DESC:TECHNICAL FIELD
[0001] The present invention relates to the field of battery technology, and in particular, relates to a self-cooling alkali-ion battery and a method of fabricating thereof.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Rechargeable alkali-ion batteries such as Lithium-ion batteries, sodium-ion batteries, and the like are emerging as promising next-generation energy storage systems for various applications like grid storage, consumer devices, gadgets, automotive, Uninterrupted Power Supply (UPS) backup applications, etc. In pursuit of these applications, it is important to understand the thermal behavior and cycling performance of the battery and find solutions to reduce heat generation, minimize thermal hazards and prolong the life cycle of the alkali–ion battery. Identifying appropriate anode, cathode, and electrolyte, as well as the combination of these three components has always been challenging to develop a robust yet safe-enough alkali-ion batteries
[0004] Batteries that work on intercalation mechanisms such as lithium, sodium, magnesium, and the like, undergo charging and discharging cyclically, and reversibly. Based on their cathode, anode, and electrolyte composition and underlying electrochemistry, the processes involved during charging and discharging are partially endothermic (heat absorbing) or exothermic (heat liberating). While charging, alkali ions de-intercalate from the cathode and insert into the anode and the electrons pass from the cathode into the anode of the battery. During discharge, the same process occurs but in a reverse manner. Depending upon the capacity of the cell, the design of the cell and the current (rate) at which the cell is being charged or discharged (I2R heat losses), the effective temperature of the cell rises above the room temperature.
[0005] Usually, there is a negative impact on cycle life if batteries are operated at elevated temperatures for a prolonged time. Hence, an external cooling mechanism must be provided to operate the battery module within the desired temperature window. However, the external cooling mechanism again requires additional energy and increases the overall cost. Most alkali-ion batteries show a rise in temperature by 5-10 degree Celsius during their operation (charging and/or discharging) and hence require an external battery cooling mechanism. This results in a parasitic loss for the energy storage system and must be minimized.
[0006] Therefore, there is a need to overcome the above-mentioned drawbacks, limitations, and shortcomings associated with alkali-ion-based batteries by providing an improved, efficient, cost-effective, and safe alkali-ion battery having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperature and does not generate excess heat during the operation nor require any external cooling system. Further, there is a need to provide a method for fabricating self-cooling alkali-ion batteries.

OBJECTS OF THE INVENTION
[0007] An object of the present invention is to provide a self-cooling alkali-ion battery and a method for fabricating a self-cooling alkali-ion battery.
[0008] Yet another object of the present invention is to provide an alkali-ion battery that can have a wider operational temperature window and does not generate excess heat during the operation.
[0009] Another object of the present invention is to eliminate the need for any external cooling system in alkali-ion batteries, thereby making the battery economical.
[0010] Yet another object of the present invention is to provide an alkali-ion battery having a longer life cycle, which does not undergo any detrimental side reactions happening at elevated temperatures.
[0011] Yet another object of the present invention is to provide a safer and hazard-free alkali-ion battery.
[0012] Yet another object of the present invention is to provide an improved, efficient, cost-effective, and safe alkali-ion battery having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.
[0013] Yet another object of the present invention is to provide an improved, efficient, cost-effective, and safe sodium-ion battery having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.

SUMMARY
[0014] The present invention relates to an improved, efficient, cost-effective, and safe alkali-ion battery having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system. Further, the present disclosure also relates to a method for fabricating self-cooling alkali-ion batteries.
[0015] According to an aspect, the present disclosure elaborates upon a self-cooling alkali-ion battery cell. The self-cooling alkali-ion battery cell comprises a cathode and an anode. Further, an ether-based electrolyte is in chemical contact with the cathode and the anode. The self-cooling alkali-ion battery cell is configured to exhibit an endothermic reaction during discharging to facilitate self-cooling of the battery cell without any external cooling mechanism.
[0016] The electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like. Further, the cathode of the self-cooling alkali-ion battery cell is made of alkali family material. Furthermore, the anode is made of graphite material selected from natural graphite, synthetic graphite, and spherical graphite.
[0017] In an aspect, the battery cell is fabricated in a design form factor selected from Pouch, Prismatic, Cylindrical, Coin, and other designs. A plurality of layers of the cathode and the anode are stacked together using one or more separators in a predefined stack formation and a predefined amount of the electrolyte is added between the corresponding cathode and the anode to fabricate the battery cell. Further, the battery cell is enclosed in a casing. In another aspect, a plurality of the proposed battery cells is operatively coupled and/or stacked together in a predefined configuration to fabricate a battery of a predefined capacity.
[0018] According to another aspect, the present disclosure further elaborates upon a self-cooling sodium ion battery cell. The self-cooling sodium ion battery cell comprises a cathode comprising a NASICON family member and an anode comprising a graphite material. Further, an ether-based electrolyte is in chemical contact with the cathode and the anode. The battery cell is configured to exhibit an endothermic reaction during discharging to facilitate self-cooling of the battery cell without any external cooling mechanism.
[0019] The electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like. Further, the cathode of the self-cooling sodium-ion battery cell is made of the NASICON family material comprising sodium vanadium phosphate (NVP), but not limited to the like. Furthermore, the anode is made of graphite material selected from natural graphite, synthetic graphite, and spherical graphite. In an example, the electrolyte comprises 1M of NaPF6 in di-glyme and the cathode to anode has a mass balance ratio of 1.4: 1.
[0020] According to yet another aspect, the present disclosure further elaborates upon a method for fabricating a self-cooling battery cell is disclosed. The method comprises the steps of stacking one or more layers of a cathode and an anode in a predefined design form factor using one or more separators. The cathode comprises an alkali family material such as but not limited to a NASICON family material and the anode comprises a graphite material. Further, connection tabs associated with the corresponding anode and the corresponding cathode are welded together and the overall configuration is inserted in a laminated casing. Furthermore, a predefined amount of an ether-based electrolyte is added/filled within the casing, followed by sealing the casing.
[0021] Conventionally, heat generation in batteries is mainly due to internal resistance (irreversible heat) and change in entropy (reversible heat) depending upon the nature of the reaction during charging and discharging. In the existing Lithium-ion battery, during charging and discharging operation there is the deposition of ions from the cathode to the anode which is known as intercalation and deintercalation respectively. During intercalation, a mobile ion or molecule is reversibly incorporated into vacant sites in a crystal lattice. In this intercalation process, the entropy of the anode of the existing Li-ion battery cell increases while charging, and the entropy of the cathode increases while discharging. As a result, during the charging and discharging process of a Li-ion battery, the entropy of the Li-ions increases, resulting in the addition of heat in the battery system, thereby leading to an exothermic reaction and increase in temperature of the existing Li-ion battery.
[0022] However, with the self-cooling alkali ion battery, self-cooling sodium ion battery, and fabrication method of the present invention, when the ions move from the cathode to the anode during charging operation, the ions take their place in the anode via Co-intercalation (i.e., intercalation of two or more materials in the battery). In the present invention, the alkali- ion and electrolyte are the co-intercalation materials during charging. Further, during discharging operation of the battery, the de-intercalation takes place the same as the existing batteries.
[0023] As a result, during a charging operation of the battery cell/battery of the present invention, the co-intercalation of alkali-ions associated with the alkali family material and the electrolyte takes place in the anode to create an exothermic reaction. Further, during the discharging operation of the battery cell/battery, the entropy of the alkali -ions reduces to enable the endothermic reaction, and the battery cell demands heat from the surrounding, which correspondingly reduces the temperature of the battery cell and facilitates the self-cooling of the battery cell. With the composition of the alkali ion battery of the present invention, the heat absorption during the discharging process compensates for any temperature rise due to I2R losses or the charging/discharging process, thereby keeping the temperature of the battery cell near room temperature or within the desired window of temperature. This makes the operation of the alkali-ion battery safer in a wider operational temperature window as well as at elevated temperatures, as chances of hitting the thermal runaway threshold temperature are less, thereby increasing the life of the battery cell.
[0024] Thus, the present invention provides an improved, efficient, cost-effective, and safe alkali-ion battery with having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.

BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0026] FIG. 1 illustrates an exemplary view of the proposed self-cooling battery cell, according to an embodiment of the present invention.
[0027] FIG. 2 illustrates exemplary views of various stacking configurations in the proposed self-cooling battery cell, according to an embodiment of the present invention
[0028] FIG. 3 illustrates exemplary steps involved in the proposed method for fabricating the self-cooling battery cell, according to an embodiment of the present invention.
[0029] FIG. 4 illustrates an exemplary experimental setup for testing a single self-cooling battery cell, according to an embodiment of the present invention.
[0030] FIG. 5 illustrates an exemplary experimental setup for testing a battery comprising an array of self-cooling battery cells, according to an embodiment of the present invention.
[0031] FIG. 6 illustrates an exemplary charging and discharging graph of the self-cooling battery cell, according to an embodiment of the present invention.
[0032] FIG. 7 illustrates an exemplary charging and discharging graph of the self-cooling battery cell at high C from 1C to 5C, according to an embodiment of the present invention.
[0033] FIG. 8 illustrates an exemplary temperature and voltage vs time graph of a battery comprising an array of self-cooling battery cells for multiple cycles, according to an embodiment of the present invention.
[0034] FIG. 9 illustrates an exemplary temperature and voltage vs time graph of the self-cooling battery comprising an array of battery cells for one cycle, according to an embodiment of the present invention.
[0035] FIG. 10 illustrates an exemplary temperature and voltage vs time graph for a conventional lithium-ion battery cell.
[0036] FIG. 11 illustrates an exemplary temperature and voltage vs time graph for a conventional Li-ion phosphate battery cell.
[0037] FIG. 12 illustrates an exemplary plot depicting a charge cycle followed by a discharge cycle of a single Li-ion cell.
[0038] FIG. 13 illustrates an exemplary representation depicting the intercalation and co-intercalation process in the proposed self-cooling battery cell, according to an embodiment of the present invention.

DETAILED DESCRIPTION
[0039] The present invention relates to a self-cooling alkali-ion battery and a method of fabricating thereof which addresses the heating problem associated with existing batteries by providing an improved, efficient, cost-effective, and safe alkali-ion battery having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperature and does not generate excess heat during the operation nor require any external cooling system.
[0040] According to an aspect, the proposed self-cooling alkali-ion battery cell comprises a cathode, an anode, and an electrolyte in chemical contact with the cathode and the anode. The battery cell is configured to enable an endothermic reaction during a discharging operation to facilitate self-cooling of the battery cell
[0041] In an embodiment, during a charging operation of the battery cell, co-intercalation of alkali-ions associated with the cathode material and the electrolyte takes place in the anode to create an exothermic reaction. Further, during the discharging operation of the battery cell, the entropy of the alkali-ions reduces to enable the endothermic reaction, which correspondingly reduces the temperature of the battery cell and facilitates the self-cooling of the battery cell.
[0042] In an embodiment, the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme. Further, the cathode is made of an alkali family material. Furthermore, the anode is made of graphite material selected from natural graphite, synthetic graphite, and spherical graphite.
[0043] In an embodiment, the battery cell is adapted to be fabricated in a design form factor selected from Pouch, Prismatic, Cylindrical, and Coin. Further, a plurality of layers of the cathode and the anode are stacked together using one or more separators in a predefined stack formation and a predefined amount of the electrolyte is added between the corresponding cathode and the anode to fabricate the battery cell. Further, the battery cell is enclosed in a casing. Furthermore, plurality of the battery cells is configured to be operatively coupled and/or stacked together in a predefined configuration to fabricate a battery of a predefined capacity.
[0044] According to an aspect, the proposed self-cooling sodium ion battery cell comprises a cathode comprising a NASICON family material, an anode comprising a graphite material, and an electrolyte in chemical contact with the cathode and the anode. The electrolyte is an ether-based electrolyte. The battery cell is configured to enable an endothermic reaction during a discharging operation to facilitate self-cooling of the battery cell.
[0045] In an embodiment, during a charging operation of the battery cell, co-intercalation of Na-ions associated with the NASICON family material and the electrolyte takes place in the anode to create an exothermic reaction.
[0046] In an embodiment, during the discharging operation of the battery cell, the entropy of the Na-ions reduces to enable the endothermic reaction, which correspondingly reduces the temperature of the battery cell and facilitates the self-cooling of the battery cell.
[0047] In an embodiment, the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme. Further, the cathode is made of the NASICON family material comprising sodium vanadium phosphate (NVP). Furthermore, the anode is made of graphite material selected from natural graphite, synthetic graphite, and spherical graphite.
[0048] In an embodiment, the electrolyte comprises 1M of NaPF6 in di-glyme.
[0049] In an embodiment, the cathode to the anode has a mass balance ratio of 1.4:1.
[0050] According to another aspect, the proposed method for fabricating a self-cooling battery cell is disclosed. The method comprises the steps of stacking one or more layers of a cathode and an anode in a predefined design form factor using one or more separators, where the cathode comprises a NASICON family material and the anode comprises a graphite material. The method further comprises the steps of welding connection tabs associated with the corresponding anode and the corresponding cathode together followed by inserting in a laminated casing, adding a predefined amount of an ether-based electrolyte within the casing, and sealing the casing. The fabricated battery is configured to enable an endothermic reaction during a discharging operation to facilitate the self-cooling of the battery cell.
[0051] While various embodiments of the present disclosure have been elaborated for the proposed self-cooling alkali-ion battery being a sodium ion battery comprising the cathode made of a NASICON family material, however, the teachings of the present disclosure are equally applicable for other alkali-based batteries compositions, such as but not limited to Lithium, Magnesium and the like, and all such embodiments are well within the scope of the present disclosure without any limitation in the scope.
[0052] Referring to FIG. 1, the proposed self-cooling battery cell 100 (also referred to as battery cell 100, herein) includes a cathode (positive electrode) 102 comprising an alkali family material such as but not limited to a NASICON family material, lithium-ion family material,, potassium-ion family material, magnesium-ion family material, and the like. The battery cell further includes an anode (negative electrode) 104 comprising a graphite material, and an ether-based electrolyte and the like in chemical contact with the cathode 102 and the anode 104. The battery cell 100 is configured to exhibit an endothermic reaction during discharging to facilitate self-cooling of the battery cell 100 without any external cooling mechanism.
[0053] In an embodiment, the cathode material for the alkali-ion battery cell 100 is selected from any of the alkali-based cathode material families without any limitation. In addition, the anode material for the alkali-ion battery cell 100 is selected from any anode material that supports a co-intercalation mechanism. Further, the electrolyte for the alkali-ion battery cell 100 is selected from any electrolyte that allows or supports the co-intercalation mechanism. The use of an ether family-based electrolyte in the alkali-ion battery cell 100 enables the co-intercalation in all the alkali base compound ions into the graphite (not limited to natural graphite, synthetic graphite, spherical graphite, etc).
[0054] In a preferred embodiment, the self-cooling alkali-ion battery cell 100 is a sodium-ion battery cell where the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like. The electrolyte also includes additives to provide the desired viscosity of the electrolyte. Further, the cathode 102 of the sodium-ion battery cell is made of the NASICON family material comprising sodium vanadium phosphate (NVP), but not limited to the like. The cathode 102 further includes a solvent N-methyl Pyridine (NMP) and a binder Polyvinylidene fluoride (PVDF) to bind the NVP material. The cathode 102 can then be coated with a conductive material. material. Furthermore, the anode 104 is made of graphite material selected from natural graphite, synthetic graphite, and spherical graphite. The anode 104 also includes a binder to bind the graphite material, which can then be coated with a conductive material.
[0055] In another embodiment, alkali chemistry Lithium (Li) and its compound such as but limited to LiFePO4, LiCoO2. Lithium metal, Nickel Manganese cobalt, and the like, are used as the cathode 102 in the self-cooling alkali-ion battery cell 100. Further, graphite material such as but not limited to natural graphite, synthetic graphite, spherical graphite, and the like, is used as the anode 104 in the battery cell 100 for the ionic conductivity in the electrolyte selected from the ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like.
[0056] In yet another embodiment, alkali chemistry of Potassium (K) and its compounds such as but limited to KMNO2, Potassium metal, KVOPO4, KVPO4F, and the like, are used as the cathode 102 in the self-cooling alkali-ion battery cell 100, Further, the graphite material such as but limited to natural graphite, synthetic graphite, spherical graphite, and the like, is used the anode 104 in the battery cell 100 and for the ionic conductivity in the electrolyte selected from ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like.
[0057] In an exemplary embodiment, the electrolyte for the self-cooling sodium-ion battery cell 100 comprises 1M of NaPF6 in di-glyme and the cathode to anode has a mass balance ratio of 1.4: 1. This mass balance ensures the capacity balance between the cathode 102 and anode 104 and has a strong correlation with the final cell capacity and stability. The excess mass balance of the cathode 102 gives better cycle life. However, any other suitable mass balance ratio may also be selected based on the requirement.
[0058] The proposed battery cell 100 is fabricated in a Pouch design as shown in FIG. 1 exhibiting the self-cooling feature. The pouch-shaped battery cell 100 comprises the cathode 102, the anode 104, the electrolyte, and one or more separators 106 (collectively referred to as separators 106 and individually referred to as a separator 106, herein). The cathode 102 and anode 104 are parallelly configured with the separator 106 located between the anode 104 and cathode 102, so as to prevent an electrical short circuit. The electrolyte acting as an ion conductor is also used, which remains in chemical contact with the cathode 102 and anode 104. In order to protect the internal material, the battery cell 100 is wrapped in a casing or pouch 108, such that electrical terminals/tabs of the cathode 102 and anode 104 extend out of the pouch to facilitate electrical coupling of the Pouch-battery cell 100 to a power source and/or electrical loads.
[0059] In an exemplary embodiment, the pouch 108 used for the battery cell comprises multiple layers. The outermost base layer (Oriented Nylon) is a material for ensuring formability and insulation. An adhesive with dry lamination is used to maintain the laminate strength between the base layer and the barrier layer. The barrier layer is typically made of aluminum so as to maintain moldability and air-tightness. An adhesive layer (S-adhesive or adhesive with polypropylene) is needed in order to maintain the water vapor barrier properties, as well as the adhesion between the barrier layer and the sealant layer. The sealant layer (casting polypropylene (CPP) or polypropylene (PP)) is a layer for maintaining the sealing strength, as well as securing the heat-resistant and insulating properties. Based on the barrier layer, the outer layer is composed of biaxially-oriented nylon, while the inner layer is composed of non-elongated CPP or PP.
[0060] In other embodiments, the proposed battery cell 100 can also be fabricated in other design form factors selected from Prismatic, Cylindrical, Coin, and the likes without any limitation, and all such embodiments are well within the scope of the present invention. In all such design form factors, the battery cell exhibits similar self-cooling and charge-discharge VS temperature response. In an embodiment, a plurality of layers of the cathode 102 and the anode 104 are stacked together using separator(s) in a predefined stack formation such as but not limited to the single sheet stacking, Z-stacking, cylindrical stacking, and prismatic winding stacking as shown in FIG. 2. Further, a predefined amount of the electrolyte is added between the corresponding cathode 102 and the anode 104 to fabricate the battery cell 100. In addition, the battery cell 100 is enclosed in a laminated casing 108 with the electrical terminals of the cathode 102 and anode 104 extending out of the casing 108 to facilitate electrical coupling of the battery cell 100 to a power source and/or electrical loads.
[0061] In another embodiment, a plurality of the proposed battery cells 100 is configured to be operatively coupled and/or stacked together in a predefined configuration including series configuration, parallel configuration, and a combination thereof, to fabricate a battery (not shown) of a predefined charge capacity (Ah).
[0062] Referring to FIG. 3, in another aspect, the present invention elaborates upon method 300 for fabricating a self-cooling battery cell. Method 300 comprises step 302 of stacking one or more layers of a cathode and an anode in a predefined design form factor using one or more separators. The cathode comprises an alkali family material such as but not limited to NASICON family material and the anode comprises a graphite material. In an embodiment, the cathode is made of the NASICON family material comprising sodium vanadium phosphate (NVP), but not limited to the like. Further, the anode is made of graphite material selected from any but not limited to natural graphite, synthetic graphite, spherical graphite, and the like.
[0063] Method 300 further comprises step 304 of welding connection tabs associated with the corresponding anode and the corresponding cathode together followed by inserting in a laminated casing such that the electrical terminals of the battery cell remain accessible outside the casing. Method 300 further comprises step 306 of adding a predefined amount of an ether-based electrolyte within the casing of step 304 followed by sealing the casing to form the battery cell.
[0064] In an embodiment, the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme, but not limited to the like. In an exemplary embodiment, the electrolyte comprises 1M of NaPF6 in di-glyme and the cathode to anode has a mass balance ratio of 1.4: 1.
[0065] In an aspect (not shown), a method for fabricating a battery comprising multiple battery cells comprises the steps of operatively coupling and/or stacking a plurality of the proposed battery cells together in a predefined configuration including series configuration, parallel configuration, and a combination thereof, to fabricate the battery of a predefined charge capacity (Ah).
[0066] Conventionally, heat generation in batteries is mainly due to internal resistance (irreversible heat) and change in entropy (reversible heat) depending upon the nature of the reaction during charging and discharging. In the existing Lithium-ion battery, during charging and discharging operation there is the deposition of ions from the cathode to the anode which is known as intercalation and deintercalation respectively. During intercalation, a mobile ion or molecule is reversibly incorporated into vacant sites in a crystal lattice. In this intercalation process, the entropy of the anode of the existing Li-ion battery cell increases while charging, and the entropy of the cathode increases while discharging. As a result, during the charging and discharging process of a Li-ion battery, the entropy of the Li-ions increases, resulting in the addition of heat in the battery system, thereby leading to an exothermic reaction and increase in temperature of the existing Li-ion battery, which can also be inferred from the experimental results of FIGs. 10 to 12. As illustrated in FIG. 12, the plot shows a charge cycle followed by a discharge cycle of a single Li-ion battery cell and details of the heat flow into and out of the existing Li-ion cell during the process. The initial section (labeled A) shows the endothermic nature of the charge chemical reaction, The discharge section (labeled B) is also an exothermic reaction. In addition, near the end of the discharge, the heat produced increases rapidly, indicating an increase in the impedance of the Li-ion cell near the end of the cell capacity.
[0067] The present invention overcomes the above drawback associated with the existing battery cells. Those skilled in the art would appreciate that with the self-cooling alkali ion battery cell 100 and the fabrication method 300 of the present invention, when the ions move from the cathode 102 to the anode 104 during charging operation, the ions take their place in the anode 104 via Co-intercalation (i.e., intercalation of two or more materials in the battery cell). In the present invention, as shown in FIG. 13, the alkali/Na-ion and electrolyte are the co-intercalation materials during charging. Further, during discharging operation of the battery cell 100, the de-intercalation takes place the same as the existing batteries. As a result, during a charging operation of the battery cell/battery 100 of the present invention, the co-intercalation of alkali/Na-ions associated with the alkali/NASICON family material and the electrolyte takes place in the anode 104 to create an exothermic reaction. Further, during the discharging operation of the battery cell/battery 100, the entropy of the alkali/Na-ions reduces to enable the endothermic reaction, and the battery cell 100 demands heat from the surrounding, which correspondingly reduces the temperature of the battery cell 100 and facilitates the self-cooling of the battery cell 100.
[0068] Thus, with the composition of the alkali ion battery and/or sodium ion battery of the present invention, the heat absorption during the discharging process compensates for any temperature rise due to I2R losses or the charging/discharging process, thereby keeping the temperature of the battery cell near room temperature or within the desired window of temperature. This makes the operation of the alkali-ion battery or sodium-ion battery safer in a wider operational temperature window as well as at elevated temperatures, as chances of hitting the thermal runaway threshold temperature are less, thereby increasing the life of the battery cell.
[0069] Referring to FIG. 4, an exemplary experiment setup for testing a single unit of the proposed self-cooling battery cell 100 is disclosed. The Pouch battery cell 100 of FIG. 1 was selected for testing. A little pressure was applied over the battery cell 100 for packaging purpose. Further, during the performance cycle, the temperature data of the battery cell 100 was measured. As illustrated, an acrylic plate 404 having multiple holes 402 was selected. The holes 402 provide an arrangement for accommodating temperature sensors (T1 to T3). Once, the plate 404 is placed over the battery cell 100, the temperature sensors (T1 to T3) were placed in the holes 402, which remain in contact with the surface of the battery cell 100. Later on, a little pressure was applied over the plate 404 for packaging purposes. Further, during the performance cycle, the temperature data of the battery cell 100 was measured using the sensors (T1 to T3).
[0070] Referring to FIG. 5, an exemplary experiment arrangement for testing multiple units of the proposed self-cooling battery cell 100 is disclosed. As illustrated, multiple (six) battery cells 100 of FIG. 1 were used. The battery cells 100 were configured parallelly with a foam layer 504 being used to give cushioning and fire-retardant effects from one battery cell to another. In addition, intermediate plates 506 were used between the battery cell 100 and foam layer 504 to remove/add heat from/to the cells 100 respectively. The battery cells 100, foam layers 504, and intermediate plates 506 were then packaged and pressure was applied to hold the battery cells together using a pressure plate 502 from top. Further, two temperature sensors were placed around the intermediate plates 506, with two sensors at the tabs and one sensor outside to observe the ambient temperature.
[0071] FIG. 6 illustrates an exemplary charging and discharging graph of the self-cooling battery cell using the experimental setup of FIG. 4. FIG. 7 illustrates an exemplary charging and discharging graph of the self-cooling battery cell at high C from 1C to 5C using the experimental setup of FIG. 4. As can be inferred from FIGs. 6 and 7, the temperature of the battery cell increased above the ambient temperature during charging cycle due to the co-intercalation of alkali/Na-ions associated with the alkali/NASICON family material and the electrolyte taking place in the anode to create an exothermic reaction. Further, the temperature of the battery cell drops below the ambient temperature during discharging cycle as the entropy of the alkali/Na-ions reduces to enable the endothermic reaction, and the battery cell demands heat from the surrounding, which correspondingly reduces the temperature of the battery cell and facilitates the self-cooling of the battery cell.
[0072] FIG. 8 illustrates an exemplary temperature and voltage vs time graph of the self-cooling battery comprising an array of cells for multiple cycles using the experimental setup of FIG. 5. FIG. 9 illustrates an exemplary temperature and voltage vs time graph of the self-cooling battery comprising an array of cells for one cycle using the experimental setup of FIG. 5. As can be inferred from FIGs. 8 and 9, similar results were observed, wherein the temperature of the battery cell increased above the ambient temperature during the charging cycle due to the exothermic reaction, and the temperature of the battery cell drops below the ambient temperature during discharging cycle due to the endothermic reaction.
[0073] Thus, the present invention provides an improved, efficient, cost-effective, and safe alkali-ion battery with having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.
[0074] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art

ADVANTAGES OF THE PRESENT INVENTION
[0075] The present invention provides a self-cooling alkali-ion battery and a method for fabricating a self-cooling alkali-ion battery.
[0076] The present invention provides an alkali-ion battery that can have a wider operational temperature window and does not generate excess heat during operation.
[0077] The present invention eliminates the need for any external cooling system in alkali-ion batteries, thereby making the battery economical.
[0078] The present invention provides an alkali-ion battery having a longer life cycle, which does not undergo any detrimental side reactions happening at elevated temperatures.
[0079] The present invention provides a safer and hazard-free alkali-ion battery.
[0080] The present invention provides an improved, efficient, cost-effective, and safe alkali-ion battery with having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.

[0081] The present invention provides an improved, efficient, cost-effective, and safe sodium-ion battery with having longer life and a wider operational temperature window, which does not undergo any detrimental side reactions happening at elevated temperatures and does not generate excess heat during the operation nor require any external cooling system.

,CLAIMS:1. A self-cooling alkali-ion battery cell (100) comprising:
a cathode (102);
an anode (104); and
an electrolyte in chemical contact with the cathode (102) and the anode (104); and
wherein the battery cell (100) is configured to enable an endothermic reaction during a discharging operation to facilitate self-cooling of the battery cell (100).

2. The self-cooling alkali ion battery cell (100) as claimed in claim 1, wherein during a charging operation of the battery cell (100), co-intercalation of alkali-ions associated with the cathode material and the electrolyte takes place in the anode (104) to create an exothermic reaction, and
wherein during the discharging operation of the battery cell (100), entropy of the alkali-ions reduces to enable the endothermic reaction, which correspondingly reduces the temperature of the battery cell (100) and facilitates the self-cooling of the battery cell (100).

3. The self-cooling alkali-ion battery cell (100) as claimed in claim 1, wherein,
the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme;
the cathode (102) is made of an alkali family material; and
the anode (104) is made of the graphite material selected from natural graphite, synthetic graphite, and spherical graphite.

4. The self-cooling alkali-ion battery cell (100) as claimed in claim 1, wherein the battery cell (100) is adapted to be fabricated in a design form factor selected from Pouch, Prismatic, Cylindrical, and Coin, and wherein a plurality of layers of the cathode (102) and the anode (104) are stacked together using one or more separators (106) in a predefined stack formation and a predefined amount of the electrolyte is added between the corresponding cathode (102) and the anode (104) to fabricate the battery cell (100), and wherein the battery cell (100) is enclosed in a casing (108).

5. A self-cooling sodium ion battery cell (100) comprising:
a cathode (102) comprising a NASICON family material;
an anode (104) comprising a graphite material; and
an electrolyte in chemical contact with the cathode (102) and the anode (104), wherein the electrolyte is an ether-based electrolyte; and
wherein the battery cell (100) is configured to enable an endothermic reaction during a discharging operation to facilitate self-cooling of the battery cell (100).

6. The self-cooling sodium ion battery cell (100) as claimed in claim 5, wherein during a charging operation of the battery cell (100), co-intercalation of Na-ions associated with the NASICON family material and the electrolyte takes place in the anode (104) to create an exothermic reaction.

7. The self-cooling sodium ion battery cell (100) as claimed in claim 6, wherein during the discharging operation of the battery cell (100), entropy of the Na-ions reduces to enable the endothermic reaction, which correspondingly reduces the temperature of the battery cell (100) and facilitates the self-cooling of the battery cell (100).

8. The self-cooling sodium ion battery cell (100) as claimed in claim 5, wherein,
the electrolyte is selected from an ether family of solvents comprising any or a combination of diglyme, tri-glyme, and tetra-glyme;
the cathode (102) is made of the NASICON family material comprising sodium vanadium phosphate (NVP); and
the anode (104) is made of the graphite material selected from natural graphite, synthetic graphite, and spherical graphite.

9. The self-cooling sodium ion battery cell (100) as claimed in claim 5, wherein the electrolyte comprises 1M of NaPF6 in di-glyme, wherein the cathode (102) to the anode (104) has a mass balance ratio of 1.4:1.

10. A method (300) for fabricating a self-cooling battery cell (100), the method (300) comprising the steps of:
stacking (302) one or more layers of a cathode (102) and an anode (104) in a predefined design form factor using one or more separators (106), wherein the cathode (102) comprises any of an alkali family material or a NASICON family material, and the anode (104) comprises a graphite material;
welding (304) connection tabs associated with the corresponding anode (104) and the corresponding cathode (102) together followed by inserting in a laminated casing (108); and
adding (306) a predefined amount of an ether-based electrolyte within the casing (108) and sealing the casing (108),
wherein the battery is configured to enable an endothermic reaction during a discharging operation to facilitate the self-cooling of the battery cell (100).