Negative pole piece, preparation method thereof and all-solid-state sulfide battery

Abstract

The invention provides a negative pole piece and a preparation method thereof and an all-solid-state sulfide battery, the negative pole piece comprises a lithium-loving coating, a negative pole material layer and a negative pole current collector, the lithium-loving coating comprises a lithium-loving active substance, a first binder and a first conductive agent, and the negative pole material layer comprises a lithium-silicon alloy, a sulfide electrolyte and a second binder, a plurality of through holes are formed in the negative electrode current collector, the lithium-loving coating, the negative electrode current collector and the negative electrode material layer are sequentially stacked, and the all-solid-state sulfide battery prepared from the negative electrode piece has the advantages that the first coulombic efficiency is high, the capacity fading is slow, and short circuit cannot occur when the all-solid-state sulfide battery is matched with a high-surface-capacity positive electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a negative electrode sheet, a preparation method thereof and a full-solid sulfide battery. BACKGROUND

[0002] Currently, lithium ion battery technology is at the forefront of a profound transformation. This transformation is driven by two major innovations: one is the replacement of graphite negative electrode, which has reached the theoretical limit, with a higher energy density negative electrode material; the other is the replacement of traditional organic liquid electrolyte with solid-state electrolyte. The combination of silicon-based negative electrode and solid-state battery technology is the intersection of these two frontiers, and is considered as the “match made in heaven” to break through the performance bottleneck of the next generation of batteries.

[0003] Silicon-based negative electrodes are known for their extremely high theoretical specific capacity (4200 mAh / g), but their industrial application has always been limited by a fatal weakness: a huge volume expansion (>300%) during charging and discharging. This expansion can cause silicon particles to break away from the current collector, resulting in a sharp decline in capacity. The core advantage of pre-lithiated lithium-silicon alloy is that it solves the two problems of low first efficiency and severe volume expansion of silicon negative electrodes by completing the “lithium supplementation” and “alloying” of silicon before battery assembly, making it possible to prepare high-energy-density, long-life batteries.

[0004] However, in the practical application of sulfide full-solid-state batteries, lithium-silicon alloy prepared by ball milling lithium powder with silicon will have residual lithium metal that has not been completely alloyed with silicon. The residual lithium not only reacts with the sulfide electrolyte, causing the internal resistance to increase, the capacity to rapidly decay, and the service life to be significantly shortened, but also easily causes short circuit problems when matching high-area-capacity cathodes. In view of the characteristics of lithium-silicon alloy, one solution is to redesign and increase the capacity of the negative electrode relative to the positive electrode (i.e., increase the N / P ratio), but this will sacrifice the overall energy density of the full battery, which is contrary to the original intention of using silicon. Therefore, there is an urgent need for a solid-state battery negative electrode sheet with high first efficiency, low volume expansion, and the ability to match high-area-capacity positive electrodes.

[0005] CONTENT The technical problem to be solved by the present application is to provide a negative electrode sheet, a preparation method thereof and a full-solid-state sulfide battery, which can improve the problem of easy short circuit and rapid capacity decay when high-area-capacity positive electrodes are matched with lithium-silicon alloy negative electrodes.

[0006] The application provides a negative electrode sheet, comprising: a lithiumophilic coating, comprising: a lithiumophilic active material, a first binder and a first conductive agent; a negative electrode material layer, comprising: a lithium-silicon alloy, a sulfide electrolyte and a second binder; and a negative electrode current collector, a plurality of through holes are provided on the negative electrode current collector, wherein the lithiumophilic coating, the negative electrode current collector and the negative electrode material layer are stacked in sequence.

[0007] Further, the mass fraction of the lithiumophilic active substance is 60% - 90%, the mass fraction of the first binder is 5% - 20%, and the mass fraction of the first conductive agent is 5% - 20%, based on the total weight of the lithiumophilic coating.

[0008] Further, the mass fraction of the lithium-silicon alloy is 80% - 95%, the mass fraction of the sulfide electrolyte is 2% - 18%, and the mass fraction of the second binder is 2% - 10%, based on the total weight of the negative electrode material layer.

[0009] Further, the negative electrode material layer further comprises a second conductive agent, and the mass fraction of the second conductive agent is less than 10%, and the second conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, and carbon nanofibers.

[0010] Further, the lithiumophilic active substance is selected from at least one of zinc oxide (ZnO), cobalt monoxide (CoO), iron oxide (Fe2O3), copper oxide (CuO), nickel oxide (NiO), cobalt nitride (Co4N), iron nitride (Fe4N), and zinc.

[0011] Further, the first binder and the second binder are both selected from at least one of styrene ethylene butylene styrene copolymer, ethylene butadiene rubber, butadiene rubber, polyisobutylene, nitrile butadiene rubber, polytetrafluoroethylene, polyvinyl acetate, polyvinyl butyral, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, carboxymethyl fiber, polyacrylonitrile, styrene-butadiene-styrene block copolymer, styrene-ethylene / propylene-styrene block copolymer, and polyacrylic acid.

[0012] Further, the first conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, and carbon nanofibers.

[0013] Further, the plurality of holes on the negative electrode current collector are uniformly distributed.

[0014] Further, the porosity of the negative electrode current collector is 20% - 70%.

[0015] Further, the porosity of the negative electrode current collector is 35% - 60%.

[0016] Further, the sulfide electrolyte is selected from Li2S-SiS2, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li4SnS4·LiI, 90(0.8Li2S-0.2P2S5)·5LiI, 80Li2S-20P2S5, Li3PS4, Li7P3S 11 , 9Li2S·3P2S5·Ni3S2, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li5.5 PS 4.5 Cl 1.5 Li 5.7 PS 4.7 C l1.3 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 6.6 Ge 0.6 P 0.4 At least one of S5I.

[0017] Furthermore, the particle size of the sulfide electrolyte is 200nm-1000nm.

[0018] This application also provides a method for preparing the above-mentioned negative electrode sheet, comprising the following steps: adding a predetermined mass of a first binder, a conductive agent, a lithiophilic active material, and the first binder sequentially to pure water and stirring to obtain a lithiophilic coating slurry; adding a predetermined mass of a second binder and a non-aqueous solvent, a predetermined mass of a sulfide electrolyte and a non-aqueous solvent, a predetermined mass of a second conductive agent and a non-aqueous solvent, and a predetermined mass of a lithium-silicon alloy and a non-aqueous solvent sequentially to a container and stirring to obtain a negative electrode slurry; coating the lithiophilic coating slurry on one side of a porous negative electrode current collector, and coating the negative electrode slurry on the other side of the negative electrode current collector to obtain a negative electrode sheet.

[0019] Furthermore, the non-aqueous solvent is selected from at least one of anisole, isobutyl isobutyrate, toluene, xylene, methyl acetate, ethyl acetate, hexane, and n-heptane.

[0020] Furthermore, the thickness of the lithium-philic coating slurry coated on the negative electrode current collector is 80um-120um, and the thickness of the negative electrode slurry coated on the negative electrode current collector is 160um-240um.

[0021] This application also provides an all-solid-state sulfide battery, comprising: a positive electrode, a negative electrode, and a sulfide electrolyte layer disposed therebetween, wherein the negative electrode is the aforementioned negative electrode sheet, or the negative electrode is prepared by the aforementioned method.

[0022] The beneficial effects of this application are: The negative electrode sheet of the present application is provided with a plurality of holes on the negative electrode current collector, and a negative electrode material layer is coated on one side of the negative electrode current collector, and a lithiumophilic coating layer is coated on the other side, so that the lithiumophilic active substance of the lithiumophilic coating layer can capture the metallic lithium in the negative electrode material layer, avoid the reaction of the metallic lithium with the sulfide electrolyte, and the reaction product can provide a more superior nucleation site in energy for lithium deposition, and the reaction product is uniformly distributed, which is equivalent to uniformly distributing countless "lithium deposition guide points", which can make lithium deposit uniformly, so that local aggregation of lithium and growth of dendrites can be avoided, and the elemental lithium after reaction cannot re-embed into the negative electrode, so that the full solid-state sulfide battery prepared from the negative electrode sheet of the present application has high initial coulombic efficiency, slow capacity attenuation, and will not short circuit when matching a high surface capacity positive electrode. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only related to some embodiments of the present disclosure, but not limit the present disclosure.

[0024] Figure 1 The structure diagram of the negative electrode sheet in the embodiments of the present disclosure. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present disclosure.

[0026] Unless otherwise defined, the technical terms or scientific terms used herein should be understood as the usual meanings understood by those of ordinary skill in the art to which the present disclosure belongs. The "first", "second" and similar words used in the specification and claims of the present patent application do not represent any order, quantity or importance, but are only used to distinguish different components.

[0027] Definitions of other specific words and phrases are provided throughout this disclosure. Those of ordinary skill in the art will appreciate that in many, if not most, instances, such definitions apply to prior and future uses of such defined words and phrases.

[0028] Figure 1 The structure diagram of the negative electrode sheet in the embodiments of the present disclosure.

[0029] The present disclosure provides a negative electrode sheet 100. As shown in Figure 1As shown, the negative electrode tab 100 includes: a lithiumophilic coating layer 10, a negative electrode material layer 20, and a negative electrode current collector 30. The lithiumophilic coating layer 10 includes: a lithiumophilic active substance, a first binder, and a first conductive agent. The negative electrode material layer 20 includes: a lithium-silicon alloy, a sulfide electrolyte, and a second binder. A plurality of through holes are provided on the negative electrode current collector 30. The lithiumophilic coating layer 10, the negative electrode current collector 30, and the negative electrode material layer 20 are sequentially stacked.

[0030] The negative electrode tab provided by the above-mentioned embodiments of the present disclosure.

[0031] In some embodiments, the mass fraction of the lithiumophilic active substance is 60%-80%, the mass fraction of the first binder is 15%-20%, and the mass fraction of the first conductive agent is 5%-20%, based on the total mass of the lithiumophilic coating layer.

[0032] In some embodiments, the mass fraction of the lithium-silicon alloy is 80%-95%, the mass fraction of the sulfide electrolyte is 2%-18%, and the mass fraction of the second binder is 2%-10%, based on the total mass of the negative electrode material layer.

[0033] In some embodiments, the negative electrode material layer further includes a second conductive agent, and the mass fraction of the second conductive agent is less than 10%.

[0034] In some embodiments, the lithiumophilic active substance is selected from at least one of zinc oxide (ZnO), cobalt suboxide (CoO), iron oxide (Fe2O3), copper oxide (CuO), nickel oxide (NiO), cobalt nitride (Co4N), and iron nitride (Fe4N).

[0035] When the lithiumophilic active substance is zinc oxide, cobalt oxide, iron oxide, copper oxide, nickel oxide, cobalt nitride (Co4N), or iron nitride (Fe4N), the lithiumophilic active substance will undergo a conversion reaction with lithium in the negative electrode material layer to generate lithium oxide or lithium nitride and nano-metal particles (zinc, copper, nickel, cobalt, or iron), and the generated nano-metal particles are uniformly distributed, which is equivalent to uniformly distributing countless "lithium deposition guide points", and can enable lithium to be uniformly deposited, avoiding local aggregation and dendrite growth of lithium; and the lithium oxide or lithium nitride can form a stable interface, which is a key to ensuring ion transmission, and the lithium element in the lithium oxide or lithium nitride cannot re-embed into the negative electrode during the charging and discharging process.

[0036] When the lithiumophilic active substance is zinc, the zinc will undergo an alloying reaction with lithium in the negative electrode material layer to generate an alloy, which can provide more superior nucleation sites in energy for lithium deposition, avoid local aggregation and dendrite growth of lithium, and the generated alloy is uniformly distributed, which is equivalent to uniformly distributing countless "lithium deposition guide points", and can enable lithium to be uniformly deposited, avoiding local aggregation and dendrite growth of lithium.

[0037] The most optimal, lithiumophilic active material is zinc oxide. When lithium metal is in contact with zinc oxide, a spontaneous and irreversible displacement reaction occurs: ZnO + 2Li → Li2O + Zn, which generates two critical materials, nano-zinc particles (Zn) and lithium oxide (Li2O). Among them, nano-zinc particles (Zn) are the key role of the subsequent "lithiumophilic" behavior, because lithium ions need to overcome a potential barrier, i.e. nucleation overpotential, to deposit on an unfamiliar substrate. However, zinc can alloy with lithium at room temperature to form lithium-zinc alloys (Li x Zn y ), such as LiZn, Li2Zn5, etc. Lithium atoms prefer to continue "growing" on the already formed lithium-zinc alloy lattice rather than re-nucleating, which significantly reduces the nucleation barrier of lithium. And the uniform distribution of nano-zinc particles is equivalent to the uniform distribution of countless "lithium deposition guide points". After the reduction of lithium ions (Li + ), they will preferentially alloy with zinc and deposit on these points, thereby avoiding the local aggregation and dendrite growth of lithium. Lithium oxide (Li2O) can form a stable interface and is the key to ensuring ion transport. Moreover, the product of the reaction between lithium and zinc oxide, lithium oxide, cannot re-embed the negative electrode during charging and discharging, thus improving the problem of residual lithium in lithium-silicon alloys, which leads to short circuits and rapid capacity decay when paired with high-surface-area cathodes.

[0038] In some embodiments, the first binder and the second binder are each selected from at least one of styrene ethylene butylene styrene copolymer (SEBS), ethylene butadiene rubber (SBR), butadiene rubber (BR), polyisobutylene (PIB), nitrile rubber (NBR), polytetrafluoroethylene (PTFE), polyvinyl acetate (PVA), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), carboxymethyl fiber (CMC), polyacrylonitrile (PAN), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), and polyacrylic acid (PAA). For example, the first binder is styrene ethylene butylene styrene copolymer. For example, the first binder is ethylene butadiene rubber and butadiene rubber. For example, the second binder is ethylene butadiene rubber. For example, the second binder is carboxymethyl fiber and ethylene butadiene rubber.

[0039] In some embodiments, the first conductive agent and the second conductive agent are each selected from at least one of conductive carbon black, conductive graphite, carbon nanotube (CNT), carbon nanofiber (VGCF). Specifically, the conductive carbon black is Super P, acetylene black, Ketjen black, and the conductive graphite can be selected from KS series, SFG series.

[0040] For example, the first conductive agent is conductive carbon black, or the first conductive agent is conductive carbon black and conductive graphite; the second conductive agent is conductive carbon black, or the second conductive agent is carbon nanofiber and carbon nanotube.

[0041] In some embodiments, the plurality of holes on the negative current collector are uniformly distributed.

[0042] In some embodiments, the porosity of the negative current collector is 20%-70%.

[0043] Preferably, the porosity of the negative current collector is 35%-60%. For example, the porosity of the negative current collector is 35%, 50%, 60%, etc.

[0044] Specifically, the negative current collector can adopt a metal foil such as copper foil or a composite current collector. The composite current collector usually adopts a "sandwich" structure, taking an insulating polymer film (such as PET, PP, PE) as the intermediate substrate, and depositing a certain thickness of copper layer on the upper and lower surfaces thereof by a combination of magnetron sputtering and electroplating process, but the application is not limited to these materials.

[0045] In some embodiments, the sulfide electrolyte is selected from at least one of Li2S-SiS2, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li4SnS4·LiI, 90(0.8Li2S-0.2P2S5)·5LiI, 80Li2S-20P2S5, Li3PS4, Li7P3S 11 , 9Li2S·3P2S5·Ni3S2, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.5 PS 4.5 Cl 1.5 , Li 5.7 PS 4.7 C l1.3 , Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75 S4, Li 6.6 Ge 0.6 P 0.4 S5I.

[0046] In some embodiments, the particle size of the sulfide electrolyte is 200 nm-1000 nm.

[0047] Preferably, the particle size of the sulfide electrolyte is 300-800 nm. For example, the particle size D50 of the sulfide electrolyte is 600 nm.

[0048] The embodiments of the present disclosure also provide a method for preparing the negative electrode sheet. The method for preparing the negative electrode sheet comprises the following steps: A predetermined mass of the first binder, the conductive agent, the lithiumophilic active material, and the first binder are sequentially added into pure water and stirred and mixed to obtain a lithiumophilic coating slurry.

[0049] A predetermined mass of the second binder and the non-aqueous solvent, a predetermined mass of the sulfide electrolyte and the non-aqueous solvent, a predetermined mass of the second conductive agent and the non-aqueous solvent, and a predetermined mass of the lithium-silicon alloy and the non-aqueous solvent are sequentially added into a container and stirred and mixed to obtain a negative electrode slurry.

[0050] The lithiumophilic coating slurry is coated on one side of the negative electrode current collector with holes, and the negative electrode slurry is coated on the other side of the negative electrode current collector to obtain a negative electrode sheet.

[0051] Specifically, the preparation of the lithiumophilic coating slurry comprises the following steps: Step S1, a predetermined mass of the first binder and a predetermined mass of pure water are weighed and added into a stirring tank, and stirred at a speed of 1500-2500 rpm for 10-20 min.

[0052] Step S2, a predetermined mass of the conductive agent is weighed and added into the slurry of step S1, and stirred at a speed of 1500-2500 rpm for 10-20 min.

[0053] Step S3, a predetermined mass of the lithiumophilic active material is weighed and added into the slurry of step S2, and stirred at a speed of 1500-2500 rpm for 10-20 min.

[0054] Step S4, a predetermined mass of the first binder is weighed and added into the slurry of step S3, and stirred at a speed of 1500-2500 rpm for 10-20 min to obtain the lithiumophilic coating slurry.

[0055] Specifically, the preparation of the negative electrode slurry comprises the following steps: Step S1, a predetermined mass of the first binder and a predetermined mass of the non-aqueous solvent are weighed and added into a stirring tank, and stirred at a speed of 1500-2500 rpm for 10-20 min.

[0056] Step S2, a predetermined mass of the sulfide electrolyte and a predetermined mass of the non-aqueous solvent are weighed and added into the slurry of step S1, and stirred at a speed of 1500-2500 rpm for 10-20 min.

[0057] Step S3, a second conductive agent of a predetermined mass and a non-aqueous solvent of a predetermined mass are weighed and added to the slurry of step S2, and stirring is performed at a rotation speed of 1500-2500 rpm for 10-20 min.

[0058] Step S4, a lithium-silicon alloy of a predetermined mass and a non-aqueous solvent of a predetermined mass are weighed and added to the slurry of step S3, and stirring is performed at a rotation speed of 1500-2500 rpm for 10-20 min to obtain a negative electrode slurry.

[0059] Specifically, the mass of the non-aqueous solvent added in steps S1-S4 is the same.

[0060] In some embodiments, the non-aqueous solvent is selected from at least one of anisole, isobutyl isobutyrate, toluene, xylene, methyl acetate, ethyl acetate, hexane, n-heptane. For example, the non-aqueous solvent is anisole. For example, the non-aqueous solvent is a mixture of anisole and xylene.

[0061] In some embodiments, the thickness of the lithiumophilic coating slurry coated on the negative electrode current collector is 80-120 um, and the thickness of the negative electrode slurry coated on the negative electrode current collector is 160-240 um. For example, the thickness of the lithiumophilic coating slurry coated on the negative electrode current collector can be 80 um, 100 um, 120 um, etc., and the thickness of the negative electrode slurry coated on the negative electrode current collector can be 160 um, 200 um, 240 um, etc.

[0062] The embodiments of the present disclosure also provide a full-solid sulfide battery. The full-solid sulfide battery comprises a positive electrode, a negative electrode, and a sulfide electrolyte layer disposed therebetween. The negative electrode is the negative electrode sheet described above, or is prepared by the method described above.

[0063] Specifically, the sulfide electrolyte in the sulfide electrolyte layer is selected from Li2S-SiS2, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li4SnS4·LiI, 90(0.8Li2S-0.2P2S5)·5LiI, 80Li2S-20P2S5, Li3PS4, Li7P3S 11 , 9Li2S·3P2S5·Ni3S2, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.5 PS 4.5 Cl 1.5 , Li 5.7 PS 4.7 Cl 1.3 , Li 10 GeP2S 12 , Li 3.25 Ge 0.25 P 0.75S4, Li 6.6 Ge 0.6 P 0.4 S5I at least one of.

[0064] Preferably, the sulfide electrolyte in the sulfide electrolyte layer is selected from Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.5 PS 4.5 Cl 1.5 , Li 5.7 PS 4.7 Cl 1.3 at least one of.

[0065] More preferably, the sulfide electrolyte in the sulfide electrolyte layer is Li 5.5 PS 4.5 Cl 1.5 .

[0066] Specifically, the particle size of the sulfide electrolyte in the sulfide electrolyte layer is 1-100 um. Preferably, the particle size of the sulfide electrolyte in the sulfide electrolyte layer is 1-50 um. For example, the particle size of the sulfide electrolyte in the sulfide electrolyte layer is 10 um.

[0067] The application will be further described in detail below in conjunction with the examples. It should be understood that the specific examples described herein are intended to explain the application, but not to limit the application. The technical conditions or conditions not noted in the examples are carried out according to the technical conditions or conditions described in the literature in the art or according to the product instructions. The reagents or instruments not noted by the manufacturer are all conventional products that can be obtained by purchase.

[0068] Example 1 <Preparation of negative electrode sheet> 1. Preparation of lithium-philic coating slurry Step S1, weigh 5g of CMC aqueous solution with a solid content of 1%, 3g of pure water into a stirring tank, and stir at a speed of 2000rpm for 15min.

[0069] Step S2, weigh 0.1g of Super P into the slurry of step S1, and stir at a speed of 2000rpm for 15min.

[0070] Step S3, weigh 1.8g of ZnO into the slurry of step S2, and stir at a speed of 2000rpm for 15min.

[0071] Step S4, weigh 0.1g of SBR aqueous solution with a solid content of 50% into the slurry of step S3, and stir at a speed of 2000rpm for 15min to obtain the lithium-philic coating slurry.

[0072] 2. Preparation of negative electrode slurry Preparation of 10 g lithium-silicon alloy: the molar mass of Li is 6.941 g / mol, the molar mass of Si is 28.0855 g / mol, according to the molar ratio of lithium-silicon 12:7, 2.976 g of lithium powder and 7.024 g of silicon powder are weighed respectively, put into a ball mill jar, the ball-to-material ratio is 10:1, the ball milling time is 24 h, and Li 12 Si7.

[0073] Step S1, weigh 2 g of SEBS glue solution with a solid content of 5% (solvent is xylene), 0.5 g of p-xylene into a stirring tank, stir at a speed of 2000 rpm for 15 min.

[0074] Step S2, weigh 0.4 g of Li 5.5 PS 4.5 Cl 1.5 , 0.5 g of p-xylene into the slurry of step S1, stir at a speed of 2000 rpm for 15 min.

[0075] Step S3, weigh 0.05 g of VGCF, 0.5 g of p-xylene into the slurry of step S2, stir at a speed of 2000 rpm for 15 min.

[0076] Step S4, weigh 4.45 g of Li 12 Si7, 0.5 g of p-xylene into the slurry of step S3, stir at a speed of 2000 rpm for 15 min to obtain a negative electrode slurry.

[0077] 3. Preparation of negative electrode sheet The lithium-philic coating slurry is coated on one side of the punched stainless steel foil by flat blade coating, wherein the gap of the doctor blade is 100 um, the porosity of the punched stainless steel foil is 50%, and the thickness of the punched stainless steel foil is 20 um. Vacuum drying at a temperature of 120℃ for 24 h; after cooling, the negative electrode slurry is coated on the other side of the negative electrode current collector, the gap of the doctor blade is 200 um, and vacuum drying is carried out at a temperature of 120℃ for 24 h to obtain a negative electrode sheet. The prepared negative electrode sheet is cut into small round pieces with a radius of 5 mm for standby.

[0078] <Preparation of positive electrode sheet> The positive electrode active material high-nickel ternary layered oxide, the conductive agent carbon nanofiber (VGCF), and the binder polytetrafluoroethylene are added into a high-speed mixer in a weight ratio of 96:2:2 for dry mixing, then precision fiberization, electrostatic deposition and transfer, and hot pressing are carried out to obtain a positive electrode sheet with a surface capacity of 5 mAh / cm². Finally, it is cut into small round pieces with a radius of 5 mm.

[0079] <Preparation of all-solid-state sulfide mold battery> Weigh 0.1 g of Li5.5 PS 4.5 Cl 1.5 The electrolyte powder is pressed into a dense sulfide electrolyte layer in a ceramic sleeve with a radius of 5 mm, the particle size D50 of the electrolyte powder is 10 um, a pressure of 2T is used, and the pressure is applied for 1 min. The positive electrode sheet with a radius of 5 mm and a surface capacity of 5 mAh / cm2 prepared above is placed on one side of the sulfide electrolyte layer, the negative electrode sheet with a radius of 5 mm prepared above is placed on the other side of the sulfide electrolyte layer, a pressure of 4T is used, the pressure is applied for 10 min, and the screw is tightened to obtain a full solid sulfide mold full cell.

[0080] Example Two The same parts of Example Two as Example One are omitted, and the same description is omitted. Example Two is different from Example One in that: When preparing the lithium-silicon alloy, 4.454 g of lithium powder and 5.546 g of silicon powder are weighed to prepare 10 g of Li 13 Si4.

[0081] When preparing the lithium-philic coating slurry, in step S1, 20 g of CMC aqueous solution with a solid content of 1% is weighed; in step S2, 0.4 g of Super P is weighed; in step S3, 0.6 g of ZnO and 0.6 g of CoO are weighed; and in step S4, 0.4 g of SBR aqueous solution with a solid content of 50% is weighed.

[0082] When preparing the negative electrode slurry, in step S1, 5 g of SEBS glue solution with a solid content of 5% is weighed; in step S2, 0.5 g of Li 5.5 PS 4.5 Cl 1.5 ; in step S3, 0.25 g of VGCF is weighed; and in step S4, 4 g of Li 13 Si4.

[0083] Example Three The same parts of Example Three as Example One are omitted, and the same description is omitted. Example Three is different from Example One in that: When preparing the lithium-silicon alloy, 4.810 g of lithium powder and 5.190 g of silicon powder are weighed to prepare 10 g of Li 15 Si4.

[0084] When preparing the lithium-philic coating slurry, in step S1, 10 g of CMC aqueous solution with a solid content of 1% is weighed; in step S2, 0.4 g of Super P is weighed; in step S3, 1.4 g of NiO is weighed; and in step S4, 0.2 g of SBR aqueous solution with a solid content of 50% is weighed.

[0085] When preparing the negative electrode slurry, in step S1, 2 g of SEBS glue solution with a solid content of 5% is weighed; in step S2, 0.35 g of Li5.5 PS 4.5 Cl 1.5 ; in step S3, 0.05 g of VGCF was weighed; in step S4, 4.5 g of Li 15 Si4.

[0086] Example Four The same parts of Example Four as Example One are omitted and the same description is omitted. Example Four is different from Example One in that: When preparing the lithium-silicon alloy, 5.123 g of lithium powder and 4.877 g of silicon powder were weighed to prepare 10 g of Li 17 Si4.

[0087] When preparing the lithiumophilic coating slurry, in step S1, 8 g of CMC aqueous solution with a solid content of 1% was weighed; in step S2, 0.24 g of Super P was weighed; in step S3, 1.6 g of ZnO was weighed; in step S4, 0.16 g of SBR aqueous solution with a solid content of 50% was weighed.

[0088] When preparing the negative electrode slurry, in step S1, 2 g of SEBS glue solution with a solid content of 5% was weighed; in step S2, 0.15 g of Li 5.5 PS 4.5 Cl 1.5 ; in step S3, 0 g of VGCF was weighed; in step S4, 4.75 g of Li 17 Si4.

[0089] Example Five The same parts of Example Five as Example One are omitted and the same description is omitted. Example Five is different from Example One in that: When preparing the lithium-silicon alloy, 5.210 g of lithium powder and 4.790 g of silicon powder were weighed to prepare 10 g of Li 22 Si5.

[0090] When preparing the lithiumophilic coating slurry, in step S2, the first conductive agent added was conductive graphite; in step S3, the lithiumophilic active substance added was zinc powder.

[0091] When preparing the negative electrode slurry, in step S1, the second binder added was SEBS glue solution with a solid content of 5% (solvent: xylene) and SBR with a solid content of 50% (solvent: xylene); in step S2, the sulfide electrolyte added was Li6PS5Cl; in step S3, the conductive agent added was carbon nanotubes and carbon nanofibers.

[0092] Comparative Example One The same parts of Comparative Example One as Example One are omitted and the same description is omitted. Comparative Example One is different from Example One in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet. The negative electrode current collector does not need to be punched, and only needs to be coated with the negative electrode slurry on one side of the stainless steel foil.

[0093] Comparative Example Two The same description is omitted for the same part of Comparative Example Two and Example Two, and Comparative Example Two is different from Example Two in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet. The negative electrode current collector does not need to be punched, and only needs to be coated with the negative electrode slurry on one side of the stainless steel foil.

[0094] Comparative Example Three The same description is omitted for the same part of Comparative Example Three and Example Three, and Comparative Example Three is different from Example Three in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet. The negative electrode current collector does not need to be punched, and only needs to be coated with the negative electrode slurry on one side of the stainless steel foil.

[0095] Comparative Example Four The same description is omitted for the same part of Comparative Example Four and Example Four, and Comparative Example Four is different from Example Four in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet. The negative electrode current collector does not need to be punched, and only needs to be coated with the negative electrode slurry on one side of the stainless steel foil.

[0096] Comparative Example Five The same description is omitted for the same part of Comparative Example Five and Example Five, and Comparative Example Five is different from Example Five in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet. The negative electrode current collector does not need to be punched, and only needs to be coated with the negative electrode slurry on one side of the stainless steel foil.

[0097] Comparative Example Six The same description is omitted for the same part of Comparative Example Six and Example One, and Comparative Example Six is different from Example One in that: The lithium-philic coating slurry does not need to be prepared when preparing the negative electrode sheet.

[0098] The preparation method of the negative electrode slurry is as follows: 2 g of SEBS glue solution (solvent is dimethylbenzene) with a solid content of 5%, 0.5 g of p-xylene are weighed into a stirring tank, and stirred at a speed of 2000 rpm for 15 min. Then 0.4 g of silicon powder, 0.5 g of p-xylene are weighed into the above stirring tank, and stirred at a speed of 2000 rpm for 15 min. Then 0.05 g of VGCF, 0.5 g of p-xylene are weighed into the above stirring tank, and stirred at a speed of 2000 rpm for 15 min. Then 4.45 g of Li 12 Si7, 0.5 g of p-xylene are weighed into the above stirring tank, and stirred at a speed of 2000 rpm for 15 min to prepare the negative electrode slurry.

[0099] The negative electrode slurry was coated on one side of the negative electrode current collector with a doctor blade gap of 200 um, vacuum dried at a temperature of 120 °C for 24 h, to obtain a negative electrode sheet. The prepared negative electrode sheet was cut into small round sheets of 5 mm in diameter for standby use.

[0100] Electrochemical performance test The full solid-state sulfide button cells of Examples 1 to 5 and Comparative Examples 1 to 6 were subjected to electrochemical performance test.

[0101] LAND test system was used: constant current charge and discharge mode was used, first charge: constant current charging from open circuit voltage to 4.25 V at 0.05C rate. First discharge: switching to discharge mode, constant current discharging from 4.25 V to 2.5 V cut-off at the same rate, recording the charge and discharge curve and calculating the first coulombic efficiency and specific capacity data, subsequent cycles were cycled at 0.33C / 0.33C rate in the voltage range of 2.5~4.25 V, when the capacity retention rate decreased to 80% of the initial capacity, the cycle number was recorded. During charging and discharging, the current in the circuit was monitored to determine whether the battery had short-circuited.

[0102] The electrochemical test data of the full solid-state sulfide button cells in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1.

[0103] Table 1.

[0104] According to the data in Table 1, when the active substance of the negative electrode material layer is lithium-silicon alloy and a lithiumophilic coating is provided, the full solid-state sulfide button cell has high first coulombic efficiency and cycle performance. When the active substance of the negative electrode material layer is lithium-silicon alloy and no lithiumophilic coating is provided, the full solid-state sulfide button cell has short-circuit phenomenon. When the active substance of the negative electrode material layer is silicon, the full solid-state sulfide button cell has low first coulombic efficiency and cycle performance.

[0105] The text and drawings in the present disclosure are provided only as examples to help understand the present disclosure. They should not be interpreted as limiting the scope of the present disclosure in any way. Although certain embodiments and examples have been provided, it will be clear to those skilled in the art based on the disclosure herein that changes can be made to the embodiments and examples shown without departing from the scope of the present disclosure.

[0106] Although the present disclosure has been described with exemplary embodiments, various changes and modifications can be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

[0107] No description in the present disclosure is to be understood to imply that any particular element, step, or function is an essential element, step, or function of the claims. The scope of patented subject matter is defined only by the claims.

Claims

1. A negative electrode sheet, characterized in that, include: The lithium-loving coating comprises: a lithium-loving active material, a first binder, and a first conductive agent; The negative electrode material layer includes: a lithium-silicon alloy, a sulfide electrolyte, and a second binder; and The negative electrode current collector has multiple through holes. The lithium-loving coating, the negative electrode current collector, and the negative electrode material layer are stacked sequentially.

2. The negative electrode sheet according to claim 1, characterized in that, Based on the total weight of the lithiophilic coating, the mass fraction of the lithiophilic active material is 60%-90%, the mass fraction of the first binder is 5%-20%, and the mass fraction of the first conductive agent is 5%-20%.

3. The negative electrode sheet according to claim 1, characterized in that, Based on the total weight of the negative electrode material layer, the mass fraction of the lithium silicon alloy is 80%-95%, the mass fraction of the sulfide electrolyte is 2%-18%, and the mass fraction of the second binder is 2%-10%.

4. The negative electrode sheet according to claim 1, characterized in that, The negative electrode material layer further includes a second conductive agent, the mass fraction of which is less than 10%, and the second conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, and carbon nanofibers.

5. The negative electrode sheet according to claim 1, characterized in that, The lithiophilic active material is selected from at least one of zinc oxide, cobalt oxide, iron oxide, copper oxide, nickel oxide, cobalt nitride, iron nitride, and zinc.

6. The negative electrode sheet according to claim 1, characterized in that, Both the first adhesive and the second adhesive are selected from at least one of the following: styrene-ethylene-butene-styrene copolymer, ethylene-butadiene rubber, butadiene rubber, polyisobutylene, nitrile rubber, polytetrafluoroethylene, polyvinyl acetate, polyvinyl butyral, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride, carboxymethyl cellulose, polyacrylonitrile, styrene-butadiene-styrene block copolymer, styrene-ethylene / propylene-styrene block copolymer, and polyacrylic acid.

7. The negative electrode sheet according to claim 1, characterized in that, The first conductive agent is selected from at least one of conductive carbon black, conductive graphite, carbon nanotubes, and carbon nanofibers.

8. The negative electrode sheet according to claim 1, characterized in that, The multiple pores on the negative electrode current collector are evenly distributed.

9. The negative electrode sheet according to claim 1, characterized in that, The porosity of the negative electrode current collector is 20%-70%.

10. The negative electrode sheet according to claim 9, characterized in that, The porosity of the negative electrode current collector is 35%-60%.

11. The negative electrode sheet according to claim 1, characterized in that, The sulfide electrolyte is selected from Li2S-SiS2, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li4SnS4·LiI, 90(0.8Li2S-0.2P2S5)·5LiI, 80Li2S-20P2S5, Li3PS4, and Li7P3S. 11 , 9Li2S·3P2S5·Ni3S2, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.5 PS 4.5 Cl 1.5 Li 5.7 PS 4.7 C l1.3 Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 6.6 Ge 0.6 P 0.4 At least one of S5I.

12. The negative electrode sheet according to claim 1, characterized in that, The sulfide electrolyte has a particle size of 200nm-1000nm.

13. A method for preparing the negative electrode sheet according to any one of claims 1-12, characterized in that, Includes the following steps: A predetermined amount of first adhesive, conductive agent, lithiophilic active material, and first adhesive are sequentially added to pure water and stirred to obtain a lithiophilic coating slurry. A predetermined mass of the second binder and non-aqueous solvent, a predetermined mass of the sulfide electrolyte and non-aqueous solvent, a predetermined mass of the second conductive agent and non-aqueous solvent, and a predetermined mass of the lithium silicon alloy and non-aqueous solvent are sequentially added to a container and stirred to obtain a negative electrode slurry. The lithium-loving coating slurry is coated on one side of the porous negative electrode current collector, and the negative electrode slurry is coated on the other side of the negative electrode current collector to obtain a negative electrode sheet.

14. The method according to claim 13, characterized in that: The non-aqueous solvent is selected from at least one of anisole, isobutyl isobutyrate, toluene, xylene, methyl acetate, ethyl acetate, hexane, and n-heptane.

15. The method according to claim 13, characterized in that: The thickness of the lithium-loving coating slurry coated on the negative electrode current collector is 80um-120um, and the thickness of the negative electrode slurry coated on the negative electrode current collector is 160um-240um.

16. An all-solid-state sulfide battery, characterized in that, include: A positive electrode, a negative electrode, and a sulfide electrolyte layer disposed therebetween, wherein the negative electrode is a negative electrode sheet according to any one of claims 1-12, or the negative electrode is prepared by any one of claims 13-15.

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