CN113937284B

CN113937284B - Film for battery electrode and preparation method thereof

Info

Publication number: CN113937284B
Application number: CN202010673302.0A
Authority: CN
Inventors: 沙玉静; 李硕宇; 夏圣安
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-07-14
Filing date: 2020-07-14
Publication date: 2023-09-22
Anticipated expiration: 2040-07-14
Also published as: CN113937284A; WO2022012357A1

Abstract

The embodiment of the application provides a film for a battery electrode, which comprises a fibrillated network matrix formed by interweaving fibrillated binder and dry particles distributed on the fibrillated network matrix, wherein the dry particles comprise functional material particles and conductive agent particles, part of the dry particles have a first size, and the rest of the dry particles have other sizes, and the other sizes are smaller than 1/2 of the first size; the dry particles having the first size are orderly arranged, and the dry particles having the other sizes are filled in the particle gaps of the dry particles having the first size, which are smaller than the first size. Because each dry particle is not randomly distributed in the film, each dry particle is not easy to agglomerate, so that the film has high continuity and integrity, and when the film is used for a battery electrode, the functional material can well exert functional characteristics, and the battery performance is improved. The embodiment of the application also provides a preparation method of the film, an electrode plate, an electrochemical cell and a terminal.

Description

Film for battery electrode and preparation method thereof

Technical Field

The embodiment of the application relates to the technical field of electrochemical cells, in particular to a film for a battery electrode, a preparation method of the film, an electrode plate, an electrochemical cell and a terminal.

Background

With the development of economy and science, the industries of portable electronic devices (mobile phones, tablet computers, notebook computers), unmanned aerial vehicles, electric vehicles and the like are in urgent need of energy storage devices with higher energy density, longer cycle life and safer. In order to achieve the above requirements, the industry generally adopts measures to introduce proper functional materials (such as lithium supplementing agents, flame retardants, etc.) into the lithium ion battery system. However, only a small portion of the functional materials can be directly added to the electrolyte, and most of the functional materials need to be introduced by a more compatible electrode sheet preparation technology to function in the battery. The traditional wet electrode slice preparation process for introducing the functional material is to mix the electrode active material, the functional material, the solvent and the like into slurry, then coat and dry the slurry on a matrix to form a film, but the functional material with active chemical properties such as a lithium supplementing agent (such as metal lithium) and the like is easy to explode in a humid environment and is not suitable for being introduced through the traditional wet electrode slice preparation process. The solvent-free dry electrode film technique solves the problem that the functional material may be incompatible with the processing environment such as solvent in the wet process, and specifically applies a high shear force to the dry binder particles to fibrillate them and load the various functional material particles thereon. However, since there is no solvent, in the conventional dry electrode film, the particles are randomly distributed and are liable to be agglomerated, which affects the performance of the battery to optimize the performance of the battery, and even deteriorates the energy density, the cycle ability, the safety, and the like of the battery.

Disclosure of Invention

In view of the above, the embodiment of the application provides a film prepared by a dry process, wherein dry particles in the film are not agglomerated, the uniformity of the film is good, and when the film is used for a battery electrode, the dry particles can well exert corresponding characteristics, so that the battery performance is improved.

Specifically, a first aspect of the embodiment of the present application provides a film for a battery electrode, the film including a fibrillated network matrix formed by interlacing a fibrillated binder and dry particles distributed on the fibrillated network matrix, the dry particles including functional material particles and conductive agent particles, part of the dry particles having a first size, and the rest of the dry particles having other sizes, the other sizes being less than 1/2 of the first size; the dry particles having the first size are orderly arranged, and the dry particles having the other sizes are filled in the particle gaps of the dry particles having the first size, which are smaller than the first size.

In the film, the dry particles are not randomly distributed on a fibrillated network matrix formed by the fibrillated binder, but the dry particles with the first size and the largest relative particle size are orderly arranged, and the dry particles with other sizes and smaller relative particle sizes are filled in the particle gaps of the dry particles with the first size, so that the dry particles form stable and orderly arrangement, and the dry particles are not easy to agglomerate, so that the film has good continuity, high integrity and high stability. Therefore, when the film is used for a battery electrode, the functional characteristics of each particle can be better exerted, and the relevant performance of the battery is improved; nor is the battery energy density, cycle ability, safety, etc. deteriorated.

In an embodiment of the present application, the first dimension is in the range of 1 μm to 50 μm; the other dimensions include one or more different size particle sizes, the other dimensions being in the range of 30nm-7 μm. The proper size can lead the distribution of dry particles to be tighter, the loading of the dry particles to be large, and ensure the structure of the film to be more stable.

In an embodiment of the present application, the functional material particles include at least one of an active ion extender, a flame retardant, and an expansion slowing agent. The active ion supplement can effectively improve the energy density of the battery; the flame retardant can improve the flame retardant property of the battery and the safety of the battery; and the expansion slowing agent can effectively relieve the expansion of the electrode material and improve the cycle stability of the battery. In an embodiment of the present application, the active ion supplement includes one of a lithium supplement, a sodium supplement, a potassium supplement, a magnesium supplement, a zinc supplement, and an aluminum supplement.

In an embodiment of the present application, the D50 particle diameter of the functional material particles is in the range of 30nm to 50 μm. The sizes of the functional material particles with different types and different functions can be flexibly adjusted according to the different specific functions and actual application scenes.

In the embodiment of the application, the particle size distribution of the dry particles of each different material meets the requirement that the (D90 particle size-D10 particle size)/D50 particle size is less than 1.5. The dry particles of different materials have higher size concentration, are convenient for uniform and orderly distribution in a fibrillated network matrix, further can improve the quality of films loaded with the dry particles, can exert the corresponding characteristics of the dry particles to the greatest extent, and ensure the quality consistency and the functional reproducibility of films of different batches.

In an embodiment of the application, the film has a thickness of greater than or equal to 30 μm. The thickness is greater than that of a film prepared by the existing wet process, and contains no solvent residues. In one embodiment of the application, the film has a thickness of 30 μm to 300. Mu.m.

In some embodiments of the application, the functional material comprises 70% to 99% by mass of the film. The mass ratio can ensure that the film has a stable structure and expected good mechanical properties, so that the load capacity of the functional material in the film is large, the local aggregation phenomenon can not be generated, and the performance of the battery can be further improved to the greatest extent.

In still other embodiments of the present application, the dry particles further comprise electrode active material particles. At this time, the thin film may be used as an active material layer of the electrode sheet.

In an embodiment of the present application, the D50 particle diameter of the electrode active material particles is in the range of 1 to 50 μm. The electrode active material particles with larger size are closely arranged in the film, so that the loading capacity of the electrode active material particles in the film is larger, and the energy density of the battery can be improved.

In an embodiment of the present application, the particle size distribution of the electrode active material particles satisfies (D90 particle size-D10 particle size)/D50 particle size <1.5. The electrode active material particles have higher size concentration, are convenient for the uniform and orderly distribution of the electrode active material particles in a fibrillated network matrix, further can improve the quality of the film containing the electrode active material, exert better performance, and ensure the quality consistency and the functional reproducibility of films in different batches.

In one embodiment of the present application, the mass of the electrode active material is 70-99% of the mass of the thin film. In a specific embodiment of the present application, the mass of the functional material accounts for 0.05% -30% of the mass of the film. The mass ratio can ensure the maximum load of the electrode active material, so that each dry particle in the film can be uniformly distributed, and the battery made of the film has high specific capacity and good additional function brought by functional materials.

According to the film provided by the first aspect of the embodiment of the application, the dry particles are not randomly distributed on the fibrillated network matrix formed by the fibrillated binder, but the dry particles with the first size and the largest relative size are orderly arranged, and the dry particles with other sizes and smaller relative sizes are filled in the particle gaps of the dry particles with the first size, so that stable and orderly arrangement is formed, the particles are not easy to agglomerate, the film has good continuity, high integrity and high stability, and when the film is applied to a battery electrode, the characteristics of the particles, especially the functional characteristics of functional materials, can be better exerted, and the relevant performance of the battery is improved.

The second aspect of the embodiment of the application also provides a preparation method of the film for the battery electrode, which comprises the following steps:

providing dry particles comprising particles of a functional material and particles of a conductive agent, a portion of the dry particles having a first size, the remainder of the dry particles having other sizes, the other sizes being less than 1/2 of the first size; preparing a first mixture of fibrillatable binder particles and dry particles having said first size in the presence of a shielding gas;

under the condition of introducing physical field intervention, carrying out high-pressure shearing on the first mixture so as to fibrillate the binder particles, orderly arranging the functional material particles with the first size, then adding the dry particles with the other sizes, and continuing carrying out high-pressure shearing to obtain a second mixture;

pressing the second mixed material to obtain a film; wherein the film comprises a fibrillated network matrix of the fibrillated binder interwoven with the dry particles distributed on the fibrillated network matrix; the dry particles with the first size are arranged in an array to form an ordered structure, and the dry particles with the other sizes are filled in the particle gaps of the dry particles with the first size, wherein the particle gaps are smaller than the first size.

In an embodiment of the present application, the physical field intervention includes at least one of ultrasound concussion and magnetic field intervention.

In one embodiment of the application, the ultrasonic frequency of the ultrasonic vibration is greater than or equal to 20KHz, and the ultrasonic power is greater than or equal to 20W. In one embodiment of the present application, the magnetic field strength of the magnetic field intervention is greater than or equal to 0.1T.

In an embodiment of the present application, the D50 particle size of the binder particles is 1 μm to 50. Mu.m. The larger size binder particles can facilitate the formation of a fibrillated network matrix that is uniformly interwoven, highly elastic, and sufficiently viscous.

In certain embodiments of the present application, in the first mixture, the dry particles having the first size further comprise electrode active material particles.

In an embodiment of the present application, the dry particles having the other sizes are added in batches in order of size from large to small. Thus, the dry particles with the first size and the dry particles with other sizes can be closely and orderly arranged, and the uniform arrangement of each dry particle in the film is better improved.

In an embodiment of the present application, in order to make the distribution of different materials of various sizes in the film more uniform, the particle size distribution of the dry particles of each different material satisfies (D90 particle size-D10 particle size)/D50 particle size <1.5.

According to the preparation method of the film provided by the second aspect of the embodiment of the application, the dry particles with the first size and the dry particles with other sizes with the largest relative size are sequentially sheared with the binder particles under high pressure, the dry particles with the first size are closely and orderly arranged through physical field intervention, and the dry particles with other sizes with smaller relative sizes are filled in the particle gaps of the dry particles with the first size, so that the dry particles are not easy to agglomerate, and the film with good continuity, high integrity and good stability is obtained. In addition, the preparation method does not involve the use of solvents, liquids and processing aids, and has strong universality and low cost.

A third aspect of the embodiment of the present application further provides an electrode sheet, where the electrode sheet includes a current collector and the thin film according to the first aspect of the embodiment of the present application disposed on the current collector. The electrode plate has stable structure, high flatness, high integrity and good continuity of the contained film, and the electrode plate containing the film can be used for providing an electrochemical cell with improved electrochemical performance.

In some embodiments of the application, the electrode sheet further includes an electrode active material layer disposed between the current collector and the thin film.

In still other embodiments of the present application, the thin film serves as an electrode active material layer of the electrode sheet. At this time, the dry particles further include electrode active material particles.

The fourth aspect of the embodiment of the application also provides an electrochemical cell, which comprises a positive electrode, a negative electrode, a separator and electrolyte, wherein the separator and the electrolyte are positioned between the positive electrode and the negative electrode, and/or the positive electrode and/or the negative electrode comprise the electrode slice of the fourth aspect of the embodiment of the application. The electrochemical cell has high energy density, long cycle life and high safety.

A fifth aspect of the embodiment of the present application further provides a terminal, where the terminal includes a housing, a main board located inside the housing, and a battery, where the battery includes the electrochemical cell according to the fourth aspect of the embodiment of the present application, and the electrochemical cell is configured to supply power to the terminal. The terminal can be electronic products such as mobile phones, notebooks, tablet computers, portable computers, intelligent wearing products and the like.

Drawings

FIG. 1a is a schematic plan view of a dry particle distribution in a film according to one embodiment of the present application;

FIG. 1b is a schematic perspective view of a dry particle distribution in a film according to one embodiment of the present application;

Fig. 2 is a schematic structural view of an electrode sheet according to an embodiment of the present application;

fig. 3 is a schematic structural view of an electrode sheet according to another embodiment of the present application;

fig. 4 is a schematic structural diagram of a terminal according to an embodiment of the present application;

fig. 5 is a photograph comparison of the battery cathodes of example 2 (a) and comparative example 2 (b) of the present application after full power disassembly.

Detailed Description

Embodiments of the present application will be described below with reference to the accompanying drawings.

Referring to fig. 1a and 1b together, an embodiment of the present application provides a film 100, which is prepared by a dry process, and includes a fibrillated binder and dry particles 2, wherein the fibrillated binder is interwoven into a fibrillated network matrix 1, and the dry particles 2 are distributed on the fibrillated network matrix 1; wherein the dry particles 2 comprise particles of functional material and particles of conductive agent, part of the dry particles having a first size, the remaining dry particles having other sizes, and the other sizes being less than 1/2 of the first size; the dry particles 21 having the first size are arranged in order, the particle gaps of the dry particles 21 having the first size are smaller than the first size, and the dry particles 22 having the other sizes are filled in the particle gaps of the dry particles 21 having the first size.

In the film 100 according to the embodiment of the present application, the dry particles are not randomly distributed on the fibrillated network matrix formed by the fibrillating binder, but the dry particles having the first size with the largest relative particle size are orderly arranged, and the dry particles having other sizes with smaller relative particle sizes are filled in the particle gaps of the dry particles having the first size, so that the dry particles form a stable and orderly arrangement, and the dry particles are not easy to agglomerate, so that the film has good continuity, high integrity and high stability.

In the present application, "the particle gap of the dry particles 21 having the first size is smaller than the first size" means that any adjacent two dry particles 21 having the first size cannot be refilled with the third dry particle 21 having the first size, that is, the dry particles 21 having the first size are closely and orderly arranged to form a "closely arranged structure". The "ordered arrangement" may be specifically an array arrangement, for example, an array form of a×b×c, where a, b, and c are positive integers.

In the film 100 of the three-dimensional structure (see fig. 1 b), 6 to 12 dry particles having the first size are around each dry particle having the first size in the embodiment of the present application. In this way, the arrangement of the dry particles 21 having the first size is compact, which is helpful to increase the distribution density of the dry particles in the film 100, and to increase the electrochemical performance such as the energy density of the battery when the film 100 is used in the battery.

In an embodiment of the present application, the film 100 has a void fraction of less than 30%. In some embodiments, the void fraction of film 100 may be less than 20%, less than 10%, or even less than 5% or less than 1%. The smaller void ratio represents that the mutual filling degree between any adjacent dry particles 2 in the film 100 is high, the compactness degree is large, the dry particles in the film 100 are more stably and orderly arranged, and the film has a stable structure and good mechanical property.

The term "dry particles" in the context of the present application encompasses powders, spheres, flakes, fibers, tubes, and other particles of other shapes and aspect ratios. Wherein the first size for spherical or spheroidal particles/powders refers to their D50 particle size, and for non-spherical particles such as flakes, fibers, tubes, strips, etc., the first size refers to the length-width dimension.

In an embodiment of the present application, the size of the dry particles 2 may be in the range of 30nm to 50 μm. Wherein the first dimension may be in the range of 1 μm to 50 μm; other dimensions may be in the range of 30nm-10 μm. In some embodiments, the first dimension may be in the range of 2 μm-30 μm, 5 μm-50 μm, 8 μm-20 μm, or 3 μm-15 μm. Other sizes may be in the range of 30nm-7 μm, 30nm-1 μm, 30nm-500nm, or 50nm-200nm, as long as "other sizes less than 1/2 of the first size" is satisfied, which may facilitate the filling of the dry particles having other sizes in the gaps between the closely arranged dry particles having the first size. In some embodiments of the application, the first dimension may be in the range of 3 μm-15 μm, and the other dimensions may be in the range of 30nm-1 μm. Other dimensions may include one or more different dimensions in the present application. For example, more than 2 different sizes are included. For example, the dry particles may include, in addition to the dry particles having the first size, dry particles having the second size, dry particles having the third size, and the third size being different from the second size, both the second size and the third size being smaller than 1/2 of the first size, which may be filled in the particle gaps of the closely and orderly arranged dry particles having the first size.

In the present application, the dry particles having the same size may be the same or different in material. Specifically, the two kinds of functional material particles (e.g., lithium-supplementing agent particles) having different materials may each have the first size, or the two kinds of lithium-supplementing agent particles having different materials and the electrode active material particles below may each have the first size.

In embodiments of the present application, the fibrillated network matrix 1 may be used to entrap, bond, support the dry particles 2 described above. Specifically, the dry particles 2 are entangled and captured by the fibrillated network matrix 1, and the fibrillated network matrix 1 also plays a certain supporting role for the dry particles 2, and the dry particles 2 can be bonded together by the fibrillated binder.

In the embodiment of the present application, the material of the fibrillated network substrate 1 may be a chain type polymer binder. The chain polymeric binders can facilitate the formation of a fibrillated network matrix under high shear forces. Specifically, the chain type polymer binder may include one or more of cellulose and its derivatives, polyolefin, fluorine-containing polymer, polyacrylic acid (PAA), polyacrylate (such as polymethyl methacrylate (PMMA)), polyacrylonitrile (PAN), polyethylene oxide (PEO), polyimide (PI), styrene Butadiene Rubber (SBR), and copolymers thereof. Among them, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF 2), polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP) and the like are exemplified as the fluorine-containing polymer, and polypropylene (PP), polyethylene (PE) and the like are exemplified as the polyolefin. Examples of the cellulose and its derivatives include carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), and the like. In the embodiment of the present application, the D50 particle diameter of the binder particles used to form the fibrillated network matrix 1 may be in the range of 1 μm to 50. Mu.m, and further, may be in the range of 2 μm to 20 μm or 3 μm to 15. Mu.m. The larger size of the binder particles can facilitate the formation of a fibrillated network matrix 1 that is uniformly interwoven, highly elastic, and sufficiently viscous.

In the embodiment of the application, the functional material particles can improve the energy density, the cycle performance, the safety and other performances of the battery. Wherein the functional material particles may include one or more of an active ion extender, a flame retardant, and an expansion slowing agent. After the film is assembled into a battery, corresponding functions can be performed at different stages according to different characteristics of functional materials contained in the film. Specifically, the flame retardant is a functional material which does not participate in the electrochemical process of the battery, and if the temperature of the battery is too high or the battery burns, the flame retardant can prevent the combustion process and flame propagation through heat absorption, coverage, inhibition of chain reaction and the like, so that the safety of the battery is improved. The functional material of the expansion slowing agent can provide a buffering effect in the expansion process of the electrode material, and can ease the expansion of the electrode plate, so that the cycle stability and the safety performance of the battery are improved. The active ion supplement can irreversibly release a large amount of active lithium ions in the first charge and discharge process of the battery, so as to supplement the lithium by the active ions and improve the energy density of the battery. Wherein the active ion may include one of lithium ion, sodium ion, potassium ion, magnesium ion and aluminum ion.

Specifically, the active ion supplement comprises one of a lithium supplement, a sodium supplement, a potassium supplement, a magnesium supplement, a zinc supplement, and an aluminum supplement. The lithium supplementing agent can release a large amount of active lithium ions before the electrode active material of the battery in the formation stage of the lithium battery so as to play a role in supplementing lithium. The lithium replenishing agent includes, but is not limited to, lithium metal and its finished products, and may include, for example, at least one of lithium powder, stabilized lithium powder, lithium tape, lithium foil, lithium-rich metal oxide, lithium carbon composite, lithium carbon alloy, lithium silicon alloy, and the like. For lithium-rich metal oxides Li can be mentioned ₂ NiO ₂ 、Li ₆ CoO ₄ 、Li ₅ FeO ₄ 、Li ₂ O·mo (M is one or more of Fe, co, ni, mn, cu, zn, re, al, ti, zr, W and La), and the like. The residues of the different lithium-supplementing agents after release of active lithium are different, e.g. Li ₂ NiO ₂ The film as the positive electrode lithium-supplementing agent can generate LiNiO, niO, li after the formation of the battery is finished ₂ One or more of O; by Li ₆ CoO ₄ The film as the positive electrode lithium supplementing agent can generate LixCoO after the formation of the battery is finished ₄ (0＜x＜6)、CoO ₂ 、Li ₂ One or more of O; by Li ₅ FeO ₄ The film as the positive electrode lithium supplementing agent can generate LiyFeO after the formation of the battery is finished ₄ (0＜y＜5)、Fe ₂ O ₃ 、Li ₂ One or more of O.

In an embodiment of the present application, the flame retardant includes inorganic flame retardants and organic flame retardants. Among them, the inorganic flame retardant may include tellurium compounds, aluminum hydroxylates (such as aluminum hydroxide, bis (2-ethylhexanoic acid) hydroxyaluminum), magnesium hydroxide, borates, and the like; organic flame retardants may include triazines and derivatives thereof, melamine, polyphosphates, urea, dicyandiamide, and the like. Wherein the expansion reducing agent comprises at least one of glucose, phenolic resin, sodium carboxymethyl cellulose, gelatin, starch, graphene, polythiophene, carbon nano tube, polyacrylonitrile, trialkylaluminum and the like.

In the embodiment of the application, the D50 particle size of each functional material particle with different materials is in the range of 30nm-50 mu m. Further, the D50 particle diameter of the functional material particles may be 30nm to 1. Mu.m, 50nm to 200nm, 2 μm to 50. Mu.m, 5 μm to 50. Mu.m, 8 μm to 20. Mu.m, or 3 μm to 15. Mu.m. The sizes of the functional material particles of different materials can be flexibly adjusted according to the specific functions and practical application situations, and the functional material can be the dry particles 21 with the first size with the largest relative size or the dry particles 22 with other sizes. For example, the D50 particle size of the flame retardant particles may be in the range of 30nm to 500nm, acting as dry particles having other sizes, and the D50 particle size of the lithium supplement may be in the range of 2 μm to 30 μm, acting as dry particles having the first size.

In the embodiment of the application, the particle size distribution of the dry particles of each different material can meet the requirement that the (D90 particle size-D10 particle size)/D50 particle size is smaller than 1.5, and particularly the particle size distribution of the functional material particles of each different material should meet the requirement that the (D90 particle size-D10 particle size)/D50 particle size is smaller than 1.5. That is, the particle size distribution of the particles of the active ion supplement, the flame retardant, and the expansion reducing agent, respectively, is (D90 particle size-D10 particle size)/D50 particle size <1.5. The dry particles of different functional materials have higher size concentration, are convenient for uniform and orderly distribution of the dry particles of the same material in a fibrillated network matrix, further can improve the quality of the film loaded with the dry particles, fully exert better performance in a battery electrode, and ensure the quality consistency and functional reproducibility of films of different batches.

In the embodiment of the present application, the kind of the conductive agent is not particularly limited, and conventional materials in the art may be used. For example, the conductive agent may include one or more of carbon fiber, carbon nanotube, graphite, graphene, conductive carbon black, furnace black, mesophase carbon microsphere, and the like. Among these, the conductive carbon black may specifically include acetylene black, ketjen black, feeder P, 350G carbon black, and the like. The graphite may include natural graphite (e.g., flake graphite, expanded graphite), artificial graphite (e.g., KS-6, spheroidal graphite), and the like. In an embodiment of the present application, the size of the conductive agent is in the range of 30nm to 50. Mu.m. For zero-dimensional and three-dimensional conductive agents (e.g., conductive carbon black particles, furnace black particles, mesophase carbon microspheres, etc.), their D50 particle size can be less than or equal to 100nm; for a two-dimensional layered conductive agent (e.g., flake graphite, graphene, etc.), the dimension thereof refers to a transverse length-width dimension, and specifically, the length-width dimension of the flake graphite or graphene may be in the range of 1 μm to 50 μm. Wherein, for the conductive agent, the particle size distribution of the spherical or spheroidal conductive agent particles of each different material satisfies (D90 particle size-D10 particle size)/D50 particle size <1.5, so that the concentration of the size of the spherical or spheroidal conductive agent particles of each different material is higher, and the uniform conductivity is provided for the film 100 of the application.

In the embodiment of the application, the thickness of the film 100 may be thicker or thinner according to the specific application scenario. Specifically, the thickness of the film 100 may be greater than or equal to 30 μm. For example, the film thickness may be 40 μm to 60 μm,100 μm to 250 μm or 30 μm to 300 μm. In some embodiments of the application, film 100 has a thickness of 70 μm to 300 μm. The film thickness is much greater than the electrode film thickness produced by current wet processes, and the film 100 is cleaner because the film is produced by a solvent-free dry process technique, without or substantially without any liquid (e.g., solvent) and residues resulting therefrom. The thickness of the film 100 is not limited by the viscosity of the slurry and the coating mode in the wet process technology, and the film can be thicker, has high continuity and integrity and is firmer in structure. In addition, compared with the existing dry electrode film, the dry electrode film has the advantages of uniform distribution of dry particles, high continuity and integrity, firm structure and good mechanical and electrical properties.

In some embodiments of the present application, the film 100 may be disposed on the surface of an electrode active material layer of an existing electrode sheet, and used as a functional layer of the electrode sheet. At this time, the film 100 as the functional layer of the electrode sheet, in which the dry particles include only the above-described functional material particles and conductive agent particles. In this embodiment, the mass of the functional material may be 70% -99% of the total mass of the film 100. The mass ratio can ensure that the film has a stable structure and expected good mechanical properties, so that the load capacity of the functional material in the film is large, the local aggregation phenomenon can not be generated, and the performance of the battery can be further improved to the greatest extent.

In other embodiments of the present application, the dry particles in film 100 further comprise electrode active material particles. At this time, the thin film 100 of the present application may be directly disposed on the surface of the current collector, acting as an active material layer of the electrode sheet, together with the current collector, constituting the electrode sheet of the battery. In this embodiment, the mass of the electrode active material may account for 70-99% of the total mass of the thin film 100. The mass of the functional material may be 0.05% -30% of the total mass of the film 100. Under the condition of ensuring the maximum load of the electrode active material, the mass ratio can ensure that each dry particle in the film can be uniformly distributed, so that the battery made of the film has high specific capacity and good additional function brought by functional materials.

In an embodiment of the present application, the D50 particle diameter of the electrode active material particles may be in the range of 1 μm to 50 μm. The electrode active material particles are preferably used as a large-particle-diameter component in the dry particles (i.e., dry particles having a first size) to achieve a tight, ordered arrangement in the thin film, to increase the loading thereof in the thin film, and thus to increase the energy density of a battery employing the thin film. In some embodiments of the application, the D50 particle size of the electrode active material particles may be 1 μm to 20 μm. For example 1 μm to 15 μm, 2 μm to 20 μm, 3 μm to 15 μm or 8 μm to 20 μm. In addition, the particle size distribution of the electrode active material particles of each different material also meets the requirement that the (D90 particle size-D10 particle size)/D50 particle size is smaller than 1.5, so that the uniform distribution of the electrode active material particles in the film is realized, the occurrence of agglomeration is avoided, the quality of the film containing the electrode active material can be further improved, the better performance is exerted, and the quality consistency and the functional reproducibility of films in different batches are ensured.

According to the film provided by the embodiment of the application, as the dry particles are not randomly distributed on the fibrillated network matrix formed by the fibrillating adhesive, but the dry particles with the first size and the largest relative size are orderly distributed, the particle gaps are smaller than the first size, and the dry particles with other sizes are filled in the particle gaps of the dry particles with the first size, the dry particles form stable and orderly arrangement, so that the film has good continuity and high integrity, does not contain solvent residues, is not easy to agglomerate in the film, has high stability, can fully exert respective effects, and can better promote the battery performance when the film is applied to a battery electrode.

Correspondingly, the embodiment of the application also provides a preparation method of the film for the battery electrode, which comprises the following steps:

s101, providing dry particles, wherein the dry particles comprise functional material particles and conductive agent particles, part of the dry particles have a first size, the rest of the dry particles have other sizes, and the other sizes are smaller than 1/2 of the first size; preparing a first mixture of fibrillatable binder particles and dry particles having a first size in the presence of a shielding gas;

S102, under the condition of introducing physical field intervention, carrying out high-pressure shearing on the first mixture to fibrillate binder particles, orderly arranging dry particles with a first size, then adding dry particles with other sizes, and continuing carrying out high-pressure shearing to obtain a second mixture;

s103, pressing the second mixed material to obtain a film; wherein the film comprises a fibrillated network matrix formed by interweaving fibrillated binders and dry particles distributed on the fibrillated network matrix; dry particles having other sizes are filled in the particle gaps of the dry particles having the first size, which are smaller than the first size.

In step S101 of the embodiment of the present application, the D50 particle diameter of the binder particles may be in the range of 1 μm to 50. Mu.m, and further, may be in the range of 2 μm to 20 μm or 3 μm to 15. Mu.m. The larger size binder particles can facilitate the formation of a fibrillated network matrix that is uniformly interwoven, highly elastic, and sufficiently viscous.

In some embodiments of the present application, in step S101, the dry particles having the first size further include electrode active material particles. That is, the electrode active material particles may be sheared with the binder particles as a large particle size component at a high pressure.

In the embodiment of the present application, in order to make the distribution of different materials of various sizes in the film more uniform, the concentration of the sizes of the dry particles provided in step S101 may be controlled so that the particle size distribution of the dry particles of each different material satisfies (D90 particle size-D10 particle size)/D50 particle size <1.5. The distribution of the dry particles of the same material in the film is similar, and the quality consistency and the functional reproducibility of films of different batches are ensured. Among the techniques that can achieve the above-described size concentration include, but are not limited to, cyclone classification, complex frequency screening, electrostatic classification, jet classification, and the like.

In step S102 of the embodiment of the present application, if the dry particles having other sizes include a plurality of different sizes, they may be sequentially added in batches in order from large to small according to their sizes to perform high pressure shearing in batches. Or at least according to the size of the D50 particle diameter of the spherical or spheroidic particles with different materials, and the particles are added in batches from large to small. Thus, the dry particles with the first size and the dry particles with other sizes can be closely and orderly arranged, and the uniform arrangement of each dry particle in the film is better improved.

In step S102 of the present application, the physical field intervention includes at least one of ultrasonic oscillation and magnetic field intervention. Physical field intervention helps to arrange the dry particles having the first size in order. By taking ultrasonic vibration as an example, the ultrasonic vibration device can promote the reciprocating high-frequency motion of the large-particle-size components to form a highly uniform orderly arrangement state, so that the small-particle-size components added later can be filled in the gaps among the particles of the large-particle-size components. The magnetic field intervention is applied to the dry particles having magnetism to form an ordered arrangement structure, for example, electrode active material particles containing Fe, co, ni, or the like or lithium supplement particles. The physical field intervention mode of ultrasonic vibration is suitable for preparing the film containing magnetic particles and the film without the magnetic particles. Further, when the above-described film containing magnetic particles is prepared, the physical field intervention employed may include at least one of ultrasonic vibration and magnetic field intervention, and preferably, magnetic field intervention is introduced.

In some embodiments of the present application, the ultrasonic frequency of the ultrasonic oscillation may be greater than or equal to 20KHz, and the ultrasonic power may be greater than or equal to 20W. In some embodiments of the application, the magnetic field strength of the magnetic field intervention may be greater than or equal to 0.1T.

In some embodiments of the present application, the introduction of physical field intervention may not begin until high pressure shear is performed at step S102. In this case, the physical field may be applied to the outer wall of the high-pressure shearing device. In other embodiments of the present application, the introduction of physical field intervention may begin as soon as the first mixture is formulated at step S101. At this time, physical fields may be applied to the outer walls of both the mixing device used in step S101 and the high-pressure shearing device used in step S102. Of course, in some embodiments of the present application, the mixing device used in step S101 and the high pressure shearing device used in step S102 may be the same device.

In some embodiments of the present application, the preparation of the first mixture in step S101 may be performed by a common mechanical mixing method (such as stirring, grinding, dual motion mixing, etc.) without introducing high pressure gas, or by a high pressure shear mixing method with introducing high pressure gas flow. Specifically, the mixing device for forming the first mixture may include at least one of a ribbon mixer, a rotary mixer, a planetary mixer, an acoustic mixer, a microwave mixer, a twin motion mixer, a fluidized bed mixer, a ball mill, a high-speed shear mixer, a jet mill, a hammer mill, and the like. When the first mixture is prepared by high-pressure shearing and mixing (such as a high-speed shearing mixer, a jet mill, a hammer mill, etc.), the configuration of the first mixture and the high-pressure shearing can be accomplished by a device.

In step S101 of the embodiment of the present application, the shielding gas used in preparing the first mixture is a sufficiently dry gas including at least one of dry air, nitrogen, helium, hydrogen, etc., preferably a dry compressed gas supplied under high pressure. The protective gas can avoid the change of the property/function of some material particles with more active chemical property and improve the safety. In some embodiments of the application, the shielding gas is still present during the high pressure shearing of step S102. The existence of the dry protective gas in the mixing and shearing processes can improve the safety and simultaneously avoid the water in the obtained film.

In step S102 of the embodiment of the present application, the fibrillation of the binder particles is achieved by a dry, solvent-free, liquid-free high pressure shear force technique, and in particular by applying a positive or negative pressure, such as compressed gas or vacuum. In the fibrillation process, high shearing force is applied to the binder, so that the binder is physically elongated and fibrillated, and the elongated binders are intertwined and overlapped to form a thin net-shaped fibrillated network matrix. In one embodiment of the application, the high pressure air stream is used at a pressure greater than or equal to 60PSI at high pressure shear to provide adequate fibrillation of the binder particles. And may be in particular 60PSI-500PSI, or 80PSI-300PSI.

In embodiments of the present application, the devices that can fibrillate the adhesive include jet mills, pin mills, hammer mills, impact mills, and the like. In a specific embodiment, the fibrillation of the binder particles is achieved by jet-milling. The jet mill process has at least one nozzle for ejecting a high pressure air stream in addition to the conventional mechanical shearing fly cutter. In the preparation process of the first mixture, the chain type polymer binder is gradually agglomerated into blocks, a common mechanical shearing fly cutter can reduce the size of the aggregates/agglomerates formed in the mixing process to form small particles, high-pressure air flow sprayed from a nozzle of the jet mill can accelerate collision of the small particles, the binder is elongated and fibrillated, the elongated binders are mutually wound and overlapped until being interwoven to form a thin net-shaped fibrillated network matrix, and the dry particles are distributed in the fibrillated network matrix.

In step S103 of the embodiment of the present application, the pressing of the second mixed material may be performed by rolling, calendaring, or the like, and specifically may be performed by a roll press, a roll mill, a calender, a belt press, a platen press, or the like.

According to the preparation method of the film, provided by the embodiment of the application, the large-particle-size components (dry particles with the first size) and the binder particles are sheared under high pressure under the intervention of a physical field, so that the large-particle-size components are closely and orderly arranged, the small-particle-size components (dry particles with other sizes) are added to continuously conduct high-pressure shearing, and the small-particle-size components are filled in the particle gaps of the large-particle-size components, so that the dry particles are not agglomerated, and the film with good continuity, high integrity and good stability is obtained, and therefore, when the film is used for a battery electrode, the effect of each dry particle can be fully exerted, and the relevant performance of the battery is improved. The preparation method solves the problems of low battery energy density, short cycle life and poor safety of the existing dry electrode film caused by dry particle agglomeration. For example, if the film contains 3wt% of the lithium supplementing agent, the cycle life of the battery can be improved by 50% or more when the film is applied to the battery.

In addition, the whole process of the preparation method does not involve the use of solvents, liquids and processing aids, solves the problem that functional materials with active chemical properties in the field of electrode films are incompatible with wet processes such as solvents, and the like, has strong universality and is suitable for introducing materials with various properties into films; compared with the wet process, the preparation method has lower cost, can save 3-4% of cost, can prepare thicker film, and has better continuity and stability and higher integrity when the film is thicker. The method has the advantages of simple process, low cost, high efficiency, environmental protection and mass production.

Referring to fig. 2, in one embodiment of the present application, there is provided an electrode sheet 2000, the electrode sheet 2000 including a current collector 10, and an electrode active material layer 11 and a thin film 100 sequentially disposed on the current collector 10. In this embodiment, the dry particles in the thin film 100 include only the functional material particles and the conductive agent particles, but do not include the electrode active material particles. The film 100 is used as a functional layer, has high flatness, high integrity and good continuity, can endow the electrode plate with good additional functions, and improves the performances of the battery in various aspects such as energy density, cycle performance, safety performance and the like.

As previously described, the functional material particles may include one or more of active ion extenders, flame retardants, expansion slowing agents. The mass of the functional material particles accounts for 70% -99% of the total mass of the film 100. The mass ratio can ensure that the film has a stable structure and expected good mechanical properties, so that the load capacity of the functional material in the film is large, the local aggregation phenomenon can not be generated, and the performance of the battery can be further improved to the greatest extent.

In addition, in this embodiment, the void fraction of the film 100 may be less than 30%. At this time, the dry particles in the film 100 are densely distributed, the mechanical strength of the film 100 is high, the distribution of the functional material particles is more uniform and dense, and the function of the battery made of the film can be better improved.

In an embodiment of the present application, current collector 10 includes, but is not limited to, a metal foil including copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold, or silver foil, or an alloy foil including stainless steel, or an alloy including at least one element of copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold, and silver. Optionally, the alloy foil takes the above elements as main components. The metal foil may further comprise a doping element including, but not limited to, one or more of platinum, ruthenium, iron, cobalt, gold, copper, zinc, aluminum, magnesium, palladium, rhodium, silver, tungsten. The current collector 10 may be etched or roughened to form a secondary structure to facilitate effective contact with the electrode active material layer 11.

In the embodiment of the present application, the electrode active material layer 11 may be prepared on the current collector 10 by a coating method or a rolling method, and the thin film 100 may be combined with the electrode active material layer 11 by rolling, isostatic pressing, or the like. Electric powerThe electrode active material in the electrode active material layer 11 is a material that can store energy by deintercalating ions including one of lithium ions, sodium ions, potassium ions, magnesium ions, and aluminum ions. In particular, the electrode active material includes, but is not limited to, a metal, an inorganic non-metal (such as a carbon material), an oxide, a nitride, a carbide, a boride, a sulfide, a chloride, or a composite of various energy storage materials. For example, lithium, magnesium, potassium, magnesium, sulfur, phosphorus, silicon, lithium cobaltate, lithium iron phosphate, layered gradient compounds, li ₃ PO ₃ 、TiO ₂ 、Li ₄ Ti ₅ O ₁₂ 、SiO、SnO ₂ 、NiS、CuS、FeS、MnS、Ag ₂ S、TiS ₂ Etc. The electrode active material layer 11 may be a positive electrode active material layer or a negative electrode active material layer. That is, the electrode active material in the electrode active material layer 11 may be a positive electrode active material or a negative electrode active material. For lithium ion batteries, the positive electrode active material may be specifically lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt oxide (LiCoO) ₂ ) At least one of lithium manganate, lithium manganese nickelate, lithium nickel manganate, nickel Cobalt Manganese (NCM), nickel Cobalt Aluminum (NCA), and the like. The negative electrode active material may include metallic lithium, graphite, hard carbon, silicon-based materials (including elemental silicon, silicon alloys, silicon oxides, silicon carbon composites), tin-based materials (including elemental tin, tin oxides, tin-based alloys), lithium titanate (Li) ₄ Ti ₅ O ₁₂ ) And TiO ₂ At least one of the following. In addition, the electrode active material layer 11 may further include a binder, a conductive agent, and the like. The binder and the conductive agent added to the electrode active material layer 11 are not particularly limited, and conventional materials existing in the art may be used, and for example, the binder may be one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyolefin, sodium alginate, and the like. For example, the conductive agent may be one or more of conductive carbon black, artificial graphite KS6, carbon nanotubes, graphene, and the like.

The electrode sheet 2000 may be a positive electrode sheet or a negative electrode sheet. If the electrode sheet is used as a positive electrode sheet, the electrode active material layer 11 is specifically a positive electrode active material layer. The current collector 10 of the positive electrode sheet may be aluminum foil. Similarly, if the electrode sheet is a negative electrode sheet, the electrode active material layer 11 is specifically a negative electrode active material layer, and the current collector 10 of the negative electrode sheet may be a copper foil.

Referring to fig. 3, the embodiment of the present application further provides an electrode sheet 3000, where the electrode sheet 3000 includes a current collector 10 and a thin film 100 disposed on the current collector 10, and in this embodiment, dry particles in the thin film 100 include electrode active material particles, the above functional material particles, and conductive agent particles, and the thin film 100 directly serves as an electrode active material layer of the electrode sheet 3000, and the thin film 100 has high flatness, high integrity, and good continuity, and can effectively improve various performances of energy density, cycle performance, safety performance, and the like of a battery.

In this embodiment, the void fraction of film 100 is less than 30%. At this time, the arrangement of the dry particles in the film 100 is dense, which is particularly useful for increasing the distribution density of the electrode active material particles having a large particle diameter in the film 100 and increasing the specific capacity of a battery made of the film.

The materials of the current collector 10 and the electrode active material particles are as described above, and are not described herein. The film 100 may be provided on the current collector 10 by a coating method or by a rolling method such as cold pressing, hot pressing, etc. The electrode tab 3000 may be a positive electrode tab or a negative electrode tab. If the electrode sheet is used as a positive electrode sheet, the electrode active material particles in the film 100 are specifically positive electrode active material particles, and the film 100 including the positive electrode active material particles may be referred to as a "positive electrode film". Similarly, if the electrode sheet is a negative electrode sheet, the electrode active material particles in the film 100 are specifically negative electrode active material particles, and the film containing the negative electrode active material particles may be referred to as a "negative electrode film".

In the electrode sheet 3000, the mass of the electrode active material particles accounts for 70-99% of the total mass of the film 100. Further, the mass of the functional material may be 0.05% -30% of the mass of the film 100. The mass ratio can ensure the maximum load of the electrode active material, so that each dry particle in the film can be uniformly distributed, and the battery made of the film has high specific capacity and good additional function brought by functional materials.

The embodiment of the application also provides an electrochemical cell, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the diaphragm is positioned between the positive electrode and the negative electrode, and at least one of the positive electrode and the positive electrode comprises the electrode slice.

The electrochemical cell may be a secondary battery having high cycle performance and high safety. Specifically, the secondary battery may be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, an aluminum secondary battery, a zinc secondary battery, or the like, which has high cycle performance and high safety.

As shown in fig. 4, the embodiment of the present application further provides a terminal 300, where the terminal 300 may be a mobile phone, a tablet computer, a notebook computer, a portable device, an intelligent wearable product, and other electronic products, and the terminal 300 includes a housing 200 assembled outside the terminal, and a circuit board and a battery (not shown in the drawing) located inside the housing 200, where the battery is the battery provided in the embodiment of the present application, the housing 200 may include a display screen assembled at a front side of the terminal and a rear cover assembled at a rear side, and the battery may be fixed inside the rear cover to supply power to the terminal 300.

The following examples are provided to further illustrate embodiments of the application.

Example 1

This example provides a positive electrode active material with nickel cobalt manganese NCM811 and Li ₂ NiO ₂ The preparation of the lithium supplementing agent, the Carbon Nano Tube (CNTs) conductive agent, the lithium supplementing electrode film of the PVDF binder and the soft package battery assembled by the film specifically comprises the following steps:

(1) Preparing a positive electrode lithium supplementing electrode film:

raw material preparation: taking a positive electrode active material NCM811 with the D50 of 12 mu m, and removing oversized particles and fine particles in the NCM811 by a cyclone classification technology, so that the volume distribution and the number distribution (D90-D10)/D50 of the granularity are adjusted to be 1.35; taking lithium supplementing agent Li with D50 particle diameter of 5 mu m ₂ NiO ₂ Particles and binder PVDF particles having a D50 particle size of 5 μm, wherein Li ₂ NiO ₂ The particle size distribution and the number distribution of the particles and the PVDF particles satisfy (D90-D10)/D50<1.5；

The NCM811 particles and Li ₂ NiO ₂ Particles, PVDF particles and CNTs were mixed according to 88:5:5:2, under the protection of argon, adding the weighed NCM811 particles and PVDF into a mixing tank of a jet mill, and starting an ultrasonic generator and a magnetic field to ensure that the ultrasonic frequency in the mixing tank is 40kHz, the power is 40W and the magnetic field strength is 0.3T; after common mechanical fly cutter mixing is carried out for 10min, a high-pressure air valve of a jet mill is opened, high-pressure shearing is carried out on materials in a mixing tank by introducing high-pressure air flow of 60PSI (an ultrasonic generator and a magnetic field are still started during high-pressure shearing), PVDF particles are fibrillated, all particles are adhered, and after high-pressure shearing is carried out for 30min, weighed Li is added ₂ NiO ₂ Continuously shearing the particles and CNTs for 2.5 hours under high pressure to enable PVDF to be repeatedly fibrillated and enable newly added materials to be adhered, and finally rolling the obtained mixed materials into a film with the thickness of 150 mu m through a rolling device connected with a discharge hole of a jet mill;

(2) Preparation of a positive plate: covering the film prepared in the step (1) on a prepared aluminum foil current collector, hot rolling the film at 160 ℃ to combine the film with the aluminum foil, and cutting to form a positive plate;

(3) Preparation of a lithium ion battery: the positive plate is matched with a silicon-oxygen-graphite negative electrode (buckling capacity is 500mAh/g, first effect is 83%) and 1mol/L LiPF is used ₆ The EC+DEC mixed solution (the volume ratio of EC to DEC is 1:1) is used as electrolyte, and the PP/PE/PP three-layer diaphragm is used as diaphragm to manufacture the soft package battery with the thickness of about 130mAh for testing the performance of the battery.

In example 1, the lithium-supplementing agent Li having active chemical properties was prepared by argon protection during the mixing process for preparing the lithium-supplementing electrode film ₂ NiO ₂ Does not denature and deactivate, and the dry particles are not randomly distributed on a fibrillated network matrix formed by the fibrillation of the binder by introducing physical field (ultrasonic field and magnetic field) intervention during high-pressure shearing, so that the lithium supplementing agent Li ₂ NiO ₂ Can exert better lithium supplementing effect. In addition, the embodiment does not introduce any solvent when preparing the lithium-supplementing electrode film, thereby avoiding Li ₂ NiO ₂ The problems of difficult gel and coating in the pulping and homogenizing processes, and the like, is environment-friendly and saves cost.

Example 2

The embodiment provides a preparation method of a lithium supplementing electrode film with a silicon-oxygen mixed graphite negative electrode active material (Bei Terui company S500-2A, buckling capacity 500mAh/g, first effect 83%), stabilized metal lithium powder SLMP (Stabilized lithium metal powder) serving as a lithium supplementing agent SLMP, a PTFE binder and an acetylene black conductive agent, and a soft package battery assembled by the film, which specifically comprises the following steps:

(1) Preparing a negative electrode lithium supplementing electrode film:

raw material preparation: firstly, controlling the concentration of the particle size of each material by an electrostatic classification technology on raw materials such as anode active material particles (D50 particle size is 6 mu m), SLMP particles (D50 particle size is 15 mu m), PTFE particles (D50 particle size is 8 mu m) and acetylene black particles (D50 particle size is 50 nm) of silicon-oxygen mixed graphite, and ensuring that the volume distribution and the quantity distribution of the particle size of each material meet (D90-D10)/D50 <1.5;

the anode active material particles of the graded silicon-oxygen mixed graphite, SLMP particles, PTFE particles and acetylene black particles are mixed according to the following proportion of 85:5:8:2, under the protection of argon, firstly adding the weighed SLMP particles and PTFE particles into a mixing tank of a jet mill, and starting an ultrasonic generator to ensure that the ultrasonic frequency in the mixing tank is 40kHz and the power is 40W; after mixing materials for 10min by a common mechanical fly cutter, opening a high-pressure air valve of a jet mill, shearing materials in the mixing tank for 2.5h at high pressure by introducing high-pressure air flow of 60PSI, adding weighed negative electrode active material particles of silicon-oxygen mixed graphite, continuing high-pressure shearing for 2.5h (an ultrasonic generator is still started during high-pressure shearing), adding acetylene black particles, continuing high-pressure shearing for 30min, obtaining a fibrillated mixed material, and finally rolling the obtained mixed material into a film with the thickness of 100 mu m by a rolling device connected with a discharge port of the jet mill;

(2) Preparing a negative plate: covering the film prepared in the step (1) on a prepared copper foil current collector, hot rolling the film at 160 ℃ to combine the film with copper foil, and cutting to form a negative plate;

(3) Preparation of a lithium ion battery: firstly, preparing an NCM811 positive plate, specifically, uniformly stirring a nickel cobalt manganese NCM811 positive electrode active material, a Super P conductive agent and a PVDF binder according to a mass ratio of 75:10:15 to obtain positive electrode active slurry, coating the positive electrode active slurry on an aluminum foil current collector in a spin coating manner, and vacuum baking at 120 ℃ for 12 hours to form a positive electrode active material layer; then hot rolling is carried out at 160 ℃ to combine the positive electrode active material layer with aluminum foil, and a positive electrode plate is obtained after cutting;

matching the negative electrode plate with an NCM811 positive electrode plate, and adopting 1mol/L LiPF ₆ The EC+DEC mixed solution (the volume ratio of EC to DEC is 1:1) is used as electrolyte, and the PP/PE/PP three-layer diaphragm is used as diaphragm to manufacture the soft package battery with the thickness of about 130mAh for testing the performance of the battery.

Example 3

The present embodiment provides a method of using Li ₆ CoO ₄ The preparation of the lithium supplementing film which is prepared from a lithium supplementing agent, PTFE serving as a binder and Keqin black serving as a conductive agent and a soft package battery assembled by the film specifically comprises the following steps:

(1) Preparing a lithium supplementing film:

raw material preparation: li is mixed with ₆ CoO ₄ The particle (D50 particle diameter is 15 μm), PTFE particle (D50 particle diameter is 10 μm) and Keqin black particle (D50 particle diameter is 80 nm) control the concentration of each material particle diameter by electrostatic classification technology, and ensure that the volume distribution and the number distribution of each material particle diameter meet (D90-D10)/D50<1.5；

The above classified Li ₆ CoO ₄ The particles, PTFE particles and Keqin black particles are weighed according to the proportion of 7:2:1, and the weighed Li is protected by argon gas ₆ CoO ₄ Adding the particles and PTFE particles into a mixing tank of a jet mill, and starting an ultrasonic generator and a magnetic field to ensure that the ultrasonic frequency in the mixing tank is 20kHz, the power is 40W and the magnetic field strength is 0.3T; in the process of general productionAfter the mechanical fly cutter is introduced into the material mixing tank for 10min, a high-pressure air valve of a jet mill is opened, high-pressure shearing is carried out on the material in the material mixing tank for 40min by high-pressure air flow of 60PSI, then the weighed Keqin black particles are added, high-pressure shearing is continued for 20min, the fibrillated mixed material is obtained, and finally the obtained mixed material is pressed into a film with the thickness of 30 mu m, and the film is put into a sealing bag for standby;

(2) Preparation of a positive plate: uniformly stirring a nickel cobalt manganese NCM811 positive electrode active material, a Super P conductive agent and a PVDF binder according to a mass ratio of 75:10:15 to obtain positive electrode active slurry, coating the positive electrode active slurry on an aluminum foil current collector in a spin coating manner, and vacuum baking at 120 ℃ for 12 hours to form a positive electrode active material layer;

Covering the surface of the positive electrode active material layer with the film prepared in the step (1), and carrying out hot rolling at 160 ℃ to combine the film with the positive electrode active material layer, and cutting to obtain a positive electrode plate;

(3) Preparation of a lithium ion battery: the positive plate is matched with a common silicon oxide negative electrode, and 1mol/L LiPF is used ₆ The EC+DEC mixed solution (the volume ratio of EC to DEC is 1:1) is used as electrolyte, and the PP/PE/PP three-layer diaphragm is used as diaphragm to manufacture the soft package battery with the thickness of about 130mAh for testing the performance of the battery.

Fig. 2 may represent the structure of the positive electrode sheet of embodiment 3 of the present invention, and fig. 1a and 1b may represent schematic structural diagrams of the lithium supplementing film 100 on the positive electrode sheet of embodiment 3. In the figure, 10 is a positive electrode current collector, 11 is an NCM811 positive electrode active material layer, 1 is a binder PTFE, and 21 is a lithium supplementing agent Li ₆ CoO ₄ And 22 is Keqin black.

Example 4

This example provides a positive electrode active material, mg (OH), having nickel cobalt manganese NCM811 ₂ The preparation of the flame-retardant electrode film of the flame retardant, the CNTs conductive agent and the PTFE adhesive and the soft package battery assembled by the film specifically comprises the following steps:

(1) Preparing a positive electrode flame-retardant electrode film:

raw material preparation: taking positive electrode active material NCM811 with D50 of 12 μm, removing NCM8 by jet classification technology 11, and the volume distribution and the number distribution (D90-D10)/D50 of the granularity of the ultra-large particles and the fine particles are adjusted to be 1.1; and Mg (OH) ₂ The volume distribution and the number distribution of the particle sizes of the particles (D50 particle size: 100 nm) and the PTFE particles (D50 particle size: 5 μm) are satisfied (D90-D10)/D50<1.5；

The NCM811 particles and Mg (OH) ₂ Particles, PTFE particles and CNTs were mixed according to 88:5:5:2, under the protection of argon, adding weighed NCM811 particles and PVDF into a mixing tank of a jet mill, introducing argon for protection, and starting an ultrasonic generator and a magnetic field to ensure that the ultrasonic frequency in the mixing tank is 40kHz, the power is 40W, and the magnetic field strength is 0.3T; starting mechanical fly cutter mixing, opening a high-pressure air valve of the jet mill after 10min, cutting the materials in the mixing tank under high pressure by introducing high-pressure air flow of 60PSI (the ultrasonic generator and the magnetic field are still started during high-pressure cutting), and adding weighed Mg (OH) after 30min of high-pressure cutting ₂ Continuously shearing the particles and CNTs for 2.5 hours under high pressure, and finally rolling the obtained mixed material into a film with the thickness of 150 mu m through a rolling device connected with a discharge hole of a jet mill;

(3) Preparation of a lithium ion battery: the positive plate is matched with a silicon-oxygen-graphite negative electrode (buckling capacity of 500mAh/g, first effect of 83%) and 1mol/L LiPF is used ₆ The EC+DEC mixed solution (the volume ratio of EC to DEC is 1:1) is used as electrolyte, and the PP/PE/PP three-layer diaphragm is used as diaphragm to manufacture the soft package battery with the thickness of about 130mAh for testing the performance of the battery.

To highlight the beneficial effects of the examples of the present application, the following comparative examples are provided:

comparative example 1

Comparative example 1 provides a method for preparing NCM 811-containing positive electrode active material, li, using conventional dry process ₂ NiO ₂ A method for supplementing lithium to electrode film of lithium supplementing agent, CNTs conductive agent and PVDF adhesive, and a soft package battery assembled by the film.Comparative example 1 differs from example 1 in that: in the step (1), the particle size concentration of each raw material is not controlled; and directly weighing NCM811 particles and Li ₂ NiO ₂ The particles, PVDF particles and CNTs are added into a mixing tank of a jet mill, after the mixture is mixed for 10min by a common mechanical fly cutter, a high-pressure air valve of the jet mill is opened, high-pressure air flow of 60PSI is selected to shear the materials in the mixing tank for 3h, and then the high-pressure sheared mixed materials are rolled into a film with the thickness of 150 mu m by a rolling device connected with a discharge hole of the jet mill.

Comparative example 2

Comparative example 2 provides a method for preparing a lithium-supplementing electrode film containing a silicon-oxygen mixed graphite negative electrode active material, an SLMP lithium supplementing agent, a PTFE binder and an acetylene black conductive agent by adopting a traditional dry process, and a soft-package battery assembled by the film. Comparative example 2 differs from example 2 in that: in the step (1), the particle size concentration of each raw material is not controlled; and the ultrasonic generator and the magnetic field are not started in the process of shearing and mixing.

Comparative example 3

Comparative example 3 provides a method for preparing a conventional NCM811 positive electrode sheet using a conventional wet coating process, and also provides a soft pack battery assembled from the conventional positive electrode sheet, comprising the steps of:

(1) Uniformly stirring a nickel cobalt manganese NCM811 positive electrode active material, a Super P conductive agent and a PVDF binder according to a mass ratio of 75:10:15 to obtain positive electrode active slurry, coating the positive electrode active slurry on an aluminum foil current collector in a spin coating manner, and vacuum baking at 120 ℃ for 12 hours to form a positive electrode active material layer; then hot rolling is carried out at 160 ℃ to combine the positive electrode active material layer with aluminum foil, and a positive electrode plate is obtained after cutting;

(2) The positive plate is matched with a silicon-oxygen-graphite negative electrode (buckling capacity is 500mAh/g, first effect is 83%) and 1mol/L LiPF is used ₆ The EC+DEC mixed solution (the volume ratio of EC to DEC is 1:1) is used as electrolyte, and the PP/PE/PP three-layer diaphragm is used as diaphragm to manufacture the soft package battery with the thickness of about 130mAh for testing the performance of the battery.

In order to strongly support the beneficial effects brought by the technical schemes of the embodiments 1-4, the following tests are provided:

lithium battery performance test: the batteries of each example were subjected to charge and discharge tests according to a 0.5C/0.5C charge and discharge regime, the test voltage range of the negative electrode sheet was 3.0-4.25V, the test voltage range of the positive electrode sheet was 3.0-4.4V, and the test results are shown in Table 1.

Table 1 results of performance tests of different lithium ion batteries

As can be seen from the test results in table 1, the lithium batteries in examples 1 to 3 of the present application have higher initial coulombic efficiency and higher capacity retention after 300 cycles than the lithium batteries in comparative examples 1 to 3, respectively, which indicates that the thin film prepared by the method provided by the present application can significantly improve the cycle performance of the battery. Specifically, as can be seen from comparative examples 3 and 3, the positive electrode sheet of comparative example 3 does not contain a lithium supplementing film, cannot be pre-supplemented with active lithium ions, exhibits low coulombic efficiency after active lithium ions are consumed by SEI (solid electrolyte membrane) formed during the first charge, and causes deterioration of cycle performance. FIG. 5 is a photograph comparison of the negative electrode sheet of the present application after the full power disassembly of example 2 (a) and comparative example 2 (b), and it can be seen from FIG. 5 and Table 1 that the lithium supplementing electrode film of comparative example 2, which is disposed on the aluminum foil current collector, although adding SLMP as a lithium supplementing agent in the same amount as example 2, has some position enrichment phenomenon due to uneven distribution of the lithium supplementing agent in the film, resulting in rupture of the lithium supplementing electrode film on the negative electrode sheet after 300 weeks of circulation, and local agglomeration of the lithium supplementing agent, resulting in local lithium precipitation of the negative electrode sheet, thereby leading to rapid degradation of the cycle performance of the battery; in contrast, the negative electrode sheet of example 2 of the present application had a complete film on the surface of the negative electrode sheet after 300 weeks of cycle, and no lithium dendrite formation occurred. In addition, as can be seen from comparison between example 1 and comparative example 1 in table 1, in the lithium-supplementing electrode film (comparative example 1) prepared by the conventional dry process, the random distribution of the lithium-supplementing agent in the film causes enrichment in certain positions, which can cause uneven lithium supplementing effect, and causes safety problems such as lithium precipitation and lithium dendrite growth, which greatly affect the cycle performance of the battery. And the random distribution of the lithium supplementing agent can also cause the problems of uneven current density on the surface of the electrode plate, overlarge local impedance and the like, thereby causing the temperature rise of the battery cell, aggravating polarization and the like.

In addition, in example 4, mg (OH) was introduced into the NCM811 positive electrode sheet as compared with comparative example 3 ₂ The flame retardant and the uniform distribution of dry particles including the flame retardant in the electrode film is realized by controlling the granularity concentration of the raw materials, introducing physical field intervention into batch high-pressure shearing mixing materials and the like. The flame retardant effects of the battery of example 4 and the battery of comparative example 3 are listed in table 2 below.

Table 2 comparison of flame retardant effects of the battery of example 4 and the battery of comparative example 3

As can be seen from table 2, the battery of example 4 of the present application has significantly reduced combustion rate compared to comparative example 3 by needling at different SOCs. This shows that the film containing flame retardant prepared by the method provided by the embodiment of the application can obviously improve the flame retardant property of the battery.

Claims

1. A film for a battery electrode, the film comprising a fibrillated network matrix of fibrillated binder interweaved with dry particles comprising particles of functional material and particles of conductive agent distributed on the fibrillated network matrix, a portion of the dry particles having a first size and the remaining dry particles having other sizes, the other sizes being less than 1/2 of the first size; the dry particles with the first size are orderly arranged in an array, the dry particles with the other sizes are filled in the particle gaps of the dry particles with the first size, and the particle gaps are smaller than the first size.

2. The film of claim 1, wherein the first dimension is in the range of 1 μm to 50 μm.

3. The film of claim 1, wherein the other dimensions comprise one or more different dimensions, the other dimensions being in the range of 30nm to 10 μm.

4. The film of claim 1, wherein the functional material particles comprise at least one of an active ion extender, a flame retardant, and an expansion-slowing agent.

5. The film of claim 1, wherein the functional material particles have a D50 particle size in the range of 30nm to 50 μm.

6. The film of claim 1, wherein the dry particles of each different material have a particle size distribution satisfying (D90 particle size-D10 particle size)/D50 particle size <1.5.

7. The film of claim 1, wherein the film has a thickness of greater than or equal to 30 μm.

8. The film of claim 7, wherein the film has a thickness of from 30 μm to 300 μm.

9. The film of any one of claims 1-8, wherein the functional material particles comprise 70% to 99% of the film by mass.

10. The film of any one of claims 1-8, wherein the dry particles further comprise electrode active material particles.

11. The film of claim 10, wherein the electrode active material particles have a D50 particle size in the range of 1 μm to 50 μm.

12. The film of claim 11, wherein the electrode active material particles have a particle size distribution satisfying (D90 particle size-D10 particle size)/D50 particle size <1.5.

13. The film of claim 10, wherein the mass of the electrode active material comprises 70-99% of the mass of the film.

14. The film of claim 10, wherein the functional material comprises 0.05% to 30% by mass of the film.

15. A method for preparing a film for a battery electrode, the method comprising:

high pressure shearing the first mixture with physical field intervention introduced to fibrillate the binder particles and arrange the dry particles having the first size in order, then adding the dry particles having the other size, and continuing high pressure shearing to obtain a second mixture; wherein the physical field intervention comprises at least one of an ultrasonic shock and a magnetic field intervention;

Pressing the second mixed material to obtain a film; wherein the film comprises a fibrillated network matrix of fibrillated binder interwoven with the dry particles distributed on the fibrillated network matrix; the dry particles having the other size are filled in the particle gaps of the dry particles having the first size, which are smaller than the first size.

16. An electrode sheet, characterized in that the electrode sheet comprises a current collector and the film according to any one of claims 1-9 arranged on the current collector.

17. The electrode sheet of claim 16, further comprising an electrode active material layer disposed between the current collector and the thin film.

18. An electrode sheet, characterized in that the electrode sheet comprises a current collector and the thin film according to any one of claims 10 to 14 provided on the current collector, the thin film serving as an electrode active material layer of the electrode sheet.

19. An electrochemical cell comprising a positive electrode, a negative electrode, and a separator and electrolyte between the positive electrode and the negative electrode, wherein the positive electrode and/or the negative electrode comprises the electrode sheet of any one of claims 16-17 or comprises the electrode sheet of claim 18.

20. A terminal comprising a housing, and a motherboard and a battery located inside the housing, the battery comprising the electrochemical cell of claim 19, the electrochemical cell being configured to power the terminal.