CN115312697A - Negative pole piece and battery - Google Patents

Negative pole piece and battery Download PDF

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Publication number
CN115312697A
CN115312697A CN202211138102.0A CN202211138102A CN115312697A CN 115312697 A CN115312697 A CN 115312697A CN 202211138102 A CN202211138102 A CN 202211138102A CN 115312697 A CN115312697 A CN 115312697A
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China
Prior art keywords
graphite
silica
negative pole
lithium
electrolyte
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CN202211138102.0A
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Inventor
唐文
董英男
张业琼
刘娇
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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Priority to CN202211138102.0A priority Critical patent/CN115312697A/en
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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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

Abstract

The invention discloses a negative pole piece and a battery, and relates to the technical field of batteries; this negative pole piece includes that the negative pole mass flow body and the negative pole diaphragm that sets up in at least one side surface of the negative pole mass flow body, and the negative pole diaphragm includes negative pole active material and negative pole conducting agent, and negative pole active material includes graphite and silica based material, and the negative pole conducting agent includes carbon nanotube, and graphite, silica based material and carbon nanotube three satisfy the formula: 0.5 π × d F >0.9D sio +0.125D G To be atThe carbon nano tube can crosslink graphite and a silica-based material in the charging and discharging processes; wherein D is sio Is the median particle diameter of the silica-based material, d F Is the average Ferrett length, D, of the carbon nanotubes G The unit of the graphite is the median particle size of the graphite, and the unit of the graphite, the median particle size and the unit of the graphite are um. The carbon nanotube of the negative pole piece can cross-link graphite and silicon-based materials at any time in the charging and discharging process, the charging and discharging power performance of the negative pole piece can be improved, and the cycle life of the negative pole piece is prolonged.

Description

Negative pole piece and battery
Technical Field
The invention relates to the technical field of batteries, in particular to a negative pole piece and a battery.
Background
With the development of science and technology, the electric tool driving is becoming a trend, including travel tools such as electric bicycles, automobiles and developing electric airplanes. This presents a significant challenge to the energy density and power performance of lithium ion batteries.
The energy density of the lithium ion secondary battery formed by matching the traditional graphite cathode with the anode material is a bottleneck, and the requirements of lighter battery and higher energy are difficult to meet. Increasing the capacity of the negative electrode is an effective means for increasing the energy density of the battery, and therefore a silicon-based negative electrode with high gram capacity is an effective choice.
The silicon-based negative electrode mainly comprises a nano silicon-based material and a silica-based material. In the circulation process of the nano silicon-based negative electrode material, because the influence of the small volume effect of silicon particles on the volume is limited, the silicon material with relatively large circulation particles can have smaller volume expansion and structural stability, but because the nano silicon has small volume, more particles, more reactive active sites and more side reactions with electrolyte, the capacity attenuation in the circulation process is faster; silica-based negative electrode material (SiO) x ) The gram capacity is usually 3-6 times of that of graphite, and because free silicon oxide is used as an expansion buffer layer and an ion conductor in the lithiation process, the cycle life of the silicon-based negative electrode can be effectively prolonged, so that the energy density is improved.
Pure silica as a negative active material causes excessive expansion of a negative electrode sheet and is easy to cause dusting and demoulding, so that a composite active material with required gram capacity is obtained by mixing with graphite. However, the silicon-based material has poor electronic conductivity, and shrinks after lithium removal due to lithiation expansion, so that large gaps are formed between the silicon-based material and graphite particles, the charge-discharge power performance is poor, and even capacity loss caused by electrical contact separation occurs.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a negative pole piece and a battery with high power performance and long cycle life.
The embodiment of the invention is realized by the following steps:
in a first aspect, the present invention provides a negative electrode plate, including:
the negative pole mass flow body and set up in the negative pole diaphragm of at least one side surface of the negative pole mass flow body, the negative pole diaphragm includes negative pole active material and negative pole conducting agent, and the negative pole active material includes graphite and silica-based material, and the negative pole conducting agent includes carbon nanotube, and graphite, silica-based material and carbon nanotube three satisfy the formula: 0.5 π × d F >0.9D sio +0.125D G So that the carbon nano tube can crosslink graphite and silica-based material in the charging and discharging process;
wherein D is sio Is the median particle diameter of the silica-based material, d F Is the average Ferrett length, D, of the carbon nanotubes G The unit of the graphite is the median particle size of the graphite, and the unit of the graphite, the median particle size and the unit of the graphite are um.
In an alternative embodiment, the silica-based material has a median particle size in the range of 4 um. Ltoreq.D sio ≤10um；
And/or the presence of a gas in the atmosphere,
the average Ferrett length of the carbon nano tube is within the range of 5um to d F ≤9um；
And/or the presence of a gas in the gas,
the median diameter of the graphite is within the range of 5um to D G ≤20um。
In alternative embodiments, the carbon nanotubes are at least one of single-walled carbon nanotubes and oligowalled carbon nanotubes; preferably, the carbon nanotubes are single-walled carbon nanotubes;
and/or the presence of a gas in the atmosphere,
the graphite is at least one of natural graphite and artificial graphite;
and/or the presence of a gas in the atmosphere,
the silica-based material is at least one of silica-based particles, carbon-coated silica-based particles, polymer-coated silica-based particles, lithium-containing silica-based particles, and magnesium-containing silica-based particlesSeed; the chemical formula of the silica-based particles is SiO x Wherein, 0.72<x<1.2。
In an alternative embodiment, the negative electrode conductive agent further comprises conductive carbon black;
preferably, the negative electrode membrane further comprises a thickener and a binder;
preferably, the mass ratio of the negative electrode active material, the conductive carbon black, the carbon nanotubes, the thickener and the binder is (80-97): (1-8): (0.01-0.5): (0.5-5): (1-5);
preferably, the thickener comprises sodium carboxymethyl cellulose; the binder comprises at least one of polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, styrene butadiene rubber, sodium carboxymethylcellulose, sodium alginate, polymethacrylic acid and carboxymethyl chitosan.
In an alternative embodiment, the mass ratio of graphite to silica-based material is (0.01-98): 2-100;
preferably, the mass ratio of the graphite to the silica-based material is (88-92): (8-12).
In alternative embodiments, the negative electrode current collector is a copper foil, a carbon-coated copper foil, or a polymer conductive film.
In a second aspect, the present invention provides a battery comprising a negative electrode tab according to any one of the preceding embodiments; the lithium battery also comprises a shell, a positive pole piece, an isolating membrane and electrolyte; the positive pole piece, the isolating membrane and the negative pole piece are sequentially stacked and arranged, and wound or laminated to form a bare cell, the bare cell is arranged in the shell, and the electrolyte is contained in the shell.
In an alternative embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode membrane disposed on at least one side surface of the positive electrode current collector;
preferably, the positive electrode current collector is an aluminum foil, a nickel foil or a polymer conductive film;
preferably, the positive membrane comprises a positive active material, a positive conductive agent and a binder in a mass ratio of (95-98) to (1-2);
preferably, the positive active material is at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide, and doping and/or coating modification compounds thereof.
In an alternative embodiment, the electrolyte is at least one of an organic liquid electrolyte, a solid organic electrolyte, a solid ceramic electrolyte and a gel electrolyte;
preferably, the electrolyte is an organic liquid electrolyte, and the electrolyte of the organic liquid electrolyte comprises at least one of lithium difluorophosphate, lithium hexafluorophosphate, lithium difluorooxalato phosphate, lithium difluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium tetrafluoroborate and lithium difluorooxalato borate;
preferably, the electrolyte is an organic liquid electrolyte, and a solvent of the organic liquid electrolyte includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, and ethyl propionate;
preferably, the electrolyte is an organic liquid electrolyte, and the additive of the organic liquid electrolyte comprises at least one of vinylene carbonate, vinyl ethylene carbonate, vinyl sulfate, ethylene sulfite, methylene methanedisulfonate, 1, 3-propane sultone, propylene sulfate, trimethylsilylphosphate, trimethylsilylborate, and fluoroethylene carbonate.
In alternative embodiments, the separator film is a polyethylene film, a polypropylene film, a nonwoven fabric film, and at least one of a composite film thereof, a ceramic-modified film, and a PVDF-modified film.
The embodiment of the invention has at least the following advantages or beneficial effects:
the negative pole piece provided by the embodiment of the invention comprises a negative pole current collector and a negative pole diaphragm arranged on at least one side surface of the negative pole current collector, wherein the negative pole diaphragm comprises a negative pole active material and a negative pole conductive agent, the negative pole active material comprises graphite and a silica-based material, the negative pole conductive agent comprises a carbon nano tube, and the graphite, the silica-based material and the carbon nano tube meet the formula: 0.5 π × d F >0.9D sio +0.125D G To make the carbon nano-tube cross-link graphite and cuprous oxide in the charging and discharging processA silicon-based material; wherein D is sio Is the median particle diameter of the silica-based material, d F Is the average Ferrett length, D, of the carbon nanotubes G The unit of the graphite is the median particle size of the graphite, and the graphite, the median particle size and the unit of the graphite are um.
The negative pole piece utilizes the toughness and the scalability of the carbon nano tube, the carbon nano tube with a proper tube length is limited to be matched with the graphite and the silica-based material with proper particle size for use, the conductive crosslinking effect of the carbon nano tube can be exerted to the maximum, so that the carbon nano tube can crosslink the graphite and the silica-based material at any time in the charging and discharging process, the expansion problem caused by the silica-based material is relieved, a conductive network is formed, the conductive connection relation between the silica-based material and the graphite material is fully improved, the charging and discharging power performance of the negative pole piece is improved, and the cycle life of the negative pole piece is prolonged.
The embodiment of the invention also provides a battery which comprises the negative pole piece. Therefore, the battery also has the advantages of high functional performance and long cycle life.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
The features and properties of the present invention are described in further detail below with reference to examples.
Pure silica as a negative active material causes excessive expansion of a negative electrode sheet and is easy to cause dusting and demoulding, so that a composite active material with required gram capacity is obtained by mixing with graphite. However, the silicon-based material has poor electronic conductivity, and shrinks after lithium removal due to lithiation expansion, so that large gaps are formed between the silicon-based material and graphite particles, the charge-discharge power performance is poor, and even capacity loss caused by electrical contact separation occurs.
In view of this, embodiments of the present invention provide a negative electrode plate using a carbon nanotube as a conductive agent, and the use of the carbon nanotube with high strength, good flexibility, and strong conductive capability can effectively improve the conductive connection between a silicon-based material and a graphite material, improve the charge-discharge power characteristics, and improve the cycle life.
In detail, the negative electrode tab provided by the embodiment of the invention comprises a negative electrode current collector and a negative electrode diaphragm arranged on at least one side surface of the negative electrode current collector. The negative electrode current collector is, for example, a copper foil, a carbon-coated copper foil, or a polymer conductive film, and preferably a copper foil. Meanwhile, the negative current collector is provided with negative diaphragms along two side surfaces in the thickness direction. And the negative diaphragm is obtained by coating the negative slurry on a negative current collector, drying and cold pressing. The negative electrode slurry includes a negative electrode active material, a negative electrode conductive agent, a binder, a thickener, and a solvent. The negative electrode active material comprises graphite and a silica-based material, the negative electrode conductive agent comprises a carbon nano tube and conductive carbon black, the binder comprises at least one of polyacrylic acid (PAA), sodium Polyacrylate (PAAS), polyvinyl alcohol (PVA), styrene Butadiene Rubber (SBR), sodium carboxymethyl cellulose (CMC), sodium Alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS), and the thickening agent comprises sodium carboxymethyl cellulose. In the examples of the present invention, styrene butadiene rubber is used as an example of the binder, and sodium carboxymethylcellulose is used as an example of the thickener. The solvent may be selected to be deionized water.
And, graphite, silica-based materials and carbon nanotubes satisfy the formula: 0.5 π × d F >0.9D sio +0.125D G So that the carbon nano tube can crosslink the graphite and the silica-based material in the charging and discharging process; wherein D is sio The median particle size of the silica-based material is measured by a laser particle size analyzer, and the measuring method is executed according to the national standard GB/T19077-2016 particle size distribution laser diffraction method. d F The carbon nanotubes are imaged by using a scanning electron microscope or a projection electron microscope, and the Ferrett length of the carbon nanotubes is determined by randomly taking the average of the Ferrett maximum lengths of the long sides of 50 carbon nanotubes. D G Is the median value of graphiteThe particle size is tested by adopting a laser particle sizer, and the testing method is executed according to the national standard GB/T19077-2016 particle size distribution laser diffraction method. The three units are um.
Although the carbon nanotubes can improve the conductivity of the pole piece to a certain extent, the carbon nanotubes, especially the single-walled carbon nanotubes, have a short length, and the silica particles and the graphite have a small size, and if the particles of the silica-based material are relatively large, the short carbon nanotubes are difficult to perform the functions of crosslinking the silica-based material and the graphite, so that the effects of improving the conductivity and relieving the expansion are difficult to perform, and at the moment, even if the amount of the carbon nanotubes is increased, the improvement effect is limited.
Therefore, in the embodiment of the invention, the negative pole piece utilizes the toughness and scalability of the carbon nano tube, and the carbon nano tube with a proper tube length is limited to be matched with the graphite and the silica-based material with proper particle size for use, so that the conductive crosslinking effect of the carbon nano tube can be exerted to the maximum, the carbon nano tube can crosslink the graphite and the silica-based material at any time in the charging and discharging process, the expansion problem caused by the silica-based material is relieved, a conductive network is formed, the conductive connection relation between the silica-based material and the graphite material is fully improved, the charging and discharging power performance of the negative pole piece is improved, and the cycle life of the negative pole piece is prolonged.
Illustratively, the median particle size of the silica-based material ranges from 4um ≦ D sio Not more than 10um, and the average Ferrett length of the carbon nano tube has a value range of 5um not more than d F Not more than 9um, and the median diameter of the graphite is not less than 5um and not more than D G Is less than or equal to 20um. The sizes of the three are limited within the range, and when the sizes meet the requirements of the formula, the carbon nano tube can cross-link the silicon-based material and the graphite all the time along with the expansion and contraction of the silicon-based material in the charging and discharging processes, so that the functional performance and the cycle performance of the negative pole piece can be fully improved. Of course, in other embodiments of the present invention, the respective value ranges of the three may be further fine-tuned to satisfy 0.5 π × d F >0.9D sio +0.125D G The formula is limited, and the embodiment of the present invention is not limited.
In the embodiment of the present invention, the carbon nanotube is at least one of a single-walled carbon nanotube and an oligowalled carbon nanotube. The single-walled carbon nanotube has the wall number of 1, has excellent electronic, mechanical and other properties, and particularly has ultrahigh mobility to electrons and holes. The carbon nanotubes with few average walls have the average wall number of 3-6, and also have the characteristics of high strength, good flexibility and strong conductive capability. Illustratively, in embodiments of the present invention, the carbon nanotubes are all single-walled carbon nanotubes. The single-walled carbon tube has more excellent performance in a silicon-based battery system, and can further improve the power performance and the cycle performance of the negative pole piece.
It is further noted that, in the embodiment of the present invention, the graphite is at least one of natural graphite and artificial graphite; the silica-based material is at least one of silica-based particles, carbon-coated silica-based particles, polymer-coated silica-based particles, lithium-containing silica-based particles and magnesium-containing silica-based particles; the chemical formula of the silica-based particles is SiO x Wherein, 0.72<x<1.2. Illustratively, the embodiments of the present invention are described by taking graphite as artificial graphite and silica-based materials as silica-based particles as examples.
In addition, it should be noted that, in the embodiment of the present invention, the mass ratio of the negative electrode active material, the conductive carbon black, the carbon nanotube, the sodium carboxymethyl cellulose, and the styrene butadiene rubber in the negative electrode slurry is (80-97): (1-8): (0.01-0.5): (0.5-5): (1-5), illustratively, optionally 95.5: 1.4:2. The mass ratio of graphite to silica-based material is (0.01-98): (2-100), preferably alternatively (88-92): (8-12), and exemplarily alternatively 90. On one hand, by limiting the using amount of the carbon nano tube, the negative effect caused by the expansion of the silicon-based material can be effectively relieved while the cost is controlled, so that the negative pole piece can have better conductivity and power performance. On the other hand, by controlling the proportion of the silicon-based material in the negative active material, the cycle performance of the negative pole piece can be ensured, the energy density of the negative pole piece can be ensured, and the performance of the battery is optimized.
The embodiment of the invention also provides a battery, which comprises the negative pole piece; the lithium battery also comprises a shell, a positive pole piece, an isolating membrane and electrolyte; the positive pole piece, the isolating membrane and the negative pole piece are sequentially stacked and arranged, and wound or laminated to form a bare cell which is arranged in the shell, and the electrolyte is contained in the shell.
In detail, the positive electrode sheet includes a positive electrode current collector and a positive electrode membrane disposed on at least one side surface of the positive electrode current collector. The positive current collector is an aluminum foil, a nickel foil or a polymer conductive film, and preferably, the positive current collector is an aluminum foil, and positive diaphragms are disposed on both side surfaces of the positive current collector in the thickness direction. The positive diaphragm is obtained by coating positive slurry on a positive current collector, drying and cold pressing, wherein the positive slurry comprises a positive active material, a positive conductive agent, a binder and a solvent in a mass ratio of (95-98) to (1-2).
The positive active material is at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide and doped and/or coated modified compounds thereof. Illustratively, the positive active material may be selected as NCM811, the conductive agent may be selected as conductive carbon black Super-P, the binder may be selected as polyvinylidene fluoride PVDF, and the solvent may be selected as N-methylpyrrolidone NMP. In other embodiments, the types of the conductive agent, the binder and the solvent in the positive electrode plate can be selected according to requirements, and are not described herein again.
The electrolyte is at least one of organic liquid electrolyte, solid organic electrolyte, solid ceramic electrolyte and gel electrolyte. Illustratively, the electrolyte is an organic liquid electrolyte, and the organic liquid electrolyte includes an electrolyte, a solvent, and an additive. Wherein the electrolyte comprises lithium hexafluorophosphate LiPF6 and lithium difluorophosphate LiPO 2 F 2 Lithium difluorooxalato phosphate LiDFOP, lithium bis (fluorosulfonylimide) LiFSI, lithium bis (trifluoromethanesulfonylimide) LiTFSi, and lithium tetrafluoroborate LiBF 4 And lithium difluoroborate LiDFOB.
The solvent comprises one or more of ethylene carbonate EC, propylene carbonate PC, diethyl carbonate DEC, dimethyl carbonate DMC, ethyl methyl carbonate EMC, methyl acetate MA, ethyl acetate EA, ethyl propionate EP.
The additive comprises one or more of vinylene carbonate VC, vinyl carbonate VEC, vinyl sulfate DTD, vinyl sulfite ES, methylene methanedisulfonate MMDS, 1, 3-propane sultone PS, propylene sultone PES, propylene sulfate TMS, trimethylsilylphosphate TMSP, trimethylsilylborate TMSB, and fluoroethylene carbonate FEC. Illustratively, in embodiments of the present invention, the electrolyte is: 1M LiPF6 and 2 volume ratio of DMC, EMC, FEC according to the formulation. In other embodiments, the electrolyte with corresponding types and components may be selected according to requirements, and the embodiments of the present invention are not limited.
The isolation membrane is at least one of a polyethylene membrane, a polypropylene membrane, a non-woven fabric membrane, and a composite membrane, a ceramic modified membrane and a PVDF modified membrane thereof. The composite film is formed by a polyethylene film, a polypropylene film and a non-woven fabric, the ceramic modified film is formed by coating a ceramic coating on the surface of a substrate film, and the PVDF modified film is formed by coating PVDF modified films on the surfaces of the polyethylene film, the polypropylene film and the non-woven fabric film. Illustratively, in embodiments of the present invention, the release film is a polyethylene film.
The above-described battery preparation process and the battery performance are described in detail below by way of specific examples, comparative examples and experimental examples:
example 1
The present example provides a battery, which is prepared by the following method:
s1: the preparation of the positive pole piece specifically comprises the following steps:
mixing a positive electrode active material NCM811, conductive carbon black Super-P and a binding agent polyvinylidene fluoride PVDF according to a mass ratio of 97 to 1, adding a solvent N-methylpyrrolidone NMP, stirring in vacuum to obtain uniform positive electrode slurry, uniformly coating the positive electrode slurry on two sides of an aluminum foil in the thickness direction, and drying, cold pressing and cutting to obtain a positive electrode piece.
S2: the preparation of the negative pole piece specifically comprises the following steps:
mixing a negative electrode active material, conductive carbon black Super-P, a conductive carbon black tube CNT, a binder carboxymethyl cellulose sodium CMC and a binder SBR according to a mass ratio of 95.5;
wherein the negative active material comprises silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 4.5um, average median particle diameter D of graphite G 12um, feret length d of carbon nanotubes F Is 5.3um,0.5 pi x d F ＝8.321，0.9D sio +0.125D G =5.55, difference 2.771,0.5 pi × d F >0.9D sio +0.125D G 。
S3: the preparation of the battery specifically comprises the following steps:
mix 1M LiPF6 and volume ratio for 2 DMC, EMC and FEC and obtain electrolyte, obtain naked electric core with positive pole piece, negative pole piece, barrier film assembly, naked electric core is arranged in the shell, pours into above-mentioned configuration electrolyte into after the drying, then processes such as encapsulation, stewing, formation, partial volume back, obtains lithium ion secondary battery, and its capacity design is 8Ah.
Example 2
This example is different from example 1 in that, in step S2 of example 2, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 4.5um, average median particle diameter D of graphite G 16.4um, feret length d of carbon nanotubes F Is 5.3um,0.5 pi x d F ＝8.321，0.9D sio +0.125D G =6.1, difference 2.221,0.5 pi × d F >0.9D sio +0.125D G 。
Example 3
This example is different from example 1 in that in step S2 of example 2, a negative electrode active materialThe material comprises silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 6.2um, average median particle diameter D of graphite G 16.4um, feret length d of carbon nanotubes F Is 5.3um,0.5 pi x d F ＝8.321，0.9D sio +0.125D G =7.63, difference is 0.691,0.5 pi × d F >0.9D sio +0.125D G 。
Example 4
This example is different from example 1 in that, in step S2 of example 2, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 9.6um, average median particle diameter D of graphite G 16.4um, feret length d of carbon nanotubes F Is 8.4um,0.5 pi x d F ＝13.188，0.9D sio +0.125D G =10.69, difference 2.498,0.5 pi × d F >0.9D sio +0.125D G 。
Example 5
This example is different from example 1 in that, in step S2 of example 2, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 12.
Example 6
This example is different from example 1 in that, in step S2 of example 2, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 8.
Comparative example 1
Comparative example 1 provides a battery, which is different from example 1 in that, in step S2 of comparative example 1, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 9.6um, average median particle diameter D of graphite G 16.4um, feret length d of carbon nanotubes F Is 5.3um,0.5 pi x d F ＝8.321，0.9D sio +0.125D G =10.69, difference is-2.369, 0.5 pi × d F <0.9D sio +0.125D G 。
Comparative example 2
Comparative example 2 provides a battery, which is different from example 1 in that, in step S2 of comparative example 2, the anode active material includes silica-based particles and artificial graphite in a mass ratio of 10. Average median particle diameter D of the silica-based particles sio 11.1um, average median particle diameter D of graphite G 21.2um, feret length d of carbon nanotubes F Is 4.3um,0.5 pi x d F ＝6.751，0.9D sio +0.125D G =12.64, difference-5.889, 0.5 pi × d F <0.9D sio +0.125D G 。
Comparative example 3
Comparative example 3 provides a battery, which is different from comparative example 1 in that, in step S2 of comparative example 3, the negative active material includes silica-based particles and artificial graphite in a mass ratio of 12.
Comparative example 4
Comparative example 4 provides a battery, which is different from comparative example 1 in that, in step S2 of comparative example 4, the negative active material includes silica-based particles and artificial graphite in a mass ratio of 8.
Comparative example 5
Comparative example 5 provides a battery, which is different from example 1 in that, in step S2 of comparative example 5, the conductive agent of the negative electrode tab includes only conductive carbon black without carbon nanotubes.
Experimental example 1
The batteries provided in examples 1 to 6 and comparative examples 1 to 5 were subjected to a cycle life test under the same conditions that the obtained lithium ion secondary batteries were charged at a rate of 1C and discharged at a rate of 1C at 25C, and a full charge discharge cycle test was performed until the capacity of the lithium ion secondary battery was attenuated to 80% of the initial capacity, and the number of cycles was recorded. The test results are shown in table 1.
TABLE 1 cycle life test results
Figure BDA0003852203980000121
As can be seen from the comparison of the data of examples 1 to 6 and comparative examples 1 to 5 in table 1, the method for preparing the battery provided in this example can effectively improve the cycle performance of the battery and prolong the cycle life of the battery by using carbon nanotubes of appropriate size. Meanwhile, as can be seen from comparison of examples 1 to 4 with examples 5 and 6, and comparison of comparative examples 1 and 3 and 4, the smaller the proportion of the silicon-based material in the negative electrode active material is, the better the cycle performance is, with the carbon nanotubes. However, since the energy density can be improved based on the silicon-based material, the proportion of the silicon-based material is preferably controlled to be within 12%. Meanwhile, according to the comparison between examples 1 to 6 and comparative example 1, when the graphite, the silica-based material and the carbon nanotube satisfy the formula: 0.5 π × d F >0.9D sio +0.125D G The cycle performance of the battery can be remarkably improved. From the comparison of examples 1 to 6, comparative example 1 and comparative example 2, it can be seen that when the formula is not satisfied for all of graphite, a silica-based material and carbon nanotubes: 0.5 π × d F >0.9D sio +0.125D G And Dsio does not satisfy Dsio is not less than 4um and not more than 10um, d F D is not more than 5um F ≤9um、D G D is not more than 5um G The cycle performance of the battery is the worst when the diameter is less than or equal to 20um.
Experimental example 2
The batteries provided in examples 1 to 6 and comparative examples 1 to 5 were subjected to a discharge power test under the same conditions under which the obtained lithium ion secondary batteries were discharged at a 20% state of charge at a power density of 1200W/kg to a cut-off of 2.5V, which is the lower voltage limit, at 25 c, and the discharge time was recorded. The test results are shown in table 2.
TABLE 2 discharge Power test results
Figure BDA0003852203980000131
As can be seen from comparison of data of examples 1 to 6 with comparative examples 1 to 5 in Table 2, the method for manufacturing a battery according to the present example can effectively improve the power performance of the battery by using carbon nanotubes having an appropriate size. Meanwhile, according to the comparison between examples 1 to 4 and examples 5 and 6, and the comparison between comparative example 1 and comparative examples 3 and 4, on the premise of having the carbon nanotube, although the smaller the proportion of the silicon-based material in the negative electrode active material, the less the power reduction problem caused by the poor electron conductivity of the silicon-based material, the power performance is directly related to the particle size of the material, and the increased silicon-based material can improve the energy density to some extent, so that it is appropriate to control the proportion of the silicon-based material within 12% in order to ensure the comprehensive electrochemical performance and the service performance of the battery. Meanwhile, according to the comparison between examples 1 to 6 and comparative example 1, when the graphite, the silica-based material and the carbon nanotube satisfy the formula: 0.5 π × d F >0.9D sio +0.125D G The power performance of the battery can be obviously improved. From the comparison of examples 1 to 6, comparative example 1 and comparative example 2, it can be seen that when the formula is not satisfied for the graphite, the silica-based material and the carbon nanotube: 0.5 π × d F >0.9D sio +0.125D G And Dsio does not satisfy Dsio is not less than 4um and not more than 10um, d F D is not more than 5um F ≤9um、D G D is not more than 5um G The power performance of the battery is the worst when the battery is less than or equal to 20um.
According to the data in tables 1 and 2, it can be seen that the negative electrode plate provided in the embodiment of the present invention utilizes the toughness and scalability of the carbon nanotube itself, and by limiting the carbon nanotube with a suitable length to be used in combination with the graphite and the silica-based material with a suitable particle size, the conductive crosslinking effect of the carbon nanotube can be maximized, so that the carbon nanotube can crosslink the graphite and the silica-based material at any time in the charging and discharging process, thereby alleviating the expansion problem caused by the silica-based material, forming a conductive network, sufficiently improving the conductive connection relationship between the silica-based material and the graphite material, improving the charging and discharging power performance of the negative electrode plate, and prolonging the cycle life of the negative electrode plate.
In summary, the embodiments of the present invention provide a negative electrode plate and a battery with high power performance and long cycle life.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A negative electrode sheet, comprising:
the negative pole mass flow body with set up in the negative pole diaphragm of at least one side surface of the negative pole mass flow body, the negative pole diaphragm includes negative pole active material and negative pole conducting agent, the negative pole active material includes graphite and silica-based material, the negative pole conducting agent includes carbon nanotube, just graphite, silica-based material with the carbon nanotube three satisfies the formula: 0.5 π × d F >0.9D sio +0.125D G To enable the carbon nanotubes to cross-link the graphite and the silica-based material during charging and discharging;
wherein D is sio Is the median particle diameter of the silica-based material, d F Is the average Ferrett length, D, of the carbon nanotubes G The unit of the three is um, which is the median particle size of the graphite.
2. The negative electrode tab of claim 1, wherein:
the value range of the median particle diameter of the silica-based material is D which is not less than 4um sio ≤10um；
And/or the presence of a gas in the gas,
the average Feret length of the carbon nano tube is within a value range of d being more than or equal to 5um F ≤9um；
And/or the presence of a gas in the gas,
the value range of the median diameter of the graphite is that D is more than or equal to 5um G ≤20um。
3. The negative electrode tab of claim 1, wherein:
the carbon nanotube is at least one of a single-walled carbon nanotube and an oligowalled carbon nanotube; preferably, the carbon nanotubes are single-walled carbon nanotubes;
and/or the presence of a gas in the atmosphere,
the graphite is at least one of natural graphite and artificial graphite;
and/or the presence of a gas in the atmosphere,
the silica-based material is at least one of silica-based particles, carbon-coated silica-based particles, polymer-coated silica-based particles, lithium-containing silica-based particles, and magnesium-containing silica-based particles; the chemical formula of the silica-based particles is SiO x Wherein, 0.72<x<1.2。
4. The negative electrode tab of claim 1, wherein:
the negative electrode conductive agent further comprises conductive carbon black;
preferably, the negative electrode membrane further comprises a thickener and a binder;
preferably, the mass ratio of the negative electrode active material, the conductive carbon black, the carbon nanotubes, the thickener, and the binder is (80-97): (1-8): (0.01-0.5): (0.5-5): (1-5);
preferably, the thickener comprises sodium carboxymethyl cellulose; the binder comprises at least one of polyacrylic acid, sodium polyacrylate, polyvinyl alcohol, styrene butadiene rubber, sodium carboxymethyl cellulose, sodium alginate, polymethacrylic acid and carboxymethyl chitosan.
5. The negative electrode tab of claim 1, wherein:
the mass ratio of the graphite to the silica-based material is (0.01-98) to (2-100);
preferably, the mass ratio of the graphite to the silica-based material is (88-92): (8-12).
6. The negative electrode tab of claim 1, wherein:
the negative current collector is a copper foil, a carbon-coated copper foil or a polymer conductive film.
7. A battery comprising the negative electrode sheet according to any one of claims 1 to 6; the lithium ion battery also comprises a shell, a positive pole piece, a separation film and electrolyte; the positive pole piece, the isolating membrane and the negative pole piece are sequentially stacked and wound or laminated to form a bare cell, the bare cell is arranged in the shell, and the electrolyte is contained in the shell.
8. The battery of claim 7, wherein:
the positive pole piece comprises a positive current collector and a positive membrane arranged on at least one side surface of the positive current collector;
preferably, the positive current collector is an aluminum foil, a nickel foil or a polymer conductive film;
preferably, the positive membrane comprises a positive active material, a positive conductive agent and a binder in a mass ratio of (95-98): 1-2;
preferably, the positive active material is at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide, and doping and/or coating modification compounds thereof.
9. The battery of claim 7, wherein:
the electrolyte is at least one of organic liquid electrolyte, solid organic electrolyte, solid ceramic electrolyte and gel electrolyte;
preferably, the electrolyte is an organic liquid electrolyte, and the electrolyte of the organic liquid electrolyte comprises at least one of lithium difluorophosphate, lithium hexafluorophosphate, lithium difluorooxalato phosphate, lithium difluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium tetrafluoroborate and lithium difluorooxalato borate;
preferably, the electrolyte is an organic liquid electrolyte, and a solvent of the organic liquid electrolyte includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, and ethyl propionate;
preferably, the electrolyte is an organic liquid electrolyte, and the additive of the organic liquid electrolyte comprises at least one of vinylene carbonate, vinyl ethylene carbonate, vinyl sulfate, ethylene sulfite, methylene methanedisulfonate, 1, 3-propane sultone, propylene sulfate, trimethylsilyl phosphate, trimethylsilyl borate and fluoroethylene carbonate.
10. The battery of claim 7, wherein:
the isolating membrane is a polyethylene membrane, a polypropylene membrane, a non-woven fabric membrane, or at least one of a composite membrane, a ceramic modified membrane and a PVDF modified membrane thereof.
CN202211138102.0A 2022-09-19 2022-09-19 Negative pole piece and battery Pending CN115312697A (en)

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CN113574698A (en) * 2019-03-08 2021-10-29 株式会社Lg新能源 Negative electrode and secondary battery including the same
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CN103633295A (en) * 2012-08-23 2014-03-12 上海杉杉科技有限公司 Silicon-carbon composite material, lithium ion battery, and preparation method and application of silicon-carbon composite material
CN108878855A (en) * 2018-07-23 2018-11-23 桑德集团有限公司 Silicon-carbon cathode material, silicon-carbon cathode, lithium ion battery and electric vehicle
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