All-solid-state batteries, battery packs and electrical equipment

Abstract

The present invention provides an all-solid-state battery, a battery pack and an electrical device. The all-solid-state battery of the present invention comprises a staggered stacked negative electrode sheet and a positive electrode sheet, a solid electrolyte layer is included between the negative electrode sheet and the positive electrode sheet, the outermost side of the all-solid-state battery is a negative electrode sheet, the outermost negative electrode sheet comprises a negative electrode collector and a negative electrode active material layer and a ceramic layer respectively arranged on the two side surfaces of the negative electrode collector, and the ceramic layer is located on the side surface of the negative electrode collector away from the positive electrode sheet. The present invention designs the outermost layer of the battery as a ceramic layer, and utilizes the good rigidity and hardness of the ceramic layer itself, so that when the battery is subjected to a large pressure during the isostatic pressing process, it can ensure uniform force, make the pressing surface flat, and not easily cause the outer packaging film to rupture, and will not cause the battery to tear during the subsequent restraint and pressurization process, so that the battery has good initial efficiency and cycle performance.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state batteries and relates to an all-solid-state battery, a battery pack and an electrical device. Background Art

[0002] Driven by the large-scale application of electric vehicles around the world, lithium-ion batteries have experienced rapid development. Currently, existing liquid lithium-ion batteries are close to the limit of their energy density, and their liquid electrolytes are flammable and explosive, resulting in low battery safety performance. Compared with liquid batteries, solid-state batteries have higher safety performance and energy density. In addition, they also have certain advantages in power characteristics and temperature adaptability, and are expected to significantly improve the range and charging performance of electric vehicles.

[0003] In the production process of all-solid-state batteries, the positive electrode sheet, solid electrolyte and negative electrode sheet are generally stacked together for assembly. In order to form a good solid-solid contact interface between the solid electrolyte and the electrode and avoid contact loss and lithium dendrite formation during the cycle, it is necessary to apply high pressure during stacking to make the materials densely stacked. The pressure provided by traditional hot pressing, roller pressing and other methods is limited and the pressure is uneven, which makes it difficult to ensure the consistency requirements of dense stacking, thus adversely affecting the performance of the battery. The isostatic pressing technology is based on the Pascal principle. The powder of the pressed part is placed in a high-pressure container. The incompressible and uniform pressure transmission properties of the liquid or gas medium are used to uniformly pressurize the workpiece from all directions, so that the powder is subjected to the same pressure in all directions, thereby realizing the forming of a high-density and high-uniformity blank. The isostatic pressing technology can make different types of materials such as metals, ceramics, composite materials and polymers dense and eliminate pores. For all-solid-state batteries, the isostatic pressing technology can effectively eliminate the gaps inside the battery, improve the contact effect between the interfaces of the components in the battery, and thus enhance the conductivity and increase the energy density.

[0004] When isostatic pressing an all-solid-state battery, the pressure generally exceeds 400Mpa, which can easily cause the battery to break and become scrapped. In order to ensure that the battery is evenly stressed during isostatic pressing and avoid breaking, it is usually necessary to set a stainless steel or aluminum splint between the battery packaging film and the electrode assembly. However, after the splint is set, the splint can easily puncture the packaging film during isostatic pressing, causing the battery to short-circuit and become unusable. In addition, if the pressure-bearing capacity of the all-solid-state battery is low, the subsequent restraint and pressurization process will also cause uneven pressure distribution inside the battery, which is detrimental to the battery's initial efficiency and cycle performance. Summary of the invention

[0005] In view of the above-mentioned defects, the present invention provides an all-solid-state battery, a battery pack and an electrical device. The present invention designs the outermost layer of the battery to be a ceramic layer, and utilizes the good rigidity and hardness of the ceramic layer itself to ensure uniform force when the battery is subjected to a large pressure during the isostatic pressing process, so that the pressing surface is flat, the outer packaging film is not easily broken, and the pressing surface is kept flat during the subsequent restraint and pressurization process, so that the battery has good initial efficiency and cycle performance.

[0006] The present invention provides an all-solid-state battery, comprising a staggered stacked negative electrode sheet and a positive electrode sheet, wherein a solid electrolyte layer is provided between the negative electrode sheet and the positive electrode sheet, the outermost side of the all-solid-state battery is the negative electrode sheet, the outermost negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer and a ceramic layer respectively provided on both side surfaces of the negative electrode current collector, and the ceramic layer is located on the side surface of the negative electrode current collector facing away from the positive electrode sheet.

[0007] The all-solid-state battery as described above, wherein the ceramic layer satisfies at least one of the following conditions:

[0008] (1) Mohs hardness is 3~10;

[0009] (2) Poisson’s ratio is 0.1 to 0.5;

[0010] (3) Density is 50%~90%;

[0011] (4) Elastic modulus is 2~10GPa.

[0012] In the all-solid-state battery as described above, the thickness of the ceramic layer is 30 μm to 150 μm.

[0013] The all-solid-state battery as described above, wherein the ceramic layer comprises ceramic particles and a binder;

[0014] Based on the total mass of the ceramic layer, the mass content of the ceramic particles is 40% to 80%, and the mass content of the binder is 1% to 10%.

[0015] The all-solid-state battery as described above, wherein the ceramic particles include one or more of aluminum oxide, zirconium oxide, boehmite, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium aluminum titanium phosphate, titanium dioxide, silicon carbide, silicon oxide, and silicon nitride.

[0016] In the all-solid-state battery as described above, the particle size D50 of the ceramic particles is 0.1-3 μm.

[0017] The all-solid-state battery as described above, wherein the ceramic layer is prepared by a method comprising the following process:

[0018] Ceramic particles and a binder are added to a solvent and mixed to obtain a ceramic slurry; the ceramic slurry is coated on one side surface of the negative electrode current collector, and the ceramic layer is obtained after heat treatment and roll pressing treatment in sequence.

[0019] The all-solid-state battery as described above, wherein the heat treatment comprises a first heat treatment and a second heat treatment performed sequentially;

[0020] The temperature of the first heat treatment is 60-200°C, and the temperature of the second heat treatment is 300-800°C.

[0021] The all-solid-state battery as described above, wherein the pressure of the roller pressing process is 5-50 MPa.

[0022] The present invention also provides a battery pack, comprising the all-solid-state battery as described above.

[0023] The present invention also provides an electrical device, comprising the all-solid-state battery or the battery pack as described above.

[0024] The implementation of the present invention has at least the following beneficial effects:

[0025] The present invention makes a special design for the all-solid-state battery structure, designs the outermost layer of the all-solid-state battery as a ceramic layer, and utilizes the high rigidity and hardness of the ceramic layer itself to ensure uniform force when the battery is subjected to a large pressure during the isostatic pressing process, so that the pressing surface is flat, the outer packaging film is not easily broken, and the surface remains flat during the subsequent restraint and pressurization process, so that the battery has good initial efficiency and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of an all-solid-state battery according to an embodiment of the present invention.

[0027] Description of reference numerals:

[0028] 1-negative electrode sheet; 11-negative electrode current collector; 12-ceramic layer; 13-negative electrode active material layer;

[0029] 2-positive electrode sheet; 21-positive electrode current collector; 22-positive electrode active material layer;

[0030] 3- Solid electrolyte layer. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides an all-solid-state battery, comprising a staggered stacked negative electrode sheet and a positive electrode sheet, a solid electrolyte layer between the negative electrode sheet and the positive electrode sheet, the outermost side of the all-solid-state battery being the negative electrode sheet, wherein the outermost negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer and a ceramic layer respectively arranged on both side surfaces of the negative electrode current collector, wherein the ceramic layer is located on the side surface of the negative electrode current collector facing away from the positive electrode sheet.

[0033] In the present invention, the staggered stacking of negative and positive electrodes refers to the state that the battery is in a state where the negative and positive electrodes are adjacent, and a solid electrolyte layer is arranged between each pair of adjacent positive and negative electrodes. The present invention does not limit the number of positive and negative electrodes, the number of positive electrodes is at least one, and the number of negative electrodes is at least two. The specific number of positive and negative electrodes can be determined according to the design capacity of the battery. Compared with arranging the positive electrode sheet at the outermost side of the battery, arranging the negative electrode sheet at the outermost side of the battery can ensure that the lithium ions released from the positive electrode active material layer can be received by the negative electrode active material layer, thereby avoiding unnecessary loss of battery energy density. Among them, when the number of negative electrode sheets exceeds two, the all-solid-state battery includes a negative electrode sheet located inside the battery and a negative electrode sheet located at the outermost side of the battery, wherein both side surfaces of the negative electrode sheet located inside the battery are provided with a negative electrode active material layer, and both side surfaces of the negative electrode sheet located at the outermost side of the battery are provided with a negative electrode active material layer and a ceramic layer, wherein the ceramic layer is located on the side surface of the negative electrode current collector away from the positive electrode sheet.

[0034] Figure 1 FIG. 1 is a schematic diagram of the structure of an all-solid-state battery according to an embodiment of the present invention. Figure 1 In the example shown, the all-solid-state battery includes two negative electrode sheets 1 located on the outermost sides of the battery and a positive electrode sheet 2 arranged between the two negative electrode sheets 1, and also includes a solid electrolyte layer 3 between the negative electrode sheet 1 and the positive electrode sheet 2, wherein the outermost negative electrode sheet 1 includes a negative electrode collector 11 and a ceramic layer 12 and a negative electrode active material layer 13 respectively located on the two side surfaces of the negative electrode collector 11, and the positive electrode sheet 2 includes a positive electrode collector 21 and a positive electrode active material layer 22 arranged on the two side surfaces of the positive electrode collector 21, wherein the ceramic layer 12 is arranged on the side surface of the negative electrode collector 11 facing away from the positive electrode sheet 2, and the negative electrode active material layer 13 is arranged on the side surface of the negative electrode collector 11 facing the positive electrode sheet 2, so as to receive the active lithium released from the positive electrode active material layer 22.

[0035] The present invention makes a special design for the battery structure, designs the outermost layer of the battery as a ceramic layer, and utilizes the high rigidity and hardness of the ceramic layer itself to ensure uniform force when the battery is subjected to a large pressure during the isostatic pressing process, so that the pressing surface is flat, the outer packaging film is not easily broken, and the surface remains flat during the subsequent restraint and pressurization process, so that the battery has good initial efficiency and cycle performance.

[0036] In addition, after the isostatic pressing process is completed, the traditional splint needs to open the outer packaging film to take out the splint and then re-seal it, which is a relatively complicated process. The outermost ceramic layer of the present invention is designed as an integral part of the battery, which not only makes the pressure more uniform, but also does not need to be taken out and re-sealed after the isostatic pressing process is completed, which simplifies the manufacturing process. When the battery is hit by external force or pierced by foreign objects, the outermost ceramic layer can also play a barrier role to avoid battery short circuit and enhance the safety performance of the battery.

[0037] In a preferred embodiment, the ceramic layer satisfies at least one of the following conditions:

[0038] (1) Mohs hardness is 3~10;

[0039] (2) Poisson’s ratio is 0.1 to 0.5;

[0040] (3) Density is 50%~90%;

[0041] (4) Elastic modulus is 2~10GPa.

[0042] The Mohs hardness, Poisson's ratio, density and elastic modulus of the ceramic layer are key factors affecting the isostatic pressing effect of the battery.

[0043] Among them, Mohs hardness is a parameter that characterizes the hardness of a material. It usually uses a scratching method to scratch the surface of the tested material with a pyramidal diamond needle, and measures the depth of the scratch. The depth of the scratch is the Mohs hardness. The Mohs hardness is generally divided into 1 to 10 levels. The larger the value, the greater the hardness of the material. When the Mohs hardness of the ceramic layer is 3 to 10, it is beneficial to maintain good flatness when subjected to isostatic pressure, and it is not easy to deform the battery. More preferably, the Mohs hardness is 5 to 8.

[0044] Poisson's ratio refers to the ratio of the absolute value of the lateral normal strain to the axial normal strain when the material is subjected to unidirectional compression or tension. It is an elastic parameter that reflects the lateral deformation of the material. Its value range is between -1 and 0.5. Integers indicate that the material will shrink in the lateral direction when subjected to force, and negative numbers indicate that it will expand. Among them, 0.5 is the maximum theoretical value, which means that the material will not change in volume when subjected to unidirectional compression or tension. The present invention can ensure that the ceramic layer has greater rigidity by controlling the Poisson's ratio of the ceramic layer within 0.1~0.5, more preferably within 0.1~0.3, so that the battery is not easily deformed during the isostatic pressing process.

[0045] The density of the ceramic layer refers to the ratio of the actual density of the ceramic layer to the theoretical density, wherein the actual density can be obtained by an electronic density meter prepared based on the Archimedean drainage method. The present invention controls the density of the ceramic layer to be within the range of 50% to 90%, more preferably within the range of 60% to 90%, which is beneficial to improving the hardness and mechanical properties of the ceramic layer.

[0046] The elastic modulus refers to the ratio of the axial stress to the axial strain of the material in the elastic deformation stage, also known as Young's modulus. The elastic modulus can be regarded as an indicator to measure the difficulty of elastic deformation of the material. The larger its value, the greater the stress for causing a certain elastic deformation of the material, that is, the greater the rigidity of the material, the smaller the elastic deformation under a certain stress. The present invention can also ensure that the ceramic layer has greater rigidity by controlling the elastic modulus of the ceramic layer within the range of 2 to 10 GPa, more preferably within the range of 3 to 8 GPa, and is not easy to deform the battery during the isostatic pressing process.

[0047] In a specific embodiment, the thickness of the ceramic layer is 30-150 μm, preferably 50-100 μm. It is understandable that the greater the thickness of the ceramic layer, the more conducive it is to resisting the adverse strain that is prone to occur in the battery during isostatic pressing, but excessive thickness will inevitably lead to damage to the energy density of the battery. Therefore, controlling the ceramic layer within the above-mentioned thickness range can enable it to play a protective role while also enabling the battery to have excellent energy density. Exemplarily, the thickness of the ceramic layer can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, etc.

[0048] In a specific embodiment, the ceramic layer includes ceramic particles and a binder; based on the total mass of the ceramic layer, the mass content of the ceramic particles is 40% to 80%, and the mass content of the binder is 1% to 10%. By making the ceramic layer include ceramic particles and a binder in the above mass content range, the ceramic layer can maintain high rigidity and hardness while also having good bonding properties with the surface of the negative electrode current collector.

[0049] The present invention does not specifically limit the type of ceramic particles, which can be selected from ceramic materials commonly used in the art, including but not limited to one or more of alumina, zirconium oxide, boehmite, lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium aluminum titanium phosphate (LATP), titanium dioxide, silicon carbide, silicon oxide, and silicon nitride.

[0050] If the particle size of ceramic particles is too small, they are easy to agglomerate during the pulping process; if the particle size of ceramic particles is too large, it is difficult to form a dense accumulation in the ceramic layer, which is not conducive to bearing a large isostatic pressure. For the above considerations, the particle size D50 of the ceramic particles is controlled to be 0.1~3μm. For example, it can be 0.1μm, 0.3μm, 0.5μm, 1.0μm, 1.5μm, 2.0μm, 2.5μm, 3.0μm, etc.

[0051] The present invention does not specifically limit the type of the adhesive, which can be selected from adhesives commonly used in the art, such as acrylic adhesives.

[0052] In a specific embodiment, the ceramic layer can be prepared by a method comprising the following steps:

[0053] Ceramic particles and a binder are added to a solvent and mixed to obtain a ceramic slurry; the ceramic layer is coated on one side surface of a negative electrode current collector, and the ceramic layer is obtained after heat treatment and roller pressing treatment in sequence.

[0054] In order to fully disperse the ceramic particles and the binder in the solvent, a dispersant may be added during the slurry preparation process.

[0055] Specifically, the dispersant can be selected from one or more of silicate dispersants, alkali metal phosphate dispersants, and organic dispersants. Among them, the organic dispersant includes but is not limited to one or more of triethylhexyl phosphoric acid, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, guar gum, and fatty acid polyethylene glycol esters.

[0056] Furthermore, the mass ratio of the ceramic particles to the dispersant is 10:(0.1-3). The mass ratio can be selected within the above range according to the dispersing capacity of the dispersant and the type of ceramic particles.

[0057] The present invention does not particularly limit the solvent used to disperse the ceramic particles and the binder, and specifically may include but is not limited to one or more of water, N-methylpyrrolidone (NMP), xylene, anisole, butyl butyrate, isobutyl isobutyrate, N,N-dimethylformamide (DMF), acetonitrile, etc.

[0058] In a specific embodiment, the solid content of the prepared ceramic slurry can be controlled to be 30wt%~90wt%, more preferably 40wt%~80wt%. The greater the solid content of the slurry, the greater the viscosity and the more difficult it is to coat. Controlling the solid content of the ceramic slurry within the above range is conducive to coating the slurry.

[0059] Heat treatment is the process of drying the slurry to form a solid ceramic layer. In a preferred embodiment, the heat treatment includes a first heat treatment and a second heat treatment performed in sequence, wherein the temperature of the first heat treatment is 60-200°C and the temperature of the second heat treatment is 300-800°C. Performing the first heat treatment at a lower temperature is conducive to the volatilization of the solvent and the drying process of the slurry; performing the second heat treatment at a higher temperature is conducive to the densification of the ceramic particles and enhancing the density of the ceramic layer.

[0060] The ceramic layer can be further densified by roller pressing and its surface can be made smoother. In a preferred embodiment, the pressure of the roller pressing is 5-50 MPa, more preferably 10-40 MPa.

[0061] The present invention does not specifically limit the type of negative electrode current collector, and the negative electrode current collector conventionally used in the art may be selected, including but not limited to copper foil, carbon-coated copper foil, etc.

[0062] In a specific embodiment, the negative electrode active material layer mainly comprises the negative electrode active material, and in addition, it may further comprise components such as a conductive agent and a binder.

[0063] Specifically, the negative electrode active material includes but is not limited to one or more of graphite, silicon-carbon material, silicon-oxygen material, and elemental silicon; the conductive agent includes but is not limited to one or more of conductive carbon black, Super-C, acetylene black, Ketjen black, and carbon nanofibers; the binder includes but is not limited to one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinyl pyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR), and hydrogenated nitrile rubber (HNBR).

[0064] In a specific embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surfaces of both sides of the positive electrode current collector. The positive electrode current collector can be selected from the positive electrode current collectors conventionally used in the art, such as aluminum foil; the main component of the positive electrode active material layer is the positive electrode active material, in addition, it may also include components such as a conductive agent and a binder. Specifically, the conductive agent and the binder can refer to the selection of the conductive agent and the binder in the negative electrode sheet, which will not be repeated here. The positive electrode active material can be selected from the positive electrode active materials conventionally used in the art, including but not limited to one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0065] The solid electrolyte layer of the present invention includes a solid electrolyte. The present invention does not specifically limit the type of the solid electrolyte, and it may be, for example, a sulfide electrolyte.

[0066] In a specific embodiment, the all-solid-state battery of the present invention can be prepared by the following method:

[0067] 1) Preparation of positive electrode sheet: The positive electrode active material, conductive agent and binder are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on both sides of the positive electrode current collector, and the positive electrode sheet is obtained after drying, rolling and cutting;

[0068] 2) Preparation of negative electrode sheet: Disperse the negative electrode active material, conductive agent and binder in a solvent to form a negative electrode active material layer slurry, apply the negative electrode active material layer slurry to one side of the negative electrode current collector, disperse ceramic particles and binder in a solvent to form a ceramic slurry, apply the ceramic slurry to the other side of the negative electrode current collector, dry, roll and cut to obtain a negative electrode sheet;

[0069] 3) Preparation of solid electrolyte layer: Disperse the solid electrolyte and the binder in a solvent to form a solid electrolyte layer slurry, apply the solid electrolyte layer slurry on a substrate, and dry it to form a solid electrolyte layer.

[0070] 4) Transferring the solid electrolyte layer from the substrate surface to the surface of the negative electrode sheet including the negative electrode active material layer.

[0071] 5) Battery assembly: Alternately stack the negative electrode sheets and positive electrode sheets including the solid electrolyte layer, with the solid electrolyte layer located between the negative electrode sheet and the positive electrode sheet, with the negative electrode sheet located on the outermost side of the battery, and with the ceramic layer of the negative electrode sheet facing away from the positive electrode sheet. After packaging, isostatic pressing is performed to obtain an all-solid-state battery.

[0072] Furthermore, the temperature of the isostatic pressing treatment is 25~150°C and the pressure is 400~800Mpa.

[0073] Furthermore, when the all-solid-state battery also includes a negative electrode sheet located between two positive electrode sheets, the negative electrode sheet is obtained by coating the negative electrode active material layer slurry on both side surfaces of the negative electrode collector, and then drying, rolling and slitting.

[0074] The second aspect of the present invention provides a battery pack, comprising the all-solid-state battery provided by the first aspect of the present invention. In addition to the all-solid-state battery, the battery pack of the present invention may also include a housing, etc. Specifically, a plurality of all-solid-state batteries may be assembled in the housing to form a battery pack. The number of all-solid-state batteries may be selected according to different battery pack capacity requirements.

[0075] Since the battery pack of the present invention includes the above-mentioned all-solid-state battery, it has both excellent first efficiency and cycle performance.

[0076] The third aspect of the present invention provides an electrical device, including the all-solid-state battery provided by the first aspect of the present invention or the battery pack provided by the second aspect of the present invention. The present invention does not specifically limit the type of electrical device, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric cars, electric toys, energy storage devices, etc.

[0077] The all-solid-state battery provided by the present invention will be described in detail below in conjunction with specific embodiments.

[0078] Example 1

[0079] This embodiment provides an all-solid-state battery, whose battery structure is similar to Figure 1 The all-solid-state battery is consistent, comprising two negative electrode sheets 1 and one positive electrode sheet 2, wherein the two negative electrode sheets 1 are located at the outermost sides of the battery, a positive electrode sheet 2 is located between the two negative electrode sheets 1, and a solid electrolyte layer 3 is also provided between the negative electrode sheet 1 and the positive electrode sheet 2. The preparation method of the all-solid-state battery comprises the following steps:

[0080] 1. Preparation of negative electrode sheet 1

[0081] 1) Ceramic particles of alumina with a particle size D50 of 0.2 μm, dispersant methyl pentanol, and binder polyacrylic acid are mixed in a mass ratio of 88:7:5, dispersed in solvent water to obtain a ceramic slurry with a solid content of 70 wt%. The ceramic slurry is applied on one side of the copper foil of the negative electrode collector 11, and after a first heat treatment at 120°C for 6 hours, the temperature is raised to 500°C for a second heat treatment for 3 hours, and then rolled at a pressure of 30 MPa to form a ceramic layer 12 with a thickness of 50 μm.

[0082] 2) Pure silicon, conductive agent acetylene black, and binder CMC are dispersed in solvent water at a mass ratio of 97.5:0.5:2 to obtain a negative electrode active material layer slurry with a solid content of 46%. The negative electrode active material layer slurry is coated on the other side surface of the copper foil of the negative electrode collector 11, and then dried and rolled to form a negative electrode active material layer 13, thereby obtaining a negative electrode sheet 1.

[0083] 2. Preparation of positive electrode sheet 2

[0084] The positive electrode active material single crystal ternary NCM811, the conductive agent acetylene black, and the binder HNBR are dispersed in the solvent xylene at a mass ratio of 94.5:0.5:5 to obtain a positive electrode active material layer slurry with a solid content of 75%. The positive electrode active material layer slurry is coated on the two side surfaces of the positive electrode collector 21 aluminum foil, and the positive electrode sheet 2 is obtained after drying and rolling.

[0085] 3. Preparation of solid electrolyte layer 3

[0086] The sulfide electrolyte Li6PS5Cl (LPSCl) and the binder SBR are dispersed in a solvent xylene at a mass ratio of 99:1 to obtain a solid electrolyte layer slurry with a solid content of 60%. The solid electrolyte layer slurry is coated on the surface of an aluminum foil substrate and dried to form a solid electrolyte layer 3. The solid electrolyte layer 3 is transferred from the aluminum foil substrate to the surface of the negative electrode sheet 1 provided with a negative electrode active material layer 13.

[0087] 4. Battery assembly

[0088] A negative electrode sheet 1 including a solid electrolyte layer 3, a positive electrode sheet 2, and a negative electrode sheet 1 including a solid electrolyte layer 3 are stacked in sequence, and the ceramic layer 12 in the negative electrode sheet 1 is located on the outermost side, and the solid electrolyte layer 3 is located between the negative electrode sheet 1 and the positive electrode sheet 2 to obtain an electrode assembly, and the electrode assembly is packaged in an aluminum-plastic film, and isostatic pressing is performed at 80°C and 500Mpa to obtain an all-solid-state battery.

[0089] Embodiments 2 to 13

[0090] The preparation methods of the all-solid-state batteries of Examples 2 to 13 are basically the same as those of Example 1, and the specific differences are listed in Table 1. The rolling pressure of the ceramic layer refers to the rolling pressure performed after the second heat treatment is completed.

[0091] Table 1

[0092]

[0093] In Example 13, "not adopted" means an operation not including the second heat treatment.

[0094] Comparative Example 1

[0095] This comparative example provides an all-solid-state battery, whose battery structure is similar to Figure 1 The difference is that the ceramic layer 12 in the negative electrode sheet 1 is replaced by the negative electrode active material layer 13 , so that both sides of the negative electrode sheet 1 are covered with the negative electrode active material layer 13 .

[0096] Comparative Example 2

[0097] This comparative example provides an all-solid-state battery, whose battery structure is basically the same as that of comparative example 1, except that a stainless steel plate with a thickness of 50 μm is placed on the surfaces of the two outermost negative electrode active material layers 13 .

[0098] Comparative Example 3

[0099] This comparative example provides an all-solid-state battery, whose battery structure is basically the same as that of comparative example 2, except that the position of the clamping plate is replaced from the surface of the negative electrode active material layer 13 to the surface of the aluminum-plastic film.

[0100] Test Case

[0101] 1. The ceramic layer of the negative electrode sheet in the above embodiment is tested for the following parameters:

[0102] 1. Mohs hardness

[0103] Test method: Use a pyramid-shaped diamond needle to scratch the surface of the ceramic layer and measure the depth of the scratch. The depth of the scratch is the Mohs hardness.

[0104] 2. Poisson's ratio

[0105] Test method: Test in accordance with GB / T 22315-2008.

[0106] 3. Elastic modulus

[0107] Test method: Test in accordance with GB / T 22315-2008.

[0108] 4. Density

[0109] Test method: The test is based on the principle of Archimedes drainage method.

[0110] The above test results are shown in Table 2.

[0111] 2. The following performance tests were performed on the all-solid-state batteries of the above embodiments and comparative examples:

[0112] 1. State after isostatic pressing

[0113] Test method: Use naked eyes to observe the damage of the aluminum-plastic film after isostatic pressing, and test the flatness of the battery surface. The flatness of the battery surface is determined by testing the angle between the battery surface and the horizontal plane. An angle of 0-0.5° indicates that the battery surface is intact and flat, an angle of 0.5°-1° indicates that the battery surface is slightly curved, an angle of >1° and <5° indicates that the battery surface is curved, and an angle ≥5° is obviously curved. When the battery is obviously curved during the isostatic pressing process, the battery will be broken during the subsequent restraint and pressurization cycle, causing the battery to short-circuit and be unable to cycle.

[0114] 2. First effect

[0115] Test method: The all-solid-state battery was subjected to equal-gap restraint pressure at 10 MPa, and while maintaining the restraint pressure, the all-solid-state battery was tested at 0.4 mA / cm at 25°C using the LAND battery test system (Wuhan Landian Electronics Co., Ltd.). 2The battery was charged with a constant current of 1.5877 W to 4.2 V, and then charged with a constant voltage until the current dropped to 0.02 C. After standing for 5 minutes, the battery was discharged with a constant current of 0.1 C to 3 V. The first charge capacity Q charge and the first discharge capacity Q discharge of the battery were recorded, and the first charge and discharge efficiency η = E discharge / E charge × 100% was calculated.

[0116] 3. Capacity retention rate after 200 cycles

[0117] Test method: The all-solid-state battery was subjected to equal-gap restraint pressure at 10 MPa, and while maintaining the restraint pressure, the all-solid-state battery was tested at 0.4 mA / cm at 25°C using the LAND battery test system (Wuhan Landian Electronics Co., Ltd.). 2 The battery was charged at a constant current density of 10000 Nm to 4.2 V, and then charged at a constant voltage until the current dropped to 0.02 C. After standing for 5 minutes, the battery was discharged at a constant current of 0.1 C to 3 V. The charge and discharge cycle was repeated 200 times. The first discharge capacity and the discharge capacity at the 200th cycle were recorded. The capacity retention rate after 200 cycles was calculated by dividing the 200th discharge capacity by the first discharge capacity.

[0118] The above test results are shown in Table 3.

[0119] Table 2

[0120]

[0121] Table 3

[0122]

[0123] The following conclusions can be drawn from Tables 2 and 3:

[0124] 1) By comparing Examples 1, 2, 7, and 8, it can be seen that when the ceramic particles are selected from alumina, LLZTO, and LATP, the ceramic layer has a higher Mohs hardness, elastic modulus, lower Poisson's ratio, and higher density. The obtained battery has an intact aluminum-plastic film after isostatic pressing, a flat battery surface, and a higher first efficiency and cycle capacity retention rate. When the ceramic particles are selected from boehmite, the Mohs hardness of the ceramic layer is lower and the Poisson's ratio is relatively high. Although the battery can still maintain an intact aluminum-plastic film and a flat battery surface after isostatic pressing, the first efficiency and cycle capacity retention rate of the battery are significantly reduced. The reason is that boehmite is easy to absorb water, which not only affects the hardness of the ceramic layer, but also has an adverse effect on the first efficiency and cycle performance of the battery.

[0125] 2) By comparing Example 1 and Example 3, it can be seen that when the solid content of the ceramic slurry is 50% and 70%, the ceramic layer has a higher Mohs hardness, a lower Poisson's ratio and a higher density. After isostatic pressing, the aluminum-plastic film is intact, the battery surface is flat, and it has excellent first efficiency and cycle performance.

[0126] 3) By comparing Examples 1, 4, and 12, it can be seen that the change in the thickness of the ceramic layer has no obvious effect on the Mohs hardness, elastic modulus, Poisson's ratio, and density. However, when the thickness of the ceramic layer is relatively small (30 μm), the pressure bearing capacity of the battery becomes weaker, and the battery surface is slightly bent after isostatic pressing. The first efficiency and cycle capacity retention rate of the battery are slightly reduced, and as the thickness of the ceramic layer is further reduced (20 μm), the first efficiency and cycle performance of the battery are seriously reduced.

[0127] 4) By comparing Examples 1 and 6, it can be seen that the rolling pressure of the ceramic layer has an effect on its density. A larger rolling pressure is beneficial to improving the density of the ceramic layer, thereby making the battery more pressure-bearing and having a higher first efficiency and cycle capacity retention rate.

[0128] 5) By comparing Examples 1, 9, 10, and 11, it can be seen that the particle size of the ceramic particles has a significant effect on the Mohs hardness and density of the ceramic layer. As the particle size of the ceramic particles increases, the Mohs hardness of the ceramic layer increases, the density decreases, and the first efficiency and cycle capacity retention rate of the battery also show a gradual downward trend.

[0129] 6) By comparing Examples 1, 5, and 13, it can be seen that when the temperature of the second heat treatment is reduced (300°C), the density and Mohs hardness of the ceramic layer decrease, the thickness of the ceramic layer also increases, and the first efficiency and cycle capacity retention rates of the battery decrease slightly. When the second heat treatment operation is not adopted, the Mohs hardness and density of the ceramic layer will decrease significantly, and the thickness will increase significantly, which will cause the battery surface to be slightly bent after isostatic pressing, and the first efficiency and cycle capacity retention rates will also decrease significantly.

[0130] 7) By comparing Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that the outermost side of the battery of Comparative Example 1 does not include a ceramic layer and is set as a conventional negative electrode active material layer. After isostatic pressing, the aluminum-plastic film is intact, but the battery is obviously bent, and the battery will be broken during the restraint and pressurization process, resulting in a short circuit, and the first effect and cycle performance tests cannot be performed; when a stainless steel clamp is placed on the surface of the outermost negative electrode active material layer on the basis of Comparative Example 1 (Comparative Example 2), after isostatic pressing, although the battery surface is still flat, the aluminum-plastic film is broken, resulting in a short circuit in the battery and cannot be cycled; when the stainless steel clamp is replaced from being built into the battery to being externally placed on the surface of the aluminum-plastic film on the basis of Comparative Example 2, after isostatic pressing, the aluminum-plastic film remains intact, but the surface of the battery cell is slightly bent, and the external stainless steel clamp is not tightly fitted to the internal battery, resulting in difficulty in maintaining a uniform pressure distribution inside the battery during the restraint and pressurization process, thereby significantly deteriorating the first effect and cycle performance of the battery.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An all-solid-state battery, comprising a staggered stack of negative electrode sheets and positive electrode sheets, wherein a solid electrolyte layer is provided between the negative electrode sheets and the positive electrode sheets, It is characterized in that The outermost side of the all-solid-state battery is a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer and a ceramic layer respectively disposed on both sides of the negative electrode current collector, wherein the ceramic layer is located on the side of the negative electrode current collector away from the positive electrode sheet; The ceramic layer meets the following conditions: (1) Mohs hardness is 5~8; (2) Poisson’s ratio is 0.1 to 0.3; (3) Density is 60%~90%; (4) Elastic modulus is 3~8GPa; The thickness of the ceramic layer is 30 μm to 150 μm.

2. The all-solid-state battery according to claim 1, It is characterized in that The ceramic layer includes ceramic particles and a binder; Based on the total mass of the ceramic layer, the mass content of the ceramic particles is 40% to 80%, and the mass content of the binder is 1% to 10%.

3. The all-solid-state battery according to claim 2, It is characterized in that The ceramic particles include one or more of aluminum oxide, zirconium oxide, boehmite, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium aluminum titanium phosphate, titanium dioxide, silicon carbide, silicon oxide, and silicon nitride.

4. The all-solid-state battery according to claim 2, It is characterized in that The particle size D50 of the ceramic particles is 0.1-3 μm.

5. The all-solid-state battery according to claim 2, It is characterized in that The ceramic layer is prepared by a method comprising the following steps: Ceramic particles and a binder are added to a solvent and mixed to obtain a ceramic slurry; the ceramic slurry is coated on one side surface of the negative electrode current collector, and the ceramic layer is obtained after heat treatment and roll pressing treatment in sequence.

6. The all-solid-state battery according to claim 5, It is characterized in that The heat treatment includes a first heat treatment and a second heat treatment performed sequentially; The temperature of the first heat treatment is 60-200°C, and the temperature of the second heat treatment is 300-800°C.

7. The all-solid-state battery according to claim 5 or 6, It is characterized in that The pressure of the roller pressing treatment is 5-50 MPa.

8. A battery pack, It is characterized in that A fully solid-state battery comprising any one of claims 1 to 7.

9. An electrical device, It is characterized in that It comprises the all-solid-state battery according to any one of claims 1 to 7 or the battery pack according to claim 8.

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