CN113140699A - Composite negative plate and lithium ion battery comprising same - Google Patents

Composite negative plate and lithium ion battery comprising same Download PDF

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Publication number
CN113140699A
CN113140699A CN202110340693.9A CN202110340693A CN113140699A CN 113140699 A CN113140699 A CN 113140699A CN 202110340693 A CN202110340693 A CN 202110340693A CN 113140699 A CN113140699 A CN 113140699A
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negative electrode
outer layer
composite negative
pole piece
lithium ion
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颜立清
王军华
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Wanxiang A123 Systems Asia Co Ltd
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Wanxiang Group Corp
Wanxiang A123 Systems Asia 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/13—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
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • 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
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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

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  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
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Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a composite negative plate and a lithium ion battery comprising the same; according to the composite negative plate disclosed by the invention, the outer layer uses the negative electrode material with good multiplying power, so that the multiplying power performance of the lithium ion battery can be ensured, the inner layer uses the negative electrode material with high energy density, so that the energy density of the lithium ion battery can be ensured, and on the other hand, the cycle performance can be improved due to the buffering and protecting effects of the outer layer; the lithium ion battery assembled by using the composite negative pole piece can obviously improve the multiplying power and the cycle performance while ensuring high energy density.

Description

Composite negative plate and lithium ion battery comprising same
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a composite negative plate and a lithium ion battery comprising the same.
Background
With the application in the field of high-performance power batteries, the requirements on lithium ion batteries are higher and higher, and particularly, excellent energy density, rate and cycle performance are simultaneously required. However, although the negative electrode materials of lithium batteries have many types and characteristics, they cannot achieve excellent performances in all aspects, and especially it is difficult to achieve both energy density and rate capability. For example, materials such as silicon-based materials and tin-based materials have high capacity, but have poor performance such as efficiency, rate and cycle; the multiplying power and the cyclicity of the lithium titanate are good, but the capacity is low; even with graphite materials commonly used in the market, high energy density and high magnification are directions for different material structures.
There have been some attempts to improve the performance of various cathode materials by making good use of the advantages and disadvantages of the materials or by using other materials. For example, chinese patent publication No. CN104538584A, which is published as 22/4/2015, entitled a multilayer negative electrode sheet, a method for manufacturing a negative electrode sheet, and a lithium ion battery disclose that a multilayer negative electrode sheet is obtained by sequentially coating and drying layer by layer according to an increasing order of expansion coefficients, which is helpful for improving the problem of large expansion coefficient of an alloy negative electrode when used alone, and a part of the alloy negative electrode used is helpful for increasing capacity. However, the material with high coefficient of expansion has high energy density and poor rate or cycle performance. According to the research results of Koffi P.C.Yao and the like, the concentration of lithium ions in the pole piece is distributed in a gradient manner due to polarization, and the multiplying power performance of the battery is more limited by the surface layer of the pole piece. The alloy negative electrode with high expansion coefficient is exposed on the outer layer of the negative plate, so that the rate and the cycle performance which are obviously superior to those of the outermost layer material are difficult to obtain, namely, the excellent rate and cycle performance are difficult to obtain. The Chinese patent publication No. CN108039453A, published as 5.15.2018, discloses a method for improving the cycle performance of a negative electrode of a lithium battery by using a coating, and discloses a method for improving the cycle performance of the negative electrode of the lithium battery by using a mixed coating of an organic silicon fluororesin and a lithium-based compound on the surface of a negative electrode sheet, so that the corrosion of an electrolyte to the negative electrode material is reduced, the volume deformation of the negative electrode material in the cycle process is inhibited, the cycle performance of the lithium battery is improved, but the composite coating does not contribute to the capacity and can not improve the rate capability of the battery.
Disclosure of Invention
In order to solve the technical problems, the invention provides a composite negative plate and a lithium ion battery comprising the same. By using the composite negative pole piece, the lithium ion battery can obviously improve the multiplying power and the cycle performance while ensuring high energy density; in addition, the glassy electrolyte particles are properly doped, so that the coating can be effectively prevented from falling off; meanwhile, the mutual matching between the transmission channel and the lithium ion radius is improved, the porosity is reduced, and the density is improved, so that the lithium ion conductivity is improved, and the energy density is improved.
The specific technical scheme of the invention is as follows: a composite negative plate comprises a negative coating and copper foil; the negative electrode coating comprises two or more layers, wherein the inner layer and the outer layer comprise different active substances, the multiplying power and the cycle performance of the active substance of the outer layer are superior to those of the inner layer, and the energy density of the active substance of the inner layer is superior to that of the outer layer.
The inner layer of the cathode coating is a cathode material layer with high energy density, and the outer layer of the cathode coating is a cathode material layer with good multiplying power and cycle performance; because the concentration of lithium ions in the pole piece is in gradient distribution due to polarization, the multiplying power performance of the battery is more limited by the surface layer of the pole piece, therefore, the multiplying power performance of the lithium ion battery can be ensured by using a negative electrode material with good multiplying power on the outer layer, and the failure caused by premature lithium precipitation or structural damage of the surface layer material is avoided; the inner layer is made of a high-energy-density cathode material, so that the energy density of the lithium ion battery can be ensured; on the other hand, the cycle performance can be improved due to the buffering and protecting effect of the outer layer.
Preferably, glassy electrolyte particles are added to the outer layer; the glassy electrolyte particles are one or more of Li2S-P2S5, Li2S-SiS2 and Li2S-B2S 3.
The glassy electrolyte particles are beneficial to increasing the contact area between the coatings, so that the coatings are bonded more firmly, and crushing and falling off caused by interlayer expansion in the use process of the battery are effectively avoided; meanwhile, the glass ceramics formed after heat treatment are very closely contacted, and the grain boundaries can not be distinguished almost, which shows that the parent glass is softened when the temperature is higher than the glass-transition temperature, and the boundary impedance is reduced, so that the ionic conductivity of the electrolyte is improved.
Preferably, the inner layer comprises the following components in percentage by mass: inner layer negative electrode active material: conductive agent: adhesive: the dispersant is 88.0-98.6: 0.4-4.5: 1.0-4.5: 0.5-3.0; the outer layer comprises the following components in percentage by mass: outer layer negative electrode active material: glassy electrolyte particles: conductive agent: adhesive: the dispersant is 86.0-98.6: 0.5-2.0: 0.4-4.5: 0.5-5.0.
Preferably, the inner-layer negative electrode active material is one or more of graphite, a silicon-based negative electrode material and a tin-based negative electrode material.
Preferably, the outer-layer negative electrode active material is one or more of graphite, soft carbon, hard carbon, lithium titanate and lead telluride.
Preferably, the conductive agent is one or more of graphene, carbon black, carbon nanotubes, carbon fibers and conductive graphite.
Preferably, the binder is one or more of styrene butadiene rubber, polyvinylidene fluoride, polyacrylic acid, sodium alginate, polyurethane, polyvinyl alcohol and polypropylene alcohol.
The selection of the binder in the invention is mainly based on the interfacial compatibility of materials and the elongation of the binder, so that the active substances are ensured not to fall off during the working process of the battery.
Preferably, the dispersant is one or more of sodium carboxymethylcellulose and polyvinylpyrrolidone.
Preferably, the thickness of the outer layer is 2-20 μm.
The outer layer of the lithium ion battery uses the negative electrode material with good multiplying power, the multiplying power performance of the lithium ion battery can be ensured, the thickness of the outer layer is very thin, and the negative electrode material of the outer layer also has certain capacity, so that the influence on the energy density of a battery core is very small; the inner layer is made of a high-energy-density negative electrode material, and the thickness of the inner layer is determined according to the design of the battery cell, so that the energy density of the lithium ion battery can be ensured.
The invention also discloses a lithium ion battery containing the composite negative pole piece, wherein the lithium ion battery consists of a positive pole piece, a negative pole piece, electrolyte and a diaphragm; the negative pole piece is the composite negative pole piece.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the composite negative plate disclosed by the invention, the outer layer uses the negative electrode material with good multiplying power, so that the multiplying power performance of the lithium ion battery can be ensured, the inner layer uses the negative electrode material with high energy density, so that the energy density of the lithium ion battery can be ensured, and on the other hand, the cycle performance can be improved due to the buffering and protecting effects of the outer layer; by using the composite negative pole piece, the lithium ion battery can obviously improve the multiplying power and the cycle performance while ensuring high energy density.
2. The proper doping of the glassy electrolyte particles can effectively avoid the coating from falling off; meanwhile, the mutual matching between the transmission channel and the lithium ion radius is improved, the porosity is reduced, and the density is improved, so that the lithium ion conductivity is improved.
Detailed Description
The present invention will be further described with reference to the following examples. The raw materials and equipment involved in the invention are common raw materials and equipment in the field if not specified; the methods used in the invention are conventional methods in the field if not specified; the reagents used in the invention are all lithium battery grade.
Example 1
(1) Preparing a positive pole piece: 96g of lithium iron phosphate, 0.3g of graphene, 1.5g of carbon black, 0.2g of carbon nano tube, 2g of polyvinylidene fluoride and 65g of N-N-dimethylpyrrolidone, fully stirring and dispersing to form slurry, uniformly coating the slurry on a positive current collector rolled aluminum foil, drying and rolling to prepare the positive pole piece.
(2) Preparing an inner layer of the negative pole piece: 94.5g of artificial graphite, 1.5g of carbon black, 1.5g of sodium carboxymethylcellulose, 2.5g of styrene butadiene rubber and 120g of deionized water, stirring to form slurry, uniformly coating the slurry on the electrolytic copper foil of the negative current collector, drying and rolling.
Outer layer: 93g of soft carbon, 2. 2S-P2S 51 g, 2.5g of carbon black, 2g of sodium carboxymethylcellulose, 2.5g of styrene butadiene rubber and 180g of deionized water are stirred to form slurry, the slurry is uniformly coated on an inner layer pole piece of the negative electrode, the thickness of an outer layer is 5 mu m, and the slurry is dried and rolled to prepare the negative electrode pole piece.
(3) Manufacturing a battery: a microporous PE diaphragm with the thickness of 16 mu m is adopted, 1.1mol of lithium hexafluorophosphate is dissolved in a mixed solvent of dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, an aluminum plastic film with the thickness of 152 mu m is laminated alternately with a positive pole piece, a diaphragm and a negative pole piece in a lamination mode to form a battery core, and then a tab is welded, heat-sealed, injected, formed and split-packaged to prepare the soft package battery.
Example 2
(1) Preparing a positive pole piece: 96g of lithium iron phosphate, 0.3g of graphene, 1.5g of carbon black, 0.2g of carbon nano tube, 2g of polyvinylidene fluoride and 65g of N-N-dimethylpyrrolidone, fully stirring and dispersing to form slurry, uniformly coating the slurry on a positive current collector rolled aluminum foil, drying and rolling to prepare the positive pole piece.
(2) Preparation of negative electrode plate
Inner layer: 88g of artificial graphite, 4.5g of carbon nano tube, 3g of sodium carboxymethylcellulose, 4.5g of polyvinylidene fluoride and 120g of deionized water, stirring to form slurry, uniformly coating the slurry on the electrolytic copper foil of the negative current collector, drying and rolling.
Outer layer: 86g of lithium titanate, 20.5 g of Li 2S-SiS20.5g, 4.5g of graphene, 4.5g of sodium carboxymethylcellulose, 4.5g of polyurethane and 180g of deionized water are stirred to form slurry, the slurry is uniformly coated on an inner layer of a negative electrode plate, the thickness of an outer layer is2 mu m, and the outer layer is dried and rolled to prepare the negative electrode plate.
(3) Manufacturing a battery: a microporous PE diaphragm with the thickness of 16 mu m is adopted, 1.1mol of lithium hexafluorophosphate is dissolved in a mixed solvent of dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, an aluminum plastic film with the thickness of 152 mu m is laminated alternately with a positive pole piece, a diaphragm and a negative pole piece in a lamination mode to form a battery core, and then a tab is welded, heat-sealed, injected, formed and split-packaged to prepare the soft package battery.
Example 3
(1) Preparing a positive pole piece: 96g of lithium iron phosphate, 0.3g of graphene, 1.5g of carbon black, 0.2g of carbon nano tube, 2g of polyvinylidene fluoride and 65g of N-N-dimethylpyrrolidone, fully stirring and dispersing to form slurry, uniformly coating the slurry on a positive current collector rolled aluminum foil, drying and rolling to prepare the positive pole piece.
(2) Preparing an inner layer of the negative pole piece: 98.6g of artificial graphite, 0.4g of carbon fiber, 0.5g of polyvinylpyrrolidone, 0.5g of polyacrylic acid and 120g of deionized water are stirred to form slurry, the slurry is uniformly coated on the electrolytic copper foil of the negative current collector, and the electrolytic copper foil is dried and rolled.
Outer layer: 98.6g of lead telluride, 0.4g of conductive graphite, 0.5g of polyvinylpyrrolidone, 0.5g of sodium alginate and 180g of deionized water are stirred to form slurry, the slurry is uniformly coated on an inner layer pole piece of the negative pole, the thickness of an outer layer is 20 mu m, and the negative pole piece is prepared by drying, rolling and pressing.
(3) Manufacturing a battery: a microporous PE diaphragm with the thickness of 16 mu m is adopted, 1.1mol of lithium hexafluorophosphate is dissolved in a mixed solvent of dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, an aluminum plastic film with the thickness of 152 mu m is laminated alternately with a positive pole piece, a diaphragm and a negative pole piece in a lamination mode to form a battery core, and then a tab is welded, heat-sealed, injected, formed and split-packaged to prepare the soft package battery.
Example 4
(1) Preparing a positive pole piece: 96g of lithium iron phosphate, 0.3g of graphene, 1.5g of carbon black, 0.2g of carbon nano tube, 2g of polyvinylidene fluoride and 65g of N-N-dimethylpyrrolidone, fully stirring and dispersing to form slurry, uniformly coating the slurry on a positive current collector rolled aluminum foil, drying and rolling to prepare the positive pole piece.
(2) Preparation of negative electrode plate
Inner layer: 94.5g of artificial graphite, 1.5g of carbon black, 1.5g of sodium carboxymethylcellulose, 2.5g of polyvinyl alcohol and 120g of deionized water, stirring to form slurry, uniformly coating the slurry on the electrolytic copper foil of the negative current collector, drying and rolling.
Outer layer: 93g of soft carbon, 2.5g of carbon black, Li2S-B2S 32 g, 2g of sodium carboxymethylcellulose, 2.5g of polypropylene glycol and 180g of deionized water are stirred to form slurry, the slurry is uniformly coated on an inner layer pole piece of the negative electrode, the thickness of an outer layer is 5 mu m, and the outer layer is dried and rolled to prepare the negative electrode pole piece.
(3) Manufacturing a battery: a microporous PE diaphragm with the thickness of 16 mu m is adopted, 1.1mol of lithium hexafluorophosphate is dissolved in a mixed solvent of dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, an aluminum plastic film with the thickness of 152 mu m is laminated alternately with a positive pole piece, a diaphragm and a negative pole piece in a lamination mode to form a battery core, and then a tab is welded, heat-sealed, injected, formed and split-packaged to prepare the soft package battery.
Comparative example 1
The comparative example differs from example 1 in that: the cathode plate has no outer layer but only an inner artificial graphite layer. The remaining raw materials and processes were the same as in example 1.
Comparative example 2
The comparative example differs from example 2 in that: the cathode plate has no outer layer but only an inner artificial graphite layer. The remaining raw materials and processes were the same as in example 2.
Comparative example 3
The comparative example differs from example 3 in that: the cathode plate has no outer layer but only an inner artificial graphite layer. The remaining raw materials and processes were the same as in example 3.
Comparative example 4
The comparative example differs from example 4 in that: the cathode plate has no outer layer but only an inner artificial graphite layer. The remaining raw materials and processes were the same as in example 4.
Comparative example 5
Comparative example 5 differs from example 1 in that: the glassy electrolyte particles were not added to the outer layer and the remaining raw materials and processes were the same as in example 1.
Comparative example 6
Comparative example 6 differs from example 1 in that: the outer layer is made of high-energy density material, the inner layer is made of high-rate material, and the rest of raw materials and processes are the same as those in example 1.
The results of testing the batteries manufactured in the above examples are shown in table 1.
TABLE 1 Soft-package battery electric performance test results
Figure BDA0002999469850000061
As can be seen from table 1, in examples 1 to 4, compared with comparative examples 1 to 4, respectively, it is shown that the negative electrode material prepared by the negative electrode material layer with high energy density on the inner layer and high rate and cycle performance on the outer layer shows better rate and cycle performance; example 1 compared to comparative example 5, illustrates that the addition of glassy electrolyte particles is more beneficial for improving cycling performance; compared with the comparative example 6, the embodiment 1 shows that the outer layer is made of the high-energy density material, and the negative electrode material with the inner layer made of the high-rate material has no beneficial effect on the improvement of the rate and the cycle performance, and further proves that the rate performance of the battery is more limited by the surface layer of the pole piece, so that the negative electrode material with good rate is used in the outer layer, the rate performance of the lithium ion battery can be ensured, and the failure caused by premature lithium precipitation or structural damage of the surface layer material can be avoided.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (10)

1. A composite negative plate comprises a negative coating and copper foil; the negative electrode coating is characterized by comprising two or more layers, wherein the inner layer and the outer layer comprise different active substances, the multiplying power and the cycle performance of the active substance of the outer layer are superior to those of the inner layer, and the energy density of the active substance of the inner layer is superior to that of the outer layer.
2. The composite negative electrode sheet of claim 1, wherein said outer layer contains glassy electrolyte particles; the glassy electrolyte particles are one or more of Li2S-P2S5, Li2S-SiS2 and Li2S-B2S 3.
3. The composite negative electrode sheet according to claim 1, wherein the inner layer comprises the following components in percentage by mass: inner layer negative electrode active material: conductive agent: adhesive: the dispersant is 88.0-98.6: 0.4-4.5: 1.0-4.5: 0.5-3.0; the outer layer comprises the following components in percentage by mass: outer layer negative electrode active material: glassy electrolyte particles: conductive agent: adhesive: the dispersant is 86.0-98.6: 0.5-2.0: 0.4-4.5: 0.5-5.0.
4. The composite negative electrode sheet according to claim 3, wherein the inner negative active material is one or more of graphite, a silicon-based negative electrode material, and a tin-based negative electrode material.
5. The composite negative electrode sheet according to claim 3, wherein the outer negative active material is one or more of graphite, soft carbon, hard carbon, lithium titanate, and lead telluride.
6. The composite negative electrode sheet according to claim 3, wherein the conductive agent is one or more of graphene, carbon black, carbon nanotubes, carbon fibers, and conductive graphite.
7. The composite negative electrode sheet according to claim 3, wherein the binder is one or more of styrene-butadiene rubber, polyvinylidene fluoride, polyacrylic acid, sodium alginate, polyurethane, polyvinyl alcohol and polypropylene alcohol.
8. The composite negative electrode sheet according to claim 3, wherein the dispersant is one or more of sodium carboxymethylcellulose and polyvinylpyrrolidone.
9. The composite negative electrode sheet according to claim 1, wherein the outer layer has a thickness of 2 to 20 μm.
10. A lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, and is characterized in that the negative pole piece is the composite negative pole piece of any one of claims 1 to 9.
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