Electrode plate and preparation method thereof, solid-state battery and power utilization device

Abstract

The invention provides an electrode plate and a preparation method thereof, a solid-state battery and an electric device, and relates to the technical field of batteries. The electrode plate comprises a current collector and an electrode film layer attached to at least one side surface of the current collector, and the electrode film layer comprises a first active material and a second active material; wherein under the multiplying power of 0.5 V-4V and 0.1 C, the volume change rate of the first active material is smaller than or equal to 1.2%, the volume change rate of the second active material is larger than or equal to 2%, and the ratio of the average particle size of the first active material to the average particle size of the second active material is larger than or equal to 6; any 1 mm * 1 mm area in the cross section of the electrode film layer contains a first active material and a second active material. By compounding the first active material with small volume change and relatively large particle size with the second active material with relatively large volume change and relatively small particle size, stable solid-solid interface contact can be formed in the electrode plate, the cycle stability of the solid-state battery can be effectively improved, and the cycle life is prolonged.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to an electrode sheet and its preparation method, a solid-state battery, and an electrical device. Background Technology

[0002] Solid-state batteries boast ultra-high energy density, ultra-high safety, and extremely low manufacturing costs, making them considered the most promising next-generation power batteries. However, the positive and negative electrode materials currently used in solid-state batteries exhibit varying degrees of volume change. For example, the volume change rate of silicon negative electrode materials can reach 300% during charge-discharge cycles, leading to unstable battery structure and short cycle life. Summary of the Invention This application is made in view of the above-mentioned problems, and its purpose is to provide an electrode sheet and its preparation method, a solid-state battery and an electrical device to improve the problems of unstable structure and poor cycle stability of existing solid-state batteries.

[0003] The first aspect of this application provides an electrode sheet, including a current collector and an electrode film layer attached to the surface of the current collector. The electrode film layer includes a first active material and a second active material. Specifically, at a rate of 0.5V to 4V and 0.1C, the volume change rate of the first active material is ≤1.2%, the volume change rate of the second active material is ≥2%, and the ratio of the average particle size of the first active material to the average particle size of the second active material is ≥6. Any 1mm × 1mm region in the cross-section of the electrode film layer contains both the first active material and the second active material.

[0004] In the above technical solution, an electrode film is formed by compounding and pressing a first active material with near-zero volume change (volume change rate ≤ 1.2%) and a large average particle size, and a second active material with a large volume change (volume change rate ≥ 2%) and a small average particle size. The difference in average particle size between the two materials is controlled to be large. The first active material with a larger average particle size is in close contact with each other, and because its volume change is very small, it can serve as a stable "rigid skeleton" for the electrode, fixing the overall structure of the film. The second active material with a smaller average particle size is confined within the stable space formed by the first active material, and its volume change is less likely to cause film peeling or current collector detachment. This effectively improves the cycle stability of the solid-state battery and increases its cycle life.

[0005] In any embodiment, at a voltage of 0.5V to 4V and a rate of 0.1C, the volume change rate of the first active material is ≤0.25%, and the volume change rate of the second active material is ≥5%.

[0006] In the above technical solutions, the second active material with a volume change rate of ≥10% usually has a higher capacity. By combining it with the first active material with a low volume change, the energy density can be increased while improving cycle performance.

[0007] In any embodiment, the electrode sheet includes a positive electrode sheet, the first active material includes at least one of lithium titanate, zero thermal expansion lithium-rich manganese-based material, lithium-titanium-germanium-phosphorus-sulfur-selenium material, lithium iron phosphate, sodium iron phosphate or sodium vanadium phosphate, and the second active material includes a ternary nickel-cobalt-manganese material.

[0008] In the above technical solutions, the volume change rate of lithium titanate, zero thermal expansion lithium-rich manganese-based material, lithium-titanium-germanium-phosphorus-sulfur-selenium material, lithium iron phosphate, sodium iron phosphate or sodium vanadium phosphate is ≤1.2%, the volume change rate of ternary nickel-cobalt-manganese material is ≥2% and has a high theoretical specific capacity, the rigid skeleton formed by the first active material can limit the expansion of the second active material, and the second active material can further improve the energy density of the battery.

[0009] In any embodiment, the electrode sheet includes a negative electrode sheet, the first active material includes lithium titanate, and the second active material includes at least one of graphite and silicon-based materials.

[0010] In the above technical solution, the volume change rate of lithium titanate is close to 0.1%, which is a zero-strain material. It can be used as a rigid substrate to effectively limit the volume expansion of graphite or silicon-based materials. Graphite and silicon-based materials have high theoretical specific capacity. Combining lithium titanate with graphite or silicon-based materials can improve the battery specific capacity and effectively improve cycle performance. In any embodiment, the mass ratio of the first active material to the second active material is (3~9):1, and the ratio of the average particle size of the first active material to the average particle size of the second active material is (50~500):1. In the above technical solution, the first active material accounts for a larger proportion (≥75%) of the second active material, which is beneficial for constructing a robust rigid support framework and suppressing volume changes in the second active material. The second active material has a suitable mass proportion range, which is beneficial for improving battery capacity. Furthermore, by further controlling the ratio of their average particle sizes, the first active material has a larger average particle size, which is beneficial for natural accumulation and contact in the electrode film layer to form a three-dimensional continuous framework, while the second active material with a smaller average particle size can effectively fill the gaps between the first active materials, which is beneficial for improving the density of the electrode and the interface contact, thereby further improving the cycle stability of the battery.

[0011] In any embodiment, the average particle size of the first active material is 1 μm to 20 μm, and the average particle size of the second active material is 10 nm to 3 μm.

[0012] In the above technical solution, the use of a micron-sized first active material is beneficial for forming a three-dimensional continuous rigid support framework, while the use of a nano / submicron-sized second active material can be suitable for filling the gaps in the first active material, which is beneficial for improving the density of the electrode and the interface contact, thereby further improving the cycle stability of the battery.

[0013] In any embodiment, the sum of the masses of the first active material and the second active material is 60wt% to 90wt% based on the total mass of the electrode film.

[0014] In the above technical solution, by controlling the mass ratio of active materials within a suitable range, and ensuring that inactive materials (such as conductive agents, binders, and solid electrolytes) have a certain mass ratio, it is beneficial to further improve the structural integrity and interface stability of the battery, thereby improving the battery's cycle performance while increasing battery capacity.

[0015] In any embodiment, the electrode sheet includes a positive electrode sheet, and the compaction density of the electrode film layer is 3.0 g / cm³. 3 ~3.6g / cm 3 ; and / or, the electrode sheet includes a negative electrode sheet, and the compaction density of the electrode film is 1.2 g / cm³. 3 ~3.4g / cm 3 .

[0016] In the above technical solution, the electrode film layer has a high compaction density, which is beneficial to further improve solid-solid interface contact, reduce interface voids, enhance electrode stability, and thus further improve the cycle performance of the battery.

[0017] The second aspect of this application also provides a method for preparing the electrode sheet provided in the first aspect, comprising the following steps: mixing a first active material, a second active material, a conductive agent and a binder to obtain an electrode slurry; coating the electrode slurry onto at least one side surface of a current collector, drying and pressing to form an electrode sheet.

[0018] In the above technical solution, an electrode slurry is formed by uniformly compounding a first active material, a second active material, and auxiliary materials. After coating and pressing, the second active material fills the gaps in the rigid support framework constructed by the first active material, resulting in a uniform and dense structure of the electrode and good interfacial contact, thereby effectively improving the cycle performance of the battery. This preparation method is simple to operate, requiring only control of the volume change rate and average particle size of the first and second active materials, without complex modification treatment, making it easy to promote and apply in practice.

[0019] In any implementation, the pressing step includes isostatic pressing.

[0020] In the above technical solution, by using isostatic pressing instead of traditional rolling pressing, the isotropic pressure of isostatic pressing can effectively improve compaction density and density uniformity, improve the solid-solid contact effect between various materials in the electrode film, and further improve the cycle performance of the battery.

[0021] In any embodiment, the isostatic pressing treatment is performed at a pressure of 100 MPa to 500 MPa, a temperature of 25°C to 100°C, and a time of 30 s to 600 s.

[0022] In the above technical solution, by controlling the range of process parameters for isostatic pressing, the electrode sheets become dense and uniform, which is beneficial for optimizing interface contact and further improving the cycle performance of the battery.

[0023] A third aspect of this application provides a solid-state battery, including the electrode plates of the second aspect of this application.

[0024] A fourth aspect of this application provides an electrical device including a solid-state battery as described in the third aspect of this application. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an electrode sheet provided in one embodiment of this application.

[0026] Figure 2 The images are scanning electron microscope cross-sectional views of the electrode intermediate and the negative electrode prepared in Example 1 of this application.

[0027] Figure 3 This is a scanning electron microscope cross-sectional image of the negative electrode sheet prepared in Example 1 of this application at a magnification.

[0028] Explanation of reference numerals in the attached drawings: 100-Electrode sheet; 1-Current collector; 2-Electrode film; 20-First active material; 21-Second active material; 22-Auxiliary material. Detailed Implementation

[0029] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the electrode sheet, method for preparing the electrode sheet, solid-state battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0030] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0032] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0033] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0034] Solid-state batteries, with their ultra-high energy density, ultra-high safety, and extremely low manufacturing cost, are considered the most promising next-generation power batteries. In the fabrication of solid-state batteries, stable solid-solid interface contact is crucial for ensuring stable cycle performance.

[0035] However, the positive and negative electrode materials used in current all-solid-state batteries exhibit varying degrees of volume change. Silicon-based materials, in particular, with high capacity, can experience a volume change rate of up to 300% during charge-discharge cycles. This leads to battery structural instability, solid-solid interface contact failure, and short cycle life. Although existing research has attempted to replace elemental silicon with silicon-carbon materials that exhibit smaller volume changes, or to add more binders, these methods have not effectively improved the battery's cycle performance.

[0036] Based on this, the first aspect of the present application provides an electrode sheet, including a current collector and an electrode film layer attached to the surface of the current collector. The electrode film layer includes a first active material and a second active material. Specifically, at a rate of 0.5V to 4V and 0.1C, the volume change rate of the first active material is ≤1.2%, the volume change rate of the second active material is ≥2%, and the ratio of the average particle size of the first active material to the average particle size of the second active material is ≥6. Any 1mm × 1mm region in the cross-section of the electrode film layer contains both the first active material and the second active material.

[0037] In this application, "volume change rate" refers to the relative change in volume of the active material caused by changes in crystal structure or microstructure due to ion insertion or deintercalation during charging and discharging. The volume change rate of the active material can be obtained using conventional testing methods in the art. For example, a coin cell battery after charging and discharging is disassembled, and the volume change is calculated based on lattice parameters using X-ray diffraction (XRD).

[0038] As an example, at a rate of 0.5V to 4V and 0.1C, the volume change rate of the first active material can be between any two values ​​of 0%, 0.1%, 0.3%, 0.5%, 1.0%, 1.2%, or higher; the volume change rate of the second active material can be between any two values ​​of 2%, 5%, 10%, 100%, 300%, or higher.

[0039] Furthermore, at a voltage range of 0.5V to 4V and a rate of 0.1C, the volume change rate of the first active material is ≤0.25%, and the volume change rate of the second active material is ≥5%.

[0040] In this application, "any 1mm×1mm region in the cross-section of the electrode film contains the first active material and the second active material" means that the first active material and the second active material in the electrode film are in a uniform mixed state, rather than a layered structure.

[0041] In this application, an electrode film is formed by compounding and pressing a first active material with near-zero volume change (volume change rate ≤ 1.2%) and a large average particle size, and a second active material with a large volume change (volume change rate ≥ 2%) and a small average particle size. The difference in average particle size between the two materials is controlled to be large. The first active material with a large average particle size is in close contact with each other, and because its volume change is very small, it can serve as a stable "rigid skeleton" for the electrode, fixing the overall structure of the film. The second active material with a small average particle size can be confined within the stable space formed by the first active material, and its volume change is less likely to cause film peeling or current collector detachment. This effectively improves the cycle stability of solid-state batteries and increases cycle life.

[0042] In some embodiments, the mass ratio of the first active material to the second active material is (3~9):1, and the ratio of the average particle size of the first active material to the average particle size of the second active material is (50~500):1. As an example, the mass ratio of the first active material to the second active material is 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or any two of these values; the ratio of the average particle size of the first active material to the second active material is 6, 10, 50, 100, 200, 500, etc.

[0043] In some embodiments, the average particle size of the first active material is 1 μm to 20 μm, and the average particle size of the second active material is 10 nm to 3 μm. As an example, the average particle size of the first active material is within the range of any two values ​​between 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, and above; the average particle size of the second active material is within the range of any two values ​​between 10 nm, 50 nm, 100 nm, 1 μm, 3 μm, and above.

[0044] In some embodiments, the sum of the masses of the first active material and the second active material, based on the total mass of the electrode film, accounts for 60 wt% to 90 wt%. As an example, the sum of the masses of the first active material and the second active material is within the range of any two values ​​between 60 wt%, 70 wt%, 80 wt%, 90 wt%, and above.

[0045] In some embodiments, the electrode film layer further includes auxiliary materials, which may include conductive agents and binders. The auxiliary materials may constitute 1% to 30% of the total mass of the electrode film layer, for example, 1%, 20%, 30%, etc.

[0046] Furthermore, based on the total mass of the electrode film, the mass percentage of the conductive agent can be 0.5% to 10%, for example, 0.5%, 2%, 5%, 7%, 8%, 10%, etc.; the mass percentage of the binder can be 0.5% to 15%, for example, 0.5%, 3%, 5%, 8%, 10%, 15%, etc.

[0047] Furthermore, the auxiliary materials may also include solid electrolytes. The mass percentage of solid electrolytes can be 3% to 40% based on the total mass of the electrode film, for example, 3%, 5%, 10%, 15%, 20%, 30%, 40%, etc.

[0048] Figure 1 For a schematic diagram of an electrode sheet according to one embodiment of this application, please refer to [link / reference]. Figure 1 The electrode sheet 100 includes a current collector 1 and an electrode film layer 2 attached to at least one side surface of the current collector 1. The electrode film layer 2 includes a first active material 20, a second active material 21 and an auxiliary material 22. The average particle size of the first active material 20 is greater than the average particle size of the second active material 21. The second active material 21 fills the gaps in the first active material 20.

[0049] Understandably, the electrode plates in this application may include positive electrode plates or negative electrode plates. Correspondingly, the first active material and the second active material may include positive active material or negative active material. The positive electrode plates and negative electrode plates are described separately below.

[0050] [Positive electrode plate] When the electrode is a positive electrode, the positive electrode includes a positive current collector and a positive electrode film layer attached to at least one side of the positive current collector. The positive electrode film layer includes a first active material, a second active material, and auxiliary materials. In some embodiments, the first active material includes at least one of lithium titanate (volume change rate of approximately 0.1%), zero-thermal-expansion lithium-rich manganese-based material (volume change rate of approximately 0%), lithium-titanium-germanium-phosphorus-sulfur-selenium material (volume change rate of approximately 1.2%), lithium iron phosphate (volume change rate of approximately 0.3%), sodium iron phosphate (volume change rate of approximately 0.5%), or sodium vanadium phosphate (volume change rate of approximately 0.6%). The second active material includes a ternary nickel-cobalt-manganese material (volume change rate between 2% and 6% depending on the mass percentage of nickel).

[0051] This application does not impose any particular restrictions on the specific type of positive electrode current collector. The positive electrode current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate is independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film.

[0052] When the electrode is a positive electrode, the binder in the auxiliary materials may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The conductive agent may be selected from at least one of conductive carbon black (super-P), acetylene black, vapor-grown carbon fiber (VGCF), carbon nanotubes, and graphene. The solid electrolyte may include at least one of sulfide solid electrolyte, oxide solid electrolyte, and organic solid electrolyte.

[0053] In some embodiments, the compaction density of the positive electrode film is 3.0 g / cm³. 3 ~3.6g / cm 3 As an example, the compaction density of the positive electrode film is 3.0 g / cm³. 3 3.1g / cm 3 3.2g / cm 3 3.5g / cm 3 3.6g / cm 3 wait.

[0054] [Negative electrode plate] When the electrode sheet is a negative electrode sheet, the negative electrode sheet includes a negative current collector and a negative electrode film layer attached to at least one side surface of the negative current collector. The negative electrode film layer includes a first active material, a second active material, and auxiliary materials.

[0055] In some embodiments, the first active material includes lithium titanate (volume change rate of about 0.1%), and the second active material includes at least one of graphite (volume change rate of about 10%) and silicon-based material (volume change rate of about 300%).

[0056] In this application, the negative current collector refers to a structure or component that collects current. The negative current collector refers to a conventional current collector structure, which can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. A composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0057] When the electrode sheet is a negative electrode sheet, the binder in the auxiliary materials may include at least one of the following: styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The conductive agent includes at least one of the following: conductive carbon black, conductive graphite, single / multi-walled carbon nanotubes, superconducting carbon, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The dispersant includes at least one of the following: polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC-Na), and lithium carboxymethyl cellulose (CMC-Li). The solid electrolyte may include at least one of the following: sulfide solid electrolyte, oxide solid electrolyte, and organic solid electrolyte.

[0058] In some embodiments, the compaction density of the negative electrode film is 1.2 g / cm³. 3 ~3.4g / cm 3 As an example, the compaction density of the bipolar film layer is 1.2 g / cm³. 3 1.5g / cm 3 2.0g / cm 3 2.5g / cm 3 3.4g / cm 3 wait.

[0059] [Electrode preparation method] The second aspect of this application also provides a method for preparing the electrode sheet provided in the first aspect of this application, comprising the following steps: S10: Mix the first active material, the second active material, the conductive agent and the binder to obtain the electrode slurry.

[0060] In some embodiments, a solid electrolyte, such as at least one of a sulfide solid electrolyte, an oxide solid electrolyte, and an organic solid electrolyte, may be added to the electrode slurry.

[0061] In some embodiments, the mixing method may be: dispersing the first active material, the second active material, the conductive agent and the binder in an organic solvent to form an electrode slurry.

[0062] Further, the organic solvent may be selected from at least one of ether organic solvents, hydrocarbon organic solvents, ester organic solvents, nitrile organic solvents, amide organic solvents, alcohol organic solvents, and halogenated organic solvents. Specifically, the ether organic solvent is selected from at least one of diethyl ether, tetrahydrofuran, and ethylene glycol dimethyl ether; the hydrocarbon organic solvent is selected from at least one of n-pentane, n-hexane, cyclohexane, toluene, xylene, and trimethylbenzene; the ester organic solvent is selected from at least one of ethyl acetate, methyl formate, and dimethyl phthalate; the nitrile organic solvent is selected from acetonitrile; the amide organic solvent is selected from N-methylpyrrolidone (NMP) and / or N,N-dimethylformamide (DMF); the alcohol organic solvent is selected from ethanol; and the halogenated organic solvent is selected from dichloromethane and / or 1,2-dichloroethane.

[0063] S20: The electrode paste is coated on at least one side of the current collector, dried, and then pressed to form an electrode sheet.

[0064] In this application, an electrode slurry is formed by uniformly compounding a first active material, a second active material, and auxiliary materials. After coating, the slurry is pressed, allowing the second active material to fill the gaps in the rigid support framework constructed by the first active material. This results in a uniform and dense structure of the electrode and good interfacial contact, effectively improving the cycle performance of the battery. This preparation method is simple to operate, requiring only control of the volume change rate and average particle size of the first and second active materials, without complex modification treatments, making it easy for practical application.

[0065] In some embodiments, the pressing step includes isostatic pressing. Further, the isostatic pressing pressure is 100 MPa to 500 MPa, the temperature is 25°C to 100°C, and the time is 30 s to 600 s.

[0066] As an example, the isostatic pressure treatment is within the range of any two values ​​of 100MPa, 200MPa, 300MPa, 400MPa, 500MPa or above; the temperature is within the range of any two values ​​of 25℃, 30℃, 50℃, 80℃, 100℃ or above; and the time is within the range of any two values ​​of 30s, 50s, 100s, 200s, 400s, 600s or above.

[0067] Solid-state batteries A third aspect of this application also provides a solid-state battery, including the electrode plates provided in the first aspect of this application.

[0068] Understandably, solid-state batteries typically include a positive electrode, a negative electrode, and a solid electrolyte membrane disposed between the positive and negative electrodes. Since the electrode provided in the first aspect of this application can be either a positive or a negative electrode, in the solid-state battery of this application, both the positive and negative electrodes can use this electrode, or only the positive or negative electrode can use this electrode.

[0069] In some embodiments, the raw material for the solid electrolyte membrane may be selected from at least one of sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, or halide solid electrolytes.

[0070] Among them, solid electrolyte membranes can be prepared from solid electrolytes by dry membrane preparation or wet membrane preparation.

[0071] In some embodiments, the dry membrane fabrication method is as follows: a solid electrolyte is placed in a mold and pressed into a membrane. The pressing method can be cold pressing or hot pressing. The pressing method can be one-step pressing or multi-step pressing. The wet membrane fabrication method is as follows: a solid electrolyte and a binder are mixed in an organic solvent and dispersed into a slurry; the slurry is coated onto a glass substrate, dried, and then pressed to obtain a sulfide electrolyte membrane.

[0072] In some embodiments, the method for preparing a solid-state battery may include the following steps: stacking and pressing a positive electrode, a solid electrolyte membrane, and a negative electrode, encapsulating and forming the solid-state battery.

[0073] [Electrical appliances] The fourth aspect of this application also provides an electrical device, including a solid-state battery according to the third aspect of this application.

[0074] The electrical device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. Another example device could be a mobile phone, tablet, or laptop.

[0075] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0076] Example 1 This embodiment provides a negative electrode sheet, the preparation method of which includes the following steps: (1) Mix 90g lithium titanate particles (average particle size of 10μm), 10g nano silicon particles (average particle size of 50nm), 5g conductive carbon black, 30g sulfide solid electrolyte and 5g binder PVDF with xylene solvent to form a negative electrode slurry.

[0077] (2) The negative electrode slurry is coated on one side of the copper foil of the negative electrode current collector, and after drying, a negative electrode film layer is formed to obtain the electrode intermediate.

[0078] (3) The electrode intermediate is encapsulated with aluminum-plastic film and subjected to isostatic pressing (300MPa, 80℃, 5min) to obtain the negative electrode.

[0079] Example 2 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (1), the average particle size of lithium titanate material is 5 μm, and the average particle size of silicon anode material is 10 nm.

[0080] Example 3 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (1), the average particle size of the lithium titanate material is 20 μm, and the average particle size of the silicon anode material is 1 μm.

[0081] Example 4 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (1), the mass of lithium titanate material is 80g and the mass of silicon anode material is 20g.

[0082] Example 5 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (1), the mass of lithium titanate material is 70g and the mass of silicon anode material is 30g.

[0083] Example 6 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (1), the average particle size of the lithium titanate material is 5 μm and the mass is 80 g, while the average particle size of the silicon anode material is 10 nm and the mass is 20 g.

[0084] Example 7 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: The conditions for the medium static pressure treatment in step (3) are 500 MPa, 80 °C, and 1 min.

[0085] Example 8 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: The conditions for the medium static pressure treatment in step (3) are 50 MPa, 80 °C, and 10 min.

[0086] Example 9 This embodiment provides a negative electrode sheet, the preparation method of which differs from that of Embodiment 1 in that: In step (3), a roller pressing process is used, with conditions including 60t, 80℃, and 5min.

[0087] Comparative Example 1 This comparative example provides a negative electrode sheet, the preparation method of which differs from that of Example 1 in that: The average particle size of the silicon anode material in step (1) is 10 μm.

[0088] Comparative Example 2 This comparative example provides a negative electrode sheet, the preparation method of which differs from that of Example 1 in that: In step (1), graphite is used to replace lithium titanate material.

[0089] Comparative Example 3 This comparative example provides a negative electrode sheet, the preparation method of which includes the following steps: (1) Mix 10g of silicon anode material (average particle size of 50nm), 5g of conductive carbon black, 30g of sulfide solid electrolyte and 5g of binder PVDF with xylene solvent to form a first anode slurry. Coat one side of the copper foil with the first anode slurry and dry to obtain the first anode film.

[0090] (2) 90g of lithium titanate material (average particle size of 10μm), 5g of conductive carbon black, 30g of sulfide solid electrolyte and 5g of binder PVDF are mixed with xylene solvent to form a second negative electrode slurry. The second negative electrode slurry is coated on the surface of the first negative electrode slurry and dried to form a second negative electrode film layer, thus obtaining an electrode intermediate.

[0091] (3) The electrode intermediate is encapsulated with aluminum-plastic film and subjected to isostatic pressing (300MPa, 80℃, 5min) to obtain the negative electrode.

[0092] The preparation parameters of the negative electrode sheet in the above embodiments and comparative examples are shown in Table 1.

[0093] Table 1. Partial fabrication process parameters of the negative electrode sheet

[0094] Performance testing and results analysis 1. Electrode plates (1) The morphology of the electrode intermediate and the negative electrode prepared in Example 1 was observed.

[0095] Figure 2 These are scanning electron microscope (SEM) cross-sectional images of the electrode intermediate (a) and the negative electrode (b) prepared in Example 1 of this application. Figure 2 As can be seen, before isostatic pressing, the electrode intermediate has a loose and porous structure. After isostatic pressing, the electrode forms a dense structure, and good solid-solid contact is formed between the materials.

[0096] Figure 3 This is a scanning electron microscope cross-sectional image of the negative electrode sheet prepared in Example 1 of this application at a magnification. Figure 3 As can be seen, the large-diameter lithium titanate particles and the small-diameter silicon nanoparticles are in close contact with each other, and the silicon nanoparticles fill the gaps between the lithium titanate particles.

[0097] (2) Compacted density The negative electrode sheet is punched into small circular pieces with an area of ​​S1, and its weight is recorded as M1. Its thickness H1 is measured. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, and the weight of the negative electrode current collector copper foil is recorded as M0. Its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (M1 - M0) / S1, the thickness of the negative electrode film layer = H1 - H0, and the compaction density of the negative electrode film layer = single-sided coating weight of the negative electrode film layer / thickness of the negative electrode film layer.

[0098] 2. Battery Using lithium metal sheets as the counter electrode, the negative electrode sheets prepared in the examples and comparative examples were assembled into mold batteries. The cycle performance was tested using a Blue Electric testing system at 25°C and 0-1.5V at rates of 0.1C, 0.33C, and 0.5C. The number of cycles when the capacity decayed to 80% of the initial capacity was recorded as the cycle life. The results of the above performance tests are shown in Table 2.

[0099] Table 2. Performance test results of negative electrode and battery in the examples and comparative examples.

[0100] As can be seen from Tables 1 and 2, compared with Comparative Examples 1 to 3, the batteries prepared in Examples 1 to 9 of this application all have good cycle stability, with a cycle life of ≥450 cycles at 0.1C rate, ≥300 cycles at 0.33C rate, and ≥200 cycles at 0.5C rate.

[0101] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrode sheet, characterized in that, The electrode sheet includes a current collector and an electrode film layer attached to at least one side surface of the current collector, the electrode film layer including a first active material and a second active material; Specifically, at a voltage range of 0.5V to 4V and a rate of 0.1C, the volume change rate of the first active material is ≤1.2%, and the volume change rate of the second active material is ≥2%; the ratio of the average particle size of the first active material to the average particle size of the second active material is ≥6. Any 1mm × 1mm region in the cross-section of the electrode film contains both the first active material and the second active material.

2. The electrode sheet as described in claim 1, characterized in that, The electrode sheet includes a positive electrode sheet, the first active material includes at least one of lithium titanate, zero thermal expansion lithium-rich manganese-based material, lithium-titanium-germanium-phosphorus-sulfur-selenium material, lithium iron phosphate, sodium iron phosphate or sodium vanadium phosphate, and the second active material includes ternary nickel-cobalt-manganese material. And / or, the electrode sheet includes a negative electrode sheet, the first active material includes lithium titanate, and the second active material includes at least one of graphite and silicon-based materials.

3. The electrode sheet as described in claim 1, characterized in that, The mass ratio of the first active material to the second active material is (3~9):1, and the ratio of the average particle size of the first active material to the average particle size of the second active material is (50~500):

1.

4. The electrode sheet as described in claim 1, characterized in that, The average particle size of the first active material is 1 μm to 20 μm, and the average particle size of the second active material is 10 nm to 3 μm.

5. The electrode sheet as described in claim 1, characterized in that, Based on the total mass of the electrode film, the sum of the masses of the first active material and the second active material accounts for 60wt% to 90wt%.

6. The electrode sheet as described in claim 1, characterized in that, The electrode sheet includes a positive electrode sheet, and the compaction density of the electrode film layer is 3.0 g / cm³. 3 ~3.6g / cm 3 ; And / or, the electrode sheet includes a negative electrode sheet, and the compaction density of the electrode film is 1.2 g / cm³. 3 ~3.4g / cm 3 .

7. A method for preparing an electrode sheet as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The first active material, the second active material, the conductive agent, and the binder are mixed to obtain the electrode slurry; Electrode paste is coated onto at least one side of the current collector, dried, and then pressed to form an electrode sheet.

8. The preparation method according to claim 7, characterized in that, The pressing step includes isostatic pressing; Preferably, the isostatic pressing treatment is performed at a pressure of 100MPa to 500MPa, a temperature of 25℃ to 100℃, and a time of 30s to 600s.

9. A solid-state battery, characterized in that, Includes the electrode sheet as described in any one of claims 1 to 6.

10. An electrical device, characterized in that, Including the solid-state battery as described in claim 9.

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