DESC:TECHNICAL FIELD
The present disclosure relates generally to the field of battery technology and, more specifically, to a zinc-bromine static battery device with modified cathode current collectors for enhanced performance.
BACKGROUND
Typically, the battery technologies for energy storage devices can be differentiated on the basis of charge and discharge (round trip) efficiency, life span, and eco-friendliness of the device. Charge and discharge efficiency is one of the performance scales that can be used to assess battery efficiency. Currently, Lithium batteries have the highest charge and discharge efficiency, at about 90%, while lead storage batteries are at about 60-70%, and zinc-based batteries are at about 70-75% charge and discharge efficiency. Researchers are actively exploring alternative options that are eco-friendly and readily available in the Earth's crust. One such alternative is zinc, an abundant metal that has demonstrated promising results in Zn-based electrochemistry as a substitute for Li-based batteries. It is known that zinc-based batteries are more eco-friendly, less expensive, and comparatively less prone to overheating and catching fire than Lithium-based batteries. However, there are certain technical challenges associated with Zinc-based batteries, especially how to improve the Coulombic efficiency (e.g., charge and discharge efficiency) of the zinc-based battery (e.g., zinc-bromine static batteries).
Zn(s)+?Br?_2 (aq)?2?Br?^- (aq)+?Zn?^(2+) (aq)
It is known that zinc-bromine static batteries have the most suitable storage technology for utility applications due to their potential long life, deep discharge characteristics and potential low manufacturing cost. The zinc-bromine static batteries generally store charge through a change in the oxidation of the redox couple (Br-/Br2) at the cathode and through a change in the reduction of the redox couple (Zn/Zn2+) electrodeposition. Although the conventional zinc-bromine static batteries have emerged as promising in many aspects as compared to other types of batteries, however, one of the technical challenges with conventional zinc-bromine batteries is that their current collectors corrode during charging and discharging (i.e., specifically charge and discharging redox couple (Br-/Br2) at the cathode) leading to reduction in coulombic efficiency over a period of time. Further, for conventional zinc-based batteries (e.g., conventional zinc-bromine static batteries), it is observed that the conventional cathode current collector generally corrodes due to oxidation followed by formation of a passivation layer on it, resulting in decrease of ionic conduction and increase of electrical resistance to the flow of electrons and further reduces the operational life of the conventional zinc-bromine static batteries. Typically, the passivation layer is a thin, protective oxide layer formed typically on metals' surface due to oxygen when metals come into contact with oxygen.
Therefore, in light of the foregoing discussion, there is a need to overcome the aforementioned drawbacks associated with the conventional zinc-bromine battery device.
SUMMARY
The present disclosure provides a zinc-bromine static battery device with modified cathode current collectors. The present disclosure provides a solution to the existing technical problem of corrosion of cathode current collectors in conventional zinc-bromine static battery device and resulting issues of decrease of ionic conduction and operational life of the conventional zinc-bromine static battery device due to the corrosion and oxidation of the cathode current collector. An aim of the present disclosure is to provide a technical solution that overcomes at least partially the problems encountered in the prior art and provide an improved zinc-bromine static battery device with the modified cathode current collectors, which manifest not only improved tolerance to oxidation and corrosion but also surprisingly improve the coulombic efficiency (e.g., charge and discharge efficiency) of the zinc-bromine static battery device.
The present invention demonstrates an unexpected and non-obvious synergistic effect that goes beyond merely applying a known carbon coating to prevent corrosion. While carbon coatings on metal surfaces may be generally known, the specific combination of a titanium current collector with a precisely formulated carbon ink layer (comprising polystyrene, N-Methyl-pyrrolidine, and Super-P carbon) in the specific thickness range of 25-75 µm creates a unique tunnelling electron transfer effect in zinc-bromine battery environments that could not have been predicted through routine experimentation. As demonstrated in FIGs. 4 to6, this specific configuration not only prevents passivation but significantly enhances electrochemical performance in a manner that is decidedly non-linear with respect to thickness, with the 50 micrometres (µm) coating showing unexpectedly superior performance compared to both thinner and thicker coatings. This peak performance at a specific thickness range constitutes a surprising technical effect that would not have been obvious to one skilled in the art seeking merely to prevent corrosion.
One or more objectives of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.
In one aspect, the present disclosure provides a zinc-bromine static battery device comprising a plurality of cells. A first cell of the plurality of cells comprises a first non-conducting frame having a first side and a second side and a cavity in a middle portion, the first non-conducting frame is configured to provide a supporting structure to the first cell. A first cathode current collector attached on the first side of the first non-conducting frame. A first anode current collector is attached on the second side of the first non-conducting frame. A first cathode layer, a first separator layer, a first anode layer arranged in a sequence in the cavity of the first non-conducting frame and sandwiched between the first cathode current collector and the first anode current collector. A carbon ink layer coated on at least one side of the first cathode current collector facing the first cathode layer such that the first cathode current collector is in contact with the first cathode layer through the carbon ink layer.
The zinc-bromine static battery device of the present disclosure with the modified cathode current collectors’ manifests not only improved tolerance to oxidation and corrosion but also surprisingly improve the coulombic efficiency (e.g., charge and discharge efficiency) of the zinc-bromine static battery device.
In conventional zinc-bromine static battery devices, the conventional cathode current collector corrodes in the presence of bromine environmental and corrosive components present in an electrolyte (zinc-bromine based electrolyte). The corrosion weakens the robustness of the conventional cathode current collector, leading to reduced electrical conductivity. In an example, generally, four main technical issues are observed in conventional current collectors. In a first example, conventional current collectors easily form passivation layer due to nascent oxygen generated by an electrochemical window at cathode side reaction. In a second example, conventional current collectors also form passivation layer due to the natural surrounding atmosphere where metals in current collectors react with oxygen to attain a stable state. In a third example, conventional current collectors are found to easily decrease ionic diffusion in battery electrolyte due to the passivation layer on the current collector. In a fourth example, conventional current collectors easily increase electronic resistance due to the passivation layer on the conventional current collectors.
In contrast to the conventional zinc-bromine static battery devices, the zinc-bromine static battery device of the present disclosure, the first cathode current collector is a modified current collector in which the carbon ink layer coated on at least one side of the first cathode current collector facing the first cathode layer such that the first cathode current collector is in contact with the first cathode layer through the carbon ink layer. This modification of the current collector does not allow the formation of the passivation layer easily due to the carbon coating on the current collector while increasing ionic diffusion in the battery electrolyte due to carbon ink coating on the current collector. Further, the modification of the current collector decreases electronic resistance due to the carbon ink coating on the current collector. Alternatively stated, the carbon ink layer improves not only electrical conductivity between the first cathode current collector of the first cell of the plurality of cells and the first cathode layer of the first cell of the plurality of cells but also facilitates efficient an electron transfer during the operation of the zinc-bromine static battery device.
In an implementation, the first cathode current collector is a metallic sheet made of an inert metal.
The first cathode current collector, when implemented as the metallic sheet made of the inert metal, reduces the chances of forming passivation layer on the first cathode current collector as compared to reactive metals. Further, the inert metal-based first cathode current collector, when coated with the carbon ink, further improves tolerance to oxidation and corrosion of the first cathode current collector.
In an implementation, the first cathode current collector is a metallic sheet made of titanium.
The first cathode current collector, when implemented as the metallic sheet made of the titanium specifically, not only significantly reduces the chances of forming passivation layer on the first cathode current collector but also prevents any adverse reaction with electrolyte species over a period of time. Furthermore, the titanium current collector layer coated with carbon ink improves the operation of the zinc-bromine static battery in terms of its durability and coulombic efficiency (e.g., charge and discharge efficiency).
In an implementation, the first anode current collector is a metallic sheet made of titanium but devoid of any carbon ink layer.
In the zinc-bromine static battery device, generally, the zinc ion is deposited at the anode, whereas the bromine molecule is generated at the cathode. Thus, resources are intelligently allocated at the first cathode current collector where there is the chance of impact of bromine species, whereas, at the first anode current collector that is in contact with the first anode layer, the carbon ink layer is not applied. Thus, the zinc-bromine static battery device is cost-effective without any compromise in operational efficiency.
In an implementation, the carbon ink layer has a coating thickness ranging from 25 to 75 micrometers (µm).
Based on experimentation, it is observed that the coating thickness of the carbon ink layer impacts the performance, particularly in terms of electron transfer effects. Higher than 75 micrometres of coating thickness is found to reduce tunnelling efficiency and increase electrical resistance, whereas less than 25 µm may not provide adequate coverage or conductivity, leading to inefficient electron transfer and poor electrochemical performance. Additionally, very thin layers may be more susceptible to mechanical damage or wear. The coating thickness ranging from 25 to 75 micrometer (µm) improves the tunnelling electron transfer effect. In an implementation, the coating thickness of about 50-55 µm is found to provide maximum tunnelling electron transfer effect.
In a further implementation, each of the first cathode current collector and the anode current collector is a metallic sheet of thickness 0.3-0.4 millimetres (mm).
The specified thickness range of 0.3-0.4 mm of each of the first cathode current collector and the anode current collector provides mechanical strength for maintaining structural integrity. Moreover, such structural integrity of the first cathode current collector makes it possible to apply the carbon ink coating with uniform thickness, enabling a consistent and an efficient flow of electrons between the electrodes (i.e., cathode layer and anode layer) and the external circuit during both the charging and discharging phases of the zinc-bromine static battery device.
In further implementation, the first non-conducting frame comprises at least one electrolyte filing slot to fill the electrolyte in the cavity of the first non-conducting frame.
The electrolyte filling slots in the first non-conducting frame of the first cell of the plurality of cells provide a narrow passage for pouring the electrolyte in the cavity of the first non-conducting frame of the first cell of the plurality of cells, which reduces wastage of the electrolyte due to leakage or due to overflow and provides a convenient medium for the transfer of the electrolyte into the zinc-bromine static battery device.
In further implementation, when the zinc-bromine static battery device is in operation, a flow of electrons is effectuated from the cathode layer to the anode layer during charging cycle of the zinc-bromine static battery device and from the anode layer to cathode layer during discharging cycle of the zinc-bromine static battery device while an oxidation of the cathode current collector is desisted by a combination of the carbon ink layer and the first cathode current collector.
The combination of the carbon ink layer and the first cathode current collector of the first cell of the plurality of cells prevents the formation of the passivation layer on the first cathode current collector. The carbon ink layer on the titanium sheet (forming the first cathode current collector) not only acts as a barrier, making it difficult for the passivation layer to form on the surface of the cathode current collector but also enhances ionic diffusion by providing pathways for ions to move more freely through the electrode (the cathode layer and the anode layer). Carbon is conductive and porous, allowing ions to navigate through the coating with lower resistance. The enhanced ionic diffusion facilitated by the carbon coating improves the interaction between the electrodes (the cathode layer and the anode layer) and the electrolyte, promoting efficient ion transport and, consequently, better electrochemical performance.
In further implementation, the carbon ink layer comprises a combination of polystyrene (PS), N-Methyl-pyrrolidine (NMP), and Super-P carbon (SPC).
The combination of PS, NMP, and SPC provides a synergistic effect, optimizing the electrical conductivity, adhesion, processability, and cost-effectiveness of the carbon ink layer. This ultimately leads to a more efficient and reliable zinc-bromine static battery. The combination minimizes the agglomeration of SPC particles, ensuring a homogenous ink layer for consistent conductivity and performance.
In a further implementation, a carbon ink of the carbon ink layer is prepared by mixing 70-90 wt.% of PS and 10-30wt.% of SPC to obtain a first mixture, wherein the first mixture is dissolved in NMP to obtain the carbon ink.
The ability to adjust the composition by varying the weight percentages of the PS and the SPC provides flexibility in tailoring the properties of the carbon ink layer and allows for customization based on specific performance requirements. The NMP enables the efficient dissolution of the PS and the SPC mixture, facilitating the application of a uniform and well-adhered carbon ink layer during the manufacturing process. The specific mixing ratios and the dissolution process in the NMP contribute to the formation of the carbon ink with the consistent properties. The carbon ink with the consistent properties results in a uniform coating thickness when applied to the cathode current collector, promoting uniformity in the electrochemical processes (i.e., conversion of chemical energy into electrical energy and vice versa) within the battery. The controlled formulation process helps minimize the agglomeration of the SPC particles, which can positively impact the homogeneity of the carbon ink layer. Uniform dispersion of carbon particles is useful for achieving consistent performance in terms of conductivity and electrochemical reactions.
In a further implementation, the zinc-bromine static battery device is a bipolar zinc-bromine static battery device.
The bipolar zinc-bromine static battery device configuration increases energy density, cuts internal resistance, and simplifies build. Such bipolar zinc-bromine static battery device are useful in high-power applications like grid storage systems that need high energy density and fast charge/discharge, and also in space-constrained applications.
In a further implementation, the zinc-bromine static battery device is a monopolar zinc-bromine static battery device, wherein in the monopolar zinc-bromine static battery device, the carbon ink layer is coated on both sides of the cathode current collector.
The monopolar zinc-bromine static battery configuration provides increased capacity, but comparatively higher internal resistance as compared to the bipolar zinc-bromine static battery device configuration. In this case, as the carbon ink layer is coated on both sides of the cathode current collector, the active cathode area may be doubled, boosting capacity by 50% without increasing size. The choice between bipolar and double-sided monopolar designs depends on the specific application.
It is to be appreciated that all the implementations can be combined. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1A is a diagram that depicts an exploded view of a first cell, in accordance with an embodiment of the present disclosure;
FIG. 1B is a diagram illustrating perspective view of a non-conducting frame, in accordance with an embodiment of the present disclosure;
FIG. 1C is a diagram illustrating schematic view of a non-conducting frame, in accordance with an embodiment of the present disclosure;
FIG. 1D is a diagram illustrating cross-sectional view of a first cell, in accordance with an embodiment of the present disclosure;
FIG. 1E is a diagram illustrating bare cathode current collector and modified cathode current collector, which is coated with carbon ink layer, in accordance with an embodiment of the present disclosure;
FIG. 1F is a diagram illustrating a first cell, in accordance with an embodiment of the present disclosure;
FIG. 1G is a diagram illustrating top view of bipolar zinc-bromine static battery device, in accordance with an embodiment of the present disclosure;
FIG. 1H and FIG. 1I are diagrams illustrating perspective view of the bipolar zinc-bromine static battery device, in accordance with an embodiment of the present disclosure;
FIG. 2A is a diagram illustrating top view of a monopolar zinc-bromine static battery device configuration, in accordance with present disclosure;
FIG. 2B is a diagram illustrating schematic view of a first cell of a monopolar zinc-bromine static battery device configuration, in accordance with present disclosure;
FIG. 2C is a diagram illustrating perspective view of a monopolar zinc-bromine static battery device configuration, in accordance with the present disclosure.
FIG. 2D is a diagram illustrating two-part casing of monopolar zinc-bromine static battery device configuration, in accordance with the present disclosure;
FIG. 3A is a diagram illustrating Nyquist plots for comparison of impedance data for cathode current collector when implemented as the metallic sheet made of the titanium without carbon ink layer and with carbon ink layer, in accordance with enclosure;
FIG. 3B is a diagram illustrating cyclic voltammogram of a test cell performed using a cathode current collector when implemented as the metallic sheet made of the titanium;
FIG. 3C is a diagram illustrating a cyclic voltammogram of a test cell performed using a cathode current collector when implemented as the metallic sheet made of the titanium sheet with carbon ink layer;
FIG. 4 is a diagram illustrating a cyclic voltammogram of a test cell performed using the first cathode current collector with different percentages of coating of carbon ink layer, in accordance with an embodiment of the present disclosure;
FIG. 5 is a diagram illustrating a cyclic voltammogram of a test cell performed using the cathode current collector with varied thicknesses of carbon ink layer, in accordance with an embodiment of the present disclosure; and
FIG. 6 is a diagram is a diagram illustrating a cyclic voltammogram of test cell demonstrating the comparative electrochemical performance of unmodified cathode current collector and cathode current collectors with carbon ink layer, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF EMBODIMENTS
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
FIG.1A is diagram illustrating exploded view of a first cell of zinc-bromine static battery device, in accordance an embodiment of the present disclosure. With reference to FIG.1A, there is shown a zinc-bromine static battery device 100 with a plurality of cells 102, such as a first cell 102a, a second cell 102b, a third cell 102c, up to an nth cell 102n. There is further shown an exploded view of the first cell 102a of the plurality of cells 102 of the zinc-bromine static battery device 100. The first cell 102a comprises a first non-conducting frame 104, a first cathode current collector 106, a first cathode layer 108, a first separator layer 110, a first anode layer 112, and a first anode current collector 114. The first cathode current collector 106 comprises a coating of a carbon ink layer 116 at least on one side that faces the first cathode layer 108. The first anode current collector 114 may be devoid of the coating of the carbon ink layer 116.
The zinc-bromine static battery device 100 refers to a type of rechargeable battery that uses zinc and bromine as its active materials in which the static property comes from the fact that zinc-bromine static battery device 100 does not require any pumps or moving parts to circulate the electrolyte, unlike a flow battery. The zinc-bromine static battery device 100 may also be called a zinc-bromine static battery apparatus or a zinc-bromine based energy storage system.
The plurality of cells 102 in the zinc-bromine static battery device 100 refers to the multiple individual electrochemical cells that are connected together to form the overall battery. The plurality of cells 102 are arranged in a stack within the zinc-bromine static battery device 100.
The first non-conducting frame 104 is an insulating and supporting frame that holds the first cathode current collector 106 at one side. The first non-conducting frame 104 comprises a cavity present in the middle portion of the first non-conducting frame 104. The first cathode layer 108, the first separator layer 110, and the first anode layer 112 may be arranged in the cavity. One or more electrolyte filling slots may be provided in the first non-conducting frame 104. An example of the first non-conducting frame 104, is shown and further described in detail, for example, in FIGs. 1B and 1C. In an implementation, the first non-conducting frame 104 may be square-shaped. In another implementation, the first non-conducting frame 104 may be rectangular-shaped or polygonal-shaped.
The first cathode current collector 106 is a component that collects and conducts electrons generated during the electrochemical reactions (e.g., redox couple reaction of Zn/Zn2+ or -Br- /Br2) at the first cathode layer 108. The first cathode current collector 106 is disposed in each cell of the plurality of cells 102 such that the first cathode current collector 106 is in contact with the first cathode layer 108. Advantageously, in the zinc-bromine static battery device 100, as the first cathode current collector 106 is coated with the carbon ink layer 116, the coating comes in contact with the first cathode layer 108.
The first cathode layer 108 is an electrode layer in the first cell 102a. During charging, bromide ions from the electrolyte are oxidized and form bromine molecule that is produced on the first cathode layer 108. During the formation of the bromine in the charging process, two electrons are released at the first cathode layer 108, where the two electrons travel through the external circuit 126 and are accepted by the zinc ions at the first anode layer 112, where the zinc ions after accepting the two electrons get plated at the first anode layer 112 of the first cell 102a. During the discharge process, the bromine molecule on the first cathode layer 108 accepts two electrons (received from the first anode layer 112 via the external circuit 126) and the bromine molecule is reduced, forming bromide ions. The bromide ions are then dissolved in the electrolyte.
The first anode layer 112 is another electrode layer in the first cell 102a. During charging, Zinc ions in the electrolyte flow to the first anode layer 112 and are deposited at the first anode layer 112 in a solid state (i.e., Zn is plated at the first anode layer 112). During Zn plating, two electrons released from the first cathode layer 108 travel through the external circuit 126 and are accepted by the zinc ions at the first anode layer 112. During discharge, reverse processes occur where Zn plated at the first anode layer 112 releases two electrons forming Zn ions that dissolve in the electrolyte where at the same time, the released electrons are accepted by the bromine molecule at the first cathode layer 108 to form bromide ions which in turn also dissolves in the electrolyte.
In an example, each of the first cathode layer 108 and the first anode layer 112 of the first cell 102a may be made up of carbon sheets to conduct an electric current from one electrode layer to another electrode layer. In another example, other material may be used without limiting the scope of the disclosure. For example, the anode materials may include but are not limited to, carbon-filled polymers, carbon fibre felts, metals (including zinc), alloys, conductive organic polymers, conductive metallorganic polymers, or binder-held carbon powders. Similarly, cathode materials may include carbon fibre felts, carbon-filled polymers, and binder-held carbon powders, such as activated carbon. Additionally, the thickness of each of the first cathode layer 108 may be greater than the thickness of the each of first anode layer 112. This differential thickness increases the energy density of the first cathode layer 108 and other cathode layers of other cells, allowing all the cathode layers to store more energy per unit of volume. Therefore, the thickness of a plurality of the cathode layers of the plurality of cells 102 increases the overall energy density of the zinc-bromine static battery device 100.
The first separator layer 110 separates the first cathode layer 108 and the first anode layer 112. The first separator layer 110 has submicron-sized pores, and the pores work as channels where ions move between the first cathode layer 108 and the first anode layer 112. Examples of the implementation of the first separator layer 110 may include, but are not limited to, an absorption glass metal (AGM), a polyethylene (PE) or a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer.
The first anode current collector 114 is a component that collects and conducts electrons produced during the electrochemical reactions (e.g., redox reaction of Zn-Br ions) at the first anode layer 112, enabling the efficient transfer of electrical current to an external circuit 126. Beneficially, the first anode current collector 114 is devoid of the carbon ink layer 116 coating, as the first anode layer 112 is not affected by bromine species.
The carbon ink layer 116 is coated on the first cathode current collector 106 at one side that faces the first cathode layer 108. Beneficially, the carbon ink layer 116 and the first cathode current collector 106 are morphologically similar, i.e., both are in a solid state. Thus, when the carbon ink layer 116 is coated on the first cathode current collector 106, the combination of the carbon ink layer 116 and the first cathode current collector 106 forms a solid–solid electrode, leading to a tunnelling electron transfer effect. In the tunnelling electron transfer effect, electrons are transferred from the first cathode layer 108 of the first cell 102a to the first anode layer 112 of the first cell 102a with improved flow, which in turn is found to improve the coulombic efficiency (e.g., charge and discharge efficiency) of the zinc-bromine static battery device 100.
In accordance with an embodiment, the first cathode current collector 106 and the first anode current collector 114 enclose the first cell 102a and, in effect, avoid mixing of the electrolyte among different cells, thus avoiding short-circuiting or any other discrepancy that could arise out of the mixing of electrolytes of different cells of the zinc-bromine static battery device 100.
FIG. 1B is a diagram illustrating the first non-conducting frame of FIG. 1A, in accordance with an embodiment of the present disclosure. FIG. 1B is explained in conjunction with elements from the FIG. 1A. With reference to FIG.1B, there is shown the first non-conducting frame 104. The first non-conducting frame 104 comprises a first side 104a and a second side 104b. Further, there is a cavity 118 in a middle portion 120 of the first non-conducting frame 104. The first non-conducting frame 104 may further comprise at least one electrolyte filing slot 122. Aqueous electrolyte filled into the first cell 102a via the at least one electrolyte filing slot 122. Like the first cell 102a, the electrolyte may be filled in the plurality of cells 102 via the corresponding electrolyte filling slot. The cavity 118 provides a space for accommodating various components of the first cell 102a.
FIG. 1C is a diagram illustrating a front view of the first non-conducting frame of FIG. 1B, in accordance with the present disclosure. FIG. 1C is explained in conjunction with elements from the FIGs. 1A and 1B. With reference to FIG. 1C, there is shown the first non-conducting frame 104. In accordance with an embodiment, the first non-conducting frame 104 comprises at least one electrolyte filing slot 122 to fill electrolyte in the cavity 118 of the first non-conducting frame 104. The at least one electrolyte filling slots facilitate the introduction of the electrolyte into the first cell 102a.
FIG. 1D is a diagram illustrating a cross-sectional view of a cell of a zinc-bromine static battery, in accordance with the present disclosure. FIG. 1D is explained in conjunction with elements from the FIGs. 1A, 1B, and 1C. With reference to FIG. 1D, there is shown a cross-sectional view of the first cell 102a.
The first cell 102a comprises the first non-conducting frame 104, having the first side 104a and the second side 104b and the cavity 118 in the middle portion 120. The shape of the cavity 118 is complementary to the shape and size of the first cathode layer 108, the first separator layer 110, and the first anode layer 112 so as to be accommodated within the cavity 118, thereby contributing to the compact form factor of the zinc-bromine static battery device 100. Furthermore, the first non-conducting frame 104 is configured to provide a supporting structure to the first cell 102a. The first cathode current collector 106 is attached on the first side 104a of the first non-conducting frame 104, and the first anode current collector 114 is attached on the second side 104b of the first non-conducting frame 104. The first cathode layer 108, the first separator layer 110, and the first anode layer 112 are arranged in a sequence in the cavity 118 of the first non-conducting frame 104 and sandwiched between the first cathode current collector 106 and the first anode current collector 114. Such arrangement not only provides mechanical strength to the cell structure of the first cell 102a but also makes the first cell 102a very compact, thereby allowing it to store more energy in the same volume as compared to conventional systems.
The carbon ink layer 116 is coated on at least one side of the first cathode current collector 106 facing the first cathode layer 108 such that the first cathode current collector 106 is in contact with the first cathode layer 108 through the carbon ink layer 116. The first cathode current collector 106 is a modified current collector, where the modification of the first cathode current collector 106 does not allow the formation of the passivation layer easily due to the carbon ink layer 116 on the first cathode current collector 106 while increasing ionic diffusion in battery electrolyte due to carbon ink coating on the first cathode current collector 106. Further, the modification of the first cathode current collector 106 decreases electronic resistance due to the carbon ink coating on the first cathode current collector 106. The carbon ink layer 116 and the first cathode current collector 106 are morphologically similar, i.e., both are in a solid state. Thus, when the carbon ink layer 116 is coated on the first cathode current collector 106, the combination of the carbon ink layer 116 and the first cathode current collector 106 forms a solid–solid electrode, leading to a tunnelling electron transfer effect. In the tunnelling electron transfer effect, electrons are transferred from the first cathode layer 108 of the first cell 102a to the first cathode current collector 106 of the first cell 102a with improved flow, which in turn is found to improve the coulombic efficiency (e.g., charge and discharge efficiency). The tunnelling may be defined as a quantum mechanical effect in which tunnelling current occurs when the electrons move through a barrier that the electrons classically shouldn’t be able to move through. In classical terms, if body doesn’t have enough energy to move over a potential energy barrier, then body will not be able to cross the potential energy barrier. However, in. the quantum mechanical world, the electrons have both wave-like and particle-like properties. The tunnelling is an effect of the wavelike nature. The waves do not end abruptly at a wall or potential energy barrier but taper off quickly. If the potential energy barrier is thin enough, the probability function may extend into the next region through the barrier. The tunnelling electron transfer effect refers to the phenomenon where electrons move through the potential energy barrier (tunnel) due to quantum mechanical effects.
The tunnelling electron transfer effect observed in the zinc-bromine static battery device with modified cathode current collectors can be explained by quantum mechanical principles. When the carbon ink layer is coated on the titanium current collector at the optimized thickness (25-75 µm), it creates a unique interface structure where electrons can move through the potential barrier between the cathode layer and current collector via quantum tunnelling rather than classical conduction. In the zinc-bromine battery context, this is particularly significant because the redox reaction of Br?/Br2 at the cathode requires efficient electron transfer to maintain high coulombic efficiency. The carbon ink layer's specific composition and morphology creates a nanoscale electronic structure that facilitates this tunnelling effect. As demonstrated in our experimental results, particularly in FiGs.5 and 6, this effect is heavily dependent on the thickness of the carbon layer, with optimal tunnelling occurring in the 45-55 µm range. At this optimal thickness, the potential barrier is thin enough to allow significant tunnelling probability while maintaining sufficient barrier properties to prevent the formation of a passivation layer on the titanium surface. This represents a novel approach and significant improvement in zinc-bromine battery design, as it directly addresses the fundamental electrochemical limitations of conventional devices or systems. The specific properties of the carbon ink layer that enable this tunnelling phenomenon can be further explained by examining its microstructure. The combination of polystyrene (PS) and Super-P carbon (SPC) creates a nanocomposite material with distinct electrical properties. The PS matrix provides mechanical stability while the SPC particles form a percolating network of conductive pathways with nanoscale separation distances. Electron microscopy analysis reveals that at the optimized thickness and composition (particularly 70-80 wt.% PS and 20-30 wt.% SPC), the carbon particles maintain an average separation distance of approximately 2-5 nanometres. The separation is beneficial because it falls within the quantum tunnelling range for electrons in this electrochemical environment. Electrochemical impedance spectroscopy measurements confirm this effect, showing a characteristic decrease in charge transfer resistance from greater than 200 ohms for uncoated titanium to less than 50 ohms for the optimized carbon ink coating, without a corresponding increase in bulk resistance that would be expected from classical conduction mechanisms. This distinctive electrical behaviour, coupled with the carbon ink's ability to prevent direct contact between the titanium substrate and the bromine species, creates an ideal environment for efficient electron transfer while simultaneously protecting the current collector from passivation.
For instance, when the carbon ink layer 116 is coated on the first cathode current collector 106 of the first cell 102a of the plurality of cells 102, the transfer of electrons from the first cathode layer 108 to the first cathode current collector 106 occurs due to a tunnelling effect exhibited by the electrons. Further, the carbon ink layer 116 serves as a medium to establish and maintain direct contact between the first cathode current collector 106 and the first cathode layer 108, which enhances adhesion, ensuring a robust and consistent connection. By promoting better contact, the carbon ink layer 116 helps reduce internal resistance within the zinc-bromine static battery device 100. Further, the close contact facilitated by the carbon ink layer 116 enhances the electrochemical reactions at the interface between the first cathode current collector 106 and the first cathode layer 108. Furthermore, the efficient connection between the first cathode current collector 106 and the first cathode layer 108 contribute to increased energy density in the zinc-bromine static battery device 100 and as a result the zinc-bromine static battery device 100 can store more energy for a given size or weight. Furthermore, the combination of the carbon ink layer 116 coated on the titanium sheet based current collector helps in achieving a uniform current distribution across the first cathode current collector 106, which is useful for preventing localized issues such as hotspots (i.e. localized areas within a battery where heat is generated at a higher rate than in the surrounding regions) and uneven wear.
In accordance with an embodiment, the first cathode current collector 106 is a metallic sheet made of an inert metal. Specifically, and advantageously, the first cathode current collector 106 is a metallic sheet made of titanium. The first cathode current collector 106, when implemented as the metallic sheet made of the titanium specifically, not only significantly reduces the chances of forming passivation layer on the first cathode current collector 106 but also prevents any adverse reaction with electrolyte species over a period of time. Furthermore, the first cathode current collector 106 coated with carbon ink improves the operation of the zinc-bromine static battery device 100 in terms of its durability and coulombic efficiency (e.g., charge and discharge efficiency). The titanium is often referred to as an inert metal due to its excellent resistance to corrosion as compared to aluminium (Al), copper (C), nickel (Ni), etc. Al easily reacts with halogens and forms metal halides for example, when Al reacts with bromine at the cathode layer, it easily converts into Aluminium Bromide, but the titanium does not react easily with halogens being an inert metal. Further, the carbon ink layer 116 is coated on the first cathode current collector 106 by a dip coating technique to increase ionic conduction and, decrease the electronic resistance and further avoid any oxidation process on the first cathode current collector 106.
In accordance with an embodiment, the dip coating technique is a process used to apply a thin layer of coating or finish to a substrate, such as the titanium sheet in this case. This technique involves immersing the titanium sheet into a liquid coating material, allowing the titanium sheet to be evenly coated. In an implementation, only one side of the titanium sheet may be coated and in such a case, the dip coating is applied such that only one side is coated. Other than dip coating, other coating techniques may be used without limiting the scope of the disclosure, for example, slot die coating.
FIG. 1E is a diagram illustrating a coating of carbon ink layer on a cathode current collector, in accordance with an embodiment of the present disclosure. FIG. 1E is explained in conjunction with elements from FIGs. 1A to 1D. With reference to FIG.1E, there is shown the carbon ink layer 116 coating applied on the first cathode current collector 106 made of titanium sheet. The carbon ink layer 116 has a coating thickness ranging from 25 to 75 micrometers. Carbon is more stable than any other non-metal in bromine environment. The carbon increases the reversibility and current density (current density is the amount of charge per unit time that flows through a unit area of a chosen cross-section).
TABLE 1
S. No Coating Thickness of Carbon Ink Layer (micrometres) Tunnelling Efficiency
1. 100 Low
2. 90 Low
3. 80 Low
4. 75 Medium
5. 70 High
6. 65 High
7. 60 High
8. 55 Very High
9. 50 Very High
10. 45 Very High
11. 40 High
12. 35 High
13. 30 High
14. 25 Medium
15. 20 Low

As shown in the table 1, the specific thickness range of carbon ink layer affects the tunnelling efficiency of the cathode current collector coated with carbon ink layer. Too thin carbon ink layer might not provide sufficient conductivity, leading to lower tunnelling efficiency. Conversely, an excessively thick layer might impede electron transfer, again affecting tunnelling efficiency (for e.g., 100 µm and 90 µm), further explained in FIG. 6. Tunnelling efficiency is very high when carbon ink layer coating is in the range of forty-five µm to 55 µm and still high/medium in the range of 25 to 75 Micrometer (µm), as given above.
The carbon ink layer 116 improves not only electrical conductivity between the first cathode current collector 106 of the first cell 102a of the plurality of cells 102 and the first cathode layer 108 but also facilitates efficient electron transfer during the operation of the zinc-bromine static battery device 100. In the tunnelling electron transfer effect, electrons are transferred from the first cathode layer 108 of the first cell 102a to the first cathode current collector 106 with improved flow, which in turn is found to improve the coulombic efficiency (e.g., charge and discharge efficiency) of the zinc-bromine static battery device 100.
In accordance with an embodiment, the carbon ink layer 116 comprises a combination of polystyrene, N-Methyl-pyrrolidine, and Super-P carbon. The combination of PS, NMP, and SPC provides a synergistic effect, optimizing the electrical conductivity, adhesion, processability, and cost-effectiveness of the carbon ink layer. This ultimately leads to a more efficient and reliable zinc-bromine static battery. The combination minimizes the agglomeration of SPC particles, ensuring a homogenous ink layer for consistent conductivity and performance.
In an implementation, the carbon ink of the carbon ink layer 116 is prepared by mixing 70-90wt.% of polystyrene (PS) and 10-30wt.% of Super-P carbon (SPC) to obtain a first mixture, where the first mixture is dissolved in N-Methyl-pyrrolidine (NMP) to obtain the carbon ink. The ability to adjust the composition by varying the weight percentages of the PS and the SPC provides flexibility in tailoring the properties of the carbon ink layer and allows for customization based on specific performance requirements. The NMP enables the efficient dissolution of the PS and the SPC mixture, facilitating the application of a uniform and well-adhered carbon ink layer during the manufacturing process. The specific mixing ratios and the dissolution process in the NMP contribute to the formation of the carbon ink with the consistent properties. The carbon ink with the consistent properties results in the uniform coating thickness when applied to the cathode current collector, promoting uniformity in the electrochemical processes (i.e., conversion of chemical energy into electrical energy and vice versa) within the battery. The controlled formulation process helps minimize the agglomeration of the SPC particles, which can positively impact the homogeneity of the carbon ink layer. Uniform dispersion of carbon particles is useful for achieving consistent performance in terms of conductivity and electrochemical reactions.
FIG. 1F is a diagram illustrating an arrangement of different components in a first cell, in accordance with an embodiment of the present disclosure. FIG. 1F is explained in conjunction with elements from FIGs. 1A to 1F. With reference to FIG. 1F, there is shown the first cell 102a. In the first cell 102a, the first anode current collector 114 is in contact with the first anode layer 112. The first separator layer 110 is in between the first anode layer 112 and the first cathode layer 108. The first cathode current collector 106, coated with the carbon ink layer 116, is in contact with the first cathode layer 108. There is further shown an external circuit 126 connected to the first cathode current collector 106 and the first anode current collector 114.
In accordance with an embodiment, a thickness of each cathode layer is greater than each anode layer in the plurality of cells 102, such as the first cell 102a. The first separator layer 110 may be one of: an absorption glass metal (AGM), a polyethylene (PE) or a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer. Although AGM, PE, and sulfonated tetrafluoroethylene-based fluoropolymer-copolymer can be used, during experimentation, it was observed that for the zinc-bromine static battery device 100, the first separator layer 110, when implemented using the AGM, the energy efficiency of the zinc-bromine static battery device 100 was found to be highest as compared to other separator materials, as shown in Table 2 below.
Table 2
Separators Charging capacity (mAh) Discharging capacity (mAh) Voltaic Efficiency Energy Efficiency Coulombic Efficiency
AGM 25 20.58 93.03 76.63 82.34
Sulfonated tetrafluoroethylene-based fluoropolymer-copolymer
5.76 4.34 78.05 58.78 75.31
Polyethylene 25 20.11 91.19 73.32 80.43

The charging capacity of the zinc-bromine static battery device 100 refers to the amount of the electrical energy that can be stored in the zinc-bromine static battery device 100 during the charging process. For example, if a battery has a charging capacity of 2000mAh, it means that it can theoretically store 2000 milliampere-hours of electrical energy when fully charged. The charging capacity is a useful specification as it determines how long a battery-powered device can operate before needing to be recharged. The discharging capacity of the zinc-bromine static battery device 100 refers to the amount of electrical energy that the zinc-bromine static battery device can deliver to the load when in use. For example, if the zinc-bromine static battery device has a discharging capacity of 2000mAh, it means that the zinc-bromine static battery device can provide a continuous current of 2000 milliampere-hours to power a device before it needs to be recharged. The Voltaic efficiency is a way to measure the efficiency of the zinc-bromine static battery device 100. Voltaic efficiency represents the ratio of the average discharge voltage to the average charge voltage. The energy efficiency is a measure for the amount of energy that can be taken from the zinc-bromine static battery device compared to the amount of energy that was charged into the battery beforehand. As inferred from Table 2, the AGM separator is useful and more efficient when used as separator as compared to sulfonated tetrafluoroethylene based fluoropolymer-copolymer and Polyethylene separators as AGM separator has comparatively better charging capacity, discharging capacity, voltaic efficiency and energy efficiency.
FIG. 1G is a diagram illustrating a top view of a zinc-bromine static battery device, in accordance with an embodiment of the present disclosure. FIG. 1G is explained in conjunction with elements from FIGs. 1A to 1F. With reference to FIG. 1G, there is shown a top view of the zinc-bromine static battery device 100. There is further shown the plurality of cells 102, the at least one electrolyte filling slot 122, and additionally a plurality of fixing means 128 (e.g., screw-bolt based fixing means), a first base plate 130 and a second base plate 132 in the zinc-bromine static battery device 100.
In this embodiment, the zinc-bromine static battery device 100 is a bipolar zinc-bromine static battery device. The bipolar zinc-bromine static battery device configuration increases energy density, cuts internal resistance, and simplifies build. Such bipolar zinc-bromine static battery device is useful in high-power applications like grid storage systems that need high energy density and fast charge/discharge, and also in space-constrained applications. Further, the first base plate 130 and the second base plate 132 are non-conducting plates that are arranged at end portions of the zinc-bromine static battery device 100. Furthermore, the first base plate 130 and the second base plate 132 provide support as well as protection to the zinc-bromine static battery device 100 from any external impact.
In an implementation, during the assembly of the zinc-bromine static battery device 100, the first base plate 130, the plurality of cells 102, and the second base plate 132 are compressed together. In an implementation, the plurality of fixing means 128 are inserted through peripheral portions of each of the first base plate 130 and the second base plate 132. In another implementation, the plurality of fixing means 128 (e.g., in the form of metallic rods) are inserted through the plurality of perforations 124 (of FIGs. 1B and 1C) of the first non-conducting frame 104. The number of the plurality of cells 102 is determined based on the required output voltage. In an example, each cell layer in the plurality of cells 102 generates a voltage of 2V. Therefore, adding 30 cells in the zinc-bromine static battery device 100 gives a total voltage of 60V. However, different numbers of voltages as per need may be generated without affecting the scope of the disclosure.
FIG. 1H and FIG. 1I are diagrams illustrating different perspectives views of a zinc-bromine static battery device, in accordance with an embodiment of the present disclosure. FIG. 1H is explained in conjunction with elements from FIGs. 1A to 1G. With reference to FIG. 1H, there is shown a first side 134 of the zinc-bromine static battery device 100 with the first base plate 130 attached on the first side 134 of the zinc-bromine static battery device 100. FIG. 1I is explained in conjunction with elements from FIGs. 1A to 1H. With reference to FIG. 1I, there is further shown a second side 136 of the zinc-bromine static battery device 100, where the second base plate 132 is attached on the second side 136 of the zinc-bromine static battery device 100. There is further shown the plurality of fixing means 128 and the at least one electrolyte filing slot 122.
FIG. 2A is a diagram illustrating a top view of a zinc-bromine static battery in a monopolar zinc-bromine static battery configuration, in accordance with an embodiment of the present disclosure. FIG. 2A is explained in conjunction with elements from FIGs. 1A to 1I. With reference to FIG. 2A, there is shown a monopolar zinc-bromine static battery device configuration 200. The monopolar zinc-bromine static battery device configuration 200 comprises a plurality of cells 202 and electrolyte filling slots 204.
In this embodiment, in the monopolar zinc-bromine static battery device configuration, the carbon ink is coated on both sides of the cathode current collector. The monopolar zinc-bromine static battery device configuration 200 provides increased capacity, but comparatively higher internal resistance as compared to the bipolar zinc-bromine static battery device configuration. In this case, as the carbon ink layer is coated on both sides of the cathode current collector 210, the active cathode area may be doubled, boosting capacity by 50% without increasing size. The placement of the one or more liquid electrolyte filling slots makes the electrolyte re-filling in the monopolar zinc-bromine static battery device configuration 200 simple with improved ease-of-use.
FIG. 2B is a diagram illustrating an arrangement of different layers in a first cell of a monopolar zinc-bromine static battery device configuration, in accordance with an embodiment of the present disclosure. FIG. 2B is explained in conjunction with elements from FIGs. 1A to 2A. With reference to FIG. 2B, there is shown a first cell 202a of the monopolar zinc-bromine static battery device configuration 200. A sequence of arrangement of different layers in the first cell 202a of the monopolar zinc-bromine static battery device configuration 200 is as follows: a first cathode layer 206, a first carbon link layer 208A, a cathode current collector 210, a second carbon link layer 208B, a second cathode layer 212, a separator layer 214, a first anode layer 216, an anode current collector 218, and a second anode layer 220.
In this configuration, i.e., the monopolar zinc-bromine static battery device configuration 200, the cathode current collector 210 is coated with the carbon ink on both sides, i.e., the first carbon link layer 208A and the second carbon link layer 208B. The cathode current collector 210 is sandwiched between the first cathode layer 206 and the second cathode layer 212. As the cathode current collector 210 is coated with carbon ink layers on both sides, the formation of passivation layers on the cathode current collector 210 decreases, which in turn desists oxidation of the cathode current collector 210. The separator layer 214 is sandwiched between the second cathode layer 212 and the first anode layer 216. The anode current collector 218 is devoid of any coatings of carbon ink.
FIG. 2C is a diagram illustrating the perspective view of a monopolar zinc-bromine static battery device, in accordance with the present disclosure. FIG. 2C is explained in conjunction with elements from FIGs. 1A to 2B. With reference to FIG. 2C, there is shown the monopolar zinc-bromine static battery device configuration 200, which includes electrolyte filling slots 204 and two-part casing, such as a first part 222A and a second part 222B, which are joined to form the two-part casing, where the joining simplifies compression of the plurality of cells 202 in the monopolar zinc-bromine static battery device configuration 200. The compression makes the different layers come in contact with each other for their proper functioning.
FIG. 2D is a diagram illustrating a two-part casing of monopolar zinc-bromine static battery device configuration, in accordance with the present disclosure. FIG. 2D is explained in conjunction with elements from FIGs. 1A to 2C. With reference to FIG. 2D, there is shown a two-part casing, such as the first part 222A and the second part 222B, of the monopolar zinc-bromine static battery device configuration 200 along with the plurality of cells 202. In an implementation, the two-part casing is made up of HDPE polymer that improves the overall battery chemistry of the monopolar zinc-bromine static battery device configuration 200, as the HDPE polymer does not react with the electrolyte (i.e., a zinc-bromine electrolyte) that is filled in the monopolar zinc-bromine static battery device. Notwithstanding, the disclosure may not be so limited, and the two-part casing may be made if other suitable materials without limiting the scope of the disclosure.
EXPERIMENTAL PART:
Materials Used:
Polystyrene and 2-Methyl-pyrrolidine were obtained in the form of a liquid, while the Super P carbon was obtained in powdery form and were directly used as raw material for preparing carbon ink. Further inert titanium sheet used as the first cathode current collector substrate was obtained in solid form.
EXAMPLES OF PREPARATION
Example 1: Method of preparation of a first cathode current collector 106 with carbon ink layer coating.
Formation of carbon ink using the polystyrene, 2-Methyl-pyrrolidine and Super P carbon.
70% by wt. of the polystyrene was dissolved into the 2-Methyl-pyrrolidine at room temperature by constantly stirring the magnet to form a homogeneous solution.
30 wt.% Super P carbon was added to the homogeneous solution to get uniform dispersion of the carbon ink.
Coating the first cathode current collector substrate, i.e. inert titanium metal sheet with carbon ink.
The first cathode current collector substrate, composed of an inert titanium metal sheet, underwent a cleaning process using isopropanol. The cleaned current collector substrate, i.e. inert titanium metal sheet, was immersed in a solution containing carbon ink. Further, the coating process was carried out using the dip coating technique.
Preparation of the first cathode current collector with carbon ink layer coating
Following the coating procedure, the coated first cathode current collector substrate, i.e., inert titanium sheet, was removed and placed into a hot air oven set at a maintained temperature of 50 degrees Celsius for a few hours in order to facilitate the drying and curing of the coating. Finally, the first cathode current collector 106 with the carbon ink layer 116 coating of thickness of approximately 350 micrometres (µm) was obtained.
Example 2: Verification of carbon ink compositions across various different compositional ratios:
To validate the effectiveness of the carbon ink layer across across different compositional ratios, additional cathode current collectors were prepared following the method described in Example 1, but varying the composition as follows: 1) Sample A: 75 wt.% polystyrene and 25 wt.% Super-P carbon; 2) Sample B: 80 wt.% polystyrene and 20 wt.% Super-P carbon; 3) Sample C: 85 wt.% polystyrene and 15 wt.% Super-P carbon; and 4) Sample D: 90 wt.% polystyrene and 10 wt.% Super-P carbon.
All samples were applied to titanium sheets with a consistent coating thickness of 50 micrometers. Cyclic voltammetry testing as described in the experimental section showed that all compositions within the range of 70-90 wt.% polystyrene and 10-30 wt.% Super-P carbon exhibited the characteristic redox peaks with current responses at least three times greater than uncoated titanium, confirming the efficacy across this compositional range. While the optimal performance was observed in the range of 70-80 wt.% polystyrene, all tested compositions demonstrated substantial improvement over uncoated titanium current collectors.
RESULTS:
FIG. 3A is a diagram illustrating Nyquist plots for comparison of impedance data for cathode current collector when implemented as a metallic sheet made of titanium with and without carbon ink layer, in accordance with an embodiment of the present disclosure. FIG. 3A is explained in conjunction with elements from FIGs. 1A to 2D. With reference to FIG. 3A, there is shown Nyquist plots where the X-axis represents real impedance, and the Y-axis represents a corresponding imaginary impedance. In electrochemical impedance spectroscopy (EIS), Nyquist plots are used to represent the impedance of an electrochemical system.
In this case, the Nyquist plot, the real component of impedance (usually resistance) is plotted on the horizontal axis (X-axis), and the imaginary component (usually reactance) is plotted on the vertical axis (Y-axis). The graphical representation 300A depicts the comparison of the first cathode current collector 106 when implemented as the metallic sheet made of the titanium without the carbon ink layer 116 and with the carbon ink layer 116. A graphical line 302A indicates impedance values for the first cathode current collector 106 without the carbon ink layer 116. A graphical line 304A indicates impedance values for the first cathode current collector 106 with the carbon ink layer 116. It is evident that the first cathode current collector 106 coated with the carbon ink layer 116 exhibits less impedance as compared to the bare cathode current collector. Lower impedance increases the electrical conductivity of the cathode current collector, thereby increasing the operating efficiency of the zinc-bromine static battery device 100 (of FIG. 1A).
FIG. 3B is a diagram illustrating a cyclic voltammogram of a test cell performed using the first cathode current collector when implemented as the metallic sheet made of the titanium without carbon ink layer. FIG. 3B is explained in conjunction with elements from FIGs. 1A to 3A. With reference to FIG. 3B there is shown a cyclic voltammogram 300B of a test cell (e.g., the first cell 102a) obtained at different scan rate of volt per second (V/s) performed using the first cathode current collector 106 when implemented as the metallic sheet made of the titanium without the carbon ink layer 116. X-axis represents varying voltage in volts with voltage of Standard Calomel Electrode. The Y-axis represents the current in milli ampere(mA). The cyclic voltammogram 300B includes a curve 302B obtained at 10 millivolts, a curve 304B obtained at 20 millivolts, a curve 306B obtained at 30 millivolts, a curve 308B obtained at 40 millivolts and a curve 310B obtained at 50 millivolts.
FIG.3C is a diagram illustrating a cyclic voltammogram of a test cell performed using a first cathode current collector when implemented as the metallic sheet made of the titanium coated with carbon ink layer. FIG. 3C is explained in conjunction with elements from FIGs. 1A to 3B. With reference to FIG. 3C, there is shown a cyclic voltammogram 300C of a test cell (e.g., the first cell 102a) obtained at different scan rate of mV/s performed using the first cathode current collector 106 when implemented as the metallic sheet made of the titanium with the carbon ink layer 116. X-axis represents varying voltage in millivolts with voltage of Standard Calomel Electrode. Y-axes represent the current in milli ampere(mA).
With reference to both FIGs. 3C and 3B, there is shown a cyclic voltammogram 300B and a cyclic voltammogram 300C. The cyclic voltammogram 300B for titanium sheet implemented as cathode current collector without a carbon ink layer shows an indistinguishable oxidation and reduction peak potential for the redox couple Br-/Br2, with a significantly lower peak current. In the cyclic voltammogram 300C for titanium sheet implemented as cathode current collector with a carbon ink layer obtained at a different. The cyclic voltammogram 300C includes a curve 302C obtained at 10 millivolts, a curve 304C obtained at 20 milli volts , a curve 306C obtained at 30 millivolts, a curve 308C obtained at 40 millivolts and a curve 310C obtained 50 millivolts.
In case of the cyclic voltammogram 300C distinct reduction peak potential is visible around 0.2 V, along with an oxidation peak potential at 1.2 V, clearly indicating an easily achievable electron transfer for the redox couple Br-/Br2. The peak current is high. The carbon ink layer 116 is likely more conductive than the bare titanium, which can improve the transport of electrons within the cathode layer and lead to higher current densities.
FIG. 4 is a diagram illustrating a cyclic voltammogram of a test cell performed using the first cathode current collector with different percentages of coating of carbon ink layer, in accordance with an embodiment of the present disclosure. FIG. 4 is explained in conjunction with elements from FIGs. 1A to 3C. With reference to FIG. 4, there is shown a cyclic voltammogram 400. The cyclic voltammogram 400 depicts electrochemical behaviour of the test cell (for example, the first cell 102a) performed using the first cathode current collector 106 when implemented as the metallic sheet with the carbon ink layer 116. The cyclic voltammogram 400 has a plurality of curves depicting different composition of the carbon ink layer 116 on the first cathode current collector 106 when implemented as the metallic sheet (hereinafter referred to as titanium sheet). X-axis represents varying voltage in volts with voltage of Standard Calomel Electrode. Y-axes represent the current in milli ampere (mA).
The cyclic voltammogram 400 includes a curve 402, a curve 404, a curve 406, a curve 408 and a curve 410. The curve 402 represents the first cathode current collector 106 made of bare titanium sheet. The curve 404 represents the first cathode current collector 106 made of titanium sheet (with titanium sheet having the passivation layer). The curve 406 represents the first cathode current collector 106 made of titanium sheet with a coating of 10% of the carbon ink layer 116. The curve 408 represents the first cathode current collector 106, made of titanium sheet with a coating of 20% of the carbon ink layer 116. The curve 410 represents the first cathode current collector 106 made of titanium sheet with a coating of 30% of the carbon ink layer 116.
The curve 402 shows minimal electrochemical activity across the potential range, with a very slight increase in current at higher potentials. The curve 402 has a relatively flat profile as compared to other curves of the plurality of curves. The curve 402 indicates poor electron transfer kinetics and limited redox activity, which substantiates that an unmodified titanium sheet has a limited utility as the first cathode current collector 106 in zinc-bromine battery due to its tendency to form a passivation layer.
The curve 404 shows the lowest electrochemical activity among all the curves of the plurality of curves, appearing almost as a flat line with negligible current response throughout the potential range. The profile of the curve 404 illustrates how the naturally formed passivation layer severely hinders electron transfer and ionic conductivity, effectively rendering the current collector (i.e., the first cathode current collector 106) electrochemically inactive and unsuitable for battery applications. The curve 406 depicts electrochemical activity with discernible redox peaks. The reduction peak of around 0.2 V and oxidation peak of around 1.3 V demonstrates that even a relatively low percentage of the coating of the carbon ink layer 116 significantly improves the electrochemical performance by providing conductive pathways that bypass the passivation issues of unmodified titanium sheet.
The curve 408 exhibits substantially enhanced electrochemical activity compared to lower carbon content samples (i.e., depicted by the curve 402, the curve 404 and the curve 406). The more pronounced reduction peak at approximately 0.2 V and oxidation peak around 1.3 V indicate improved reaction kinetics and greater electrochemical accessibility. The increased peak current amplitudes suggest better conductivity and more efficient electron transfer processes. The curve 410 features the highest current response among the plurality of curves, with sharp, well-defined reduction and oxidation peaks. The peak current reaches nearly 6mA, approximately ten times greater than that depicted by the curve 402. The dramatic improvement confirms that the coating of 30% of the carbon ink layer 116 effectively addresses the passivation layer issues, substantially enhances ionic diffusion, and significantly reduces electronic resistance.
FIG. 5 is a diagram illustrating a cyclic voltammogram of a test cell performed using the cathode current collector with varied thicknesses of carbon ink layer, in accordance with an embodiment of the present disclosure. FIG. 5 is explained in conjunction with elements from FIGs. 1A to 4. With reference to FIG. 5, there is shown a cyclic voltammogram 500. The cyclic voltammogram 500 depicts the electrochemical behaviour of the test cell (for example, the first cell 102a) performed using the cathode current collector (for example, the first cathode current collector 106) when implemented as the metallic sheet with the carbon ink layer 116. The cyclic voltammogram 500 has a plurality of curves depicting the behaviour of the first cathode current collector 106 when implemented as the titanium sheet and the titanium sheet being coated with different thicknesses of the carbon ink layer 116. X-axis represents varying voltage in volts with the voltage of Standard Calomel Electrode. Y-axis represents the current in milli ampere (mA).
The cyclic voltammogram 500 includes a curve 502, a curve 504, a curve 506, a curve 508 and a curve 510. The curve 502 represents the first cathode current collector 106 made of the titanium sheet (with titanium sheet coated with 10 micrometre of the carbon ink layer 116). The curve 504 represents the first cathode current collector 106 made of the titanium sheet (with the titanium sheet coated with 30 micrometre of the carbon ink layer 116). The curve 506 represents the first cathode current collector 106 made of the titanium sheet (with titanium sheet coated with 50 micrometres of the carbon ink layer 116). The curve 508 represents the first cathode current collector 106 made of the titanium sheet (with the titanium sheet coated with 70 micrometres of the carbon ink layer 116). The curve 510 represents the first cathode current collector 106 made of titanium sheet (with the titanium sheet coated with 100 micrometres of the carbon ink layer 116).
The curve 506 demonstrates superior electrochemical activity compared to other curves, exhibiting the most pronounced reduction peak at approximately 0.3 volts and oxidation peak at around 1.2 V. The cathode current collector with 50 micrometres coating achieves the highest current response in both reduction (approximately “-4 mA”) and oxidation (approximately “4.5 mA”) regions, indicating optimal electron transfer kinetics and ionic conductivity. The exceptional performance of the 50 micrometres coating of the carbon ink layer 116 represents a coating thickness that maximizes electrochemical performance while using minimal material.
The curve 502 shows well-defined redox peaks, suggesting that even relatively thin carbon coatings may substantially improve the electrochemical properties of the first cathode current collector 106. Meanwhile, the curve 508 (corresponding to the 70 micrometres coating of the carbon ink layer 116) and the curve 510 (corresponding to 100 micrometres coating of the carbon ink layer 116) demonstrate diminished performance, with lower current responses despite using more carbon material. The lower current at a higher thickness of the carbon ink layer 116 indicates that excessive coating thickness may introduce electronic resistance or mass transport limitations. The curve 502 (i.e., 10 micrometres of coating of the carbon ink layer 116) shows the weakest performance among all the thicknesses, though still dramatically improved compared to bare titanium sheet (as shown in FIG. 4).
The cyclic voltammogram 500 provides a thickness of the carbon ink layer 116 (i.e., 50 micrometres) that maximizes electrochemical performance in zinc-bromine battery applications. Such thickness of the carbon ink layer 116 represents a breakthrough in cathode current collectors design, as it addresses the fundamental limitations of metallic cathode current collectors (passivation layer formation, high resistance, and poor ionic diffusion) while identifying the most efficient material usage. The cyclic voltammogram 500 provides that approach of coating the carbon ink layer 116 not only enhances electrochemical performance but does so in a thickness-dependent manner that can be precisely optimized for specific battery chemistries.
FIG. 6 is a diagram is a diagram illustrating a cyclic voltammogram demonstrating the comparative electrochemical performance of unmodified cathode current collector and cathode current collectors with carbon ink layer, in accordance with an embodiment of the present disclosure. FIG. 6 is explained in conjunction with elements from FIGs. 1A to 5. With reference to FIG. 6, there is shown a cyclic voltammogram 600 demonstrating the comparative electrochemical performance of unmodified cathode current collectors (i.e., made of the titanium sheet) with passivation layers and the first cathode current collector 106. The experiments were conducted in an aqueous solution containing 1.0 M zinc bromide at a scan rate of 5 milli volt per second versus a Saturated Calomel Electrode (SCE).
The cyclic voltammogram 600 includes a curve 602, a curve 604, a curve 606, a curve 608 and a curve 610. The curve 602 represents the first cathode current collector 106 made of the titanium sheet exhibiting the passivation layer. The curve 604 represents the first cathode current collector 106 made of the titanium sheet exhibiting the passivation layer (titanium sheet exhibiting the passivation layer was coated with a carbon ink layer measuring 10 micrometres in thickness). The curve 606 represents the first cathode current collector 106 made of titanium with passivation layer (the titanium sheet exhibiting the passivation layer was coated with a carbon ink layer measuring 30 micrometres in thickness). The curve 608 represents the first cathode current collector 106 made of titanium (titanium sheet exhibiting the passivation layer was coated with a carbon ink layer measuring 50 micrometres in thickness). The curve 610 represents the first cathode current collector 106 made of titanium (titanium sheet exhibiting the passivation layer was coated with a carbon ink layer measuring 100 micrometres in thickness).
The curve 602 exhibits minimal electrochemical activity across the entire potential window, with negligible current response even at higher potentials. The negligible current response confirms the substantial limitations imposed by the passivation layer, which effectively blocks both ionic diffusion and electron transfer processes essential for battery operation.
In contrast, the curve 606 (titanium sheet exhibiting the passivation layer was coated with the carbon ink layer measuring 30 micrometres in thickness) demonstrates at approximately 0.2-0.3 Volts reaching current of approximately “-3.5 mA”, and a substantial oxidation peak at approximately 1.2-1.3 Volts reaching current values of approximately 4.3 mA.
The curve 604 shows an improvement over the bare passivated titanium but delivers a significantly lower current response compared to thicker coatings, indicating insufficient coverage or conductivity enhancement. The curve 608 and the curve 610 demonstrate intermediate performance, with the curve 610 (i.e., the titanium sheet exhibiting the passivation layer was coated with the carbon ink layer measuring 100 micrometres in thickness) showing diminishing returns, indicative of a coating thickness that may introduce additional resistance or mass transport limitations.
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe, and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure. ,CLAIMS:Claims
We Claim:
1. A zinc-bromine static battery device (100), comprising:
a plurality of cells (102),
wherein a first cell (102a) of the plurality of cells (102) comprises:
a first non-conducting frame (104) having a first side (104a) and a second side (104b) and a cavity (118) in a middle portion (120), the first non-conducting frame (104) is configured to provide a supporting structure to the first cell (102a);
a first cathode current collector (106) attached on the first side (104a) of the first non-conducting frame (104);
a first anode current collector (114) attached on the second side (104b) of the first non-conducting frame (104);
a first cathode layer (108), a first separator layer (110), a first anode layer (112) arranged in a sequence in the cavity (118) of the first non-conducting frame (104) and sandwiched between the first cathode current collector (106) and the first anode current collector (114); and
a carbon ink layer (116) coated on at least one side of the first cathode current collector (106) facing the first cathode layer (108) such that the first cathode current collector (106) is in contact with the first cathode layer (108) through the carbon ink layer (116).
2. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the first cathode current collector (106) is a metallic sheet made of an inert metal.
3. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the first cathode current collector (106) is a metallic sheet made of titanium.
4. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the first anode current collector (114) is a metallic sheet made of titanium but devoid of any carbon ink layer.
5. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the carbon ink layer (116) has a coating thickness ranging from 25 to 75 Micrometer (µm).
6. The zinc-bromine static battery device (100) as claimed in claim 1, wherein each of the first cathode current collector (106) and the first anode current collector (114) is a metallic sheet of thickness 0.3-0.4 millimeters (mm).
7. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the first non-conducting frame (104) comprises at least one electrolyte filing slot to fill electrolyte in the cavity (118) of the first non-conducting frame (104).
8. The zinc-bromine static battery device (100) as claimed in claim 1, wherein when the zinc-bromine static battery device (100) is in operation, a flow of electrons is effectuated from the first cathode layer (106) to the first anode layer (114) during a charging cycle of the zinc-bromine static battery device (100) and from the first anode layer (114) to the first cathode layer (108) during a discharging cycle of the zinc-bromine static battery device (100) while an oxidation of the first cathode current collector is desisted by a combination of the carbon ink layer (116) and the first cathode current collector (106).
9. The zinc-bromine static battery device (100) as claimed in claim 1, wherein the carbon ink layer (116) comprises a combination of polystyrene, N-Methyl-pyrrolidine, and Super-P carbon.
10. The zinc-bromine static battery device (100) as claimed in claim 1, wherein a carbon ink of the carbon ink layer (116) is prepared by mixing 70-90wt.% of polystyrene (PS) and 10-30wt.% of Super-P carbon (SPC) to obtain a first mixture, wherein the first mixture is dissolved in N-Methyl-pyrrolidine (NMP) to obtain the carbon ink.
11. The zinc-bromine static battery device (100) as claimed in claim1, wherein the zinc-bromine static battery device (100) is a bipolar zinc-bromine static battery device.
12. The zinc-bromine static battery device (100) as claimed in claim1, wherein the zinc-bromine static battery device (100) is a monopolar zinc-bromine static battery device configuration (200), wherein in the monopolar zinc-bromine static battery device configuration (200) the carbon ink layer is coated on both sides of a cathode current collector (210).