High-performance solid-state battery and preparation method thereof

Abstract

The invention relates to a high-performance solid-state battery and a preparation method thereof, the solid-state battery comprises at least one bipolar electrode, and the bipolar electrode sequentially comprises a positive electrode active material layer, a current collector and a lithium carbon material layer. The lithium carbon material layer comprises an elastic lithium monomer, and the elastic lithium monomer comprises lithium powder and / or lithium alloy powder as an active core and a tubular carbon nanomaterial as an elastic shell. The elastic shell is distributed between the active cores to construct a three-dimensional network channel, so that lithium ion and electron dual-channel adjustability is realized. The elastic shell can change in applicability according to the change of the active core, so that the problem of volume change caused by lithium deposition / stripping is solved; the surface of the lithium-carbon material layer is provided with micro-nano-scale protrusions, the lithium-carbon material layer can be well combined with the current collector and the solid electrolyte, and the problem of poor interface contact is solved. The solid-state battery has the advantages of small internal resistance, high energy density and good cycle performance and rate capability, and belongs to a high-performance solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and particularly relates to a high-performance solid-state battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are currently the most widely used secondary batteries. Since they use liquid electrolytes containing flammable organic solvents such as dimethyl carbonate (DMC) or 1,2-dimethoxyethane (DME), there are safety hazards. Therefore, the development of solid-state batteries has become one of the research focuses for improving battery safety.

[0003] At present, the application of all-solid-state batteries still needs to solve some technical problems, including positive and negative electrode materials suitable for all-solid-state batteries, technologies for reducing the ionic transport resistance at the interface between the electrolyte phase and the electrode phase, high pressure, etc. These problems severely limit the commercialization of all-solid-state batteries.

[0004] CN 115632123 A discloses an all-solid-state lithium battery and a preparation method thereof. The cathode of the all-solid-state lithium battery includes LiNi 0.5 Mn 1.5 O4, LiFe 0.8 Mn 0.2 PO4, Li2MnP2O7, PTFE, Super-P, and a current collector carbon-coated aluminum foil; the electrolyte includes Li 20 Si3P3S 23 Cl, Li7La3Zr 1.6 Ta 0.4 O 12 , CMC, and PTFE; the anode is an In / Li alloy foil and a current collector copper foil. The synergistic effect of two cathode materials, spinel LiNi 0.5 Mn 1.5 O4 and olivine LiFe 0.8 Mn 0.2 PO4, can be fully exerted, significantly improving the interface and structural stability of the cathode material. However, the selection of the cathode material for the all-solid-state battery is not universal; the mechanical strength of the anode In / Li alloy foil is higher than that of the lithium metal foil, and its interface contact with the solid electrolyte is still poor, with a large interface impedance, making it unable to be widely applied.

[0005] CN101379652A discloses an electrode laminate and a bipolar secondary battery. The electrode laminate includes a stacked positive electrode active material layer and negative electrode active material layer; and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. Through holes penetrating in the stacking direction of the positive electrode active material layer and the negative electrode active material layer are formed in the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer. The electrode laminate further includes: bolts inserted into the holes for integrally holding the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer. Although through this structure, it is possible to effectively prevent the interface shift between the positive electrode, the negative electrode, and the electrolyte, the use of structural components such as bolts results in a low energy density of the battery and does not solve the interface contact problem between the positive electrode, the negative electrode, and the solid electrolyte.

[0006] In most previous studies, all-solid-state batteries need to be tested under a high external pressure of dozens of megapascals, which is unrealistic for practical applications. It is understood that in practical applications, the battery is required to operate stably under less than 10 megapascals.

[0007] How to develop a solid-state battery that is not limited to the type of cathode material, has good contact between the anode and the electrolyte interface, and operates stably under less than 10 megapascals has become an urgent problem to be solved at the present stage. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a high-performance solid-state battery and a preparation method thereof. The negative electrode of the solid-state battery is a lithium-carbon material layer, and the lithium-carbon material layer includes elastic lithium monomers. The elastic lithium monomers include lithium powder and / or lithium alloy powder as active cores, and tubular carbon nanomaterials as elastic shells. The carbon materials with a specific structure in the lithium-carbon material layer are uniformly distributed between the lithium-containing cores, while reducing the local current density, alleviating volume expansion, and inhibiting the growth of lithium dendrites, a conductive network is constructed between the lithium-containing cores and the electrolyte, improving the contact performance of the solid-solid interface. Therefore, the solid-state battery has excellent cycle performance and rate performance.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a solid-state battery, which includes: at least one bipolar electrode, the bipolar electrode sequentially includes a positive electrode active material layer, a current collector, and a lithium-carbon material layer; solid electrolyte layers respectively located on the positive electrode active material layer side and the lithium-carbon material layer side of the bipolar electrode; and a bipolar electrode opposite to the bipolar electrode with an opposite polarity side across the solid electrolyte layer, or a unipolar electrode with an opposite polarity opposite to the bipolar electrode across the solid electrolyte layer, wherein the lithium-carbon material in the lithium-carbon material layer includes elastic lithium monomers, and the elastic lithium monomers include metallic lithium and / or a lithium alloy as an active core and tubular carbon nanotubes as an elastic outer shell, and the elastic outer shells communicate with each other to construct a three-dimensional network channel, and there are protrusions formed by tubular carbon nanotubes on the surface of the lithium-carbon material layer.

[0011] In the present invention, on both side surfaces of the lithium-carbon material layer, the ends or bent portions of the tubular carbon nanotubes form protrusions, which are exposed on the electrode surface, greatly increasing the roughness of the lithium-carbon material layer, so that the combination between the lithium-carbon material layer and the current collector and the solid electrolyte is good, solving the problem of poor contact between the negative electrode and the current collector and the solid electrolyte, and the solid-state battery has the advantage of low internal resistance.

[0012] In the bulk phase of the lithium-carbon material layer, the elastic outer shells formed by the tubular carbon nanotubes communicate with each other to construct a three-dimensional network channel, which plays a role in modifying the bulk phase and stabilizing the structure of the lithium-carbon material layer. The structure stability of the lithium-carbon material layer is good, and even if the active core undergoes volume changes during the deposition / stripping process, the elastic outer shell can adaptively change with the metallic lithium and / or the lithium alloy by using its own ability to restore to its original state, and always maintain good contact with the solid electrolyte, solving the problem of deteriorating the contact between the negative electrode and the solid electrolyte during the deposition / stripping process of metallic lithium, and effectively extending the cycle life of the solid-state battery.

[0013] The tubular carbon nanotubes have good electronic conductivity and effectively regulate the current density; the tubular carbon nanotubes also have a hollow structure and effectively regulate the transport of lithium ions. The tubular carbon materials are connected to each other to construct a three-dimensional network channel, realizing the simultaneous regulation of electrons and ions and inhibiting the growth of lithium dendrites. Compared with the metallic lithium negative electrode, the electrode of the present application converts the two-dimensional planar active lithium deposition / stripping mechanism into a three-dimensional stereoscopic mechanism, can achieve high-rate charge and discharge, and has excellent rate performance.

[0014] Optionally, the lithium alloy includes any one or a combination of at least two of a binary lithium alloy, a ternary lithium alloy, or a multi-component lithium alloy, wherein the mass content of metallic lithium exceeds 50%, preferably more than 80%, and more preferably more than 90%; for example, the alloying elements in the lithium alloy include but are not limited to at least one of boron, silicon, aluminum, gallium, antimony, silver, tin, indium, magnesium, or gold. Within the mass content range, the metallic lithium alloy can take into account the processing performance and the cycle performance.

[0015] Optionally, the tubular carbon nanotubes include at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes or doped carbon nanotubes, preferably a combination of single-walled carbon nanotubes and at least one carbon nanotube selected from double-walled carbon nanotubes, multi-walled carbon nanotubes and doped carbon nanotubes. Single-walled carbon nanotubes have higher flexibility than other tubular carbon materials and can better construct an elastic outer shell while supporting other tubular carbon materials to build a stable elastic outer shell. The mass ratio of the single-walled carbon nanotubes to other tubular carbon materials can be 1:(0.1-10). If the ratio is too high, the amount of single-walled carbon nanotubes is large, the production cost is high, and they are prone to self-aggregation with poor dispersion uniformity. If the ratio is too low, the content of single-walled carbon nanotubes is small and an elastic outer shell cannot be effectively constructed. Preferably, it is 1:(0.5-5).

[0016] Optionally, the doping elements in the doped carbon nanotubes include at least one of nitrogen, oxygen, sulfur, aluminum, silver, silicon, magnesium, tin or zinc.

[0017] Optionally, the lithium-carbon material layer further includes linear carbon nanotubes, preferably nanofibers and / or modified nanofibers; the ratio of the tubular carbon nanotubes to the linear carbon nanotubes is 1:(0.1-10), preferably 1:(0.5-5). This ratio range can balance the structural stability and cycling stability of the lithium-carbon material layer.

[0018] Optionally, the diameter of the linear and / or tubular carbon nanotubes is below 200 nm, preferably 1-50 nm, and more preferably 2-10 nm.

[0019] Optionally, the length of the linear and / or tubular carbon materials is above 1 μm, preferably 3-50 μm, and more preferably 5-30 μm.

[0020] Optionally, the aspect ratio of the linear and / or tubular carbon materials is 10-100000, preferably 2000-50000, and more preferably 5000-30000.

[0021] Optionally, the average thickness of the elastic outer shell is 0.05-10 μm, preferably 0.5-5 μm.

[0022] Optionally, based on the total mass of the lithium-carbon material layer being 100%, the mass fraction of the elastic outer shell is 0.05%-50%, preferably 0.25%-30%. By adjusting the mass fraction to adjust the average thickness of the elastic outer shell, the thickness of the elastic outer shell of the present invention can be adjusted, thereby realizing the adjustment of the electron and ion channels.

[0023] As a preferred technical solution of the present invention, the elastic outer shell further includes an elastic filler, and the elastic filler includes a thermoplastic elastic material and a conductive material. By utilizing the good elasticity and softness of the thermoplastic elastic material and the excellent electrical conductivity of the conductive material, the elastic filler has both electrical conductivity and toughness, effectively increasing the flexibility of the elastic outer shell and the ability to recover deformation, and making the interface contact closer.

[0024] Optionally, the mass ratio of the thermoplastic elastic material to the conductive material is (0.1 - 10):(90 - 99.9). If the mass ratio is too low, the amount of the thermoplastic elastic material is small, and its effect on adapting to the deformation of the elastic outer shell is limited; if the mass ratio is too high, the amount of the thermoplastic elastic material is large, and its effect on adapting to the deformation of the elastic outer shell is strong, but the electrical conductivity is greatly reduced, which is not conducive to the performance of the electrode. Preferably, it is (0.5 - 5):(95 - 99.5), and more preferably (1 - 3):(97 - 99).

[0025] Optionally, the thermoplastic elastic material includes, but is not limited to, any one or a combination of at least two of styrene - butadiene - styrene block copolymer (SBS), styrene - isoprene - styrene block copolymer (SIS), styrene - ethylene - butene - styrene block copolymer (SEBS), and styrene - ethylene - propylene - styrene block copolymer (SEPS).

[0026] Optionally, the conductive material includes, but is not limited to, at least one of Ketjen black, acetylene black, Cabot carbon black, conductive graphite, Super P, graphene, graphene oxide, mesophase carbon microspheres, carbon nanofibers, or nano - metal particles.

[0027] Optionally, based on the total mass of the lithium - carbon material layer being 100%, the mass fraction of the elastic filler is below 5%. If the mass fraction is too large, the content of the elastic filler is high, which hinders the electron and ion transport of the lithium - carbon material layer; if the mass fraction is too small, the content of the elastic filler is low, and its adaptability to the volume change of the lithium - carbon material layer is weak. Preferably, it is 0.5 - 3%.

[0028] Preferably, the surface roughness Ra of the lithium - carbon material layer is greater than 0.3 μm, and preferably Ra is 0.5 - 5 μm. The surface roughness has the meaning well - known in the art and can be measured by the instruments and methods well - known in the art. For example, it can be measured by a surface roughness meter. In this application, the NDT110 type equipment of Beijing Kaida Keyi Technology Co., Ltd. is used for measurement.

[0029] Preferably, the peeling force between the lithium-carbon material layer and the current collector is greater than 0.2 kgf, preferably 0.5 - 5 kgf. The peeling force has the meaning well-known in the art and can be measured by the instruments and methods well-known in the art. For example, it can be measured by a universal tensile testing machine. In this application, a Shimadzu AG-X50N universal tensile testing machine is used for testing.

[0030] Optionally, the thickness of the lithium-carbon material layer is 5 - 100 μm, preferably 10 - 50 μm.

[0031] Preferably, the N / P ratio of the lithium-carbon material layer to the positive electrode active material layer is 0.5 - 1.25, preferably 1.05 - 1.15. The N / P ratio is designed according to actual requirements.

[0032] Optionally, the positive electrode active material layer includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganate, lithium cobaltate, sublimed sulfur, sulfonated polyacrylonitrile, vanadium pentoxide, or MS2 (M = Fe, Mn, Mo, V, Ti, Co, or Cr).

[0033] Optionally, an elastic functional layer is further provided on the surface of the positive electrode active material layer. The elastic functional layer includes a thermoplastic elastic material and a conductive material. The function of the elastic functional layer is to improve the interfacial contact between the positive electrode active material layer and the solid electrolyte layer, and at the same time can adaptively change with the volume change of the electrode structure during the charge and discharge process, so that the positive electrode can better match the lithium-carbon material layer.

[0034] Optionally, the mass ratio of the thermoplastic elastic material to the conductive material is (0.5 - 5):(95 - 99.5), preferably (1 - 3):(97 - 99).

[0035] Optionally, the thermoplastic elastic material includes at least one of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS); the conductive material includes at least one of Ketjen black, acetylene black, Cabot carbon black, conductive graphite, Super P, graphene, graphene oxide, mesophase carbon microspheres, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or nano metal particles.

[0036] Optionally, the thickness of the elastic functional layer is 0.1 - 10 μm, preferably 1 - 5 μm. The setting method of the elastic functional layer is not specifically limited. It can be coating (solvents such as N-methylpyrrolidone, n-hexane, xylene, etc.), screen printing, or spraying. As long as it is a method commonly used by those skilled in the art, it is applicable to this application.

[0037] Optionally, the current collector includes a base current collector and a modified current collector. The base current collector includes at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, conductive polymer thin film, or carbon fiber paper. The polymer matrix material of the conductive polymer composite thin film includes but is not limited to at least one of polyethylene, polypropylene, polystyrene, polyurethane, epoxy resin, and phenolic resin. The conductive filler of the conductive polymer composite thin film includes but is not limited to at least one of conductive carbon black, conductive graphite, carbon nanofiber, carbon nanotube, graphene, metal, and metal oxide.

[0038] Optionally, the modified current collector includes a base current collector and a coating disposed on the surface of the base current collector. The coating includes at least one of graphene, graphene oxide, chromate, manganese oxide, or aluminum oxide. Different types of coatings have different interactions with the lithium-carbon material layer. Preferably, a coating that can form an integral structure with the lithium-carbon material coating is selected; the thickness of the coating is selected according to actual needs, generally 3-10 μm.

[0039] Optionally, the solid electrolyte in the solid-state battery includes at least one of polymer solid electrolyte, oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, or composite solid electrolyte.

[0040] Illustrating the types of solid electrolytes, the polymer solid electrolyte includes but is not limited to polyethylene oxide (PEO)-type polymer electrolyte, polyacrylonitrile (PAN)-type polymer electrolyte, polyvinylidene fluoride (PVDF)-type polymer electrolyte, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP)-type polymer electrolyte, polyethylene glycol (PEG)-type polymer electrolyte, polydimethylsiloxane (PDMS)-type polymer electrolyte, polyvinyl chloride acetate (PVCA)-type polymer electrolyte, etc. The oxide solid electrolyte includes but is not limited to Li 6.4 La3Zr 1.4 Ta 0.6 O 12 (LLZTO), Li7La3Zr2O 12 (LLZO), Li 6.28 La3Al 0.24 Zr2O 12 (LLAZO), etc. The sulfide solid electrolyte includes but is not limited to Li 10 GeP2S 12 (LGPS), Li6PS5Cl (LPSCl), Li 10 SnP2S 12 、Li 6+x M x As 1-xS5I (M = Si, Sn), Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, or Li2S-B2S3, etc. The halide solid electrolyte includes but is not limited to Li2ZrCl6 (LZC), Li3InCl6, Li x ScCl 3+x (x = 2.5, 3, 3.5, 4), Li2Sc 2 / 3 Cl4, Li 3-x (Er / Y) 1-x Zr x Cl6, Li3Y 1-x In x Cl6 and Li 2.25 Zr 0.75 Fe 0.25 C l6 etc. The composite solid electrolyte is generally an electrolyte obtained by compounding inorganic fillers and polymer solid electrolytes. The composite solid electrolyte combines the advantages of inorganic solid electrolytes and organic solid electrolytes. The inorganic fillers include but are not limited to Al2O3, ZrO2, SiO2, Y2O3, TiO2, BaTiO3, Mg2B2O5, MOF-5, LLZO, LLZTO, Li 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP), Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP), LGPS, LSPS, etc.

[0041] Second, the present invention provides a method for preparing a solid-state battery as described in the first aspect above. The method includes the following steps:

[0042] (1) Mix the positive electrode active material, conductive agent, and binder, and set them on one side of the current collector; or set the lithium-carbon material on one side of the current collector;

[0043] (2) Set the material containing the active material with the opposite polarity to that in step (1) on the other side of the current collector to obtain a bipolar electrode;

[0044] (3) Stack the bipolar electrode obtained in step (2) across the solid electrolyte layer to obtain a stacked body. The outermost electrode of the stacked body is a unipolar electrode, and the polarity of the active substance on the unipolar electrode is opposite to that of the active substance in the adjacent electrode structure. Then, package it to obtain the solid-state battery.

[0045] For the preparation method provided by the present invention, there is no specific limitation on the setting method of the positive electrode active material layer, which can be a wet process or a dry process.

[0046] The preparation method is simple and easy to operate, and is easy to industrialize production.

[0047] The preparation method of the lithium-carbon material is illustrated by way of example, but is not limited to the preparation method of the lithium-carbon material:

[0048] (1`) Mix a lithium-containing core, a tubular carbon nanomaterial, and a non-polar organic solvent; (2`) Spray granulation or high-speed winding under the condition of a rotation speed above 6000 rpm, and the tubular carbon nanotube material forms an elastic outer shell, and at least one lithium-containing core is included in the elastic outer shell to obtain the lithium-carbon material.

[0049] For the lithium-carbon material containing an elastic filler, its preparation method is not limited. For example, it may include the following steps: uniformly mix a thermoplastic elastomer and a conductive material to obtain an elastic slurry, add the elastic slurry to the mixture in (1`), or add the elastic slurry after step (1`) is completed for secondary mixing, and perform step (2`) after mixing. The lithium-carbon material and the elastic slurry can also be mixed in step (2`) for secondary spray granulation or high-speed mixing, and the rotation speed of the mixing is above 5000 rpm.

[0050] The non-polar organic solvent includes, but is not limited to, any one or at least two combinations of liquid alkanes with 5-10 carbon atoms, benzene, p-xylene, or petroleum ether.

[0051] The lithium-containing core includes metallic lithium powder and / or lithium alloy powder.

[0052] As a preferred preparation method of the present invention, the method includes the following steps:

[0053] (a) Prepare a positive electrode active material layer from a positive electrode active material, a conductive agent, and a binder through a dry process, and then set it on one side of a current collector through a mechanical rolling and / or bonding process;

[0054] (b) Set the lithium-carbon material on the other side of the current collector described in step (1) through any one or at least two combinations of mechanical rolling, twisting, spraying, or stamping to obtain the electrode structure;

[0055] (c) Stack the electrode structure and a solid electrolyte layer to obtain a stacked body. The outermost electrode of the stacked body is a unipolar electrode, and the polarity of the active substance on the unipolar electrode is opposite to the polarity of the active substance in the adjacent electrode structure. Then, through isostatic pressing and encapsulation, the solid-state battery is obtained.

[0056] Optionally, the isostatic pressing encapsulation in step (c) includes cold isostatic pressing, warm isostatic pressing or a combination of both. The temperature of cold isostatic pressing is below 20°C, preferably 5 - 15°C; the temperature of warm isostatic pressing is above 20°C, preferably 40 - 100°C. The pressure of the isostatic pressing encapsulation is below 10 MPa.

[0057] Compared with the prior art, the present invention has at least the following beneficial effects:

[0058] (1) For the solid-state battery provided by the present invention, the tubular carbon nanomaterials are exposed on the surfaces of both sides of the electrode, forming protrusions, which greatly increases the roughness of the lithium-carbon material layer. The interface between the negative lithium-carbon material layer, the current collector and the solid electrolyte is good, and the interface impedance of the solid-state battery is small, having excellent cycle performance;

[0059] (2) For the solid-state battery provided by the present invention, the negative lithium-carbon material layer has dual channels for ions and electrons, effectively regulating the negative current density and the transport of lithium ions, inhibiting the growth of lithium dendrites, and the solid-state battery has good cycle stability and excellent rate performance;

[0060] (3) For the solid-state battery provided by the present invention, the elastic outer shell formed by the tubular carbon nanomaterials can adaptively change with the volume change of metallic lithium and / or lithium alloy by utilizing its self-recovery deformation performance, ensuring that the lithium-carbon material layer, the current collector and the solid electrolyte layer always maintain good contact during charge and discharge, and the solid-state battery can operate stably at less than 10 MPa;

[0061] (4) By designing parameters such as the type and mass fraction of the elastic outer shell material, the present invention regulates the surface state of the electrode, optimizes the interface contact problem between the lithium-carbon material layer, the current collector and the solid electrolyte, and improves the cycle performance of the solid-state battery;

[0062] (5) For the solid-state battery provided by the present invention, by further providing an elastic functional layer on the surface of the positive electrode active material layer, the problems of poor contact between the positive electrode and the solid electrolyte layer and the volume change of the positive electrode are improved. The positive electrode, the solid electrolyte and the lithium-carbon material layer cooperate with each other to further improve the cycle performance of the solid-state battery;

[0063] (6) The preparation method provided by the present invention is simple in operation, high in production efficiency and has universality. Description of the Drawings

[0064] Figure 1 It is a schematic diagram for comparing the structure of the solid-state battery in the prior art with the structure of the solid-state battery of the present application.

[0065] 1 - Metallic lithium, 1' - Lithium-carbon material layer, 2 - Negative current collector, 2' - Bipolar current collector, 3 - Solid electrolyte layer, 4 - Positive electrode active material layer, 5 - Positive current collector;

[0066] Figure 2 SEM cross-sectional view of the electrode in Example 2. Detailed implementation manners

[0067] For ease of understanding the present invention, the following examples are listed. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0068] For example, the differences between the solid-state battery structure in the present application and the solid-state battery structure in the prior art are shown in the structure comparison schematic diagram as Figure 1 shown. It can be seen from the figure that a conventional solid-state battery in the prior art includes 3 electrode units. Each electrode unit includes a metallic lithium negative electrode 1, a negative electrode current collector 2 (generally a copper foil), a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector 5. Ear tabs (not shown) are left on each negative electrode current collector and positive electrode current collector, and the ear tabs are welded later for current collection. A parallel structure is formed between the electrode units. The voltage of the solid-state battery is equal to the voltage of the electrode unit (if NVM811 is used as the positive electrode, the voltage is 3.7V), and the battery capacity is the sum of the capacities of the electrode units.

[0069] The solid-state battery in the present application includes 2 bipolar electrodes and a unipolar electrode with a polarity opposite to the opposite surface of the bipolar electrode. The bipolar electrode includes a lithium-carbon material layer 1', a bipolar current collector 2', and a positive electrode active material layer 4. A solid electrolyte layer 3 is provided between the bipolar electrodes. A series structure is formed between the bipolar electrode and the unipolar electrode, and the current / voltage is output from the unipolar electrodes on both sides of the solid-state battery. The voltage of the solid-state battery is equal to the sum of the electrode voltages. By superimposing the double-electrode structure, a high voltage can be provided.

[0070] During the charge and discharge process, voids and pores (shown as white areas in the figure) will appear between the metallic lithium negative electrode 1 and the solid electrolyte layer 3 in the solid-state battery in the prior art, and the interfacial contact will deteriorate further with cycling; in the solid-state battery in the present application, the lithium-carbon material layer 1' has an elastic shell formed by tubular carbon materials, which can adapt to the volume change of the lithium-carbon material layer and always maintain good contact with the solid electrolyte.

[0071] Example 1

[0072] This example provides a solid-state battery, the solid-state battery includes a bipolar electrode, the positive electrode active material is lithium iron phosphate, the negative electrode is a lithium-carbon material layer, and the electrolyte is Li2ZrCl6.

[0073] The preparation method of the solid-state battery includes the following steps:

[0074] (1) Mix lithium iron phosphate (Orion Energy Technology (Beijing) Co., Ltd.), Li2ZrCl6, acetylene black (Aladdin), and PVDF (Solvay 5130, USA) in a mass ratio of 7:1:1:1. The solvent is N-methylpyrrolidone (Shandong Changxin Chemical Technology Co., Ltd.) to make a slurry, and then coat it on the surface of the aluminum foil in a 12-μm copper-aluminum composite foil and the surface of a 15-μm pure aluminum foil respectively, and dry it to obtain the positive electrode 1 and the positive electrode 2 in sequence;

[0075] (2) Disperse Li2ZrCl6 (LZ C), CMC (Aladdin), and PTFE (Aladdin) in acetonitrile (Aladdin), stir and mix evenly, then evaporate the solvent to obtain a solid mixture, and then repeatedly hot-press the solid mixture into a film in a roll press with a heating function to obtain a solid electrolyte layer;

[0076] (3) Take the positive electrode 1 in step (1), and use a roll press to roll the lithium-carbon material on the surface of the copper foil on the side opposite to the lithium iron phosphate to make a bipolar electrode, control the thickness of the lithium-carbon material layer to be 20 μm. At the same time, use a roll press to roll the lithium-carbon material on the surface of a 15-μm copper foil to obtain a single-sided negative electrode, and control the thickness of the lithium-carbon material layer to be 20 μm;

[0077] The preparation method of the lithium-carbon material is as follows: Weigh 21 g of a 3% single-walled carbon nanotube dispersion (Oxyair) and 0.17 g of multi-walled carbon nanotubes (with a diameter of 8 - 10 nm, Tianjin Aivixin Chemical Industry) and 29.2 g of metallic lithium powder with an average particle size of 20 μm into a beaker, add 800 g of n-hexane, mix at a high speed at a rotation speed of 12000 rpm for 10 min, control the mass fraction of single-walled carbon nanotubes in the lithium-carbon material to be 2%, filter by suction, and heat to remove n-hexane to obtain the lithium-carbon material;

[0078] (4) Stack the positive electrode 2, the solid electrolyte membrane, the bipolar electrode, the solid electrolyte membrane, and the single-sided negative electrode in sequence, and press and bond them tightly at 90 °C by means of warm isostatic pressing at 2 MPa to assemble a solid-state battery.

[0079] The solid-state battery is subjected to a cycling test at 60 °C and 3 MPa at 0.2C, the voltage range is 3.0 - 4.0V, the initial discharge specific capacity is 116.7 mAh / g, and the capacity retention rate is 92.5% after 100 stable cycles.

[0080] Example 2

[0081] This example provides a solid-state battery. The solid-state battery includes 3 bipolar electrodes. The positive electrode active material of the solid-state battery is NCM811, the negative electrode is a lithium-carbon material layer, and the electrolyte is an ionic conductor lithium lanthanum zirconium oxide LLZO.

[0082] The preparation method of the solid-state battery includes the following steps:

[0083] (1) Use a roll press to roll the lithium-carbon material onto one surface of a 10-μm stainless steel foil with an alumina coating to make the negative electrode 1. At the same time, take a roll press to roll the lithium-carbon material onto the surface of a 15-μm stainless steel foil to make the negative electrode 2;

[0084] The preparation method of the lithium-carbon material is as follows: Weigh 5 g of a 3% single-walled carbon nanotube dispersion (Okosier), add 2000 g of heptane, disperse it at a high speed of 15000 rpm for 2 min, add 120 g of lithium-tin alloy powder (the mass fraction of tin is 5%), mix it at a high speed of 15000 rpm for 5 min, control the mass fraction of single-walled carbon nanotubes in the lithium-carbon material to be 0.12%, filter by suction, and heat to remove heptane to obtain the lithium-carbon material;

[0085] (2) Mix lithium niobate-coated NCM811 (Thornton New Energy Technology Co., Ltd.), LLZO, acetylene black (Aladdin), and PTFE (Daikin Japan) evenly according to the mass ratio of 85:5:5:5, shear at a high speed, and then hot roll it into a positive electrode active material layer. Stick it to the other surface of the stainless steel foil in step (1) through a conductive adhesive to obtain a bipolar electrode. At the same time, roll the positive electrode active material layer onto the surface of a 15-μm stainless steel foil to obtain a single-sided positive electrode, and control the thickness of the lithium-carbon material layer to be 50 μm;

[0086] (3) In a glove box, dissolve the butadiene rubber (Aladdin) binder in a toluene solution, add LLZO (Aladdin), and then heat and stir until a stable and uniform solution is obtained; Spin-coat this solution onto the positive electrode side of the bipolar electrode in step (2) and the surface of the single-sided positive electrode respectively, and dry it to obtain a bipolar electrode and a single-sided positive electrode sheet containing a solid electrolyte;

[0087] (4) Press and fit the positive electrode sheet containing a solid electrolyte, 3 bipolar electrodes, and a single-sided negative electrode at 10 °C by cold isostatic pressing at 8 MPa to assemble a solid-state battery.

[0088] Take the cross-section SEM (excluding the stainless steel foil) of the rolled lithium-carbon material in step (1) for testing, and the test results are as Figure 2 shown. It can be clearly seen from the figure that the lithium-carbon material layer includes an elastic outer shell formed by single-walled carbon nanotubes and lithium-tin alloy powder contained in the elastic outer shell. The elastic outer shells are interconnected to build a three-dimensional network channel, and there are protrusions formed by exposed carbon nanotubes on both side surfaces of the lithium-carbon material layer.

[0089] Take the negative electrode 1 in step (1) to test the surface roughness and peel strength. After testing, the surface roughness Ra of the lithium-carbon material layer is 0.62, and the peel strength is 3.65 kgf.

[0090] The solid-state battery was subjected to a cycling test at 60 °C and 5 MPa at 0.2C, with a voltage range of 3.0 - 4.3V. The initial discharge specific capacity was 185.4 mAh / g. After 100 stable cycles, the capacity retention rate was 90.44%.

[0091] Example 3

[0092] This example provides a solid-state battery, which includes 5 bipolar electrodes. The positive electrode active material is polyacrylonitrile sulfide, the negative electrode is a lithium-carbon material layer, and the electrolyte is an LGPS solid electrolyte.

[0093] The preparation method of the solid-state battery includes the following steps:

[0094] (1) Polyacrylonitrile sulfide (Aladdin), Super P (Tianjin Youmeng Chemical Technology Co., Ltd.) and LGPS were ball-milled and mixed in a mass ratio of 6:2:2, and then pressed into tablets to obtain a positive electrode active material layer. The positive electrode active material layer was adhered to one side of a 20-μm carbon fiber paper with a graphene oxide coating through a conductive adhesive to obtain a positive electrode. At the same time, the positive electrode active material layer was adhered to the surface of a 12-μm nickel foil to prepare a single-sided positive electrode;

[0095] (2) LGPS was pressed into tablets to prepare an electrolyte layer;

[0096] (3) The lithium-carbon material was roll-pressed on the other side of a 20-μm carbon fiber paper with a graphene oxide coating by a roll press, and the thickness of the lithium-carbon material layer was controlled to be 100 μm to form a bipolar electrode. At the same time, the prepared lithium-carbon material was roll-pressed on the surface of a 12-μm nickel foil to prepare a single-sided negative electrode;

[0097] The preparation method of the lithium-carbon material is as follows: Weigh 50 g of a 3% single-walled carbon nanotube dispersion (Okosier) and 15 g of nanofiber carbon VGCF (OEMG), mix them at a high speed for 15 min at a rotation speed of 10,000 rpm, add 16.5 g of lithium-silver alloy powder (the mass fraction of silver is 1%), mix them at a high speed for 5 min at a rotation speed of 15,000 rpm, perform suction filtration, and heat to remove p-xylene to obtain the lithium-carbon material;

[0098] (4) The single-sided positive electrode, the electrolyte layer, 5 bipolar electrodes and the single-sided negative electrode were tightly pressed and bonded at 40 °C by warm isostatic pressing at 5 MPa to assemble a solid-state battery.

[0099] The solid-state battery was subjected to a cycling test at 60 °C and 8 MPa at 0.2C, with a voltage range of 1.5 - 3.0V. The initial discharge specific capacity was 809.32 mAh / g. After 100 stable cycles, the capacity retention rate was 91.69%.

[0100] Example 4

[0101] Compared with Example 2, the only difference is that the mass fraction of single-walled carbon nanotubes in the lithium-carbon material layer is replaced by 0.25%.

[0102] The solid-state battery was subjected to a cycling test at 60 °C, 5 MPa, 0.2C, the voltage range was 3.0 - 4.0V, the initial discharge specific capacity was 184.9 mAh / g, and after 100 stable cycles, the capacity retention rate was 91.85%.

[0103] Example 5

[0104] Compared with Example 2, the only difference is that the mass fraction of single-walled carbon nanotubes in the lithium-carbon material layer is replaced by 30%.

[0105] The solid-state battery was subjected to a cycling test at 60 °C, 5 MPa, 0.2C, the voltage range was 3.0 - 4.0V, the initial discharge specific capacity was 184.8 mAh / g, and after 100 stable cycles, the capacity retention rate was 93.32%.

[0106] Example 6

[0107] Compared with Example 2, the only difference is that an elastic filler is added to the lithium-carbon material layer, and the elastic filler includes SBS and mesophase carbon microspheres with a mass ratio of 0.5:99.5.

[0108] The preparation method of the lithium-carbon material is as follows: 0.03 g of SBS and 5.97 g of mesophase carbon microspheres are mixed in 500 g of heptane to prepare an elastic slurry, and stirred for 2 h until the SBS is dissolved;

[0109] Weigh 5 g of a 3% single-walled carbon nanotube dispersion (Okosier), add 2000 g of heptane, disperse it at a high speed of 15000 rpm for 2 min, add it to the elastic slurry and mix evenly, add 120 g of lithium-tin alloy powder (the mass fraction of tin is 5%), mix it at a high speed of 15000 rpm for 5 min, filter by suction, and heat to remove heptane to obtain the lithium-carbon material.

[0110] The solid-state battery was subjected to a cycling test at 60 °C, 5 MPa, 0.2C, the voltage range was 3.0 - 4.0V, the initial discharge specific capacity was 184.8 mAh / g, and after 100 stable cycles, the capacity retention rate was 94.15%.

[0111] Example 7

[0112] Compared with Example 2, the only difference is that an elastic filler is added to the lithium-carbon material layer, and the elastic filler includes SEBS and graphene oxide with a mass ratio of 3:97.

[0113] The preparation method of the lithium-carbon material is as follows: 0.09 g of SEBS and 2.91 g of graphene oxide are mixed in 500 g of heptane to prepare an elastic slurry, and stirred for 2 h until the SBS is dissolved;

[0114] Weigh 5 g of a 3% single-walled carbon nanotube dispersion (Okosier), add 2000 g of heptane, disperse at a high speed of 15000 rpm for 2 min, add it to the elastic slurry and mix evenly, add 120 g of lithium-tin alloy powder (the mass fraction of tin is 5%), mix at a high speed of 15000 rpm for 5 min, filter by suction, and heat to remove heptane to obtain the lithium-carbon material.

[0115] The solid-state battery is subjected to a cycle test at 60 °C, 5 MPa, and 0.2 C. The voltage range is 3.0 - 4.0 V. The initial discharge specific capacity is 184.8 mAh / g. After 100 stable cycles, the capacity retention rate is 93.71%.

[0116] Example 8

[0117] Compared with Example 2, the difference is only that an elastic functional layer with a thickness of 1 μm is coated on the surface of the positive electrode material layer. The elastic functional layer includes SIS and single-walled carbon nanotubes with a mass ratio of 1:99.

[0118] The solid-state battery is subjected to a cycle test at 60 °C, 5 MPa, and 0.2 C. The voltage range is 3.0 - 4.0 V. The initial discharge specific capacity is 184.8 mAh / g. After 100 stable cycles, the capacity retention rate is 95.32%.

[0119] Example 9

[0120] Compared with Example 8, the difference is only that the lithium-carbon material layer uses the lithium-carbon material layer in Example 7.

[0121] The solid-state battery is subjected to a cycle test at 60 °C, 5 MPa, and 0.2 C. The voltage range is 3.0 - 4.0 V. The initial discharge specific capacity is 184.8 mAh / g. After 100 stable cycles, the capacity retention rate is 96.98%.

[0122] Example 10

[0123] Compared with Example 1, the difference is only that the lithium-carbon material layer does not contain multi-walled carbon nanotubes, that is, multi-walled carbon nanotubes are not added in the method for preparing the lithium-carbon material. The lithium-carbon material consists of metallic lithium powder as the active core and single-walled carbon nanotubes as the elastic shell, and the other conditions are the same as those in Example 1.

[0124] The solid-state battery was subjected to a cycling test at 60 °C, 3 MPa, 0.2C, with a voltage range of 3.0 - 4.0V. The initial discharge specific capacity was 116.0 mAh / g. After 100 stable cycles, the capacity retention rate was 91.11%.

[0125] Comparative Example 1

[0126] Compared with Example 1, the only difference is that the lithium-carbon material is replaced with pure metallic lithium powder, and the other conditions are the same as those in Example 1.

[0127] The solid-state battery was subjected to a cycling test at 60 °C, 5 MPa, 0.2C, with a voltage range of 3.0 - 4.0V. The first discharge specific capacity was 116.8 mAh / g. After 100 stable cycles, the capacity retention rate was 72.56%. This is because the volume change of pure metallic lithium powder is more obvious during charge and discharge, and there is no elastic outer shell for adaptive adjustment.

[0128] Comparative Example 2

[0129] Compared with Example 2, the only difference is that the lithium-carbon material is replaced with lithium-tin alloy powder, and the other conditions are the same as those in Example 2.

[0130] The solid-state battery was subjected to a cycling test at 60 °C, 5 MPa, 0.2C, with a voltage range of 3.0 - 4.0V. The first discharge specific capacity was 157.2 mAh / g. After 100 stable cycles, the capacity retention rate was 73.84%. This is because although the lithium-tin alloy negative electrode can regulate the deposition of metallic lithium to a certain extent, compared with the lithium-carbon material layer in Example 2, the volume change during charge and discharge is still more obvious, and there is no elastic outer shell for adaptive adjustment.

[0131] The surface roughness and peel strength of the negative electrode prepared from lithium-tin alloy powder were tested. The surface roughness Ra of the lithium-tin alloy negative electrode was 0.35, and the peel strength was 2.85 kgf, both of which were lower than those in Example 2. This is because there is no elastic outer shell on the surface of the lithium-tin alloy powder, there are no nanoscale protrusions, the surface roughness is low, and it is close to pure metallic lithium tape; even though lithium in the negative electrode can react with the alumina coating to form an integrated structure, the contact between the negative electrode prepared from pure metallic lithium powder and the stainless steel foil with an alumina coating is planar (two-dimensional), while there are protrusions on the surface of the lithium-carbon material layer in Example 2, and the contact between the lithium-carbon material layer and the stainless steel foil with an alumina coating is three-dimensional (three-dimensional), with good interfacial contact and difficult to peel.

[0132] Comparative Example 3

[0133] Compared with Example 2, the only difference is that the lithium-tin alloy powder and single-walled carbon nanotubes in the lithium-carbon material layer are randomly distributed, and a three-dimensional network channel is not constructed, and the other conditions are the same as those in Example 2.

[0134] The preparation method of the lithium-carbon material is as follows:

[0135] Weigh 5 g of a single-walled carbon nanotube dispersion (Okesiere) with a mass fraction of 3%, add 2000 g of heptane, disperse it at a high speed for 2 min at a rotation speed of 15000 rpm, add 120 g of lithium-tin alloy powder (the mass fraction of tin is 5%), mix it at a rotation speed of 1500 rpm for 5 min, filter it by suction, heat to remove heptane, and obtain a mixture.

[0136] The solid-state battery is subjected to a cycling test at 60 °C, 5 MPa, and 0.2 C. The voltage range is 3.0 - 4.0 V. The initial discharge specific capacity is 157.1 mAh / g. After 100 stable cycles, the capacity retention rate is 74.37%. This is because the single-walled carbon nanotubes are randomly distributed and do not form an elastic shell, resulting in limited improvement in battery performance.

[0137] Comparative Example 4

[0138] Compared with Example 2, the difference is only that the lithium-carbon material is carbon nanotube microspheres (the carbon nanotube microspheres are obtained by dispersing multi-walled carbon nanotubes in a liquid and then spray granulating, and the specific method is the same as that in the literature. The literature is Yalong Wang, A lithium–carbon nanotube composite for stable lithium anodes. J. Mater. Chem. A, 2017, 5, 23434–23439.) after being filled with molten lithium-tin alloy (the mass fraction of tin is 5%), and the other conditions are the same as those in Example 2.

[0139] The solid-state battery is subjected to a cycling test at 60 °C, 5 MPa, and 0.2 C. The voltage range is 3.0 - 4.0 V. The initial discharge specific capacity is 157.3 mAh / g. After 100 stable cycles, the capacity retention rate is 71.44%. This is because even when using lithium-tin alloy (the mass fraction of tin is 5%), metallic lithium still preferentially deposits on the surface of the carbon nanotube microspheres, forming lithium dendrites.

[0140] The applicant declares that the present invention uses the above embodiments to illustrate the detailed structural features of the present invention, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A solid-state battery, characterized in that, The solid-state battery includes: At least one bipolar electrode, which sequentially includes a positive electrode active material layer, a current collector, and a lithium-carbon material layer; Solid electrolyte layers respectively located on the side of the positive electrode active material layer and the side of the lithium-carbon material layer of the bipolar electrode; and A bipolar electrode opposite to the bipolar electrode with an opposite polarity side across the solid electrolyte layer, or a unipolar electrode with an opposite polarity opposite to the bipolar electrode across the solid electrolyte layer, Wherein the lithium-carbon material in the lithium-carbon material layer includes elastic lithium monomers, and the elastic lithium monomers include metallic lithium and / or lithium alloy as an active core, and tubular carbon nanotubes as an elastic outer shell. The elastic outer shells communicate with each other to construct a three-dimensional network channel, and there are protrusions formed by tubular carbon nanotubes on the surface of the lithium-carbon material layer.

2. The solid-state battery according to claim 1, characterized in that, The alloying elements in the lithium alloy include at least one of boron, silicon, aluminum, gallium, antimony, silver, tin, indium, magnesium, or gold, and the mass fraction of lithium in the lithium alloy is not less than 50%.

3. The solid-state battery according to claim 1 or 2, characterized in that, The tubular carbon nanotubes include at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, or doped carbon nanotubes, preferably a combination of single-walled carbon nanotubes and at least one carbon nanotube selected from double-walled carbon nanotubes, multi-walled carbon nanotubes, and modified carbon nanotubes; Preferably, the doping elements in the doped carbon nanotubes include at least one of nitrogen, oxygen, sulfur, aluminum, silver, silicon, magnesium, tin, or zinc; Preferably, the lithium-carbon material layer further includes linear carbon nanotubes, preferably carbon nanofibers and / or modified carbon nanofibers; the ratio of the tubular carbon nanotubes to the linear carbon nanotubes is 1:(0.1-10), preferably 1:(0.5-5).

4. The solid-state battery according to any one of claims 1 to 3, characterized in that, The average thickness of the elastic outer shell is 0.05-10 μm, preferably 0.5-5 μm; Preferably, based on the total mass of the lithium-carbon material layer being 100%, the mass fraction of the elastic outer shell is 0.05-50%, preferably 0.25%-30%; Preferably, the elastic outer shell further includes elastic fillers, and the elastic fillers include thermoplastic elastic materials and conductive materials. The mass ratio of the thermoplastic elastic materials to the conductive materials is (0.1-10): (90-99.9), preferably (0.5-5):(95-99.5), more preferably (1-3);(97-99); Preferably, based on the total mass of the lithium-carbon material layer being 100%, the mass fraction of the elastic fillers is below 5%, preferably 0.5-3%; Preferably, the surface roughness Ra of the lithium-carbon material layer is greater than 0.3 μm, preferably Ra is 0.5-5 μm; Preferably, the peeling force between the lithium-carbon material layer and the current collector is greater than 0.2 kgf, preferably 0.5-5 kgf; Preferably, the N / P ratio of the lithium-carbon material layer to the positive electrode active material layer is 0.9-1.25, preferably 1.05-1.

15.

5. The solid-state battery according to any one of claims 1-4, characterized in that, The positive electrode active material layer includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium cobalt oxide, sublimated sulfur, sulfided polyacrylonitrile, vanadium pentoxide or MS2 (M = Fe, Mn, Mo, V, Ti, Co or Cr); Preferably, an elastic functional layer is further provided on the surface of the positive electrode active material layer, and the elastic functional layer comprises a thermoplastic elastic material and a conductive material; Preferably, the thermoplastic elastic material includes at least one of styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS); the conductive material includes at least one of Ketjen black, acetylene black, Cabot black, conductive graphite, Super P, graphene, graphene oxide, mesophase carbon microbeads, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, nanocarbon fibers or nanometal particles.

6. The solid-state battery with an electrode structure according to any one of claims 1-5, characterized in that The current collector includes a basic current collector and a modified current collector, wherein the basic current collector includes at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, carbon nanotube paper or carbon fiber paper; The modified current collector includes a base current collector and a coating disposed on a surface of the base current collector, wherein the coating includes at least one of graphene, graphene oxide, chromate, manganese oxide, or aluminum oxide.

7. The solid-state battery according to any one of claims 1-6, characterized in that, The solid electrolyte in the solid electrolyte layer includes at least one of a polymer solid electrolyte, an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte or a composite solid electrolyte.

8. A method for preparing a solid-state battery according to any one of claims 1-7, characterized in that, The method comprises the following steps: (1) The positive electrode active material, the conductive agent and the binder are mixed and arranged on one side of the current collector; or the lithium carbon material is arranged on one side of the current collector; (2) placing a material containing an active material having a polarity opposite to that in step (1) on the other side of the current collector to obtain a bipolar electrode; (3) The bipolar electrodes obtained in step (2) are stacked via a solid electrolyte layer to obtain a stack, wherein the outermost electrode of the stack is a unipolar electrode, and the polarity of the active material on the unipolar electrode is opposite to the polarity of the active material in the adjacent electrode structure, and then packaged to obtain the solid-state battery.

9. The method according to claim 8, wherein The method comprises the following steps: (a) preparing a positive electrode active material, a conductive agent and a binder into a positive electrode active material layer by a dry process, and then placing it on one side of a current collector by mechanical rolling and / or bonding process; (b) disposing the lithium carbon material on the other side of the current collector in step (1) by any one of mechanical rolling, twisting, spraying or stamping, or a combination of at least two of them, to obtain the bipolar electrode structure; (c) stacking the bipolar electrode structure and the solid electrolyte to obtain a stack, wherein the outermost electrode of the stack is a unipolar electrode, and the polarity of the active material on the unipolar electrode is opposite to the polarity of the active material in the adjacent electrode structure, and then isostatically pressing to obtain the solid-state battery.

10. The method according to claim 9, wherein The isostatic pressing encapsulation in step (c) includes cold isostatic pressing, warm isostatic pressing, or a combination of both.

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