A process for preparing an electrode film and implementations thereof

Abstract

The present disclosure provides a process for preparing an electrode fdm, the process comprising: first calendering through a first set of rollers (101) to obtain a first film and second calendering the first film through a second set of rollers (102) to obtain an electrode film, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc. The present disclosure further provides an electrode film obtained by the process as disclosed herein, an electrode comprising the electrode film as disclosed herein, a method of preparing the electrode as disclosed herein, a first electrochemical cell comprising the electrode as disclosed herein, and a use of the electrode film, electrode and electrochemical cell as disclosed herein.

Description

A PROCESS FOR PREPARING AN ELECTRODE FILM AND IMPLEMENTATIONS THEREOFFIELD OF INVENTION

[0001] The present disclosure broadly relates to the field of battery. Particularly, the present disclosure relates to a process of preparing an electrode film.BACKGROUND OF INVENTION

[0002] With increasing global demand for batteries, developing more efficient processes for preparation of electrode composition is a growing focus of the industry. The conventional electrode preparation for lithium-ion batteries often involves a wet electrode process. Conventional wet electrode processes include dissolving the binder in a solvent and dispersing the active material and conductive additive mixture in the binder solution. The resulting slurry is coated over a current collector and the solvent is removed by heating. The resultant electrode consists of binder getting coated on the active material. Due to the inconvenience and impracticality of scaling up such wet processes, the battery manufacturing has shifted toward dry electrode processes.

[0003] Dry processed electrodes permit better ionic conductivity when compared to wet processed electrodes at a similar electrode density. Electrode engineering plays a significant role in determining the key performance factors of a lithium-ion cell such as volumetric energy density and rate performance. While electrode density, and mass loading of active material play key roles in determining the cell’s energy density. The electron and lithium-ion transport properties of the electrode determine the rate performance of the cell. One major factor upon which the electron and ion transportation depend directly on is electrode density. Improving electrode density of dry electrodes could also enhance the electrode properties like, peel strength, initial columbic efficiency (ICE), and energy density while maintaining good ionic conductivity of the electrodes. An electrode with high density with reduced porosity provides a higher volumetric energy density. However, as a consequence of the reduced porosity in such electrodes, the lithium- ion transfer kinetics are severely impeded due to reduced surface area, putting anupper limit on the electrode density. An electrode with lower density and higher porosity provides a better ion transport. However, loosely bound active materials impede the electron transport in the electrode, creating a higher polarization resistance on the electrode. Additionally, volume expansion during cycling hampers structural integrity of the electrode, leading to loss of capacity during cycling. As a result of this trade off, it is necessary to strike a balance between the electrode density and transport properties to achieve an optimum cell performance.

[0004] Therefore, there exists a need for developing an efficient dry electrode process to achieve an electrode with optimised porosity and electrode density.SUMMARY OF THE INVENTION

[0005] In a first aspect of the present disclosure, there is provided a process for preparing an electrode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. adding a fibrillating binder to the first mixture followed by high shear mixing to obtain a second mixture; c. first calendering the second mixture through a first set of rollers (101) having a roller gap in a range of 100 to 400 pm, and at a differential roller speed in a range of 40 to 88% to obtain a first film ; and d. second calendering the first film through a second set of rollers (102) at a roller force in a range of 12 to 25 kN, at a differential roller speed in a range of 70 to 80%, to obtain an electrode film, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

[0006] In a second aspect of the present disclosure, there is provided an electrode film obtained by the process as disclosed herein, the electrode film comprising: a. an active material; b. at least one conductive additive; and c. at least one binder, wherein the electrode film that has a porosity in a range of 17 to 22% and a density in a range of least 1.7 to 3.9g / cc.

[0007] In a third aspect of the present disclosure, there is provided an electrode comprising the electrode film as disclosed herein, laminated on one side or both sides of a current collector.

[0008] In a fourth aspect of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, the method comprising:a. obtaining a mixture comprising an active material, at least one conductive additive, a non-fibrillating binder, and a fibrillating binder; b. allowing a first part of the mixture from input A to pass through a first set of rollers (101) for first calendering to obtain a first film A, and allowing a second part of the mixture from input A’ to pass through a third set of rollers (103) for first calendering to obtain a first film A’; c. second calendering the first film A through a second set of rollers (102) to obtain a second film B and second calendering the first film A’ through a fourth set of rollers (104) to obtain a second film B’; and d. simultaneously laminating the second film B and the second film B’ on a current collector to obtain the electrode, wherein the electrode has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

[0009] In a fifth aspect of the present disclosure, there is provided a first electrochemical cell comprising: a. a cathode; b. an anode comprising the electrode film as; and c. an electrolyte.

[0010] In a sixth aspect of the present disclosure, there is provided a second electrochemical cell comprising: a. a cathode comprising the electrode film as disclosed herein; b. an anode; and an electrolyte.

[0011] In a seventh aspect of the present disclosure, there is provided a third electrochemical cell comprising: a. the electrode as disclosed herein as cathode; b. the electrode as disclosed herein as anode; and c. an electrolyte.

[0012] In an eighth aspect of the present disclosure, there is provided a use of the electrode film as disclosed herein or the electrode as disclosed herein, as a working electrode in an electrochemical cell

[0013] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE FIGURES

[0014] The following drawings form a part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.

[0015] Figure 1A depicts the schematic representation of the method of preparing the electrode film, in accordance with an embodiment of the present disclosure.

[0016] Figure IB depicts the schematic representation of the method of preparing the electrode, in accordance with an embodiment of the present disclosure.

[0017] Figure 2 A depicts the (i) surface and (ii) cross-sectional scanning electron microscopic (SEM) images of anodes (a) D-l; (b) D-2; (c) D-3, in accordance with an embodiment of the present disclosure.

[0018] Figure 2B depicts the (i, iii) surface and (ii, iv) cross-sectional SEM images of the (i, ii) cathode C-0 and (iii, iv) cathode C-l, in accordance with an embodiment of the present disclosure.

[0019] Figure 3 depicts the specific capacity graph for various anode D-l, D-2 and D-3, in accordance with an embodiment of the present disclosure.

[0020] Figure 4 depicts the life cycle graph of the anode D-l (cell-1) and D-2(cell- 2), in accordance with an embodiment of the present disclosure.

[0021] Figure 5 depicts the (a) specific capacity analysis graph and (b) life cycle analysis graph of the cathode C- 1 , in accordance with an embodiment of the present disclosure.

[0022] Figure 6 depicts the (a) charge-discharge analysis graph; and (b) life cycle analysis graph of the full electrochemical cell, in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0023] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions,and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any or more of such steps or features. Definitions

[0024] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

[0025] The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0026] The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.

[0027] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0028] The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.

[0029] The term “w / w” means the percentage by weight, relative to the weight of the total composition, unless otherwise specified.

[0030] The term "at least one" is used to mean one or more and thus includes individual components as well as mixtures / combinations.

[0031] The term “electrode film” refers to the free-standing film or layer comprising an active material, at least one conductive additive, and at least one binder. In an aspect of the present disclosure, ether is provided an electrode film obtained by the process as disclosed herein, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

[0032] The term “electrode” refers to the conducting material which is in electrical contact with a non -metallic part of the circuit namely electrolyte. In an aspect of thepresent disclosure, electrode refers to the material obtained by laminating an electrode film over a suitable current collector.

[0033] The term “high shear mixing” refers to the process that disperses one phase or ingredient into a main continuous phase at a high force and speed of blades. In an aspect of the present disclosure, the high shear mixing is carried out at a tip speed in a range of 30 to 4 Im / s, for a period in a range of 5 to 60 minutes, until temperature of the mixture is in a range of 65 to 85 °C.

[0034] The term “calendering” refers to the process by which a material is passed through a set of rollers or calender to obtain a uniform sheet or film. The term “first calendering” refers to the calendering process wherein the calendering rollers are set at a specific gap between them to result in a specific thickness of the film. The term “second calendering” refers to calendering process wherein the calendering rollers are set to apply a predetermined force on the film which is greater than the roller force applied while first calendering to result in a specific thickness of the film and initiate fibrillating of fibrillating binder. In another aspect of the present disclosure, the first calendering is carried out through a first set of rollers (101) having a roller gap in a range of 100 to 400 pm, and at a differential roller speed in a range of 40 to 88%. In another aspect of the present disclosure, the second calendering is carried out through a second set of rollers (102) at a roller force in a range of 12 to 25 kN, at a differential roller speed in a range of 70 to 80%. In a similar aspect of the present disclosure, the first calendering is carried out through third set of rollers (103) and the second calendering is carried out through fourth set of rollers (104) configured similar to the first set of rollers (101) and the second set of rollers (102) respectively.

[0035] The term “jet milling” refers to the process by which a material is grinded using a high-speed jet of compressed air or inert gas to impact particles into each other. In an aspect of the present disclosure, the jet milling is carried out at a feeding pressure in a range of 1 to 3kg / cm2; a milling pressure in a range of 1 to 3 kg / cm2; and at a temperature in a range of 10 to 25 °C.

[0036] The term “differential roller speed” refers to the percentage difference between the rotation speed of the rollers. The differential roller speed is an important parameter in calendering process as this is directly related to applying ashear % on the calendered film. Hence, the differential roller speed may also be expressed in terms of the shear rate introduced as a result of the differential roller speed. In an aspect of the present disclosure, the first calendering is carried out at a differential roller speed in a range of 40 to 88%.

[0037] The term “progressively decreasing roller gap” refers to the trend of reducing the roller gap between two rollers in a set of rollers. In an aspect of the present disclosure, there is provided a process of preparing the electrode film as disclosed herein, wherein the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap.

[0038] The term “roller speed” refers to the speed at which a set of rollers are rotated to result in calendering of a mixture and obtain a film. In an aspect of the present disclosure, there is provided a process of preparing the electrode film as disclosed herein, the second calendering is carried out at a roller speed in a range of 0.5 to 25 m / min. The roller speed affects the thickness, compactness, etc. of the electrode film.

[0039] The term “roller force” refers to the force applied by a pair of rollers upon a film which is subjected to calendering. In an aspect of the present disclosure, there is provided a method of preparing the electrode film as disclosed herein, the second calendering is carried out at a roller force in a range of 12 to 25 kN. The roller force affects the electrode film properties such as thickness, compactness, density, and porosity of the electrode film.

[0040] The term “first set of rollers” refers to the set of rollers in a range of 3 to 5 rollers used for first calendering of a film material wherein the rollers are defined in terms of a fixed roller gap, differential roller speed and roller temperature to achieve a film with specified thickness, mass loading, compactness, porosity, and density. In an aspect of the present disclosure, there is provided a process of preparing an electrode film, wherein first calendering is carried out through a first set of rollers (101) having a roller gap in a range of 100 to 400 pm, differential roller speed of 40 to 85% and roller temperature of 100 to 200 °C.

[0041] The term “second set of rollers” refers to the set of rollers in a range of 5 to 7 rollers used for second calendering of a film material wherein the rollers are defined in terms of a roller force, differential roller speed and roller temperature toachieve a film with specified thickness, mass loading, compactness, porosity, and density. In an aspect of the present disclosure, there is provided a process of preparing an electrode film, wherein second calendering is carried out through a second set of rollers (102) at a roller force of 12 to 25 kN, at a differential roller speed of 70 to 80% and roller temperature of 100 to 200 °C.

[0042] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, weight percentage in the range of 0.1% to 2.5% (w / w) should be interpreted to include not only the explicitly recited limits of 0.1% to 2.5% (w / w) but also to include subranges, such as 1% to 2% (w / w), 1.5% to 2.5% (w / w) and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 1.8% (w / w), 1.5% (w / w), and 0.8% (w / w).

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0044] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products, compositions, formulations, and methods are clearly within the scope of the disclosure, as described herein.

[0045] As discussed in the background, there are many challenges in developing a dry electrode having both better density and higher porosity. An electrode with lower density and higher porosity provides a better ion transport. However, loosely bound active materials impede the electron transport in the electrode, creating a higher polarization resistance on the electrode. There is a need to develop anelectrode with better electrode density and transport properties to achieve an optimum cell performance with reduced capacity loss. The currently employed ‘gap’ calendering process wherein the set of rollers are fixed at a specific gap, is not efficient enough to improve electrode density.

[0046] Higher electrode density also offers benefits in terms of physical properties of the electrode such as enhanced structural integrity and improved mechanical strength due to thin / dense fibrillation. Better adhesion between electrode film and current collector leads to improved electrochemical performance during cycling. This is particularly important in rechargeable dry battery systems, where electrodes undergo repeated expansion and contraction during charge and discharge cycles. Additionally, increasing the density of the electrode can improve the rate capability of the cell. Rate capability refers to the ability of a battery to deliver or accept a high current or power output. Higher electrode density allows for faster diffusion of ions and electrons, facilitating rapid charge and discharge rates. This is crucial in applications that require high-power performance, such as electric vehicles or grid energy storage. However, it is important to note that there may be practical limitations to increasing electrode density. Extremely high densities can lead to reduced porosity and limited electrolyte penetration, which may adversely affect the overall electrochemical performance. Therefore, finding an optimal density that balances conductivity, structural integrity, and rate capability is essential in electrode design and manufacturing. Overall, increasing the density of a dry electrode can be an effective strategy to mitigate the negative effects of increased interface resistance, improve the physical properties of the electrode, and enhance the performance of the cell. Accordingly, the present disclosure provides a process for optimising the porosity and density of an electrode via repeated first calendering and second calendering steps.

[0047] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. adding a fibrillating binder to the first mixture followed by high shear mixing to obtain a second mixture; c. first calendering the second mixture through a first set of rollers (101) having a roller gap in a range of 100 to 400 pm,and at a differential roller speed in a range of 40 to 88% to obtain a first film; and d. second calendering the first film through a second set of rollers (102) at a roller force in a range of 12 to 25 kN, at a differential roller speed in a range of 70 to 80%, to obtain an electrode film, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc, as represented in Figure 1A. In another embodiment of the present disclosure, the first set of rollers (101) has a roller gap in a range of 250 to 350 pm.

[0048] In an embodiment of the present disclosure, there is provided a process for preparing an anode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. adding a fibrillating binder to the first mixture followed by high shear mixing to obtain a second mixture; c. introducing the second mixture into a first set of rollers at a flow rate in a range of 80 to 150g / min followed by first calendering the second mixture through the first set of rollers (101) having a roller gap in a range of 100 to 400 pm, and at a differential roller speed in a range of 40 to 88% to obtain a first film; and d. second calendering the first film through a second set of rollers (102) at a roller force in a range of 12 to 25 kN, and at a differential roller speed in a range of 70 to 80%, to obtain the anode film, wherein the anode film having a porosity in a range of 18 to 22% and a density in a range of 1.75 to 1.95 g / cc. In yet another embodiment of the present disclosure, the anode film has a porosity in a range of 18 to 22% and a density in a range of 1.75 to 1.85 g / cc. In yet another embodiment of the present disclosure, the anode film has a porosity of 20 to 21 % and a density of 1.75 to 1.8 g / cc.

[0049] In an embodiment of the present disclosure, there is provided a process for preparing a cathode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. high shear mixing a fibrillating binder with the first mixture to obtain a second mixture; c. first calendering the second mixture through a first set of rollers (101) to obtain a first film; and d. second calendering the first film through a second set of rollers (102) to obtain the cathode film, wherein the cathode film having a porosity in a range of 17 to 21% and a density in a range of 3.7 to 3.9 g / cc. In another embodiment of the present disclosure, the cathode film has a porosity in arange of 17.5 to 21% and a density in a range of 3.7 to 3.85 g / cc. In yet another embodiment of the present disclosure, the cathode film having a porosity of 18 to 19 % and a density of 3.75 to 3.82 g / cc.

[0050] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the second set of rollers (102) comprises ‘n’ number of rollers wherein each roller rotates in a progressively increasing roller speed; ‘m’ is in a range of 2 to 5; and ‘n’ is in a range of 2 to 10. In another embodiment of the present disclosure, the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the second set of rollers (102) comprises ‘n’ number of rollers wherein each roller rotates in a progressively increasing roller speed; ‘m’ is in a range of 2 to 3; and ‘n’ is in a range of 2 to 7.

[0051] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein the first set of rollers (101) and the second set of rollers (102) have a roller temperature in a range of 100 to 200 °C.

[0052] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein the active material is selected from natural graphite, synthetic graphite, silicon, silicon-graphite, nickel- manganese-cobalt oxide (NMC), lithium-nickel-cobalt-aluminium oxides (NCA), lithium iron phosphate (LFP), or lithium -manganese-rich (LMR). In another embodiment of the present disclosure, the active material is natural graphite when the electrode film is an anode film. In yet another embodiment of the present disclosure, the active material is nickel-manganese-cobalt oxide (NMC) when the electrode film is a cathode film.

[0053] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein the active material is in a weight range of 96 to 99% w / w. In another embodiment of the present disclosure, the active material is in a weight range of 96.5 to 98.5% (w / w). In another embodiment of the present disclosure, the active material is in a weight range of96.5 to 98.5% w / w. In yet another embodiment of the present disclosure, the active material is in a weight range of 97 to 98% (w / w).

[0054] In an embodiment of the present disclosure, there is provided a process for preparing an electrode fdm as disclosed herein, wherein the at least one conductive additive is selected from carbon black, graphene, graphite, mesoporous carbon, acetylene black, activated carbon, super P, carbon nanofiber, vapour grown carbon nanofiber, carbon nanotube, or combinations thereof. In another embodiment of the present disclosure, wherein the at least one conductive additive is selected from carbon black, vapour grown carbon nanofiber or combinations thereof. In yet another embodiment of the present disclosure, wherein the at least one conductive additive is selected from carbon black (Ketjen black), graphite (KS6L) or combinations thereof.

[0055] In an embodiment of the present disclosure, there is provided a process for preparing an electrode fdm as disclosed herein, wherein the at least one conductive additive is in a weight range of 0.5 to 2% (w / w). In another embodiment of the present disclosure, wherein the at least one conductive additive is in a weight range of 1.5% (w / w).

[0056] In an embodiment of the present disclosure, there is provided a process for preparing an electrode fdm as disclosed herein, wherein the fibrillating binder is selected from polytetrafluoroethylene (PTFE), fluoroethylene vinyl ether (FEVE), fluoroethylene polymer (FEP), or combinations thereof. In another embodiment of the present disclosure, the fibrillating binder is polytetrafluoroethylene (PTFE).

[0057] In an embodiment of the present disclosure, there is provided a process for preparing an electrode fdm as disclosed herein, wherein fibrillating binder is in a weight range of 0.5 to 3% (w / w). In another embodiment of the present disclosure, wherein fibrillating binder is in a weight range of 0.5 to 2% (w / w). In yet another embodiment of the present disclosure, wherein fibrillating binder is in a weight of 1% (w / w).

[0058] In an embodiment of the present disclosure, there is provided a process for preparing an electrode fdm as disclosed herein, wherein the non-fibrillating binder is selected from polyvinylidene fluoride (PVDF), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), sodiumcarboxymethyl cellulose (Na-CMC), carboxymethyl cellulose (CMC), styrene butadiene rubber, polyethylene glycol (PEG), polyacrylic acid (PAA), polyethylene oxide (PEO), poly vinyl pyrrolidone (PVP), poly(vinylidene fluoride-co- hexafluoropropylene) (PCDF-HFP) or combinations thereof. In another embodiment of the present disclosure, the non-fibrillating binder is polyvinylidene fluoride (PVDF).

[0059] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein non-fibrillating binder is in a weight range of 0.5 to 3% (w / w). In another embodiment of the present disclosure, wherein non-fibrillating binder is in a weight range of 0.75 to 2% (w / w). In yet another embodiment of the present disclosure, wherein non-fibrillating binder is in a weight of 1% (w / w).

[0060] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein high shear mixing is carried out at a tip speed in a range of 30 to 4 Im / s, for a period in a range of 5 to 60 minutes, until temperature of the mixture is in a range of 65 to 85 °C.

[0061] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein the second mixture is cooled to a temperature below 19°C followed by jet milling, prior to first calendering.

[0062] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film as disclosed herein, wherein cooling is carried out with low-speed mixing at a tip speed in a range of 3 to 20 m / s.

[0063] In an embodiment of the present disclosure, there is provided a process for preparing an electrode film, wherein the jet milling is carried out at a feeding pressure in a range of 1 to 3kg / cm2; a milling pressure in a range of 1 to 3 kg / cm2; and at a temperature in a range of 10 to 25 °C.

[0064] In an embodiment of the present disclosure, there is provided a process for preparing an anode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. high shear mixing the first mixture with a binder to obtain a second mixture which is cooled with low-speed mixing at a tip speed in a range of 3 to 20m / s to a temperature below 19°C and jet milled at a feeding pressure of 1 to 3 kg / cm2; a milling pressure in a range of 1 to 3 kg / cm2; and at a temperature of 10 to 25°C to obtain a jet milled second mixture; c. first calendering the second mixture through a first set of rollers at a roller speed of 0.1 to 0.6 m / min, a roller gap of 100 to 400 pm, a differential roller speed of 70 to 80%, and a roller temperature in a range of 140 to 160 °C to obtain a first film; second calendering the first film through a second set of rollers at a roller force adjusted in a range of 12- 16 kN, at roller speed of 0.4 - 1.0 m / min, at differential roller speed of 70 to 80%, and at a roller temperature of 140 to 160 °C to obtain a second film; second calendering the second film through a first set of rollers with roller force of 14kN - 18 kN, at roller speed of 0.4 - 1.0 m / min, at a differential roller speed in a range of 70 to 80%, and at a roller temperature of 140 to 160 °C to obtain the anode film.

[0065] In an embodiment of the present disclosure, there is provided a process for preparing a cathode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. high shear mixing a fibrillating binder with the first mixture to obtain a second mixture followed by cooling the second mixture with low-speed mixing at a tip speed in a range of 3 to 20 m / s to a temperature below 19°C and jet milling at a feeding pressure of 1 to 3 kg / cm2; a milling pressure in a range of 1 to 3 kg / cm2; and at a temperature of 10 to 25°C to obtain jet milled second mixture; c. first calendering the second mixture through a first set of rollers in gap -controlled mode where a constant roller gap of 250 - 350 pm, roller speed of 0.1 - 0.8 m / min, differential roller speed of 40 to 88% and roller temperature of 120-180 °C to obtain a first film; and d. second calendering the first film through a second set of rollers at a constant roller force of 12kN - 15 kN, at roller speed of 0.4 - 1.0 m / min, at differential roller speed of 70-80% and at roller temperature of 120-180 °C to obtain a second film; second calendering the second film through a second set of rollers at a constant roller force of 12kN - 15 kN, roller speed of 0.4 to 1.0 m / min, differential roller speed of 70-80% and roller temperature of 120-180 °C to obtain athird film; second calendering the third film through a second set of rollers at a constant rollerforce of 12kN - 25 kN, roller speed of 0.6 to 1.5 m / min, at a differential roller speed of 70 to 80% and at a roller temperature of 120 to 180 °C to obtain the cathode film.

[0066] In an embodiment of the present disclosure, there is provided an electrode film obtained by the process as disclosed herein, the electrode film comprising: a. an active material; b. at least one conductive additive; and c. at least one binder, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

[0067] In an embodiment of the present disclosure, there is provided an anode film obtained by the process as disclosed herein, the anode film comprising: a. an active material; b. at least one conductive additive; and c. at least one binder, wherein the anode film has a porosity in a range of 18 to 22% and a density in a range of 1.75 to 1.85g / cc. In another embodiment of the present disclosure, the anode film has a porosity in a range of 20 to 22% and a density in a range of 1.76 to 1.83g / cc.

[0068] In an embodiment of the present disclosure, there is provided a cathode film obtained by the process as disclosed herein, the cathode film comprising: a. an active material; b. at least one conductive additive; and c. at least one binder, wherein the cathode film has a porosity in a range of 17.5 to 21% and a density in a range of 3.7 to 3.85g / cc. In another embodiment of the present disclosure, the cathode film has a porosity in a range of 18 to 20% and a density in a range of 3.75 to 3.85g / cc.

[0069] In an embodiment of the present disclosure, there is provided an electrode film obtained by the process as disclosed herein, wherein the electrode film has an active material loading in a range of 10 to 30 mg / cm2. In another embodiment of the present disclosure, the electrode film has an active material loading in a range of 15 to 25 mg / cm2. In yet another embodiment of the present disclosure, the electrode film has an active material loading in a range of 15 to 17 mg / cm2for anode film. In still another embodiment of the present disclosure, the electrode film has an active material loading in a range of 25 to 27 mg / cm2, for anode film.

[0070] In an embodiment of the present disclosure, there is provided an electrode film obtained by the process as disclosed herein, wherein the electrode film has a thickness in a range of 60 to 110 pm. In another embodiment of the present disclosure, the electrode film has a thickness in a range of 65 to 100 pm. In yetanother embodiment of the present disclosure, the electrode fdm has a thickness in a range of 75 to 100 pm for anode fdm. In still another embodiment of the present disclosure, the electrode fdm has a thickness in a range of 65 to 75 pm, for cathode fdm.

[0071] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein at least one binder is selected from a fibrillating binder, a non-fibrillating binder or combinations thereof.

[0072] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein the electrode fdm has an aerial loading in a range of 10 to 30 mg / cm2.

[0073] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein the electrode fdm has a porosity in a range of 18 to 22% and a density in a range of 1 to 2 g / cc, when the electrode fdm is an anode fdm.

[0074] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein the electrode fdm has a porosity in a range of 18 to 22% and a density in a range of 1 to 2 g / cc, when the electrode fdm is an anode fdm and the anode fdm exhibits a specific capacity in a range of 340 to 360 mAh / g.

[0075] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein the electrode fdm has a porosity in a range of 17 to 21% and a density in a range of 3 to 4 g / cc, when the electrode fdm is a cathode fdm.

[0076] In an embodiment of the present disclosure, there is provided an electrode fdm as disclosed herein, wherein the electrode fdm has a porosity in a range of 17 to 21% and a density in a range of 3 to 4 g / cc, when the electrode fdm is a cathode fdm and the cathode fdm exhibits a specific capacity in a range of 205 to 215 mAh / g.

[0077] In an embodiment of the present disclosure, there is provided an electrode comprising the electrode fdm as disclosed herein, laminated on one side or both sides of a current collector.

[0078] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, the method comprising: a. obtaining amixture comprising an active material, at least one conductive additive, a non- fibrillating binder, and a fibrillating binder; b. allowing a first part of the mixture from input A to pass through a first set of rollers ( 101 ) for first calendering to obtain a first film A, and allowing a second part of the mixture from input A’ to pass through a third set of rollers (103) for first calendering to obtain a first film A’; c. second calendering the first film A through a second set of rollers (102) to obtain a second film B and second calendering the first film A’ through a fourth set of rollers (104) to obtain a second film B’; and d. simultaneously laminating the second film B and the second film B’ on either sides of a current collector to obtain the electrode, wherein the electrode has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc, as represented in Figure IB.

[0079] In an embodiment of the present disclosure, there is provided a method as disclosed herein, wherein the first set of rollers (101) is placed at input A near proximal end; the second set of rollers (102) is placed successive to the first set of rollers (101); the third set of rollers (103) is placed at input A’ near distal end; the fourth set of rollers (104) is placed successive to the third set of rollers (103); and the last roller of the second set of rollers (102) meet the last roller of the fourth set of rollers (104) at the center.

[0080] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein the first set of rollers (101) and the third set of rollers (103) have a roller gap in a range of 100 to 400 pm and rotate at a differential roller speed in a range of 40 to 88%.

[0081] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein the second set of rollers (102) and the fourth set of rollers (104) exert a roller force upon the first film in a range of 12 to 25 kN and rotate at a differential roller speed in a range of 70 to 80%.

[0082] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the second set of rollers (102) comprises ‘n’ number of rollers wherein each roller rotates in a progressively increasing roller speed; the third set of rollers (103) comprises ‘o’ number of rollers wherein each pair of rollers has aprogressively decreasing roller gap; the fourth set of rollers (104) comprises ‘p’ number of rollers wherein each roller rotates in a progressively increasing roller speed; ‘m’ and ‘o’ are in a range of 2 to 5; and ‘n’ and ‘p’ are in a range of 2 to 10.

[0083] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein mixture is obtained by premixing an active material with at least one conductive additive and a non- fibrillating binder followed by high shear mixing with a fibrillating binder.

[0084] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein the last roller of the second set of rollers and the last roller of the fourth set of rollers rotate in the same rotating speed, in a range of 0.5 to 25 m / min.

[0085] In an embodiment of the present disclosure, there is provided a method of preparing an electrode as disclosed herein, wherein laminating is carried out at a roller force in a range of 15 to 40 kN, a roller speed in a range of 0.2 to 5.0 m / min and a roller temperature in a range of 60 to 200 °C. In another embodiment of the present disclosure laminating is carried out at a roller force in a range of 25 to 35 kN, a roller speed in a range of 0.3 to 1.0 m / min and a roller temperature in a range of 140 to 160 °C. In yet another embodiment of the present disclosure, there is provided a process for preparing a cathode film, wherein laminating is carried out at a roller force in a range of 15 to 30 kN, a roller speed in a range of 0.2 to 0.8 m / min and a roller temperature in a range of 120 to 180 °C.

[0086] In an embodiment of the present disclosure, there is provided a first electrochemical cell comprising: a. a cathode; b. the electrode as disclosed herein as anode; and c. an electrolyte.

[0087] In an embodiment of the present disclosure, there is provided a second electrochemical cell comprising: a. the electrode as disclosed herein as cathode; b. an anode; and an electrolyte.

[0088] In an embodiment of the present disclosure, there is provided a third electrochemical cell comprising: a. the electrode as disclosed herein as cathode; b. the electrode as disclosed herein as anode; and c. an electrolyte.

[0089] In an embodiment of the present disclosure, there is provided an electrochemical cell as disclosed herein, wherein the electrolyte is selected fromLiPFr, or LiBF4 dissolved in a solvent selected from ethyl carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), vinylene carbonate (VC), 1, 3- propane sultone (PS), succinonitrile (SN), or combinations thereof. In another embodiment of the present disclosure, the electrolyte is LiPFr, dissolved in a solvent selected from ethyl carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or combinations thereof, or LiBF4 dissolved in a solvent selected from vinylene carbonate (VC), 1, 3-propane sultone (PS), succinonitrile (SN), or combinations thereof. In yet another embodiment of the present disclosure, the electrolyte is LiPFr, dissolved in a solvent selected from ethyl carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or combinations thereof.

[0090] In an embodiment of the present disclosure, there is provided a use of the electrode fdm as disclosed herein, as a working electrode in an electrochemical cell.

[0091] Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.Examples

[0092] The disclosure will now be illustrated with working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices, and materials are described herein. It is to beunderstood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.Materials and Methods

[0093] The various chemicals and solvents used in the present disclosure are as follows:

[0094] Synthetic graphite, - ZeichenNMC-811 - EaspringKetjen black, - Nouryon super P, KS6L - Imerys vapour grown carbon fibre (VGCF) - Nanografi polyvinylidene fluoride (PVDF) - Arkema polytetrafluoroethylene (PTFE) - Diakin Copper current collector - Iljin; and Aluminium current collector - DingshengEXAMPLE 1Preparation of electrode and electrochemical cellPreparation of anode film

[0095] Ninety-seven percentage by weight (97% (w / w)) of synthetic graphite (anode active material) was pre-mixed with 0.5% (w / w) of super P (conductive additive) and 0.5% (w / w) of vapour grown carbon fibre (VGCF) (conductive additive) and 1% (w / w) of polyvinylidene fluoride (PVDF, non-fibrillating binder) to obtain a first mixture. The first mixture was then high shear mixed with 1% (w / w) of polytetrafluoroethylene (PTFE, fibrillating binder) at a tip speed of 30 to 41m / s, for a period in a range of 5 to 60 minutes, until temperature of the mixture is of 75 °C to obtain a second mixture. The second mixture was cooled, with low speed mixing at a tip speed in a range of 12.25 m / s to a temperature below 19°C. The cooled second mixture was then jet milled at a feeding pressure of 2 kg / cm2; a milling pressure in a range of 2 kg / cm2; and at a temperature of 20°C. The second mixture hence obtained was used to prepare different anode films namely Dl-Dl’, D2-D2’ and D3-D3’ with varying density and porosity values by altering thecalendering parameters. Figure 1A shows the schematic representation of the method of preparing the electrode film.

[0096] Further the electrode films are laminated on both sides of a current collector to obtain an electrode. Figure IB shows the schematic representation of the method of preparing the electrode.Preparation of anode film D-l

[0097] The second mixture was subjected to first calendering through a first set of rollers (102) and third set of rollers (103) at a roller gap of 100 - 400 pm with the roller speed of 0.1- 0.6 m / min to obtain an anode film DI and DI’ respectively.

[0098] The anode films D 1 and D 1 ’ were then simultaneously laminated on both sides of a copper current collector with roller force adjusted to 25kN - 35 kN, at a roller speed of 0.3 - 1.0 m / min and at a roller temperature of 140- 160 °C to obtain an anode D-l (electrode).Preparation of anode film D-2

[0099] 50% by weight of the second mixture was subjected to first calendering through a first set of rollers (101) at a roller gap of 250 - 350 pm, at a roller speed of 0.1 to 0.6 m / min, a differential roller speed of 70 to 80%, and a roller temperature in a range of 140 to 160 °C to obtain a first film Ai. Remaining 50% by weight of the second mixture was allowed to pass through a third set of rollers (103) wherein a pair of rollers adjusted at a roller gap of 250 - 350 pm, at a roller speed of 0.1 to 0.6 m / min, a differential roller speed of 70 to 80%, and a roller temperature of 140 to 160 °C to obtain a first film Ai’. The first and third set of rollers had 2 rollers each.The first films were then subjected to second calendering through a second (102) and a fourth set of rollers (104) under the below conditions:

[0100] The first film A2 was subjected to second calendering through second set of rollers (102) wherein a pair of rollers having roller force adjusted at 12-16 kN, at roller speed of 0.4 - 1.0 m / min, at differential roller speed of 70 to 80%, and at a roller temp of 140-160 °C to obtain a second film B2. The first film A2’ was subjected to second calendering through a fourth set of rollers (104) wherein a pair of rollers having roller force adjusted at 12-16 kN, at roller speed of 0.4 - 1.0 m / min, at differential roller speed of 70 to 80%, and at a roller temp of 140-160 °C to obtain a second film B2’. The second and fourth set of rollers had 7 rollers each.

[0101] The obtained second films B2 and B2’ was subjected to second calendering wherein the subsequent pair of rollers at a roller force of 14kN - 18 kN, at roller speed of 0.4 - 1.0 m / min, at a differential roller speed of 70-80%, and at a roller temperature of 140-160 °C to obtain the anode films D2 and D2’ each having a density of 1.79 g / cc and a thickness of 92 pm.

[0102] The anode films D2 and D2’ were then simultaneously laminated on both sides of a copper current collector using the last roller of the second set of rollers (102) and the last roller of the fourth set of rollers (104) with roller force adjusted to 25kN - 35 kN, at a roller speed of 0.3 - 1.0 m / min and at a roller temperature of 140- 160 °C to obtain an anode D-2 (electrode).Preparation of anode film D-3

[0103] 50 % by weight of the second mixture was subjected to first calendering through a first set of rollers (101) and third set of rollers (103) at a roller gap of 250 - 350 pm, at a roller speed of 0. 1 to 0.6 m / min, a differential roller speed of 70 to 80%, and a roller temperature in a range of 140 to 160 °C to obtain first films A3 and A3’. The first films A3 and A3’ were then subjected to second calendering through a second and fourth set of rollers respectively, under the below conditions:

[0104] The first film A3 and A3’ were subjected to second calendering through a first pair of rollers in a second and a fourth set of rollers respectively, wherein a pair of rollers having roller force adjusted at 17-24 kN, at roller speed of 0.4 - 1.0 m / min, at differential roller speed of 72 to 80%, and at a roller temp of 140- 160 °C to obtain second films B3 and B3 ’ .

[0105] The obtained second films B and B’ were subjected to second calendering through the second pair of rollers in the second set of rollers (102) and the fourth set of rollers (104) respectively, wherein the subsequent pair of rollers are at a roller force of 17kN - 24 kN, at roller speed of 0.4 - 1.0 m / min, at a differential roller speed of 72-80%, and at a roller temperature of 140- 160 °C to obtain the anode film D3 and D3 ’ each having a density of 2.0 g / cc and a thickness of 92 pm each.

[0106] The anode films D3 and D3 ’ were then simultaneously laminated on both sides of a copper current collector using the last roller of the second set of rollers (102) and the last roller of the fourth set of rollers (104) with roller force adjustedto 25kN - 35 kN, at a roller speed of 0.3 - 1.0 m / min and at a roller temperature of 140- 160 °C to obtain an anode (electrode) D-3.

[0107] Similarly, the anodes were prepared with varying electrode densities and porosities. The below table 1 depicts the porosity, electrode density, active material mass loading, and peel strength exhibited by the anode comprising the anode films Dl-Dl’, D2-D2’ and D3-D3’ each prepared by the process as explained above by varying the second calendering step and passing through the set of rollers.

[0108] Table 1

[0109] The DI and DI’ anode films were obtained by a single first calendaring process. The D2-D2’ and D3-D3’ anode films were obtained by first calendaring and second calendering process. Compared to D2-D2’ anode films, the roller force applied in the calendaring process was higher in D3-D3’ anode film preparation. The porosity of the D3-D3’ anode films was found to be -11.3%, which was very low and had a very high Macmullin number.

[0110] The Macmullin Number (Nm) provides an indication of ionic mobility. The anode films D2-D2’ had a Nm value of 17.6 and D3-D3’ had Nm value of 26.9. It was understood that lower the Nm, higher the ionic mobility and conductivity. D2 and D2’ anode films possessed a lower Nm than D3 and D3’, hence the conductivity was found to be higher for D2 and D2’ . According to the present disclosure, the D2 and D2’anode films were found to be the electrode films with highest peel strength, conductivity, porosity, and density. The D2 and D2’ anode films with the density of 1.79 g / cc and a thickness of 92 pm, provided an optimum porosity of 20.4%.Preparation of cathode filmsPreparation of cathode film C-l

[0111] About 97.2% (w / w) of NMC-811 (nickel manganese cobalt in 8: 1: 1 ratio; anode active material) was pre-mixed with 1% (w / w) of Ketjen black and 0.3% (w / w) of KS6L (conductive additives) to obtain a first mixture. The first mixture was then high shear mixed with 1.5% (w / w) of polytetrafluoroethylene (fibrillating binder) to obtain a second mixture. The second mixture was cooled with low-speed mixing at a tip speed in a range of 12.25 m / s to a temperature below 19°C. The cooled second mixture was then jet milled at a feeding pressure of 2 kg / cm2; a milling pressure in a range of 2 kg / cm2; and at a temperature of20°C. The jet milled second mixture was separated into two parts- first part and second part (in 50:50 weight percentage ratio). The first part and second part of second mixture were subjected to first calendering through a first set of rollers (101) and third set of rollers (103) respectively, wherein each set of rollers having a constant roller gap of 250 - 350 pm, differential roller speed of 40 to 88% and roller temperature of 120-180 °C to obtain first film A4 and A4’ . The first films A4 and A4’were separately subjected to second calendering through a first pair of rollers each of second set of rollers (102) and fourth set of rollers (104) wherein the first pair of rollers were at a constant roller force of 12kN - 15kN, differential roller speed of 70-80% and roller temperature of 20-180 °C to obtain second films B4 and B4’ respectively. The second films B4 and B4’ were subsequently second calendered using a second pair of rollers each of second set of rollers (102) and fourth set of rollers (104) at a constant roller force of 12kN - 18 kN, a roller speed of 0.4 - 1 m / min, a differential roller speed of 70 to 80% and roller temperature of 120-180 °C to obtain third films C4 and C4’ . The third films C4 and C4’were then passed through a third pair of rollers the each of second set of rollers (102) and fourth set of rollers (104) in force- controlled mode at a constant roller force of 12kN - 18 kN, roller speed of 0.6 - 1.5 m / min, at differential roller speed of 70 to 80% and at roller temperature of 120- 180 °C to obtain the cathode films Cl and Cl’. The density of cathode films were found to be about 3.8 g / cc.

[0112] The cathodic films Cl and Cl’ were laminated upon both sides of an aluminium current collector using the last roller of the second set of rollers (102) and the last roller of the fourth set of rollers (104) with roller force adjusted to roller force of 15kN - 30 kN, at roller speed of 0.2 - 0.8m / min, and at roller temperature of 120 - 180 °C to obtain a cathode C-l (electrode).Preparation of cathode film C-0

[0113] For comparative purposes, a conventional cathode film was prepared by premixing 97.2% (w / w) of NMC-811 (nickel manganese cobalt in 8: 1: 1 ratio; anode active material) with 1% (w / w) of Ketjen black and 0.3% (w / w) of KS6L (conductive additives) to obtain a first mixture. The first mixture was then high shear mixed with 1.5% (w / w) of polytetrafluoroethylene (fibrillating binder) to obtain a second mixture. The second mixture was cooled with low-speed mixing at a tip speed in a range of 12.25 m / s to atemperature below 19°C. The cooled second mixture was then jet milled at a feeding pressure of 2 kg / cm2; a milling pressure in a range of 2 kg / cm2; and at a temperature of 20°C. The jet milled second mixture was separated into two parts- first part and second part (in 50:50 weight percentage ratio). The first part and second part of second mixture were calendered at a constant roller gap of 70 - 250 pm, at a roller speed 0.1- 1 m / min differential roller speed of 40-88% and roller temperature of 120-180 °C to obtain a cathode films CO and CO’. However, the density of the cathode films CO-CO’obtained was found to be ~2.5 g / cc, which was lesser than that of cathode films Cl -Cl ’. The obtained cathode films CO and CO’ were laminated on both sides of an aluminium current collector to obtain cathode C-0.

[0114] The below table 2 illustrates the cathode sample prepared by the process as explained with the porosity, electrode density, active material mass loading of the cathode film and peel strength.

[0115] Table 2Preparation of full cell (electrochemical cell)

[0116] A full electrochemical cell (pouch) was fabricated with the anode D-3 and cathode C-l prepared by the aforementioned process. The anode having a mass loading of 16.59 mg / cm2, anode density of 1.79 g / cc, and electrode porosity of 20.4% was placed along one side of an electrolyte comprising 12.31 wt.% of LiPFr, dissolved in a solution of 33.95% (w / w) of ethylene carbonate (EC), 26.21% (w / w) of ethyl methyl carbonate (EMC), and 27.53% (w / w) of dimethyl carbonate (DMC).

[0117] The cathode having active mass loading of 25.57 mg / cm2, electrode density of 3.80 g / cc and electrode porosity of 17.3%, was disposed on the other side of the electrolyte to obtain a full electrochemical cell.EXAMPLE 2Scanning electron microscopic (SEM) analysis

[0118] The structural-morphological analysis of the obtained anodes D-l, D-2, D- 3, conventional cathode C-0 and cathode C-l were carried out using scanning electron microscopic technique. The surface (Figure 2A a(i), b(i) and c(i)), and cross-sectional (Figure 2A a(ii), b(ii), and c(ii), SEM images of the anodes D-l, D- 2, and D-3, are depicted in Figure 2A. In the SEM images of anodes, the mechanical stability of the anode in terms of peel strength and thin / dense fibrillation was found to be improved with electrode density. In Figure 2A (a), it was clearly seen that the PTFE fibrils were non-uniform, thick and possessed poor particle-to-particle adhesion. However, improved fibrillization, in terms of uniformity and density of PTFE fibrils was observed in the SEM images of anodes D-2 and D-3 (Figure 2A b-c) and that of cathode C-l (Figure 2B). In comparison with the cathode C-0, the cathode C-l obtained by the process as disclosed in the present disclosure. As depicted in Figure 2B, the image (i) and (ii) represents the surface and cross- sectional images of cathode C-0 obtained by the first calendering process. The images showed that the conventional cathode C-0 was non-uniform. The electrodecomponents were found to be not distributed uniformly, and the compactness of the particles were observed to be less in the C-0 cathode. The loosely bound material and the non-uniform C-0 cathode resulted in a reduced electrode density, energy density, and columbic efficiency.

[0119] The improvement in fibrillization was found to be responsible for enhancing peel strength and cohesion between the consecutive particles. This was attributed to the increased compactness of the particles to achieve higher electrode density. Therefore, the density and uniformity of PTFE fibrils was found to be increased with the density of the anode and cathode films as shown in Tables 1 and 2.

[0120] The SEM results corresponding to D-2 anode was hence in alignment with the physical properties displayed in table 1. Higher electrode density offered benefits in terms of physical properties of the electrode as depicted in tables 1 and 2. It enhanced the structural integrity, making the electrode more mechanically robust due to thin and dense PTFE fibrillation resulting in better adhesion and thereby enhance peel strength as shown in SEM images of anode D-2 (Figure 2A b) and cathode C-l (Figure 2B). Better adhesion between electrode film and current collector was understood to result in improved electrochemical performance during cycling.

[0121] The SEM image of D-3 showed that the electrode components of the anode film were arranged in a very compact manner and hence the porosity was found to be poor. The reduced porosity was expected to detrimentally affect the ion mobility. Electrochemical analysis a. Specific capacity analysis

[0122] The obtained anodes D-l, D-2, and D-3 were analysed for their electrochemical performance in an electrolyte of 12.31 wt.% of LiPFr, dissolved in a solution of 33.95% (w / w) of ethylene carbonate (EC), 26.21% (w / w) of ethyl methyl carbonate (EMC), and 27.53% (w / w) of dimethyl carbonate (DMC). The Figure 3 depicts the specific capacity of the various anodes. The specific capacity plot as depicted in Figure 3 illustrated that the specific capacity for the D-2 anode was 345.1 mAh / g and has an initial coulombic efficiency (ICE) of 92.20%. For the anodes D-l and D-3, ICE is 83.03% and 90.43% respectively. It was observed that the anode D-2 obtained by first calendering and second calendering where rollergap was fixed and adjusted so as to achieve a porosity in a range of 18 to 22% and a density in a range of 1 to 2 g / cc provided highest specific capacity of 345. 1 mAh / g and ICE of 92.20%.

[0123] The obtained cathode C-l was analysed for their electrochemical performance in an electrolyte of 12.31 wt% of LiPFr, dissolved in EC / EMC / DMC in a weight ratio of 33.95:26.21:27.53. The cathode sample C-l which had porosity of 18.6% and yet possessed better electrode density of 3.8g / cc exhibited an appreciable ICE of 92.96% with a specific capacity of 213 mAh / g as depicted in Figure 5 (a).

[0124] The cathode films Cl and Cl’ were obtained by the process as explained in Example 1. The cathode C-l having an electrode density of ~3.8 g / cc, porosity of -18.6% and thickness of ~71pm was found to exhibit better electrochemical performance than the C-0 cathode. b. Life Cycle Analysis

[0125] The stability of the anodes (D-l, D-2, and D-3) were analysed by life cycle analysis by electrochemical cycling of each anode in an electrolyte of 1 M LiPFr,. EC:EMC:DMC (1: 1 : 1) Figure 4 (b) depicts the state of health (SoH) graph for the anodes D-l and D-2. The graph shows the comparative stability of the anodes D-l and D-2 to signify the role of force controlled multi-step calendering adopted to achieve optimally porous and dense anode D-2 which resulted not only higher ICE % value, but also in a stabilized electrochemical performance as shown herein. The anode D-2 exhibited a SoH of 80% at 27 cycles.

[0126] The cathode sample Cl which had porosity in a range of 17.5 - 21% and yet possessed better electrode density of 3.8g / cc exhibited an appreciably better state of health (SoH) of up to 83.62% at 50thcycle as depicted in Figure 5 (b).

[0127] The electrochemical properties of the anodes obtained by the above- mentioned process at various densities are comparatively tabulated in the below table 3. The initial columbic efficiency (ICE) and state of health (SoH) of the anodeswere determined to analyse their electrochemical performance and the stability of the anodes.

[0128] Table 3

[0129] The anode D-2 which had porosity of 20.4% and electrode density of 1.79 g / cc exhibited the maximum energy density of 61.4mWh / g and initial columbic efficiency (ICE) of 92.2%. Furthermore, the anode D-2 also exhibited better state of health (SoH) of 80% at 27thcycle. In comparison to the anode D-3 having lesser porosity and higher electrode density, the anode D-2 showed comparatively moderate peel strength of 0.035 Kgf as shown in table 1. Therefore, it was identified that the process as explained herein advantageously provided anode films having optimised porosity in a range of 18.0 -22.0 % and an electrode density in a range of 1.75-1.85 g / cc to result in enhanced and stabilized electrochemical performance.

[0130] The full electrochemical cell was analysed for its electrochemical performance via charge -discharge cycling and life cycle analysis.

[0131] The charge-dischaige cycle graph of the full electrochemical cell showed enhanced specific capacity and better electrochemical performance as shown in Figure 6(a). The cell exhibited a specific capacity of 198 mAh / g at a potential window of 3.6V. The initial capacity test was carried out at a charging C-rate of 0.1C and a discharging rate of 0.1C. From the initial capacity analysis, the ICE obtained was of > 90% was obtained. In order to measure the capacity retention of the cell, the charging and dischaiging C-rates were 0.5C / 1C respectively. From the life cycle curve, it is evident that a retention of >90% was obtained after 300 cycles at 25 °C.

[0132] The life-cycle data of the full electrochemical cell is shown in Figure 6(b). The state of health was found to be 92% after 300thcycle.ADVANTAGES OF THE PRESENT DISCLOSURE

[0133] The process of the present disclosure provides an electrode with optimum porosity and density to result in enhanced electrochemical performance. At optimum electrode density, the compactness between the active material particles improves as well as good adhesion between film and current collector is achieved. This is due to thin / dense fibrillation, resulting in enhanced ion / electronic diffusion ability within the electrode. The dry processing as explained by the present disclosure is practically convenient and scalable to a higher extend to achieve optimally performing electrodes. A full electrochemical cell wherein both cathode and anode are prepared by the multi-step calendering (first and second calendering) process of the present disclosure resulted in achieving better cycling stability and higher specific capacity than the cells having conventionally prepared dry electrodes. Furthermore, the electrodes of the present disclosure, both anode and cathode prepared by the process as disclosed herein achieves a better electrode density with enhanced porosity despite using low quantity of binder contents.

Claims

I / We Claim:

1. A process for preparing an electrode film, the process comprising: a. pre-mixing an active material with at least one conductive additive and a non-fibrillating binder to obtain a first mixture; b. adding a fibrillating binder to the first mixture followed by high shear mixing to obtain a second mixture; c. first calendering the second mixture through a first set of rollers (101) having a roller gap in a range of 100 to 400 pm, and at a differential roller speed in a range of 40 to 88% to obtain a first film ; and d. second calendering the first film through a second set of rollers (102) at a roller force in a range of 12 to 25 kN, at a differential roller speed in a range of 70 to 80%, to obtain an electrode film, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

2. The process as claimed in claim 1, wherein the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the second set of rollers (102) comprises ‘n’ number of rollers wherein each roller rotates in a progressively increasing roller speed; ‘m’ is in a range of 2 to 5; and ‘n’ is in a range of 2 to 10.

3. The process as claimed in claim 1, wherein the first set of rollers (101) and the second set of rollers (102), independently rotate at a speed in a range of at a roller speed in a range of 0.5 to 25 m / min.

4. The process as claimed in claim 1, wherein the first set of rollers (101) and the second set of rollers (102) have a roller temperature in a range of 100 to 200 °C.

5. The process as claimed in claim 1, wherein the active material is in a weight range of 96 to 99% (w / w) and is selected from natural graphite, synthetic graphite, silicon, silicon-graphite, nickel-manganese-cobalt oxide (NMC), lithium-nickel-cobalt-aluminium oxides (NCA), lithium iron phosphate (LFP), or lithium-manganese-rich (LMR).

6. The process as claimed in claim 1, wherein the at least one conductive additive is in a weight range of 0.5 to 2% (w / w) and is selected from carbon black, graphene, mesoporous carbon, acetylene black, activated carbon, super P, carbon nanofiber, vapour grown carbon nanofiber, carbon nanotube, or combinations thereof.

7. The process as claimed in claim 1, wherein the fibrillating binder is in a weight range of 0.5 to 3% (w / w) and is selected from polytetrafluoroethylene (PTFE), fluoroethylene vinyl ether (FEVE), fluoroethylene polymer (FEP), or combinations thereof.

8. The process as claimed in claim 1, wherein the non -fibrillating binder is in a weight range of 0.5 to 3% (w / w) and is selected from polyvinylidene fluoride (PVDF), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (Na- CMC), carboxymethyl cellulose (CMC), styrene butadiene rubber, polyethylene glycol (PEG), polyacrylic acid (PAA), polyethylene oxide (PEO), poly vinyl pyrrolidone (PVP), poly(vinylidene fluoride-co- hexafluoropropylene) (PVDF-HFP), or combinations thereof.

9. The process as claimed in claim 1, wherein high shear mixing is carried out at a tip speed in a range of 30 to 41m / s, for a period in a range of 5 to 60 minutes, until temperature of the mixture is in a range of 65 to 85 °C.

10. The process as claimed in claim 1, wherein the second mixture is cooled to a temperature below 19°C followed by jet milling, prior to first calendering.

11. The process as claimed in claim 1, wherein the process further comprises laminating the electrode film upon a current collector to obtain an electrode.

12. An electrode film obtained by the process as claimed in claim 1, the electrode film comprising: a. an active material; b. at least one conductive additive; and c. at least one binder, wherein the electrode film has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

13. The electrode film as claimed in claim 12, wherein at least one binder is selected from a fibrillating binder, a non-fibrillating binder or combinations thereof.

14. The electrode film as claimed in claim 12, wherein the electrode film has an aerial loading in a range of 10 to 30 mg / cm2.

15. The electrode film as claimed in claim 12, wherein the electrode film has a porosity in a range of 18 to 22% and a density in a range of 1 to 2 g / cc, when the electrode film is an anode film.

16. The electrode film as claimed in claim 15, wherein the electrode film exhibits a specific capacity in a range of 340 to 360 mAh / g.

17. The electrode film as claimed in claim 12, wherein the electrode film has a porosity in a range of 17 to 21% and a density in a range of 3 to 4 g / cc, when the electrode film is a cathode film.

18. The electrode film as claimed in claim 17, wherein the electrode film exhibits a specific capacity in a range of 205 to 215 mAh / g.

19. An electrode comprising the electrode film as claimed in any one of the claims 12 to 18, laminated on one side or both sides of a current collector.

20. A method of preparing an electrode as claimed in claim 19, the method comprising: a. obtaining a mixture comprising an active material, at least one conductive additive, a non-fibrillating binder, and a fibrillating binder; b. allowing a first part of the mixture from input A to pass through a first set of rollers (101) for first calendering to obtain a first film A, and allowing a second part of the mixture from input A’ to pass through a third set of rollers (103) for first calendering to obtain a first film A’ ; c. second calendering the first film A through a second set of rollers (102) to obtain a second film B and second calendering the first film A’ through a fourth set of rollers (104) to obtain a second film B’; and d. simultaneously laminating the second film B and the second film B’ on a current collector to obtain the electrode,wherein the electrode has a porosity in a range of 17 to 22% and a density in a range of 1.7 to 3.9 g / cc.

21. The method as claimed in claim 20, wherein the first set of rollers (101) is placed at input A near proximal end; the second set of rollers (102) is placed successive to the first set of rollers (101); the third set of rollers (103) is placed at input A’ near distal end; the fourth set of rollers (104) is placed successive to the third set of rollers (103); and the last roller of the second set of rollers (102) meet the last roller of the fourth set of rollers (104) at the center.

22. The method as claimed in claim 20, wherein the first set of rollers (101) and the third set of rollers (103) have a roller gap in a range of 100 to 400 pm and rotate at a differential roller speed in a range of 40 to 88%.

23. The method as claimed in claim 20, wherein the second set of rollers (102) and the fourth set of rollers (104) exert a roller force upon the first film in a range of 12 to 25 kN and rotate at a differential roller speed in a range of 70 to 80%.

24. The method as claimed in claim 20, wherein the first set of rollers (101) comprises ‘m’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the second set of rollers (102) comprises ‘n’ number of rollers wherein each roller rotates in a progressively increasing roller speed; the third set of rollers (103) comprises ‘o’ number of rollers wherein each pair of rollers has a progressively decreasing roller gap; the fourth set of rollers (104) comprises ‘p’ number of rollers wherein each roller rotates in a progressively increasing roller speed; ‘m’ and ‘o’ are in a range of 2 to 5; and ‘n’ and ‘p’ are in a range of 2 to 10.

25. The method as claimed in claim 20, wherein the mixture is obtained by premixing an active material with at least one conductive additive and a non- fibrillating binder followed by high shear mixing with a fibrillating binder.

26. The method as claimed in claim 20, wherein the last roller of the second set of rollers (102) and the last roller of the fourth set of rollers (104) rotate in the same rotating speed, in a range of 0.5 to 25 m / min.

27. A first electrochemical cell comprising:a. a cathode; b. an anode comprising the electrode film as claimed in claim 15; and c. an electrolyte.

28. A second electrochemical cell comprising: a. a cathode comprising the electrode film as claimed in claim 17; b. an anode; and c. an electrolyte.

29. A third electrochemical cell comprising: a. an anode comprising the electrode film as claimed in claim 15; b. a cathode comprising the electrode film as claimed in claim 17; and c. an electrolyte.

30. The electrochemical cell as claimed in any one of the claims 27 to 29, wherein the electrolyte is selected from LiPFr, or LiBF4 dissolved in a solvent selected from ethyl carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), vinylene carbonate (VC), 1, 3-propane sultone (PS), succinonitrile (SN), or combinations thereof.

31. Use of the electrode film as claimed in any one of the claims 12 to 18 or the electrode as claimed in claim 19, as a working electrode in an electrochemical cell.

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