CN116682941A - Negative plate, preparation method of negative plate and device using negative plate - Google Patents

Negative plate, preparation method of negative plate and device using negative plate Download PDF

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Publication number
CN116682941A
CN116682941A CN202310889309.XA CN202310889309A CN116682941A CN 116682941 A CN116682941 A CN 116682941A CN 202310889309 A CN202310889309 A CN 202310889309A CN 116682941 A CN116682941 A CN 116682941A
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graphite particles
negative electrode
silicon
electrode sheet
particles
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王凯
黄志轩
齐士博
陈建鹏
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Jiangsu Yaoning New Energy Innovation Technology Co ltd
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Jiangsu Yaoning New Energy Innovation Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The application discloses a negative plate, a preparation method of the negative plate and a device using the negative plate, and belongs to the technical field of secondary batteries. The negative plate provided by the application is as follows: the coating on the current collector and the current collector comprises first graphite particles, second graphite particles and a silicon-based material, wherein the ratio of the median particle diameter D50 of the first graphite particles to the median particle diameter D50 of the second graphite particles is in the range of 1-4:1, and the ratio of the length-diameter ratio of the first graphite particles to the length-diameter ratio of the second graphite particles is in the range of 1-4:1. According to the negative electrode plate coating provided by the application, the first graphite particles with large length-diameter ratio are erected in the expansion and contraction process of the silicon-based material and matched with the second graphite particles with small length-diameter ratio, so that the arrangement of the first graphite particles before charging is recovered more easily after the battery is discharged, and the conductive network is preserved more perfectly. The lithium ion battery using the negative plate has higher energy density and cycle retention rate.

Description

Negative plate, preparation method of negative plate and device using negative plate
Technical Field
The application belongs to the technical field of secondary batteries, and particularly relates to a negative plate, a preparation method of the negative plate and a device using the negative plate.
Background
With the popularization of electronic products such as electric automobiles and smart phones, lithium ion batteries are becoming more and more interesting as batteries with high energy density, long service life and environmental protection. However, the performance requirements of lithium ion batteries are continuously increasing, and lithium ion batteries are required to have both higher energy density and longer cycle life.
Silicon is a material with high capacity, the theoretical specific capacity is up to 4200mAh/g, which is more than 11 times of the theoretical specific capacity of the graphite negative electrode of the commercial lithium ion battery, and the silicon is considered to be the most promising cathode material for commercial application in a short time to improve the energy density of the lithium ion battery, and the silicon can be used as the cathode material of the lithium ion battery. However, silicon is greatly expanded and contracted during charge and discharge, resulting in deformation and destruction of the electrode structure, thereby affecting the cycle performance and safety of the battery. The root cause of the silicon negative electrode expansion and contraction problem is that the volume expansion coefficient of silicon is large, and the expansion direction of silicon is inconsistent with the longitudinal direction of the electrode structure, resulting in deformation and destruction of the electrode structure. Under this expansion, the conductive network of the negative electrode is easily broken, part of the particles lose electrical contact, and the capacity degradation of the battery is accelerated. Therefore, how to inhibit the volume expansion of the silicon material in the charge and discharge process and improve the stability of the silicon-containing negative electrode sheet is a problem that needs to be solved in the application of the silicon material in the negative electrode of the lithium ion battery.
In order to solve the problem of expansion and contraction of the silicon negative electrode, researchers put forward some solutions, such as nanocrystallization treatment of silicon-based materials, compounding of silicon-based materials and other materials, optimal design of electrode structures, optimization of electrolyte and the like, and the effect is not ideal. The silicon and the graphite are directly mixed in a certain proportion, a modification process is not needed, and the slightly low silicon content realizes the larger specific capacity performance improvement compared with a pure graphite electrode, and the problem of poor silicon conductivity is solved. Although the cycle performance of the relatively pure graphite system is reduced, the method is simple and easy to operate and has low cost, and is a mode which is adopted by the industry currently.
CN111416098A discloses a preparation method of a lithium ion battery anode, the active material layer of the anode contains an active material composed of a mixture of graphite particles and silicon particles, wherein the graphite particles comprise first graphite particles and second graphite particles, the particle size D50 of the first graphite particles is 3.2-3.5 microns, the particle size D50 of the second graphite particles is 1.5-1.7 microns, and the particle size D50 of the silicon particles is 1.2-1.5 microns. The application prepares the bottom layer slurry, the middle layer slurry and the surface layer slurry according to different proportions to obtain the cathode, which has higher energy density and rate capability and better cycle stability. CN111554899a discloses a mixing method of a negative electrode slurry, which comprises first graphite particles, second graphite particles and silicon particles, wherein the average particle diameter D50 of the first graphite particles is 2.3-2.5 micrometers, the D50 of the second graphite particles is 0.4-0.5 times of the first graphite particles, the particle diameter D50 of the silicon particles is 360-400nm, and the mass ratio of the first graphite particles, the second graphite particles and the silicon particles is 100:15-17:30-35. According to the application, a step-by-step mixing method is adopted, first graphite particles and second graphite particles are pulped, then silicon particles are added into the slurry to obtain the electrode slurry, the storage time of the electrode slurry is long, the retention property is good, the coating property is good, and the obtained negative electrode has higher energy density and stability. In the prior art, graphite particles with different particle sizes are mixed with silicon particles, so that the energy density is improved to a certain extent, but the battery cycle performance is still not high.
Disclosure of Invention
Aiming at the defects existing in the prior art, the technical problem to be solved by the application is to provide the negative electrode plate prepared by mixing graphite particles with different particle diameters and length-diameter ratios with a silicon-based material, so that the secondary battery prepared by using the negative electrode plate has the characteristics of high quality energy density and long cycle life. The application also solves the technical problem of providing a specific preparation method of the negative plate. The technical problem to be solved finally is to provide a device using the negative plate.
In order to solve the technical problems, the technical scheme adopted by the application is as follows:
a negative electrode sheet comprising: a coating on a current collector and a current collector, the coating comprising first graphite particles, second graphite particles and a silicon-based material, the first graphite particles having a median particle diameter D50 of a, the second graphite particles having a median particle diameter D50 of b, a/b in the range of 1-4:1, the first graphite particles having an aspect ratio of c, the second graphite particles having an aspect ratio of D, the c/D in the range of 1-4:1.
The application designs a negative electrode plate from the aspect of improving the battery cycle performance and considering the quality energy density, the negative electrode active material adopts a mode of mixing a silicon-based material and graphite particles, the used graphite particles are two types of graphite particles with different median particle diameters D50 and length-diameter ratios, the first graphite particles are first graphite particles, and the second graphite particles are second graphite particles relative to the first graphite particles.
Preferably, the first graphite particles have a median particle diameter a of 3 to 22 μm and an aspect ratio c of 1 to 4. The median particle diameter b of the second graphite particles is 3-22 mu m.
In some embodiments, the first graphite particles and the second graphite particles are present in a mass ratio of from 1 to 3:1.
In the application, two kinds of graphite particles with different D50 are selected, and the compactness of the cathode material can be improved within a preferable range, so that the purpose of improving the quality and the energy density of the battery is achieved.
In the present application, the aspect ratio is defined for the graphite particles, specifically, as the aspect ratio of the graphite particles is smaller, that is, closer to 1, the graphite particles are closer to spherical, and as the aspect ratio is larger, the graphite particles are more conspicuous as rod-shaped. The median particle diameter D50 refers to the particle size corresponding to 50vol% of the cumulative volume in the particle size distribution as measured by laser diffraction method when counted from the minimum particle size.
According to some embodiments of the application, within the preferred scope, graphite particles of rod-like structure have significant advantages over spheroidal graphite particles for inhibiting expansion of silicon-based materials. For example, in accordance with some embodiments of the application, within the preferred ranges, the larger the aspect ratio of the first graphite particles within the appropriate range, the lower the full electrical expansion of the cell, and the better the cell cycle performance.
According to some embodiments of the application, the first graphite particles and the second graphite particles are each selected from one of artificial graphite particles, natural graphite particles, composite graphite.
According to some embodiments of the application, the silicon-based material is a silicon-carbon negative electrode material or a silicon-oxygen negative electrode material (silicon-carbon particles and silicon-oxygen particles), and is a core-shell structure, and the second graphite particles are distributed around the core-shell structure.
The silicon-based material with the core-shell structure takes silicon or silicon oxide as a core, the carbon material as a coating layer forms a shell, and the layer thickness is 0.2-1.3 mu m. In this structure, the carbon-based material coating layer can buffer the volume expansion of silicon during lithiation, reduce the contact of active materials with the electrolyte, and prevent aggregation of the nanostructure particles.
The silicon carbon negative electrode material and the silicon oxygen negative electrode material (silicon carbon particles and silicon oxygen particles) preparation method are general.
The silicon-carbon negative electrode material production process comprises the steps of raw material preparation, carbonization, sintering, carbonization sintering and the like. Raw material preparation: the silicon-carbon negative electrode material needs two raw materials of silicon powder and carbon powder, the silicon powder needs to be subjected to procedures of crushing, screening, purifying and the like, and the carbon powder needs to be subjected to procedures of carbonization, crushing and the like; carbonizing: silicon powder and carbon powder are prepared according to a certain proportion, and a proper amount of additive is added for carbonization reaction at high temperature; sintering: sintering the carbonized silicon-carbon composite material at high temperature to crystallize the material and improve the density and hardness of the material. And (3) carbonizing and sintering: and carbonizing and sintering the sintered silicon-carbon composite material at high temperature and high pressure again to ensure that the material has higher conductivity and better electrochemical performance.
The preparation process of the silicon-oxygen anode material comprises the steps of firstly pressing silicon dioxide to form a block-shaped silicon dioxide cake, then uniformly placing the block-shaped silicon dioxide cake in a heating area of a resistance heating device, heating the block-shaped silicon dioxide cake to 1000-1500 ℃, vacuumizing a cavity of the resistance heating device to ensure that the vacuum degree in the cavity is less than or equal to 50pa, and then uniformly introducing silane gas into the cavity. Condensing at the cooling end of the resistance heating device to obtain a silica product, and finally coating the silica product with a carbon material to obtain the silica cathode material.
According to some embodiments of the application, the current collector is a metal foil, including but not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal.
According to some embodiments of the application, the current collector may be copper foil, aluminum foil.
According to some embodiments of the application, the current collector has a thickness of 4 μm to 10 μm.
The preparation method of the negative electrode sheet comprises the following steps: mixing the first graphite particles, the second graphite particles, the silicon-based particles, the conductive agent, the binder and the dispersing agent, adding water, stirring to prepare negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to obtain the negative electrode sheet.
According to some embodiments of the application, the conductive agent includes, but is not limited to: natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver or polyphenylene derivatives.
According to some embodiments of the application, the conductive agent is selected from one or more of conductive carbon black, conductive graphite, carbon nanotubes or acetylene black;
according to some embodiments of the application, the binder includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy or nylon.
According to some embodiments of the present application, the binder is selected from any one or more of carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyurethane, polyvinyl alcohol, or a copolymer of polyvinylpyrrolidone, etc.;
according to some embodiments of the application, the dispersant is selected from any one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and the like.
According to some embodiments of the application, the negative electrode sheet has a post-coating thickness of 120 μm to 170 μm and a post-rolling thickness of 90 μm to 140 μm.
Embodiments of the present application provide an electrochemical device including any device in which an electrochemical reaction occurs.
The electrochemical device of the present application includes a positive electrode having a positive electrode active material capable of occluding and releasing metal ions, a negative electrode according to the present application, an electrolyte, and a separator interposed between the positive electrode and the negative electrode, and may be, for example, a lithium ion battery.
The separator is a member for preventing a short circuit in the battery due to direct contact between the positive electrode and the negative electrode, and a known material can be used. Specifically, the porous polymer film is composed of a porous polymer film such as polyolefin, paper, or the like. As the porous polymer film, a film such as polyethylene or polypropylene is selected since it is not affected by the electrolyte.
The electrolyte is a solution formed of an electrolyte lithium salt compound, an aprotic organic solvent as a solvent, or the like. As the electrolyte lithium salt compound, a lithium salt compound having a wide potential window, which is generally used in lithium ion batteries, can be used. For example, liBF is exemplified 4 、LiPF 6 、LiClO 4 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 、LiN[CF 3 SC(C 2 F 5 SO 2 ) 3 ] 2 And the like, but are not limited to the above. These may be used alone or in combination of two or more.
The present application also provides an electronic device comprising the above-described electrochemical device, i.e. the electronic device may be any device using the electrochemical device according to the present application. The electronic device includes, but is not limited to: notebook computers, pen-input computers, mobile computers, portable printers, headphones, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, toys, game machines, and the like.
Compared with the prior art, the application has the beneficial effects that:
the application provides a negative electrode plate which gives consideration to the cycle performance and the mass energy density of a battery, wherein a coating of the negative electrode plate contains a silicon-based material, two first graphite particles and second graphite particles with different length-diameter ratios and median particle diameter D50, the first graphite particles with large length-diameter ratios are dispersed on the periphery of the silicon-based material to play a role of lapping, the expansion and shrinkage of the silicon-based material are restrained, the full-charge expansion rate of the battery is reduced, the second graphite particles with small length-diameter ratios have good charge and discharge performance, and the first graphite particles are uniformly distributed on the periphery of the silicon-based material to form a conductive network, so that the distribution of the battery before charging is easier to recover after discharging. Therefore, the synergistic effect of two kinds of graphite particles with different length-diameter ratios in the application ensures that the battery cycle retention rate is better and the mass energy density is higher.
Drawings
Fig. 1 is a schematic structural diagram of a negative plate according to an embodiment of the present application.
Detailed Description
The inventive concept, which will be described more fully hereinafter, is susceptible to various modifications and various embodiments, and specific embodiments are shown in the drawings and will be described in more detail. However, the inventive concept should not be construed as being limited to the particular embodiments set forth herein. Rather, these embodiments are to be construed to cover all modifications, equivalents, or alternatives falling within the scope of the inventive concept. For simplicity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.
As used herein, the terms "substantially," "substantially," and "about" are used to describe and illustrate minor variations. When used in connection with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely and instances where it occurs to the close approximation. For example, when used in connection with a numerical value, the term can refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, two values may be considered "substantially" the same if the difference between the two values is less than or equal to ±10% (e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%) of the average value of the values.
In the description herein, unless otherwise indicated, "above", "below" are intended to include the present number, and the meaning of "several" in "one or several" means two or more; the meaning of "at least one" is one or more, i.e., one, two, and more than two.
Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
In the present application, if the particles are spherical, the term "particle size" of the particles refers to the average particle size, while for particles that are not spherical, the term refers to the average major axis length of the particles. Particle size of the particles can be measured using a Particle Size Analyzer (PSA). The "particle size" of the particles may be, for example, the average diameter of the particles. The average particle diameter may be, for example, a median particle diameter (D50). The median particle diameter (D50) refers to the particle size corresponding to 50vol% of the cumulative volume in the particle size distribution as measured by laser diffraction method when counted from the minimum particle size.
Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in the present application can be measured by various measuring methods commonly used in the art.
The application is further illustrated, but not limited, by the following examples.
The following examples and comparative examples were conducted using the following main reaction materials for the preparation of the negative electrode sheet:
silicon carbon material (trademark SA 99-SIO), shanghai Tewang photoelectric materials Co., ltd;
graphite grain (trade mark AML 400), manufactured by guangdong kai Jin Xin energy technology limited;
sodium carboxymethyl cellulose (trade name CMC 2200), a dispersant of japanese celluloid industry, inc;
styrene-butadiene rubber (SBR) binder (brand ETERESM-BA1810, incorporated herein by reference);
the conductive agent is conductive carbon black Super P (trademark ENSACO 250G), very dense high graphite Co., ltd.
Example 1
(1) Preparation of negative electrode sheet
The first graphite particles (D50: 13 μm, aspect ratio: 2), the second graphite particles (D50: 4 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate, wherein the structure of the negative electrode plate is shown in figure 1. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material.
(2) Preparation of positive plate
The positive electrode active material (lithium iron phosphate), the conductive agent (conductive carbon black), the binder (PVDF) and the (carbon nano tube) CNT are mixed according to the mass ratio of 96.5:0.5:2.2:0.8, and then a certain amount of N-methyl pyrrolidone (NMP) is added to be stirred and dispersed to prepare the positive electrode slurry with the solid content of 60+3wt%. And then coating the positive electrode slurry on a positive electrode current collector, and drying, rolling, slitting and tabletting to prepare the positive electrode plate.
(3) Preparation of a Battery
And (3) preparing the prepared positive plate, negative plate and diaphragm lamination into a bare cell, packaging with an aluminum plastic film to prepare a battery, then carrying out the procedures of liquid injection, aging, formation, secondary packaging, capacity division, separation and the like, and finally carrying out the tests of mass energy density, first full charge expansion rate, cycle performance and the like on the battery.
Example 2
Preparing a negative plate: the first graphite particles (D50: 7 μm, aspect ratio: 3), the second graphite particles (D50: 7 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 3
(1) Preparation of negative electrode sheet
The first graphite particles (D50: 14 μm, aspect ratio: 3), the second graphite particles (D50: 4 μm, aspect ratio: 2), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3% by weight. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 4
Preparing a negative plate: the first graphite particles (D50: 13 μm, aspect ratio: 4), the second graphite particles (D50: 4 μm, aspect ratio: 1), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3% by weight. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 5
Preparing a negative plate: the first graphite particles (D50: 13 μm, aspect ratio: 2), the second graphite particles (D50: 3.25 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 6
Preparing a negative plate: the first graphite particles (D50: 22 μm, aspect ratio: 4), the second graphite particles (D50: 11 μm, aspect ratio: 3), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3% by weight. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 7
Preparing a negative plate: the first graphite particles (D50 is 10 νm, length-diameter ratio is 4), the second graphite particles (D50 is 5 μm, length-diameter ratio is 4), silicon carbon material (D50 is 5.5 μm), conductive agent, binder (SBR) and dispersant (CMC) are mixed according to the mass ratio of 70:20:5.5:0.5:2:1.5, and then water is added and stirred to prepare the cathode slurry with solid content of 50+ -3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 8
Preparing a negative plate: the first graphite particles (D50: 6 μm, aspect ratio: 3.5), the second graphite particles (D50: 3 μm, aspect ratio: 1), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 9
Preparing a negative plate: the first graphite particles (D50: 18 μm, aspect ratio: 3), the second graphite particles (D50: 6 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Example 10
Preparing a negative plate: the first graphite particles (D50: 16 μm, aspect ratio: 4), the second graphite particles (D50: 10 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Comparative example 1
Preparing a negative plate: filler particles (first graphite particles) (D50: 13 μm, aspect ratio: 2), a silicon carbon material (D50: 5.5 μm), a conductive agent, a binder (SBR) and a dispersant (CMC) were mixed in a mass ratio of 90:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3% by weight. Namely, in the anode slurry, the filler particles (first graphite particles) account for 94.2wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Comparative example 2
Preparing a negative plate: filler particles second graphite particles (D50 of 4 μm, aspect ratio of 1.5), silicon carbon material (D50 of 5.5 μm), conductive agent, binder (SBR) and dispersant (CMC) were mixed in a ratio of 90:5.5:0.5:2: 1.5, and then adding water and stirring to prepare the cathode slurry with the solid content of 50+/-3 weight percent. Namely, in the anode slurry, the filler particles (first graphite particles) account for 94.2wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Comparative example 3
Preparing a negative plate: the first graphite particles (D50: 15 μm, aspect ratio: 3.5), the second graphite particles (D50: 3 μm, aspect ratio: 1.5), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3 wt%. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
Comparative example 4
Preparing a negative plate: the first graphite particles (D50: 10 μm, aspect ratio: 5), the second graphite particles (D50: 4 μm, aspect ratio: 1), the silicon carbon material (D50: 5.5 μm), the conductive agent, the binder (SBR) and the dispersant (CMC) were mixed in a mass ratio of 70:20:5.5:0.5:2:1.5, and then water was added thereto and stirred to prepare a negative electrode slurry having a solid content of 50.+ -. 3% by weight. Namely, in the anode slurry, the first graphite particles account for 73.3wt% of the anode active material, the second graphite particles account for 20.9wt% of the anode active material, and the silicon-based material accounts for 5.7wt% of the anode active material. And then coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode plate. The blending amount of the silicon-based material in this example was 5.7wt% in the whole negative electrode active material. The rest of the procedure is the same as in example 1.
The example and comparative test data are listed in table 1 as follows:
table 1 lithium ion battery performance test results
From the test results of examples 1 to 10 in Table 1, it was revealed that when the first graphite particles and the second graphite particles were used to prepare the negative electrode sheet, when the ratio (a/b) of the first graphite particles D50 to the second graphite particles D50 was 1 to 4, and the ratio (c/D) of the aspect ratio of the first graphite particles to the aspect ratio of the second graphite particles was also 1 to 4, the mass energy density could be maintained at about 208Wh/kg, the first full charge expansion ratio was not less than 28%, the 500-cycle retention ratio could be maintained at 91% or less, and from comparative examples 1 to 2, the mass energy density and the 500-cycle retention ratio were both greatly reduced, and the first full charge expansion ratio was as high as about 30%, as seen from comparative examples 3 to 4, even when the ratio (a/b) of the first graphite particles D50 to the second graphite particles or the ratio of the first aspect ratio to the second graphite particles (c/D) was selected to be within the range of 1 to 4, and the mass expansion ratio was still high as compared to 500-cycle retention ratio was maintained at the outside the full charge expansion ratio of the range of 1 to 4. In conclusion, the particle size and the length-diameter ratio of the two graphite particles in the negative plate coating are limited in a proper range, so that the expansion of the negative plate can be effectively inhibited, and the quality energy density and the cycle performance of the battery are improved.

Claims (13)

1. A negative electrode sheet, comprising: and a coating on the current collector and the current collector, wherein the coating comprises first graphite particles, second graphite particles and a silicon-based material, the ratio of the median particle diameter D50 of the first graphite particles to the median particle diameter D50 of the second graphite particles is in the range of 1-4:1, and the ratio of the length-diameter ratio of the first graphite particles to the length-diameter ratio of the second graphite particles is in the range of 1-4:1.
2. The negative electrode sheet according to claim 1, wherein the first graphite particles and the second graphite particles are each selected from one of artificial graphite particles, natural graphite particles, and composite graphite.
3. The negative electrode sheet according to claim 1, wherein the first graphite particles D50 are 3 to 22 μm, the second graphite particles have a median particle diameter D50 of 3 to 22 μm, and the first graphite particles have an aspect ratio of 1 to 4.
4. The negative electrode sheet of claim 1, wherein the mass ratio of the first graphite particles to the second graphite particles is 1-3:1.
5. The negative electrode sheet according to claim 1, wherein the silicon-based material is silicon carbon particles or silicon oxygen particles.
6. The negative electrode sheet according to claim 1, wherein the silicon-based material is a core-shell structure, the core is a silicon-containing component, the shell is a carbon layer, and the thickness of the shell is 0.2-1.3 μm.
7. The negative plate of claim 1, wherein the second graphite particles are distributed around the silicon-based material.
8. The negative electrode sheet according to claim 1, wherein the current collector is a metal foil, and the thickness of the current collector is 4-10 μm.
9. The method for producing a negative electrode sheet according to any one of claims 1 to 8, characterized by comprising: mixing the first graphite particles, the second graphite particles, the silicon-based material, the conductive agent, the binder and the dispersing agent, adding water, stirring to prepare negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector through coating equipment, and drying, rolling, slitting and tabletting to prepare the negative electrode sheet.
10. The method for producing a negative electrode sheet according to claim 9, wherein the conductive agent is one or more selected from the group consisting of conductive carbon black, conductive graphite, carbon nanotube and acetylene black; the adhesive is one or more selected from carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyurethane, polyvinyl alcohol or polyvinylpyrrolidone copolymer; the dispersing agent is selected from one of carboxymethyl cellulose, sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.
11. The method for producing a negative electrode sheet according to claim 9, wherein the negative electrode sheet has a thickness of 120 to 170 μm after coating and a thickness of 90 to 140 μm after rolling.
12. An electrochemical device, comprising: a positive electrode sheet, the negative electrode sheet of any one of claims 1 to 8, a separator, and an electrolyte.
13. An electronic device comprising the electrochemical device of claim 12.
CN202310889309.XA 2023-07-19 2023-07-19 Negative plate, preparation method of negative plate and device using negative plate Pending CN116682941A (en)

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