Binder composition and use thereof, negative electrode material, negative electrode sheet, and lithium ion battery

Abstract

The present application relates to the technical field of lithium battery, in particular to a kind of binder composition and its application, negative electrode material, negative electrode sheet and lithium ion battery.The binder composition includes: binder 100 parts by weight;Conductor polymer 0.1-10 parts;Functional polymer 0-20 parts;Conductor polymer is selected from one or more of imine covalent organic framework polymer;Functional polymer is selected from one or more of polymer capable of forming dynamic hydrogen bond with the binder and / or the conductor polymer.The binder composition of the present application is used in silicon-based lithium ion battery, which can maintain the integrity of lithium ion battery negative electrode and SEI film structure, and can improve the electrochemical performance of lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a binder composition and its application, a negative electrode material, a negative electrode sheet, and a lithium-ion battery. Background Technology

[0002] In recent years, as lithium-ion batteries have progressed towards higher energy density, higher safety, and higher stability, the industrial application of positive and negative electrode active materials with high specific capacity has attracted widespread attention. Among these, silicon anodes, with a theoretical specific capacity of 4200 mAh / g compared to the traditional graphite anode's theoretical specific capacity of 370 mAh / g, have been the focus of research. However, silicon-based materials undergo significant volume changes during charge and discharge, leading to damage to the electrode structure and shedding of active materials, thus affecting the battery's cycle life and safety. To address this issue, researchers have performed composite modification on silicon-based materials themselves. For example, anodes prepared by combining silicon with graphite in different ways have already seen initial applications. However, these silicon-carbon anodes have low silicon content, with a reversible specific capacity of only 400-450 mAh / g. To meet the demand for higher energy density, it is necessary to further increase the silicon content of silicon-carbon anodes to achieve a reversible specific capacity of 550-750 mAh / g. In practical applications of high-silicon silicon-carbon anodes, functional modification of binders that can bond active materials, conductive agents, and current collectors together and suppress volume expansion to a certain extent has attracted much attention. Binders not only affect the electrode fabrication process and cost, but also play an important role in the structural stability of the electrode, electron and ion transport, the formation of the solid electrolyte interphase (SEI) film, and the cycle life of the battery.

[0003] Currently, commercial lithium-ion batteries mainly use polyvinylidene fluoride (PVDF), polyimide (PI), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber latex (SBR) as binders. These binders have good chemical stability, bonding effect, and processability, but they also have some disadvantages, such as poor high-temperature resistance, easy swelling in electrolyte, and poor electronic and ionic conductivity.

[0004] Improvements to ion-conducting properties are mainly achieved through the following two methods: (1) adding an electrolyte-absorbing expansion unit; (2) adding electron-rich groups or highly polar groups, utilizing their properties to enhance the ion-conducting properties of Li. + Strong affinity to promote ion transfer. For the first method, although relying on the high ionic conductivity (~10) of the swollen organic electrolyte... -2 S·cm -1 This improves ion transport capability, but excessively high expansion rates may compromise electrode stability. Strongly polar or electron-rich groups, such as ether bonds, sulfonyl groups, and cyano groups, can also negatively impact Li₂. + They have strong interactions.

[0005] Silicon-based anode materials face challenges such as volume expansion, mechanical damage, electrode-electrolyte interface problems, and decreased conductivity. This places certain demands on the binder, which constitutes a significant proportion of the anode slurry. However, commonly used silicon-based anode binders suffer from insufficient mechanical properties, poor conductivity, and poor interface stability. More importantly, and less-discussed, issues are as follows:

[0006] Lithium-ion diffusion limitation: Insufficient ionic conductivity of the binder restricts the diffusion rate of lithium ions within the electrode, as lithium ions need to pass through the binder layer to enter or leave the active material particles. This can lead to an increased lithium-ion concentration gradient within the electrode, affecting the battery's charge / discharge rate and efficiency.

[0007] Degraded cycle performance: If lithium ions cannot pass through the binder layer quickly and effectively during charging and discharging, it may cause uneven volume expansion of the electrode, which in turn leads to fatigue and instability of the electrode structure, thereby reducing the cycle stability and life of the battery.

[0008] Increased interfacial reactions: Insufficient ionic conductivity of the binder may lead to increased interfacial reactions between the electrode and the electrolyte. Especially during electrode charging and discharging, localized electrolyte concentration or dehydration may occur on the electrode surface, resulting in uneven formation of the SEI layer, which in turn affects the cycle stability and safety of the battery.

[0009] Increased wear: Due to the limited diffusion rate of lithium ions inside the electrode, the battery may generate additional heat during charging and discharging, which will exacerbate the damage to the binder layer and thus affect the cycle life and safety of the electrode.

[0010] Power performance degradation: Due to the limited diffusion rate of lithium ions, the electronic conduction and ion transport channels inside the electrodes may be blocked, resulting in a degradation of the battery's power performance. In particular, under high-rate charge and discharge conditions, the battery may not be able to provide sufficient power output. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems of volume expansion, mechanical damage, electrode-electrolyte interface issues, and decreased conductivity faced by existing silicon-based anode materials. This invention provides a binder composition and its application, anode materials, anode sheets, and lithium-ion batteries. This binder composition, used in lithium-ion batteries (e.g., silicon-based lithium-ion anodes), can maintain the integrity of the anode and SEI film structure during charge and discharge processes, thereby improving the rate performance and long-cycle stability of the lithium-ion battery.

[0012] To achieve the above objectives, a first aspect of the present invention provides an adhesive composition comprising, by weight:

[0013] 100 parts adhesive; 0.1-10 parts conductive polymer; 0-20 parts functional polymer;

[0014] The conductor polymer is selected from one or more imine-based covalent organic framework polymers;

[0015] The functional polymer is selected from one or more polymers that can form dynamic hydrogen bonds with the binder and / or the conductor polymer.

[0016] A second aspect of the present invention provides the application of the binder composition of the present invention in a lithium-ion anode binder.

[0017] A third aspect of the present invention provides a negative electrode material comprising a silicon-containing negative electrode active material, a binder, and a conductive material, wherein the binder comprises the binder composition described in the present invention.

[0018] A fourth aspect of the present invention provides a negative electrode sheet, comprising a current collector and a negative electrode material layer disposed on the surface of the current collector, wherein the negative electrode material layer comprises the negative electrode material described in the present invention.

[0019] A fifth aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode comprises the negative electrode sheet described in the present invention.

[0020] Through the above technical solutions, the adhesive composition of the present invention can improve mechanical properties, such as high peel strength, low resistivity, and excellent electrical conductivity.

[0021] The adhesive composition described in this invention, when used as a binder for lithium-ion batteries (e.g., silicon-based negative electrode lithium-ion batteries), can maintain the integrity of the negative electrode and SEI film structure during charge and discharge processes, thereby improving the rate performance and long-cycle stability of the lithium-ion battery. It is speculated that the conductive polymer in the adhesive composition of this invention has a large number of -C=N- active sites, exhibiting both ionic and electronic conductivity. It forms a negative electrode material layer with the silicon-based negative electrode active material, improving electronic conductivity, ion transport efficiency, and inducing the formation of a stable SEI film. This suppresses the volume expansion of the silicon-based negative electrode during charge and discharge processes, mitigates fatigue damage to the binder layer, and maintains the integrity of the negative electrode and SEI film structure during charge and discharge.

[0022] In a preferred embodiment of the present invention, the addition of functional polymers forms a hydrogen bond network between the binder and the conductive polymer, enabling extensive contact with the silicon-based anode active material. This improves electronic conductivity, ion transport efficiency, and induces the formation of a stable SEI film, suppresses the volume expansion of the silicon-based anode during charging and discharging, and slows down fatigue damage to the binder layer. It can maintain the integrity of the anode and SEI film during charging and discharging, further improving the rate performance and long-cycle stability of the lithium-ion battery.

[0023] According to a preferred embodiment of the present invention, the binder composition further contains the nanoparticles described in the present invention. The addition of nano-inorganic particles enhances the stability of the electrode structure, enhances the interfacial stability between the electrode and the electrolyte, and realizes the self-dissipation of stress generated by the expansion of silicon particles, thereby further improving the rate performance and long-cycle stability of the lithium-ion battery. Attached Figure Description

[0024] Figure 1 The graphs show the specific charge capacity and coulombic efficiency of the batteries after 500 cycles for Application Example 2 and Comparative Application Example 1.

[0025] Figure 2 This is the battery rate performance diagram for Application Example 2. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] In this invention, imine covalent organic frameworks (ImineCOFs) polymers are a class of covalent organic framework polymers formed by the condensation of organic amine monomers and aldehyde or ketone monomers according to the Schiff base reaction principle. The main type is an imine bond (C=N) formed by the condensation of amines with aldehydes or ketones. The main chain of imine covalent organic framework polymers contains -C=N- functional groups.

[0028] A first aspect of the present invention provides an adhesive composition comprising, by weight:

[0029] 100 parts adhesive; 0.1-10 parts conductive polymer; 0-20 parts functional polymer;

[0030] The conductor polymer is selected from one or more of the self-chain imine covalent organic framework polymers;

[0031] The functional polymer is selected from one or more polymers capable of forming dynamic hydrogen bonds with the binder and / or the conductor polymer. The binder composition of the present invention, as a binder, can improve mechanical properties, such as high peel strength, low resistivity, and excellent conductivity. It can improve the rate performance and long-cycle stability of lithium-ion batteries, especially silicon-containing anode lithium-ion batteries.

[0032] In this invention, the weight parts of the conductor polymer can be 0.2 parts, 0.5 parts, 0.8 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts. According to a preferred embodiment of this invention, the conductor polymer is 0.1-5 parts, which is beneficial to improve mechanical properties and conductivity.

[0033] In this invention, the functional polymer can be in parts by weight of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20. According to a preferred embodiment of this invention, the functional polymer is in parts of 1-10, which is beneficial for improving mechanical properties and electrical conductivity.

[0034] According to a preferred embodiment of the present invention, the adhesive composition further contains nanoparticles, wherein the nanoparticles are 0.01-1 parts, for example, 0.05 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts or 1 part, which is beneficial to improving mechanical properties and electrical conductivity.

[0035] According to a preferred embodiment of the present invention, the nanoparticles are 0.01-0.5 parts.

[0036] In this invention, nanoparticles refer to material particles with a diameter between 1 and 100 nanometers (nm). According to a preferred embodiment of the invention, the nanoparticles are selected from one or more of barium titanate, nanocellulose, alumina, boron nitride, silicon oxide, zirconium oxide, and titanium dioxide. This is beneficial for improving the rate performance and long-cycle stability of lithium-ion batteries, and can also improve the thermal stability of the battery. The addition of nanoparticles is beneficial for improving the flexibility of the binder, and also helps to dissipate the internal stress caused by the volume expansion of silicon-based active materials.

[0037] According to a preferred embodiment of the present invention, the particle size of the nanoparticles is 1-100 nm, which is beneficial to improving the rate performance and long-cycle stability of lithium-ion batteries, and improving the thermal stability of the batteries.

[0038] According to one embodiment of the present invention, the adhesive composition comprises, by weight: 100 parts of adhesive; and 0.1-10 parts of conductive polymer.

[0039] According to one embodiment of the present invention, the adhesive composition comprises, by weight: 100 parts adhesive; 0.1-10 parts conductive polymer; and 0.01-1 parts nanoparticles.

[0040] According to one embodiment of the present invention, the adhesive composition comprises, by weight: 100 parts adhesive; 0.1-5 parts conductive polymer; and 0.01-0.5 parts nanoparticles.

[0041] In this invention, the binder composition simultaneously contains a conductive polymer and a functional polymer, which can further improve the rate performance and long-cycle stability of lithium-ion batteries. According to a preferred embodiment of the invention, the binder composition comprises, by weight: 100 parts binder; 0.1-5 parts conductive polymer; and 1-10 parts functional polymer.

[0042] In this invention, the binder composition further contains the nanoparticles described in this invention, which can further improve the rate performance and long-cycle stability of lithium-ion batteries, and can also improve the thermal stability of the batteries. According to a preferred embodiment of this invention, the binder composition comprises, by weight: 100 parts binder; 0.1-5 parts conductive polymer; 1-10 parts functional polymer; and 0.01-0.5 parts nanoparticles.

[0043] In this invention, there is no particular limitation on the type of binder in the binder composition. Any binder conventionally used in lithium-ion anodes in the art can be used in this invention to achieve the technical effects of this invention. According to a preferred embodiment of this invention, the binder is selected from one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyacrylonitrile (PAN), carboxymethyl cellulose (CMC), sodium alginate (SA), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), and polyimide (PI).

[0044] According to a preferred embodiment of the present invention, the functional polymer is selected from one or more of polyurea, polyethylene glycol, acrylamide, polyvinylimidazolium, tannic acid, phytic acid and chitosan quaternary ammonium salt, which is beneficial to improving the rate performance and long-cycle stability of lithium-ion batteries.

[0045] In this invention, the monomers used to synthesize the imine-based covalent organic framework polymers include organic amine monomers and aldehyde and ketone monomers. Preferably, the organic amine monomers are selected from one or more of p-3,3'-diaminobenzidine, phenylenediamine, benzyldiamine, tetrastyrenetetramine, tetra(4-aminophenyl)methane, 1,3,5-tris(4-aminophenyl)benzene, and aromatic diaminochiral pyrrolidine. The aldehyde and ketone monomers are selected from one or more of cyclohexanehexanone, 1,3,5-trialdehydebenzene, 1,3,6,8-tetra(4-aldehydephenyl)pyrene, biphenyldialdehyde, terphenyldialdehyde, and terephthalaldehyde.

[0046] For example, the monomers for synthesizing PHATN (polyhexaazanaphthalene) are cyclohexanehexaone and 3,3'-diaminobenzidine.

[0047] For example, the monomers for synthesizing COF-LZU-1 are 1,3,5-trialdehydebenzene and p-phenylenediamine.

[0048] For example, the monomers for synthesizing COF-LZU-72 are 1,3,5-trialdehydebenzene and aromatic diamino chiral pyrrolidine.

[0049] For example, the monomers for synthesizing ILCof-1 are 1,3,6,8-tetra(4-aldehydephenyl)pyrene and p-phenylenediamine.

[0050] For example, the monomers used to synthesize SIOC-COF-1 are tetraphenylethylenetetramine, biphenyl dicarboxaldehyde, and terphenyl dicarboxaldehyde.

[0051] For example, the monomers for synthesizing TAPB-PDA-COF are 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde.

[0052] For example, the monomers used to synthesize COF-300 are tetra(4-aminophenyl)methane and terephthalaldehyde.

[0053] For example, the monomers for synthesizing COF-320 are tetra(4-aminophenyl)methane and biphenyl dicarboxaldehyde.

[0054] For example, the monomers for synthesizing 3d-Py-COF are tetrakis(4-aminophenyl)methane and 1,3,6,8-tetrakis(4-aldehydephenyl)pyrene.

[0055] According to a preferred embodiment of the present invention, the conductor polymer is selected from one or more of PHATN (polyhexaazanaphthalene), COF-LZU-1, COF-LZU-72, ILCOF-1, SIOC-COF-1, TAPB-PDA-COF, COF-300, COF-320 and 3d-Py-COF, which is beneficial to further improve the rate performance and long cycle stability of lithium-ion batteries.

[0056] According to a preferred embodiment of the present invention, the conductor polymer is selected from at least two of PHATN, COF-LZU-1, COF-LZU-72, ILCOF-1, SIOC-COF-1, TAPB-PDA-COF, COF-300, COF-320 and 3d-Py-COF, wherein the content of any one conductor polymer is not less than 20 wt% and not more than 80 wt% of the total mass of the conductor polymer. Using two or more conductor polymers is beneficial to further improve the rate performance and long cycle stability of lithium-ion batteries.

[0057] According to a preferred embodiment of the present invention, the conductive polymer contains at least PHATN, and more preferably, the content of PHATN is 40-60 wt% of the total mass of the conductive polymer.

[0058] In this invention, the conductive polymer is a type of imine covalent organic framework polymer formed by the condensation of organic amine monomers and aldehyde or ketone monomers according to the Schiff base reaction principle. There are no particular limitations on the source and preparation method of the conductive polymer, as long as the conductive polymer can be prepared. This is an illustrative example and does not limit the scope of the invention. This invention provides a method for preparing polyhexaazanaphthalene, comprising:

[0059] (1) Weigh out 5-10 parts of cyclohexanehexaone octahydrate, 5-10 parts of 3,3'-diaminobenzidine, 50-150 parts of N-methylpyrrolidone (NMP), 1-6 parts of concentrated sulfuric acid and 300-500 parts of deionized water.

[0060] (2) Under an argon atmosphere, cyclohexanehexaone octahydrate, 3,3'-diaminobenzidine and NMP were mixed;

[0061] (3) Add a mixture of NMP and concentrated sulfuric acid, stir and heat to react, separate and dry to obtain brown polyhexaazanaphthalene (PHATN)COFs material; preferably, the heating conditions include: temperature of 50-80℃ and time of 5-30h.

[0062] According to a preferred embodiment of the present invention, in step (3), a mixture of NMP and concentrated sulfuric acid is added under an ice bath.

[0063] A second aspect of this invention provides the application of the binder composition described herein in lithium-ion anode binders, preferably in silicon-containing anode binders. The binder composition described herein, when used as a binder for lithium-ion batteries (e.g., silicon-based lithium-ion anodes), can maintain the integrity of the anode and SEI film structure during charge and discharge processes, thereby improving the rate performance and long-cycle stability of the lithium-ion battery.

[0064] A third aspect of the present invention provides a negative electrode material comprising a silicon-containing negative electrode active material, a binder, and a conductive material, wherein the binder comprises the binder composition described in the present invention.

[0065] In this invention, the mass content of the silicon-containing anode active material and the conductive material binder composition can be selected within a wide range. Conventional amounts in the art can achieve the purpose of this invention. According to a preferred embodiment of this invention, by weight, the silicon-containing anode active material in the anode material is 80-100 parts, the binder content is 1-10 parts, and the conductive material content is 1-10 parts.

[0066] The adhesive composition described in this invention is particularly suitable for silicon-based lithium-ion anode binders, which can maintain the integrity of the anode and SEI film of the lithium-ion battery during charge and discharge processes, thereby improving the rate performance and long-cycle stability of the lithium-ion battery. According to a preferred embodiment of the invention, the silicon content in the silicon-containing anode active material is not less than 5 wt%, and preferably not more than 45 wt%.

[0067] According to a preferred embodiment of the present invention, the silicon-containing anode active material is selected from silicon-carbon anode materials.

[0068] According to a preferred embodiment of the present invention, the silicon-carbon anode material contains 15-25 wt% silicon and 75-85 wt% carbon.

[0069] According to a preferred embodiment of the present invention, the specific capacity of the silicon-containing anode active material is 550-750 mAh / g.

[0070] In this invention, there is no particular limitation on the type of conductive material. Conventional conductive materials in the art can be used to achieve the objectives of this invention. According to a preferred embodiment of this invention, the conductive material is selected from one or more carbon-based conductive materials, preferably from one or more of SP (Sup P, Sup C45, Sup C65, KS-6), acetylene black, Ketjen black, graphene, and carbon nanotubes. In this embodiment, Super P (Sup P) material is used as an example, but this does not limit the scope of protection of this invention.

[0071] A fourth aspect of the present invention provides a negative electrode sheet, comprising a current collector and a negative electrode material layer disposed on the surface of the current collector, wherein the negative electrode material layer comprises the negative electrode material described in the present invention.

[0072] A fifth aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode comprises the negative electrode sheet described in the present invention.

[0073] The present invention will be described in detail below through embodiments.

[0074] In the following embodiments, the peel strength parameter was measured using the peel mode of a Model 5943 universal testing machine manufactured by INSTRON Instruments, Inc., USA, at a 180° peel angle. The specific testing method was as follows: the dried electrode sheet was cut into rectangular strips 15mm wide and 80mm long. After fixing the sample on a sample holder, a 13mm wide strip of 3M tape was firmly adhered to the surface of the electrode sheet with the material. Then, the peel strength was measured at 50mm min... -1 The force is slowly peeled off from the electrode at a certain speed, and the pulling force used is collected and recorded.

[0075] The resistivity parameter was obtained using the RST-8 four-probe tester launched by Guangzhou Four-Probe Technology Co., Ltd., China. By applying force, an ohmic connection was created between the probe and the adhesive film to be tested. Then, a small current was applied to the two probes at the two outermost ends using a constant current power supply. The voltage V between the two middle probes was then accurately measured using a voltmeter. Finally, the thin film resistivity of the corresponding sample could be calculated.

[0076] The polyacrylic acid raw material is LA136D, a water-based binder from Sichuan Yindile Technology Co., Ltd.

[0077] The polyimide raw material is Tinctive T126, a water-based binder from Guangzhou Tinci Advanced Materials Co., Ltd.

[0078] Example 1

[0079] (1) Ingredients: 100 parts polyacrylic acid binder, 3 parts chitosan quaternary ammonium salt, 3 parts tannic acid, 1 part polyhexaazanaphthalene, 0.1 parts nano alumina (particle size 80-100nm), 200 parts deionized water;

[0080] (2) Disperse polyhexaazanaphthalene, nano alumina, chitosan quaternary ammonium salt and tannic acid in 100 parts of water to obtain a dispersion, and disperse polyacrylic acid in 100 parts of water to obtain another dispersion; mix the two dispersions, stir for 3 hours, and then pass through a 400-mesh sieve to obtain an emulsion dispersion.

[0081] Example 2

[0082] (1) Ingredients: 100 parts polyacrylic acid binder, 5 parts chitosan quaternary ammonium salt, 5 parts tannic acid, 5 parts polyhexaazanaphthalene, 0.5 parts nano alumina (particle size 80-100nm), 200 parts deionized water;

[0083] (2) Disperse polyhexaazanaphthalene, nano alumina, chitosan quaternary ammonium salt and tannic acid in 100 parts of water to obtain a dispersion, and disperse polyacrylic acid in 100 parts of water to obtain another dispersion; mix the two dispersions, stir for 3 hours, and then pass through a 400-mesh sieve to obtain an emulsion dispersion.

[0084] Example 3

[0085] The method of Example 2 is the same as in Example 2, except that 10 parts of chitosan quaternary ammonium salt, 10 parts of tannic acid, 10 parts of polyhexaazanaphthalene, and 1 part of nano-alumina are used, while the other conditions are the same as in Example 2.

[0086] Example 4

[0087] The method of Example 2 is the same as that of Example 2, except that an equal amount of nano boron nitride (80-100nm) is used instead of nano alumina.

[0088] Example 5

[0089] The method of Example 2 is the same as in Example 2, except that a polyimide adhesive is used instead of a polyacrylic acid adhesive.

[0090] Example 6

[0091] The method of Example 2 is the same as that in Example 2, except that the ingredients are: 100 parts of polyacrylic acid binder, 5 parts of chitosan quaternary ammonium salt, 5 parts of tannic acid, 5 parts of polyhexaazanaphthalene, and 200 parts of deionized water; the other conditions are the same as in Example 2.

[0092] Example 7

[0093] The method of Example 2 is the same as that in Example 2, except that the ingredients are: 100 parts of polyacrylic acid binder, 5 parts of polyhexaazanaphthalene, 0.5 parts of nano alumina (particle size of 80-100nm) dispersion, and 200 parts of deionized water; the other conditions are the same as in Example 2.

[0094] Example 8

[0095] The method of Example 2 is the same as in Example 2, except that the ingredients are: 100 parts of polyacrylic acid binder, 5 parts of polyhexaazanaphthalene, and 200 parts of deionized water; the other conditions are the same as in Example 2.

[0096] Example 9

[0097] The method of Example 2 is followed, except that 2 parts of COF-LZU-1 are used instead of 5 parts of polyhexaazanaphthalene; the other conditions are the same as in Example 2.

[0098] Example 10

[0099] The method of Example 2 is followed, except that 4 parts of COF-320 are used instead of 5 parts of polyhexaazanaphthalene; the other conditions are the same as in Example 2.

[0100] Example 11

[0101] The method of Example 2 is followed, except that 5 parts of ILCof-1 are used instead of 5 parts of polyhexaazanaphthalene; the other conditions are the same as in Example 2.

[0102] Example 12

[0103] The method of Example 2 is followed, except that 3 parts of polyhexaazanaphthalene and 2 parts of COF-LZU-1 are used instead of 5 parts of polyhexaazanaphthalene; the other conditions are the same as in Example 2.

[0104] Comparative Example 1

[0105] The method of Example 7 is followed, except that polyhexaazanaphthalene is not added, while the other conditions are the same as in Example 7.

[0106] Comparative Example 2

[0107] The method of Example 8 is followed, except that polyhexaazanaphthalene is not added, while the other conditions are the same as in Example 8.

[0108] Comparative Example 3

[0109] The method of Example 2 is the same as that in Example 2, except that the ingredients are: 100 parts polyacrylic acid binder, 5 parts chitosan quaternary ammonium salt, 5 parts tannic acid, 0.5 parts nano alumina (particle size of 80-100nm), and 200 parts deionized water; the other conditions are the same as in Example 2.

[0110] Application Example 1

[0111] This application example provides a negative electrode sheet and a lithium-ion battery including the negative electrode sheet. The preparation method of the negative electrode sheet and the lithium-ion battery including the negative electrode sheet is as follows:

[0112] S1. Preparation of the negative electrode:

[0113] The negative electrode active material is a silicon-carbon material of model SL650B1-SC produced by Nanjing Tianmu Pioneer, with silicon and carbon contents of 15% and 85% respectively, and a reversible specific capacity of 650mAh / g.

[0114] The emulsion dispersion was prepared according to the method in Example 1, and diluted with deionized water to a solid content of 4 wt%. 100 parts were weighed, which is 4 parts of the dry weight of the binder.

[0115] Weigh the other components according to the mass ratio of silicon carbide material: Super P: binder dry weight = 93:3:4. Grind the silicon carbide material and Super P evenly, then add them to the binder dilution solution and disperse them to form a uniform slurry. Use a 200μm scraper to evenly coat the slurry onto the copper foil, and dry it in an 80℃ vacuum oven for 8 hours. Then cut the electrode into slices and dry them in an 80℃ vacuum oven for 8 hours. Store them in a glove box for later use.

[0116] S2, Battery Assembly

[0117] The prepared negative electrode was assembled into a CR2025 button cell using a lithium metal sheet as the counter electrode, a polypropylene microporous membrane (Celgard 2500) as the separator, and a 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC (volume ratio 1:1) + FEC 10% (v)) as the electrolyte in an argon-protected glove box. The battery was then sealed at 50 MPa and allowed to stand for 12 hours to obtain the lithium-ion battery.

[0118] Application Examples 2-12 and Comparative Application Examples 1-2 use the same preparation method as Application Example 1, the difference being that the adhesive is replaced with the adhesive provided in Example 2-12 and the adhesive provided in Comparative Examples 1-2, respectively.

[0119] Negative electrode sheets and lithium-ion batteries were prepared according to the methods of Application Examples 1-12 and Comparative Application Examples 1-2, and the following performance tests were performed:

[0120] Conductivity test

[0121] The binders of the above examples and comparative examples were mixed with deionized water to dilute them to a 2% solid content emulsion. 10g of the emulsion was weighed and poured into a polytetrafluoroethylene petri dish with a diameter of 80mm. The petri dish was placed in a constant temperature oven at 100℃ to dry. The prepared film was cut into 5cm×5cm films and then placed between two graphite plates. The resistance at different temperatures was tested by AC impedance using an electrochemical workstation. The conductivity of the film at different temperatures was then calculated by formula (1).

[0122] σ=t / R×S (1)

[0123] Where σ is the proton conductivity (S / cm), t is the thickness of the proton exchange membrane (cm), R is the in-plane resistance perpendicular to the membrane surface (Ω), and S is the effective membrane area (cm²). 2 The conductivity test results are shown in Table 1.

[0124] Mechanical property testing

[0125] The negative electrode sheet was cut into strips of 15mm × 80mm. 3M transparent tape was adhered to one side of the coating layer. A tensile testing machine was used to peel the coating layer in a 180° direction at a speed of 50mm / min, and the peel stress was measured. Peel stress was used as the criterion for judging adhesion performance; the greater the peel stress, the better the adhesion strength of the adhesive. The mechanical property test results are shown in Table 2.

[0126] The prepared battery was subjected to the following electrochemical performance tests using a blue electric field tester:

[0127] Constant current charge-discharge experiment: The test voltage range is 0.005-1.5V, the cycle test current density is 0.5C, and 1C = 1000mAh / g.

[0128] Rate performance: The battery is charged and discharged at currents of 0.1C, 0.5C, 1C, 2C, and 5C, with 10 cycles at each current density, followed by 10 cycles at 0.1C. The charge and discharge voltage range is 0.005-1.5V.

[0129] Cycle stability: After activation and stabilization, the battery was charged and discharged at 0.5C for 150 cycles.Figure 1 The graphs show the charge specific capacity and coulombic efficiency of the batteries after 500 cycles for Application Example 2 and Comparative Application Example 1. Figure 2 The battery rate performance diagram in Application Example 2 illustrates that the technical means of the present invention improves the rate performance and long-cycle stability of lithium-ion batteries.

[0130] The electrochemical test results are shown in Tables 2 and 3. In Table 3, the specific capacity at each rate is the average of the specific capacity after 10 charges; the specific capacity retention rate is the ratio of the average specific capacity of the last 10 0.1C charges to the average specific capacity of the first 10 0.1C charges.

[0131] Table 1

[0132] Example 1 2.85 Example 2 3.61 Example 3 3.48 Example 4 3.40 Example 5 3.53 Example 6 3.29 Example 7 3.17 Example 8 3.21 Example 9 3.53 Example 10 3.60 Example 11 3.50 Example 12 3.60 Comparative Example 1 2.31 Comparative Example 2 2.28 Comparative Example 3 2.52

[0133] Table 2

[0134]

[0135]

[0136] Table 3

[0137]

[0138]

[0139] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A negative electrode material, characterized in that, The negative electrode material contains silicon-containing negative electrode active material, binder composition and conductive material. By weight, the silicon-containing negative electrode active material is 80-100 parts, the binder composition is 1-10 parts and the conductive material is 1-10 parts. The silicon content in the silicon-containing anode active material is not less than 5 wt% and not more than 45 wt%. The adhesive composition includes: 100 parts adhesive, 0.1-10 parts conductive polymer, and 1-20 parts functional polymer; The functional polymers are selected from tannic acid and chitosan quaternary ammonium salt; The conductor polymer is selected from one or more of PHATN, COF-LZU-1, COF-LZU-72, ILCOF-1, SIOC-COF-1, TAPB-PDA-COF, COF-300, COF-320 and 3d-Py-COF; The binder is selected from one or more of polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, sodium alginate, polyamide, and polyimide.

2. The negative electrode material according to claim 1, wherein, The conductor polymer is 0.1-5 parts; and / or The functional polymer is 1-10 parts.

3. The negative electrode material according to claim 1 or 2, wherein, The adhesive composition further contains nanoparticles, in an amount of 0.01-1 part; The nanoparticles are made from one or more of barium titanate, nanocellulose, alumina, boron nitride, silicon oxide, zirconium oxide, and titanium dioxide.

4. The negative electrode material according to claim 3, wherein, The nanoparticles are present in quantities of 0.01-0.5 parts; and / or The nanoparticles have a particle size of 1-100 nm.

5. The negative electrode material according to claim 1, wherein, The silicon-containing anode active material is selected from silicon-carbon anode materials; the silicon content is 15-25 wt% and the carbon content is 75-85 wt%.

6. The negative electrode material according to claim 1, wherein, The specific capacity of the silicon-containing anode active material is 550-750 mAh / g.

7. A negative electrode sheet, comprising a current collector and a negative electrode material layer disposed on the surface of the current collector, characterized in that, The negative electrode material layer comprises the negative electrode material according to any one of claims 1-6.

8. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, characterized in that, The negative electrode comprises the negative electrode sheet as described in claim 7.

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