CN113937284A

CN113937284A - Thin film for battery electrode and preparation method thereof

Info

Publication number: CN113937284A
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: 2022-01-14
Anticipated expiration: 2040-07-14
Also published as: CN113937284B; WO2022012357A1

Abstract

The embodiment of the application provides a film for a battery electrode, which comprises a fibrillating network matrix formed by interweaving fibrillating binders and dry particles distributed on the fibrillating 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 1/2 smaller than the first size; the dry particles having the first size are arranged in an orderly manner, and the dry particles having the other sizes are filled in the inter-particle spaces of the dry particles having the first size, which are smaller than the first size. Because the dry particles are not randomly distributed in the film and are not easy to agglomerate, the continuity and the integrity of the film are high, and when the film is used for a battery electrode, the functional material can well exert the functional characteristics and improve the performance of the battery. The embodiment of the application also provides a preparation method of the film, an electrode plate, an electrochemical cell and a terminal.

Description

Thin 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 thin film for a cell electrode and a preparation method thereof, an electrode plate, an electrochemical cell and a terminal.

Background

With the development of economy and science and technology, industries such as portable electronic devices (mobile phones, tablet computers and notebook computers), unmanned planes and electric vehicles have urgent needs for energy storage devices with higher energy density, longer cycle life and higher safety. In order to meet the above requirements, the conventional measures adopted in the industry are to introduce appropriate functional materials (such as lithium supplement agent, flame retardant, etc.) into the lithium ion battery system. However, only a small amount of functional materials can be directly added into the electrolyte, and most of the functional materials need to be introduced through an electrode plate preparation technology with stronger compatibility so as to play a role in the battery. The traditional wet electrode plate preparation process for introducing the functional material is to mix the electrode active material, the functional material, a solvent and the like into slurry, and then coat and dry the slurry on a substrate to form a film, but the functional material with active chemical properties such as a lithium supplement agent (such as metallic lithium) is easy to explode in a humid environment and is not suitable for being introduced through the traditional wet electrode plate preparation process. The dry electrode film technology without solvent solves the problem that the functional material in the wet process is not compatible with the processing environment of solvent, and the like, and particularly, the technology applies high shearing force to dry binder particles to fibrillate the dry binder particles and load various functional material particles on the dry binder particles. However, in the conventional dry electrode film, the particles are randomly distributed due to the absence of the solvent, and are easily agglomerated, thereby affecting their performance of optimizing the battery performance, and even deteriorating the performance of the battery, such as energy density, cycle ability, safety, and the like.

Disclosure of Invention

In view of this, the embodiment of the present application provides a thin film prepared by a dry process, dry particles in the thin film do not agglomerate, the uniformity of the thin film is good, and when the thin film is used for a battery electrode, the dry particles can well exert corresponding characteristics, and the battery performance is improved.

Specifically, a first aspect of embodiments of the present application provides a film for a battery electrode, the film comprising a fibrillated network matrix interwoven with a fibrillated binder, and dry particles distributed on the fibrillated network matrix, the 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; the dry particles having the first size are arranged in an orderly manner, and the dry particles having the other sizes are filled in the inter-particle spaces 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 fibrillating network matrix formed by the fibrillating binder, but the dry particles with the largest relative particle size and the first size are orderly arranged, and the dry particles with the smaller relative particle size and other sizes are filled in the gaps among 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; the energy density, the cycle ability, the safety, etc. of the battery are not deteriorated.

In an embodiment of the present application, the first dimension is in a range of 1 μm to 50 μm; the other dimensions include one or more different sized particle sizes, and the other dimensions are in the range of 30nm to 7 μm. The appropriate size allows for a tighter distribution of dry particles, a greater loading of dry particles, and ensures a more stable structure of the film.

In an embodiment of the present application, the functional material particles include at least one of an active ion extender, a flame retardant, and a swelling retarder. Wherein, the active ion replenisher can effectively improve the energy density of the battery; the flame retardant can improve the flame retardant performance of the battery and improve the safety of the battery; and the expansion retardant can effectively relieve the expansion of the electrode material and improve the cycling 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 the present embodiment, the functional material particles have a D50 particle size 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 different specific functions and practical application scenes.

In the embodiment of the application, the particle size distribution of the dry particles made of different materials satisfies (D90 particle size-D10 particle size)/D50 particle size < 1.5. The dry particles made of different materials are high in size concentration ratio, so that the dry particles are uniformly and orderly distributed in a fibrillating network matrix, the quality of a film loaded with the dry particles can be improved, the corresponding characteristics of the dry particles can be exerted to the greatest extent, and the quality consistency and the function reproducibility of films in different batches are ensured.

In an embodiment of the present application, the thin film has a thickness of 30 μm or more. The thickness is greater than the film thickness produced by the existing wet process and is free of solvent residues. In one embodiment of the present application, the thin film has a thickness of 30 μm to 300. mu.m.

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

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

In the present embodiment, the D50 particle size of the electrode active material particles is in the range of 1-50 μm. The electrode active material particles with larger sizes 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 further 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 size concentration of the electrode active material particles is high, so that the electrode active material particles are uniformly and orderly distributed in the fibrillating network matrix, the quality of the film containing the electrode active material can be improved, the excellent performance is realized, and the quality consistency and the function reproducibility of films in different batches are ensured.

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

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

The second aspect of the embodiments of the present application also provides a method for preparing a thin film for a battery electrode, including:

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

under the condition of introducing physical field intervention, carrying out high-pressure shearing on the first mixture to fibrillate the binder particles and arrange the functional material particles with the first size in order, then adding the dry particles with 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 interwoven by the fibrillated binder and the dry particles distributed on the fibrillated network matrix; the dry particles having the first size are arrayed to form an ordered structure, and the dry particles having the other sizes are filled in the inter-particle spaces of the dry particles having the first size, which are smaller than the first size.

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

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

In the embodiment of the present application, the D50 particle size of the binder particles is 1 μm to 50 μm. The binder particles of larger particle size can facilitate the formation of a fibrillated network matrix with uniform interweaving, strong elasticity and sufficient viscosity.

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

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

In the present embodiment, in order to make the distribution of the different materials of various sizes in the film more uniform, the particle size distribution of the dry particles of each of the different materials 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 sizes are sequentially subjected to high-pressure shearing with the binder particles, the dry particles with the first size are tightly and orderly arranged through physical field intervention, and the dry particles with the other sizes and the smaller relative sizes are filled in the gaps among 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.

The third aspect of the embodiments of the present application further provides an electrode sheet, where the electrode sheet includes a current collector and a thin film as described in the first aspect of the embodiments of the present application, disposed on the current collector. The electrode sheet has a stable structure, contains a thin film with high flatness, high integrity and good continuity, and can be used for providing an electrochemical cell with improved electrochemical performance.

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

In 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 embodiments of the present application also provides an electrochemical cell comprising a positive electrode, a negative electrode, and a separator and an electrolyte between the positive electrode and the negative electrode, wherein the positive electrode and/or the negative electrode comprises the electrode sheet of the fourth aspect of the embodiments of the present application. The electrochemical cell has high energy density, long cycle life and high safety.

The fifth aspect of the embodiments of the present application further provides a terminal, where the terminal includes a housing, and a main board and a battery located inside the housing, where the battery includes the electrochemical cell according to the fourth aspect of the embodiments of the present application, and the electrochemical cell is used to supply power to the terminal. The terminal can be an electronic product such as a mobile phone, a notebook, a tablet personal computer, a portable machine, an intelligent wearable product and the like.

Drawings

FIG. 1a is a schematic plan view of a film provided in accordance with an embodiment of the present disclosure;

FIG. 1b is a schematic illustration of a three-dimensional distribution of dry particles in a film provided in an embodiment of the present application;

fig. 2 is a schematic structural diagram of an electrode sheet provided in an embodiment of the present application;

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

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

fig. 5 is a photograph comparison of the negative electrodes of the batteries in example 2(a) and comparative example 2(b) of the present application after full disassembly.

Detailed Description

The following description will be made with reference to the drawings in the embodiments of the present application.

Referring to fig. 1a and 1b together, the present embodiment 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 include particles of the functional material and particles of the conductive agent, a part of the dry particles having a first size, the rest of the 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 an orderly manner, the dry particles 21 having the first size have particle gaps smaller than the first size, and the dry particles 22 having other sizes are filled in the particle gaps of the dry particles 21 having the first size.

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

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

In the present embodiment, in the three-dimensional structured film 100 (see fig. 1b), each of the dry particles having the first size is surrounded by 6 to 12 dry particles having the first size. In this way, the dry particles 21 having the first size are arranged in a compact manner, which helps to increase the distribution density of the dry particles in the film 100, and when the film 100 is used in a battery, the electrochemical performance such as energy density of the battery can be improved.

In embodiments of the present invention, the film 100 has a porosity of less than 30%. In some embodiments, the porosity of film 100 may be less than 20%, less than 10%, even less than 5%, or less than 1%. The smaller porosity represents that the mutual filling degree between any adjacent dry particles 2 in the film 100 is high, the degree of compactness is large, each dry particle in the film 100 is more stably and orderly arranged, and the film has stable structure and better mechanical property.

The term "dry particles" in the present application is intended to encompass within its scope powders, spheres, flakes, fibers, tubes and other particles of any shape and aspect ratio. Wherein, for spherical or spheroidal particles/powders, the first dimension refers to the D50 particle diameter, and for non-spherical particles such as flakes, fibers, tubes, rods, etc., the first dimension refers to the length and width dimensions.

In the present embodiment, the size of the dry particles 2 may be in the range of 30nm to 50 μm. Wherein the first size may be in a range of 1 μm to 50 μm; other sizes may be in the range of 30nm-10 μm. In some embodiments, the first dimension may be in a range of 2 μm-30 μm, 5 μm-50 μm, 8 μm-20 μm, or 3 μm-15 μm. The other size may be in the range of 30nm to 7 μm, 30nm to 1 μm, 30nm to 500nm, or 50nm to 200nm, as long as "1/2 having the other size smaller than the first size" is satisfied, which may facilitate the dry particles having the other size to be filled in the spaces between the closely arranged dry particles having the first size. In some embodiments of the present application, the first dimension may be in the range of 3 μm to 15 μm, and the other dimension may be in the range of 30nm to 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 dry particles having a second size, dry particles having a third size different from the second size, and 1/2 where the second size and the third size are both smaller than the first size, in addition to the dry particles having the first size, both of which may be packed in a close, ordered arrangement of the interstices between the dry particles having the first size.

In the present application, the dry particles having the same size may be the same or different. Specifically, the functional material particles (for example, lithium supplement particles) having two different materials may have the first size, or the lithium supplement particles having two different materials and the electrode active material particles having different functions may have the first size.

In the present embodiment, the fibrillated network matrix 1 may be used to capture, bind, and support the dry particles 2. Specifically, the dry particles 2 are captured by the entangled fibrillated network matrix 1, and the fibrillated network matrix 1 also supports the dry particles 2, and the dry particles 2 can be bonded together by a fibrillated adhesive.

In the present embodiment, the material of the fibrillating network matrix 1 may be a chain type polymer binder. The chain type high molecular binder can be convenient for forming a fibrillating network matrix under the action of high shearing force. Specifically, the material of the chain type polymer binder may include one or more of cellulose and its derivatives, polyolefin, fluoropolymer, 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, examples of the fluoropolymer include Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF2), polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP), and examples of the polyolefin include polypropylene (PP) and Polyethylene (PE). Examples of the cellulose and its derivatives include carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), and the like. In the present embodiment, the D50 particle size of the binder particles for forming the fibrillated network matrix 1 may be in the range of 1 μm to 50 μm, and further, may be in the range of 2 μm to 20 μm or 3 μm to 15 μm. The larger size binder particles facilitate the formation of a fibrillated network matrix 1 with uniform interlacing, high elasticity, and sufficient viscosity.

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 can comprise one or more of active ion replenisher, flame retardant and swelling reducing agent. After the film is assembled into a battery subsequently, the film can play corresponding functions in different stages according to different characteristics of functional materials contained in the film. Specifically, the functional material of the flame retardant does not participate in the electrochemical process of the battery, and if the battery is heated or burns, the flame retardant can absorb heat, cover, inhibit chain reaction and the like to prevent the combustion process and flame propagation, so that the safety of the battery is improved. The functional material of the expansion retarder can provide a buffer effect and relieve the expansion of the electrode plate in the expansion process of the electrode material, so that the cycle stability and the safety performance of the battery are improved. The active ion replenisher can irreversibly release a large amount of active lithium ions in the first charge-discharge process of the battery so as to supplement the active ions and lithium and improve the energy density of the battery. Wherein the active ions may include one of lithium ions, sodium ions, potassium ions, magnesium ions, and aluminum ions.

Specifically, the active ion supplement comprises one of a lithium supplement agent, a sodium supplement agent, a potassium supplement agent, a magnesium supplement agent, a zinc supplement agent and an aluminum supplement agent. The lithium supplement agent can release a large amount of active lithium ions before an electrode active material of the battery in the formation stage of the lithium battery so as to supplement lithium. Lithium replenishers include, but are not limited to, lithium metal and its finished products, e.g., may include lithiumAt least one of powder, stabilized lithium powder, lithium ribbon, lithium foil, lithium-rich metal oxide, lithium-carbon composite, lithium-carbon alloy, lithium-silicon alloy, and the like. Li is cited as an example of the lithium-rich metal oxide₂NiO₂、Li₆CoO₄、Li₅FeO₄、Li₂O.MO (M is one or more of Fe, Co, Ni, Mn, Cu, Zn, Re, Al, Ti, Zr, W and La), etc. The residues of different lithium-supplementing agents after release of active lithium differ, for example with Li₂NiO₂The thin film as the positive electrode lithium-supplementing agent generates LiNiO, NiO and Li after the formation of the battery is finished₂One or more of O; with Li₆CoO₄The thin film used as the positive electrode lithium supplement agent generates LixCoO after the formation of the battery is finished₄(0＜x＜6)、CoO₂、Li₂One or more of O; with Li₅FeO₄The thin film used as the positive electrode lithium supplement agent can generate LiyFeO after the formation of the battery is finished₄(0＜y＜5)、Fe₂O₃、Li₂One or more of O.

In the embodiment of the present application, the flame retardant includes an inorganic flame retardant and an organic flame retardant. Among them, the inorganic flame retardant may include compounds of tellurium, aluminum hydroxylates (such as aluminum hydroxide, bis (2-ethylhexanoic acid) aluminum hydroxide), magnesium hydroxide, borates, and the like; the organic flame retardant may include triazine and its derivatives, melamine, polyphosphate, urea, dicyandiamide, and the like. Wherein the swelling reducing agent includes, but is not limited to, at least one of glucose, phenolic resin, sodium carboxymethylcellulose, gelatin, starch, graphene, polythiophene, carbon nanotube, polyacrylonitrile, trialkylaluminum, and the like.

In the embodiment of the application, the D50 particle size of each functional material particle made of different materials is in the range of 30nm-50 μm. Further, the D50 particle size of the functional material particle may be 30nm-1 μm, 50nm-200nm, 2 μm-50 μm, 5 μm-50 μm, 8 μm-20 μm, or 3 μm-15 μm. The sizes of the functional material particles of different materials can be flexibly adjusted according to different specific functions and practical application scenarios, and the functional material can be the dry particle 21 with the first size as the largest relative size, or the dry particle 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 a first size.

In the embodiment of the present application, the particle size distribution of the dry particles of each different material can satisfy (D90-D10)/D50<1.5, and especially, the particle size distribution of the functional material particles of each different material should satisfy (D90-D10)/D50< 1.5. That is, the particle size distribution of the active ion replenisher particles, the flame retardant particles, and the expansion reducing agent particles, which are different for each material, satisfies (D90 particle size-D10 particle size)/D50 particle size < 1.5. The size concentration of the dry particles of each different functional material is higher, so that the dry particles of the same material can be uniformly and orderly distributed in the fibrillating network matrix, the quality of the film loaded with the dry particles can be improved, the excellent performance can be fully exerted in the battery electrode subsequently, and the quality consistency and the function reproducibility of films in different batches can be ensured.

In the embodiments of the present application, the kind of the conductive agent is not particularly limited, and any conventional material in the art may be used. For example, the conductive agent may include one or more of carbon fibers, carbon nanotubes, graphite, graphene, conductive carbon black, furnace black, mesocarbon microbeads, and the like. The conductive carbon black may specifically include acetylene black, ketjen black, super 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 the present embodiment, the size of the conductive agent is in the range of 30nm to 50 μm. For zero-dimensional and three-dimensional conductive agents (such as conductive carbon black particles, furnace black particles, mesocarbon microbeads and the like), the D50 particle size can be less than or equal to 100 nm; for a two-dimensional layered conductive agent (e.g., flake graphite, graphene, etc.), the dimensions thereof refer to the length and width dimensions in the lateral direction, and specifically, the length and width dimensions of 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 each spherical or spheroidal conductive agent particle of different materials satisfies (D90 particle size-D10 particle size)/D50 particle size <1.5, thus the size concentration of each spherical or spheroidal conductive agent particle of different materials is higher, and the film 100 of the present application is endowed with uniform conductivity.

In the embodiment of the present application, the thickness of the film 100 may be made thicker or thinner according to a specific application scenario. Specifically, the thickness of the film 100 may be greater than or equal to 30 μm. For example, the thickness of the film may be 40 μm to 60 μm, 100 μm to 250 μm, or 30 μm to 300 μm. In some embodiments of the present application, the 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 because the film is produced by a solvent-free dry technique, the film 100 is cleaner and free or substantially free of any liquids (e.g., solvents) and residues resulting therefrom. The thickness of the film 100 is not limited by the consistency of the slurry and the coating method in the wet process technology, and the film can be thicker, continuous, high in integrity and firmer in structure. In addition, compared with the existing dry electrode film, the dry particles in the film are distributed more uniformly, the continuity and the integrity of the film are high, the structure is firmer, and the film has better mechanical property and electrical property.

In some embodiments of the present disclosure, 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, which is a functional layer of the electrode sheet, contains only the above functional material particles and the conductive agent particles in the dry particles. In this embodiment, the mass of the functional material may be 70% to 99% of the total mass of the film 100. The mass ratio can ensure that the loading capacity of the functional material in the film is larger and the local aggregation phenomenon can not be generated under the condition of ensuring that the film has a stable structure and expected good mechanical properties, so that the performance of the battery can be improved to the maximum extent.

In other embodiments of the present disclosure, the dry particles in film 100 further comprise electrode active material particles. At this time, the film 100 of the present application may be directly disposed on the surface of the current collector, serving as an active material layer of the electrode sheet, and constitute an electrode sheet of the battery together with the current collector. In this embodiment, the mass of the electrode active material may be 70 to 99% of the total mass of the film 100. The mass of the functional material can account for 0.05-30% of the total mass of the film 100. These mass fractions enable uniform distribution of the dry particles in the film while ensuring the maximum loading of the electrode active material, thereby enabling the battery made from the film to have both high specific capacity and good additional functions brought by the functional material.

In the present embodiment, the D50 particle size 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 large-particle-size components (i.e., dry particles having a first size) among the dry particles to achieve a close, orderly arrangement thereof in the thin film, to increase the loading amount thereof in the thin film, and to thereby increase the energy density of the battery employing the thin film. In some embodiments of the present 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 each electrode active material particle of different materials also meets (D90 particle size-D10 particle size)/D50 particle size <1.5, so that the uniform distribution of the electrode active material particles in the film is realized, the agglomeration is avoided, the quality of the film containing the electrode active material is improved, the excellent performance is realized, and the quality consistency and the function reproducibility of films of different batches are ensured.

According to the film provided by the embodiment of the application, the dry particles are not randomly distributed on the fibrillating network matrix formed by the fibrillating binder, but the dry particles with the largest relative size and the first size are orderly arranged, the particle gaps of the dry particles 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, so that the dry particles form stable and ordered arrangement, the film is good in continuity and high in integrity, does not contain solvent residues, is not easy to agglomerate in the film, is high in stability, can fully exert respective effects, and can better improve the performance of a battery when being 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 are 1/2 with a first size, and the rest of the dry particles are 1/2 with other sizes smaller than the first size; formulating fibrillatable binder particles and dry particles having a first size into a first mixture 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 the binder particles, orderly arranging the dry particles with the first size, adding the dry particles with other sizes, and continuously 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 interwoven by a fibrillated binder and dry particles distributed on the fibrillated network matrix; the dry particles having the other sizes are filled in the particle spaces 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 size of the binder particle may be in the range of 1 μm to 50 μm, and further, may be in the range of 2 μm to 20 μm or 3 μm to 15 μm. The binder particles of larger particle size can facilitate the formation of a fibrillated network matrix with uniform interweaving, strong elasticity and sufficient viscosity.

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 first subjected to high-pressure shearing with the binder particles as a large-particle-diameter component.

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

In step S102 in the embodiment of the present application, if the dry particles with other sizes include a plurality of different sizes, the dry particles may be 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 D50 particle size of the spherical or spheroidal particles of different materials, the particles are added in batches from large to small. Therefore, the dry particles with the first size and the dry particles with other sizes can be closely and orderly arranged, and the uniform arrangement property of the dry particles in the film is better improved.

In step S102, the physical field intervention includes at least one of ultrasound oscillation and magnetic field intervention. Physical field intervention helps to align the dry particles having the first size. Taking ultrasonic oscillation as an example, the ultrasonic oscillation device can push large-particle-size components to reciprocate in a high-frequency manner to form a highly uniform ordered arrangement state, so that the later added small-particle-size components can be filled in particle gaps of the large-particle-size components. It should be noted that the magnetic field intervention is applied to the formation of an ordered arrangement of the dry particles having magnetism, 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 the magnetic particles and the film without the magnetic particles. Further, when the above-mentioned thin film containing magnetic particles is prepared, the physical field intervention to be employed may include at least one of ultrasonic oscillation 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 present 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 be initiated only when high pressure shearing is performed at step S102. At this time, the physical field may be applied to the outer wall of the high pressure shearing apparatus. In other embodiments of the present application, the introduction of the physical field intervention may begin as soon as the first mixture is formulated at step S101. At this time, a physical field may be applied to the outer walls of 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 first mixture in step S101 may be prepared by ordinary mechanical mixing (e.g., stirring, milling, dual motion mixing, etc.) without introducing high pressure gas, or by high pressure shear mixing with introducing high pressure gas flow. Specifically, the mixing device for forming the first mixture may include at least one of a belt mixer, a rotary mixer, a planetary mixer, an acoustic mixer, a microwave mixer, a double motion mixer, a fluidized bed mixer, a ball mill, a high speed shear mixer, a jet mill, a hammer mill, and the like. Wherein, when the first mixture is formed by high-pressure shear mixing (such as high-speed shear mixer, jet mill, hammer mill, etc.), the first mixture can be prepared and the high-pressure shear can be performed by a single device.

In step S101 of the embodiment of the present application, the protective gas used in preparing the first mixture is a sufficiently dry gas including at least one of dry air, nitrogen, helium, hydrogen, and the like, and is preferably a dry compressed gas provided under high pressure. The protective gas can prevent the property/function change of some material particles with more active chemical properties and improve the safety. In some embodiments of the present application, the shielding gas is still present during the high pressure shearing process of step S102. The presence 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 fibrillating of the binder particles is achieved by a dry, solvent-free, liquid-free high-pressure shear force technique, which may be specifically achieved by applying a positive pressure or a negative pressure, such as a compressed gas or a vacuum. In the fibrillation process, high shearing force is applied to the binder, so that the binder can be physically elongated and fibrillated, and the elongated binder is mutually wound and overlapped to form a thin reticular fibrillated network matrix. In one embodiment of the present application, the high pressure air stream used during high pressure shearing has a pressure greater than or equal to 60PSI in order to achieve sufficient fibrillation of the binder particles. Specifically, the PSI value may be 60PSI-500PSI or 80PSI-300 PSI.

In the present embodiment, the apparatus for fibrillating the binder may include a jet mill, a pin mill, a hammer mill, a collision crusher, and the like. In one embodiment, the fibrillation of the binder particles is achieved by a jet mill. The jet mill is provided with at least one nozzle capable of spraying high-pressure air flow besides a common mechanical shearing fly-cutter. During the preparation of the first mixture, the chain type high molecular binder is gradually agglomerated into blocks, the size of the agglomerates/aggregates formed in the mixing process can be reduced to form small particles by a common mechanical shearing fly cutter, the collision of the small particles can be accelerated by high-pressure air flow sprayed from a nozzle of a jet mill, the binder is elongated and fibrillated, the elongated binder is mutually wound and overlapped until the elongated binder is 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 second mixed material may be pressed by rolling, calendering, and the like, and specifically, the second mixed material may be pressed by a roll press, a roll grinder, a calender, a belt press, a platen press, and the like.

According to the preparation method of the film provided by the embodiment of the application, under the intervention of a physical field, the large-particle-size component (dry particles with the first size) and the binder particles are firstly subjected to high-pressure shearing, so that the large-particle-size component is closely and orderly arranged, the small-particle-size component (dry particles with other sizes) is added to continuously carry out high-pressure shearing, and the small-particle-size component is filled in the particle gaps of the large-particle-size component, so that the dry particles are not agglomerated, the film with good continuity, high integrity and good stability is obtained, and the effect of the dry particles can be fully exerted when the film is used for a battery electrode, 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 3 wt% of a 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 preparation method does not involve the use of solvents, liquids and processing aids in the whole process, solves the problem that the functional materials with active chemical properties in the electrode film field are incompatible with wet processes such as solvents and the like, has strong universality, and is suitable for introducing materials with various properties into a film; compared with a wet process, the preparation method has the advantages that the cost is low, the cost can be saved by 3-4%, the thickness of the obtained film can be thicker, the continuity and the stability of the film are still good when the film is thicker, and the integrity is higher. The process is simple, low in cost, efficient and environment-friendly, and can be used for large-scale production.

Referring to fig. 2, an electrode sheet 2000 is provided in an embodiment of the present application, 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 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 an active ion extender, a flame retardant, and a swell reducer. 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 loading capacity of the functional material in the film is larger and the local aggregation phenomenon can not be generated under the condition of ensuring that the film has a stable structure and expected good mechanical properties, so that the performance of the battery can be improved to the maximum extent.

In addition, in this embodiment, the porosity of the film 100 may be less than 30%. At this time, the dry particles in the film 100 are arranged more densely, the mechanical strength of the film 100 is higher, 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 the present embodiment, the current collector 10 includes, but is not limited to, a metal foil or an alloy foil, the metal foil includes a copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold or silver foil, and the alloy foil includes stainless steel or an alloy containing at least one element of copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold and silver. Optionally, the alloy foil comprises 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 for making effective contact with the electrode active material layer 11.

In the present embodiment, the electrode active material layer 11 may be prepared on the current collector 10 by a coating method or a roll-pressing method, and the film 100 may be combined with the electrode active material layer 11 by a roll-pressing, isostatic pressing, or the like. The 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. Specifically, the electrode active material includes, but is not limited to, metals, inorganic non-metals (such as carbon materials), oxides, nitrides, carbides, borides, sulfides, chlorides, or composites of various energy storage materials. Examples of the inorganic compound include lithium, magnesium, potassium, magnesium, sulfur, phosphorus, silicon, lithium cobaltate, lithium iron phosphate, layered gradient compound, and Li₃PO₃、TiO₂、Li₄Ti₅O₁₂、SiO、SnO₂、NiS、CuS、FeS、MnS、Ag₂S、TiS₂And the like. 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 active material may be specifically lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, phosphorusLithium cobalt oxide, lithium cobaltate (LiCoO)₂) At least one of lithium manganate, lithium manganese nickelate, lithium nickel manganese, Nickel Cobalt Manganese (NCM), Nickel Cobalt Aluminum (NCA), and the like. The negative 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)₄Ti₅O₁₂) And TiO₂And the like. 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 may be any conventional materials in the art, 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 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 an 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 present embodiment also 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, in this embodiment, dry particles in the thin film 100 include electrode active material particles, the above functional material particles, and conductive agent particles at the same time, 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 performance of the battery in various aspects, such as energy density, cycle performance, and safety performance.

In this embodiment, the film 100 has a void fraction of less than 30%. At this time, the arrangement of the dry particles in the film 100 is dense, which is particularly helpful to increase the distribution density of electrode active material particles with larger particle size in the film 100, and to increase the specific capacity of the 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 again. The film 100 may be disposed 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 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 used as 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 to 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 that all dry particles in the film can be uniformly distributed under the condition of ensuring the maximum load capacity of the electrode active material, so that the battery made of the film has high specific capacity and good additional functions brought by functional materials.

The embodiment of the application also provides an electrochemical battery, 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 plate.

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, the secondary battery having high cycle performance and high safety.

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

The examples of the present application are further illustrated below in various examples.

Example 1

This example provides a positive electrode active material with nickel-cobalt-manganese NCM811, Li₂NiO₂The preparation method of the lithium supplement electrode film of the lithium supplement agent, the Carbon Nano Tube (CNTs) conductive agent and the PVDF binder and the soft package battery assembled by the film comprises the following steps:

(1) preparing a positive electrode lithium supplement electrode film:

preparing raw materials: taking a positive electrode active material NCM811 with D50 of 12 mu m, removing ultra-large particles and fine particles in the NCM811 by a cyclone classification technology, and adjusting the volume distribution and the quantity distribution (D90-D10)/D50 of the particle size to be 1.35; taking a lithium supplement Li with the D50 particle size of 5 mu m₂NiO₂The particles were mixed with PVDF particles as a binder having a particle size of 5 μm of D50, in which Li₂NiO₂The volume distribution and the quantity distribution of the particle sizes of the particles and the PVDF particles both meet (D90-D10)/D50<1.5；

Mixing the NCM811 particles and Li₂NiO₂Particles, PVDF particles and CNTs were measured according to 88: 5: 5: 2, weighing, adding the weighed NCM811 particles and PVDF into a mixing tank of a jet mill under the protection of argon, and starting an ultrasonic generator and a magnetic field to enable the ultrasonic frequency in the mixing tank to be 40kHz, the power to be 40W and the magnetic field strength to be 0.3T; mixing materials for 10min with common mechanical fly cutter, opening high pressure air valve of jet mill, introducing 60PSI high pressure air flow to perform high pressure shearing (ultrasonic generator and magnetic field are still opened during high pressure shearing) on the materials in the mixing tank to fibrillate PVDF particles and adhere all the particles, high pressure shearing for 30min, and adding weighed Li₂NiO₂The particles and CNTs are continuously subjected to high-pressure shearing for 2.5h, PVDF is repeatedly fibrillated, newly added materials are adhered, and finally the obtained mixed materials are ground by sprayingA rolling device connected with the discharge port of the mill rolls the mixture into a film with the thickness of 150 mu m;

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

(3) preparing a lithium ion battery: the anode plate is matched with a silica graphite cathode (the fastening capacitance is 500mAh/g, the first effect is 83 percent), and 1mol/L LiPF is used₆The EC + DEC mixed solution (the volume ratio of EC and DEC is 1:1) is used as electrolyte, a PP/PE/PP three-layer diaphragm is used as a diaphragm, and the soft package battery with the thickness of about 130mAh is manufactured and used for testing the performance of the battery.

In this example 1, the compounding process for preparing the lithium ion-supplement electrode film is protected by argon gas, and the lithium ion-supplement agent Li with active chemical properties is used₂NiO₂Does not denature and inactivate, and leads each dry particle not to be randomly distributed on a fibrillating network matrix formed by fibrillating the binder by introducing physical field (ultrasonic field and magnetic field) interference during high-pressure shearing, so that the lithium supplement agent Li₂NiO₂Can exert better lithium supplementing effect. In addition, no solvent is introduced in the preparation of the lithium-supplement electrode film, so that Li is avoided₂NiO₂The problems of difficult gel and coating in the pulping and homogenate process and the like, is environment-friendly and saves the cost.

Example 2

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

(1) preparing a negative electrode lithium supplement electrode film:

preparing raw materials: firstly, controlling the concentration ratio of the particle diameter of each material by using an electrostatic classification technology for raw materials such as silicon-oxygen mixed graphite cathode active material particles (the particle diameter of D50 is 6 microns), SLMP particles (the particle diameter of D50 is 15 microns), PTFE particles (the particle diameter of D50 is 8 microns) and acetylene black particles (the particle diameter of D50 is 50nm) and the like, and ensuring that the volume distribution and the quantity distribution of the particle diameter of each material meet (D90-D10)/D50< 1.5;

mixing the graded silica mixed graphite negative electrode active material particles with SLMP particles, PTFE particles, and acetylene black particles in a ratio 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 enable the ultrasonic frequency in the mixing tank to be 40kHz and the power to be 40W; after mixing materials for 10min by using a common mechanical fly cutter, opening a high-pressure air valve of a jet mill, carrying out high-pressure shearing on the materials in a mixing tank for 2.5h by introducing 60PSI high-pressure air flow, then adding weighed silica mixed graphite cathode active material particles, continuing carrying out high-pressure shearing for 2.5h (an ultrasonic generator is still started during high-pressure shearing), adding acetylene black particles, continuing carrying out high-pressure shearing for 30min to obtain a fibrillated mixed material, and finally rolling the obtained mixed material into a film with the thickness of 100 mu m by using rolling equipment 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, carrying out hot rolling on the film at 160 ℃ to enable the film to be combined with a copper foil, and cutting the sheet to form a negative plate;

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

the negative plate is matched with an NCM811 positive plate, and 1mol/L LiPF is adopted₆The EC + DEC mixed solution (the volume ratio of EC and DEC is 1:1) is used as electrolyte, a PP/PE/PP three-layer diaphragm is used as a diaphragm, and the soft package battery with the thickness of about 130mAh is manufactured and used for testing the performance of the battery.

Example 3

This example provides a method of using Li₆CoO₄The preparation method comprises the following steps of:

(1) preparing a lithium supplement film:

preparing raw materials: mixing Li₆CoO₄The concentration ratio of each material particle diameter is controlled by electrostatic classification technology through particles (D50 particle diameter is 15 μm), PTFE particles (D50 particle diameter is 10 μm) and Ketjen black particles (D50 particle diameter is 80nm), and the volume distribution and the quantity distribution of each material particle diameter are ensured to meet (D90-D10)/D50<1.5；

Classifying the above-mentioned Li₆CoO₄Weighing the particles, PTFE particles and Ketjen black particles according to the ratio of 7:2:1, and under the protection of argon, weighing the Li₆CoO₄Adding 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 intensity is 0.3T; after mixing materials for 10min by using a common mechanical fly cutter, opening a high-pressure air valve of a jet mill, carrying out high-pressure shearing on the materials in a mixing tank for 40min by introducing 60PSI high-pressure airflow, then adding weighed Ketjen black particles, continuing carrying out high-pressure shearing for 20min to obtain a fibrillated mixed material, finally pressing the obtained mixed material into a film with the thickness of 30 mu m, and putting the film into a sealing bag for storage for later use;

(2) preparing 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 baking for 12 hours at 120 ℃ in vacuum to form a positive electrode active material layer;

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

(3) preparing a lithium ion battery: the positive plate is matched with a common silica material negative electrode for use1mol/L LiPF₆The EC + DEC mixed solution (the volume ratio of EC and DEC is 1:1) is used as electrolyte, a PP/PE/PP three-layer diaphragm is used as a diaphragm, and the soft package battery with the thickness of about 130mAh is manufactured and used for testing the performance of the battery.

Fig. 2 may represent the structure of the positive electrode sheet according to embodiment 3 of the present invention, and fig. 1a and 1b may represent the schematic structural diagram of the lithium supplement film 100 on the positive electrode sheet according to 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 supplement agent Li₆CoO₄And 22 is Ketjen black.

Example 4

This example provides a positive electrode active material comprising nickel-cobalt-manganese NCM811, Mg (OH)₂The preparation method 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 comprises the following steps:

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

preparing raw materials: taking a positive electrode active material NCM811 with D50 of 12 mu m, removing ultra-large particles and fine particles in the NCM811 by a jet flow classification technology, and adjusting the volume distribution and the quantity distribution (D90-D10)/D50 of the particle size to 1.1; and adding Mg (OH)₂The volume distribution and the number distribution of the particle sizes of the particles (D50 with the particle size of 100nm) and the PTFE particles (D50 with the particle size of 5 mu m) also meet the requirements of (D90-D10)/D50<1.5；

Mixing the NCM811 particles, Mg (OH)₂Particles, PTFE particles and CNTs were mixed according to 88: 5: 5: 2, adding the weighed NCM811 particles and PVDF into a mixing tank of a jet mill under the protection of argon, 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 a mechanical fly cutter to mix materials, opening a high-pressure air valve of a jet mill after 10min, introducing 60PSI high-pressure air flow to carry out high-pressure shearing on the materials in a mixing tank (an ultrasonic generator and a magnetic field are still opened during high-pressure shearing), adding weighed Mg (OH) after 30min of high-pressure shearing₂Continuously carrying out high-pressure shearing on the particles and the CNTs for 2.5h, and finally rolling the obtained mixed material through a roller connected with a discharge port of a jet millRolling the mixture into a film with the thickness of 150 mu m by using a device;

(3) preparing a lithium ion battery: the positive plate is matched with a silica graphite negative electrode (the buckling capacity is 500mAh/g, the first effect is 83 percent), and 1mol/L LiPF is used₆The EC + DEC mixed solution (the volume ratio of EC and DEC is 1:1) is used as electrolyte, a PP/PE/PP three-layer diaphragm is used as a diaphragm, and the soft package battery with the thickness of about 130mAh is manufactured and used for testing the performance of the battery.

In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided:

comparative example 1

Comparative example 1 provides a method for preparing a cathode active material containing NCM811 and Li by using a conventional dry process₂NiO₂The method for supplementing the lithium electrode film with the lithium supplementing agent, the CNTs conductive agent and the PVDF binder and the soft package battery assembled by the film. Comparative example 1 differs from example 1 in that: in the step (1), the particle size concentration ratio of each raw material is not controlled; and weighed NCM811 particles and Li are directly mixed₂NiO₂Adding the particles, PVDF particles and CNTs into a mixing tank of a jet mill, mixing for 10min by using a common mechanical fly cutter, opening a high-pressure air valve of the jet mill, selecting high-pressure air flow of 60PSI to carry out high-pressure shearing on the materials in the mixing tank for 3h, and rolling the mixed materials subjected to high-pressure shearing into a film with the thickness of 150 microns by using a rolling device connected with a discharge port of the jet mill.

Comparative example 2

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

Comparative example 3

Comparative example 3 provides a method for preparing a conventional NCM811 positive plate by using a conventional wet coating process, and also provides a pouch battery assembled from the conventional positive plate, which specifically includes the following steps:

(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 baking for 12 hours at 120 ℃ in vacuum to form a positive electrode active material layer; then carrying out hot rolling at 160 ℃ to combine the positive active material layer with the aluminum foil, and cutting into pieces to obtain a positive plate;

(2) the anode plate is matched with a silica graphite cathode (the fastening capacitance is 500mAh/g, the first effect is 83 percent), and 1mol/L LiPF is used₆The EC + DEC mixed solution (the volume ratio of EC and DEC is 1:1) is used as electrolyte, a PP/PE/PP three-layer diaphragm is used as a diaphragm, and the soft package battery with the thickness of about 130mAh is manufactured and used for testing the performance of the battery.

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

testing the performance of the lithium battery: the batteries of the examples were subjected to charge and discharge tests according to a 0.5C/0.5C charge and discharge schedule, with the test voltage range of the negative electrode tab being 3.0-4.25V and the test voltage range of the positive electrode tab being 3.0-4.4V, and the test results are shown in Table 1.

TABLE 1 Performance test results for different lithium ion batteries

As can be seen from the test results in table 1, the first coulombic efficiency and the capacity retention rate after 300 cycles of the lithium batteries in examples 1 to 3 of the present application are respectively higher than those of the corresponding lithium batteries in comparative examples 1 to 3, which indicates that the cycle performance of the batteries can be significantly improved by using the thin film prepared by the method provided in the examples of the present application. Specifically, comparative example 3 and comparative example 3 revealed that the positive electrode sheet of comparative example 3 did not include a lithium supplement film and could not pre-supplement active lithium ions, and that SEI (solid electrolyte membrane) formed during the first charge process consumed active lithium ions, thereby exhibiting lower coulombic efficiency and causing deterioration of cycle performance. Fig. 5 is a photo comparison of the negative electrode sheets in the present application example 2(a) and the comparative example 2(b) after full-charge disassembly, and as can be seen from fig. 5 and table 1, although the lithium supplement electrode film in the comparative example 2 disposed on the aluminum foil current collector has the same amount of SLMP as that in the example 2 added as the lithium supplement agent, because the lithium supplement agent is unevenly distributed in the film, some position enrichment phenomena occur, so that after the negative electrode sheet is cycled for 300 weeks, the lithium supplement electrode film on the negative electrode sheet is broken, and the lithium supplement agent is locally agglomerated, so that the negative electrode sheet has local lithium precipitation, and the cycle performance of the battery is rapidly attenuated; after the negative plate in example 2 of the present application is cycled for 300 weeks, the film on the surface of the negative plate is complete and no lithium dendrites are generated. In addition, as can be seen from comparison between example 1 and comparative example 1 in table 1, in the lithium supplement electrode film (comparative example 1) prepared by the conventional dry process, the lithium supplement agent is randomly distributed in the film, so that the lithium supplement agent is easily enriched at certain positions, the lithium supplement effect is not uniform, lithium cannot be supplemented at one part of the film, the lithium content is excessive at the other part of the film, and further safety problems such as lithium precipitation, lithium dendrite growth and the like are caused, and the cycle performance of the battery is greatly influenced. And the random distribution of the lithium supplement agent can 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 a battery cell, aggravating polarization and the like.

In addition, in example 4, compared with comparative example 3, Mg (OH) was introduced into the NCM811 positive electrode sheet₂The flame retardant is used for realizing the uniform distribution of dry particles including the flame retardant in the electrode film by controlling the particle size concentration of each raw material, introducing batch high-pressure shearing mixed materials of physical field intervention and the like. The flame retardant effects of the battery of example 4 and the battery of comparative example 3 are shown 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 combustion rate of example 4 of the present application was significantly decreased compared to comparative example 3 when needling was performed at different SOCs. This shows that the flame retardant-containing film prepared by the method provided by the embodiment of the application can significantly improve the flame retardant performance of the battery.

Claims

1. A film for a battery electrode, said film comprising a fibrillated network matrix interwoven with a fibrillated binder, and dry particles distributed over said fibrillated network matrix, said dry particles comprising particles of a functional material and particles of a conductive agent, some of said dry particles having a first size and others of said dry particles having other sizes, said other sizes being less than 1/2 of said first size; the dry particles having the first size are arranged in an orderly manner, and the dry particles having the other sizes are filled in the inter-particle spaces of the dry particles having the first size, which are smaller than the first size.

2. The film of claim 1, wherein the first dimension is in a range of 1 μ ι η to 50 μ ι η.

3. The film of claim 1, wherein the other dimensions include one or more different dimensions, and wherein the other dimensions are in the range of 30nm to 10 μ ι η.

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

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

6. A film according to any one of claims 1 to 5, wherein the dry particles of each different material have a particle size distribution such that (D90 particle size-D10 particle size)/D50 particle size < 1.5.

7. The film of any one of claims 1-6, 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. A film according to any of claims 1 to 8, wherein the particles of functional material comprise from 70% to 99% by mass of the film.

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

11. The film according to 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 according to claim 11, wherein the particle size distribution of the electrode active material particles satisfies (D90 particle size-D10 particle size)/D50 particle size < 1.5.

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

14. A film according to any of claims 10 to 13, wherein the functional material is present in an amount of from 0.05% to 30% by mass of the film.

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

subjecting the first mixture to high pressure shearing with introduction of physical field intervention to fibrillate the binder particles and to arrange the dry particles of the first size in order, then adding dry particles of the other size, and continuing the 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 interwoven by the fibrillated binder and 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. The method of claim 15, wherein the physical field intervention comprises at least one of sonication and magnetic field intervention.

17. An electrode sheet, characterized in that it comprises a current collector and the thin film according to any one of claims 1 to 9 provided on the current collector.

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

19. An electrode sheet, characterized by comprising 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.

20. 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 an electrode sheet as defined in any one of claims 18 and 19 or comprises an electrode sheet as defined in claim 19.

21. A terminal comprising a housing, and a motherboard and a battery located within the housing, the battery comprising an electrochemical cell according to claim 20 for powering the terminal.