Negative pole piece, solid-state battery and preparation method of negative pole piece

Abstract

The invention provides a negative pole piece, a solid-state battery and a preparation method of the negative pole piece, and belongs to the technical field of secondary batteries, and the negative pole piece comprises a negative current collector, a first coating and a second coating. Wherein the first coating is arranged on the negative electrode current collector, the first coating comprises a carbon material and a first lithium-loving material, and the first lithium-loving material comprises a lithium-loving metal oxide; a second coating layer is disposed on the first coating layer, the second coating layer comprising a second lithium-philic material, the second lithium-philic material comprising a lithium-philic metal and / or a lithium alloy of the lithium-philic metal. According to the negative electrode plate, through the synergistic effect of the double-layer lithium-loving structure on the negative electrode current collector, lithium ions can be guided to be uniformly and compactly deposited on a negative electrode interface, generation of lithium dendrites on the surface of a negative electrode is inhibited, and active lithium loss caused by surface side reaction and dead lithium generation on the negative electrode interface is reduced; therefore, the cycle life and the safety performance of the solid-state battery are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a negative electrode sheet, a solid-state battery, and a method for preparing the negative electrode sheet. Background Technology

[0002] Traditional anode materials (such as graphite and silicon-carbon) occupy a certain volume and mass within the battery, limiting the improvement of energy density in solid-state batteries. To further improve the energy density of solid-state batteries, anode-less battery technology has emerged. Its basic idea is to avoid pre-loading a lithium metal anode during battery assembly, instead directly extracting lithium ions from the positive electrode and depositing them on the anode current collector during charging to form a metallic lithium anode. Theoretically, this design can significantly increase the battery's energy density because it eliminates the volume and mass occupied by the anode active material and allows for the use of thinner anode current collectors.

[0003] However, during the charge-discharge cycle of a battery without a negative electrode, active lithium is difficult to deposit uniformly on the surface of the negative electrode current collector. Instead, it tends to form needle-like or dendritic lithium dendrites on the surface of the negative electrode current collector. The deposited lithium dendrites can easily pierce the solid electrolyte membrane, leading to internal short circuits in the battery and causing rapid capacity decay.

[0004] Therefore, it is necessary to design a method for preparing a negative electrode sheet, a solid-state battery, and a negative electrode sheet to improve the above-mentioned problems. Summary of the Invention

[0005] This invention provides a negative electrode sheet, a solid-state battery, and a method for preparing the negative electrode sheet, in order to improve the technical problem that lithium metal deposited on the negative electrode current collector in a negative electrode-less battery tends to form lithium dendrites, which can easily puncture the solid electrolyte membrane, causing battery short circuits and rapid capacity decay.

[0006] In a first aspect, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector, a first coating, and a second coating.

[0007] The first coating is disposed on the negative electrode current collector, and the first coating includes a carbon material and a first lithiophilic material, the first lithiophilic material including a lithiophilic metal oxide; the second coating is disposed on the first coating, the second coating including a second lithiophilic material, the second lithiophilic material including a lithiophilic metal and / or a lithium alloy of the lithiophilic metal.

[0008] In one example of the present invention, the first lithiophilic material includes at least one of TiO2, ZnO, and SnO2.

[0009] In one example of the present invention, the second lithiophilic material includes at least one of Ag, Al, Au, Sn, Zn, Ca, In, Pb, Bi, Mg, or lithium alloys of the above materials.

[0010] In one example of the present invention, the second lithiophilic material includes at least one of Ag, Zn, Mg, or lithium alloys of the above materials.

[0011] In one example of the present invention, the thickness of the first coating is 100 nm to 10 μm.

[0012] In one example of the present invention, the thickness of the second coating is 50 nm to 5 μm.

[0013] In one example of the present invention, the average particle size of the first lithiophilic material is 1 nm to 1 μm.

[0014] In one example of the present invention, the areal density of the first coating is 0.05 mg / cm³. 2 ~2mg / cm 2 .

[0015] In one example of the present invention, the average particle size of the second lithiophilic material is 1 nm to 500 nm.

[0016] In one example of the present invention, the areal density of the second coating is 0.01 mg / cm³. 2 ~1mg / cm 2 .

[0017] In one example of the present invention, the first coating further includes a binder, the binder having a mass content of 1 wt% to 5 wt% in the first coating, the mass content of the first lithiophilic material and the carbon material in the first coating being 95 wt% to 99 wt%, and the mass ratio of the first lithiophilic material to the carbon material being (5 to 99):(1 to 95).

[0018] In one example of the present invention, the mass content of the first lithiophilic material in the first coating is 4.5 wt% to 96 wt%, and the mass content of the carbon material in the first coating is 0.95 wt% to 92 wt%.

[0019] In one example of the present invention, the carbon material includes at least one of graphene, carbon nanotubes, hard carbon, soft carbon, carbon fiber, and carbon black.

[0020] In a second aspect, the present invention also provides a method for preparing a negative electrode sheet, the method comprising:

[0021] A first coating is formed on the negative electrode current collector; the first coating comprises a carbon material and a first lithiophilic material, wherein the first lithiophilic material comprises a lithiophilic metal oxide.

[0022] A second coating is formed on the first coating to obtain a negative electrode sheet; the second coating includes a second lithiophilic material, which includes a lithiophilic metal and / or a lithium alloy of the lithiophilic metal.

[0023] In a third aspect, the present invention also provides a solid-state battery, the solid-state battery comprising a positive electrode, a solid electrolyte membrane, and a negative electrode as described in any of the above examples, or a negative electrode prepared by the preparation method described in any of the above examples.

[0024] In the negative electrode sheet provided by this invention, the carbon material and lithium-loving metal oxide of the first coating provide a uniform and porous network substrate. The first coating can provide uniformly distributed lithium deposition sites on the surface of the second coating and provide channels for the rapid transport of lithium ions and electrons to induce the uniform dissolution and deposition of active lithium at the negative electrode interface. The second coating provides a negative electrode interface that is highly lithium-loving and has better compatibility with the solid electrolyte interface. Based on its own lithium-loving alloying properties, the second coating can further induce the uniform embedding and deposition of lithium ions at the negative electrode interface, reduce the negative electrode interface impedance, improve the negative electrode interface stability, and reduce the occurrence of side reactions between active lithium and solid electrolyte at the negative electrode interface, thereby effectively improving the rate performance, cycle life and safety performance of the solid-state battery.

[0025] In summary, the negative electrode sheet provided by this invention, through the synergistic effect of the double-layer lithiophilic structure on the negative electrode current collector, can guide lithium ions to be deposited uniformly and densely at the negative electrode interface, suppress the formation of lithium dendrites on the negative electrode surface, reduce the loss of active lithium caused by surface side reactions and dead lithium formation at the negative electrode interface, and improve the coulombic efficiency of lithium deposition and dissolution during charging and discharging, thereby significantly improving the cycle life and safety performance of solid-state batteries. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other embodiments based on these drawings without inventive effort.

[0027] In the attached diagram:

[0028] Figure 1 This is a schematic diagram of the negative electrode sheet in one embodiment of the present invention;

[0029] Figure 2 This is a schematic flowchart of a method for preparing a negative electrode sheet in one embodiment of the present invention.

[0030] The attached figures are labeled as follows:

[0031] 1. Negative electrode current collector; 2. First coating; 3. Second coating. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of the present invention is for describing specific implementation schemes and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0033] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as part of the scope of the invention.

[0034] In this specification, the average particle size (Dv50) can be defined as the equivalent diameter of the particle corresponding to the volumetric 50% proportion in the particle size distribution curve. The average particle size (Dv50) can be measured, for example, by laser diffraction. Dv50 can be obtained using a HELOS-RODOS type dry laser particle size analyzer. Laser diffraction can typically measure particle sizes from the submicron range to several millimeters, thus providing highly reproducible and high-resolution results.

[0035] like Figure 1 As shown, in a first aspect, the present invention provides a negative electrode sheet comprising a negative current collector 1, a first coating 2, and a second coating 3. The negative current collector 1 has two surfaces opposite each other in its own thickness direction. The first coating 2 and the second coating 3 are disposed on at least one surface of the negative current collector 1, such that the first coating 2 and the second coating 3 are sequentially disposed on the surface of the negative current collector 1 facing the positive electrode sheet in a direction away from the negative current collector 1. The first coating 2 is disposed on the negative current collector 1, and the second coating 3 is disposed on the first coating 2, with the surface of the second coating 3 in contact with a solid electrolyte membrane. The first coating 2 comprises a carbon material and a first lithiophilic material, the first lithiophilic material comprising a lithiophilic metal oxide. The second coating 3 comprises a second lithiophilic material, the second lithiophilic material comprising at least one of a lithiophilic metal and a lithiophilic lithium alloy.

[0036] The carbon material and the first lithiophilic material uniformly composited in the first coating 2 form a porous or network-like substrate. The first lithiophilic material in the substrate utilizes its abundant oxygen vacancies to further reduce the lithium nucleation potential at the metal interface of the second coating 3, and provides multiple uniformly distributed lithium nucleation sites at the substrate to assist the second coating 3 in inducing the uniform deposition and spreading of active lithium at the negative electrode interface during the initial stage of charging. At the same time, the first lithiophilic material in the first coating 2 also provides a transport channel and storage space for lithium ions in the negative electrode, which can promote the uniform deposition and dissolution of lithium ions on the negative electrode during subsequent charge and discharge cycles, and further suppress the appearance of lithium dendrites on the negative electrode surface. Furthermore, the carbon material mixed with the first lithiophilic material in the first coating 2 can construct a highly conductive three-dimensional network structure in the substrate. On the one hand, the three-dimensional network structure can provide a buffer space to alleviate the volume change stress of the negative electrode sheet caused by lithium deposition / dissolution and prevent the negative electrode interface from peeling off during charging and discharging. On the other hand, it can improve the conductivity of the negative electrode sheet, rapidly transfer electrons during charging and discharging, avoid excessive accumulation of local current density in the negative electrode, reduce side reactions at the negative electrode interface, and prevent uneven charge distribution at the negative electrode sheet interface from inducing lithium dendrite growth.

[0037] As an interfacial coating that directly contacts the solid electrolyte, the second coating 3 provides a highly lithium-friendly negative electrode interface with better compatibility with the solid electrolyte. Based on the lithium alloying properties of the second lithium-friendly material, the second coating 3 can induce rapid and uniform nucleation growth of lithium ions at the negative electrode interface. On the other hand, by forming an alloy phase during cycling as a host for lithium deposition, it stabilizes the contact interface between the negative electrode and the solid electrolyte, reduces the occurrence of side reactions, and thus improves the battery cycle capacity.

[0038] In some embodiments, the mass content of the first lithiophilic material in the first coating is any value in the range of 4.5 wt% to 96 wt%, for example, the mass content of the first lithiophilic material in the first coating can be 4.5 wt%, 4.75 wt%, 5 wt%, 7 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or 96 wt%.

[0039] In some embodiments, the mass content of carbon material in the first coating is any value in the range of 0.95wt% to 92wt%, for example, the mass content of carbon material in the first coating can be 0.95wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, or 92wt%.

[0040] When the content of the first lithiophilic material and carbon material in the first coating is within the aforementioned mass content range, the negative electrode sheet can be guaranteed to have both good structural strength and lithiophilic and conductive properties. If the content of the first lithiophilic material in the first coating is too high and the content of carbon material is too low, it will lead to an increase in the resistance of the first coating, hindering electron transport in the negative electrode sheet, reducing rate performance, and consequently causing uneven current distribution at the negative electrode interface under high current density, increasing the risk of lithium dendrite growth at the negative electrode interface, and deteriorating the cycle life of the battery. If the content of the first lithiophilic material in the first coating is too low and the content of carbon material is too high, it will result in insufficient number of root lithium nucleation sites provided by the first coating of the negative electrode sheet, which will easily lead to localized lithium deposition at the negative electrode interface, also increasing the risk of lithium dendrite growth at the negative electrode interface and negatively impacting the cycle life of the battery.

[0041] In some embodiments, the thickness of the first coating is any value within the range of 100 nm to 10 μm, for example, the thickness of the first coating can be 100 nm, 200 nm, 500 nm, 700 nm, 1 μm, 3 μm, 5 μm, 7 μm, or 10 μm. When the thickness of the first coating is within the above-mentioned thickness range, the uniformity of lithium deposition at the negative electrode interface can be ensured without occupying too much battery space. If the thickness of the first coating is too thin, the negative electrode will lack a sufficient number of lithium nucleation sites and electron transport pathways at the bottom layer, causing lithium ion reduction during charging to preferentially occur in a few regions of the negative electrode interface, thereby inducing non-uniform lithium deposition at the negative electrode interface and increasing the risk of lithium dendrite growth. If the thickness of the first coating is too thick, although it will not worsen the uniform deposition process of active lithium at the negative electrode interface, it will lead to excessive coating load and a decrease in battery energy density.

[0042] In some embodiments, the thickness of the second coating is any value within the range of 50 nm to 5 μm. For example, the thickness of the second coating can be 50 nm, 100 nm, 500 nm, 700 nm, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. When the thickness of the second coating is within the above-mentioned range, the stability of the lithium-affinity interface between the negative electrode and the solid electrolyte membrane can be maintained while reducing space occupation. If the thickness of the second coating is too thin, it will affect the interfacial contact stability between the negative electrode and the solid electrolyte membrane, increase the interfacial impedance on the surface of the negative electrode, lead to non-uniform deposition of active lithium at the negative electrode interface, and increase the risk of lithium dendrite growth.

[0043] In some embodiments, the average particle size Dv50 of the first lithiophilic material is any value within the range of 1 nm to 1 μm. For example, the average particle size Dv50 of the first lithiophilic material can be 1 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 800 nm, or 1 μm. When the particle size of the first lithiophilic material is within the above range, a suitable size of the first lithiophilic material can enable the first coating to have a high specific surface area while providing dense and uniformly distributed lithium nucleation sites in the first coating. It can also utilize the gaps between nanoparticles to provide a shorter diffusion path for lithium ions, thereby helping lithium ions to diffuse and deposit rapidly and uniformly on the negative electrode, and effectively suppressing the formation of lithium dendrites at the negative electrode interface.

[0044] Optionally, the average particle size Dv50 of the first lithiophilic material can be any value within the range of 10 nm to 100 nm, such as 10 nm, 20 nm, 40 nm, 50 nm, 60 nm, 80 nm, or 100 nm. When the average particle size of the first lithiophilic material is within the above range, particle agglomeration leading to uneven particle distribution can be avoided, and more uniformly distributed lithium diffusion channels and nucleation sites can be provided, thereby improving the reaction kinetics of active lithium deposition and dissolution in the negative electrode, and further improving the cycle capacity and life of the battery.

[0045] In some embodiments, the areal density of the first coating is 0.05 mg / cm³. 2 ~2mg / cm 2 Any value within the range, for example, the areal density of the first coating can be 0.05 mg / cm³. 2 0.1 mg / cm 2 0.3 mg / cm 2 0.5 mg / cm 2 0.7 mg / cm 2 1mg / cm 2 1.3 mg / cm 2 1.5 mg / cm 2 1.7 mg / cm 2 Or 2mg / cm 2 .

[0046] In some embodiments, the average particle size Dv50 of the second lithiophilic material is any value within the range of 1 nm to 500 nm. For example, the average particle size Dv50 of the second lithiophilic material can be 1 nm, 5 nm, 10 nm, 30 nm, 50 nm, 70 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm. When the particle size of the second lithiophilic material is within the above range, the uniform distribution of lithiophilic particles in the second coating and the mechanical stability of the overall structure can be maintained. If the particle size of the second lithiophilic material is too small, the particles are prone to agglomeration in the second coating, affecting the uniformity of particle distribution in the second coating and the uniformity of lithium nucleation barrier at the lithiophilic contact interface. This can easily lead to excessive current accumulation in local areas during charging and discharging, thereby inducing the growth of lithium dendrites at the negative electrode interface and deteriorating the battery's cycle capacity and lifespan. If the particles of the second lithiophilic material are too large, they are prone to severe volume expansion and contraction during charge and discharge cycles, causing the second coating particles to rapidly pulverize and fail to achieve stable interfacial contact with the solid electrolyte membrane, resulting in rapid capacity decay of the battery.

[0047] Optionally, the average particle size Dv50 of the second lithiophilic material can be any value within the range of 1 nm to 50 nm, such as 1 nm, 3 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. When the particle size of the second lithiophilic material is within the above range, the arrangement of the second lithiophilic material in the second coating can be further optimized, improving the kinetic performance of the second coating in depositing or dissolving active lithium, thereby further improving the cycle life of the battery.

[0048] In some embodiments, the areal density of the second coating is 0.01 mg / cm³. 2 ~1mg / cm 2 Any value within the range, for example, the areal density of the second coating can be 0.01 mg / cm³. 2 0.05 mg / cm 2 0.1 mg / cm 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 0.9 mg / cm 2 or 1mg / cm 2 .

[0049] In some embodiments, the negative electrode current collector may be a foil material with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel or carbon; in addition to foil materials, the negative electrode current collector may also be any one or more of the following forms: film, mesh, porous, foam or non-woven fabric.

[0050] In some embodiments, the first lithiophilic material includes at least one of TiO2, ZnO, and SnO2. That is, the first lithiophilic material can be any one of the materials listed above, such as TiO2, ZnO, or SnO2; the first lithiophilic material can also be any combination of two or more of the materials listed above, for example, a combination of TiO2 and ZnO, or a combination of ZnO and SnO2, or a combination of TiO2 and SnO2, or a combination of TiO2, ZnO, and SnO2, etc., which will not be listed here one by one. When the first lithiophilic material is a combination of two or more materials, the proportion of each material within the combination is not limited, and they can be mixed in any proportion. In other embodiments, the first lithiophilic material can also be a material not listed above.

[0051] In some embodiments, the carbon material includes at least one of graphene, carbon nanotubes, hard carbon, soft carbon, carbon fiber, and carbon black. That is, the carbon material can be any one of the materials listed above, such as graphene, carbon nanotubes, hard carbon, soft carbon, carbon fiber, or carbon black; the carbon material can also be any combination of two or more of the materials listed above, for example, a combination of graphene and carbon nanotubes, or a combination of graphene and carbon fiber, or a combination of carbon black and carbon nanotubes, or a combination of hard carbon and carbon black, or a combination of graphene, carbon nanotubes, and carbon black, or a combination of hard carbon, graphene, and carbon black, etc., and not all will be listed here. When the carbon material is a combination of two or more materials, the proportion of each material within the combination is not limited, and they can be mixed in any proportion. In other embodiments, the carbon material can also be a material not listed above.

[0052] It should be noted that the second lithiophilic material can be any metal material capable of alloying with lithium, and its specific type is not limited. In some embodiments, the second lithiophilic material includes at least one of silver (Ag), aluminum (Al), gold (Au), zinc (Zn), tin (Sn), calcium (Ca), indium (In), lead (Pb), bismuth (Bi), magnesium (Mg), and lithium alloys of the above materials. The second lithiophilic material can be any of the materials listed above, such as silver, silver-lithium alloy, aluminum, aluminum-lithium alloy, gold, gold-lithium alloy, zinc, zinc-lithium alloy, tin, tin-lithium alloy, calcium, calcium-lithium alloy, indium, indium-lithium alloy, lead, lead-lithium alloy, bismuth, bismuth-lithium alloy, magnesium, or magnesium-lithium alloy. The second lithiophilic material can also be any combination of two or more of the materials listed above. For example, the second lithiophilic material can be a combination of Ag, Al and their lithium alloys, or a combination of Ag, Zn and their lithium alloys, or a combination of Au, Sn and their lithium alloys, or a combination of Al, In and their lithium alloys, or a combination of Pb, Mg and their lithium alloys, or a combination of Bi, Ca and their lithium alloys, or a combination of Ag, Zn, Mg and their lithium alloys, or a combination of Au, In and Bi and their lithium alloys, etc., and so on, which will not be listed here.

[0053] Optionally, in some embodiments, the second lithiophilic material includes at least one of silver, zinc, magnesium, and lithium alloys of the above materials. That is, the second lithiophilic material can be silver, zinc, magnesium, a silver-lithium alloy, a zinc-lithium alloy, or a magnesium-lithium alloy. The second lithiophilic material can also be a combination of Ag, Zn, and their lithium alloys, or a combination of Ag, Mg, and their lithium alloys, or a combination of Mg, Zn, Mg, and their lithium alloys, etc. It should be noted that when the second lithiophilic material is a combination of two or more materials, the proportion of each material within the combination is not limited, and they can be mixed in any proportion. In other embodiments, the second lithiophilic material can also be a material not listed above.

[0054] In some embodiments, the first coating and the second coating further comprise a negative electrode binder. In either the first coating or the second coating, the mass content of the negative electrode binder is 1 wt% to 5 wt%, for example, it can be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%. The negative electrode binder is selected from at least one of the following binder materials: polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), etc. Furthermore, the mass and mass content of the first lithiophilic material and the carbon material in the first coating are 95 wt% to 99 wt%, and the mass ratio of the first lithiophilic material to the carbon material is (5-99):(1-95).

[0055] In a second aspect, the present invention also provides a method for preparing the negative electrode sheet in any of the above embodiments, such as... Figure 2 As shown, the preparation method of this negative electrode sheet includes the following steps:

[0056] S1. Provide a negative electrode current collector and form a first coating on the negative electrode current collector; the first coating includes a carbon material and a first lithiophilic material, wherein the first lithiophilic material includes a lithiophilic metal oxide;

[0057] S2. A second coating is formed on the first coating to obtain a negative electrode sheet; the second coating includes a second lithiophilic material, the second lithiophilic material including a lithiophilic metal and / or a lithium alloy of the lithiophilic metal.

[0058] In some embodiments, step S1 includes the following steps:

[0059] S11. The first lithiophilic material, carbon material and binder are uniformly mixed to form the first slurry.

[0060] In step S11, the first lithiophilic material and the carbon material are first uniformly mixed to obtain a mixed coating material; then the mixed coating material, the negative electrode binder, and deionized water are mixed to form a first slurry. In the first slurry, the mass ratio of the first lithiophilic material, the carbon material, and the negative electrode binder is (4.5~95):(1~92):(1~4).

[0061] The first lithiophilic material is selected from at least one of TiO2, ZnO and SnO2; the carbon material is selected from at least one of graphene, carbon nanotubes, hard carbon, soft carbon, carbon fiber and carbon black; and the negative electrode binder is selected from at least one of polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol and styrene-butadiene rubber.

[0062] S12. The first slurry is uniformly coated on the surface of the negative electrode current collector; the negative electrode current collector coated with the first slurry is heated and dried to form a first coating on the surface of the negative electrode current collector.

[0063] In step S12, the method of transferring the first slurry to the surface of the negative electrode current collector is not limited. For example, the first slurry can be coated on the surface of the negative electrode current collector by magnetron sputtering, spraying or scraping.

[0064] In some embodiments, in step S2, a second lithiophilic material is further coated or deposited on the first coating on the surface of the negative electrode current collector to form a second coating on the surface of the first coating, thereby forming a negative electrode sheet. The second lithiophilic material is selected from at least one of silver, aluminum, gold, zinc, tin, calcium, indium, lead, bismuth, magnesium, and their lithium alloys.

[0065] In step S2, the method of forming the second coating on the negative electrode current collector is not limited. The second coating can be formed on the first coating of the negative electrode current collector by magnetron sputtering, vapor deposition, electrochemical deposition, spraying, or scraping. For example, in one example, the second lithiophilic material is directly deposited on the surface of the negative electrode current collector by magnetron sputtering, vapor deposition, or electrochemical deposition to form the second coating on the surface of the first coating. Alternatively, in another example, the second lithiophilic material, the negative electrode binder, and deionized water can be uniformly mixed to obtain a second slurry; then, the second slurry is sprayed or scraped onto the surface of the first coating of the negative electrode current collector, and after heating and drying, the second slurry forms the second coating on the negative electrode current collector to obtain the negative electrode sheet. The mass ratio of the second lithiophilic material to the negative electrode binder in the second slurry is (96-99):(1-4).

[0066] In a third aspect, the present invention also provides a solid-state battery, which can be a solid-state lithium-ion secondary battery. The solid-state battery includes a positive electrode, a solid electrolyte membrane, and a negative electrode as described in any of the above embodiments. The solid electrolyte membrane is disposed between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode, and serves as a lithium-ion conductor between the positive electrode and the negative electrode.

[0067] The solid electrolyte membrane can be any solid electrolyte membrane used in various systems in the art. For example, in some embodiments, the solid electrolyte membrane includes a solid electrolyte and a membrane binder, wherein the mass ratio of the solid electrolyte to the membrane binder in the solid electrolyte membrane is (90-100):(0.5-10). The solid electrolyte is selected from at least one of sulfide electrolytes, halide electrolytes, oxide electrolytes, and polymer electrolytes, and the membrane binder is selected from any one of nitrile rubber (NBR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and linear triblock copolymers, or a combination of several of these in any proportion.

[0068] The positive electrode can be a positive electrode used in various systems in this field.

[0069] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector. The positive active material layer includes a positive active material, a positive binder, a positive conductive agent, and a solid electrolyte. The preparation process of this type of positive electrode sheet is as follows: the positive active material, solid electrolyte, positive conductive agent, and positive binder are mixed in a mass ratio of (70-90):(5-25):(1-5):(1-3), and the solvent N-methylpyrrolidone (NMP) is added. Then, the mixture is thoroughly stirred under vacuum to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated onto the positive current collector, and the positive current collector is dried at room temperature and then transferred to an oven for drying. Finally, the positive electrode sheet is obtained by cold pressing and slitting.

[0070] The positive electrode current collector can be made of foil with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel or carbon. In addition to foil, the positive electrode current collector can also be made of any one or more of the following forms: film, mesh, porous, foam or non-woven fabric.

[0071] The positive electrode active material is selected from one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), and lithium-rich manganese oxide (LRMO).

[0072] The solid electrolyte is selected from at least one of sulfide electrolytes, halide electrolytes, oxide electrolytes and polymer electrolytes.

[0073] The positive electrode conductive agent is selected from one or a combination of carbon black, Ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, porous carbon, etc. In one example, the positive electrode conductive agent includes carbon black and carbon nanofibers, and the mass ratio of carbon black to carbon nanofibers is 1:(0.2 to 1.5).

[0074] The positive electrode binder is selected from, for example, any one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer, or a combination of several of these in any proportion.

[0075] An example of the assembly method for solid-state batteries is described: a solid electrolyte is cold-pressed under a pressure of 300-400 MPa to obtain a solid electrolyte membrane with a thickness of 100-500 μm; the positive electrode, the solid electrolyte membrane, and the negative electrode are stacked and pressed together to obtain a battery cell; the pressed battery cell is sealed and packaged under a vacuum or inert atmosphere to obtain a solid-state lithium-ion battery.

[0076] The technical solution of the present invention will be described in detail below through several specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by conventional methods in the art.

[0077] Example 1

[0078] This embodiment provides a solid-state battery, which includes a positive electrode, a solid electrolyte membrane, and a negative electrode. The negative electrode includes a negative current collector and a first coating and a second coating sequentially disposed on the current collector. The first coating includes a first lithiophilic material, a carbon material, and a binder; the second coating includes a second lithiophilic material. Specifically, the first lithiophilic material is TiO2 with a Dv50 of 50 nm and a mass content of 4.8 wt% in the first coating; the carbon material is carbon nanotubes (CNTs) with a mass content of 91.2 wt% in the first coating; the binder is PAA with a mass content of 4 wt% in the first coating; and the second lithiophilic material is Ag with a Dv50 of 20 nm.

[0079] The preparation process of this negative electrode sheet is as follows:

[0080] (1) The first lithiophilic material TiO2 and the carbon material CNT are dry-mixed for 2 hours at a mass ratio of 5:95 to obtain a mixed coating material; then the mixed coating material, binder and deionized water are mixed evenly at a mass ratio of 50:2:48 to obtain the first slurry.

[0081] (2) The first slurry is coated on the surface of the copper negative electrode current collector, and after drying, a first coating with a thickness of 5μm is formed on the surface of the negative electrode current collector.

[0082] (3) Mix the second lithiophilic material Ag, binder PAA and deionized water in a mass ratio of 55:2:43 to obtain the second slurry.

[0083] (4) The second slurry is uniformly sprayed onto the first coating layer and dried to form a second coating layer with a thickness of 2μm on the first coating layer to obtain the negative electrode sheet.

[0084] The assembly and fabrication process of this solid-state battery is as follows:

[0085] Preparation of solid electrolyte membrane: Under an argon atmosphere, 2 mol Li₂S, 1.5 mol LiCl, 0.48 mol P₂S₅, and 0.02 mol Sb₂O₅ were added to a ball mill jar at a ball-to-material ratio of 30:1 and a rotation speed of 500 rpm for 20 hours. The resulting electrolyte precursor powder was then sintered at 500℃ for 10 hours to obtain Li₂O₅. 5.5 P0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 Sulfide electrolyte; 50 mg of sulfide electrolyte was cold-pressed under a pressure of 360 MPa to prepare a solid electrolyte membrane with a thickness of 300 μm and a diameter of 10 mm.

[0086] Positive electrode preparation: The positive electrode active material LiNi is prepared... 0.8 Co 0.1 Mn 0.1 O2, positive electrode conductive agent (super-P and VGCF mixed conductive agent in a mass ratio of 1:1), the above-mentioned sulfide electrolyte, and positive electrode binder PTFE are mixed in a mass ratio of 69:1:29:1 to form a positive electrode slurry. The positive electrode slurry is then combined with the positive electrode current collector aluminum foil using a dry method and cut into circular pieces with a diameter of 10mm to obtain the positive electrode sheet.

[0087] Assembly process: The negative electrode sheet prepared above is cut into a circular sheet with a diameter of 10mm. The positive electrode sheet, solid electrolyte membrane and the cut negative electrode sheet are placed into a mold sleeve and pressed and packaged under a pressure of 100Mpa to obtain a solid-state battery.

[0088] Example 2

[0089] This embodiment provides a solid-state battery with the same system as that in Embodiment 1. The difference between this embodiment and Embodiment 1 is that in the negative electrode preparation step (1), the mass ratio of the first lithiophilic material TiO2 to the carbon material CNT is 50:50, so that the mass content of the first lithiophilic material in the first coating of the negative electrode is 48wt% and the mass content of the carbon material is 48wt%.

[0090] Example 3

[0091] This embodiment provides a solid-state battery with the same system as that in Embodiment 1. The difference between this embodiment and Embodiment 1 is that in the negative electrode preparation step (1), the mass ratio of the first lithiophilic material TiO2 to the carbon material CNT is 70:30, so that the mass content of the first lithiophilic material in the first coating of the negative electrode is 67wt% and the mass content of the carbon material is 29wt%.

[0092] Example 4

[0093] This embodiment provides a solid-state battery with the same system as that in Embodiment 1. The difference between this embodiment and Embodiment 1 is that in the negative electrode preparation step (1), the mass ratio of the first lithiophilic material TiO2 to the carbon material CNT is 99:1, so that the mass content of the first lithiophilic material in the first coating of the negative electrode is 95.2 wt% and the mass content of the carbon material is 0.96 wt%.

[0094] Example 5

[0095] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the first lithiophilic material is ZnO.

[0096] Example 6

[0097] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the first lithiophilic material is SnO2.

[0098] Example 7

[0099] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that hard carbon (HC) is used as the carbon material.

[0100] Example 8

[0101] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the carbon material used is vapor-grown carbon fiber (VGCF).

[0102] Example 9

[0103] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the first lithiophilic material TiO2 is 1 nm.

[0104] Example 10

[0105] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the first lithiophilic material TiO2 is 10nm.

[0106] Example 11

[0107] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the first lithiophilic material TiO2 is 100nm.

[0108] Example 12

[0109] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the first lithiophilic material TiO2 is 1 μm.

[0110] Example 13

[0111] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the first lithiophilic material TiO2 is 3 μm.

[0112] Example 14

[0113] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 50 nm.

[0114] Example 15

[0115] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 100 nm.

[0116] Example 16

[0117] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 1 μm.

[0118] Example 17

[0119] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the first coating is 10 μm.

[0120] Example 18

[0121] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the second lithiophilic material is Zn.

[0122] Example 19

[0123] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the second lithiophilic material is Mg.

[0124] Example 20

[0125] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the second lithiophilic material Ag is 1 nm.

[0126] Example 21

[0127] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the second lithiophilic material Ag is 50 nm.

[0128] Example 22

[0129] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the second lithiophilic material Ag is 100 nm.

[0130] Example 23

[0131] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the second lithiophilic material Ag is 500 nm.

[0132] Example 24

[0133] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the Dv50 of the second lithiophilic material Ag is 1 μm.

[0134] Example 25

[0135] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the second coating is 20 nm.

[0136] Example 26

[0137] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the second coating is 50 nm.

[0138] Example 27

[0139] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the second coating is 1 μm.

[0140] Example 28

[0141] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that the thickness of the second coating is 5 μm.

[0142] Example 29

[0143] This embodiment provides a solid-state battery with the same system as Example 3. The difference between this embodiment and Example 3 is that the sulfide electrolyte used in the solid-state battery is Li₂S prepared by 2.02 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.01 mol In₂O₃. 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.5 .

[0144] Example 30

[0145] This embodiment provides a solid-state battery with the same system as Example 3. The difference between this embodiment and Example 3 is that the sulfide electrolyte used in the solid-state battery is Li₂S prepared by 2.02 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.01 mol Bi₂O₃. 5.54 P 0.98 Bi 0.02 S 4.47 O 0.03 Cl 1.5 .

[0146] Example 31

[0147] This embodiment provides a solid-state battery with the same system as Example 3. The difference between this embodiment and Example 3 is that the sulfide electrolyte used in the solid-state battery is Li₂S prepared by 2.03 mol Li₂S, 1.5 mol LiCl, 0.49 mol P₂S₅, and 0.02 mol MgO. 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.5 .

[0148] Example 32

[0149] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the sulfide electrolyte used in the solid-state battery is Li₂S prepared by 2 mol Li₂S, 1.5 mol LiCl, and 0.5 mol P₂S₅. 5.5 PS 4.5 Cl 1.5 .

[0150] Comparative Example 1

[0151] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the negative electrode sheet uses bare negative electrode current collector copper foil.

[0152] Comparative Example 2

[0153] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the negative electrode sheet does not have a first coating on the negative electrode current collector, but only has a second coating on the surface of the negative electrode current collector.

[0154] Comparative Example 3

[0155] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the negative electrode sheet does not have a second coating on the negative electrode current collector, but only has a first coating on the surface of the negative electrode current collector.

[0156] Comparative Example 4

[0157] This embodiment provides a solid-state battery with the same system as Embodiment 3. The difference between this embodiment and Embodiment 3 is that the first coating includes a second lithiophilic material Ag, the Dv50 of which is 20 nm, and the thickness of the first coating is 2 μm; the second coating includes a first lithiophilic material TiO2, a carbon material CNT, and a binder PAA, the thickness of which is 5 μm, the Dv50 of which is 50 nm, the mass content of which is 67 wt%, and the mass content of which is 29 wt%.

[0158] The solid-state batteries prepared in Examples 1 to 32 and Comparative Examples 1 to 4 were subjected to cycle performance tests to verify the effect of the negative electrode on improving the cycle performance of the battery. The test results are shown in Table 1.

[0159] The solid-state battery cycle performance test process is as follows: Solid-state batteries were prepared for Examples 1 to 32 and Comparative Examples 1 to 4 at 25°C. The batteries were capacitively charged with a current of 0.6mA. After capacitive charging, the solid-state batteries were charged and discharged at a current rate of 1C / 1C within the operating voltage range of 2.5 to 4.3V. During the charge and discharge cycle, the specific capacity of the first charge cycle and the number of cycles when the SOH capacity was less than or equal to 80% of the initial capacity were recorded.

[0160] Table 1: Parameters of negative electrode sheets prepared in Examples 1 to 32 and Comparative Examples 1 to 4, and performance test results of assembled batteries.

[0161]

[0162]

[0163] Comparing the test results of Examples 1 to 31 and Comparative Example 1, it can be seen that, compared with the negative electrode sheet using only bare copper foil in Comparative Example 1, the negative electrode sheet using a double-layer lithium-loving coating structure in the present invention can effectively suppress the formation of lithium dendrites on the negative electrode surface, reduce the loss of active lithium and the increase in impedance caused by side reactions and dead lithium in the negative electrode sheet, and reduce the risk of short circuit in the battery during cycling, thereby significantly improving the cycle life of the solid-state battery.

[0164] Comparing the test results of Examples 1 to 17 and Comparative Example 2, it can be seen that, due to the lack of a first coating, the negative electrode current collector in Comparative Example 2 loses its underlying mechanical support substrate, electronic conduction framework, and root lithium nucleation sites. This leads to the negative electrode being prone to uneven surface current distribution during cycling, making it difficult to effectively control lithium dendrite growth. Furthermore, excessive electrode deformation can cause interface peeling at the negative electrode coating interface, resulting in a sharp deterioration in battery cycle life. In contrast to Comparative Example 2, the negative electrode in this embodiment utilizes a balanced mixture of a first lithiophilic material and a carbon material in the first coating, providing a substrate with both good conductivity and mechanical strength, and providing multiple uniformly distributed lithium nucleation sites within the substrate. The first coating in the negative electrode can prevent uneven current density distribution at the negative electrode interface during battery cycling, promote uniform spreading of active lithium at the negative electrode interface, and inhibit the formation of lithium dendrites at the negative electrode interface. Simultaneously, it reduces volume deformation of the negative electrode due to lithium deposition / dissolution, preventing interface peeling and thus significantly improving battery cycle life.

[0165] Comparing the test results of Examples 3, 9 to 28 and Comparative Example 3, it can be seen that if the negative electrode sheet in Comparative Example 3 lacks a second coating, the negative electrode sheet lacks a highly lithium-affinity trapping layer and a uniform lithium deposition spreading platform on its surface, resulting in poor lithium deposition uniformity during the initial charging stage; and the first coating with oxide lithium-affinity material will be directly exposed to the electrolyte interface, affecting the long-term stability of the negative electrode interface, and side reactions are prone to occur during long-term cycling, thereby reducing battery impedance and capacity.

[0166] Comparing the test results of Example 3 and Comparative Example 4, it can be seen that if a second lithiophilic material is placed in the first coating of the negative electrode sheet, and a first lithiophilic material and carbon material are placed in the second coating, the lithium nucleation potential of the bottom coating of the negative electrode sheet will be higher than that of the top coating. This will hinder the deposition of active lithium in the bottom layer during charging and discharging, making it difficult to fully utilize the capacity-enhancing effect of the double-layer coating structure. At the same time, it will also cause the oxide lithiophilic material to be directly exposed to the electrolyte interface, making it impossible to protect the oxide lithiophilic material. This will lead to an increase in side reactions under long-term cycling, which will have a negative impact on battery impedance and cycle life.

[0167] Comparing the test results of Examples 1 to 4, it can be seen that the mass content of the first lithiophilic material and the carbon material in the first coating has a crucial impact on the battery cycle performance. If the mass content of the first lithiophilic material in the first coating is too low and the mass content of the carbon material is too high, it will lead to insufficient lithiophilic sites provided by the negative electrode substrate, resulting in uneven lithium deposition during cycling, which increases the probability of lithium dendrite formation and affects the battery cycle life. If the mass content of the first lithiophilic material in the first coating is too high and the mass content of the carbon material is too low, it will lead to increased impedance of the negative electrode, hindering electron transport. The negative electrode is prone to uneven current distribution under high-rate current, which in turn exacerbates the risk of local lithium dendrite formation and affects battery life.

[0168] Comparing the test results of Examples 9 to 13, it can be seen that when the Dv50 of the first lithiophilic material is within the suitable range of 10nm to 100nm, the cycle performance of the battery can reach its optimal level. If the Dv50 of the first lithiophilic material is too small, the extremely small particles of the first lithiophilic material are prone to agglomeration, resulting in uneven particle distribution in the first coating, affecting the uniformity of lithium nucleation sites provided by the first coating, and increasing the risk of lithium dendrite formation. If the Dv50 of the first lithiophilic material is too large, the specific surface area of ​​the first coating will be low, and the number of lithium nucleation sites provided by the first coating will be relatively small, which will easily lead to uneven lithium deposition, increase the risk of lithium dendrite formation, and also increase the diffusion path of lithium ions between large particles, slowing down nucleation and reaction kinetics, and affecting the deposition and dissolution rate of active lithium on the negative electrode.

[0169] Comparing the test results of Examples 14 to 17, it can be seen that when the thickness of the first coating is within a suitable range of 100 nm to 10 μm, it can optimize both battery capacity and cycle life, resulting in optimal battery cycle performance. If the thickness of the first coating is too thin, the negative electrode sheet will lack a sufficient number of lithium nucleation sites and electron transport pathways at the bottom layer. This will cause lithium ion reduction during charging to preferentially occur in a few regions of the negative electrode interface, thereby inducing non-uniform lithium deposition at the negative electrode interface and increasing the risk of lithium dendrite growth. If the thickness of the first coating is too thick, although it will not worsen the uniform deposition process of active lithium at the negative electrode interface, it will lead to excessive coating load and a decrease in battery energy density.

[0170] Comparing the test results of Examples 20 to 24, it can be seen that when the Dv50 of the second lithiophilic material is within the suitable range of 1nm to 50nm, the cycle performance of the battery can reach its optimal level. If the Dv50 of the second lithiophilic material is too small, the particles of the second lithiophilic material are prone to agglomeration in the second coating, affecting the uniformity of particle distribution in the second coating and the uniformity of lithium nucleation barrier at the lithiophilic contact interface. This can easily lead to the accumulation of excessive current in local areas during charging and discharging, thereby inducing the growth of lithium dendrites at the negative electrode interface and deteriorating the cycle capacity and lifespan of the battery. If the Dv50 of the second lithiophilic material is too large, severe volume expansion and contraction can easily occur during charge and discharge cycles, causing the particles of the second coating to pulverize rapidly and failing to achieve stable interfacial contact with the solid electrolyte membrane, resulting in rapid capacity decay of the battery.

[0171] Comparing the test results of Examples 25 to 28, it can be seen that when the thickness of the second coating is within a suitable range of 50 nm to 5 μm, the stability of the lithium-affinity interface between the negative electrode and the solid electrolyte membrane can be maintained while minimizing space occupation, thereby further improving battery cycle performance. If the thickness of the second coating is too thin, it will affect the stability of the interface between the negative electrode and the solid electrolyte membrane, increase the interfacial impedance of the negative electrode surface, and lead to non-uniform deposition of active lithium at the negative electrode interface, increasing the risk of lithium dendrite growth. If the thickness of the second coating is too thick, it will result in excessive coating load, affecting the battery energy density.

[0172] Comparing the test results of Examples 3, 29 to 31, and Example 32, it can be seen that the battery cycle performance deteriorates when the sulfide electrolyte used in the solid-state battery is not doped with elements such as Sb, In, Bi, and Mg, while the battery cycle performance is significantly improved after doping with elements such as Sb, In, Bi, and Mg. This is because the doping modification of the sulfide electrolyte can improve the interfacial chemical and physical contact between the sulfide electrolyte and the electrode, suppress the occurrence of interfacial side reactions, form a stable interfacial layer, thereby reducing interfacial impedance and improving the cycle life and power performance of the battery.

[0173] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A negative electrode sheet, characterized by, The negative electrode current collector comprises: a negative electrode current collector; a first coating layer disposed on the negative electrode current collector, the first coating layer comprising a carbon material and a first lithiumophilic material, the first lithiumophilic material comprising a lithiumophilic metal oxide; a second coating layer disposed on the first coating layer, the second coating layer comprising a second lithiumophilic material, the second lithiumophilic material comprising a lithiumophilic metal and / or a lithium alloy of the lithiumophilic metal.

2. The negative electrode sheet according to claim 1, characterized by The first lithiumophilic material comprises at least one of TiO2, ZnO, and SnO2; and / or, the second lithiumophilic material comprises at least one of Ag, Al, Au, Sn, Zn, Ca, In, Pb, Bi, Mg, or a lithium alloy of the above materials.

3. The negative electrode sheet according to claim 2, characterized by The second lithiumophilic material comprises at least one of Ag, Zn, Mg, or a lithium alloy of the above materials.

4. The negative electrode sheet according to claim 1, wherein The thickness of the first coating layer is 100 nm to 10 μm; and / or, the thickness of the second coating layer is 50 nm to 5 μm.

5. The negative electrode sheet according to claim 1, wherein The first lithiumophilic material has an average particle size of 1 nm to 1 μm; and / or the first coating has an areal density of 0.05 mg / cm 2 to 2 mg / cm 2 .

6. The negative electrode sheet according to claim 1, wherein The average particle size of the second lithiophilic material is 1 nm to 500 nm; and / or, the areal density of the second coating is 0.01 mg / cm 2 ~ 1 mg / cm 2 .

7. The negative electrode sheet according to claim 1, wherein The first coating layer further comprises a binder, the mass content of the binder in the first coating layer is 1 wt% to 5 wt%, the mass content of the first lithiumophilic material and the carbon material in the first coating layer is 95 wt% to 99 wt%, and the mass ratio of the first lithiumophilic material to the carbon material is (5-99):(1-95); and / or, the mass content of the first lithiumophilic material in the first coating layer is 4.5 wt% to 96 wt%, and the mass content of the carbon material in the first coating layer is 0.95 wt% to 92 wt%.

8. The negative electrode plate of claim 1, wherein, The carbon material comprises at least one of graphene, carbon nanotubes, hard carbon, soft carbon, carbon fibers, and carbon black.

9. A method for producing the negative electrode sheet according to any one of claims 1 to 8, characterized by, The negative electrode current collector comprises: forming a first coating layer on the negative electrode current collector; The first coating layer comprises a carbon material and a first lithiumophilic material, the first lithiumophilic material comprising a lithiumophilic metal oxide; forming a second coating layer on the first coating layer to obtain a negative electrode tab, the second coating layer comprising a second lithiumophilic material, the second lithiumophilic material comprising a lithiumophilic metal and / or a lithium alloy of the lithiumophilic metal.

10. A solid state battery, characterized by The negative electrode tab comprises any one of claims 1 to 8, or is prepared by the preparation method of claim 9.

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