Composition for battery negative electrode slurry, battery negative electrode material, preparation method of battery negative electrode material and solid-state lithium battery

Abstract

The invention relates to the field of solid-state batteries, and discloses a composition for negative electrode slurry, a negative electrode material, a preparation method of the negative electrode material and a solid-state lithium battery. The composition contains a component A and an organic solvent B, the component A contains a copolymer component, a lithium salt, a solid electrolyte and conductive carbon; the copolymer component contains a first polymer, a second polymer and a third polymer in a mass content ratio of 1: (0.05-3): (0.2-5); the weight-average molecular weight of the first polymer is 300,000-600,000 Da; the weight-average molecular weight of the second polymer is 5,000-50,000 Da; the weight-average molecular weight of the third polymer is 60 thousand to 25 thousand Da; the solid electrolyte comprises sulfide solid electrolyte and / or oxide solid electrolyte. The negative electrode material disclosed by the invention has the advantages of low interface resistance, high ionic conductivity and good cycling stability.

Description

Technical Field

[0001] The present invention relates to a solid-state battery, and in particular to a composition for a battery negative electrode slurry, a battery negative electrode material and a preparation method thereof, and a solid-state lithium battery. Background Art

[0002] Lithium metal is widely considered the most promising anode material for lithium batteries due to its ultra-high theoretical capacity and extremely low electrochemical potential. Furthermore, with the deepening of research into all-solid-state batteries, which use solid electrolytes instead of liquid electrolytes to address safety concerns, the energy density advantages of lithium metal batteries based on sulfide all-solid-state systems have become even more apparent.

[0003] However, the application of lithium metal anodes still faces significant challenges. Lithium metal is highly reducible and reacts with sulfide solid electrolytes (SSEs) to directly form a solid electrolyte interphase (SEI) with low ionic conductivity. This fragile SEI undergoes significant volume changes as lithium metal is continuously inserted and removed. This constantly breaks down and forms new layers, exacerbating the consumption of active lithium and electrolyte, and shortening the battery's lifespan.

[0004] At present, almost all the problems faced by metal lithium negative electrodes are basically caused by the instability of the interface between metal lithium and electrolyte. How to rationally design and construct an effective interface layer to form a composite metal lithium negative electrode is the key to realizing sulfide-based all-solid-state metal lithium batteries.

[0005] Currently, the artificial interface layer of composite metal lithium anodes is mostly constructed using methods such as chemical vapor deposition (CVD) and atomic layer deposition (ALD). The interface layer can reach the nanometer level and is controllable, but the process is complex and costly. The use of traditional processes (such as gravure coating, knife-roll coating, metering rod coating, slot die coating, etc.) to apply the ion-conducting and electron-conducting buffer layer has the problem of low ionic conductivity (<1mS / cm) of the metal lithium anode and incompatibility between the buffer layer and the electrolyte layer, resulting in interfacial impedance of the battery anode material and poor battery cycling performance.

[0006] For example, the technical solutions disclosed in CN115732783A and CN113363570A introduce an artificial solid electrolyte interface layer on the surface of the metallic lithium negative electrode by means of magnetron sputtering, plasma-enhanced chemical vapor deposition, etc., thereby controlling the thickness of the artificial interface layer. However, the technology is costly, inefficient, and difficult to industrialize.

[0007] For example, the technical solution disclosed in CN115207483A uses electron-conducting carbon materials and ion-conducting lithium nitride to form a dual-conducting negative electrode interface modification layer that conducts ions and electrons. However, the usage scenarios of the lithium nitride material itself are more stringent than those of sulfide electrolytes. It generates lithium hydroxide and ammonia when it comes into contact with water, and there are also problems with its compatibility with sulfide electrolytes.

[0008] Therefore, there is an urgent need to develop a stable, low-cost composite metal lithium anode that matches SSE. Summary of the Invention

[0009] The purpose of the present invention is to solve the problems of high interface resistance, low ion conductivity and poor cycle stability of battery negative electrode materials.

[0010] In order to achieve the above object, the first aspect of the present invention provides a composition for battery negative electrode slurry, which comprises component A and organic solvent B; the component A comprises a copolymer component, a lithium salt, a solid electrolyte and conductive carbon;

[0011] The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da;

[0012] The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate;

[0013] The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

[0014] A second aspect of the present invention provides a method for preparing a battery negative electrode material, which is performed using the battery negative electrode slurry composition described in the first aspect, and comprises:

[0015] (1) contacting and mixing the components in the composition to obtain a protective layer slurry;

[0016] (2) coating the protective layer slurry on lithium foil and performing heat treatment to obtain a battery negative electrode material;

[0017] The composition contains component A and organic solvent B; component A contains copolymer component, lithium salt, solid electrolyte and conductive carbon;

[0018] The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da;

[0019] The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate;

[0020] The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

[0021] The third aspect of the present invention provides a battery negative electrode material prepared by the method described in the second aspect.

[0022] The fourth aspect of the present invention provides a solid-state lithium battery, which contains a positive electrode material, a solid electrolyte and a negative electrode material; the negative electrode material is the battery negative electrode material described in the third aspect.

[0023] The present invention has at least the following advantages:

[0024] (1) The battery negative electrode material of the present invention has the advantage of low interfacial impedance and can effectively solve the problem of incompatibility between the electrolyte and the interfacial buffer layer;

[0025] (2) The battery negative electrode material of the present invention can effectively inhibit the growth of lithium dendrites, has excellent ionic conductivity, and can significantly improve the cycle stability and cycle life of solid-state batteries. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] As mentioned above, the first aspect of the present invention provides a composition for battery negative electrode slurry, which comprises component A and organic solvent B; component A comprises a copolymer component, a lithium salt, a solid electrolyte and conductive carbon;

[0028] The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da;

[0029] The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate;

[0030] The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

[0031] In the technical solution of the present invention, three different types of polymers are synergistically coordinated with solid electrolytes, conductive carbon, lithium salts and specific organic solvents to construct a negative electrode material containing a low interfacial impedance layer; the negative electrode material of the present invention has excellent interface stability, avoiding the increase in interface impedance caused by side reactions between the electrolyte and metallic lithium in the battery, and effectively avoiding the growth of lithium dendrites; in addition, in the present invention, through the design of materials and formulas, the ionic conductivity of the negative electrode material can be effectively improved, and when the negative electrode material is applied to solid-state batteries, it can significantly improve the cycle stability and cycle life of the solid-state battery.

[0032] Preferably, the mass content ratio of the first polymer, the second polymer and the third polymer is 1:0.1-0.5:0.2-2.

[0033] Preferably, based on the total mass of component A, the copolymer component comprises 3.5-18 wt %, the lithium salt comprises 0.5-5 wt %, the conductive carbon comprises 0.5-3 wt %, and the solid electrolyte comprises 74-95.5 wt %. The inventors of the present invention have discovered that under these preferred conditions, the prepared negative electrode material exhibits superior interfacial impedance, significantly improving the cycle stability and cycle life of solid-state batteries.

[0034] Preferably, in the composition, the content of component A is 13-70 wt%.

[0035] Preferably, the first polymer is at least one selected from polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate and polyacrylonitrile.

[0036] Further preferably, the second polymer is selected from at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, poly(p-phenylene vinylene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate).

[0037] More preferably, the third polymer is at least one selected from styrene-butadiene rubber, nitrile rubber, styrene-ethylene-butylene-styrene copolymer and styrene-butadiene-styrene copolymer.

[0038] Preferably, the organic solvent B is selected from n-hexane, n-pentane, isopentane, n-heptane, n-octane, isooctane, trichlorotrifluoroethane, dichloromethane, chloroform, 2-methylpentane, 2,2-dimethylpentane, 3-methylpentane, 2,3-dimethylpentane, 2-methylhexane, 2,2-dimethylhexane, 3-methylhexane, 2,3-dimethylhexane, 3-ethylhexane, cyclohexane, cycloheptane, methylcyclohexane, tert-butylcyclohexane, tetrahydrofuran, benzene, toluene, 1 , at least one of 2-xylene, 1,3-xylene, 1,4-xylene, chlorobenzene, o-dichlorobenzene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, ethylene dichloride, cyclopentene, cyclohexene, 1-methylcyclohexene, 4-methylcyclohexene, 1-ethylcyclohexene, 1,4-dimethylcyclohexene, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate.

[0039] According to a preferred embodiment, the sulfide solid electrolyte is an argyrodite-type sulfide solid electrolyte and / or a low-temperature phase sulfide solid electrolyte;

[0040] The low-temperature phase sulfide solid electrolyte has a chemical formula as shown in Formula 1;

[0041] Li7P2S8A x B 1-x , formula 1;

[0042] Among them, 0≤x≤1, A and B are the same or different, and each independently selects any one of F, Cl, Br, and I. The inventors of the present invention found that by using the sulfide solid electrolyte defined in this application, the prepared battery anode material has more excellent stability.

[0043] Further preferably, the argyrodite-type sulfide solid electrolyte has a chemical formula as shown in Formula 2;

[0044] wLi2S·(100-w-u)L c S d ·uM, Formula 2;

[0045] 0<w<100; c is 0, 1 or 2; d is 2c or 2c + 1; 0≤u<100-w;

[0046] L selects any one of B, Si, P, and Ge, and M selects any one of LiCl, LiBr, LiI, Li3PO4, GeS2, P2O5, Li4SiO4, and P2S3.

[0047] Preferably, the lithium salt is selected from at least one of lithium nitrate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(catecholato)borate, lithium bis(2,3-naphthalenediolato)borate, lithium bis(2,2-biphenyldioxolato)borate, lithium di(salicylato)borate, lithium di(2,3-pyridinedioxolato)borate, lithium bisborate, and lithium bis(malonato)borate.

[0048] Preferably, the conductive carbon is selected from at least one of carbon black, carbon nanotubes, acetylene black, vapor-grown carbon fibers, and graphene.

[0049] As described above, the second aspect of the present invention provides a method for preparing a battery anode material. This method is carried out using the battery anode paste composition described in the first aspect. This method includes:

[0050] (1) Contact and mix each component in the composition to obtain a protective layer paste;

[0051] (2) Coat the protective layer paste on a lithium foil and perform heat treatment to obtain a battery anode material;

[0052] The composition contains component A and organic solvent B; component A contains a copolymer component, a lithium salt, a solid electrolyte, and conductive carbon;

[0053] The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da;

[0054] The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate;

[0055] The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

[0056] It should be noted that the types and dosages of the substances involved in the second aspect of the present invention are the same as the types and contents involved in the composition of the first aspect. In order to avoid redundancy, the present invention is not repeated in the second aspect, and those skilled in the art should not understand it as a limitation of the present invention.

[0057] Preferably, the composition further comprises organic solvent 1 and organic solvent 2;

[0058] The contact mixing operation in step (1) includes:

[0059] Mixing a solution 1 containing the organic solvent 1, the first polymer and the lithium salt, a solution 2 containing the organic solvent 2, the second polymer and the conductive carbon, and a solution 3 containing the organic solvent B, the third polymer and the solid electrolyte to obtain the protective layer slurry;

[0060] The organic solvent 1 and the organic solvent 2 are the same or different, and are each independently selected from at least one of acetonitrile, dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethyl sulfoxide, triethyl phosphate, trimethyl phosphate, ε-caprolactone and 1,4-butyrolactone.

[0061] In the present invention, by adopting a step-by-step contact mixing method, the function of each component can be fully exerted, while avoiding the problem of side reactions of part of the electrolyte caused by one-step mixing.

[0062] According to a preferred embodiment, in step (1), the contact mixing conditions include: temperature of 20-60° C. and time of 1-24 h.

[0063] According to a particularly preferred embodiment, the contact mixing operation includes:

[0064] (1) mixing the first polymer and the lithium salt in the organic solvent 1 to obtain the solution 1;

[0065] In the organic solvent 2, the second polymer and the conductive carbon are mixed for a second time to obtain the solution 2;

[0066] In the organic solvent B, the third polymer and the solid electrolyte are mixed for a third time to obtain the solution 3;

[0067] (2) The solution 1, the solution 2, and the solution 3 are mixed for the fourth time to obtain the protective layer slurry.

[0068] Preferably, the temperatures of the first mixing, the second mixing, the third mixing and the fourth mixing are each independently selected from 20-60° C., and the total mixing time is 1-24 h.

[0069] More preferably, the stirring speeds of the first mixing, the second mixing, the third mixing and the fourth mixing are each independently selected from 50-500 rpm.

[0070] Preferably, in step (2), the heat treatment conditions include: temperature of 40-120° C., and time of 1-24 h.

[0071] According to a preferred embodiment, the operation of “coating the protective layer slurry on the lithium foil and performing heat treatment” includes:

[0072] (1) coating the protective layer slurry on a substrate and performing a first heat treatment to obtain a protective layer tape;

[0073] (2) Laminating the protective layer slurry surface in the protective layer tape onto a metal lithium foil material, performing a second heat treatment, and then removing the substrate to obtain the battery negative electrode material.

[0074] Preferably, the conditions of the first heat treatment include: temperature of 40-70° C. and time of 1-12 h.

[0075] Preferably, the conditions of the second heat treatment include: temperature of 60-120° C., and time of 5-60 min.

[0076] Further preferably, the substrate is selected from at least one of polyethylene terephthalate film, polyester release film, polyimide film, aluminum foil and stainless steel foil.

[0077] More preferably, the coating method is selected from at least one of gravure coating, knife roll coating, metering rod coating and slot die coating.

[0078] Preferably, the thickness of the protective layer is 1-20 μm.

[0079] As mentioned above, the third aspect of the present invention provides a battery negative electrode material prepared by the method described in the second aspect.

[0080] As mentioned above, the fourth aspect of the present invention provides a solid-state lithium battery, which contains a positive electrode material, a solid electrolyte and a negative electrode material; the negative electrode material is the battery negative electrode material described in the third aspect.

[0081] Preferably, the positive electrode material is selected from LiCoO2, LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.83 Co 0.12 Mn 0.05 O、LiNi 0.92 Co 0.06 Mn 0.02 At least one of O.

[0082] In the following examples, unless otherwise specified, the raw materials are all common commercially available products.

[0083] First polymer

[0084] Polyethylene oxide 1: weight average molecular weight 500,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0085] Polyvinylidene fluoride: weight average molecular weight 534,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0086] Polyethylene oxide 2: weight average molecular weight 200,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0087] Second polymer

[0088] Polypyrrole (PPy) with a weight-average molecular weight of 50,000 Da was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0089] Polyacetylene: weight average molecular weight 20,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0090] Polyaniline (PAI) with a weight-average molecular weight of 15,000 Da was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0091] Poly(p-phenylene vinylene): weight average molecular weight 20,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0092] Polythiophene: weight average molecular weight 25,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0093] Polyacene: weight average molecular weight 20,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0094] The third polymer

[0095] Styrene-ethylene-butylene-styrene copolymer: weight average molecular weight 60,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0096] Styrene-butadiene-styrene copolymer (SBST) with a weight-average molecular weight of 80,000 Da was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0097] Nitrile butadiene rubber (NBR) with a weight-average molecular weight of 100,000 Da was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0098] Styrene-butadiene rubber: weight-average molecular weight 100,000 Da, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0099] Conductive carbon

[0100] Vapor-grown carbon fiber: purity: 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0101] Multi-walled carbon nanotubes: purity: 95%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0102] solid electrolyte

[0103] S1:Li7P2S8I

[0104] S2:Li7P2S8Br 0.5 I 0.5

[0105] S3:Li7P2S8Cl 0.2 I 0.8

[0106] S4:Li7P2S8F 0.1 I 0.9

[0107] S5:Li6PS5Cl

[0108] S6:Li3PS4.

[0109] Lithium lanthanum zirconium tantalum oxide: Li 6.5 La3Zr 1.5 Ta 0.5 O 12 (LLZTO)

[0110] Example 1

[0111] (1) In an organic solvent 1, a first polymer and a lithium salt are first mixed in a planetary ball mill at 25° C. to obtain a solution 1;

[0112] In organic solvent 2, a second polymer and conductive carbon are mixed in a planetary ball mill at 25° C. to obtain solution 2;

[0113] In organic solvent B, a third polymer and a sulfide solid electrolyte are mixed in a planetary ball mill at 25° C. to obtain solution 3;

[0114] (2) placing solution 1, solution 2, and solution 3 in a degassing machine and performing a fourth mixing at 30° C. to obtain a protective layer slurry;

[0115] (3) The protective layer slurry is coated on the substrate by a metering rod coating method, and a first heat treatment is performed to obtain a substrate containing a protective layer strip with a thickness of 3 μm; then the protective layer strip surface is attached to a metal lithium foil material, and a second heat treatment is performed and the substrate is removed to obtain a negative electrode material.

[0116] The specific raw material types and process parameters are shown in Table 1.

[0117] Example 2-Example 5

[0118] The same process as in Example 1 was adopted, except that the types of raw materials and process parameters were different, to obtain the negative electrode material; the details are shown in Table 1.

[0119] Example 6

[0120] The same process as in Example 1 was adopted, except that S1 was replaced by an oxide electrolyte of lithium lanthanum zirconium tantalum oxide (LLZTO) in an equal amount by mass, and the rest remained unchanged to prepare a negative electrode material.

[0121] Example 7

[0122] The same process as in Example 1 was adopted, except that S1 was replaced with an equal amount of aluminum oxide Al2O3, and the rest remained unchanged, to prepare a negative electrode material.

[0123] Example 8

[0124] The same process as in Example 1 was adopted, except that S1 was replaced by Li3PS4 in an equal amount by mass, and the rest remained unchanged to prepare the negative electrode material.

[0125] Example 9

[0126] The same process as Example 2 was adopted, except that different amounts of raw material components were used while other factors remained unchanged to prepare negative electrode materials, as shown in Table 1.

[0127] Example 10

[0128] The same process as in Example 3 was adopted, except that different amounts of raw material components were used while other factors remained unchanged to prepare negative electrode materials, as shown in Table 1.

[0129] Example 11

[0130] In an organic solvent, 8 g of polyethylene oxide 1 (first polymer), 1 g of polypyrrole (second polymer), 2 g of styrene-ethylene-butylene-styrene copolymer (third polymer), 3 g of lithium difluorooxalatoborate (lithium salt), 2 g of carbon nanotubes (conductive carbon) and 84 g of S1 (sulfide solid electrolyte) were mixed at 30 ° C and 200 rpm for 7.5 h to obtain a protective layer slurry;

[0131] The protective layer slurry is coated on a polyethylene terephthalate film (substrate) by knife-roll coating, and a first heat treatment is performed to obtain a substrate containing a 3 μm thick protective layer strip. The protective layer strip surface is then attached to a metal lithium foil, and a second heat treatment is performed before the substrate is removed to obtain a negative electrode material.

[0132] The conditions for the first heat treatment are: temperature 50°C, time 4h; the conditions for the second heat treatment are: temperature 80°C, time 30min;

[0133] The organic solvent consisted of 233 g of acetonitrile and 100 g of 1,4-dimethylbenzene.

[0134] Example 12

[0135] The same process as in Example 1 was adopted, except that polypyrrole (the second polymer) was replaced by polyacene of equal mass, and the rest remained unchanged, to prepare a negative electrode material.

[0136] Comparative Example 1

[0137] The same process as in Example 1 was adopted, except that different amounts of raw material components were used while other components remained unchanged to prepare negative electrode materials, as shown in Table 1.

[0138] Comparative Example 2

[0139] The same process as in Example 1 was adopted, except that polyethylene oxide 1 was replaced by polyethylene oxide 2 of equal mass, and the rest remained unchanged, to prepare a negative electrode material.

[0140] Comparative Example 3

[0141] The same process as in Example 1 was adopted, except that the types of organic solvent 1, organic solvent 2, and organic solvent B were different, and the rest remained unchanged to prepare the negative electrode material, as shown in Table 1.

[0142] Table 1

[0143]

[0144]

[0145] Table 1

[0146]

[0147]

[0148] Application Examples

[0149] A solid electrolyte:

[0150] (1) Positive electrode preparation: LiNi 0.8 Co 0.1 Mn 0.1 O2 and Li6PS5Cl (sulfide electrolyte) were ground and mixed for 20 minutes in a mass ratio of 70:30 (total amount of 1 g) to obtain a positive electrode material;

[0151] (2) 0.1 g of Li6PS5Cl (sulfide electrolyte) was compacted at 300 MPa, 21 mg of positive electrode material was placed on one side, and after vibration, a steel sheet was laid flat on it and compacted at 300 MPa; the negative electrode materials prepared in the embodiment and comparative example were placed on the other side respectively and compacted at 2 MPa; a solid-state battery was obtained.

[0152] Test example:

[0153] An all-solid-state battery mold was used for testing: the test temperature was 60°C, and the battery was first charged to 4.4V at a constant current of 0.1C, then charged at a constant voltage until the current dropped to 0.05C, and then allowed to stand for 20 minutes. The battery was then discharged to 2V at a current of 0.1C and allowed to stand for 20 minutes to complete a cycle. This cycle was repeated for one round, and then a charge and discharge cycle test was performed at a current of 0.33C. The specific test results are shown in Table 2.

[0154] Table 2

[0155]

[0156] From the above content, it can be seen that the negative electrode material obtained by the preparation method of the present invention is applied to all-solid-state batteries, and the battery has better cycle performance; Li7P2S8A x B 1-x Low-temperature phase sulfide solid electrolytes are more stable to metallic lithium than argyrodite-type electrolytes, so the cycle performance of Examples 1-4 is better than that of Example 5. In Examples 6-8, changing the type of solid electrolyte also has a certain impact on the cycle performance of the battery. In Examples 9-10 and Example 12, by setting different raw material formulas, excessive solid electrolyte content or excessive polymer content has a certain degree of impact on the battery cycle performance. As shown in Example 11, different preparation processes also have a certain impact on the cycle performance of the battery. As shown in Comparative Examples 1-3, if the negative electrode material is prepared using raw materials and methods that do not conform to the technical solution of the present invention, the ionic conductivity and cycle stability will be significantly deteriorated when used in a solid electrolyte.

[0157] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composition for battery negative electrode slurry, characterized in that: The composition contains component A and organic solvent B; the component A contains copolymer components, lithium salt, solid electrolyte and conductive carbon; The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da; The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate; The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

2. The composition according to claim 1, characterized in that Based on the total mass of component A, the content of the copolymer component is 3.5-18wt%, the content of the lithium salt is 0.5-5wt%, the content of the conductive carbon is 0.5-3wt%, and the content of the solid electrolyte is 74-95.5wt%.

3. The composition according to claim 1 or 2, characterized in that In the composition, the content of component A is 13-70 wt%.

4. The composition according to claim 1 or 2, characterized in that The first polymer is selected from at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate and polyacrylonitrile; and / or, the second polymer is selected from at least one of polypyrrole, polyaniline, polythiophene, polyacetylene, poly(p-phenylene vinylene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate); And / or, the third polymer is at least one selected from styrene-butadiene rubber, nitrile rubber, styrene-ethylene-butylene-styrene copolymer and styrene-butadiene-styrene copolymer.

5. The composition according to claim 1 or 2, characterized in that The sulfide solid electrolyte is an argyrodite-type sulfide solid electrolyte and / or a low-temperature phase sulfide solid electrolyte; The low-temperature phase sulfide solid electrolyte has a chemical formula as shown in Formula 1; Li7P2S8A x B 1-x , formula 1; Wherein, 0≤x≤1, A and B are the same or different, and are independently selected from any one of F, Cl, Br and I.

6. A method for preparing a negative electrode material for a battery, characterized in that: The method is carried out using the battery negative electrode slurry composition according to any one of claims 1 to 5, and the method comprises: (1) contacting and mixing the components in the composition to obtain a protective layer slurry; (2) coating the protective layer slurry on lithium foil and performing heat treatment to obtain a battery negative electrode material; The composition contains component A and organic solvent B; component A contains copolymer component, lithium salt, solid electrolyte and conductive carbon; The copolymer component contains a first polymer, a second polymer, and a third polymer in a mass ratio of 1:0.05-3:0.2-5; the weight average molecular weight of the first polymer is 300,000-600,000 Da; the weight average molecular weight of the second polymer is 5,000-50,000 Da; and the weight average molecular weight of the third polymer is 60,000-250,000 Da; The organic solvent B includes C4-C 12 Straight chain alkanes, C4-C 12 Branched alkanes, C4-C 12 Cycloalkanes, aromatic hydrocarbons, C4-C 12 Olefins, C4-C 12 At least one of cycloolefins, petroleum ether, trifluoroacetic acid, butyl chloride, trichloroethylene, carbon tetrachloride, propyl ether, diethyl ether, butyl acetate, isobutyl isobutyrate and ethyl acetate; The solid electrolyte includes a sulfide solid electrolyte and / or an oxide solid electrolyte.

7. The method according to claim 6, characterized in that The composition further includes organic solvent 1 and organic solvent 2; The contact mixing operation in step (1) includes: Mixing a solution 1 containing the organic solvent 1, the first polymer and the lithium salt, a solution 2 containing the organic solvent 2, the second polymer and the conductive carbon, and a solution 3 containing the organic solvent B, the third polymer and the solid electrolyte to obtain the protective layer slurry; The organic solvent 1 and the organic solvent 2 are the same or different, and are each independently selected from at least one of acetonitrile, dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethyl sulfoxide, triethyl phosphate, trimethyl phosphate, ε-caprolactone and 1,4-butyrolactone.

8. The method according to claim 6 or 7, characterized in that In step (1), the contact mixing conditions include: temperature of 20-60°C and time of 1-24h; And / or, in step (2), the heat treatment conditions include: temperature of 40-120° C., time of 1-24 h.

9. A battery negative electrode material prepared by the method according to any one of claims 6 to 8.

10. A solid-state lithium battery, characterized in that: The battery contains a positive electrode material, a solid electrolyte and a negative electrode material; The negative electrode material is the battery negative electrode material according to claim 9.

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