Positive electrode material and its modification method, method for dry-preparing positive electrode film of lithium battery, positive electrode film and lithium ion battery

Abstract

This application relates to the technical field of lithium-ion batteries, and specifically relates to a cathode material and its modification method, a method for dry-preparing a lithium battery cathode electrode film, a cathode electrode film, and a lithium-ion battery. In this application, a composite modifier including a titanate coupling agent and an orthosilicate ester is pre-used to perform surface modification on the cathode material, and the modified cathode material after surface modification is used to prepare a cathode film. During the process of preparing the cathode film, the modified layer is further polymerized, and a three-dimensional network structure is formed between the binder, the conductive material, and the cathode by using the polymerized modified layer, so as to significantly improve the adhesion between various materials, thereby ensuring close contact and uniform mixing between materials while reducing the amount of binder used, achieving the purpose of reducing costs and improving the energy density of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular, to a cathode material and a modification method thereof, a method for dry-preparing a lithium battery cathode electrode film, a cathode electrode film, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have currently been widely used in portable electronic devices such as mobile phones and laptop computers, as well as in the field of electric vehicles. The active energy storage medium of a lithium-ion battery is the positive and negative electrode materials with the ability to reversibly embed and de-embed lithium ions. The traditional method for preparing the positive and negative electrodes of a lithium-ion battery is mainly completed by a wet coating process. The organic solvents required by the wet coating process have a high cost, are easy to pollute the environment, and the organic solvents also need to be evaporated to remove, resulting in energy waste. In addition, during the evaporation and drying process of the organic solvents, the sedimentation of the active materials easily causes the problem of electrode delamination. In addition, limited by the existing technology, the thickness of the electrode prepared by the wet coating process is limited, and the residual solvent easily affects the battery performance.

[0003] In recent years, technical solutions for preparing electrodes by a dry process have begun to receive attention. Generally speaking, the dry electrode preparation process refers to mixing the powders of active substances, conductive agents, and binders evenly, and then using methods such as magnetron sputtering, electrostatic spraying, or spray drying to coat them on the surface of the current collector, or making a self-supporting electrode sheet by rolling / thermocompression of the mixed materials. The technical core of the dry electrode preparation process lies in achieving the fibrillation of the binder during the powder mixing process to form a self-supporting dry electrode film, avoiding the problems caused by the use of solvents. However, there are still other problems in the current dry electrode preparation process. For example, the binder in a limited state only has point contact with the surface of the active material particles, resulting in poor contact uniformity, tightness, electrode flexibility, and durability between the active material particles and between the active material particles and the conductive agent. For the purpose of improving the uniformity and adhesion of the mixed powder, in some existing technologies, a large amount of binder (such as polytetrafluoroethylene, PTFE) is used for bonding. Although the large amount of binder plays a certain role in improving the adhesion, it leads to a decrease in the electrode specific capacity.

[0004] Currently, there are also other means to improve the contact uniformity and adhesion of active materials, the flexibility, durability and specific capacity of electrodes. For example, introducing organic polymers into the formulation to improve the adhesion between mixed materials, or developing alternative binders to reduce the dosage to enhance the specific energy of the electrode sheet, or developing special equipment from the preparation equipment to improve the fibrillation of the binder. Strategies in several different directions can, to a certain extent, improve the problems in dry electrode preparation, but the effects are single, the cost is high, and the increase in the dosage of inactive substances will affect the electrode surface density and the energy density of the corresponding battery system. Therefore, it is necessary to seek a dry electrode preparation strategy with simple process and low cost, which can ensure the uniform dispersion and good contact between materials while reducing the dosage of the binder, reduce the dosage of inactive substances, and improve the electrode surface density and the energy density of the corresponding battery system. Summary of the Invention

[0005] This application aims to provide a positive electrode material, a modification method thereof, a method for dry-preparing a positive electrode film of a lithium battery, a positive electrode film and a lithium ion battery, so as to improve the uniformity and adhesion between materials in dry electrode preparation through a simple process and at a low cost, and on the basis of improving the uniformity and adhesion between materials, reduce the dosage of inactive substances.

[0006] The embodiments of this application are implemented as follows:

[0007] In a first aspect, an embodiment of this application provides a method for modifying a positive electrode material, which includes:

[0008] S1.1: Prepare a dispersion of the positive electrode material;

[0009] S1.2: Add a composite modifier to the dispersion of the positive electrode material to form a mixture for modifying the positive electrode material, and the composite modifier includes a titanate coupling agent and a tetraethoxysilane.

[0010] In an embodiment of this application, the mass ratio of the positive electrode material to the composite modifier is (99.5:0.5)-(90:10).

[0011] In an embodiment of this application, the mass ratio of the titanate coupling agent to the tetraethoxysilane is (1:9)-(9:1).

[0012] In an embodiment of this application, the titanate coupling agent includes one or more of tetrabutyl titanate, diisooctanoyl titanate ethyl ester, triisooctanoyl titanate isopropyl ester, tetraisopropyl di(octyl phosphite) titanate, isopropoxy tris(dodecylbenzenesulfonyloxy) titanate, isopropyl trioleoyl titanate, and isopropyl dioleoyl (dioctyl phosphate acyloxy) titanate.

[0013] In one embodiment of the present application, the orthosilicate includes one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, and isopropyl orthosilicate.

[0014] In one embodiment of the present application, in S1.2, after adding the composite modifier to the positive electrode material dispersion, an ultrasonic frequency of 30 - 50 kHz is applied and maintained for 5 - 20 min, or magnetic stirring is carried out at a rotation speed of 300 - 1000 r / min for 10 - 30 min, so that the positive electrode material and the composite modifier are fully mixed.

[0015] In one embodiment of the present application, it further includes:

[0016] S1.3: Add a pH adjusting solution to adjust the pH value of the mixed solution to 4 - 5, and dry the mixed solution with a pH value of 4 - 5 to obtain a positive electrode material modified with a composite modifier.

[0017] In one embodiment of the present application, before S1.3, the pH regulator is added to the aqueous alcohol solution and fully dispersed to prepare the pH adjusting solution with a concentration of 1 - 3 mol / L.

[0018] In one embodiment of the present application, the pH regulator includes at least one of formic acid, glacial acetic acid, and oxalic acid, the aqueous alcohol solution includes an alcohol solvent and deionized water with a mass ratio of (90:10) - (70:30), and the alcohol solvent includes at least one of methanol, ethanol, ethylene glycol, and isopropyl alcohol.

[0019] In one embodiment of the present application, in S1.3, while stirring, the pH adjusting solution is added to the mixed solution, then continue stirring, measure the pH value at intervals of a set time, and after the pH value stabilizes between 4 - 5, dry the mixed solution to obtain a positive electrode material modified with a composite modifier.

[0020] In one embodiment of the present application, in S1.3, stirring is carried out at a rotation speed of 200 - 1200 r / min, and the set time is 0.5 - 1 h.

[0021] In a second aspect, an embodiment of the present application provides a method for dry - preparing a positive electrode film of a lithium - ion battery, which is characterized by including:

[0022] S2.1, mixing the positive electrode material modified with a composite modifier obtained by any one of the positive electrode material modification methods in the first aspect with a conductive agent and a binder to prepare a premixed modified positive electrode mixture;

[0023] S2.2, performing crushing, dispersion, and fibrillation treatment on the premixed modified positive electrode mixture to obtain a fibrillated modified positive electrode mixture;

[0024] S2.3. Heat and calender the fibrillated modified cathode mixture to obtain a dry-process modified cathode film.

[0025] S2.4. Composite the dry-process modified cathode film with a current collector to obtain a cathode electrode film.

[0026] In one embodiment of the present application, in S2.1, the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, carbon fiber, and carbon nanotube; the binder includes at least one of ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0027] The mass ratio of the cathode material modified by the composite modifier, the conductive agent, and the binder is (90 - 96):(2 - 5):(2 - 5).

[0028] In one embodiment of the present application, in S2.1, the cathode material modified by the composite modifier, the conductive agent, and the binder are ball-milled and mixed at a rate of 100 - 350 rpm for 0.5 - 3 h, or stirred and mixed at a rate of 500 - 2500 rpm for 0.5 - 3 h to prepare a premixed modified cathode mixture.

[0029] In one embodiment of the present application, in S2.2, the premixed modified cathode mixture is subjected to high-speed dispersion and air jet milling to achieve the purpose of fragmentation, dispersion, and fibrillation treatment, where the high-speed dispersion rate is 10000 rpm - 20000 rpm, the dispersion time is 5 - 120 min, the air jet milling speed is 20 m / s - 100 m / s, the air pressure is 0.3 - 1.2 MPa, the feeding pressure is 0.3 - 1.0 MPa, and the temperature is 20°C - 60°C.

[0030] In one embodiment of the present application, in S2.3, the fibrillated modified cathode mixture is heat-calendered at a pressure of 80 - 800 kPa and a temperature of 40 - 300°C to prepare the dry-process modified cathode film with a thickness of 100 - 500 μm.

[0031] In one embodiment of the present application, in S2.4, the dry-process modified cathode film and the current collector are composite by heat-calendering or high-temperature roll-pressing to form a cathode electrode film with a thickness of 50 - 100 μm. Among them, the pressure of heat-calendering is 200 - 600 kPa, the temperature is 40 - 300°C, and the temperature of high-temperature roll-pressing is 200 - 300°C.

[0032] In a third aspect, an embodiment of the present application provides a cathode material, the surface of the cathode material is coated with titanate coupling agent and orthosilicate; or the cathode material is processed by the cathode material modification method described in any one of the first aspects.

[0033] Fourthly, an embodiment of the present application provides a positive electrode film:

[0034] The positive electrode film includes a positive electrode film and a current collector, and the positive electrode film is made of the positive electrode material described in the third aspect;

[0035] Or the positive electrode film is formed by processing using the method for dry-preparing a lithium battery positive electrode film described in any one of the second aspect.

[0036] Fifthly, an embodiment of the present application provides a lithium ion battery, which includes:

[0037] The positive electrode material described in the third aspect;

[0038] Or the positive electrode film described in the fourth aspect.

[0039] The technical solution provided by the present application has the following beneficial effects compared with the prior art:

[0040] (1) The surface of the positive electrode material is pre-modified with a composite modifier including a titanate coupling agent and a tetraalkyl orthosilicate. The tetraalkyl orthosilicate material has good chemical stability. After being coated with it, the surface characteristics of the positive electrode material can be optimized. The addition of the titanate coupling agent also improves the high-temperature resistance of the dry electrode sheet, which promotes the safety of the battery cell. The chemical bond formed between the modification layer formed by the composite modifier and the positive electrode is more stable than the physical adsorption. Therefore, when the materials are mixed at a low speed, the agglomeration of the positive electrode particles can be effectively inhibited. The modified positive electrode material has smaller charge-discharge polarization, higher first charge-discharge efficiency, higher capacity retention rate, and better cycle performance.

[0041] (2) After the conductive agent and the binder are mixed with the positive electrode material modified by the composite modifier at a low speed, the binder and the conductive material are evenly distributed around the positive electrode particles. During the further high-speed stirring, shearing or grinding process, the modification layer polymerizes. After polymerization, a coating network is formed between the binder, the conductive substance and the positive electrode, which can not only achieve the uniform mixing of each component, but also avoid the decrease in the adhesiveness between the materials. Therefore, without affecting the material contact and mixing uniformity, the amount of the binder can be reduced.

[0042] (3) The dry method is used for electrode preparation, and no solvent is used in the mixing process of each component, avoiding the problem of electrode delamination caused by solvent evaporation. Compared with special equipment, this strategy has simple operation, reduces equipment costs and energy consumption. The optimized strategy and the preparation process are simple, saving material costs and being beneficial to environmental safety. Description of the Drawings

[0043] To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0044] Figure 1 It is the first-cycle charge-discharge curve graph of the battery of Embodiment 1 of the present application and the battery of Comparative Example 1.

[0045] Figure 2 It is the capacity retention rate graph of the battery of Embodiment 1 of the present application and the battery of Comparative Example 1 after 100 charge-discharge cycles.

[0046] Figure 3 It is the cross-sectional electron microscope test graph (1μm) of the dry-process modified NCM811 positive electrode film provided in Embodiment 1 of the present application.

[0047] Figure 4 It is the cross-sectional electron microscope test graph (10μm) of the dry-process modified NCM811 positive electrode film provided in Embodiment 1 of the present application. Specific Embodiments

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0049] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" usually refer to the upper and lower in the actual use or working state of the device, specifically the drawing direction in the accompanying drawings; and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "including" means "including but not limited to". The use of terms such as first, second, and third is only for marking and does not impose a numerical requirement or establish an order.

[0050] In the present application, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural.

[0051] In this application, "at least one" means one or more, and "a plurality" means two or more. "One or several", "at least one (item) below", or similar expressions refer to any combination of these items, including any combination of single (item) or plural items. For example, "at least one (item) among a, b, or c", or "at least one (item) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0052] The various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the description of the range has specifically disclosed all possible sub - ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0053] In electrochemical energy storage devices, lithium - ion batteries have become the mainstream in the battery field today due to their advantages such as high working voltage, high specific capacity, wide operating temperature range, good cycle performance, and long lifespan. Currently, they have been widely used in portable electronic devices such as mobile phones and laptop computers, as well as in the field of electric vehicles, and are gradually expanding into the energy storage field and the field of cordless power tools. The active energy storage medium of lithium - ion batteries is the positive and negative electrode materials with the ability to reversibly intercalate and deintercalate lithium ions. The traditional method for preparing lithium - ion battery electrodes mainly uses the wet - coating process, that is, mixing active materials, conductive agents, binders, and solvents to form a slurry, and then coating the slurry on a foil and evaporating the solvent to obtain the electrode. The entire process not only has energy waste caused by drying and environmental pollution caused by high - cost organic solvents, but also problems such as electrode delamination caused by the sedimentation of active materials during the solvent evaporation process, limited electrode thickness obtained by the process, and solvent residues affecting battery performance cannot be ignored.

[0054] To solve the problems in the wet electrode preparation process, researchers have started to focus on the dry electrode preparation process. The dry electrode preparation process refers to evenly mixing the powders of active materials, conductive agents, and binders, and then using methods such as magnetron sputtering, electrostatic spraying, or spray drying to coat them on the surface of the current collector, or making self-supporting electrode sheets by rolling / thermocompression of the mixed materials. The dry electrode technology avoids using any solvents during electrode preparation. This simplified process can not only reduce the cost of solvent materials and the cost of solvent drying, recovery, and drying equipment, but also facilitate the control of the microstructure of the electrode sheet, inhibit electrode delamination, and achieve controllability of electrode thickness and areal density.

[0055] The technical core of the dry electrode lies in achieving the fibrillation of the binder during the powder mixing process to form a self-supporting dry electrode film. However, there are still some problems to be solved in the dry electrode technology, which has led to the fact that some mainstream lithium-ion batteries have not widely adopted the dry electrode preparation process. On the one hand, no solvents are used in the production of dry electrodes, and the binder exists in a fibrous state, with only point contact with the surface of the active material particles, resulting in poor contact uniformity and tightness between the active material particles inside the electrode and between them and the conductive agent, as well as poor flexibility and durability of the electrode. On the other hand, for the purpose of improving the uniformity and adhesiveness of the mixed powder, the amount of the binder is increased in the dry electrode preparation process. For example, the amount of polytetrafluoroethylene (PTFE) used as the binder is increased, which leads to a significant reduction in the specific capacity of the electrode.

[0056] To balance the problems of contact uniformity and tightness between active material particles and between them and the conductive agent, electrode flexibility, durability, and specific capacity, improvement solutions have also been considered from multiple different directions. For example, introducing organic polymers into the formulation to improve the adhesiveness between the mixed materials, or developing alternative binders to reduce the dosage to enhance the specific energy of the electrode sheet, or developing special equipment from the preparation equipment to improve the fibrillation of the binder. Although the existing improvement solutions can, to a certain extent, improve the problems in the dry electrode preparation, the effects are single, the cost is high, and the increase in the amount of non-active substances will affect the areal density of the electrode and the energy density of the corresponding battery system.

[0057] Based on this, the inventor proposes a technical solution. First, use a composite modifier including titanate coupling agent and orthosilicate to perform surface modification on the cathode material. During the process of preparing the cathode film, the modified layer is further polymerized, and a three-dimensional network structure is formed between the binder, conductive substances, and the cathode by using the polymerized modified layer, so as to significantly improve the adhesiveness between various materials. Therefore, while reducing the amount of the binder, the tight contact and uniform mixing between materials are ensured, achieving the purpose of reducing costs and increasing the energy density of the battery.

[0058] The technical solution of this application is as follows:

[0059] In a first aspect, a method for modifying a cathode material is provided, including:

[0060] S1.1: Prepare a cathode material dispersion;

[0061] S1.2: Add a composite modifier to the cathode material dispersion and mix well to form a mixture. The composite modifier includes a titanate coupling agent and an orthosilicate.

[0062] In S1.1, a certain amount of cathode material is weighed and dispersed in a solvent by ultrasonic or mechanical stirring or ball milling to prepare a uniform cathode dispersion. The cathode material includes at least one of lithium cobaltate (LiCoO2), lithium manganate (LiMn2O4), lithium nickel manganese oxide (LiNi0.5Mn1.5O4), lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium nickel cobalt manganese oxide (LiNixCoyMnzO2, where x + y + z = 1), and lithium-rich compounds. The solvent is at least one of methanol, ethanol, ethylene glycol, and isopropyl alcohol. The concentration of the cathode material is 0.1 - 2 g / ml. Among them, the frequency of ultrasonic dispersion is 50 - 80 kHz, and the duration is 10 - 30 min. The conditions for mechanical stirring include: the stirring rate is 1500 - 3000 rpm, and the duration is 10 - 30 min. The conditions for ball milling include: the ball milling rate is 200 - 300 rpm, and the duration is 5 - 20 min.

[0063] In some embodiments, in S1.2, the mass ratio of the cathode material to the composite modifier is (99.5:0.5) - (90:10). Optionally, the mass ratio of the cathode material to the composite modifier is (98:2) - (95:5). Optionally, the mass ratio of the cathode material to the composite modifier is (97:3) - (96:4).

[0064] In some embodiments, in S1.2, the mass ratio of the titanate coupling agent to the orthosilicate is (1:9) - (9:1). Optionally, the mass ratio of the titanate coupling agent to the orthosilicate is (1:3) - (3:1). Optionally, the mass ratio of the titanate coupling agent to the orthosilicate is (2:3) - (3:2).

[0065] In some embodiments, in S1.2, the titanate coupling agent includes one or more of tetrabutyl titanate, diisooctanoyl titanate ethyl ester, triisooctanoyl titanate isopropyl ester, tetra(isopropyl) di(octylphosphite) titanate, isopropoxy tris(dodecylbenzenesulfonyloxy) titanate, isopropyl trioleoyl titanate, and isopropyl dioleoyl (dioctylphosphate) titanate.

[0066] In some embodiments, in S1.2, the orthosilicate includes one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, and isopropyl orthosilicate.

[0067] In some embodiments, in S1.2, after adding the composite modifier to the positive electrode material dispersion, an ultrasonic frequency of 30 - 50 kHz is applied and maintained for 5 - 20 min, or magnetic stirring is performed at a rotation speed of 300 - 1000 r / min for 10 - 30 min to fully mix the positive electrode material and the composite modifier.

[0068] To facilitate the storage and application of the positive electrode material, in some embodiments, after modifying the positive electrode material with the composite modifier, the liquid obtained after S1.2 is also dried. Exemplarily, the positive electrode material modification method provided in the embodiments of the present application further includes step S1.3: adding a pH adjustment liquid to adjust the pH value of the mixed liquid to 4 - 5, and drying the mixed liquid with a pH value of 4 - 5 to obtain the positive electrode material modified with the composite modifier.

[0069] In some embodiments, the pH adjustment liquid is prepared before S1.3. Exemplarily, a pH regulator is added to an aqueous alcohol solution and fully dispersed to prepare a pH adjustment liquid with a concentration of 1 - 3 mol / L.

[0070] Among them, the pH regulator includes at least one of formic acid, glacial acetic acid, and oxalic acid, the aqueous alcohol solution includes an alcohol solvent and deionized water with a mass ratio of (90:10) - (70:30), and the alcohol solvent includes at least one of methanol, ethanol, ethylene glycol, and isopropyl alcohol.

[0071] In some embodiments, in S1.3, the pH adjustment liquid is added to the mixed liquid while stirring, and then stirring continues. The pH value is measured once every set time interval. After the pH value stabilizes between 4 and 5, the mixed liquid is dried to obtain the positive electrode material modified with the composite modifier.

[0072] In some embodiments, in S1.3, stirring is performed at a rotation speed of 200 - 1200 r / min, and the set time is 0.5 - 1 h.

[0073] In a second aspect, the embodiments of the present application provide a method for dry - preparing a lithium - battery positive - electrode film, including:

[0074] S2.1, mixing the positive electrode material modified with the composite modifier obtained after the positive electrode material modification method with a conductive agent and a binder to prepare a premixed modified positive - electrode mixture;

[0075] S2.2, performing crushing, dispersion, and fibrillation treatment on the premixed modified positive - electrode mixture to obtain a fibrillated modified positive - electrode mixture;

[0076] S2.3. Heat and calender the fibrillated modified cathode mixture to obtain a dry-process modified cathode film.

[0077] S2.4. Composite the dry-process modified cathode film with a current collector to obtain a cathode electrode film.

[0078] In some embodiments, in S2.1, the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, carbon fiber, and carbon nanotube; the binder includes at least one of ethylene-tetrafluoroethylene copolymer, polyacrylonitrile, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0079] Among them, the mass ratio of the composite modifier-modified cathode material, conductive agent, and binder is (90-96):(2-5):(2-5).

[0080] In some embodiments, in S2.1, the composite modifier-modified cathode material, conductive agent, and binder are ball-milled and mixed at a rate of 100-350 rpm for 0.5-3 h, or stirred and mixed at a rate of 500-2500 rpm for 0.5-3 h to prepare a premixed modified cathode mixture.

[0081] In some embodiments, in S2.2, the premixed modified cathode mixture is subjected to high-speed dispersion and air jet milling to achieve the purpose of crushing, dispersing, and fibrillating treatment, where the high-speed dispersion rate is 10000 rpm - 20000 rpm, the dispersion time is 5-120 min, the air jet milling speed is 20 m / s - 100 m / s, the air pressure is 0.3-1.2 MPa, the feeding pressure is 0.3-1.0 MPa, and the temperature is 20°C - 60°C.

[0082] In S2.1, after the conductive agent and binder are mixed with the composite modifier-modified cathode material at a low speed, the binder and conductive material are evenly distributed around the cathode material particles. Further, in S2.2, during the high-speed stirring, shearing, or grinding process, the modification layer polymerizes, and a coating network is formed between the binder, conductive substance, and cathode material. Thus, both the uniform mixing of each component can be achieved, and the decrease in the adhesiveness between materials can be avoided. Therefore, without affecting the material contact and mixing uniformity, the amount of binder used can be reduced.

[0083] In addition, the modification layer including the titanate coupling agent and orthosilicate also plays a certain hydrophobic role, which is beneficial to the implementation of subsequent dry-process steps and avoids the interference of moisture caused by factors such as equipment, environment, and reaction during the preparation process.

[0084] In some embodiments, in S2.3, the fibrillated modified cathode mixture is subjected to hot rolling treatment at a pressure of 80 - 800 kPa and a temperature of 40 - 300 °C to prepare a dry-process modified cathode film with a thickness of 100 - 500 μm.

[0085] Fibrillation modification can transform the cathode material into a fibrous structure, where conductive agents such as carbon black or conductive nanomaterials are coated by the fibers and form a conductive network with the cathode material. The binder is used to firmly bind these fibers and conductive agents to the cathode material.

[0086] Hot rolling is a process of heating the mixture to an appropriate temperature and applying pressure to cause mutual combination and densification under the combined action of thermal and mechanical forces. After the cathode material, conductive agent, and binder are uniformly mixed and form a fibrillated three-dimensional network structure, through the action of hot pressing, the gaps between the structures are reduced, further exerting the role of the binder, enhancing the binding force and integrity of the material, and forming a relatively dense cathode film.

[0087] In the formed dense cathode film, the fibrous structure provides a large specific surface area, and the conductive agent forms a conductive network, which is conducive to the full and rapid progress of the electrochemical reaction.

[0088] In some embodiments, in S2.4, the dry-process modified cathode film and the current collector are compounded by hot rolling or high-temperature roll pressing to form a cathode electrode film with a thickness of 50 - 100 μm. Among them, the pressure of hot rolling is 200 - 600 kPa, the temperature is 40 - 300 °C, and the temperature of high-temperature roll pressing is 200 - 300 °C.

[0089] The current collector includes one of aluminum foil and carbon-coated aluminum foil.

[0090] Using the method provided by the embodiments of the present application to prepare the cathode material and the cathode electrode film, the mixing process of each component does not use a solvent, avoiding the problem of electrode delamination caused by solvent evaporation. And compared with special equipment, this strategy is simple to operate, reduces equipment costs and energy consumption, the optimization strategy and the preparation process are simple, saves material costs, and is beneficial to environmental safety.

[0091] In a third aspect, the present application provides a cathode material, the surface of which is coated with a titanate coupling agent and a silicate ester, or the cathode material is processed by using the cathode material modification method provided in any of the foregoing embodiments.

[0092] The orthosilicate material has good chemical stability. After coating with it, the surface characteristics of the cathode material can be optimized. The addition of titanate coupling agent also improves the high-temperature resistance of the dry electrode sheet, which promotes the safety of the battery cell. The chemical bond formed between the modification layer and the cathode is more stable than the physical adsorption, so the agglomeration of cathode particles can be effectively inhibited when the materials are mixed at a low speed.

[0093] Fourthly, the present application provides a cathode electrode film, which includes a cathode film and a current collector. The cathode film is stacked on the current collector and formed by composite molding. The cathode film is formed by heat rolling after fibrillation modification of a cathode material, a conductive agent and a binder. The surface of the cathode material is coated with a titanate coupling agent and an orthosilicate; or the cathode electrode film is processed by using the method for preparing a lithium battery cathode electrode film by dry method provided in any one of the foregoing embodiments.

[0094] As described above, the current collector includes one of aluminum foil and carbon-coated aluminum foil.

[0095] The cathode film is a dense fibrous structure. The cathode material and the conductive agent are uniformly mixed and tightly adhered under the action of the binder. The electrode does not delaminate, and the amount of non-active substances is small.

[0096] Fifthly, the present application provides a lithium ion battery, which includes the foregoing cathode electrode film, anode electrode film and electrolyte.

[0097] The cathode electrode film not only has a dense structure, a large specific surface area and good electrical conductivity, but also the addition of the titanate coupling agent improves the high-temperature resistance of the dry electrode sheet and improves the safety of the battery cell of the lithium ion battery.

[0098] The present application will be specifically described below through specific embodiments. The following embodiments are only partial embodiments of the present application and do not limit the present application.

[0099] Example 1

[0100] The embodiment of the present application provides a lithium battery, the cathode electrode film of which is formed by compounding a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0101] First, perform surface modification on the cathode material:

[0102] S1.1 Pretreatment of the cathode material: Weigh 100 g of lithium nickel cobalt manganese oxide cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811) and disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0103] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator in an alcohol-water solution and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency 30 kHz, time 10 min.

[0104] S1.3 Mixing the cathode material and the composite modifier: Add 2.08 g of tetrabutyl titanate and 2.08 g of tetraethyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1, that is, the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in the composite modifier is 1:1, and the mass ratio of the NCM811 cathode material to the composite modifier is about 96:4. Then use magnetic stirring to form a uniform mixture, with a stirring speed of 1000 r / min and a time of 30 min.

[0105] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, with a stirring speed of 1000 r / min. After the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0106] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0107] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0108] S2.1 Preparation of the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain a premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 94:3:3. The stirring and mixing rate is 1500 rpm and the mixing time is 2 h.

[0109] S2.2 Preparation of the fibrillated modified cathode mixture: Use the air jet milling method to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain a fibrillated modified NCM811 cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0110] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0111] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0112] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0113] S3.1 Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into a circular piece with a diameter of 16 mm as the negative electrode plate;

[0114] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular piece with a diameter of 14 mm as the cathode plate;

[0115] S3.3 Cut a polyethylene homopolymer film into a circular piece with a diameter of 19 mm as the separator;

[0116] S3.4 In a glove box filled with argon, stack the cathode plate, the negative electrode plate, and the separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1M LiPF6 in FEC-DMC (volume ratio 1:4).

[0117] Example 2

[0118] This application example provides a lithium battery, whose cathode electrode film is formed by compounding a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0119] First, perform surface modification on the cathode material:

[0120] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium iron phosphate cathode material (LiFePO4) and disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform lithium iron phosphate cathode material dispersion. The concentration of lithium iron phosphate is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0121] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol aqueous solution, and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol aqueous solution. The mass ratio of the alcohol solvent to deionized water in the alcohol aqueous solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency 30 kHz, time 10 min.

[0122] S1.3 Mixing the lithium iron phosphate cathode material and the composite modifier: Add 2.63 g of a composite modifier of tetrabutyl titanate and tetraethyl orthosilicate to the lithium iron phosphate cathode material dispersion obtained in S1.1. That is, the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in the composite modifier is 1:1, and the mass ratio of the lithium iron phosphate cathode material to the composite modifier is about 95:5. Then use magnetic stirring to form a uniform mixture. The stirring speed is 1000 r / min, and the time is 30 min.

[0123] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol aqueous solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5. The stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven and dry it until the solvent is completely removed. The drying temperature is 60 °C, and the drying time is 24 h. Finally, obtain the lithium iron phosphate cathode material modified by the composite modifier.

[0124] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0125] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by dry method:

[0126] S2.1 Preparation of the premixed modified positive electrode mixture: Weigh 94 g of the lithium iron phosphate cathode material modified by the composite modifier, 3 g of acetylene black, and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain a premixed modified positive electrode mixture. The mass ratio of the lithium iron phosphate cathode material modified by the composite modifier, the conductive agent acetylene black, and the binder polytetrafluoroethylene is 94:3:3. The stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0127] S2.2 Preparation of the fibrillated modified positive electrode mixture: Use air jet milling to crush, disperse, and fibrillate the premixed modified positive electrode mixture obtained in step S2.1 to obtain a fibrillated modified lithium iron phosphate cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0128] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified lithium iron phosphate cathode mixture is subjected to heat rolling treatment to obtain a dry-modified lithium iron phosphate cathode film with a thickness of 300 μm.

[0129] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified lithium iron phosphate cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified lithium iron phosphate cathode film is combined with the aluminum foil current collector to obtain a dry-modified lithium iron phosphate cathode electrode film with a thickness of 50 μm.

[0130] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0131] S3.1 Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into circular pieces with a diameter of 16 mm to serve as the negative electrode sheet;

[0132] S3.2 Cut the cathode electrode film obtained in S2.4 above into circular pieces with a diameter of 14 mm to serve as the cathode sheet;

[0133] S3.3 Cut a polyethylene homopolymer film into circular pieces with a diameter of 19 mm to serve as the separator;

[0134] S3.4 In a glove box filled with argon, stack the cathode sheet, the negative electrode sheet, and the separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0135] Example 3

[0136] This application example provides a lithium battery, the cathode electrode film of which is formed by combining a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0137] First, perform surface modification on the cathode material:

[0138] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium manganese phosphate cathode material (LiMnPO4) and disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform dispersion of lithium manganese phosphate cathode material. The concentration of lithium manganese phosphate is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0139] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol-water solution, and disperse it thoroughly by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0140] S1.3 Mixing the lithium manganese phosphate cathode material and the composite modifier: Add 1.02 g of a composite modifier of tetrabutyl titanate and tetraethyl orthosilicate to the lithium manganese phosphate cathode material dispersion obtained in S1.1, that is, the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in the composite modifier is 1:1, and the mass ratio of the lithium manganese phosphate cathode material to the composite modifier is about 98:2. Then use ultrasonic dispersion to form a uniform mixture. The ultrasonic dispersion conditions are 45 kHz and 20 min.

[0141] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Stir continuously during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, where the stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven and dry it until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the lithium manganese phosphate cathode material modified by the composite modifier.

[0142] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 and the preparation of the pH adjustment solution is completed.

[0143] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0144] S2.1 Preparation of the premixed modified positive electrode mixture: Weigh 94 g of the lithium manganese phosphate cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified positive electrode mixture. The mass ratio of the lithium manganese phosphate cathode material modified by the composite modifier, acetylene black and the binder polytetrafluoroethylene is 94:3:3; the stirring and mixing rate is 1500 rpm and the mixing time is 2 h.

[0145] S2.2 Preparation of the fibrillated modified positive electrode mixture: Use the air jet milling method to crush, disperse and fibrillate the premixed modified positive electrode mixture obtained in step S2.1 to obtain the fibrillated modified lithium manganese phosphate cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0146] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified lithium manganese phosphate cathode mixture is subjected to hot rolling treatment to obtain a dry-modified lithium manganese phosphate cathode film with a thickness of 300 μm.

[0147] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified lithium manganese phosphate cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified lithium manganese phosphate cathode film is combined with the aluminum foil current collector to obtain a dry-modified lithium manganese phosphate cathode electrode film with a thickness of 50 μm.

[0148] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0149] S3.1 Select a negative electrode material (silicon-graphite composite material), cut the negative electrode material into a circular piece with a diameter of 16 mm as the negative electrode plate;

[0150] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular piece with a diameter of 14 mm as the positive electrode plate;

[0151] S3.3 Cut a polyethylene homopolymer film into a circular piece with a diameter of 19 mm as the separator;

[0152] S3.4 In a glove box filled with argon, stack the positive electrode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0153] Example 4

[0154] An embodiment of the present application provides a lithium battery, the positive electrode electrode film of which is formed by combining a positive electrode film and a current collector. The positive electrode material used in the positive electrode film is modified by a composite modifier, and the preparation method is as follows.

[0155] First, perform surface modification on the positive electrode material:

[0156] S1.1 Pretreatment of positive electrode material: Weigh 100 g of lithium nickel cobalt manganese oxide positive electrode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 positive electrode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0157] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol-water solution, and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0158] S1.3 Mixing the cathode material and the composite modifier: Add 2.10 g of diisostearoyl titanate and 3.15 g of tetraethyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1. That is, the mass ratio of diisostearoyl titanate to tetraethyl orthosilicate in the composite modifier is 4:6, and the mass ratio of the NCM811 cathode material to the composite modifier is about 95:5. Then use magnetic stirring to form a uniform mixture, with a stirring speed of 1000 r / min and a time of 30 min.

[0159] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, with a stirring speed of 1000 r / min. After the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0160] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0161] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0162] S2.1 Preparation of the premixed modified cathode mixture: Weigh 95 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black, and 2 g of polytetrafluoroethylene, and use stirring to mix them to obtain a premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black, and the binder polytetrafluoroethylene is 95:3:2. The stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0163] S2.2 Preparation of the fibrillated modified cathode mixture: Use the airflow pulverization method to crush, disperse, and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain a fibrillated modified NCM811 cathode mixture. The speed of airflow pulverization is 50 m / s, the airflow pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0164] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0165] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0166] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0167] S3.1 Select a negative electrode material (silicon-graphite composite material), cut the negative electrode material into circular pieces with a diameter of 16 mm to serve as negative electrode plates;

[0168] S3.2 Cut the cathode electrode film obtained in S2.4 above into circular pieces with a diameter of 14 mm to serve as cathode plates;

[0169] S3.3 Cut a polyethylene homopolymer film into circular pieces with a diameter of 19 mm to serve as a separator;

[0170] S3.4 In a glove box filled with argon, stack the cathode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0171] Example 5

[0172] This application example provides a lithium battery, whose cathode electrode film is formed by compounding a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0173] First, perform surface modification on the cathode material:

[0174] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium nickel cobalt manganate cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm, and the time is 15 min.

[0175] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol-water solution, and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L; the ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0176] S1.3 Mixing the cathode material and the composite modifier: Add 0.2 g of diisooctyl titanate titanate and 0.3 g of tetraethyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1. That is, the mass ratio of diisooctyl titanate to tetraethyl orthosilicate in the composite modifier is 4:6, and the mass ratio of the NCM811 cathode material to the composite modifier is about 99.5:0.5. Then, use ultrasonic dispersion to form a uniform mixture. The ultrasonic dispersion conditions are 50 kHz and 20 min.

[0177] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH range of the mixture is 4.5. The stirring speed is 1000 r / min; after the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0178] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0179] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0180] S2.1 Preparation of the premixed modified cathode mixture: Weigh 95 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 2 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 95:3:2; the stirring and mixing rate is 1500 rpm and the mixing time is 2 h.

[0181] S2.2 Preparation of the fibrillated modified cathode mixture: Use the air flow crushing method to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain the fibrillated modified NCM811 cathode mixture. The air flow crushing speed is 50 m / s, the air flow pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0182] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0183] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is combined with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0184] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0185] S3.1 Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into a circular piece with a diameter of 16 mm as the negative electrode plate;

[0186] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular piece with a diameter of 14 mm as the cathode plate;

[0187] S3.3 Cut a polyethylene homopolymer film into a circular piece with a diameter of 19 mm as the separator;

[0188] S3.4 In a glove box filled with argon, stack the cathode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0189] Example 6

[0190] This application example provides a lithium battery, whose cathode electrode film is formed by combining a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0191] First, perform surface modification on the cathode material:

[0192] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium nickel cobalt manganese oxide cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811) and disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0193] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol aqueous solution, and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol aqueous solution. The mass ratio of the alcohol solvent to deionized water in the alcohol aqueous solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency 30 kHz, time 10 min.

[0194] S1.3 Mixing the cathode material and the composite modifier: Add 0.83 g of isopropyltrioleoyltitanate and 3.33 g of tetraethyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1. That is, the mass ratio of isopropyltrioleoyltitanate to tetraethyl orthosilicate in the composite modifier is about 1:4, and the mass ratio of the NCM811 cathode material to the composite modifier is about 96:4. Then use magnetic stirring to form a uniform mixture. The stirring speed is 1000 r / min, and the time is 30 min.

[0195] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol aqueous solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5. The stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C, and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0196] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0197] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0198] S2.1 Preparation of the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use ball milling to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 94:3:3. The ball milling mixing conditions are 300 rpm, and the mixing time is 2.5 h.

[0199] S2.2 Preparation of the fibrillated modified cathode mixture: Use the airflow crushing method to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain the fibrillated modified NCM811 cathode mixture. The airflow crushing speed is 50 m / s, the airflow pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0200] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0201] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is combined with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0202] Furthermore, a button lithium-ion battery is prepared using the above cathode electrode film:

[0203] S3.1 Select a negative electrode material (silicon-graphite composite material), cut the negative electrode material into a circular sheet with a diameter of 16 mm as the negative electrode plate;

[0204] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular sheet with a diameter of 14 mm as the cathode plate;

[0205] S3.3 Cut a polyethylene homopolymer film into a circular sheet with a diameter of 19 mm as the separator;

[0206] S3.4 In a glove box filled with argon, stack the cathode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button lithium-ion battery. Among them, the electrolyte is 1M LiPF6 in FEC-DMC (volume ratio 1:4).

[0207] Example 7

[0208] This application example provides a lithium battery, the cathode electrode film of which is formed by combining a cathode film and a current collector, and the cathode material used in the cathode film is modified by a composite modifier. The preparation method is as follows.

[0209] First, perform surface modification on the cathode material:

[0210] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium nickel cobalt manganese oxide cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0211] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol-water solution and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency 30 kHz, time 10 min.

[0212] S1.3 Mixing the cathode material and the composite modifier: Add 1.25 g of tetrabutyl titanate and 2.51 g of tetramethoxysilane composite modifier to the NCM811 cathode material dispersion obtained in S1.1, that is, the mass ratio of tetrabutyl titanate to tetramethoxysilane in the composite modifier is about 1:2, and the mass ratio of the NCM811 cathode material to the composite modifier is about 96:4. Then use magnetic stirring to form a uniform mixture, with a stirring speed of 1000 r / min and a time of 30 min.

[0213] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, with a stirring speed of 1000 r / min. After the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0214] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0215] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by dry method:

[0216] S2.1 Preparation of the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 94:3:3; the stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0217] S2.2 Preparation of the fibrillated modified cathode mixture: Use the air jet milling method to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain the fibrillated modified NCM811 cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0218] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 700 kPa and a temperature of 290 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 100 μm.

[0219] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0220] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0221] S3.1 Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into a circular piece with a diameter of 16 mm as the negative electrode plate;

[0222] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular piece with a diameter of 14 mm as the cathode plate;

[0223] S3.3 Cut a polyethylene homopolymer film into a circular piece with a diameter of 19 mm as the separator;

[0224] S3.4 In a glove box filled with argon, stack the cathode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0225] Example 8

[0226] An embodiment of the present application provides a lithium battery, the cathode electrode film of which is formed by compounding a cathode film and a current collector. The cathode material used in the cathode film is modified by a composite modifier, and the preparation method is as follows.

[0227] First, perform surface modification on the cathode material:

[0228] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium nickel cobalt manganese oxide cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0229] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol aqueous solution, and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol aqueous solution. The mass ratio of the alcohol solvent to deionized water in the alcohol aqueous solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0230] S1.3 Mixing the cathode material and the composite modifier: Add 3.32 g of tetrabutyl titanate and 0.83 g of tetrabutyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1. That is, the mass ratio of tetrabutyl titanate to tetrabutyl orthosilicate in the composite modifier is about 4:1, and the mass ratio of the NCM811 cathode material to the composite modifier is about 96:4. Then use magnetic stirring to form a uniform mixture, with a stirring speed of 1000 r / min and a time of 30 min.

[0231] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol aqueous solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, where the stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven to dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0232] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 to complete the preparation of the pH adjustment solution.

[0233] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0234] S2.1 Preparation of the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 94:3:3. The stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0235] S2.2 Preparation of the fibrillated modified cathode mixture: Use the air jet milling method to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain the fibrillated modified NCM811 cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0236] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0237] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is combined with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0238] Then, the above-mentioned cathode electrode film is used to prepare a button-type lithium-ion battery:

[0239] S3.1 Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into circular pieces with a diameter of 16 mm to serve as the negative electrode plates;

[0240] S3.2 Cut the cathode electrode film obtained in S2.4 above into circular pieces with a diameter of 14 mm to serve as the cathode plates;

[0241] S3.3 Cut a polyethylene homopolymer film into circular pieces with a diameter of 19 mm to serve as the separator;

[0242] S3.4 In a glove box filled with argon, stack the cathode plate, the negative electrode plate, and the separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0243] Example 9

[0244] An embodiment of this application provides a lithium battery, the cathode electrode film of which is formed by combining a cathode film and a current collector, and the cathode material used in the cathode film is modified by a composite modifier. The preparation method is as follows.

[0245] First, perform surface modification on the cathode material:

[0246] S1.1 Pretreatment of cathode material: Weigh 100 g of lithium nickel cobalt manganese oxide cathode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 cathode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0247] S1.2 Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator into an alcohol-water solution and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L. The ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0248] S1.3 Mixing the cathode material and the composite modifier: Add 2.50 g of tetrabutyl titanate and 1.66 g of isopropyl orthosilicate composite modifier to the NCM811 cathode material dispersion obtained in S1.1. That is, the mass ratio of tetrabutyl titanate to isopropyl orthosilicate in the composite modifier is about 3:2, and the mass ratio of the NCM811 cathode material to the composite modifier is about 96:4. Then use magnetic stirring to form a uniform mixture. The stirring speed is 1000 r / min and the time is 30 min.

[0249] S1.4 Adjusting the pH value and drying: Use the glacial acetic acid alcohol-water solution in S1.2 to adjust the pH of the mixture in S1.3 to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5. The stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven and dry it until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by the composite modifier.

[0250] Among them, the order of S1.2 is not limited. As long as S1.2 is carried out before S1.4 and the preparation of the pH adjustment solution is completed.

[0251] Then, use the cathode material modified by the composite modifier to prepare the positive electrode film by the dry method:

[0252] S2.1 Preparation of the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by the composite modifier, 3 g of acetylene black and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by the composite modifier, the conductive agent acetylene black and the binder polytetrafluoroethylene is 94:3:3. The stirring and mixing rate is 1500 rpm and the mixing time is 2 h.

[0253] S2.2 Preparation of the fibrillated modified cathode mixture: Use high-speed dispersion to crush, disperse and fibrillate the premixed modified cathode mixture obtained in step S2.1 to obtain the fibrillated modified NCM811 cathode mixture. The high-speed dispersion rate is 15000 m / s and the time is 100 min.

[0254] S2.3 Preparation of dry-modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated modified NCM811 cathode mixture is subjected to hot rolling treatment to obtain a dry-modified NCM811 cathode film with a thickness of 300 μm.

[0255] S2.4 Preparation of cathode electrode film: At a temperature of 300 °C, the dry-modified NCM811 cathode film obtained in S2.3 and an aluminum foil current collector are roll-pressed so that the dry-modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-modified NCM811 cathode electrode film with a thickness of 50 μm.

[0256] Then use the above cathode electrode film to prepare a button-type lithium-ion battery:

[0257] S3.1 Select a negative electrode material (silicon-graphite composite material), cut the negative electrode material into a circular sheet with a diameter of 16 mm as the negative electrode plate;

[0258] S3.2 Cut the cathode electrode film obtained in S2.4 above into a circular sheet with a diameter of 14 mm as the cathode plate;

[0259] S3.3 Cut a polyethylene homopolymer film into a circular sheet with a diameter of 19 mm as the separator;

[0260] S3.4 In a glove box filled with argon, stack the cathode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1M LiPF6 in FEC-DMC (volume ratio 1:4).

[0261] Comparative Example 1

[0262] Comparative Example 1 is basically the same as Example 1, the difference is that the NCM811 cathode active material used in this example is not subjected to surface modification treatment, that is:

[0263] (1) Preparation of premixed cathode mixture: Weigh 94 g of NCM811 cathode material, 3 g of acetylene black, and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain a premixed cathode mixture. The mass ratio of the NCM811 cathode material, the conductive agent acetylene black, and the binder polytetrafluoroethylene is 94:3:3; the stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0264] (2) Preparation of fibrillated cathode mixture: The premixed cathode mixture obtained in step (1) is subjected to crushing, dispersion, and fibrillation treatment using air jet milling to obtain a fibrillated NCM811 cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0265] (3) Preparation of dry-type positive electrode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, the fibrillated NCM811 positive electrode mixture is subjected to hot rolling treatment to obtain a dry-type NCM811 positive electrode film with a thickness of 300 μm.

[0266] (4) Preparation of positive electrode film: At a temperature of 300 °C, the dry-type NCM811 positive electrode film obtained in step (3) and an aluminum foil current collector are roll-pressed so that the dry-type NCM811 positive electrode film is compounded with the aluminum foil current collector to obtain a dry-type NCM811 positive electrode film with a thickness of 50 μm.

[0267] (5) Select a negative electrode material (silicon-graphite composite material), and cut the negative electrode material into circular pieces with a diameter of 16 mm as the negative electrode plate;

[0268] (6) Cut the positive electrode film obtained in step (4) into circular pieces with a diameter of 14 mm as the positive electrode plate;

[0269] (7) Cut a polyethylene homopolymer film into circular pieces with a diameter of 19 mm as the separator;

[0270] (8) In a glove box filled with argon, stack the positive electrode plate, negative electrode plate, and separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0271] Comparative Example 2

[0272] Comparative Example 2 is basically the same as Example 1, the difference is that the positive electrode material is only modified by a titanate coupling agent, and the specific method is as follows:

[0273] (1) Pretreatment of positive electrode material: Weigh 100 g of lithium nickel cobalt manganate positive electrode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811), disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 positive electrode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0274] (2) Preparation of pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator in an alcohol-water solution, and ultrasonically disperse it to obtain a glacial acetic acid alcohol-water solution. The mass ratio of the alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L; the ultrasonic conditions include: a frequency of 30 kHz and a time of 10 min.

[0275] (3) Mix the cathode material and the modifier: Add 4.16 g of tetrabutyl titanate coupling agent to the NCM811 cathode material dispersion obtained in (1), so that the mass ratio of the NCM811 cathode material to the tetrabutyl titanate coupling agent is about 96:4. Then, use magnetic stirring to form a uniform mixture. The stirring speed is 1000 r / min and the time is 30 min.

[0276] (4) Adjust the pH value and dry: Use the glacial acetic acid alcohol aqueous solution in (2) to adjust the pH of the mixture in (3) to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, where the stirring speed is 1000 r / min. After the pH of the mixture is stable, put it into an oven and dry it until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 cathode material modified by tetrabutyl titanate.

[0277] (5) Prepare the premixed modified cathode mixture: Weigh 94 g of the NCM811 cathode material modified by tetrabutyl titanate, 3 g of acetylene black, and 3 g of polytetrafluoroethylene, and use stirring to mix them to obtain the premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified by tetrabutyl titanate, the conductive agent acetylene black, and the binder polytetrafluoroethylene is 94:3:3. The stirring and mixing rate is 1500 rpm and the mixing time is 2 h.

[0278] (6) Prepare the fibrillated modified cathode mixture: Use air jet milling to crush, disperse, and fibrillate the premixed modified cathode mixture obtained in step (5) to obtain the fibrillated modified NCM811 cathode mixture. The speed of air jet milling is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0279] (7) Prepare the dry-process modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, perform hot rolling on the fibrillated modified NCM811 cathode mixture to obtain a dry-process modified NCM811 cathode film with a thickness of 300 μm.

[0280] (8) Prepare the cathode electrode film: At a temperature of 300 °C, roll press the dry-process modified NCM811 cathode film obtained in S2.3 and the aluminum foil current collector so that the dry-process modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-process modified NCM811 cathode electrode film with a thickness of 50 μm.

[0281] (9) Select the anode material (silicon-graphite composite material), cut the anode material into circular pieces with a diameter of 16 mm to be used as the anode electrode;

[0282] (10) Cut the positive electrode film obtained in S2.4 above into circular pieces with a diameter of 14 mm to serve as the positive electrode plate.

[0283] (11) Cut the polyethylene homopolymer film into circular pieces with a diameter of 19 mm to serve as the separator.

[0284] (12) In a glove box filled with argon, stack the positive electrode plate, negative electrode plate, and separator, add the electrolyte and seal to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1M LiPF6 in FEC-DMC (volume ratio 1:4).

[0285] Comparative Example 3

[0286] Comparative Example 3 is basically the same as Example 1, except that the positive electrode material is only modified by orthosilicate ester, and the specific method is as follows:

[0287] (1) Pretreatment of the positive electrode material: Weigh 100 g of lithium nickel cobalt manganese oxide positive electrode material (LiNi0.8Co0.1Mn0.1O2, hereinafter referred to as NCM811) and disperse it in 500 ml of ethanol solvent by ball milling to obtain a uniform NCM811 positive electrode material dispersion. The concentration of NCM811 is 0.2 g / ml; the dispersion rate of ball milling is 300 rpm and the time is 15 min.

[0288] (2) Prepare the pH adjustment solution: Weigh 120 g of glacial acetic acid pH regulator in an alcohol-water solution and disperse it fully by ultrasonic method to obtain a glacial acetic acid alcohol-water solution. The mass ratio of alcohol solvent to deionized water in the alcohol-water solution is 90:10, and the concentration of glacial acetic acid is 2 mol / L; the ultrasonic conditions include: frequency of 30 kHz and time of 10 min.

[0289] (3) Mix the positive electrode material and the modifier: Add 4.16 g of tetraethyl orthosilicate to the NCM811 positive electrode material dispersion obtained in S1.1, so that the mass ratio of NCM811 positive electrode material to tetraethyl orthosilicate is about 96:4, and then use magnetic stirring to form a uniform mixture. The stirring speed is 1000 r / min and the time is 30 min.

[0290] (4) Adjust the pH value and dry: Use the glacial acetic acid alcohol-water solution in (2) to adjust the pH of the mixture in (3) to 4.5. Keep stirring during the adjustment process, and then continue to stir for 1 h and repeat the pH test to ensure that the pH of the mixture is 4.5, where the stirring speed is 1000 r / min; after the pH of the mixture is stable, put it into an oven and dry until the solvent is completely removed. The drying temperature is 60 °C and the drying time is 24 h. Finally, obtain the NCM811 positive electrode material modified by tetraethyl orthosilicate modifier.

[0291] (5) Preparation of premixed modified cathode mixture: Weigh 94 g of NCM811 cathode material modified with tetraethyl orthosilicate, 3 g of acetylene black, and 3 g of polytetrafluoroethylene, and mix them by stirring to obtain a premixed modified cathode mixture. The mass ratio of the NCM811 cathode material modified with tetraethyl orthosilicate modifier, the conductive agent acetylene black, and the binder polytetrafluoroethylene is 94:3:3; the stirring and mixing rate is 1500 rpm, and the mixing time is 2 h.

[0292] (6) Preparation of fibrillated modified cathode mixture: Subject the premixed modified cathode mixture obtained in step (5) to crushing, dispersion, and fibrillation treatment using air jet milling to obtain a fibrillated modified NCM811 cathode mixture. The air jet milling speed is 50 m / s, the air pressure is 0.5 MPa, the feeding pressure is 0.5 MPa, and the temperature is 30 °C.

[0293] (7) Preparation of dry-process modified cathode film: Under the conditions of a pressure of 500 kPa and a temperature of 250 °C, perform hot rolling on the fibrillated modified NCM811 cathode mixture to obtain a dry-process modified NCM811 cathode film with a thickness of 300 μm.

[0294] (8) Preparation of cathode electrode film: At a temperature of 300 °C, roll press the dry-process modified NCM811 cathode film obtained in S2.3 with an aluminum foil current collector so that the dry-process modified NCM811 cathode film is compounded with the aluminum foil current collector to obtain a dry-process modified NCM811 cathode electrode film with a thickness of 50 μm.

[0295] (9) Select a negative electrode material (silicon-graphite composite material), cut the negative electrode material into circular pieces with a diameter of 16 mm to serve as negative electrode plates;

[0296] (10) Cut the cathode electrode film obtained in S2.4 above into circular pieces with a diameter of 14 mm to serve as cathode plates;

[0297] (11) Cut a polyethylene homopolymer film into circular pieces with a diameter of 19 mm to serve as a separator;

[0298] (12) In a glove box filled with argon, stack the cathode plate, the negative electrode plate, and the separator, add an electrolyte and seal it to assemble a button-type lithium-ion battery. Among them, the electrolyte is 1 M LiPF6 in FEC-DMC (volume ratio 1:4).

[0299] The cycle performance and discharge capacity retention rate of the batteries of Examples 1-9 and Comparative Examples 1-3 were tested using the Xinwei charge and discharge test system, and the first efficiency and discharge capacity retention rate of the batteries of Examples 1-9 and Comparative Examples 1-3 were obtained as shown in Table 1. At the same time, the test curve graphs of Example 1 and Comparative Example 1 are exemplarily shown: The first cycle charge and discharge curve graphs of the batteries of Example 1 and Comparative Example 1 (as shown in Table 1) Figure 1 ), and the cycle curves of the discharge capacity retention rate of the batteries of Example 1 and Comparative Example 1 were obtained (as shown in Figure 2 shown).

[0300] Table 1

[0301]

[0302]

[0303] As can be seen from Table 1, the first effect and capacity retention rate of the batteries of different embodiments and comparative examples after 100 cycles were tested and the results were summarized. Compared with the results of comparative example 1, Examples 1, 2 and 3 show higher first effect and capacity retention rate, indicating that the composite modifier makes the materials inside the dry-process positive electrode membrane contact more closely, the positive electrode layer structure is more stable, and can adapt to the volume expansion of the positive electrode material caused by the cycle, so it shows better performance; at the same time, the composite modifier is also applicable to other positive electrode materials, and the amount of the composite modifier can be flexibly adjusted within a certain range. The comparison of the results of Example 1 and Comparative Examples 1-3 shows that the additive can significantly improve the battery performance, and the comprehensive performance of the composite modifier is better than that of a single additive. In Examples 4 and 5, the amount of binder is reduced in the positive electrode formula. Compared with Comparative Example 1, the results of Example 4 show that the battery system with an appropriate amount of composite modifier added can still maintain a high first effect and capacity retention rate when the amount of binder in the positive electrode formula is reduced, and the composite modifier added in Example 5 is only 0.5% and can still play its role. The comparison of the results of Examples 6-9 shows that the addition ratio of the two types of modifiers in the composite modifier can be flexibly adjusted within a certain range, and a better improvement effect is shown when the proportion of orthosilicate is higher.

[0304] The accompanying drawings of this application specification exemplarily show the test curve diagrams of Example 1 and Comparative Example 1. Figure 1 The first cycle charge and discharge curves of the battery of Example 1 and the battery of Comparative Example 1 are shown, wherein the test voltage range is 2.7V to 4.2V, and the charge and discharge current is 0.1C. Figure 1It can be seen that, compared with the battery of Comparative Example 1, the charge-discharge polarization of the battery of Example 1 is smaller and the first charge-discharge efficiency is higher. The first efficiency of the battery of Example 1 is 85.82%, while that of the battery of the comparative example is 77.85%. This result shows that the internal materials of the dry-modified NCM811 cathode electrode film prepared in Example 1 of the present application have good contact, and the battery prepared in Example 1 of the present application exhibits higher charge-discharge efficiency and lower polarization.

[0305] Figure 2 Figure 4 shows the capacity retention rate diagrams of the batteries of Example 1 and Comparative Example 1 after 100 charge-discharge cycles, where the test voltage range is 2.7V to 4.2V, the charge-discharge activation current in the first three cycles is 0.1C, and then it is cycled 100 times with 0.2C charge / 0.5C discharge. Example 1 shows a higher capacity retention rate compared to Comparative Example 1, indicating that the dry electrode preparation strategy of pre-surface modification of the cathode material can significantly improve the cycle stability of the battery.

[0306] At the same time, a scanning electron microscope test was performed on the cross-section of the dry-modified NCM811 cathode electrode film in Example 1, and the distribution and morphology results of each material inside the electrode are as Figure 3 and Figure 4 shown. As can be seen from Figure 3 Figure 5, the fibrous binder is evenly distributed in the electrode in a cobweb drawing state. Although the binder fibers are not densely distributed, as can be seen from Figure 4 Figure 6, the distribution of each material inside the cathode is uniform and the contact is good. Therefore, after pre-surface treatment of the cathode material, even with less binder, uniform mixing and close contact between the materials can be achieved.

[0307] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for modifying a cathode material, characterized in that, it includes: S1.1: Prepare a cathode material dispersion; S1.2: Add a composite modifier to the cathode material dispersion to form a mixed solution for modifying the cathode material. The composite modifier includes a titanate coupling agent and an orthosilicate. The mass ratio of the cathode material to the composite modifier is (99.5:0.5)-(90:10), and the mass ratio of the titanate coupling agent to the orthosilicate is (1:9)-(9:1).

2. The method for modifying a cathode material according to claim 1, characterized in that, the titanate coupling agent includes one or more of tetrabutyl titanate, diisooctanoyl titanate ethyl ester, triisooctanoyl titanate isopropyl ester, tetra-isopropyl di(phosphite dioctyl ester) titanate, isopropoxy tris(dodecylbenzenesulfonyloxy) titanate, isopropyl trioleate titanate, isopropyl dioleate (dioctyl phosphate acyloxy) titanate; and / or the orthosilicate includes one or more of methyl orthosilicate, ethyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate.

3. The method for modifying a cathode material according to claim 1, characterized in that, in S1.2, after adding the composite modifier to the cathode material dispersion, apply an ultrasonic frequency of 30 - 50 kHz and continue for 5 - 20 min, or perform magnetic stirring at a rotation speed of 300 - 1000 r / min for 10 - 30 min to fully mix the cathode material and the composite modifier.

4. The method for modifying a cathode material according to claim 1, characterized in that, it further includes: S1.3: Add a PH adjusting solution to adjust the PH value of the mixed solution to 4 - 5, and perform a drying treatment on the mixed solution with a PH value of 4 - 5 to obtain a cathode material modified with a composite modifier.

5. The method for modifying a cathode material according to claim 4, characterized in that, before S1.3, add a PH regulator to an alcohol aqueous solution and fully disperse it to prepare the PH adjusting solution with a concentration of 1 - 3 mol / L.

6. The method for modifying a cathode material according to claim 5, characterized in that, the PH regulator includes at least one of formic acid, glacial acetic acid, and oxalic acid; and / or the alcohol aqueous solution includes an alcohol solvent and deionized water with a mass ratio of (90:10)-(70:30); and / or the alcohol solvent includes at least one of methanol, ethanol, ethylene glycol, and isopropyl alcohol.

7. The method for modifying a cathode material according to claim 4, characterized in that, in S1.3, add the PH adjusting solution to the mixed solution while stirring. After the PH adjusting solution is completely added, continue stirring, measure the PH value at intervals of a set time. After the PH value stabilizes between 4 - 5, dry the mixed solution to obtain a cathode material modified with a composite modifier.

8. The method for modifying a cathode material according to claim 7, characterized in that, in S1.3, stir at a rotation speed of 200 - 1200 r / min, and the set time is 0.5 - 1 h.

9. A method for dry-preparing a positive electrode film of a lithium battery, characterized in that, it includes: S2.1, mixing the positive electrode material modified by the composite modifier obtained after the positive electrode material modification method described in any one of claims 1-8 with a conductive agent and a binder to prepare a premixed modified positive electrode mixture; S2.2, performing crushing, dispersion and fibrillation treatment on the premixed modified positive electrode mixture to obtain a fibrillated modified positive electrode mixture; S2.3, performing hot rolling treatment on the fibrillated modified positive electrode mixture to obtain a dry-modified positive electrode film; S2.4, compounding the dry-modified positive electrode film with a current collector to obtain a positive electrode film.

10. The method for dry-preparing a positive electrode film of a lithium battery according to claim 9, characterized in that, in S2.1, the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, carbon fiber and carbon nanotube; and / or the binder includes at least one of ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer; and / or the mass ratio of the positive electrode material modified by the composite modifier, the conductive agent and the binder is (90-96):(2-5):(2-5).

11. The method for dry-preparing a positive electrode film of a lithium battery according to claim 9, characterized in that, in S2.1, the positive electrode material modified by the composite modifier, the conductive agent and the binder are ball-milled and mixed at a rate of 100-350 rpm for 0.5-3 h, or stirred and mixed at a rate of 500-2500 rpm for 0.5-3 h to prepare a premixed modified positive electrode mixture; and / or, in S2.2, the crushing and dispersion includes: the high-speed dispersion rate is 10000-20000 rpm, the dispersion time is 5-120 min, the air flow pulverization speed is 20-100 m / s, the air flow pressure is 0.3-1.2 MPa, the feeding pressure is 0.3-1.0 MPa, and the temperature is 20-60 °C; and / or, in S2.3, the hot rolling treatment of the fibrillated modified positive electrode mixture includes: performing hot rolling treatment on the fibrillated modified positive electrode mixture at a pressure of 80-800 kPa and a temperature of 40-300 °C to prepare the dry-modified positive electrode film with a thickness of 100-500 μm.

12. The method for dry-preparing a positive electrode film of a lithium battery according to claim 9, characterized in that, in S2.4, the dry-modified positive electrode film and the current collector are compounded by hot rolling or high-temperature roll pressing to form a positive electrode film with a thickness of 50-100 μm, wherein the pressure of hot rolling is 200-600 kPa, the temperature is 40-300 °C, and the temperature of high-temperature roll pressing is 200-300 °C.

13. A positive electrode material, characterized in that, The surface of the positive electrode material is coated with a titanate coupling agent and a tetraorthosilicate, or the positive electrode material is processed by the positive electrode material modification method described in any one of claims 1-8; wherein, the positive electrode material is modified with a composite modifier, the composite modifier includes a titanate coupling agent and a tetraorthosilicate, the mass ratio of the positive electrode material to the composite modifier is (99.5:0.5)-(90:10), and the mass ratio of the titanate coupling agent to the tetraorthosilicate is (1:9)-(9:1).

14. A positive electrode film Characterized in that It includes a positive electrode film and a current collector, and the positive electrode film is made of the positive electrode material described in claim 13; Or the positive electrode film is processed by the method for dry-preparing a positive electrode film of a lithium battery described in any one of claims 9-12.

15. A lithium ion battery Characterized in that It includes The positive electrode material described in claim 13; Or, the positive electrode film described in claim 14.

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