Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See sections 10 & rule 13)
1. TITLE OF THE INVENTION
NEGATIVE ELECTRODE FOR SODIUM ION BATTERY AND PREPARATION METHOD OF THE SAME
2. APPLICANT (S)
NAME NATIONALITY ADDRESS
INDIGENOUS ENERGY STORAGE TECHNOLOGIES PVT. LTD. IN I-10, 2nd Floor, Tides Business Incubator, IIT Roorkee, Roorkee-247667, Uttarakhand, India.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:
[001] The present invention relates to the field of sodium ion battery. The present invention in particular relates to a negative electrode slurry and method for preparing the same, which involves combination of a clustered complex consisting of a negative electrode slurry having active material, binder and the conductive additives (CA) with a solvent to optimize the rheology and coating properties of the slurry.
DESCRIPTION OF THE RELATED ART:
[002] Lithium-ion batteries are widely used in modern portable electronic devices and electric vehicles due to their high energy density and long cycle life. However, lithium is suffering from the scarcity and it is an expensive element that led to concerns about the sustainability and cost of lithium-ion batteries. Consequently, there has been growing demand in inventing alternative battery technologies that should be based on more abundant and cost-effective elements. The best alternative is sodium-ion batteries, which use sodium ions instead of lithium ions to store and release energy. Sodium is actually abundant and widely available as NaCl in the water bodies and other parts of earth, making it a potentially more sustainable and cost-effective option.
[003] Reference may be made to the following:
[004] Publication No. CN115849367 relates to a sodium-ion battery negative electrode material based on a natural graphite raw material, a preparation method of the sodium-ion battery negative electrode material and a sodium-ion battery. The publication describes a sodium-ion battery negative electrode material and its preparation method using natural graphite. While it focuses on modifying the material's structure for improved electrochemical performance, it does not address the rheological parameters or wettability of the slurry.
[005] Present invention optimizes the viscosity of the binder in the negative electrode slurry to enhance its rheological properties and wettability. This distinction highlights the unique contribution of the invention in addressing these crucial factors for better battery performance and stability.
[006] Publication No. CN115763682 discloses a preparation method of a sodium ion battery negative electrode slurry and a negative electrode slurry, and the preparation method of the sodium ion battery negative electrode slurry comprises the following steps: S1, preparing a CMC glue solution; s2, hard carbon and SP are added into the stirring pot at the same time, first slurry is formed through stirring, and SP is a conductive agent; s3, a CMC glue solution is added into the first slurry, stirring is performed to form second slurry, and the solid content of the second slurry is 73%-76%; s4, adding the residual CMC glue solution into the second slurry in batches, and adding a solvent to adjust the solid content to form third slurry; the solid content of the third slurry is 48-52%; s5, adding SBR into the third slurry, and performing vacuum low-speed stirring to form fourth slurry; and S6, sieving and discharging the fourth slurry to obtain the negative electrode slurry, wherein the solid content of the negative electrode slurry is 47-51%. The above patent is prepared in two steps as first slurry and second slurry. They prepared the CMC glue that is added to the secondary slurry to get better battery performance.
[007] Present invention describes the rheological parameters along with the adhesivity of the slurry in the aluminum based current collector.
[008] Publication No. CN115763814 relates to electrode slurry and a preparation method thereof, a negative electrode plate and a lithium-ion battery. The negative electrode slurry comprises a negative electrode active material, a conductive agent, a thickening agent, a binder, a material with cationic groups and a solvent, the thickening agent comprises sodium carboxy methyl cellulose (CMC), and the binder comprises styrene butadiene rubber (SBR). The patent focuses on addressing the SBR floating issue in the CMC-SBR binder system for electrode slurry. It offers advantages of improved roller sticking, enhanced bonding force, simplified operation, and low cost.
[009] The present invention provides composition, rheological optimization, agri-waste-derived active material, specific viscosity control, binder wettability, slurry rheology, porosity determination, and superior electrode performance. These differentiating features contribute to advancements in sodium-ion battery technology.
[010] Publication No. CN115621464 relates to sodium ion battery negative electrode slurry and a preparation method thereof, a battery negative electrode plate and a preparation method thereof, and a battery and a preparation method thereof. This focuses on a sodium-ion battery negative electrode slurry composition and its preparation method, emphasizing the use of a lubricant like one or a combination of more of graphene, black phosphorus, MoS2, Ti3C2, SnS, C3N4, tungsten carbide and hexagonal boron nitride.
[011] The present invention is not related to the lubricant etc but it fixes the range of viscosity of the binder to tune the viscoelasticity and adhesivity of slurry to get better electrochemical response.
[012] Publication No. CN115301496 relates to a sodium ion battery negative plate dipping and coating device capable of uniformly dispersing slurry and an operation method, the sodium ion battery negative plate dipping and coating device comprises a device base frame, a dipping and coating mechanism and a polar plate shifting carrier, the polar plate shifting carrier is arranged on the top surface of the device base frame, and the polar plate shifting carrier can transversely move on the top surface of the device base frame; the dipping coating mechanism is fixed to the inner side of the front end of the device base frame, and the rear bottom side of the dipping coating mechanism can make contact with the top face of the polar plate shifting carrier. This patent introduces a sodium-ion battery negative plate dipping and coating device along with its operation method. This device offers a solution for achieving uniform dispersion of slurry during the coating process of sodium-ion battery negative plates, ensuring improved quality and consistency.
[013] However, present invention offers unique aspects such the binder having a particular range of viscosity that control rheological parameter. It has agri-waste-derived active material with tuned adhesivity as according to the contact angle of slurry on the Al based current collector and surface tension.
[014] Publication No. CN115312717 discloses low-temperature-resistant lithium ion battery negative electrode slurry as well as a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The low-temperature-resistant lithium ion battery negative electrode slurry is prepared from the following components in percentage by mass: 42 to 48.5 percent of a negative electrode material, 0.1 to 3.0 percent of a poly acrylate adhesive, 1 to 2.0 percent of a conductive agent, 0.6 to 1.5 percent of sodium carboxy methyl cellulose and 45 to 55 percent of deionized water. The patent primarily focusses on the low temperature resistant, for that they have added the polyacrylate adhesive to the slurry.
[015] However, present invention focus on achieving the enhanced electrochemical performance using the viscoelastic parameters and adhesivity of the slurry controlled by the binder having the viscosity in particular range.
[016] Publication No. CN115275206 relates to a sodium ion battery negative electrode and a sodium ion battery. The patent has not claimed the rheological and adhesive parameters of the slurry rather is directly prepared the electrode.
[017] The present invention provides negative electrode with the tuned viscoelastic and adhesivity parameters that results in the enhancement in the overall electrochemical performance along with better mechanical stability of electrode.
[018] Publication No. CN110504421 discloses a binder for a negative electrode of a lithium ion battery and negative electrode slurry. The patent introduces a binder composition and negative electrode slurry preparation method for lithium-ion batteries. The specific parts by mass ratios and inclusion of a film-forming additive highlight the novelty of the binder formulation with different additives.
[019] However, the patent stands out with its aspects including the binder having the viscosity in the particular range that tuned the viscoelastic and adhesive parameters that results in better wettability on the Al based current collector to develop the electrode.
[020] Publication No. CN115224228 relates to the technical field of silicon-based fast-charging lithium-ion batteries, in particular to a silicon-based fast-charging composite negative electrode slurry composition and a preparation method thereof. The mentioned patent focuses on the development of a silicon-based fast-charging composite negative electrode slurry for lithium-ion batteries.
[021] The present invention emphasizes the use of a hard carbon-based active material and employs advanced characterization techniques for achieving a more homogenous coating on the current collector. It focuses on the achieving the enhanced electrochemical performance with the tuned rheology and wettability of the slurry on the Al based current collector.
[022] Publication No. CN115188965 relates to sodium-ion battery negative electrode slurry and a method for preparing a pole piece from the sodium-ion battery negative electrode slurry. The mentioned patent focuses emphasizes the addition of a small amount of porous medium to improve the rate capability of the negative electrode in sodium-ion batteries, it does not specifically address the rheology and wettability aspects of the slurry.
[023] However, present invention differentiates itself by considering the rheological properties and binder wettability using techniques such as contact angle measurement and surface tension analysis. This comprehensive approach allows us to optimize the slurry's homogeneity, adhesion, and coating characteristics on the current collector, leading to enhanced electrochemical performance in sodium-ion battery systems.
[024] Publication No. CN115692712 discloses a negative electrode additive, a negative electrode material, a negative electrode plate and a lithium ion secondary battery, and belongs to the technical field of lithium ion batteries. This patent focuses on optimizing the rheological properties and binder wettability of the slurry for sodium-ion batteries, but above patent introduces a unique negative electrode additive derived from 1,1-difluoroethylene for lithium-ion batteries for better electrochemical performances.
[025] The present invention addresses the unique coating characteristics and homogeneity of the slurry using the binder viscosity in particular range. This achieves better electrochemical performance and mechanical stability with the better wettability.
[026] Publication No. CN115799443 discloses a micro porous aluminum foil electrode of a sodium ion battery and a preparation method of the micro porous aluminum foil electrode, and belongs to the technical field of electro material. The above patent is preparing the cathode and anode slurry and coating on the aluminum foil. It has claimed the range of viscosity but at what shear rate.
[027] It has not claimed the characteristics of slurry that it is more elastic than viscous or more viscous than elastic. It has not claimed the contact angle and surface tension. It claims the shear viscosity specific range at the shear rate of 102 (1/s).
[028] Publication No. JP2021515358 relates to an anode slurry composition which can be applied to production of anodes to cope well with shrinkage and expansion by repeated charge and discharge, and has excellent binding force between active materials and adhesive force to a current collector, and an anode and a secondary battery, comprising the same. The invention focuses on the composition of the acrylic polymer and its effect on the negative electrode active material and explores the formulation of a slurry, potentially incorporating silicon active materials.
[029] It develops the negative electrode using the hard carbon as the active material that have plateau capacity. The better electrochemical performance and mechanical stability is tuned using the rheological and adhesive parameters by modifying eh better wettability on the current collector of Al foil.
[030] Publication No. US2022285669 relates to semi-solid suspensions, and more particularly to systems and methods for preparing semi-solid suspensions for use as electrodes in electrochemical devices such as, for example batteries. This introduces a method for preparing semi-solid suspensions as electrodes for electrochemical devices, such as batteries. The method involves combining an active material with an electrolyte to form an intermediate material, which is then mixed with a conductive additive. The resulting electrode material is mixed to achieve a high mixing index of at least 0.80 before being formed into a semi-solid electrode.
[031] However, present invention focuses to tune the electrochemical performance and mechanical stability with the optimization of rheology and wettability of slurry with the particular range viscosity of added binder.
[032] Publication No. US2018151866 provides a slurry composition for a secondary battery negative electrode that has excellent producibility and can suppress cell swelling and an increase in internal resistance in a secondary battery. This aims to improve producibility and suppress cell swelling and internal resistance. It consists of a carbon-based negative electrode active material with specific surface characteristics and a particulate polymer with controlled surface acid content.
[033] Present invention offers a distinct advantage by addressing the rheological properties and binder wettability of the slurry, optimizing coating characteristics and adhesion. By considering these factors, our patent enhances the homogeneity, stability, and electrochemical performance and mechanical stability of the negative electrode in sodium-ion batteries.
[034] Publication No. CN115036463 discloses a sodium ion battery negative electrode which comprises a current collector foil and electrode coatings which are positioned on two surfaces of the current collector foil and are prepared from negative electrode slurry, and the negative electrode slurry comprises hard carbon, a conductive agent, a binder, an additive and ultrapure water; the negative electrode slurry is prepared from the following components in percentage by weight: 48 to 49 weight percent of hard carbon, 0.3 to 0.6 weight percent of a conductive agent, 1.5 to 2.5 weight percent of a binder, 2.0 to 3.0 weight percent of an additive and 46.0 to 47.0 weight percent of ultrapure water; the additive is a combination of more than one of propylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether; according to the invention, high-boiling-point ethers and carbonic esters are added when the negative pole piece of the battery is produced, so that the coating cracking phenomenon can be avoided, the product performance is ensured, and the product quality and the production efficiency are improved.
[035] This focuses on the conductive additives and dilution additives to enhance the electrochemical performance. The conductive additive is prepared by adding 64.52% ultrapure water and diglyme into the mixing tank, stir for 30 minutes with the parameters of revolution 25 rpm/min and dispersion 500 rpm/min to obtain a colorless and transparent additive liquid, that is, anti-cracking liquid.
[036] However, present invention offers a unique advantage by considering the rheological properties and binder wettability of the slurry. The adhesion of slurry on the Al based current collector using the binder having particular rage of viscosity and surface tension.
[037] Publication No. CN111313005 discloses a silicon-carbon negative electrode slurry mixing method, and belongs to the field of lithium-ion battery preparation. The method specifically comprises the following steps: firstly, adding sodium carboxy methyl cellulose and deionized water into a planetary stirrer and stirring for 1.5 to 2.5 hours; then adding a carbon black Super-p conductive agent and/or a carbon nanotube conductive agent and a poly acrylic acid binder; stirring for 1-2 hours, then adding the silicon-carbon composite material in twice stirring for at least 2-4 hours finally adding dissolved ethylene carbonate/propylene carbonate, stirring for 1.5-2.5 hours, adding the residual deionized water, adjusting the viscosity of the slurry to meet the technical requirements, performing reverse defoaming and sieving the slurry to obtain the silicon-carbon negative electrode slurry to be prepared. The patent discloses the development of slurry with the silicon carbon as active material. There focus in the claim section is on the speed and time of stirring while preparing the slurry.
[038] Whereas, present invention uses hard carbon as the active material that have plateau capacity, further present invention uses the binder having viscosity in the particular range that tune the rheological parameters and wettability of slurry.
[039] Publication No. EP3690991 relates to a negative electrode slurry composition including clay particles having a plate-type structure and an average particle diameter (D50) of 10 nm to 2 µm carboxy methylcellulose (CMC) a negative electrode active material, and an aqueous solvent, wherein a weight ratio of the carboxy methylcellulose and the clay particles is 9.5:0.5 to 4:6. The patent mainly focuses on the performance of the active material that is clay particles having a plate-type structure, they have not claimed about the rheology of the slurry, wettability of slurry.
[040] Present invention have hard carbon as active material. Further the rheological parameters and wettability of slurry has been optimized.
[041] Publication No. CN115632130 discloses application of diquat glue in negative electrode slurry, the negative electrode slurry, a preparation method and a battery negative electrode material. The battery negative electrode material can be obtained by mixing the diquat as a stabilizer and/or a binder with an active substance, a conductive agent and water according to a specific proportion and coating a current collector with the battery negative electrode slurry. The patent is specifically for the diutan used as stabilizer/ or binder which further helps in stabilizing the viscosity of slurry.
[042] In present invention the viscosity of the binder has been fixed that will further optimize the viscosity of the slurry at shear rate of the 102 1/s.
[043] Publication No. CN115020655 discloses a sodium ion battery negative electrode material and a preparation method thereof, and relates to the technical field of sodium ion batteries, and the preparation method comprises the following steps: step 1, mixing and stirring crystalline nanometer silicon with the particle size of 55-185 nm, conductive carbon black, poly tetra fluoroethylene and polyvinyl alcohol, and grinding in N-methyl pyrrolidone and water to obtain uniform silicon negative electrode slurry for later use; according to the copper foil coating and drying device, coating and drying work can be completed synchronously, and meanwhile copper foil can be cut off in the horizontal direction and the vertical direction; the whole motion is intermittent motion, adjustment in the vertical direction and the horizontal direction and final conveying are completed step by step through pushing of the first air cylinder and arrangement of a limiting structure, and the cutting precision is higher. The above describes a method involves several steps, including mixing and stirring crystalline nanometer silicon, conductive carbon black, polytetrafluoroethylene, and polyvinyl alcohol in N-methyl pyrrolidone and water to obtain a uniform silicon negative electrode slurry. The slurry is then used for coating and drying on copper foil using a specific device that allows simultaneous coating and drying while providing precise cutting in both horizontal and vertical directions.
[044] The present invention offers a distinct advantage by focusing on comprehensive optimizations of rheological properties, binder wettability, and other parameters specific to sodium-ion battery slurries, we have used the aluminum foil as current collector. It enhances the homogeneity, adhesion, and coating properties of the slurry on the current collector, resulting in improved electrochemical performance.
[045] Publication No. JP2019079646 relates to a binder composition and a slurry for a negative electrode of a sodium ion battery, which can suppress the increase in the irreversible capacity in initial charge and discharge, and has a high cycle retaining rate, and a negative electrode and a sodium ion battery. This discloses a binder composition and slurry for a sodium-ion battery negative electrode. The binder composition aims to minimize irreversible capacity. It comprises a graft copolymer of (meth)acrylonitrile-grafted polyvinyl alcohol, with specified molecular weight and proportions. The above patent does not claim the rheological parameters and wettability.
[046] However, present invention is based on the flow behavior and adhesivity of slurry. It uses the binder having the viscosity in the particular range that tune the viscoelastic behavior of slurry, that results in high electrochemical performance and mechanical stability.
[047] Publication No. CN107170957 provides a sodium ion battery negative electrode slurry. The slurry comprises a negative electrode active substance, a conductive agent, a binder, a plasticizer and a solvent. The above patent discloses the slurry formation with the plasticizer addition in the slurry to enhance the adhesivity.
[048] The present invention fixes the viscosity range of binder to get better rheology properties and wettability of the slurry. The contact angle of binder on the Al current collector helps in enhancement the adhesivity of slurry on the Al current collector that results in better electrochemical performance of electrode.
[049] Publication No. CN106654159 relates to a processing method and a product of a negative electrode material of a sodium ion battery, and belongs to the technical field of the sodium ion battery. This discloses the precondition process of the electrode.
[050] The present invention is based on the rheological behavior with the adhesivity as according to the contact angle of slurry on the current collector.
[051] Publication No. CN105449166 relates to a manufacturing method for a negative electrode pole piece for a sodium ion battery. This describes the method involves grinding the active material, vacuum drying, and coating a copper foil current collector with a slurry. The resulting pole piece exhibits high cycling stability and specific discharge capacity, making it economically beneficial for large-scale production.
[052] The present invention offers a distinct advantage by focusing on comprehensive optimizations of rheological properties, binder wettability, and other parameters specific to sodium-ion battery slurries. The use of aluminum foil as the current collector enhances homogeneity, adhesion, and coating properties, leading to improved electrochemical performance. This approach can potentially improve battery efficiency and enable cost-effective large-scale production.
[053] Publication No. US2023057606 relates to a negative electrode for a non-aqueous electrolyte secondary battery includes a negative electrode current collector, and a negative electrode mixture layer supported on the negative electrode current collector. This focuses on a negative electrode for a non-aqueous electrolyte secondary battery, utilizing flaky silicon particles and a binder containing a silicate. However, it does not address the rheological parameters, wettability, or adhesivity of the slurry.
[054] Present invention aims to optimize the viscosity of the binder to improve the rheological properties and wettability of the slurry. By considering these factors, we aim to enhance the overall performance, stability, and adhesivity of the negative electrode slurry in the battery.
[055] Publication No. US2023028284 provides a method for manufacturing a novel electrode. The method includes the steps of applying, to a current collector, a mixture comprising an active material conductive additive comprising a graphene compound, a binder, and a dispersion medium; performing a drying treatment on the mixture; performing a heat treatment on the mixture at a temperature higher than a temperature of the drying treatment; reducing the graphene compound in the mixture by a chemical reaction using a reducing agent; and performing a thermal reduction treatment on the mixture at a temperature higher than the temperature of the heat treatment. This describes a method for manufacturing a novel electrode, which includes applying a mixture comprising an active material, a conductive additive, a binder, and a dispersion medium onto a current collector. However, it does not discuss the rheological parameters, wettability, or adhesivity of the slurry.
[056] Present invention, focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, leading to improved adhesivity and stability of the electrode.
[057] Publication No. WO2023045125 relates to a negative electrode material and a preparation method therefor, and a sodium-ion battery. The negative electrode material comprises a transition metal sulfide, and nitrogen ions and selenium ions doped in the transition metal sulfide. The patent discloses a negative electrode material for a sodium-ion battery, comprising a transition metal sulfide doped with nitrogen and selenium ions. While it emphasizes the improvement in rate capability and cycling stability, it does not specifically address the rheological parameters or wettability of the slurry.
[058] Present invention focuses on optimizing the viscosity range of the binder to achieve better rheological properties and wettability, leading to improved adhesivity and stability of the negative electrode slurry in the battery.
[059] Publication No. US2022367857 relates to a negative electrode material preparation method thereof, and a lithium ion battery. This is a negative electrode material preparation method for a lithium-ion battery, comprising a first graphite core coated with a second graphite inner layer and an amorphous carbon outer layer. While it highlights the high capacity and power performance of the negative electrode material, it does not specifically discuss the rheological parameters or wettability of the slurry.
[060] Present invention focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, resulting in improved adhesivity and stability of the negative electrode slurry.
[061] Publication No. US2011111294 relates to high-capacity silicon-based anode active materials are described for lithium-ion batteries. This describes high-capacity silicon-based anode active materials for lithium-ion batteries, including composites with conductive coatings. While it explores the advantages of different carbon coatings, it does not specifically address the rheological parameters or wettability of the slurry.
[062] Present invention, focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, leading to improved adhesivity and stability of the negative electrode slurry in the battery.
[063] Publication No. WO2020103139 relates to a sodium ion battery negative electrode material that is rich in defects, a preparation method therefor and an application thereof, wherein the preparation method comprises the following steps: washing and drying a carbon-based material; adding defects at defect sites of the material by means of heating under a reducing atmosphere at 100-1200°C for 1-24 hours; then performing secondary sintering under an inert atmosphere at 1200-2500°C and maintaining the temperature for 0.5-48 hours to obtain a final product. This discusses a sodium-ion battery negative electrode material preparation method using a carbon-based material with added defects. While it emphasizes the improved rate performance and cycling stability, it does not specifically address the rheological parameters or wettability of the slurry.
[064] Present invention focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, aiming to enhance the adhesivity and stability of the negative electrode slurry.
[065] Publication No. WO2022063169 relates to a lithium-ion secondary battery negative electrode additive and a negative electrode slurry containing same, and a battery. The lithium-ion secondary battery negative electrode additive comprises a polyaspartic acid salt and water. This presents a lithium-ion secondary battery negative electrode additive comprising a polyaspartic acid salt and water, aiming to improve the electrochemical performance of the battery. However, it does not specifically discuss the rheological parameters or wettability of the slurry.
[066] Present invention focuses on optimizing the viscosity range of the binder to achieve better rheological properties and wettability, leading to improved adhesivity and stability of the negative electrode slurry.
[067] Publication No. EP3343679 relates to a sodium-ion secondary battery carbonaceous material with a low BET specific surface area. While it emphasizes high discharge capacity and excellent cycling characteristics, it does not specifically address the rheological parameters or wettability of the slurry.
[068] Present invention focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, aiming to enhance the adhesivity and stability of the negative electrode slurry.
[069] Publication No. EP3306710 relates to a negative electrode for a lithium-ion battery, comprising a carbon nanoribbon, a conductive agent, and a binder. While it highlights the composition of the negative electrode mixture layer, it does not specifically address the rheological parameters or wettability of the slurry.
[070] Present invention, however, focuses on optimizing the viscosity of the binder to achieve better rheological properties and wettability, leading to improved adhesivity and stability of the negative electrode slurry.
[071] Publication No. CN109742383 relates to a sodium-ion battery hard carbon anode material prepared from phenolic resin. While it emphasizes the high energy density and rate performance, it does not specifically address the rheological parameters or wettability of the slurry.
[072] Present invention focuses on optimizing the viscosity range of the binder to achieve better rheological properties and wettability, aiming to enhance the adhesivity and stability of the negative electrode slurry.
[073] The article entitled “A novel slurry concept for the fabrication of lithium-ion battery electrodes with beneficial properties.” By Boris Bitsch, Jens Dittmann, Marcel Schmitt, Philip Scharfer, WilhelmSchabel, Norbert Willenbacher; Journal of Power Sources Volume 265; 1 November 2014 talks about the rheological properties and adhesivity of slurry for the Li-ion battery. They have not measured the adhesivity on the current collector and our focus is on the how binder viscosity in particular can also give the better rheological parameters of the slurry with better adhesivity.
[074] The article entitled “Agitation effect on the rheological behavior of lithium-ion battery slurries” by Young Il Kwon, Jong Dae Kim & Young Seok Song; Journal of Electronic Materials volume 44, 475–481; 17 September 2014 talks about the rheological and morphological characteristics of a multicomponent slurry system consisting of an active material, conductive additive, and binder. The above article is the study of the Li-ion based cathode electrode for the battery whereas present invention claims the rheology and wettability of negative electrode slurry for Na-ion battery. There is not study on the contact angle and surface tension in the article.
[075] The article entitled “Rheology and structure of lithium-ion battery electrode slurries.” By Carl D. Reynolds, Sam D. Hare, Peter R. Slater, Mark J. H. Simmons, Emma Kendrick; Wiley Online Library; 25 August 2022 talks about the rheology of electrode slurries dictates the final coating microstructure. The above article is the study of the Li-ion based cathode electrode for the battery whereas we are claiming the rheology and wettability of negative electrode slurry for Na-ion battery. There is not study on the contact angle and surface tension in the article.
[076] In order to overcome above listed prior art, the present invention aims to provide an electrode slurry and electrode for a sodium (Na)-ion battery cell that achieves high energy density, high specific capacity with better cycle life. The invention provides a negative electrode slurry having improved dispersibility and adhesion property to strongly adhere the electrode active material with a current collector, thereby excellently maintaining electrode properties.
OBJECTS OF THE INVENTION:
[077] The principal object of the present invention is to provide a negative electrode slurry and negative electrode for sodium-ion batteries that utilizes the hard carbon that is synthesized from the agriculture waste like bagasse, rice straw.
[078] Another object of the present invention is to provide a negative electrode slurry having improved dispersibility and adhesion property to strongly adhere the electrode active material with a current collector, thereby excellently maintaining electrode properties.
[079] Yet another object of the present invention is to provide a sustainable approach to producing high-performance hard carbon-based negative electrode for the sodium-ion batteries using agricultural waste as a raw material.
[080] Still another object of the present invention is to provide anode fabrication in the production of high-performance sodium-ion batteries, offering a practical and cost-effective solution for energy storage.
SUMMARY OF THE INVENTION:
[081] The present invention relates to a negative electrode slurry and negative electrode for sodium-ion batteries that utilizes the hard carbon (HC) derived from bagasse as active material. The invention provides a method for preparing the negative electrode slurry by combining a clustered complex consisting of an active material (AM), a binder and a conductive material in the solvent like NMP, Deionized water. The improved and optimized rheology and adhesivity/wettability of the slurry, resulting in more uniform coating and better adhesion on the current collector. The adhesivity is enhanced and standardized based on the value of contact angle and surface tension. The adhesivity and rheology of slurry is controlled by the viscosity range of the prepared binder. The invention provides anode fabrication in the production of high-performance sodium-ion batteries, offering a practical and cost-effective solution for energy storage, especially the plateau capacity up to 0.2 V during charging, the charge-discharge efficiency and the capacity retention at normal temperatures. The disclosed method enables the large-scale production of efficient and reliable SIBs, which can significantly contribute to the advancement of sustainable energy solutions.
[082] A binder was prepared with precise control over its viscosity range to tune the rheological parameters for the negative electrode slurry. The adhesivity of the binder was modified based on the contact angle measurements on the current collector and surface tension analysis. The binder's properties were adjusted to achieve better adhesion or wettability of the slurry on the current collector made of aluminium foil.
[083] The binder properties resulted in the optimization of rheological parameters for the slurry. The shear viscosity range was carefully adjusted to prevent extreme shear thickening or shear thinning at a particular speed range during the coating process. The storage and loss moduli of the slurry were also optimized to promote a more homogeneous distribution of materials on the current collector.
[084] The improved adhesion or wettability of the slurry on the current collector, particularly aluminium foil, was achieved by measuring the contact angle of the slurry on the collector's surface. Surface tension analysis was conducted to assess the slurry's affinity for the current collector and make necessary adjustments to enhance adhesion.
[085] The range of tuned rheological and wettability parameters for the binder and slurry resulted in substantial improvements in the electrochemical performance of the negative electrode prepared for N-ion batteries such as better cycling stability, higher capacity retention of electrode.
[086] The wettability and adhesivity of coating, achieved through the optimized contact angle and surface tension, enhanced the overall mechanical stability of electrode.
BREIF DESCRIPTION OF THE INVENTION
[087] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
[088] Fig. 1 shows micrograph of the 80:10:10 ratio of A.M.: CMC: CA.
[089] Fig. 2 shows micrograph of the 90:02:08 ratio of A.M.: CMC: CA.
[090] Fig. 3 shows storage and loss modulus of the 92:02:08; A.M.: CMC: CA.
[091] Fig. 4 shows storage and loss modulus of the 80:10:10; A.M.: CMC: CA.
[092] Fig. 5 shows shear stress of the negative electrodes 92:02:08; A.M.: CMC: CA., 80:10:10; A.M.: CMC: CA.
[093] Fig. 6 shows shear viscosity of the negative electrodes 92:02:08; A.M.: CMC: CA., 80:10:10; A.M.: CMC: CA.
[094] Fig. 7 shows schematic diagram show the tangent and arc technique to measure contact angle of slurry comprising the 92:02:08; A.M.: CMC: CA.
[095] Fig. 8 shows surface tension of slurry comprising the 92:02:08; A.M.: CMC: CA.
[096] Fig. 9 shows schematic diagram show the tangent and arc technique to measure contact angle of slurry comprising the 80:10:10; A.M.: CMC: CA.
[097] Fig. 10 shows surface tension of slurry comprising the 80:10:10; A.M.: CMC: CA.
DETAILED DESCRIPTION OF THE INVENTION:
[098] The present invention is to provide a method for preparing the electrode active material slurry by varying the constituent ratios. The active material ratio ranges from 80% to 95%, while the additive ratio ranges from 0% to 15%, and the binder ratio ranges from 5% to 20%. The negative electrode active material is hard carbon. Additionally the binder is selected from one out of or group of any out of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymers, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, poly (vinylidene fluoride) -hexafluoropropene).
[099] The addition of conductive additives in varying percentage ranges to the negative electrode slurry increases its conducting properties as well as rheological parameters. The selection of the conductive additives is one or mixer out of the AC, SuperP, C45, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibers, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon. The negative electrode includes the slurry preparation process, characterization of the slurry, electrode construction, and performance evaluation of the high-capacity negative electrode. The present invention provides a negative electrode with highly optimized rheological parameters with wettability/adhesivity control, which is essential for producing a sodium ion battery of high energy density exhibiting excellent cycle characteristics and high-speed charging/discharging performance. The negative electrode slurry for a sodium battery produced by applying the above composition must satisfy specific rheological and physical properties, including shear stress, shear viscosity, and loss and storage moduli, within specified ranges. The adhesivity/wettability of the negative electrode slurry is optimized using the value of the contact angle of slurry on the surface of the current collector that is aluminum foil and surface tension using the sessile drop method. The surface tension is measured of pendent drop with 10ml volume. Thus, the invention provides the detailed process of developing the negative electrode slurry for the advance negative electrode for the modern sodium ion battery that have high specific capacity, energy density and longer life cycle. The below is the detailed process of developing the negative electrode for the sodium ion battery.
[100] The active material of negative electrode of the sodium ion battery is hard carbon whereas:
[101] The binder content is in the range of 5-20 wt.% based on the weight of the active material. The binder is selected from one out of or group of any out of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymers, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, poly (vinylidene fluoride) -hexafluoropropene).
[102] The selection of the conductive additives is one or mixer out of the AC, SuperP, C45, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon.
[103] The method for producing a composition for developing the negative electrode material for a lithium battery involves the content of active material in the negative electrode slurry must be in the range of 80 to 90%. The addition of the binder must be in the range of 5 to 20%, and The binder is selected from one out of or group of any out of following: styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymers, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, poly (vinylidene fluoride) -hexafluoropropene),. Additionally, the selection of the conductive additives is one or mixer out of the AC, SuperP, C45, graphite, expanded graphite, graphene, graphene nanoplatelets, carbon fibres, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon. The particle size or density of each conductive additive is specific to the additive. After adding the conductive additives, the mixture must be stirred for a specific time at a specific RPM in the range 300 to 2000 RPM. The optimal range of each parameter is crucial to ensure the best performance of the negative electrode material. The content of hard carbon in the negative electrode slurry affects the battery's capacity and cycle life. The addition of the binder is essential to enhance the mechanical strength and adhesion of the negative electrode slurry. The binder's density determines its ability to hold the particles together and its effect on the electrode's conductivity. The binder and conductive additives have crucial role in the formation of the slurry as they govern the rheological properties of the slurry. The shear viscosity, shear stress and loss, storage moduli are the rheological parameters which has been extensively optimized. The contact angle of the slurry is useful to understand the wettability of the slurry. It should be in the range of 50 to 80° on the aluminium foil. Moreover, the conductive additives are crucial in enhancing the electrode's electrical conductivity and improving the battery's performance.
[104] The characteristics of the slurry, including its rheological properties and wettability are important for determining the performance of the battery. Here are some common characteristics that are rheological properties and wettability of a typical slurry for the negative electrode of a Na-ion battery:
[105] The shear viscosity should be in the range 1 to 10 Pa.s. The loss modulus(G?) and storage modulus (G') are in the range 5 to 200 and 0.5 to 50 respectively at the shear rate of 102/s. The shear stress is optimized having the value of 50Pa to 300Pa with the shear rate of 102/s. The value of the contact angle is in the range 40 to 70º on the aluminum foil surface. The appropriate value of surface tension should be in the range 40 to 100mN/m.
[106] Preparation of Negative Electrode:
[107] The slurry formed of the with the content of active material in the range of 80 to 90%. The addition of the binder must be in the range of 5 to 20%, Additionally, the conductive additives must be added in the range of 0 to 15%.
[108] The preparation of the negative electrode follows the steps as given below:
[109] Coating of the slurry:
[110] A negative electrode for a sodium-ion battery can be prepared by applying the negative electrode slurry to a collector foil. This can be done using any known technique, such as doctor blading, bar coating, or a similar method. Various materials can be used as the collector for the sodium-ion battery, including copper foil, aluminum foil, stainless steel foil, nickel foil, titanium foil, alloys of these metals, or a carbon sheet. Aluminum foil is preferred due to its strength, electrochemical stability, and cost-effectiveness. The thickness of the collector foil used in the sodium-ion battery is not limited, but it should not be too thin as this could reduce the strength of the collector foil and cause problems with handling during application of the composition. Conversely, if the thickness is too large, it will increase the ratio by mass (or volume) of the collector foil to the components of the battery, reducing the energy density of the battery. In addition, to overcome the problem of the negative electrode hardening while processing that make it difficult to wind up, the thickness of the current collector foil is preferably between 12 to 25µm.
[111] Drying the coated negative electrode:
[112] Once the negative electrode material has been coated onto the current collector, it is generally in wet form or partial wet form containing the solvent and additives. Drying the negative electrode material serves several purposes, such as removing the solvent from the electrode, which leaves behind a solid and stable material. This is important to prevent the solvent from interfering with the electrochemical performance of the battery. Additionally, drying the negative electrode material enhances the adhesion of the active material and conductive additive to the current collector, which improves the stability and performance of the electrode. Furthermore, drying the negative electrode material improves the uniformity of the electrode structure. The drying of negative electrode is dried in the oven then subjected to a moulding process, the drying temperature range 80 to 180 degree C for the 10-12 hours.
[113] Calendaring of electrode:
[114] After drying process, the resulting electrode is moulded using a known technique such as calendaring to achieve the desired porosity, tortuosity, thickness and density. Porosity and tortuosity are both important factors to consider in the electrode after calendaring for optimal battery performance. But it is to take care the thickness of calendaring or applied pressure as the porosity of the electrode material sheet can be reduced, which can decrease the amount of available space for the electrolyte ions to interact with the active material, leading to a decrease in battery performance. However, a certain level of tortuosity can be beneficial in reducing electrode degradation and improving the overall cycling stability of the battery. Therefore, it is important to balance the porosity and tortuosity of the negative electrode after calendaring for optimal battery performance by carefully controlling the calendaring process parameters using the optimal value of the pressure or the thickness between the roller at a given 0.1 to 0.12mm at 100 to 200 RPM. There are no limitations on the thickness of the electrode, as it varies depending on the required properties. However, porosity of electrode after calendaring is generally regulated to between 30% to 50%.
[115] The performance of the negative electrode is given in the Table 1 with the various composition and examples.
[116] Table 1: Showing the all characteristics of the negative electrodes
Name of Characterizations 80:10:10;
HC: CMC: Super P 90:02:08;
HC: CMC: Super P
Rheology parameters at 102 s-1 of shear rate ? (Pa.s) 1.46 0.95
Shear stress (Pa) 145.95 101.74
G? (Pa) 7 24
G' (Pa) 1 6
Surface tension (mN/m) 48 to 55 65 to 70
Contact Angle 50 to 57º 60 to 70º
Porosity 35.89% 37.70%
Tortuosity 1.66 1.62

Storage Properties
Plateau Capacity
(Up to 0.2 V)
(Considering 1C= 250 mAh) Plateau Capacity
(Up to 0.2 V)
(Considering 1C= 250 mAh)
C/10 C/5 C/2 1C C/10 C/5 C/2 1C
216 214 209 203 210 210 206 203
Capacity Retention After 500th Cycles, at 1C= 174 mAh g-1 After 500th Cycles, at 1C= 160 mAh g-1
[117] The invention will be more fully understood from the following examples. These examples are to be constructed as illustrative of the invention and not limitative thereof:
[118] Example 1
[119] In this example, the negative electrode material of the Na -ion batteries was prepared with the following constituents:
[120] A mixture of active material that is hard carbon, binder, and additives was prepared using a mass ratio of 90:02:08. The hard carbon is synthesized from sugarcane bagasse, the hard carbon has particles distribution size nanometre ranging from 20 to 50nm with the tap density of 1.2 to 2.0 g/cm3 and specific surface area 2 to 5 m2/g. The binder was a Carboxymethyl cellulose (CMC) with a density of 1.69g/cm3 and the conductive additives included superP Carbon black (SuperP) having density of 0.16g/cc. The solid content was added to the Deionized water solvent to make a mixture. The mixture was then homogenized in a mixer for 20 to 60 minutes at the speed of 300 to 600 RPM to obtain a uniform mixture.
1. The FESEM micrograph of the negative electrode shows the homogenous distribution of the active material in the electrode complex with the binder CMC and conductive additive SuperP. The micrograph is shown in the Fig. 1.
2. The slurry has been optimized with the rheological properties. At the shear rate of 102 s-1, the shear viscosity of the slurry is 0.95 Pa.s, the shear stress 101.74Pa, whereas the storage and loss moduli have values 6 and 24 Pa respectively. Fig. 3 to 6 shows the rheological parameters.
3. The slurry has the contact angle of 60 to 70° measured on the surface of the aluminium foil, whereas the surface tension measured values is in the range 75 to 80mN/m. Fig. 7 to 8 show the wettability parameters like contact angle and surface tension.
4. The mixture was then coated onto an aluminium foil using a doctor blade with the speed of 0.016m/s and dried in a vacuum oven at 120°C for 10 to 12 hours to form a film of the negative electrode material on the aluminium based current collector. The thickness of the coated film was 30 to 35µm.
5. The coated electrode was further subjected to calendaring process at a temperature of 80°C to get the desired porosity and tortuosity. Calendaring was done at a speed of the 100 to 200 RPM with the 1000MPa stress.
6. The fabricated negative electrode has porosity found to be in the range 37.7% for varying thickness. Consequently, the tortuosity is in the range 1.62.
[121] The Table 1 shows the performance of the negative electrode with the 90:02:08 ratio of Hard Carbon: CMC: SuperP for the sodium batteries prepared in this example.
[122] The resulting negative electrode material was characterized for its morphological characteristics using field-emission scanning electron microscopy (FESEM) as shown Fig. 1. The FESEM images showed that the hard carbon particles were well-dispersed in the CMC binder and additive, with a uniform distribution. The rheology of the slurry is influenced by various factors, such as the particle size distribution, the binder concentration, and the mixing conditions. The particle size distribution of the hard carbon particles and the SuperP additive can affect the packing and flow behavior of the slurry. The binder concentration and type can affect the Shear Viscosity and adhesion properties of the slurry. The mixing conditions, such as the speed and duration of mixing, can affect the homogeneity and dispersion of the slurry. By optimizing the rheological properties of the slurry, it is possible to achieve a uniform and stable negative electrode material with good coating and calendaring behavior. The prepared slurry has such values of Shear Viscosity, modulus, shear stress and wettability, indicating good flowability, rheology and adhesion properties, that results highly enhanced electrochemical performances (shown in Table 1).
[123] Example 2
[124] In this example, a negative electrode material of the Na -ion batteries were prepared with the following constituents:
[125] A mixture of active material that hard carbon, binder, and additives was prepared using a mass ratio of 80:10:10. The hard carbon is synthesized from sugarcane bagasse, the hard carbon has particles distribution size nanometre ranging from 20 to 50nm with the tap density of 1.2 to 2.0 g/cm3 and specific surface area 2 to 5 m2/g. The binder was a Carboxymethyl cellulose (CMC) with a density of 1.69g/cm3 and the conductive additives included superP Carbon black (SuperP) having density of 0.16g/cc. The solid content with the amount was added to the deionized water solvent to make a mixture. The mixture was then homogenized in a mixer for 20 to 60 minutes at the speed of 300 to 600 RPM to obtain a uniform mixture.
[126] The FESEM micrograph of the negative electrode shows the homogenous distribution of the active material in the electrode complex with the binder CMC and conductive additive SuperP. The micrograph is shown in the Fig.2.
1. The slurry has been optimized with the rheological properties. At the shear rate of 102 s-1, the shear viscosity of the slurry is 1.46 Pa.s, the shear stress 145.94Pa, whereas the storage and loss moduli have values 1 and 7 Pa respectively. Fig. 3 to 6 shows the rheological parameters.
2. The slurry has the contact angle of 50 to 57° measured on the surface of the aluminium foil, whereas the surface tension measured values is in the range 58 to 65mN/m. Fig. 9 to 10 show the wettability parameters like contact angle and surface tension.
3. The mixture was then coated onto an aluminium foil using a doctor blade with the speed of 0.016m/s and dried in a vacuum oven at 80 to 135°C for 12 hours to form a film of the negative electrode material on the aluminium based current collector. The thickness of the coated film was 30 to 35µm.
4. The coated electrode was further subjected to calendaring process at a temperature of 80 to 120°C to get the desired porosity and tortuosity. Calendaring was done at a speed of the 100 to 200 RPM with the 1000MPa stress.
5. The fabricated negative electrode has porosity found to be in the range 35.89% for varying thickness. Consequently, the tortuosity is in the range 1.66.
[127] The Table 1 shows the performance of the negative electrode with the 90:02:08 ratio of Hard Carbon: CMC: SuperP for the sodium batteries prepared in this example. The resulting negative electrode material was characterized for its morphological characteristics using field-emission scanning electron microscopy (FESEM) as shown in Fig.2. The FESEM images showed that the hard carbon particles were well-dispersed in the CMC binder and additive, with a uniform distribution. The rheology of the slurry is influenced by various factors, such as the particle size distribution, the binder concentration, and the mixing conditions. The particle size distribution of the hard carbon particles and the conductive additive SuperP can affect the packing and flow behavior of the slurry. The binder concentration and type can affect the viscosity and adhesion properties of the slurry. The mixing conditions, such as the speed and duration of mixing, can affect the homogeneity and dispersion of the slurry. By optimizing the rheological properties of the slurry, it is possible to achieve a uniform and stable negative electrode material with good coating and calendaring behavior. The prepared slurry has such values of shear viscosity, modulus, shear stress and wettability, indicating good mechanical stability, rheology and adhesion properties.
[128] Thus, the method is provided for preparing a hard carbon-based slurry for negative electrode coated on the aluminum based current collector with good dispersion, mechanical stability, and adhesion properties optimized as rheological properties, which are important for the performance and longevity of battery systems. The rheological measurements and FESEM provides valuable insights into the rheological properties of the slurry and morphological of electrode respectively, which can inform the design and optimization of future battery systems.
[129] Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.
, C , Claims:WE CLAIM
1. A method for preparing a negative electrode slurry and negative electrode for sodium-ion batteries that utilizes the hard carbon (HC) derived from cattle manure, rice straw, bagasse as active material includes following steps:
a) Applying the negative electrode slurry to a current collector characterized in that the negative electrode slurry is coated onto a current collector made of copper, Aluminium, mixture of both (Cu/Al) with a coating thickness in the range = 10 to = 300 µm. Further, a coating weight of the active material can be about 0.1 to 20 mg/cm2.
b) Drying the negative electrode at a temperature range of 80 to 180º C for = 2 to = 12 hours.
c) Controlling the calendaring process parameters with an optimal value of pressure of = 0.5 MPa to = 1500 MPa, thickness between the roller at 0.05 to 0.3 mm, and a roller speed in between 100 to 200 RPM.
2. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the hard carbon has distribution size ranging from 20 to 100 nm, tap density of 1.0 to 5.0 g/cm3, and specific surface area of 2 to 10 m2/g.
3. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the binder is selected from a group including styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene/propylene copolymers, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, fluorinated polymer, chlorinated polymer, and polyvinylidene fluoride-hexafluoropropene.
4. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the conductive additive is selected from a group including AC, SuperP, C45, graphite, expanded graphite, graphene nanoplatelets, carbon fibers, carbon nano-fibers, graphitized carbon flake, carbon tubes, carbon nanotubes, activated carbon, and mesoporous carbon.
5. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the solvent is selected from a group including deionized water, NMP, and alcohol-based solvents.
6. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the electrode slurry is formed with the content of active material in the range of 80 to 98%, binder in the range of 2 to 20%, and conductive additives in the range of 0 to 15%.
7. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein at a shear rate in the range of 0.1 to 103 s-1, the shear viscosity of the slurry is in the range of 1.0 to 10 Pa.s, shear stress in the range of =100 to = 300 Pa, storage modulus in the range of = 0.5 to = 50 Pa, loss modulus in the range of = 5 to = 200 Pa.
8. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the negative electrode slurry has a binder solution viscosity in the range of = 500 to = 2000 mPas, which is controlled by the binder material and solvent selection and/or weight percentage ratio of binder material to solvent.
9. The method for preparing the electrode active material slurry, as claimed in claim 1, wherein the negative electrode slurry exhibits a contact angle in the range of = 40 to = 70° on the surface of the current collector made of copper, Aluminium, mixture of both (Cu/Al) and a surface tension in the range of = 40 to = 100 mN/m.
10. The method for preparing the electrode active material slurry, as claimed in claim 10, wherein negative electrode has a porosity in the range of 30 to 55% and a tortuosity in the range of 1.34 to 1.82 enabling efficient transport of Na-ions and electrolyte within the electrode.
11. The method for preparing the electrode active material slurry, as claimed in claim 11, wherein the rheological property, enabling the efficient transport of Na-ions within the electrode, results in a high plateau capacity value in the range 200 mAh g-1 to 300 mAh g-1 (up to 0.2 V) during charging at 0.2C, 0.5C, 1C, 2C, 5C, 10C wherein 1C=250 mAh along with good cycling stability in Na-ion battery cells.