Composite negative electrode material, negative electrode plate, preparation method and battery

Abstract

The invention relates to a composite negative electrode material, a negative electrode pole piece, a preparation method and a battery. The composite negative electrode material comprises a pole piece substrate and an ionic conduction medium positioned on the pole piece substrate, the ionic conduction medium comprises a polymer and a lithium salt, and the polymer comprises an acrylate polymer and a vinyl ester polymer. The lithium ion transmission capability can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a composite negative electrode material, a negative electrode sheet, a preparation method, and a battery. Background Technology

[0002] Solid-state battery technology, as a core technology for next-generation electric vehicles, offers significant value in two areas: a revolutionary safety improvement (completely eliminating the risk of battery fires) and a leap in driving range (energy density exceeding that of existing batteries by more than 40%). Among various solid-state battery systems, sulfide solid electrolytes possess ionic conductivity (3-12 mS / cm) comparable to liquid electrolytes, enabling them to withstand extreme tests such as nail penetration and compression, thus bringing revolutionary safety improvements to the electric vehicle field. However, several key issues remain to be addressed in the development of sulfide solid-state batteries.

[0003] In sulfide solid-state batteries, silicon or silicon-carbon materials are usually used for the negative electrode in order to achieve high energy density. The contact between the active materials inside the negative electrode is a "point-to-point" contact. The lithium ion transfer efficiency between the negative electrode particles is low and the interface impedance is high. Specifically, during the charging and discharging process, the discharge capacity of the negative electrode sheet decreases and the rate performance is poor.

[0004] To address this issue, some related technologies involve immersing the negative electrode sheet in a monomeric LiFPA electrolyte, followed by thermosetting to polymerize the monomers, thus constructing ion transport channels within the electrode sheet and reducing the internal lithium-ion transport impedance. However, this immersion method has several drawbacks: 1. The LiFPA electrolyte has a certain dissolving effect on the binder in the electrode sheet. Prolonged immersion can lead to partial dissolution of the binder in the electrolyte, ultimately resulting in insufficient adhesion of the negative electrode material to the current collector; 2. During in-situ curing after immersion in the electrolyte, it is difficult to ensure that all monomers are polymerized. Typically, about 10% of the monomers remain incompletely polymerized, resulting in some liquid residue in the negative electrode sheet. This residue can participate in reactions during battery charging and discharging, leading to a decrease in battery performance.

[0005] Negative electrode active materials, such as pure silicon and silicon-carbon, exhibit significant volume expansion and contraction during charging and discharging. This drastic volume change causes collisions between silicon-carbon particles, which disrupt the internal ion conduction network, leading to impaired ion transport and a gradual decrease in battery capacity. Some related technologies introduce a carbon coating layer onto the surface of the silicon-carbon negative electrode active particles to suppress expansion, ultimately improving battery performance. While this method partially suppresses the expansion rate of silicon-carbon particles by introducing a carbon coating layer, a large number of voids still exist within the negative electrode, and the contact between negative electrode particles remains point-to-point. This results in a low lithium-ion transport rate and high internal impedance. Summary of the Invention

[0006] This application provides a composite negative electrode material, a negative electrode sheet, a preparation method, and a battery to improve lithium-ion transport capability.

[0007] In a first aspect, a composite negative electrode material is provided, which includes an electrode substrate and an ion-conducting medium located on the electrode substrate; The ion-conducting medium comprises a polymer and a lithium salt, wherein the polymer comprises acrylate polymers and vinyl ester polymers.

[0008] In some embodiments, the acrylate polymers include at least one of polymethyl acrylate (PMA), polyethyl acrylate (PEA), polybutyl acrylate (n-butyl acrylate), poly(2-ethylhexyl acrylate), polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polybutyl methacrylate (PBMA), polyethylene glycol monomethacrylate, poly(β-hydroxypropyl methacrylate), polyglycidyl methacrylate, and polyallyl methacrylate. And / or, the molecular weight range of the acrylate polymer is 20,000 to 1,000,000; And / or, the molecular weight range of the vinyl ester polymer is 1,000 to 1,000,000; And / or, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium dioxaborate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluoromethanesulfonylimide.

[0009] In some embodiments, the vinyl ester polymer is obtained by free radical polymerization of small molecule monomers initiated by a photoinitiator; The small molecule monomers include at least one of ethylene carbonate, ethylene carbonate, methyl ethylene carbonate, ethyl ethylene carbonate, 1,2-dimethyl ethylene carbonate, 1,2-diethyl ethylene carbonate, fluoroethylene carbonate, and trifluoromethyl ethylene carbonate. The photoinitiator includes at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone.

[0010] In some embodiments, the photoinitiator accounts for 0.05 to 2% of the mass of the small molecule monomer.

[0011] In some embodiments, the ion-conducting medium further includes a plasticizer.

[0012] In some embodiments, the plasticizer accounts for 3-5% of the total mass of the ion-conducting medium; And / or, the plasticizer includes polyethylene glycol dimethyl ether, perfluoropolyether, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, 1-butyl-3-methylimidazolium chloride, 1-ethyl-1-methylpyrrolidine bis(fluorosulfonyl)imide salt, 1-methyl-1-propylpyrrolidine ononium bis(fluorosulfonyl)imide salt, tributylmethylammonium bis(fluorosulfonyl)imide salt, tetra... At least one of the following: triethylmethylammonium fluoroborate, tetraethylammonium tetrafluoroborate, 1-propyl-1-methylpiperidine bis(trifluoromethanesulfonyl)imide, fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfate, 4-methylethylene sulfate, vinylethylene carbonate, 4-ethylethylene sulfate, 1,3-propanesulfonate lactone, vinylethylene sulfite, 1-butyl-1-methylpiperidine bis(trifluoromethanesulfonyl)imide, and 1-ethyl-4-tert-butylpyridine iodide.

[0013] In some embodiments, the acrylate polymer constitutes 30-50% of the total mass of the ion-conducting medium; The vinyl ester polymer constitutes 30-55% of the total mass of the ion-conducting medium; The lithium salt accounts for 10-20% of the total mass of the ion-conducting medium.

[0014] In some embodiments, the ion-conducting medium accounts for 10 to 40% of the total mass of the composite negative electrode material.

[0015] In some embodiments, the electrode substrate includes a negative electrode active material, a conductive agent, and a solid electrolyte.

[0016] In some embodiments, the solid electrolyte accounts for 3% to 30% of the total mass of the electrode substrate; The negative electrode active material accounts for 60-90% of the total mass of the electrode substrate; The conductive agent accounts for 3 to 10% of the total mass of the electrode substrate.

[0017] In some embodiments, the negative electrode active material includes at least one of graphite, hard carbon, silicon, SiO, and silicon-carbon (SiC). And / or, the conductive agent includes one of acetylene black and carbon nanofibers; or, the conductive agent includes acetylene black and carbon nanofibers, and the mass ratio of acetylene black to carbon nanofibers is 1:(0.5~1).

[0018] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes and oxide solid electrolytes.

[0019] In some embodiments, the sulfide solid electrolyte is selected from yLi₂S·(100-y)P₂S₅, Li₃PS₄, and Li₇P₃S.11 Li6PS5X and its derivatives, Li 10 MP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li4GeS4 and Li 11 Sn2PS 12 At least one of the following, 0≤y≤100, X=Cl,Br,I, M=Ge,Sn,Si; And / or, the oxide solid electrolyte is selected from one or more of the following substances: Li 1+x1 Al x1 Ti 2-x1 (PO4)3,x1=0~0.6; Li 7-x2 La3Zr 2-x2 Ta x2 O 12 x² = 0 to 0.6; Li 7-x3 La3Zr 2-x3 Nb x3 O 12 x3 = 0 to 0.6; Li 7-3x4 Ga x4 La3Zr2O 12 x4 = 0 to 0.6; Li 7-3x5 Al x5 La3Zr2O 12 x5 = 0 to 0.4; Li 1+x9 Al x9 Ge 2-x9 (PO4)3, x9 = 0 to 0.6; Li 1+x10 Ta2P 1-x10 Si x10 O8, x10 = 0~1; Li 1+x11 Zr2Si x11 P 3-x11 O 12 x11 = 0 to 3; Li 2-x12 La (1+x12) / 3 Nb₂O₆F, x¹² = 0–0.8; Li2-x13 La (1+x13) / 3 Ta₂O₆F, x¹³ = 0–0.8.

[0020] Secondly, a method for preparing the composite negative electrode material as described above is provided, comprising: The electrode substrate and the ion-conducting medium are stirred and mixed to obtain a composite negative electrode material.

[0021] In some embodiments, the vinyl ester polymer is obtained by free radical polymerization of small molecule monomers initiated by a photoinitiator; The electrode substrate includes a negative electrode active material, a conductive agent, and a solid electrolyte; The electrode substrate and the ion-conducting medium are stirred and mixed to obtain a composite negative electrode material, specifically including: A conductive agent and an acrylate polymer are added to a solvent and stirred at room temperature to obtain a conductive adhesive. Small molecule monomers, photoinitiators, and lithium salts are added to a solvent and stirred at room temperature. During the stirring process, continuous light irradiation is applied to initiate the photopolymerization of the small molecule monomers, resulting in an ion-conducting liquid. The conductive adhesive and ion-conducting liquid were mixed and stirred at room temperature for a period of time. Then, the negative electrode active material and solid electrolyte were added and stirred at room temperature to obtain the composite negative electrode material.

[0022] In some embodiments, ultraviolet (UV) lamps are used for irradiation, with a power of 10–50W, an illumination area of ​​5cm × 5cm, and a distance of 10–30cm between the UV lamp and the stirring flask.

[0023] In some embodiments, the solvent is selected from at least one of isobutyl isobutyrate, ethyl acetate, anisole, butyl butyrate, hexyl butyrate, dimethyl ether, dipropyl ether, dibutyl ether, and methyl ethyl ether.

[0024] Thirdly, a negative electrode sheet is provided, which includes a negative current collector and an active layer coated on the negative current collector, the active layer being formed of any of the composite negative electrode materials described above.

[0025] Fourthly, a method for preparing the negative electrode sheet as described above is provided, comprising: The composite negative electrode material is coated onto the negative electrode current collector, and then heated and dried under vacuum in sequence. After rolling, the negative electrode sheet is obtained.

[0026] Fifthly, a battery is provided that includes the negative electrode sheet described above.

[0027] The beneficial effects of the technical solution provided in this application include: The composite anode material provided in this application has an ion-conducting medium comprising two types of polymers, among which the acrylate polymers can play at least the following three roles in the composite anode material: 1. Acrylic ester polymers possess strong adhesive properties. Their molecular chains contain polar functional groups (such as ester and carboxylic acid groups), which can bond the negative electrode active material, conductive agent, and negative electrode current collector through multi-scale interactions such as hydrogen bonding, electrostatic interactions, and van der Waals forces, forming a stable interfacial bond. This dual chemical and physical bonding mechanism significantly improves the mechanical strength and interfacial stability of the electrode material, thereby ensuring the structural integrity of the electrode.

[0028] 2. Regarding ion conduction, the COC ester bonds in acrylate polymer molecules possess specific polarity and coordination ability, enabling them to form stable coordination structures with lithium ions. This coordination induces the orderly migration of lithium ions within the material via a "rocking chair" mechanism. Simultaneously, acrylate polymers can also regulate the pore structure and microphase separation behavior of the electrolyte network through chain segment movement, further optimizing the lithium ion diffusion channels and thus enhancing the lithium ion transport capacity within the composite anode material.

[0029] 3. Acrylic ester polymers typically contain polar functional groups, enabling them to form hydrogen bonds or electrostatic interactions with polar solvent molecules. These intermolecular interactions significantly reduce the interparticle forces in the slurry system, effectively suppressing agglomeration and promoting uniform dispersion of the negative electrode active material in the slurry. Furthermore, their ability to regulate the rheological properties of the slurry imparts excellent thixotropic and shear-thinning characteristics, which not only improves coating efficiency but also allows for the preparation of electrode films with uniform pore structures.

[0030] Ethylene ester polymers in ion-conducting media contain a large number of ester bonds in their repeating units. Polymers with ester bonds can serve as polymer electrolytes. Their oxygen atoms coordinate with lithium ions, and lithium ion transport is achieved through a "rocking chair" effect, which can effectively improve the problem of insufficient lithium ion conductivity in composite anode materials. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating the preparation method of the composite negative electrode material provided in this application embodiment. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] This application provides a composite negative electrode material, which includes an electrode substrate and an ion-conducting medium located on the electrode substrate. Specifically, the ion-conducting medium is located at least inside the porous structure of the electrode substrate, and may also be partially located on the outer surface of the electrode substrate. The ion-conducting medium includes a polymer and a lithium salt, and the polymer includes acrylate polymers and vinyl ester polymers.

[0035] The composite anode material provided in this application has an ion-conducting medium comprising two types of polymers, among which the acrylate polymers can play at least the following three roles in the composite anode material: 1. Acrylic ester polymers possess strong adhesive properties. Their molecular chains contain polar functional groups (such as ester and carboxylic acid groups), which can bond the negative electrode active material, conductive agent, and negative electrode current collector through multi-scale interactions such as hydrogen bonding, electrostatic interactions, and van der Waals forces, forming a stable interfacial bond. This dual chemical and physical bonding mechanism significantly improves the mechanical strength and interfacial stability of the electrode material, thereby ensuring the structural integrity of the electrode.

[0036] 2. Regarding ion conduction, the COC ester bonds in acrylate polymer molecules possess specific polarity and coordination ability, enabling them to form stable coordination structures with lithium ions. This coordination induces the orderly migration of lithium ions within the material via a "rocking chair" mechanism. Simultaneously, acrylate polymers can also regulate the pore structure and microphase separation behavior of the electrolyte network through chain segment movement, further optimizing the lithium ion diffusion channels and thus enhancing the lithium ion transport capacity within the composite anode material.

[0037] 3. Acrylic ester polymers typically contain polar functional groups, enabling them to form hydrogen bonds or electrostatic interactions with polar solvent molecules. These intermolecular interactions significantly reduce the interparticle forces in the slurry system, effectively suppressing agglomeration and promoting uniform dispersion of the negative electrode active material in the slurry. Furthermore, their ability to regulate the rheological properties of the slurry imparts excellent thixotropic and shear-thinning characteristics, which not only improves coating efficiency but also allows for the preparation of electrode films with uniform pore structures.

[0038] Ethylene ester polymers in ion-conducting media contain a large number of ester bonds in their repeating units. Polymers with ester bonds can serve as polymer electrolytes. Their oxygen atoms coordinate with lithium ions, and lithium ion transport is achieved through a "rocking chair" effect, which can effectively improve the problem of insufficient lithium ion conductivity in composite anode materials.

[0039] The acrylate polymer can be selected from a variety of options. As an example, preferably, the acrylate polymer includes at least one of polymethyl acrylate (PMA), polyethyl acrylate (PEA), polybutyl acrylate (n-butyl acrylate), poly(2-ethylhexyl acrylate), polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polybutyl methacrylate (PBMA), polyethylene glycol monomethacrylate, poly(β-hydroxypropyl methacrylate), polyglycidyl methacrylate, and polyallyl methacrylate.

[0040] For acrylate polymers, excessively low molecular weight leads to insufficient adhesion, and low molecular weight binders may fail to effectively bond the active material and current collector, causing material detachment and affecting electrode stability. Excessively high molecular weight increases the viscosity of the slurry, affecting its flowability and the electrode's processing performance. Preferably, the molecular weight of the acrylate polymer ranges from 20,000 to 1,000,000.

[0041] For vinyl ester polymers, polymers with excessively low molecular weights typically have lower mechanical strength and are prone to deformation or breakage during battery cycling due to repeated expansion / contraction of the negative electrode material. Polymer electrolytes with excessively high molecular weights usually have higher crystallinity or more compact chain structures, which can hinder lithium-ion migration and lead to reduced lithium-ion conductivity. In addition, increasing molecular weight also increases the viscosity of the slurry, thereby increasing processing difficulty and affecting the operability of coating or molding processes. Preferably, the molecular weight range of the vinyl ester polymer is 1,000 to 1,000,000.

[0042] The lithium salt can be selected from a variety of options. As an example, preferably, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium dioxaborate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluoromethanesulfonylimide.

[0043] In this application, the ethylene ester polymer is obtained by free radical polymerization of small molecule monomers initiated by a photoinitiator.

[0044] Photoinitiated polymerization can typically be carried out at lower temperatures, unlike traditional thermally initiated polymerization which relies on high temperatures or high pressures. Photoinitiated polymerization allows for precise control of the light beam to target specific areas, enabling the polymerization reaction to occur at specific spatial locations and time periods. Furthermore, the polymerization rate can be controlled by precisely regulating the light intensity and irradiation time, thereby controlling the molecular weight and structural uniformity of the polymer. This contributes to obtaining polymers with more stable properties and higher quality.

[0045] The small molecule monomer can be selected from a variety of options. As an example, preferably, the small molecule monomer includes at least one of ethylene carbonate, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluorovinylene carbonate, and trifluoromethyl vinylene carbonate.

[0046] The photoinitiator can be selected from a variety of options. As an example, preferably, the photoinitiator includes at least one selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone.

[0047] In this application, polyacrylate polymers and photoinitiated polymerization are used. The structure may contain partially crystalline regions that can hinder lithium-ion transport. To address this issue, the ion-conducting medium also includes a plasticizer. First, the plasticizer itself has high ionic conductivity, which can further improve the overall ion conductivity. Second, the plasticizer can effectively increase the amorphous regions within the polymer, improving the lithium-ion transport efficiency in these regions.

[0048] The plasticizer can be selected from a variety of options. As an example, preferably, the plasticizer includes polyethylene glycol dimethyl ether (number average molecular weight Mn of 100–1000), perfluoropolyether (number average molecular weight Mn of 100–1000), 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium chloride, 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, and 1-methyl-1-propylpyrrolidine onium bis(fluorosulfonyl)imide. At least one of the following: amine salt, tributylmethylammonium bis(trifluoromethanesulfonyl)imide salt, triethylmethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, 1-propyl-1-methylpiperidine bis(trifluoromethanesulfonyl)imide salt, fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, propylene sulfate, 4-methylethylene sulfate, vinylethylene carbonate, 4-ethylethylene sulfate, 1,3-propanesulfonate lactone, vinylethylene sulfite, 1-butyl-1-methylpiperidine bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-4-tert-butylpyridine iodide.

[0049] Furthermore, in the composite anode material, the ion-conducting medium accounts for 10-40% of the total mass of the composite anode material, with the remainder being the mass fraction of the electrode matrix.

[0050] In the ion-conducting medium, the acrylate polymer accounts for 30-50% of the total mass of the ion-conducting medium, the vinyl ester polymer accounts for 30-55% of the total mass of the ion-conducting medium, the lithium salt accounts for 10-20% of the total mass of the ion-conducting medium, and the plasticizer accounts for 3-5% of the total mass of the ion-conducting medium.

[0051] In the ethylene ester polymer, the photoinitiator accounts for 0.05 to 2% of the mass of the small molecule monomer.

[0052] The electrode substrate includes a negative electrode active material, a conductive agent, and a solid electrolyte.

[0053] The solid electrolyte accounts for 3-30% of the total mass of the electrode substrate, the negative electrode active material accounts for 60-90% of the total mass of the electrode substrate, and the conductive agent accounts for 3-10% of the total mass of the electrode substrate.

[0054] The negative electrode active material can be selected from a variety of materials. As an example, preferably, the negative electrode active material includes at least one of graphite, hard carbon, silicon, SiO, and silicon-carbon (SiC).

[0055] The conductive agent can be selected from a variety of options. As an example, preferably, the conductive agent includes one of acetylene black and carbon nanofibers; or, the conductive agent includes acetylene black and carbon nanofibers, and the mass ratio of acetylene black to carbon nanofibers is 1:(0.5~1).

[0056] The solid electrolyte can be selected from several options. As an example, preferably, the solid electrolyte includes one or more of sulfide solid electrolytes and oxide solid electrolytes.

[0057] The sulfide solid electrolyte can be selected from a variety of options. As an example, preferably, the sulfide electrolyte is selected from yLi₂S·(100-y)P₂S₅, Li₃PS₄, and Li₇P₃S. 11 Li6PS5X and its derivatives, Li 10 MP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li4GeS4 and Li 11 Sn2PS12 At least one of the following, 0≤y≤100, X=Cl,Br,I, M=Ge,Sn,Si.

[0058] The oxide solid electrolyte can be selected from a variety of materials. As an example, preferably, the oxide solid electrolyte is selected from one or more of the following substances: Li 1+x1 Al x1 Ti 2-x1 (PO4)3,x1=0~0.6, i.e. LATP.

[0059] Ta-doped LLZO, i.e., Li 7-x2 La3Zr 2-x2 Ta x2 O 12 ,x2=0~0.6,LLZTO.

[0060] Nb-doped LLZO, i.e., Li 7-x3 La3Zr 2-x3 Nb x3 O 12 x3 = 0 ~ 0.6, LLZNO.

[0061] Ga-doped LLZO, i.e., Li 7-3x4 Ga x4 La3Zr2O 12 x4 = 0 to 0.6, LLGZO.

[0062] Li 7-3x5 Al x5 La3Zr2O 12 x5 = 0 to 0.4.

[0063] Li 1+x9 Al x9 Ge 2-x9 (PO4)3, x9 = 0 to 0.6, i.e., LAGP.

[0064] Li 1+x10 Ta2P 1-x10 Si x10 O8, x10 = 0~1, i.e. LTPSO.

[0065] Li 1+x11 Zr2Si x11 P 3-x11 O 12 , x11 = 0 ~ 3.

[0066] Li 2-x12 La (1+x12) / 3 Nb₂O₆F, x₁₂ = 0–0.8.

[0067] Li 2-x13 La (1+x13) / 3 Ta₂O₆F, x¹³ = 0–0.8.

[0068] In summary, this application significantly expands the lithium-ion transport pathway by introducing an ion-conducting medium with an optimized structure, combining the properties of two polymers, to enhance lithium-ion transport capabilities. Specifically, the coordination of lithium ions with ester bonds in the acrylate polymer and with oxygen atoms in the vinyl ester polymer achieves lithium-ion transport through a "rocking chair" effect. Furthermore, the special structure formed by photo-initiated polymerization of the vinyl ester polymer further improves the conductivity of lithium ions within the composite anode material.

[0069] This application achieves a more uniform and efficient structural distribution within the electrode substrate through a unique design. The contact method between active materials is transformed from the traditional "point-to-point" contact to a highly efficient connection through an ion-conducting medium, significantly reducing the voids between negative electrode particles. This structural optimization not only improves the transport efficiency of lithium ions between particles but also provides strong support for enhancing the battery's charge and discharge performance.

[0070] To improve battery stability and cycle life, this application effectively mitigates the structural damage caused by drastic volume changes in negative electrode active materials (such as silicon or silicon-carbon) during charge and discharge through comprehensive optimization design of the ion-conducting medium and electrode structure. The amorphous regions introduced by the plasticizer further reduce stress concentration in the active material, significantly improving battery cycle stability and lifespan. Furthermore, the photoinitiated polymerization technology employed in this application simplifies and controls the preparation process, eliminating the need for high-temperature and high-pressure conditions, and allowing for precise control of photopolymerization conditions to obtain polymers with more uniform and stable performance.

[0071] This application also provides a method for preparing a composite anode material, which includes: stirring and mixing an electrode substrate and an ion-conducting medium to obtain a composite anode material.

[0072] Specifically, see Figure 1 As shown, the electrode substrate and the ion-conducting medium are stirred and mixed to obtain a composite negative electrode material comprising: S1: Add the conductive agent and acrylate polymer to the solvent and stir at room temperature to obtain a conductive adhesive.

[0073] S2: Add small molecule monomers, photoinitiators and lithium salts to a solvent, stir at room temperature, and continuously irradiate with light during stirring to initiate photopolymerization of the small molecule monomers, thus obtaining an ion-conducting liquid.

[0074] The mixture was stirred in a colorless and transparent stirring flask. During the stirring process, a UV lamp of a certain power was used to continuously irradiate the stirring flask at a certain distance and with a certain illumination area, which triggered the photopolymerization of monomer molecules.

[0075] Ultraviolet (UV) lamps are used for irradiation. The power of the UV lamps is 10–50W, the irradiation area of ​​the UV lamps is 5cm × 5cm, and the distance between the UV lamps and the stirring flasks used is 10–30cm.

[0076] S3: Mix the conductive adhesive with the ion-conducting liquid and stir at room temperature for a period of time. Then add the negative electrode active material and the solid electrolyte and stir at room temperature to obtain the composite negative electrode material.

[0077] The solvent can be selected from a variety of options. As an example, preferably, the solvent is selected from at least one of isobutyl isobutyrate, ethyl acetate, anisole, butyl butyrate, hexyl butyrate, dimethyl ether, dipropyl ether, dibutyl ether, and methyl ethyl ether.

[0078] This application also provides a negative electrode sheet, which includes a negative current collector and an active layer coated on the negative current collector, wherein the active layer is formed of the composite negative electrode material.

[0079] During preparation, the composite negative electrode material is coated onto the negative electrode current collector, and then heated and vacuum dried sequentially, followed by rolling to obtain the negative electrode sheet. For example, as an example, it is dried at 100°C for 2 hours, and then transferred to a vacuum dryer at 100°C for 24 hours.

[0080] This application also provides a battery including the negative electrode plate.

[0081] The battery also includes a positive electrode and a solid electrolyte membrane.

[0082] During preparation, the negative electrode sheet is dried in a vacuum oven and set aside; a sulfide solid electrolyte is selected as the solid electrolyte membrane of the solid battery; the dried negative electrode sheet is placed on one side of the solid electrolyte membrane as the negative electrode and stacked to bond the negative electrode sheet and the solid electrolyte membrane together and set aside; the positive electrode sheet is placed on the other side of the solid electrolyte membrane and then pressurized and sealed to obtain the sulfide solid battery.

[0083] Preferably, the positive electrode active material of the positive electrode sheet is selected from at least one of lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, spinel nickel manganese oxide material, and lithium-rich manganese material.

[0084] Preferably, the conductive agent of the positive electrode sheet is selected from at least one of carbon nanofibers, conductive graphite, conductive carbon black, carbon nanotubes, and graphene.

[0085] Preferably, when bonding the electrode to the solid electrolyte membrane, the adhesive used is selected from at least one of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, nitrile rubber, and styrene-butadiene rubber.

[0086] The batteries mentioned above are solid-state batteries, such as all-solid-state batteries or semi-solid-state batteries.

[0087] The present application will be described in detail below through examples.

[0088] Example 1 A composite anode material includes an electrode substrate and an ion-conducting medium located on the electrode substrate, wherein the ion-conducting medium accounts for 30% of the total mass of the composite anode material.

[0089] The electrode substrate comprises a negative electrode active material (silicon-carbon), a conductive agent (acetylene black), and a solid electrolyte (Li6PS5Cl). The solid electrolyte accounts for 25% of the total mass of the electrode substrate, the negative electrode active material accounts for 70% of the total mass of the electrode substrate, and the conductive agent accounts for 5% of the total mass of the electrode substrate.

[0090] The ion-conducting medium comprises a polymer, a plasticizer (polyethylene glycol dimethyl ether PEGDE, Mn 500), and a lithium salt (lithium hexafluorophosphate LiPF6). The polymer comprises an acrylate polymer (polymethyl methacrylate PMMA, molecular weight 200,000) and a vinyl ester polymer (small molecule monomer vinylene carbonate VCE, photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide). In the ion-conducting medium, the acrylate polymer accounts for 40% of the total mass of the ion-conducting medium, the vinyl ester polymer accounts for 40% of the total mass of the ion-conducting medium, the lithium salt accounts for 16% of the total mass of the ion-conducting medium, and the plasticizer accounts for 4% of the total mass of the ion-conducting medium. Within the vinyl ester polymer, the photoinitiator accounts for 0.5% of the small molecule mass.

[0091] The preparation method of the negative electrode sheet is as follows: 101. Add the conductive agent and acrylate polymer to the solvent ethyl acetate and stir at room temperature for 2 hours to obtain a conductive adhesive.

[0092] 102. Add the small molecule monomer, photoinitiator, and lithium salt to a stirred flask containing ethyl acetate as solvent. Irradiate the flask with a UV lamp (30W) at a distance of 20cm from the stirred flask with a light area of ​​5cm×5cm, and stir for 4 hours to initiate polymerization and form an ion-conducting liquid.

[0093] 103. Mix the conductive adhesive with the ion-conducting liquid and stir for 1 hour. Add the negative electrode active material and solid electrolyte and continue stirring for 4 hours to obtain the composite negative electrode material.

[0094] 104. Coat the composite negative electrode material obtained in step 103 onto copper foil and dry at 100°C for 2 hours. Vacuum dry for 24 hours, and roll press to obtain the negative electrode sheet.

[0095] A method for preparing a sulfide solid-state battery includes the following steps: 201. Place the negative electrode sheet obtained in step 104 in a vacuum oven to dry it for later use; 202. Li6PS5Cl electrolyte was selected as the solid electrolyte membrane for sulfide solid-state batteries; 203. Place the dried negative electrode sheet from step 201 as the negative electrode on one side of the solid electrolyte membrane from step 202, and stack them to assemble a "sandwich" structure. 204. In the active material layer of the positive electrode, the mass ratio of the components is nickel-cobalt-manganese ternary material: sulfide electrolyte: binder: conductive agent = 70:26:2:2. The binder is nitrile rubber (NBR), the conductive agent is carbon nanofiber (VGCF), and the sulfide electrolyte is Li6PS5Cl. The positive electrode is placed on the other side of the solid electrolyte membrane, and the sulfide solid battery is obtained by pressure encapsulation.

[0096] Example 2 The difference between this embodiment and Embodiment 1 is that: The acrylate polymer is polyethyl methacrylate (PEMA) with a molecular weight of 500,000, and the ethylene ester polymer uses the small molecule monomer ethylene ethylene carbonate (VCE2).

[0097] Example 3 The difference between this embodiment and Embodiment 1 is that: The plasticizer is 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4, the acrylate polymer is polyethyl methacrylate (PEMA) with a molecular weight of 500,000, and the vinyl ester polymer is the small molecule monomer ethylene ethylene carbonate (VCE2).

[0098] Example 4 The difference between this embodiment and Embodiment 1 is that: The UV lamp should be 10cm away from the stirring flask.

[0099] Example 5 The difference between this embodiment and Embodiment 1 is that: The UV lamp should be 30cm away from the stirring flask.

[0100] Example 6 The difference between this embodiment and Embodiment 1 is that: The plasticizer used is perfluoropolyether (Mn, 500).

[0101] Example 7 The difference between this embodiment and Embodiment 1 is that: The acrylate polymer used is polyethyl acrylate (PEA) with a molecular weight of 200,000, and the plasticizer used is 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt.

[0102] Example 8 The difference between this embodiment and Embodiment 1 is that: The lithium salt used is lithium bis(fluoromethanesulfonyl)imide, and the solid electrolyte is Li7La3Zr2O. 12 .

[0103] Example 9 The difference between this embodiment and Embodiment 1 is that: The solid electrolyte accounts for 30% of the total mass of the electrode substrate, the negative electrode active material accounts for 65% of the total mass of the electrode substrate, and the conductive agent accounts for 5% of the total mass of the electrode substrate.

[0104] Example 10 The difference between this embodiment and Embodiment 1 is that: In the ion-conducting medium, the acrylate polymer accounts for 35% of the total mass of the ion-conducting medium, the vinyl ester polymer accounts for 46% of the total mass of the ion-conducting medium, the lithium salt accounts for 15% of the total mass of the ion-conducting medium, and the plasticizer accounts for 4% of the total mass of the ion-conducting medium.

[0105] Example 11 The difference between this embodiment and Embodiment 1 is that: Without the addition of plasticizers, in this ion-conducting medium, the acrylate polymer accounts for 41% of the total mass of the ion-conducting medium, the vinyl ester polymer accounts for 42% of the total mass of the ion-conducting medium, and the lithium salt accounts for 17% of the total mass of the ion-conducting medium.

[0106] Example 12 The difference between this embodiment and Embodiment 1 is that: Photoinitiated polymerization is not used.

[0107] Example 13 The difference between this embodiment and Embodiment 1 is that: The distance between the UV lamp and the stirring flask is 50cm.

[0108] Example 14 The difference between this embodiment and Embodiment 1 is that: The distance between the UV lamp and the stirring flask is 5cm.

[0109] Example 15 The difference between this embodiment and Embodiment 1 is that: No acrylate polymers are added. In this case, the vinyl ester polymer accounts for 81% of the total mass of the ion-conducting medium, the lithium salt accounts for 15% of the total mass of the ion-conducting medium, and the plasticizer accounts for 4% of the total mass of the ion-conducting medium.

[0110] Example 16 The difference between this embodiment and Embodiment 1 is that: No acrylate polymers or vinyl ester polymers are added. In this case, the lithium salt accounts for 80% of the total mass of the ion-conducting medium, and the plasticizer accounts for 20% of the total mass of the ion-conducting medium.

[0111] Example 17 The difference between this embodiment and Embodiment 1 is that: No vinyl ester polymers are added. In this case, the acrylate polymers account for 80% of the total mass of the ion-conducting medium, the lithium salt accounts for 16% of the total mass of the ion-conducting medium, and the plasticizer accounts for 4% of the total mass of the ion-conducting medium.

[0112] Example 18 The difference between this embodiment and Embodiment 1 is that: Ethylene carbonate (VCE) is reacted with photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide to obtain an ethylene ester polymer. This ethylene ester polymer is then directly added as a finished product, eliminating the need for photoinitiation in the preparation of the negative electrode.

[0113] Detection and Analysis 1) Battery first-efficiency analysis The negative electrode obtained in the example was used to assemble a half cell. The performance was evaluated using a sandwich structure of lithium sheet-indium sheet-solid electrolyte-negative electrode. Charge and discharge tests were performed in a battery charge and discharge test system. The capacity of the first charge was divided by the capacity of the first discharge to obtain the first coulombic efficiency. The first efficiency analysis can reflect the ion conduction ability of the electrolyte inside the negative electrode during the first charge. The lower the first efficiency, the worse the internal ion conduction ability.

[0114] 2) Gram capacity test The negative electrode obtained in the example was assembled into a half cell. The performance of the negative electrode was evaluated using a sandwich structure of lithium sheet-indium sheet-solid electrolyte-negative electrode. Charge and discharge tests were performed in a battery charge and discharge test system, and the capacity of the first charge was recorded. 3) Cyclic charge-discharge test The sulfide solid-state battery provided in the example was subjected to cyclic charge-discharge tests using a battery testing system. The specific procedure was as follows: the battery cycle performance was tested at a voltage of 2.5V-4.4V. Under constant temperature conditions of 25℃, the battery was charged at 0.2C to 4.4V, and then charged at a constant voltage of 4.4V until the current was less than 0.05mA. After resting for 5 minutes, it was discharged at 0.2C to 2.5V, and the discharge capacity E0 was recorded. This charge-discharge cycle was repeated 100 times, and the discharge capacity E1 after 100 cycles was recorded. E0 / E1 × 100% is the cycle capacity retention rate. The test results are shown in the table below.

[0115]

[0116] Comprehensive data analysis and conclusions: 1. Coulomb efficiency (first-time effect) The initial efficiency of Examples 1 to 10 was between 88.59% and 89.65%, indicating that the design of the negative electrode significantly improved the ion conduction capacity inside the battery.

[0117] Examples 11 to 18 had lower first-efficiency: The first-efficiency of Example 11 (without plasticizer) was 82.86%, significantly lower than that of the Examples (88.59%–89.65%). The introduction of plasticizer significantly improved the amorphous regions of the polymer, increased lithium-ion transport efficiency, and also alleviated the volume expansion problem of the active material during charge and discharge, thereby improving the battery's first-efficiency, discharge capacity, and cycle stability.

[0118] Example 12 (without photoinitiated polymerization) had an initial efficiency of only 78.56%, which is more than 10% lower than that of Examples 1 to 10. Photoinitiated polymerization technology can precisely control the conditions of the polymerization reaction (such as light distance and light intensity), thereby producing a more uniform and stable ion-conducting medium. By optimizing the light distance (e.g., 20 cm in Example 1), the overall performance of the battery can be significantly improved.

[0119] Example 15 (using only conventional PVDF as a binder, without acrylate polymers) had an initial efficiency of only 70.29%, significantly lower than Examples 1 to 10, demonstrating the irreplaceable role of acrylate polymers in improving adhesion and ion conductivity. Acrylate polymers not only act as binders for the negative electrode sheet but also significantly enhance lithium-ion transport capacity through the coordination of their ester bonds with lithium ions. Furthermore, their ability to regulate the rheology of the slurry contributes to the preparation of electrode films with uniform pore structures, thereby improving the overall performance of the battery.

[0120] Example 17 has a lower first-efficiency than Example 12: Example 17, without the addition of vinyl ester polymers, has a first-efficiency of 77.12%, while Example 12, without photoinitiated polymerization, has a first-efficiency of 78.56. This is because in Example 12, even without photoinitiated polymerization, the small molecule monomers still have ester groups, which can provide channels for lithium-ion transport. Therefore, its performance is better than that of Example 17 without the addition of vinyl ester polymers.

[0121] Example 18 has a higher first-efficiency than Examples 12, 15, 16, and 17: Example 18 introduces ethylene ester polymers by using external photoinitiation, and then directly uses the well-reacted product to mix with lithium salt to obtain an ion-conducting liquid. Its performance is better than that of Examples 12, 15, 16, and 17, which did not add acrylate polymers, ethylene ester polymers, or did not use photoinitiation polymerization. This is because ethylene ester polymers can provide ion transport channels inside the negative electrode material, thus resulting in a higher first-efficiency.

[0122] 2. Capacity The discharge specific capacity of Examples 1 to 10 is between 1465 and 1573 mAh / g, showing a high energy density.

[0123] The discharge specific capacity of Examples 11 to 18 is relatively low: Example 11 (without plasticizer) had a value of 980 mAh / g, which was significantly lower than that of Examples 1 to 10, indicating that plasticizers are crucial for improving the amorphous regions and ion transport capabilities of polymers.

[0124] Example 15 (without using acrylate polymers) had only 865 mAh / g, which is much lower than that of Examples 1 to 10, indicating that acrylate polymers play an important role in improving the bonding performance and ion conductivity of active materials.

[0125] 3. Cyclic capacity retention The cycle capacity retention rates of Examples 1 to 10 were all between 95.14% and 96.32%, demonstrating excellent cycle stability.

[0126] The cycle capacity retention rates of Examples 11 to 18 were low. Example 11 (without plasticizer) had a content of 88.32%, which was more than 7% lower than that of Examples 1 to 10, indicating that plasticizers play an important role in reducing the volume expansion of active materials and improving cycle stability.

[0127] The cycle capacity retention rate of Example 14 (UV lamp too close to stirring bottle) was 90.39%, slightly lower than that of Examples 1 to 10, indicating that the control of the light irradiation distance during photoinitiated polymerization has a certain impact on the final performance.

[0128] The cycle capacity retention of Example 15 (without acrylate polymers) was only 55.48%, which was much lower than that of Examples 1 to 10, indicating that acrylate polymers play an important role in improving the mechanical properties and cycle stability of the battery.

[0129] Example 16 showed a cycle capacity retention of only 45.63%, which was much lower than that of Examples 1 to 10, indicating that acrylate polymers and vinyl ester polymers have a significant impact on battery performance and can improve the battery's cycle performance.

[0130] Example 17 showed a cycle capacity retention rate of only 60.32%, which was higher than that of Example 16. This indicates that the addition of acrylate polymers can improve the cycle performance of the battery. This is because acrylate polymers have adhesive and ion conduction capabilities, which can improve the cycle charge-discharge stability of the battery.

[0131] Example 18 introduces ethylene ester polymers using an external photoinitiator, and its performance is superior to that of Examples 12, 15, 16, and 17, which did not add acrylate polymers, ethylene ester polymers, or did not use photoinitiator polymerization. This is because acrylate polymers have adhesive and ion conduction capabilities, which can improve the cycle charge-discharge stability of the battery, and ethylene ester polymers can provide ion transport channels inside the negative electrode material, thus improving cycle performance.

[0132] This invention significantly improves the performance of solid-state lithium metal batteries by optimizing the design and fabrication process of the composite negative electrode. By introducing a plasticizer, the amorphous region of the polymer is optimized, improving lithium-ion transport efficiency and effectively mitigating structural damage caused by volume expansion of the active material during charge and discharge. The application of photo-initiated polymerization technology enables precise control of the polymer structure, further optimizing the ion transport pathway within the electrode. Furthermore, acrylate polymers not only exhibit excellent binding properties but also significantly enhance ion conductivity through the coordination of ester bonds with lithium ions. These factors work together to result in excellent performance of the composite negative electrode in terms of initial coulombic efficiency, discharge specific capacity, and cycle stability. Comparative experiments show that examples lacking plasticizers or using traditional binders are significantly inferior to examples in all performance indicators, highlighting the crucial role of each component in improving battery performance. This invention provides important technical support for the industrial application of solid-state batteries and has broad prospects.

[0133] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composite negative electrode material, characterized by, The composite negative electrode material comprises a pole piece substrate and an ion-conducting medium on the pole piece substrate, and the ion-conducting medium accounts for 10-40% of the total mass of the composite negative electrode material. The pole piece substrate comprises a negative electrode active material, a conductive agent and a solid-state electrolyte. The solid-state electrolyte accounts for 3-30% of the total mass of the pole piece substrate. The negative electrode active material accounts for 60-90% of the total mass of the pole piece substrate. The conductive agent accounts for 3-10% of the total mass of the pole piece substrate. The ion-conducting medium comprises a polymer and a lithium salt, and the polymer comprises an acrylate polymer and an ethylene ester polymer. The acrylate polymer accounts for 30-50% of the total mass of the ion-conducting medium. The ethylene ester polymer accounts for 30-55% of the total mass of the ion-conducting medium. The lithium salt accounts for 10-20% of the total mass of the ion-conducting medium. The ethylene ester polymer is obtained by free radical polymerization of small molecule monomers initiated by a photoinitiator. The small molecule monomers comprise at least one of vinyl ethylene carbonate, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluorinated vinylene carbonate and trifluoromethyl vinylene carbonate. The ultraviolet lamp is irradiated at a distance of 10-30 cm from the stirring bottle.

2. The composite negative electrode material of claim 1, wherein: The acrylate polymer comprises at least one of polymethyl acrylate (PMA), polyethyl acrylate (PEA), poly-n-butyl acrylate, poly-2-ethylhexyl acrylate, polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polybutyl methacrylate (PBMA), poly-mono-ethylene glycol methacrylate, poly-β-hydroxypropyl methacrylate, poly-glycidyl methacrylate and poly-allyl methacrylate. And / or, the molecular weight of the acrylate polymer ranges from 20,000 to 1,000,000. And / or, the molecular weight of the ethylene ester polymer ranges from 1,000 to 1,000,000. And / or, the lithium salt comprises at least one of lithium perchlorate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate and lithium bisfluoromethanesulfonimide.

3. The composite negative electrode material of claim 1, wherein: The photoinitiator comprises at least one of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone.

4. The composite negative electrode material of claim 3, wherein: The photoinitiator accounts for 0.05-2% of the mass of the small molecule monomers.

5. The composite negative electrode material of claim 1, wherein: The ion-conducting medium further comprises a plasticizer.

6. The composite negative electrode material of claim 5, wherein: The plasticizer accounts for 3-5% of the total mass of the ion-conducting medium. And / or, the plasticizer includes at least one of polyethylene glycol dimethyl ether, perfluoropolyether, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonimide, 1-butyl-3-methylimidazolium chloride, 1-ethyl-1-methylpyrrolidinium bis-trifluoromethanesulfonimide, 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide, tributylmethylammonium bis-trifluoromethanesulfonimide, triethylmethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, 1-propyl-1-methylpiperidinium bis-trifluoromethanesulfonimide, fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, propylene sulfate, 4-methyl ethylene sulfate, vinyl ethylene carbonate, 4-ethyl ethylene sulfate, 1,3-propane sulfonate lactone, vinyl ethylene sulfite, 1-butyl-1-methylpiperidinium bis-trifluoromethanesulfonimide, and 1-ethyl-4-tert-butylpyridine iodine. 7.The composite negative material of claim 1, wherein: the negative active material comprises at least one of graphite, hard carbon, silicon, SiO, and silicon carbon SiC; and / or, the conductive agent comprises one of acetylene black and carbon nanofiber; or, the conductive agent comprises acetylene black and carbon nanofiber, and the mass ratio of acetylene black to carbon nanofiber is 1: (0.5-1). 8.The composite negative material of claim 1, wherein: the solid-state electrolyte comprises one or more of sulfide solid-state electrolyte and oxide solid-state electrolyte. 9.The composite negative material of claim 8, wherein: The sulfide solid-state electrolyte is selected from at least one of yLi2S-(100-y)P2S5, Li3PS4, Li7P3S 11 6PS5X and derivatives thereof, Li 10 MP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li4GeS4 and Li 11 Sn2PS 12 , 0≤y≤100, X=Cl, Br, I, M=Ge, Sn, Si. and / or, the oxide solid-state electrolyte is selected from one or more of: Li 1+x1 Al x1 Ti 2-x1 (PO4)3, x1=0~0.6; Li 7-x2 La3Zr 2-x2 Ta x2 O 12 x2 = 0-0.6; Li 7-x3 La3Zr 2-x3 Nb x3 O 12 x3 = 0-0.6; Li 7-3x4 Ga x4 La3Zr2O 12 x4 = 0 to 0.6; Li 7-3x5 Al x5 La3Zr2O 12 x5 = 0 to 0.4; Li 1+x9 Al x9 Ge 2-x9 (PO4)3, x9 = 0 to 0.6; Li 1+x10 Ta2P 1-x10 Si x10 O8, x10 = 0-1; Li 1+x11 Zr2Si x11 P 3-x11 O 12 x11=0~3; Li 2-x12 La (1+x12) / 3 Nb2O6F, x12= 0-0.8; Li 2-x13 La (1+x13) / 3 Ta2O6F, x13 = 0-0.

8.

10. A method of preparing the composite negative electrode material according to claim 1, characterized by, which comprises: stirring and mixing the electrode sheet matrix and the ion-conducting medium to obtain the composite negative material. 11.The preparation method of the composite negative material of claim 10, wherein: the vinyl ester polymer is obtained by free radical polymerization of small molecule monomers initiated by a photoinitiator; the electrode sheet matrix comprises negative active material, conductive agent, and solid-state electrolyte; stirring and mixing the electrode sheet matrix and the ion-conducting medium to obtain the composite negative material, specifically comprising: adding the conductive agent and the acrylate polymer into the solvent, and stirring at room temperature to obtain conductive glue; adding the small molecule monomers, the photoinitiator, and the lithium salt into the solvent, and stirring at room temperature, and continuously irradiating during the stirring process to initiate the photopolymerization of the small molecule monomers to obtain the ion-conducting liquid; mixing the conductive glue and the ion-conducting liquid, and stirring at room temperature for a period of time, and then adding the negative active material and the solid-state electrolyte, and stirring at room temperature to obtain the composite negative material. 12.The preparation method of the composite negative material of claim 11, wherein: the ultraviolet lamp is irradiated, and the power of the ultraviolet lamp is 10-50 W, and the light irradiation area of the ultraviolet lamp is 5 cm×5 cm. 13.The preparation method of the composite negative material of claim 11, wherein: The solvent is selected from at least one of isobutyl isobutyrate, ethyl acetate, anisole, butyl butyrate, hexyl butyrate, dimethyl ether, dipropyl ether, dibutyl ether, and methyl ethyl ether.

14. A negative electrode sheet characterized by comprising: The negative electrode active material is formed by the composite negative electrode material according to any one of claims 1 to 13.

15. A method of producing the negative electrode sheet according to claim 14, characterized by, The negative electrode active material is formed by the composite negative electrode material according to any one of claims 1 to 13. The composite negative electrode material is coated on the negative electrode current collector, and is sequentially heated, dried, vacuum baked, and rolled to obtain the negative electrode sheet.

16. A battery, characterized by The negative electrode sheet according to claim 14.

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