A cathode composite, a lithium-ion battery and processes thereof

Abstract

The present disclosure provides a cathode composite comprising: (i) an active material; (ii) at least one primary carbon; (iii) at least one secondary carbon; and (iv) at least one binder, wherein the primary carbon is coated on the active material, and the secondary carbon is coated on the primary carbon; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

Description

A CATHODE COMPOSITE, A LITHIUM-ION BATTERY AND PROCESSES THEREOFFIELD OF INVENTION

[0001] The present disclosure broadly relates to the field of battery. Particularly, the present disclosure relates to a dry electrode composite and a process for preparing the electrode composite. Particularly, the present disclosure relates to a cathode composite.BACKGROUND OF THE INVENTION

[0002] Dry electrodes are prepared without the use of liquid solvents or binders, focusing on solid-state materials to enhance battery performance. They reduce the manufacturing complexity and environmental impact associated with traditional wet coating processes. By eliminating solvents, dry electrodes can achieve a higher energy density and lighter weight, which are crucial for applications in electric vehicles and portable electronics. Additionally, dry electrodes often exhibit improved structural integrity and longer cycling stability, making them a promising alternative in the development of next-generation energy storage devices.

[0003] Among the various strategies, the employment of two types of carbon along with the active material in cathode composites of dry electrodes had led to the enhancement of electrochemical performance. However, these dry electrodes utilized in battery systems face significant limitations when it comes to performance, particularly at higher C-rates. This performance deficiency is primarily attributed to the inherent low electrical resistance of the cathode. While dry electrodes are designed to minimize weight and rely on solid-state materials, this design can lead to development of internal electrical resistance within the cathode. When subjected to higher C-rates, where rapid ion and electron transport is required, the increased resistance can hinder the overall electrochemical performance of the battery. Additionally, elevated temperature conditions exacerbate this issue. As temperature rises, the mobility of ions may increase, but the conductivity of many dry electrode materials does not vary in this manner. Thiswill lead to a mismatch in ionic and electronic transport pathways. This discrepancy can result in a decrease in efficiency, elevated heat generation, and potential thermal degradation of the materials, resulting in diminished overall performance and cycle life of the battery.

[0004] Even though, dry electrodes hold great promise for energy storage technology, their performance at higher C-rates is limited by the combination of low electrical conductivity and temperature-related effects.

[0005] Thus, there is a dire need in the art to develop cost-effective, cathodes with high-rate performance, enhanced electronic conductivity, improved electrochemical properties, and better electrical resistance at high C rates even at extreme temperature conditions.SUMMARY OF THE INVENTION

[0006] In an aspect of the present disclosure, there is provided a cathode composite comprising: (i) an active material; (ii) at least one primary carbon; (iii) at least one secondary carbon; and (iv) at least one binder, wherein the primary carbon is coated on the active material, and the secondary carbon is coated on the primary carbon; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

[0007] In another aspect of the present disclosure, there is provided a process for preparation of the cathode composite as disclosed herein, the process comprising: (i) mixing an active material, a primary carbon, and a secondary carbon to obtain a first mixture; (ii) blending the first mixture with a fibrillating binder and an adhesive binder followed by high shear mixing to obtain a second mixture; and (iii) cooling the second mixture to a temperature in a range of 10 to 19°C to obtain the dry cathode composite, wherein the mixing is carried out at a tip speed in a range 15 to 40 m / s, at a temperature range of 10 to 25°C, and for a period in a range of 65 to 85 minutes.

[0008] In yet another aspect of the present disclosure, there is provided a dry cathode composite prepared by the process as disclosed herein.

[0009] In still another aspect of the present disclosure, there is provided a cathode comprising the cathode composite as disclosed herein, coated on a current collector.

[0010] In another aspect of the present disclosure, there is provided a lithium-ion battery comprising: (a) the cathode as disclosed herein; (b) an anode; and (c) an electrolyte.

[0011] 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

[0012] 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.

[0013] Figure 1 depicts the scanning electron microscopic (SEM) images of cathode composite SI having varied mixing time for carbons and active material, wherein (a) 15 minutes; (b) 30 minutes; (c) 45 minutes; (d) 60 minutes; (e) 120 minutes; (f) 105 minutes; (g) 90 minutes; and (h) 75 minutes, in accordance with an embodiment of the present disclosure.

[0014] Figure 2 depicts the SEM images of cathode composite S2 having varied mixing time for carbons and active material, wherein (a) 15 minutes; (b) 30 minutes; (c) 45 minutes; (d) 60 minutes; (e) 120 minutes; (f) 105 minutes; (g) 90 minutes; and (h) 75 minutes, in accordance with an embodiment of the present disclosure.

[0015] Figure 3 depicts zoomed out (a, b) and zoomed in (c, d) SEM images of first mixtures for preparing cathodes composite SI (a, c) and S2 (b, d), in accordance with an embodiment of the present disclosure.

[0016] Figure 4 depicts the zoomed out (a, b) and zoomed in (c, d) SEM images of adhesive binder added first mixtures for preparing cathodes composite SI (a, c) and S2 (b, d) , in accordance with an embodiment of the present disclosure.

[0017] Figure 5 depicts the zoomed out (a, b) and zoomed in (c, d) SEM images of second mixture for preparing cathodes composites SI (a) and S2 (b), in accordance with an embodiment of the present disclosure.

[0018] Figure 6 depicts the zoomed out (a, b) and zoomed in (c, d) SEM images of cathode composites S 1 (a) and S2 (b) after high shear mixing, in accordance with an embodiment of the present disclosure.

[0019] Figure 7 depicts the SEM images of the surface view of cathodes composite SI (a) and S2 (b), in accordance with an embodiment of the present disclosure.

[0020] Figure 8 depicts the SEM images of the cross-sectional view of cathode composites SI (a) and S2 (b), in accordance with an embodiment of the present disclosure.

[0021] Figure 9 (a, b, c and d) depicts the transmission electron microscopic (TEM) images of cathode composite SI, in accordance with an embodiment of the present disclosure.

[0022] Figure 10 (a, b, c and d) depicts the TEM images of the cathode composite S2, in accordance with an embodiment of the present disclosure.

[0023] Figure 11 depicts the discharge capacities exhibited by cathode composites SI, S2 and S3 at 1C, 2C, and 3C rates, in accordance with an embodiment of the present disclosure.

[0024] Figure 12 depicts the electrical resistances exhibited by cathode composites SI, S2, and S3 in accordance with an embodiment of the present disclosure.

[0025] Figure 13 depicts the capacity retention of cathodes Cl and C2 at 25°C (a) and 45°C (b) , in accordance with an embodiment of the present disclosure.

[0026] Figure 14 depicts the initial coulombic efficiency (ICE) values for electrochemical cells El and E2, in accordance with an embodiment of the present disclosure.

[0027] Figure 15 depicts the discharge capacities for electrochemical cells El and E2, in accordance with an embodiment of the present disclosure.

[0028] Figure 16 depicts the discharge capacities for electrochemical cells El and E2 at (a) 1C, (b) 2C, and (c) 3C rates, in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0029] 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

[0030] 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.

[0031] 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.

[0032] 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”.

[0033] 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.

[0034] The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.

[0035] The term “w / w” means the percentage by weight, relative to the weight of the total composition, unless otherwise specified.

[0036] The term "at least one" is used to mean one or more and thus includes individual components as well as mixtures / combinations.

[0037] The term “current collector” refers to the electric bridging component, which collects electrical current generated at the electrodes of electrochemical devices and connect with external circuits. In an aspect of the present disclosure, the current collector include but not limited to aluminium foil, glossy aluminium foils, carbon or polymer pre-coated aluminium foil or combinations thereof.

[0038] The term “surface area”, as used in refers to the area of the surface or exposed portion of a material, particles or structures. In an aspect of the present disclosure, surface area of primary carbon in a range of 800 to 1800 m2 / g.

[0039] The term “cathode composite” refers to a composite material used in a cathode which is a dry battery electrode wherein the composite material acts as the component for aiding the electrochemical reaction. In an aspect of the present disclosure, the cathode composite comprises: (i) an active material; (ii) at least one primary carbon; (iii) at least one secondary carbon; and (iv) at least one binder.

[0040] The term “active material” refers to the component within a battery's cathode that undergoes electrochemical reactions to store and release energy, specifically, during the charge and discharge cycles of lithium-ion batteries. In an aspect of the present disclosure, the active material is selected from lithium nickel manganese cobalt oxides, lithium oxides, lithium iron phosphates, or combinations thereof.

[0041] The term “primary carbon” refers to a carbon-based additive having high surface area, and porosity, which is added to an electrode composition to enhance the conductivity of the composite material. In the present disclosure, the primary carbon is selected from carbon black (such as Ketjen black), acetylene black, amorphous carbon black, or combinations thereof.

[0042] The term “secondary carbon” refers to graphitic carbon with layered hexagonal lattice added to work synergistically with primary carbon additives to enhance the performance of the cathode composite by efficient electron transport and by contributing to structural stability. In an aspect of the present disclosure, thesecondary carbon is selected from graphite, graphene, KS6L, or combinations thereof.

[0043] The term “binder” refers to the material used to hold the active materials and conductive additives together, ensuring structural integrity and cohesion within the electrode composite during the charge and discharge cycles of a battery. It facilitates the adhesion between the active materials and the current collector, which is essential for effective electron transfer. In an aspect of the present disclosure, the binder is selected from an adhesive binder, a fibrillating binder or combinations thereof; the adhesive binder is selected from polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof; and the fibrillating binder is selected from polytetrafluoroethylene, poly fluoroethylene, polyfluoroethylene vinyl ether or combinations thereof.

[0044] The term “porosity” refers to the presence and distribution of tiny pores or void spaces within the carbon material, which is characterized by parameters such as pore size, pore volume, and surface area, and it plays a critical role in determining the conductivity, accessibility, and storage capacity of the conductive carbon. In an aspect of the present disclosure, the primary carbon has a porosity in a range of 60 to 90%.

[0045] The term “electrical resistance” refers to the resistance exhibited by the cathode composite to the flow of electric current. In an aspect of the present disclosure, the composite exhibits an electric resistance in a range of 0.1 to 0.5 Q.

[0046] The term “tensile strength” refers to the largest force in weight per unit area tugging in the direction of length that a given substance can sustain without rupturing. Tensile strength is also described as the "resistance to lengthwise stress." A tensile test (or tension test) applies force to a material specimen in order to measure the material's response to tensile (or pulling) stress. A material either fully or partially cannot be reverted to its former shape and size once the stress approaches the tensile strength value. Force per unit area is a measure of tensile strength.

[0047] The term “mixing” refers to the process of combining the raw materials for the preparation of cathode composite into a homogenous mixture, where the raw materials may be subjected to mechanical forces. In an aspect of the present disclosure, there is provided a process of preparation of a cathode composite as disclosed herein, the process comprising mixing an active material, a primary carbon, and a secondary carbon at a tip speed in a range 10 to 15 m / s, at a temperature range of 10 to 25 °C, and for a period in a range of 65 to 85 minutes to obtain a first mixture.

[0048] The term “blending” refers to the process of combining two or more different materials or mixtures to create a new, homogeneous mixture. In electrode materials, blending can be used to create a composite material that combines the benefits of individual components, such as improved conductivity, enhanced surface area, or increased stability. In an aspect of the present disclosure, blending is performed at a tip speed in a range of 10 to 20 m / s, a temperature range of 10 to 19 °C, and for a period in a range of 15 to 40 minutes.

[0049] The term “high shear mixing” refers to a mixing process that uses highspeed agitation to create a uniform dispersion of materials by applying intense shear forces. In an aspect of the present disclosure, high shear mixing is carried out at a tip speed in a range of 10 to 15 m / s, and a temperature in a range of 60 to 80 °C.

[0050] The term “calendered” refers to the process of laying a material onto the surface of a substrate such as a current collector to form a uniformly dense electrode layer. This process involves passing the coated current collector through a series of rollers or calendering machines, which apply pressure and heat to flatten and compress the electrode material into a thin, consistent film. In an aspect of the present disclosure, calendering is carried out at a temperature in a range of 60 to 150 °C.

[0051] The term “laminated” refers to the process in which a layer of cathode composite is applied and bonded to a current collector. This technique can enhance the performance, structure, and manufacturing efficiency of the electrode assembly. In an aspect of the present disclosure, laminating is carried out at a temperature in a range of 60 to 150 °C.

[0052] The term “Initial Coulombic Efficiency” or “ICE” refers to the ratio of the charge capacity of a battery during its first charge cycle to the discharge capacity during the same cycle, expressed as a percentage. In an aspect of the present disclosure, cathode exhibits an initial coulombic efficiency in a range of 89 to 95%.

[0053] The term “discharge capacity” refers to the maximum amount of electric charge that an electrode can release or deliver during a single discharge cycle. It is a measure of the electrode's ability to provide electrical energy and is typically expressed in terms of the capacity per unit area (e.g., mAh / cm2). In an aspect of the present disclosure, the cathode comprising the cathode composite as disclosed herein exhibits a discharge capacity in a range of 190 to 250 mAh.

[0054] The term “C-rate” refers to the rate at which a battery is charged and discharged. 1C means that the battery is fully charged and discharged within one hour, 2C is 30 minutes, 10C is 6 mins, 100C is 6 seconds.

[0055] The term “capacity retention” refers to the ability of an electrode or an electrochemical cell, to maintain its operational capacity under defined charge and discharge cycling conditions and over extended periods. It is used for assessing the longevity and performance stability of the device. It is expressed as a percentage of the initial capacity. The electrochemical cell of the present disclosure exhibits a capacity retention of 90 to 99.9%.

[0056] 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, temperature in the range of 10 to 19 °C should be interpreted to include not only the explicitly recited limits of 10 to 19 °C but also to include sub-ranges, such as 10 to 15 °C, 12 to 19°C and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 10.5 °C, 15.00 °C and 18.9

[0057] 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.

[0058] 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.

[0059] As discussed in the background, in order to enhance the electrochemical properties of cathode active materials (CAM), in the existing methodologies, a dual carbon coating approach has been employed. Specifically, an inner coating composed of amorphous carbon (Ketjen Black), and a graphitic outer layer (KS6L) is applied. Each coating has a nominal thickness in a range of 5 to 500 nm, and these carbon materials are designed to adhere effectively to one another and to the cathode active material's surface. However, the dense nature of these coatings hinders the binder material from penetrating the cathode active material surface adequately. This limited infiltration may restrict the electrical pathways necessary for optimal ion and electron transport, further exacerbating the overall electrical resistance of the system. Consequently, there exists a critical need to refine the carbon coating strategy to mitigate this resistance, thus enhancing the rate performance of the electrodes at high C-rates.

[0060] To achieve the objective, the present disclosure provides a modified cathode active material that is comprised of an active material coated with a primary and a secondary carbon, which has enhanced electrical conductivity crucial for rapid charge and discharge cycles. This modified cathode material has a rough coating of the carbon materials, wherein the primary and secondary carbons are arranged in non-uniform layers, yet the overall density is meticulously maintained. The optimization of this density, alongside the incorporation of a combination of fibrillating and adhesive binders, enables a significant improvement in theconductivity and overall electrochemical performance of the battery. Further, primary carbon possessing high surface area provides higher conductivity to the electrode film, whereas the secondary carbon having a lower surface area and lower conductivity provides lubrication to achieve flexible free standing electrode films. Furthermore, the rough coating is strategically achieved through precise control of the mixing process, optimized to 75 minutes. This careful optimization not only enhances the structural integrity of the electrode but also facilitates better ion transport. As a result, the present disclosure effectively mitigates the issues of high resistance and suboptimal performance in elevated temperature conditions, thereby providing a robust solution for improved battery efficiency and longevity.

[0061] Accordingly, in an embodiment of the present disclosure, there is provided a cathode composite comprising: (i) an active material; (ii) at least one primary carbon; (iii) at least one secondary carbon; and (iii) at least one binder, wherein the primary carbon is coated on the active material, and the secondary carbon is coated on the primary carbon; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm. In another embodiment of the present disclosure, the combined thickness of the primary carbon and the secondary carbon is in a range of 100 to 500 nm. In yet another embodiment of the present disclosure, the combined thickness of the primary carbon and the secondary carbon is in a range of 150 to 400 nm. In still another embodiment of the present disclosure, the combined thickness of the primary carbon and the secondary carbon is in a range of 200 to 300 nm.

[0062] In an embodiment of the present disclosure, there is provided acathode composite comprising: (i) 95 to 98% by weight of an active material; (ii) 1 to 2% by weight of at least one primary carbon; (iii) 0.1 to 1% by weight of at least one secondary carbon; and (iii) 1 to 3% by weight of at least one binder, wherein the primary carbon is coated on the active material, and the secondary carbon is coated on the primary carbon; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; andcombined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

[0063] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the primary carbon has a coating density in a range of 0.1 to 1 g / cc, a thickness in a range of 5 to 40 nm, and a thickness-to-mass ratio is in a range of 800 to 15000 nm / g.

[0064] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the layer of secondary carbon has a density in a range of 0.005 to 0.05 g / cc, a thickness in a range of 50 to 500 nm; and a thickness-to-mass ratio is in a range of 25000 to 40000 nm / g.

[0065] In an embodiment of the present disclosure, there is provided a cathode composite comprising: (i) an active material; (ii) at least one primary carbon; (iii) at least one secondary carbon; and (iii) at least one binder, wherein the primary carbon is coated on the active material with a coating density in a range of 0.1 to 1 g / cc, a thickness in a range of 5 to 40 nm, and a thickness-to-mass ratio is in a range of 800 to 15000 nm / g., and the secondary carbon is coated on the primary carbon with a density in a range of 0.005 to 0.05 g / cc, a thickness in a range of 50 to 500 nm; and a thickness-to-mass ratio is in a range of 25000 to 40000 nm / g; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

[0066] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the primary carbon has a porosity in a range of 60 to 90% and a surface area in a range of 800 to 1800 m2 / g.

[0067] In an embodiment of the present disclosure, there is provided a cathode composite comprising: (i) an active material; (ii) at least one primary carbon having a porosity in a range of 60 to 90% and a surface area in a range of 800 to 1800 m2 / g; (iii) at least one secondary carbon; and (iii) at least one binder, wherein the primary carbon is coated on the active material with a coating density in a range of 0.1 to 1 g / cc, a thickness in a range of 5 to 40 nm, and a thickness-to-mass ratio is in a range of 800 to 15000 nm / g, and the secondary carbon is coated on the primary carbonwith a density in a range of 0.005 to 0.05 g / cc, a thickness in a range of 50 to 500 nm; and a thickness-to-mass ratio is in a range of 25000 to 40000 nm / g; the coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and the combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

[0068] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the active material is selected from lithium nickel manganese cobalt oxides, lithium oxides, lithium iron phosphates, or combinations thereof; the primary carbon is selected from carbon black (ketjen black), acetylene black, amorphous carbon black, or combinations thereof; and the secondary carbon is selected from graphite, graphene, KS6L or combinations thereof.

[0069] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the binder is selected from an adhesive binder, a fibrillating binder or combinations thereof; the adhesive binder is selected from polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof; and the fibrillating binder is selected from polytetrafluoroethylene, poly fluoroethylene, polyfluoroethylene vinyl ether or combinations thereof.

[0070] In an embodiment of the present disclosure, there is provided a cathode composite comprising: (i) an active material selected from lithium nickel manganese cobalt, lithium oxides, lithium iron phosphates, or combinations thereof; (ii) at least one primary carbon selected from carbon black, ketjen black, acetylene black, amorphous carbon black, or combinations thereof; (iii) at least one secondary carbon selected from graphite, graphene, KS6L or combinations thereof; and (iii) at least one binder, wherein the binder is selected from an adhesive binder, a fibrillating binder or combinations thereof; the adhesive binder is selected from polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof; and the fibrillating binder is selected from polytetrafluoroethylene, poly fluoroethylene, polyfluoroethylene vinyl ether or combinations thereof, wherein the primary carbon is coated on the activematerial, and the secondary carbon is coated on the primary carbon; coating density of the primary carbon and the secondary carbon coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; and combined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

[0071] In an embodiment of the present disclosure, there is provided a cathode composite as disclosed herein, wherein the composite exhibits an electric resistance in a range of 0.1 to 0.5 Q.

[0072] In an embodiment of the present disclosure, there is provided a process for preparation of the cathode composite as disclosed herein, the process comprising: i) mixing an active material, a primary carbon, and a secondary carbon to obtain a first mixture; (ii) blending the first mixture with a fibrillating binder and an adhesive binder followed by high shear mixing to obtain a second mixture; and (iii) cooling the second mixture to a temperature in a range of 10 to 19 °C to obtain the dry cathode composite, wherein the mixing is carried out at a tip speed in a range 10 to 15 m / s, at a temperature range of 10 to 25 °C, and for a period in a range of 65 to 85 minutes.

[0073] In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the blending is performed at a tip speed in a range of 10 to 20 m / s, a temperature range of 10 to 19 °C, and for a period in a range of 15 to 40 minutes.

[0074] In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the high shear mixing is carried out at a tip speed in a range of 15 to 40 m / s, at a temperature in a range of 60 to 80 °C.

[0075] In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the cooling is carried out at a tip speed in a range of 3 to 10 m / s.

[0076] In an embodiment of the present disclosure, there is provided a process for preparation of the cathode composite as disclosed herein, the process comprising: i) mixing an active material, a primary carbon, and a secondary carbon to obtain a first mixture; (ii) blending the first mixture with a fibrillating binder and an adhesive binder at a tip speed in a range of 10 to 20 m / s, a temperature range of 10 to 19 °C,and for a period in a range of 15 to 40 minutes, followed by high shear mixing at a tip speed in a range of 10 to 15 m / s, at a temperature in a range of 60 to 80 °C, to obtain a second mixture; and (iii) cooling the second mixture at a tip speed in a range of 3 to 10 m / s to a temperature in a range of 10 to 19 °C to obtain the dry cathode composite, wherein the mixing is carried out at a tip speed in a range 10 to 15 m / s, at a temperature range of 10 to 25 °C, and for a period in a range of 65 to 85 minutes. In another embodiment of the present disclosure, the mixing is carried out at a tip speed in a range 20 to 35 m / s, at a temperature range of 10 to 20 °C, and for a period in a range of 70 to 80 minutes. In yet another embodiment of the present disclosure, the mixing is carried out at a tip speed in a range 30 to 31 m / s, at a temperature of 20 °C, and for a period in a range of 75 minutes.

[0077] In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the cathode composite is calendered and optionally laminated on a current collector at a temperature in a range of 60 to 150 °C.

[0078] In an embodiment of the present disclosure, there is provided a process as disclosed herein, wherein the current collector is selected from aluminium foil, aluminium sheet, or pre-coated aluminium sheet.

[0079] In an embodiment of the present disclosure, there is provided a process for preparation of the cathode composite as disclosed herein, the process comprising: i) mixing an active material, a primary carbon, and a secondary carbon to obtain a first mixture; (ii) blending the first mixture with a fibrillating binder and an adhesive binder at a tip speed in a range of 10 to 20 m / s, a temperature range of 10 to 19 °C, and for a period in a range of 15 to 40 minutes, followed by high shear mixing at a tip speed in a range of 10 to 15 m / s, at a temperature in a range of 60 to 80 °C, to obtain a second mixture; (iii) cooling the second mixture at a tip speed in a range of 3 to 10 m / s to a temperature in a range of 10 to 19 °C to obtain the dry cathode composite; (iv) calendering and optionally laminating the dry cathode composite on a current collector at a temperature in a range of 60 to 150 °C, wherein the current collector is selected from aluminium foil, aluminium sheet, or pre-coated aluminium sheet, wherein the mixing is carried out at a tip speed in a range 15 to40 m / s, at a temperature range of 10 to 25°C, and for a period in a range of 65 to 85 minutes.

[0080] In an embodiment of the present disclosure, there is provided a dry cathode composite prepared by the process as disclosed herein.

[0081] In an embodiment of the present disclosure, there is provided a cathode comprising the cathode composite as disclosed herein, coated on a current collector.

[0082] In an embodiment of the present disclosure, there is provided a cathode as disclosed herein, wherein the cathode exhibits an initial coulombic efficiency in a range of 89 to 95%, a discharge capacity in a range of 190 to 250 mAh / g; and a capacity retention in a range of 90 to 99.9%.

[0083] In an embodiment of the present disclosure, there is provided a lithium-ion battery comprising: (a) the cathode as disclosed herein; (b) an anode; and (c) an electrolyte.

[0084] Although the invention has been described with respect to a limited number of embodiments, the specific features of one embodiment are not attributable to those of other embodiments of the invention.EXAMPLES

[0085] 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 be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.Materials and Methods

[0086] The procurement details of various chemicals and solvents used in the present disclosure are as follows:1. Cathode active material NMC811 (lithium nickel manganese cobalt oxide)was procured from BASF.2. Primary carbon-ketjen black was procured from Noury on (porosity of 60 to 80%; surface area of 1400 m2 / g).3. Secondary carbon KS6L (synthetic graphite) was procured from Imerys (surface area of 20 m2 / g)4. Adhesive binder: polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) was procured from Arkema.5. Binder: polytetrafluoroethylene (PTFE) was procured from Daikin.6. Pre-coated aluminium Current collector was procured from BlueGlow Nano.EXAMPLE 1Preparation of the cathode composite

[0087] 96.2% by weight of lithium nickel manganese cobalt oxide (active material, AM), 1.38% by weight of Ketjen black (primary carbon (CC1)) and 0.42% by weight of KS6L (secondary carbon (CC2)), were mixed for 75 minutes in a Zeppelin mixture at a tip speed of 30 m / s, at a temperature of 20°C, to obtain a first mixture, where the coating density of the primary carbon and the secondary carbon coated over the active material is 0.07 g / cc; and the combined thickness of the primary carbon and the secondary carbon is 220 nm. 1% by weight of poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) (adhesive binder, Bl) and 1% by weight of polytetrafluoroethylene (PTFE) (fibrillating binder, B2) was added to the first mixture, and was subjected to blending at a tip speed of 15 m / s, at a temperature of 15°C for 30 minutes, followed by high shear mixing at a tip speed of 30 m / s, at a temperature of 75 °C to obtain a second mixture. The second mixture was cooled to a temperature of 15°C by stirring at a tip speed of 5 m / s, to obtain the dry cathode composite, S 1.

[0088] For comparative purposes, a dry cathode composite S2 was prepared by the process as described above, wherein the active material, CC1, and CC2 were mixed(in weight ranges as explained above) for 120 minutes in a Zeppelin mixture at a tip speed of 12 m / s, at a temperature of 20°C, to obtain a first mixture. The first mixture was then processed in a similar manner as described above to obtain dry cathode composite, S2.

[0089] Similarly, a dry cathode composite S3 was prepared by the process as described above, wherein the 96.2% of active material, 1% of CC1, and 0.3% of CC2 were mixed for 120 minutes in a Zeppelin mixture at a tip speed of 12 m / s, at a temperature of 20°C, to obtain a first mixture. The first mixture was then processed in a similar manner as described above to obtain dry cathode composite, S3.

[0090] The composition of the dry cathode composites SI, S2 and S3 are summarized in Table 1.Table 1EXAMPLE 2Characterization of the dry cathode compositeA. Scanning electron microscopic (SEM) analysis

[0091] The coating of primary and secondary carbon over the active material was analyzed using SEM technique. The SEM images of cathode composites, SI and S2 as prepared in Example 1, were taken and compared. The observations for firstmixtures at different mixing times were provided in Figure (la to Ih). Further, a zoomed-out SEM image of the above observations are shown in Figure (2a to 2h).

[0092] From the Figures Ih and 2h, it was obvious that the dry cathode composite, SI prepared by the process as explained in Example 1, wherein the time for mixing the active material with CC1 and CC2 was 75 minutes, exhibited dense coating with rough surface. There was no agglomeration observed confirming the improved conductivity network.

[0093] Further, from the Figure 3a and 3b, it was observed that, due to the reduced mixing time (75 minutes) of carbons CC1 and CC2 with the active material, the obtained first mixture had less dense coating of the carbons upon active material surface. The less dense and rough surface coating improved conductivity, enhanced rate performance and reduced electrical resistance. It was observed that when the mixing time was beyond 85 minutes (as observed for the first mixture for preparing the composite S2 where the mixing time was 120 minutes), a smooth coating was seen which led to decreased conductivity, and increased resistance. Further, it was noted that, below 65 mins, agglomeration of primary and secondary carbons was observed.

[0094] Furthermore, from the Figure 4a and 4b, it was found that, for first mixtures obtained while preparing composite SI (after adding PVDF-HFP and before adding PTFE), the binder PVDF-HFP was also coated with carbons due to their less dense deposition on the active material resulting in a rough surface. It was also seen that PVDF-HFP was uniformly distributed or decorated on active material particle surface in the mixture of SI compared to that of S2.

[0095] Similarly, from the Figure 5a and 5b, it was observed that, for the second mixtures obtained while preparing composite SI, where the mixing time was 75 minutes, PTFE particles were also coated with carbons in case of second mixture of SI. However, the carbon mixing / coating with the PTFE particles was not observed for the second mixture of S2.

[0096] In addition, from the Figure 6a and 6b, it was noted that, after high shear mixing was carried out, both the SI and S2 looked similar, where the PTFE micro fibrils were visible on both the composites SI and S2.

[0097] However, from the Figures 7a and 7b, CC1 was observed in between the PTFE fibrils for in the surface of the composite SI along with CC2. Meanwhile, CC2 alone was noticed on the surface of composite S2.

[0098] Furthermore, from the cross-sectional view of the composites SI and S2 as films coated upon an aluminium current collector in Figures 8a and 8b respectively, it was found that, CC1 was observed in between the PTFE fibrils for composite SI, while only CC2 was observed in composite S2.B. Transmission Electron Microscopic (TEM) analysis

[0099] The coating of primary and secondary carbons over the active material particles was analyzed using TEM. The TEM images of cathode composite comprising primary and secondary carbon coated over the active material by varying the mixing time were taken and compared.

[0100] From the Figures 9a, 9b, 9c, and 9d, it was noted that, for composite SI the coating layer of CC1 exhibited a thickness of 10 nm and the coating layer of CC2 exhibited a thickness of 100 nm.

[0101] Similarly, From the Figure 10a, 10b, 10c and lOd it was observed that, for S2, the coating layer of CC1 exhibited a thickness of 20nm and the coating layer of CC2 exhibited a thickness of 200nm.EXAMPLE 3Preparation of the cathode composite

[0102] The dry cathode composites, SI, S2 and S3 as prepared in Example 1 were roll-to-roll calendered to obtain a free-standing film at a roller temperature of 150°C, roller speed of 0.1-0.5 m / min, and roller gap of 200-300 pm. Further, lamination on to the current collector at a temperature of 150°C to obtain cathodes Cl, C2 and C3 respectively.Characterization of the cathodesTensile Strength

[0103] Tensile strength analysis was performed for the cathodes prepared as explained above.

[0104] The required length (200-250mm), width (25-30mm) and thickness (60 -80qm) of dry cathode was prepared for the tensile strength measurement. The prepared dry cathode was fixed in the fixtures, and the load was applied with crosssection speed of 12.5mm / min.

[0105] The tensile strength for the cathodes prepared using the cathode composites SI, S2 and S3 were tabulated (Table 2a. It was observed that, the cathode Cl comprising the cathode composite SI exhibited a tensile strength of 36.6 MPa. Peel strength analysis

[0106] Peel strength analysis is a conventional method in battery industry for ranking the adhesion strength of electrodes. For the test, a double-sided adhesive tape was first stuck onto the movable pull-off table. The composite to be tested was then glued to the adhesive tape. Subsequently, one of the two connected (glued) components was attached to the load cell using a tension clamp, which was integrated in the movable measuring arm of the testing device. During the test, the measuring arm moved upwards, separating the two materials adhering to each other at an angle of 90°. The congruent movement of the table maintained the 90° angle during the measurement. The pull-off speed was varied. The pull-off force standardized to the width of the test strip is called peel strength and is usually given in N / mm. After measuring and averaging the load required to peel the specimen, the peel strength is derived by dividing the average load by the bond line's unit width.

[0107] The cathode composite coating was separated from the current collector using bond tapes at a speed of about 0.01 mm / s to 40 mm / s to obtain a cathode, SI having a peel strength of 1.46 N / 25mm (Table 2a).Table 2aC. Conductivity measurement

[0108] The conductivity of the cathode Cl, C2, and C3 were assessed. The electrical resistance of the cathodes are as shown in below Table 2b. the graphical representation of the resistance measurement is provided in Figure 12.Table 2b

[0109] Similarly, the electrical resistance of the cathodes Cl, C2, and C3 as prepared in Example 2 was measured (Figure 12). From Figure 12 it was observed that the cathode Cl comprising the composite SI prepared by employing mixing time of 75 minutes, exhibited low resistance value of 0.5 Q. Whereas the cathodes C2 and C3 having the composites S2 and S3 respectively where either the mixing time was higher (which led to smooth and dense carbon coating as in the case of S2) or the composition was not optimized (as in the case of S3), exhibited much higher electrical resistance.D. Electrochemical analysis

[0110] For the purpose of electrochemical analysis of the cathode composites SI and S2 as explained in example 1, a half-cell was prepared using Li metal as anode.

[0111] The discharge capacity exhibited by Cl and C2 at 1C, 2C and 3C rate (Figure 11) is summarized in Table 2c.Table 2cState of health

[0112] The capacity retention of the cathodes was also analyzed in electrolyte comprising 1.2M of LiPFe dissolved in ethylene carbonate, ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) with other additives such as vinylene carbonate (VC), 1,3-propane sultone (PS), lithium difluoro(oxalato)borate (LiDFOB), and thiourea (TU).

[0113] for up to 50 cycles at 1C, to find out if appreciable cycle stability is exhibited by the cathodes as shown in Figure 13 (a) and (b). The state of health (SoH) was calculated using the formula: SoH = (maximum available capacity of the current cycle / maximum available capacity of the initial cycle) x 100.

[0114] Figure 13(a) depicts that the cathodes Cl and C2 prepared according to process as prepared as described in the Example 2 exhibited capacity retention of approximately greater than 95% in 50 cycles, at a temperature of 25°C.

[0115] Figure 13(b) depicts that the cathodes Cl and C2 prepared according to process as prepared as described in the Example 2 exhibited capacity retention of approximately greater than 95% in 50 cycles, at a temperature of 45°C. However, the slight enhancement in capacity retention pointed towards the better electrochemical performance of the cathode Cl having the cathode composite SI.

[0116] Hence, it was inferred that the cathode Cl showed enhanced capacity retention than the cathode C2, at elevated temperatures.EXAMPLE 5Preparation of electrochemical cell

[0117] This example illustrates the preparation of an electrochemical cell comprising the cathode as prepared in Example 2 of the present disclosure.

[0118] The electrochemical cell setup was obtained by assembling and sequentially stacking the pellets of cathode prepared by the method as explained in example 2, and an anode on either side of an electrolyte.

[0119] An electrochemical cell specifically a battery, and more specifically, a lithium-ion battery was prepared. The lithium-ion battery includes a cathode (positive electrode) of the dry battery electrode as explained in example 2, a Limetal anode disposed to face the cathode, and an electrolyte comprising LiPFe dissolved in ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate solvent mixture, placed between cathode and anode.EXAMPLE 6Electrochemical analysis

[0120] The electrochemical analysis of the cells El and E2 comprised of cathodes Cl and C2 respectively, prepared by the process as described in Example 2, were carried out.Initial Coulombic Efficiency (ICE)

[0121] The ICE value for El and E2 were analysed after the cell was subjected to sequential charging-discharging steps to facilitate the formation of SEI layer in the battery so as to result in ready usage of the battery with high electrochemical performance and better capacity. The charge-discharge cycles of the nominal capacity measurement were carried out at a rate of 0.5C charge / 1C discharge. The observations are provided in Figure 14. It was observed that the cells comprising the Cl prepared by the process as disclosed in Example 2, exhibited improved internal coulombic efficiency (ICE) and discharge capacity.Discharge Capacity

[0122] The cells El and E2 prepared using the electrodes Cl and C2 respectively, along with using electrolyte NGF30 was subjected to electrochemical analysis. The ICE of the cell prepared using the Cl and electrolyte NGF30 (NGF30 electrolyte comprises IM of LiPFe dissolved in solvent mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate with other additives) was found to be 92.3% and 92.5% respectively, which was higher than the cells prepared using C2. This behaviour was attributed to the proper coating of primary and secondary carbons over the surface of active material particles as found in the SEM results.

[0123] Similarly, the discharge capacity of the cell El prepared using the cathode Cl was found to be 213.13mAh / g which was higher than the cell E2 prepared using cathode C2 (Figure 15). Further, the discharge capacity of the cell prepared using the Cl and C2 at 1C, 2C, and 3C rate were analysed (Figure 16 (a), (b) and (c)).Hence, it was understood that at lower and higher c rates, the cathode Cl having the composite S 1 performed better in terms of discharge capacity as well as capacity retention.ADVANTAGES OF THE PRESENT DISCLOSURE

[0124] The present disclosure provides a dry cathode composite comprising active material, primary and secondary carbons, and binders which significantly improves the mechanical stability and integrity of the active material, exhibiting high conductivity, and improved electrochemical performance in aspects of improved discharge capacity, initial coulombic efficiency, capacity retention, and improved performance at high C rates in a range of 1C to 3C. The non-uniform layer structure of the composite, characterized by specific varied densities, allows for tailored ion transport pathways and enhances the distribution of active materials, leading to improved electrochemical performance. The rough coating of the carbons on active material surface in the composite was achieved through mixing for a period of 65 to 85 minutes which contributes to a larger surface area, maximizing contact between the active material and the electrolyte. This feature facilitates better ion diffusion, leading to increased charge transfer kinetics. Furthermore, the strategic incorporation of primary and secondary carbons with differing densities optimizes the electrical conductivity of the composite. In addition, the high-density carbon enhances electron transport, while the low-density carbon serves to improve the porosity and accessibility of the electroactive sites, thus enabling superior charge / discharge rates.

Claims

I / We Claim:

1. A cathode composite comprising:i. an active material;ii. at least one primary carbon;iii. at least one secondary carbon; andiv. at least one binder,wherein the primary carbon is coated on the active material, and the secondary carbon is coated on the primary carbon;coating density of the primary carbon and the secondary carbon, coated over the active material is in a range of 0.01 g / cc to 0.15 g / cc; andcombined thickness of the primary carbon and the secondary carbon is in a range of 55 to 540 nm.

2. The composite as claimed in claim 1, wherein the primary carbon has a coating density in a range of 0.1 to 1 g / cc, a thickness in a range of 5 to 40 nm, and a thickness-to-mass ratio is in a range of 800 to 1800 nm / g.

3. The composite as claimed in claim 1, wherein the layer of secondary carbon has a density in a range of 0.005 to 0.05 g / cc, a thickness in a range of 50 to 500 nm; and a thickness-to-mass ratio is in a range of 25 x 103to 35 x 103nm / g.

4. The composite as claimed in claim 1, wherein the primary carbon has a porosity in a range of 60 to 90% and a surface area in a range of 800 to 1800 m2 / g.

5. The composite as claimed in claim 1, wherein the active material is selected from lithium nickel manganese cobalt oxides, lithium oxides, lithium iron phosphates, or combinations thereof; the primary carbon is selected from carbon black, ketjen black, acetylene black, amorphous carbon black, or combinations thereof; and the secondary carbon is selected from graphite, graphene, KS6L, or combinations thereof.

6. The composite as claimed in claim 1, wherein the binder is selected from an adhesive binder, a fibrillating binder, or combinations thereof; the adhesive binder is selected from polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof; andthe fibrillating binder is selected from polytetrafluoroethylene, poly fluoroethylene, polyfluoroethylene vinyl ether, or combinations thereof.

7. The composite as claimed in claim 1, wherein the composite exhibits an electric resistance in a range of 0.1 to 0.5 Q.

8. A process for preparation of the cathode composite as claimed in claim 1, the process comprising:i)mixing an active material, a primary carbon, and a secondary carbon to obtain a first mixture;ii) blending the first mixture with a fibrillating binder and an adhesive binder followed by high shear mixing to obtain a second mixture; and iii) cooling the second mixture to a temperature in a range of 10 to 19 °C to obtain the dry cathode composite,wherein the mixing is carried out at a tip speed in a range of 15 to 40 m / s, at a temperature range of 10 to 25 °C, and for a period in a range of 65 to 85 minutes.

9. The process as claimed in claim 8, wherein the blending is performed at a tip speed in a range of 10 to 20 m / s, a temperature range of 10 to 19 °C, and for a period in a range of 15 to 40 minutes.

10. The process as claimed in claim 8, wherein the high shear mixing is carried out at a tip speed in a range of 15 to 40m / s, and a temperature in a range of 60 to 80 °C.

11. The process as claimed in claim 8, wherein the cooling is carried out at a tip speed in a range of 3 to 10 m / s.

12. The process as claimed in claim 8, wherein the cathode composite is calendered and optionally laminated on a current collector at a temperature in a range of 60 to 150 °C.

13. The process as claimed in claim 12, wherein the current collector is selected from aluminium foil, aluminium sheet, or pre-coated aluminium sheet.

14. A dry cathode composite prepared by the process as claimed in claim 8.

15. A cathode comprising the cathode composite as claimed in claim 1 , coated on a current collector.

16. The cathode as claimed in claim 15, wherein the cathode exhibits an initial coulombic efficiency in a range of 89 to 95%, a discharge capacity in a range of 190 to 250 mAh / g; and a capacity retention in a range of 90 to 99.9%.

17. A lithium-ion battery comprising:a. the cathode as claimed in claim 15;b. an anode; andc. an electrolyte.

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