Description:FIELD
The present disclosure relates to the field of batteries. Particularly, the present disclosure relates to a positive electrode slurry composition and a process for the preparation of a positive electrode.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used, indicate otherwise.
Conductivity: The term “conductivity” refers to ability of an electrode to conduct electricity. High conductivity means a material allows electrical current to flow easily.
Current collector: The term “current collector” refers to a conductive material that bridges the flow of electrons between the active electrode materials and the external circuit.
Flexibility: The term ‘flexibility” refers to ability of an electrode to bend, fold, or stretch without losing its conductive properties or structural integrity.
Loss modulus: The term “loss modulus” denoted as G″, measures the amount of energy dissipated as heat during deformation, which is not recoverable. The loss modulus represents the viscous or liquid-like behaviour of a viscoelastic material.
Peel strength: The term “peel strength” refers to a resistance of the electrode adhesion to the current collector. It essentially measures how much force is needed to separate the electrode material (active material and binder) from the underlying current collector.
Percentage retention: The term “retention percentage” refers to ability of an electrode to retain its initial capacity or performance over time, specifically during extended use or cycling or elevated current rate. It is a measure of how well an electrode maintains its functionality as it is charged and discharged repeatedly.
Resistance: The term “resistance” refers to the opposition an electrode presents to the flow of electric current.
Storage modulus: The term “storage modulus” denoted as G’ measures the amount of energy stored in the material during deformation, which is recoverable when the stress is removed. The storage modulus represents the elastic or solid-like behaviour of a viscoelastic material.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
In the electrode coating industry, a higher solid content in slurry is preferred as it minimizes solvent usage, increases mass loading, and enables faster coating speeds, ultimately reducing drying time and overall energy consumption. However, excessively high solid content limits solvent availability, leading to increased viscosity, which makes it challenging to achieve a homogeneous slurry and complicates the coating process. Maintaining a proper balance between solid content and viscosity is crucial to ensuring a well-mixed slurry suitable for efficient coating. To achieve a slurry that is both process-friendly and well-dispersed in terms of its components while maintaining the required viscosity for the coating process, without compromising electrode properties, is a challenging task.
There is, therefore, felt a need to develop a positive electrode slurry composition that can mitigate the drawbacks mentioned herein above or at least provide a useful alternative.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure is to ameliorate one or more problems given in the background or to at least provide a useful alternative.
Another object of the present disclosure is to provide a positive electrode slurry composition.
Still another object of the present disclosure is to provide a positive electrode slurry composition that can accommodate high solid content without compromising the desired rheological properties.
Yet another object of the present disclosure is to provide a positive electrode slurry composition that has improved loading capacity and can be coated to higher thickness.
Still another object of the present disclosure is to provide a positive electrode slurry that has improved storage modulus.
Yet another object of the present disclosure is to provide a process for the preparation of a positive electrode.
Still another object of the present disclosure is to provide a process for the preparation of a positive electrode that is simple, economical and scalable.
Yet another object of the present disclosure is to provide a positive electrode.
Still another object of the present disclosure is to provide a positive electrode that has improved peel strength, flexibility and conductivity.
Yet another object of the present disclosure is to provide a positive electrode that has improved capacity retention at high current rates.
Still another object of the present disclosure is to provide a positive electrode that has better life cycle retention.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In an aspect, the present disclosure provides a positive electrode slurry composition. The positive electrode slurry composition comprising:
• an active material;
• a conductive agent;
• multi-walled carbon nanotubes (MWCNT);
• a binder solution; and
• a binder additive solution;
wherein a mass ratio of the binder additive solution to the binder solution is in the range of 1:2 to 1:5.
In accordance with the present disclosure, the slurry composition is characterized by having at least one of the following:
• solid content in the range of 65% to 80%;
• viscosity in the range of 1000 cP to 4500 cP;
• storage modulus (G’) in the range of 950 Pa to 1400 Pa at a frequency in the range of 45 Hz to 110 Hz;
• loss modulus (G”) in the range of 720 Pa to 1000 Pa at a frequency in the range of 45 Hz to 110 Hz;
• storage modulus (G’) in the range of 150 Pa to 250 Pa at a strain percent in the range of 2 to 12;
• loss modulus (G”) in the range of 170 Pa to 200 Pa at a strain percent in the range of 2 to 12; and
• loading capacity in the range of 15 mg/cm2 to 25 mg/cm2 per side of an electrode.
In accordance with the present disclosure,
• the active material is present in an amount in the range of 96 mass% to 98 mass% with respect to the total amount of the slurry composition;
• the conductive agent is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of the slurry composition;
• the multi-walled carbon nanotubes (MWCNT) is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of the slurry composition;
• the binder is present in an amount in the range of 0.7 mass% to 1.5 mass% with respect to the total amount of the slurry composition; and
• the binder additive is present in an amount in the range of 0.2 mass% to 0.35 mass% with respect to the total amount of the slurry composition.
In accordance with the present disclosure, the active material is selected from the group consisting of nickel manganese cobalt (NMC) compound, lithium cobalt oxide, lithium and manganese rich (LMR) nickel manganese cobalt compound and nickel cobalt aluminium (NCA).
In accordance with the present disclosure, the conductive agent is selected from the group consisting of carbon black powder, acetylene black and graphene.
In accordance with the present disclosure, the binder solution is selected from the group consisting of polyvinylidene fluoride (PVDF) solution, polyimide solution, polyacrylonitrile solution, and polyamide-imide solution.
In accordance with the present disclosure, the binder additive solution is selected from the group consisting of terpolymer of vinylidene fluoride (VDF) solution, copolymer of vinylidene fluoride and hexafluoropropylene (VDF-HFP) solution, copolymer of vinylidene fluoride and trifluoroethylene (VDF-TrFE) solution and polyaniline solution.
In another aspect, the present disclosure provides a process for the preparation of a positive electrode. The process comprising the following steps:
i) sequentially mixing predetermined amounts of a binder solution, a binder additive solution, a multi-walled carbon nanotubes (MWCNT), first portions of a conductive agent and an active material under stirring followed by adding second portions of said conductive agent and said active material to obtain a slurry composition;
ii) coating the slurry composition on a current collector at a predetermined thickness to obtain a coated electrode;
iii) drying the coated electrode at a predetermined temperature for a predetermined time period to obtain a dried electrode; and
iv) calendaring the dried electrode to a predetermined density to obtain the positive electrode.
In accordance with the present disclosure, a mass ratio of the binder additive solution to the binder solution is in the range of 1:2 to 1:5.
In accordance with the present disclosure,
• the predetermined amount of the active material is in the range of 96 mass% to 98 mass% with respect to the total mass of the slurry composition;
• the predetermined amount of the conductive agent is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of the slurry composition;
• the predetermined amount of the multi-walled carbon nanotubes (MWCNT) is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of the slurry composition;
• the predetermined amount of the binder solution is in the range of 0.7 mass% to 1.5 mass% with respect to the total mass of the slurry composition; and
• the predetermined amount of the binder additive solution is in the range of 0.2 mass% to 0.35 mass% with respect to the total mass of the slurry composition.
In accordance with the present disclosure, the binder additive solution has a solid content in the range of 6% to 9%; and the binder solution has a solid content in the range of 6% to 9%.
In accordance with the present disclosure, the stirring is carried out at a speed in the range of 1500 rpm to 2500 rpm, and the stirring is carried out at a time period in the range of 1 hour to 3 hours.
In accordance with the present disclosure, the predetermined thickness is in the range of 50 microns to 160 microns
In accordance with the present disclosure, the predetermined temperature is in the range of 90 oC to 110 oC, the predetermined time period is in the range of 4 hours to 8 hours, and the predetermined density is in the range of 2 g/cc to 5 g/cc.
A positive electrode obtained by using the process of the present disclosure is characterized by having at least one of the following:
• peel strength in the range of 3 N/mm to 4 N/mm;
• conductivity in the range of 2 ohm-1 to 8 ohm-1;
• percentage capacity retention in the range of 85% to 95% at a current-rate in the range of 1C to 3C;
• percentage capacity retention in the range of 98% to 99% when used for up to 50 cycles;
• thickness in the range of 35 microns to 100 microns; and
• density in the range of 2 g/cc to 5 g/cc.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Fig. 1a illustrates a graph of peel strength vs total binder content of the slurry compositions with and without binder additive (VDF), and having 70% solid content;
Fig. 1b illustrates a graph of resistance vs total binder content of the slurry composition with and without binder additive (VDF), and having 70% solid content;
Fig. 1c illustrates a graph of viscosity vs total binder content of the slurry composition with and without binder additive (VDF), and having 70% solid content;
Fig. 2a illustrates a comparative bar graph of resistance and peel strength of the electrodes prepared by using the slurry compositions with and without binder additive (VDF), and having 70% and 76% solid content;
Fig. 2b illustrates a comparative bar graph of viscosity of the slurry compositions with and without binder additive (VDF), and having 70% and 76% solid content;
Fig. 2c illustrates an electrode prepared by using a slurry composition without binder additive (VDF);
Fig. 2d illustrates an electrode prepared by using a slurry composition with binder additive (VDF);
Fig. 3a illustrates a graph of storage modulus G’ and loss modulus G” vs frequency for the slurry composition with binder additive in accordance with the present disclosure;
Fig. 3b illustrates a graph of storage modulus G’ and loss modulus G” vs frequency for the slurry composition without binder additive (VDF);
Fig. 3c illustrates a graph of storage modulus G’ and loss modulus G” vs strain percentage for the slurry composition with binder additive in accordance with the present disclosure;
Fig. 3d illustrates a graph of storage modulus G’ and loss modulus G” vs strain percentage for the slurry composition without binder additive (VDF);
Fig. 4a illustrates a comparative graph of retention percentage vs current rate of the electrodes prepared by using the slurry compositions with and without VDF; and
Fig. 4b illustrates a comparative graph of retention percentage vs current rate of the electrodes prepared by using the slurry compositions with and without VDF.
DETAILED DESCRIPTION
The present disclosure relates to a positive electrode slurry composition, a process for the preparation of positive electrode and a positive electrode.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc. when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
In the electrode coating industry, a higher solid content in slurry is preferred as it minimizes solvent usage, increases mass loading, and enables faster coating speeds, ultimately reducing drying time and overall energy consumption. However, excessively high solid content limits solvent availability, leading to increased viscosity, which makes it challenging to achieve a homogeneous slurry and complicates the coating process. Maintaining a proper balance between solid content and viscosity is crucial to ensuring a well-mixed slurry suitable for efficient coating.
To achieve a slurry that is both process-friendly and well-dispersed in terms of its components while maintaining the required viscosity for the coating process, without compromising electrode properties, is a challenging task.
In an aspect, the present disclosure provides a positive electrode slurry composition. The positive electrode slurry composition comprises an active material, a conductive agent, multi-walled carbon nanotubes (MWCNT), a binder solution, and binder additive solution.
In accordance with the present disclosure, a mass ratio of the binder additive solution to the binder solution is in the range of 1:2 to 1:5. In an exemplary embodiment, a mass ratio of the binder additive solution to the binder solution is 1:3. In another exemplary embodiment, a mass ratio of the binder additive solution to the binder solution is 1:4.
The selected mass ratio of the binder additive solution to the binder solution has improved the properties of the slurry composition of the present disclosure by allowing to accommodate higher solid content without compromising the desired properties such as viscosity, loading capacity and the like.
In accordance with the present disclosure, the active material is selected from the group consisting of nickel manganese cobalt (NMC) compound, lithium cobalt oxide, lithium and manganese (LMR) rich nickel manganese cobalt compound and nickel cobalt aluminium (NCA). In an exemplary embodiment, the active material is nickel manganese cobalt (NMC). Nickel manganese cobalt (NMC) compound is an active material of used in a battery. NMC compound has a high energy density, good rate capability and stability making it suitable for applications like electric vehicles and consumer electronics.
In accordance with the present disclosure, the active material is present in an amount in the range of 96 mass% to 98 mass% with respect to the total amount of the slurry composition. In an exemplary embodiment, the active material is present in an amount of 97% with respect to the total amount of the slurry composition.
In accordance with the present disclosure, the conductive agent is selected from the group consisting of carbon black powder, acetylene black and graphene. In an embodiment, the carbon black powder is selected from the group consisting of Super PTM, C65TM, Ketjen black, and KS6LTM. In an exemplary embodiment, the conductive agent is Super PTM.
In accordance with the present disclosure, the conductive agent is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of the slurry composition. In an exemplary embodiment, the conductive agent is present in an amount of 0.75 mass% with respect to the total amount of the slurry composition.
MWCNT are the multi-walled tubular structures made of carbon atoms arranged in a hexagonal lattice, with multiple layers of graphene sheets nested within each other. MWCNTs are known for their exceptional strength, flexibility, electrical and thermal conductivity, and are used in various applications, including reinforcing composite materials and as conductive and heat-dissipating materials.
In accordance with the present disclosure, the multi-walled carbon nanotubes (MWCNT) is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of the slurry composition. In an exemplary embodiment, the multi-walled carbon nanotubes (MWCNT) is present in an amount of 0.75 mass% with respect to the total amount of the slurry composition.
In accordance with the present disclosure, the binder solution is selected from the group consisting of polyvinylidene fluoride (PVDF) solution, polyimide solution, polyacrylonitrile solution and polyamide-imide solution.
In accordance with the present disclosure, the binder solution is present in an amount in the range of 0.7 mass% to 1.5 mass% with respect to the total amount of the slurry composition. In an exemplary embodiment, the binder solution is present in an amount of 1.2 mass% with respect to the total amount of the slurry composition. In another exemplary embodiment, the binder solution is present in an amount of 0.9 mass% with respect to the total amount of the slurry composition.
In accordance with the present disclosure, the binder additive solution is selected from the group consisting of a terpolymer of vinylidene fluoride (VDF) solution, copolymer of vinylidene fluoride and hexafluoropropylene (VDF-HFP) solution, copolymer of vinylidene fluoride and trifluoroethylene (VDF-TrFE) solution and polyaniline solution. In an exemplary embodiment, the binder additive solution is a terpolymer of vinylidene fluoride (VDF), which is a tertiary polymer of vinylidene fluoride, tetrafluroethylene and hexafluoropropylene (VDF-TFE-HFP).
In accordance with the present disclosure, the binder additive solution is present in an amount in the range of 0.2 mass% to 0.35 mass% with respect to the total amount of the slurry composition. In an exemplary embodiment, the binder additive solution is present in an amount of 0.3 mass% with respect to the total amount of the slurry composition.
The binder additive solution is used in the slurry composition of the present disclosure to control the viscosity of the slurry and to obtain the better rheological property for coating.
In accordance with the present disclosure, the slurry composition is characterized by having at least one of the following: solid content in the range of 65% to 80%; viscosity in the range of 1000 cP to 4500 cP; storage modulus (G’) in the range of 950 Pa to 1400 Pa at a frequency in the range of 45 Hz to 110 Hz; loss modulus (G”) in the range of 720 Pa to 1000 Pa at a frequency in the range of 45 Hz to 110 Hz; storage modulus (G’) in the range of 150 Pa to 250 Pa at a strain percent in the range of 2 to 12; loss modulus (G”) in the range of 170 Pa to 200 Pa at a strain percent in the range of 2 to 12, and loading capacity in the range of 20 mg/cm2 to 45 mg/cm2 per side of an electrode.
In an exemplary embodiment, the slurry composition is characterized by having: solid content of 76%, viscosity of 4346 cP, storage modulus (G’) of 983 Pa at 50 Hz frequency and 1320 Pa at 100 Hz frequency, loss modulus (G”) of 731.6 Pa at 50 Hz frequency and 956.2 Pa at 100 Hz frequency, storage modulus (G’) of 224 Pa at 5% strain and 167 Pa at 10% strain, loss modulus (G”) of 195.9 Pa at 5% strain, and 174.1 Pa at 10% strain, and loading capacity of 22 mg/cm2 per side of the electrode. In another exemplary embodiment, the slurry composition is characterized by having: solid content of 70%, viscosity of 2462 cP, and loading capacity of 19 mg/cm2 per side of the electrode.
The slurry composition of the present disclosure has improved the solid content of up to 76% and has improved the mass loading during coating up to 44 g/cm2 on both sides.
In another aspect, the present disclosure provides a process for the preparation of a positive electrode. The process for the preparation of the positive electrode is provided in detail below:
Predetermined amounts of a binder solution, a binder additive solution, a multi-walled carbon nanotubes (MWCNT), first portions of a conductive agent and an active material are mixed sequentially under stirring followed by adding second portions of the conductive agent and the active material to obtain a slurry composition.
In accordance with the present disclosure, the predetermined amount of the binder solution is in the range of 0.7 mass% to 1.5 mass% with respect to the total mass of the slurry composition. In an exemplary embodiment, the predetermined amount of the binder solution is 1.2 mass% with respect to the total mass of the slurry composition.
In accordance with the present disclosure, the binder solution is selected from the group consisting of polyvinylidene fluoride (PVDF) solution, polyvinylpyrrolidone (PVP) solution, polyimide solution, polyacrylonitrile solution and polyamide-imide solution. In an exemplary embodiment, the binder solution is polyvinylidene fluoride (PVDF) solution.
In accordance with the present disclosure, the binder additive solution is selected from the group consisting of a terpolymer of vinylidene fluoride (VDF) solution, copolymer of vinylidene fluoride and hexafluoropropylene (VDF-HFP) solution, copolymer of vinylidene fluoride and trifluoroethylene (VDF-TrFE) solution and polyaniline solution. In an exemplary embodiment, the binder additive solution is terpolymer of vinylidene fluoride (VDF), which is a tertiary polymer of vinylidene fluoride, tetrafluroethylene and hexafluoropropylene (VDF-TFE-HFP) solution.
In accordance with the present disclosure, the predetermined amount of the binder additive solution is in the range of 0.2 mass% to 0.35 mass% with respect to the total mass of the slurry composition. In an exemplary embodiment, the predetermined amount of the binder additive solution is 0.3 mass% with respect to the total mass of the slurry composition.
In accordance with the present disclosure, a mass ratio of the binder additive solution to the binder solution is in the range of 1:2 to 1:5. In an exemplary embodiment, a mass ratio of the binder additive solution to the binder solution is 1:3. In another exemplary embodiment, a mass ratio of the binder additive solution to the binder solution is 1:4.
The mass ratio of the binder additive to the binder in the slurry composition of the present disclosure can regulate viscosity while maximizing the solid content, allow increased mass loading without compromising essential electrode properties such as peel strength, electrical resistance, mechanical flexibility, particularly in thicker electrodes. The slurry composition of the present disclosure can enhance the overall performance and manufacturability of the coated electrodes.
In accordance with the present disclosure, the binder additive solution has a solid content in the range of 6% to 9%; and the binder solution has a solid content in the range of 6% to 9%. In an exemplary embodiment, the binder additive solution has a solid content in the range of 7.8%; and the binder solution has a solid content in the range of 7.8%.
In accordance with the present disclosure, the binder additive solution is prepared by mixing a binder additive in a fluid medium under stirring at a speed in the range of 400 rpm to 600 rpm for a time period in the range of 10 minutes to 20 minutes.
In accordance with the present disclosure, the binder solution is prepared by mixing a binder in a fluid medium under stirring at a speed in the range of 400 rpm to 600 rpm for a time period in the range of 10 minutes to 20 minutes.
In accordance with the present disclosure, the fluid medium is selected from the group consisting of N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO) and dimethylformamide (DMF). In an exemplary embodiment, the fluid medium is N-methyl pyrrolidone (NMP).
In accordance with the present disclosure, the predetermined amount of the multi-walled carbon nanotubes (MWCNT) is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of the slurry composition. In an exemplary embodiment, the predetermined amount of the multi-walled carbon nanotubes (MWCNT) is 0.75 mass% with respect to the total mass of the slurry composition.
In an embodiment, the multi-walled carbon nanotubes (MWCNT) are in solid powder form or in a dispersion form for enhanced mixing.
In accordance with the present disclosure, the conductive agent is selected from the group consisting of carbon black powder, acetylene black and graphene. In an embodiment, the carbon black powder is selected from the group consisting of super PTM, C65TM, Ketjen black, and KS6LTM. In an exemplary embodiment, the conductive agent is Super PTM.
In an embodiment, the process comprising split addition of the conductive carbon, wherein the first portion of the conductive agent is 50% of the total amount of the conductive agent, and the second portion of the conductive agent is the remaining 50% of the total amount of the conductive agent.
In accordance with the present disclosure, the total amount of the conductive agent is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of the slurry composition. In an exemplary embodiment, the total amount of the conductive agent is 0.75 mass% with respect to the total mass of the slurry composition.
In accordance with the present disclosure, the active material is selected from the group consisting of nickel manganese cobalt (NMC) compound, lithium cobalt oxide, lithium and manganese rich (LMR) nickel manganese cobalt compound and nickel cobalt aluminium (NCA). In an exemplary embodiment, the active material is nickel manganese cobalt (NMC) compound.
In an embodiment, the first portion of the active material is 50% of the total amount of the active material, and the second portion of the active material is the remaining 50% of the total amount of the active material.
In accordance with the present disclosure, the total amount of the active material is in the range of 96 mass% to 98 mass% with respect to the total mass of the slurry composition. In an exemplary embodiment, the total amount of the active material is 97 mass% with respect to the total mass of the slurry.
In accordance with the present disclosure, the stirring is carried out at a speed in the range of 1500 rpm to 2500 rpm. In an exemplary embodiment, the stirring is carried out at 2000 rpm.
In accordance with the present disclosure, the stirring is carried out for a time period in the range of 1 hour to 3 hours. In an exemplary embodiment, the stirring is carried out for 2 hours.
The slurry composition is coated on a current collector having a predetermined thickness to obtain a coated electrode.
In accordance with the present disclosure, the coating is performed by a method selected from doctor blade coating, slot die and spray coating. In an exemplary embodiment, the coating is performed by using a doctor blade.
In accordance with the present disclosure, the predetermined thickness is in the range of 50 microns to 160 microns. In an exemplary embodiment, the predetermined thickness is 99 microns.
The coated electrode is dried at a predetermined temperature for a predetermined time period to obtain a dried electrode.
In accordance with the present disclosure, drying is performed by a method selected from hot air drying and vacuum drying. In an exemplary embodiment, drying is performed by hot air drying.
In accordance with the present disclosure, the predetermined temperature is in the range of 90oC to 110oC. In an exemplary embodiment, the predetermined temperature is 100oC.
In accordance with the present disclosure, the predetermined time period is in the range of 4 hours to 8 hours. In an exemplary embodiment, the predetermined time period is 6 hours.
The dried electrode is calendared to a predetermined density to obtain the positive electrode.
In accordance with the present disclosure, the predetermined density is in the range of 2 g/cc to 5 g/cc. In an exemplary embodiment, the predetermined density is 3.6 g/cc.
The process for the preparation of a positive electrode is simple, economical and scalable.
In accordance with the present disclosure, a positive electrode is obtained by using the process of the present disclosure. The positive electrode is characterized by having at least one of the following: peel strength in the range of 3 N/mm to 4 N/mm, conductivity in the range of 4 ohm-1 to 8 ohm-1, percentage capacity retention in the range of 85% to 95% at a current-rate in the range of 1C to 3C, percentage capacity retention in the range of 98% to 99% when used for up to 50 cycles, thickness in the range of 35 microns to 100 microns, and density in the range of 2 g/cc to 5 g/cc.
In an exemplary embodiment, the positive electrode is characterized by having peel strength of 3.8 N/mm, conductivity of 4.2 ohm-1, percentage capacity retention of 92.56 % at a current-rate of 1C and 86.75% at a current rate of 3C, percentage capacity retention of 98.75% when used for up to 50 cycles, thickness of 72 microns, and density of 3.6 g/cc.
In another exemplary embodiment, the positive electrode is characterized by having peel strength of 3.3 N/mm, conductivity of 7.7 ohm-1, thickness of 72 microns, and density of 3.6 g/cc.
The positive electrode in accordance with the present disclosure has improved peel strength, flexibility and conductivity.
The positive electrode slurry composition in accordance with the present disclosure has improved storage modulus.
The positive electrode in accordance with the present disclosure has improved capacity retention at high current rates.
The positive electrode in accordance with the present disclosure has better life cycle retention.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purposes only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: Process for the preparation of a positive electrode in accordance with the present disclosure

Example 1
Preparation of positive electrode slurry composition
The binder solution with 7.8% solid content was prepared by adding polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone under mixing at 500 rpm for 12 hours. A binder additive solution with 7.8% solid content was prepared by adding terpolymer of vinylidene fluoride (VDF) under mixing at 500 rpm for 12 hours.
To prepare the slurry composition, the following ingredients were mixed stepwise and were stirred at 2000 rpm for 15 minutes after each addition. The amounts of each of the ingredient is provided in Table 1.
Initially, the polyvinylidene fluoride (PVDF) binder solution and the terpolymer of vinylidene fluoride (VDF) binder additive solution were mixed at 2000 rpm for 15 minutes to obtain a binder mixture. Then, multi-walled carbon nanotubes (MWCNT) were added followed by adding first portions of (50% amount) carbon black (Super PTM), and nickel manganese cobalt (NMC) compound to the binder mixture sequentially under stirring at 2000 rpm for 15 minutes for each addition, which was followed by mixing sequentially the second portions of (remaining 50% amount) of SuperPTM and NMC under mixing at 2000 rpm for 15 minutes each for each addition to obtain the slurry composition.
The slurry compositions were so prepared to obtain the solid content of 70%.
Examples 2 to 4:
Example 5 was prepared by using the similar procedure as provided in Example 1 except by varying the amount of ingredients to achieve the 70% solid content in the slurry composition.
Example 5:
Example 5 was prepared by using the similar procedure as provided in Example 2 except that the solid content of 76% was used instead of 70% solid content in the slurry composition.
The viscosity of these slurry compositions were determined, and the values are provided in Table 1.
Table 1: Positive electrode slurry compositions in accordance with the present disclosure
Example No. Slurry composition (wt. %) Measurements
NMC
(%) SuperP
(%) MWCNT
(%) PVDF
(%) VDF
(%) Solid content
(%) Viscosity
(cP) Peel strength
(25 N/mm) Resistance
(ohm)
Example 1 96.8 0.75 0.75 1.5 0.2 70 3456 3.57 0.24
Example 2 97 0.75 0.75 1.2 0.3 70 2462 3.32 0.13
Example 3 97.3 0.75 0.75 0.9 0.3 70 1423 3.08 0.14
Example 4 97.6 0.75 0.75 0.6 0.3 70 1351 1.93 0.13
Example 5 97 0.75 0.75 1.2 0.3 76 4346 3.8 0.24

Preparation of the positive electrodes by using the slurry composition
The slurry compositions so obtained were coated on a current collector by using a doctor’s blade to a thickness of 99 microns to obtain a coated electrode. The coated electrode was dried at 100 oC for 6 hours to obtain a dried electrode. The dried electrode was then processed by calendaring to 3.6 g/cc density to obtain the positive electrode. The so obtained positive electrode had thickness of 72 mm.
The so obtained positive electrode were characterized for peel strength and resistance and the values are provided in Table 1. For measuring peel strength of the positive electrode prepared by using the slurry composition 25 mm sample was used.
Experiment 2: Experiments for initial optimizing the slurry composition (comparative examples)
Initial experiments were performed by changing the solid content of a slurry composition without binder additive solution. The slurry compositions were prepared by mixing 97% nickel manganese cobalt (NMC) compound, 0.75% carbon black (Super P) (CB), 0.75% carbon nanotubes (CNT), and 1.5% Polyvinylidene Fluoride (PVDF) binder solution. Table 2 illustrates the comparative slurry compositions with variable solid content, and the properties of the electrode so obtained.
Table 2: Comparative slurry compositions with variable solid contents
Example no. Active
Material
(NMC)
(%) Carbon Black (CB)
(%) Carbon Nanotubes (MWCNT)
(%) Binder
(PVDF)
(%) Solid
Content (%) Viscosity
(cP) Peel Strength
25 N/mm Resistance
(ohm) Conductivity
(1/ohm)
Comparative Example 1 97 0.75 0.75 1.5 65 1972 2.6 0.13 7.7
Comparative Example 2 97 0.75 0.75 1.5 70 3417 3.4 0.19 5.3
Comparative Example 3 97 0.75 0.75 1.5 76 6574 2.4 0.38 2.6

It can be observed from Table 2 that with increasing the solid content in the slurry composition to 76%, while keeping the amounts of other ingredients unchanged, led to increased viscosity of the slurry composition, and the electrode so prepared by using these slurry compositions showed higher resistance and poor peel strength. This experiment provided valuable insights into optimizing the slurry to achieve the highest possible solid content without affecting the electrode properties.
Experiment 3: Optimization of the slurry composition in accordance with the present disclosure
In order to improve the solid content and to improve mass loading capacity of the slurry composition, while maintaining the superior electrode properties and maintaining the required viscosity of slurry composition (4000 ± 500 cP), a binder additive solution was used along with the binder (PVDF) solution in accordance with the present disclosure. Similar experiments without binder additive solutions were also performed for comparison.
The binder solution with 7.8% solid content was prepared by adding polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone under mixing at 500 rpm for 12 hours. A binder additive solution with 7.8% solid content was prepared by adding terpolymer of vinylidene fluoride (VDF) under mixing at 500 rpm for 12 hours.
Experiments were performed with 70% total solid content of the slurry composition. Table 3 represents various slurry compositions with variable amounts of ingredients, along with their effect on slurry composition viscosity, and peel strength and resistance of the electrodes obtained by using respective slurry compositions.
Table 3: Slurry compositions with variable amounts of the ingredients, along with their effect on viscosity, peel strength and resistance
Example No. Slurry composition (wt. %) Measurements
NMC Super P MWCNT PVDF VDF Viscosity Solid content Peel strength Resistance
Example 1 96.8 0.75 0.75 1.5 0.2 3456 70 3.57 0.24
Example 2 97 0.75 0.75 1.2 0.3 2462 70 3.32 0.13
Example 3 97.3 0.75 0.75 0.9 0.3 1423 70 3.08 0.14
Example 4 97.6 0.75 0.75 0.6 0.3 1351 70 1.93 0.13
Comparative Example 2 97 0.75 0.75 1.5 0 3147 70 3.45 0.14
Comparative Example 4 97.3 0.75 0.75 1.2 0 2132 70 3.02 0.11
Comparative Example 5 97.6 0.75 0.75 0.9 0 1504 70 2.96 0.12
Comparative Example 6 97.9 0.75 0.75 0.6 0 1453 70 2.83 0.11

It can be observed from Table 3 and Fig. 1a to Fig. 1c that when the binder (PVDF) solution content was > 1.2, a better peel strength and a low resistance were obtained. However, there was increase in viscosity with the binder (PVDF) solution content of > 1.2. Further, there was no significant change in the electrode properties when the binder additive (terpolymer of VDF) was used along with PVDF in ratios of 1:4 and 1:3 (examples 2 and 3). However, there was significant decrease in viscosity with increase in binder additive (VDF) (examples 2 to 4). This clearly shows a better possibility of increasing the solid content while keeping the slurry homogeneity and desired viscosity. Further, with PVDF and VDF in the ratios of 1:5 and 1:2 (Examples 1 and 4), there was increased resistance with the binder additive and the binder ratio of 1:5 and less peel strength with the binder additive and the binder ratio of 1:2. The slurry composition of Example 2 was selected for further experimentation, due better peel strength and low resistance as compared to Example 3.
Experiment 4: Further optimization of the solid content in the slurry composition of the present disclosure
In order to further optimize the solid content of the slurry composition, the solid content was further increased in the slurry composition. In this experiment, the slurry composition taken was fixed to (active material: carbon black: MWCNT: binder (with or without binder additive)) = (97:0.75:0.75:1.5). The comparative results demonstrating the effect on viscosity, peel strength, resistance and conductivity are as shown in Table 4.
Table 4: Comparative results showing the effect of solid content in the slurry composition in accordance with the present disclosure
Example No. Active Material (NMC)
(%) Carbon Black (CB)
(%) Carbon Nanotubes (MWCNT)
(%) Binder solution (PVDC)
(%) Binder additive
Solution (VDC)
(%) Solid Content
(%) Viscosity
(cP) Peel Strength
(25 N/mm) Resistance
(ohm) Conductivity
(1/ohm)
Comparative Example 2
(70 (WOV)) 97 0.75 0.75 1.5 0 70 3417 3.4 0.14 7.1
Comparative Example 3
(76 (WOV)) 97 0.75 0.75 1.5 0 76 6574 2.4 0.38 2.6
Example 2
(70 (WV)) 97 0.75 0.75 1.2 0.3 70 2462 3.3 0.13 7.7
Example 5
(76 (WV)) 97 0.75 0.75 1.2 0.3 76 4346 3.8 0.24 4.2
It can be observed from Table 4, Fig. 2a, and Fig. 2b that with the addition of the binder additive with the binder additive to binder ratio of 1:4, the electrode properties are either retained or improved, while keeping the viscosity as per requirement. Also, it is observed that with the addition of the binder additive, the ingredients of the slurry composition showed better dispersion in the fluid medium. Further, it can be observed from Fig. 2c that the electrodes prepared by using the binder additives showed better flexibility and resistance to break, as compared to the electrodes prepared without using the binder additive (Fig. 2d). The flexibility of the electrodes was measured by winding the so obtained electrode films over 6 mm rod. Further the slurry composition having the binder additive solution showed higher mass loading of 22 mg/cm2 per side of the electrode.
Experiment 5: Characterization of the slurry compositions of the present disclosure, and the electrodes prepared therefrom
Frequency and amplitude sweep measurements were performed on the slurry compositions.
A. Effect of frequency on the slurry compositions
During frequency measurement, 0.1% of strain was applied and was kept constant throughout the measurement and frequency was changed from 0.01 rad/sec to 1000 rad/sec.
The effect of frequency on the slurry compositions having 76% solid content, with and without binder additive were compared. The results are as shown in Table 5.
Table 5: Comparative effect of the frequency on the slurry composition having 76% solid content and with or with VDF
Frequency
(Hz or rad/sec) Example 5
(G’/G”) (Pa) Comparative Example 3
(G’/G”) (Pa)
50 983.8/ 731.6 617.3/ 568.1
100 1320/ 956.2 884.1/ 769.4

It can be observed from Table 5, Fig. 3a and Fig. 3b that the slurry composition of Example 5 showed higher storage modulus G′ (983.8 Pa at 50 Hz, 1320 Pa at 100 Hz) compared to the slurry composition of comparative Example 3 (617.3 Pa at 50 Hz, 884.1 Pa at 100 Hz), indicating better structural integrity and particle suspension, leading to improved electrode stability. In comparative example 3 without VDF, the less storage modulus G′ make the slurry composition viscous (liquid-like), making it easier to spread but prone to particle settling. It can be concluded that the binder additive (VDF) enhanced mechanical strength, ensured better coating uniformity and adhesion to the current collector.
Further, it can be observed from Table 5, Fig. 3a and Fig. 3b that the slurry composition of Example 5 having VDF showed higher loss modulus (G”) (731.6 Pa at 50 Hz, 956.2 Pa at 100 Hz) as compared to the slurry composition of the Comparative Example 3 (568.1 Pa at 50 Hz, 769.4 Pa at 100 Hz).
B. Effect of amplitude on the slurry composition
During the amplitude measurement, 1 rad/sec frequency was applied and was kept constant throughout the measurement and strain was varied from 0.01% to 1000%.
The effect of amplitude on the slurry compositions having 76% solid content, with or without binder additive were compared. The results are as shown in Table 6.
Table 6: Comparative effect of the amplitude on the slurry composition having 76% solid content and with or without VDF
Amplitude
(%) Example 5
(G’/G”) (Pa) Comparative Example 3
(G’/G”) (Pa)
5 224.5/ 195.9 194.2/ 181.7
10 167/ 174.1 143.5/ 158.8

It can be observed from Table 6, Fig. 3c and 3d that the slurry composition of Example 5 (slurry composition with VDF) exhibited higher storage modulus G' (224.5 Pa at 5 % amplitude and 167.2 Pa at 10 % amplitude), compared to the slurry composition of comparative example 3 (194.2 Pa at 5 % amplitude and 143.5 Pa at 10 % amplitude) indicating a more structured and elastic network. The slurry composition of comparative example 3 showed crossover at 6% amplitude, suggesting weaker mechanical integrity and lower viscoelastic stability.
Further, the slurry composition of Example 5 (slurry composition with VDF) exhibited higher loss modulus G” (195.9 Pa at 5 % amplitude and 174.1 Pa at 10 % amplitude), compared to the slurry composition of comparative example 3 (181.7 Pa at 5 % amplitude and 158.8 Pa at 10 % amplitude).
C. Effect of current-rate on the electrodes prepared by using the slurry compositions
The effect of current rate on the electrodes prepared by using the slurry compositions having 76% solid content, with or without binder additive were compared. The results are as shown in Table 7.
Table 7: Comparative effect of the current rate on the electrodes prepared by using the slurry composition having 76% solid content and with or without VDF
Example No. 1C 3C
Example 5
(with VDF) 92.56 86.75
Comparative Example 3 (without VDF) 91.8 80.34

It can be observed from Table 7 and Fig. 4a that the electrode prepared by using the slurry composition of Example 5 showed better capacity retention percentage at higher current rate of 1C to 3C as compared to the electrode prepared by using the slurry composition of comparative example 3.
D. Life cycle retention of the electrodes prepared by using the slurry compositions

The effect of number of usage cycles on the electrodes prepared by using the slurry compositions having 76% solid content, with or without binder additive were compared. The results are as shown in Table 8.
Table 8: Comparative effect of the number of usage cycles on the electrodes prepared by using the slurry composition having 76% solid content and with or without VDF
Example No. Capacity retention
(%)
Example 5
(with VDF) 98.75
Comparative Example 3
(without VDF) 96.87

It can be observed from Table 8 and Fig. 4b that the electrode prepared by using the slurry composition of Example 5 showed better capacity retention percentage at when used for up to 50 cycles as compared to the electrode prepared by using the slurry composition of comparative example 3.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of:
a positive electrode slurry composition that:
• can accommodate high solid content without compromising the desired properties; and
• has improved loading capacity and can be coated to higher thickness;
a process for the preparation of a positive electrode that:
• is simple, economical and scalable;
and
a positive electrode that:
• has improved peel strength, flexibility and conductivity;
• has improved storage modulus;
• has improved capacity retention at high current rates; and
• has better life cycle retention.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or are common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. , C , Claims:WE CLAIM:
1. A positive electrode slurry composition comprising:
• an active material;
• a conductive agent;
• multi-walled carbon nanotubes (MWCNT);
• a binder solution; and
• a binder additive solution;
wherein a mass ratio of said binder additive solution to said binder solution is in the range of 1:2 to 1:5.
2. The slurry composition as claimed in claim 1, wherein said slurry composition is characterized by having at least one of the following:
• solid content in the range of 65% to 80%;
• viscosity in the range of 1000 cP to 4500 cP;
• storage modulus (G’) in the range of 950 Pa to 1400 Pa at a frequency in the range of 45 Hz to 110 Hz;
• loss modulus (G”) in the range of 720 Pa to 1000 Pa at a frequency in the range of 45 Hz to 110 Hz;
• storage modulus (G’) in the range of 150 Pa to 250 Pa at a strain percent in the range of 2 to 12;
• loss modulus (G”) in the range of 170 Pa to 200 Pa at a strain percent in the range of 2 to 12; and
• loading capacity in the range of 15 mg/cm2 to 25 mg/cm2 per side of an electrode.
3. The slurry composition as claimed in claim 1, wherein
• said active material is present in an amount in the range of 96 mass% to 98 mass% with respect to the total amount of said slurry composition;
• said conductive agent is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of said slurry composition;
• said multi-walled carbon nanotubes (MWCNT) is present in an amount in the range of 0.6 mass% to 0.9 mass% with respect to the total amount of said slurry composition;
• said binder solution is present in an amount in the range of 0.7 mass% to 1.5 mass% with respect to the total amount of said slurry composition; and
• said binder additive solution is present in an amount in the range of 0.2 mass% to 0.35 mass% with respect to the total amount of said slurry composition.
4. The slurry composition as claimed in claim 1, wherein said active material is selected from the group consisting of nickel manganese cobalt (NMC) compound, lithium cobalt oxide, lithium and manganese rich (LMR) nickel manganese cobalt compound and nickel cobalt aluminium (NCA).
5. The slurry composition as claimed in claim 1, wherein said conductive agent is selected from the group consisting of carbon black powder, acetylene black and graphene.
6. The slurry composition as claimed in claim 1, wherein said binder solution is selected from the group consisting of polyvinylidene fluoride (PVDF) solution, polyvinylpyrrolidone (PVP) solution, polyimide solution, polyacrylonitrile solution, and polyamide-imide solution.
7. The slurry composition as claimed in claim 1, wherein said binder additive solution is selected from the group consisting of a terpolymer of vinylidene fluoride (VDF) solution, copolymer of vinylidene fluoride and hexafluoropropylene (VDF-HFP) solution, copolymer of vinylidene fluoride and trifluoroethylene (VDF-TrFE) solution and polyaniline solution.
8. A process for the preparation of a positive electrode, wherein said process comprising the following steps:
i) sequentially mixing predetermined amounts of a binder solution, a binder additive solution, multi-walled carbon nanotubes (MWCNT), first portions of a conductive agent and an active material under stirring followed by adding second portions of said conductive agent and said active material to obtain a slurry composition;
ii) coating said slurry composition on a current collector at a predetermined thickness to obtain a coated electrode;
iii) drying said coated electrode at a predetermined temperature for a predetermined time period to obtain a dried electrode; and
iv) calendaring said dried electrode to a predetermined density to obtain said positive electrode.
9. The process as claimed in claim 8, wherein a mass ratio of said binder additive solution to said binder solution is in the range of 1:2 to 1:5.
10. The process as claimed in claim 8, wherein
• said predetermined amount of said active material is in the range of 96 mass% to 98 mass% with respect to the total mass of said slurry composition;
• said predetermined amount of said conductive agent is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of said slurry composition;
• said predetermined amount of said multi-walled carbon nanotubes (MWCNT) is in the range of 0.6 mass% to 0.9 mass% with respect to the total mass of said slurry composition;
• said predetermined amount of said binder solution is in the range of 0.7 mass% to 1.5 mass% with respect to the total mass of said slurry composition; and
• said predetermined amount of said binder additive solution is in the range of 0.2 mass% to 0.35 mass% with respect to the total mass of said slurry composition.
11. The process as claimed in claim 8, wherein said binder additive solution has a solid content in the range of 6% to 9%; and said binder solution has a solid content in the range of 6% to 9%.
12. The process as claimed in claim 8, wherein said stirring is carried out at a speed is in the range of 1500 rpm to 2500 rpm; and said stirring is carried out for a time period is in the range of 1 hour to 3 hours.
13. The process as claimed in claim 8, wherein said predetermined thickness is in the range of 50 microns to 160 microns.
14. The process as claimed in claim 8, wherein said predetermined temperature is in the range of 90 oC to 110 oC; said predetermined time period is in the range of 4 hours to 8 hours; and said predetermined density is in the range of 2 g/cc to 5 g/cc.
15. A positive electrode obtained by using the process as claimed in claim 8 is characterized by having at least one of the following:
• peel strength in the range of 3 N/mm to 4 N/mm;
• conductivity in the range of 4 ohm-1 to 8 ohm-1;
• percentage capacity retention in the range of 85% to 95% at a current-rate in the range of 1C to 3C;
• percentage capacity retention in the range of 98% to 99% when used for up to 50 cycles;
• thickness is in the range of 35 microns to 100 microns; and
• density in the range of 2 g/cc to 5 g/cc.
Dated this 26th Day of May 2025

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
OF R. K. DEWAN & CO.
AUTHORIZED AGENT OF APPLICANT

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT CHENNAI