Solid-state battery cell, positive electrode sheet and preparation method therefor, battery device, and electric device

Abstract

The present application provides a solid-state battery cell, a positive electrode sheet and a preparation method therefor, a battery device, and an electric device. The solid-state battery cell of the present application comprises a positive electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector; the positive electrode active layer comprises a first positive electrode active layer located on at least one side of the positive electrode current collector, and a second positive electrode active layer located on the side of the first positive electrode active layer away from the positive electrode current collector and / or the side of the first positive electrode active layer close to the positive electrode current collector; the first positive electrode active layer comprises a positive electrode material; and the second positive electrode active layer comprises a sulfide solid electrolyte. The total content by mass of impurities in the positive electrode active layer is less than or equal to 1.5%. The impurities include: sulfides of one or more of nickel, cobalt, lithium, iron, and phosphorus; oxides of one or more of nickel, cobalt, lithium, iron, and phosphorus; and at least one of elemental sulfur, lithium phosphate, and lithium pyrophosphate. The first coulombic efficiency, specific capacity, and cycle performance of the solid-state battery cell of the present application are simultaneously improved.

Description

Solid-state battery cells, positive electrode sheets and their preparation methods, battery devices and electrical devices

[0001] This application is based on and claims priority to Chinese patent application No. 2025101311434 filed on February 6, 2025, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a solid-state battery cell, a positive electrode, a method for preparing the positive electrode, a battery device, and an electrical device. Background Technology

[0003] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant advancements in battery technology, higher requirements have been placed on their initial efficiency, specific capacity, and cycle performance. Summary of the Invention

[0004] This application provides a solid-state battery cell, a positive electrode, a method for preparing the positive electrode, a battery device, and an electrical device. The solid-state battery cell of this application simultaneously improves its initial efficiency, specific capacity, and cycle performance.

[0005] The first aspect of this application provides a solid-state battery cell, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer located on at least one side of the positive current collector, the positive active layer including a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector, the first positive active layer including a positive electrode material, and the second positive active layer including a sulfide solid electrolyte;

[0006] The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

[0007] Therefore, this application effectively reduces the content of by-product impurities in the positive electrode active layer, and forms a second positive electrode active layer including a sulfide solid electrolyte on at least one side of the first positive electrode active layer, thereby improving the lithium-ion conductivity of the positive electrode active layer material and thus improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0008] In any embodiment, the total mass content of impurities in the positive electrode active layer is ≤1.4%, ≤1.29%, or ≤1%.

[0009] In any embodiment, the mass content of nickel oxide impurities in the positive electrode active layer is ≤1%, ≤0.4%, or ≤0.3%.

[0010] In any embodiment, the mass content of lithium sulfide impurities in the positive electrode active layer is ≤0.7% or ≤0.31%.

[0011] In any embodiment, the mass content of phosphorus sulfide impurities in the positive electrode active layer is ≤0.5% or ≤0.36%.

[0012] In any embodiment, the mass content of lithium phosphate impurities in the positive electrode active layer is ≤0.45% or ≤0.35%.

[0013] In any embodiment, the mass content of elemental sulfur impurities in the positive electrode active layer is ≤1% or ≤0.3%.

[0014] In any embodiment, the mass content of iron sulfide impurities in the positive electrode active layer is ≤0.35%.

[0015] In any embodiment, the mass content of lithium pyrophosphate impurities in the positive electrode active layer is ≤0.4% or ≤0.31%.

[0016] In any embodiment, the mass content of cobalt sulfide impurities in the positive electrode active layer is ≤0.5%.

[0017] In any embodiment, the mass content of cobalt phosphorus sulfide impurities in the positive electrode active layer is ≤0.3%.

[0018] In any embodiment, the impurities in the positive electrode active layer include one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

[0019] In any embodiment, the cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0020] Therefore, when the cathode material includes lithium nickel cobalt manganese oxide, this application suppresses the side reactions between the lithium nickel cobalt manganese oxide material and the sulfide solid electrolyte, effectively reducing the content of by-product impurities such as nickel sulfide, cobalt sulfide, nickel oxide, cobalt oxide, lithium sulfide, lithium oxide, phosphorus sulfide, cobalt phosphorus sulfide, elemental sulfur and / or lithium phosphate in the cathode active layer, improving the lithium-ion conductivity of the cathode active layer material, and improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0021] When the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, this application suppresses the side reactions between lithium iron phosphate and / or lithium manganese iron phosphate and sulfide solid electrolyte, effectively reducing the content of by-product impurities such as lithium sulfide, phosphorus sulfide, elemental sulfur, iron sulfide, lithium phosphate and / or lithium pyrophosphate in the cathode active layer, improving the lithium-ion conductivity of the cathode active layer material, and improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0022] In any embodiment, when the cathode material includes lithium nickel cobalt manganese oxide, the impurities include one or more sulfides of nickel, cobalt, lithium, and phosphorus, one or more oxides of nickel, cobalt, lithium, and phosphorus, elemental sulfur, and at least one of lithium phosphate, and may be selected as one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, and elemental sulfur.

[0023] Therefore, when the cathode material includes lithium nickel cobalt manganese oxide, this application suppresses side reactions between the lithium nickel cobalt manganese oxide material and the sulfide solid electrolyte, reducing the types and / or contents of impurities in the cathode active layer.

[0024] In any embodiment, when the cathode material comprises lithium iron phosphate and / or lithium manganese iron phosphate, the impurities include at least one of iron sulfide, phosphorus sulfide, lithium sulfide, elemental sulfur, lithium phosphate, and lithium pyrophosphate, and may be selected as one or more of Li2S, P2S5, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

[0025] Therefore, when the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, this application suppresses the side reactions between the lithium iron phosphate and / or lithium manganese iron phosphate materials and the sulfide solid electrolyte, reducing the types and / or contents of impurities in the cathode active layer.

[0026] In any embodiment, the thickness ratio of the first positive electrode active layer to the second positive electrode active layer is 100:1-5000:1 or 200:1-1500:1. Therefore, the second positive electrode active layer, including a sulfide solid electrolyte, is beneficial in two ways: firstly, it improves the conductivity of lithium ions in the positive electrode active layer, thereby increasing the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell; secondly, it helps to reduce the impact of increasing the thickness ratio of the second positive electrode active layer in the positive electrode active layer on the energy density of the battery cell.

[0027] In any embodiment, the thickness of the second positive electrode active layer is 100 nm–1 μm or 100 nm–700 nm. Thus, the second positive electrode active layer, including a sulfide solid electrolyte, is beneficial in two ways: firstly, it improves the conductivity of lithium ions in the positive electrode active layer, thereby increasing the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell; secondly, it helps to reduce the impact of increasing the thickness of the second positive electrode active layer on the energy density of the battery cell.

[0028] In any embodiment, the lithium-ion conductivity of the material in the positive electrode active layer is ≥3.4×10⁻⁶. -4 S / cm, or 7.3×10 -4 S / cm – 3.5 × 10 -3 S / cm. Therefore, improving the lithium-ion conductivity of the positive electrode active layer material is beneficial to improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell.

[0029] In any embodiment, the sulfide solid electrolyte includes Li6PS5Cl, Li2S, P2S5, and Li7P3S. 11 Li 10 GeP2S 12 One or more of them.

[0030] A second aspect of this application provides a positive electrode sheet, including a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The first positive active layer includes a positive electrode material, and the second positive active layer includes a sulfide solid electrolyte.

[0031] The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

[0032] Therefore, this application effectively reduces the content of by-product impurities in the positive electrode active layer, and forms a second positive electrode active layer including a sulfide solid electrolyte on at least one side of the first positive electrode active layer, thereby improving the lithium-ion conductivity of the positive electrode active layer material and thus improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0033] In any embodiment, the total mass content of impurities in the positive electrode active layer is ≤1.4%, ≤1.29%, or ≤1%.

[0034] In any embodiment, the mass content of nickel oxide impurities in the positive electrode active layer is ≤1%, ≤0.4%, or ≤0.3%.

[0035] In any embodiment, the mass content of lithium sulfide impurities in the positive electrode active layer is ≤0.7% or ≤0.31%.

[0036] In any embodiment, the mass content of phosphorus sulfide impurities in the positive electrode active layer is ≤0.5% or ≤0.36%.

[0037] In any embodiment, the mass content of lithium phosphate impurities in the positive electrode active layer is ≤0.45% or ≤0.35%.

[0038] In any embodiment, the mass content of elemental sulfur impurities in the positive electrode active layer is ≤1% or ≤0.3%.

[0039] In any embodiment, the mass content of iron sulfide impurities in the positive electrode active layer is ≤0.35%.

[0040] In any embodiment, the mass content of lithium pyrophosphate impurities in the positive electrode active layer is ≤0.4% or ≤0.31%.

[0041] In any embodiment, the mass content of cobalt sulfide impurities in the positive electrode active layer is ≤0.5%.

[0042] In any embodiment, the mass content of cobalt phosphorus sulfide impurities in the positive electrode active layer is ≤0.3%.

[0043] In any embodiment, the impurities in the positive electrode active layer include one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

[0044] In any embodiment, the cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0045] In any embodiment, when the cathode material includes lithium nickel cobalt manganese oxide, the impurities include one or more sulfides of nickel, cobalt, lithium, and phosphorus, one or more oxides of nickel, cobalt, lithium, and phosphorus, elemental sulfur, and at least one of lithium phosphate, and may be selected as one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, and elemental sulfur.

[0046] In any embodiment, when the cathode material comprises lithium iron phosphate and / or lithium manganese iron phosphate, the impurities include at least one of iron sulfide, phosphorus sulfide, lithium sulfide, elemental sulfur, lithium phosphate, and lithium pyrophosphate, and may be selected as one or more of Li2S, P2S5, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

[0047] In any embodiment, the thickness ratio of the first positive electrode active layer to the second positive electrode active layer is 100:1-5000:1 or 200:1-1500:1.

[0048] In any embodiment, the thickness of the second positive electrode active layer is 100nm–1μm or 100nm–700nm.

[0049] In any embodiment, the lithium-ion conductivity of the material in the positive electrode active layer is ≥3.4×10⁻⁶. -4 S / cm, or 7.3×10 -4 S / cm – 3.5 × 10 -3 S / cm.

[0050] In any embodiment, the sulfide solid electrolyte includes Li6PS5Cl, Li2S, P2S5, and Li7P3S. 11 Li 10 GeP2S 12 One or more of them.

[0051] The third aspect of this application provides a method for preparing a positive electrode sheet, which is either method one or method two;

[0052] Method 1 includes the following steps:

[0053] The first positive electrode active layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain a pretreated first positive electrode active layer.

[0054] The pretreated first positive electrode active layer is composited onto at least one side of the positive electrode current collector to obtain a positive electrode sheet;

[0055] The second method includes the following steps:

[0056] The first positive electrode active layer is composited on at least one side of the positive electrode current collector to obtain a composite layer;

[0057] The composite layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain a positive electrode sheet;

[0058] The solvent in the solution containing the sulfide solid electrolyte includes one or more of ethanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and propanol.

[0059] The positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The second positive active layer includes a sulfide solid electrolyte.

[0060] Therefore, this application employs a specific solution including a sulfide solid electrolyte to wet the first positive electrode active layer, and the solvent of the specific solution is not prone to side reactions with the sulfide solid electrolyte, thereby reducing the content of impurity by-products in the positive electrode active layer. A second positive electrode active layer including a sulfide solid electrolyte with high coverage is formed on at least one side of the first positive electrode active layer, which improves the lithium-ion conductivity of the positive electrode active layer material, thereby improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0061] In any embodiment, in method one, after drying, a heat treatment is performed to obtain the pretreated first positive electrode active layer.

[0062] In any embodiment, in method two, the positive electrode sheet is obtained by heating after drying.

[0063] In any embodiment, the temperature of the heat treatment is 90℃-150℃ or 100℃-150℃.

[0064] In any embodiment, the heating treatment time is 3h–12h or 5h–12h.

[0065] Therefore, heat treatment is beneficial for removing residual solvents, reducing the content of impurities and byproducts in the positive electrode active layer, and improving the lithium-ion conductivity of the positive electrode active layer material, thereby improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell.

[0066] In any embodiment, the mass content of the sulfide solid electrolyte in the solution is 10%-70% or 30%-70%.

[0067] In any embodiment, the soaking time is 2h–8h.

[0068] In any embodiment, the impregnation is performed at room temperature.

[0069] In any embodiment, during the wetting process, the volume ratio of the solution to the first positive electrode active layer or the volume ratio of the solution to the composite layer is 1:9-8:2 or 1:1-7:3.

[0070] In any embodiment, the composite is performed at 60°C-100°C.

[0071] In any implementation, the compounding time is 2 min–10 min.

[0072] In any embodiment, the first positive electrode active layer is prepared by a dry process.

[0073] In any embodiment, the positive electrode is the positive electrode of the first or second aspect of this application.

[0074] The fourth aspect of this application provides a battery device, including a battery cell according to the first aspect of this application, a positive electrode according to the second aspect of this application, or a positive electrode prepared by the method of the third aspect of this application.

[0075] The fifth aspect of this application provides an electrical device, including a battery cell of the first aspect of this application or a battery device of the fourth aspect of this application. Attached Figure Description

[0076] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0077] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0078] Figure 2 is an exploded view of a secondary battery according to an embodiment of this application shown in Figure 1.

[0079] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0080] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0081] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0082] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0083] The accompanying drawings are not drawn to scale.

[0084] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0085] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0086] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, secondary battery, battery module, battery pack, 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.

[0087] 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 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 "ab" 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.

[0088] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0089] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0090] 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.

[0091] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0092] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0093] [Rechargeable Battery]

[0094] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0095] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0096] One embodiment of this application provides a solid-state battery cell, including a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The first positive active layer includes a positive electrode material, and the second positive active layer includes a sulfide solid electrolyte.

[0097] The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

[0098] Currently, wet processes are mainly used to prepare positive electrode sheets. However, when using sulfide solid electrolytes to prepare composite positive electrode sheets, the solvent in the wet process may undergo side reactions with the sulfide, leading to deterioration of the electrode sheet performance. Furthermore, the large amount of solvent used in the wet process can easily reduce the coverage of the sulfide solid electrolyte on the surface of the positive electrode active material during evaporation, affecting the rapid transport of lithium ions. Dry processes can avoid these problems. The high-speed shear force in the dry process can increase the contact area between the additives and the positive electrode active material, which is beneficial for the rapid diffusion of active lithium ions and improves the utilization rate of the positive electrode active material at high current densities. In addition, compared with wet processes, dry processes are more suitable for preparing thicker positive electrode sheets, thereby increasing the energy density of the battery cell.

[0099] However, the dry process for preparing composite electrodes requires high-speed shearing and stirring. Under high-speed shearing and stirring, the positive electrode active material and the sulfide solid electrolyte are prone to violent reaction to generate by-products. These by-products hinder lithium-ion transport in the electrode, reducing the initial efficiency, specific capacity, and cycle performance of the battery cell.

[0100] The applicant unexpectedly discovered that this application effectively reduces the content of by-product impurities in the positive electrode active layer, and can form a second positive electrode active layer with high coverage and including sulfide solid electrolyte on at least one side of the first positive electrode active layer, thereby improving the lithium-ion transport rate between the positive electrode material and the sulfide solid electrolyte, improving the lithium-ion conductivity of the positive electrode active layer material, and thus improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0101] [Positive electrode plate]

[0102] One embodiment of this application provides a positive electrode sheet including a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The first positive active layer includes a positive electrode material, and the second positive active layer includes a sulfide solid electrolyte.

[0103] The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

[0104] Therefore, this application effectively reduces the content of by-product impurities in the positive electrode active layer, and can form a second positive electrode active layer with high coverage and including sulfide solid electrolyte on at least one side of the first positive electrode active layer, thereby improving the lithium-ion transport rate between the positive electrode material and the sulfide solid electrolyte, improving the lithium-ion conductivity of the positive electrode active layer material, and thus improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0105] In some embodiments, the total mass content of impurities in the positive electrode active layer is ≤1.4%, ≤1.29%, or ≤1%, for example ≤1.35%, ≤1.3%, ≤1.29%, ≤1.25%, ≤1.2%, ≤1.15%, ≤1.1%, ≤1.07%, ≤1%, ≤0.97%, ≤0.94%, ≤0.85%, ≤0.83%, or ≤0.8%. The range consisting of ≤0.78%, ≤0.74%, ≤0.7%, ≤0.65%, ≤0.63%, ≤0.6%, ≤0.55%, ≤0.5%, ≤0.45%, ≤0.4%, ≤0.35%, ≤0.3%, ≤0.25%, ≤0.2%, ≤0.15%, ≤0.1%, ≤0.05%, ≤0.01%, or any of the above values.

[0106] In some embodiments, the mass content of nickel oxide impurities in the positive electrode active layer is ≤1%, ≤0.4%, or ≤0.3%, for example, ≤1%, ≤0.95%, ≤0.9%, ≤0.85%, ≤0.8%, ≤0.75%, ≤0.7%, ≤0.65%, ≤0.6%, ≤0.55%, ≤0.5%, ≤0.44%, ≤0.4%, ≤0.36%, ≤0.3%, ≤0.28%, ≤0.23%, ≤0.2%, ≤0.15%, ≤0.14%, ≤0.13%, ≤0.11%, ≤0.1%, ≤0.05%, ≤0.01%, or any range of the above values.

[0107] In some embodiments, the mass content of lithium sulfide impurities in the positive electrode active layer is ≤0.7% or ≤0.31%, for example, ≤0.7%, ≤0.64%, ≤0.6%, ≤0.56%, ≤0.5%, ≤0.44%, ≤0.4%, ≤0.37%, ≤0.31%, ≤0.3%, ≤0.27%, ≤0.24%, ≤0.23%, ≤0.22%, ≤0.21%, ≤0.2%, ≤0.18%, ≤0.1%, ≤0.05%, ≤0.01%, or any range of the above values.

[0108] In some embodiments, the mass content of phosphorus sulfide impurities in the positive electrode active layer is ≤0.5% or ≤0.36%, for example, ≤0.5%, ≤0.46%, ≤0.4%, ≤0.35%, ≤0.36%, ≤0.31%, ≤0.3%, ≤0.29%, ≤0.28%, ≤0.27%, ≤0.26%, ≤0.23%, ≤0.2%, ≤0.16%, ≤0.11%, ≤0.1%, ≤0.08%, ≤0.05%, ≤0.03%, ≤0.01%, or any range of the above values.

[0109] In some embodiments, the mass content of lithium phosphate impurities in the positive electrode active layer is ≤0.45% or ≤0.35%, for example, ≤0.45%, ≤0.4%, ≤0.35%, ≤0.3%, ≤0.28%, ≤0.26%, ≤0.24%, ≤0.22%, ≤0.2%, ≤0.18%, ≤0.17%, ≤0.15%, ≤0.1%, ≤0.08%, ≤0.05%, ≤0.01%, or any range of the above values.

[0110] In some embodiments, the mass content of elemental sulfur impurities in the positive electrode active layer is ≤1% or ≤0.3%, for example, ≤1%, ≤0.9%, ≤0.86%, ≤0.8%, ≤0.75%, ≤0.7%, ≤0.64%, ≤0.6%, ≤0.56%, ≤0.5%, ≤0.47%, ≤0.4%, ≤0.34%, ≤0.3%, ≤0.27%, ≤0.25%, ≤0.2%, ≤0.18%, ≤0.15%, ≤0.12%, ≤0.1%, ≤0.05%, ≤0.01%, or any range of the above values.

[0111] In some embodiments, the mass content of iron sulfide impurities in the positive electrode active layer is ≤0.35%, for example, ≤0.35%, ≤0.31%, ≤0.3%, ≤0.25%, ≤0.21%, ≤0.2%, ≤0.15%, ≤0.1%, ≤0.08%, ≤0.05%, ≤0.01%, or any range of the above values.

[0112] In some embodiments, the mass content of lithium pyrophosphate impurities in the positive electrode active layer is ≤0.4% or ≤0.31%, for example, ≤0.4%, ≤0.35%, ≤0.31%, ≤0.3%, ≤0.25%, ≤0.23%, ≤0.2%, ≤0.15%, ≤0.12%, ≤0.1%, ≤0.08%, ≤0.06%, ≤0.01%, or any range of the above values.

[0113] In some embodiments, the mass content of cobalt sulfide impurities in the positive electrode active layer is ≤0.5%.

[0114] In some embodiments, the mass content of cobalt phosphorus sulfide impurities in the positive electrode active layer is ≤0.3%.

[0115] In some embodiments, the impurities in the positive electrode active layer include one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

[0116] In some embodiments, the cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0117] Therefore, when the cathode material includes lithium nickel cobalt manganese oxide, this application suppresses the side reactions between the lithium nickel cobalt manganese oxide material and the sulfide solid electrolyte, effectively reducing the content of by-product impurities such as nickel sulfide, cobalt sulfide, nickel oxide, cobalt oxide, lithium sulfide, lithium oxide, phosphorus sulfide, cobalt phosphorus sulfide, elemental sulfur and / or lithium phosphate in the cathode active layer, improving the lithium-ion conductivity of the cathode active layer material, and improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0118] When the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, this application suppresses the side reactions between lithium iron phosphate and / or lithium manganese iron phosphate and sulfide solid electrolyte, effectively reducing the content of by-product impurities such as lithium sulfide, phosphorus sulfide, elemental sulfur, iron sulfide, lithium phosphate and / or lithium pyrophosphate in the cathode active layer, improving the lithium-ion conductivity of the cathode active layer material, and improving the initial coulombic efficiency, specific capacity and cycle performance of the battery cell.

[0119] In some embodiments, when the cathode material includes lithium nickel cobalt manganese oxide, the impurities include one or more sulfides of nickel, cobalt, lithium, and phosphorus, one or more oxides of nickel, cobalt, lithium, and phosphorus, elemental sulfur, and at least one of lithium phosphate. The impurities may be selected from one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, and elemental sulfur, and more preferably from one or more of NiO, Li2S, P2S5, and lithium phosphate.

[0120] Therefore, when the cathode material includes lithium nickel cobalt manganese oxide, this application suppresses side reactions between the lithium nickel cobalt manganese oxide material and the sulfide solid electrolyte, reducing the types and / or contents of impurities in the cathode active layer.

[0121] In some embodiments, when the cathode material comprises lithium iron phosphate and / or lithium manganese iron phosphate, the impurities include at least one of iron sulfide, phosphorus sulfide, lithium sulfide, elemental sulfur, lithium phosphate, and lithium pyrophosphate, and may optionally include one or more of Li2S, P2S5, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2, and more preferably include one or more of P2S5, elemental sulfur, lithium pyrophosphate, and FeS2.

[0122] Therefore, when the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, this application suppresses the side reactions between the lithium iron phosphate and / or lithium manganese iron phosphate materials and the sulfide solid electrolyte, reducing the types and / or contents of impurities in the cathode active layer.

[0123] In this application, the impurities and their content in the positive electrode active layer are tested using conventional methods in the art; for example, the testing method may be: disassembling the battery cell, removing the positive electrode sheet, scraping off the positive electrode active layer powder from the positive electrode sheet; and using an X-ray diffractometer (XRD) to test the positive electrode active layer powder, using Cu Kα radiation. The cathode active layer was operated at 36 kV and 20 mA within the 2θ range of 10-80. Impurity compounds in the cathode active layer were qualitatively identified based on diffraction peaks and comparison with standard spectra. The cathode active layer powder was tested using an X-ray photoelectron spectroscopy (XPS, ULVAC-PHI, Inc., PHI 5000 VersaProbe III) with monochromatic Al Kα radiation to obtain peaks of elements with different valence states. Based on the qualitative results above, the impurity compounds corresponding to the peaks of elements with different valence states were determined. Then, the content of impurity compounds in the cathode active layer was calculated based on the peak area of ​​elements with different valence states.

[0124] In some embodiments, the thickness ratio of the first positive electrode active layer to the second positive electrode active layer is 100:1-5000:1 or 200:1-1500:1, for example, 100:1, 150:1, 375:2, 200:1, 260:1, 280:1, 300:1, 350:1, 400:1, 3000:7, 467:1, 500:1, 600:1, 700:1, 750:1, 800:1, 900:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1 or any range of the above values. Therefore, the second positive electrode active layer, which includes a sulfide solid electrolyte, is beneficial in two ways: firstly, it improves the conductivity of lithium ions in the positive electrode active layer, thereby improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell; secondly, it helps to reduce the impact of the increased thickness of the second positive electrode active layer in the positive electrode active layer on the energy density of the battery cell.

[0125] In some embodiments, the thickness of the second positive electrode active layer is 100nm–1μm or 100nm–700nm, for example, 100nm, 200nm, 250nm, 300nm, 350nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm or any combination thereof. Thus, including a second positive electrode active layer with a sulfide solid electrolyte, on the one hand, it is beneficial to improve the conductivity of lithium ions in the positive electrode active layer, thereby improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell; on the other hand, it is beneficial to reduce the impact of increasing the thickness of the second positive electrode active layer on the energy density of the battery cell.

[0126] In this application, the thicknesses of the first positive electrode active layer and the second positive electrode active layer can be tested using conventional methods in the art. For example, the battery cell can be disassembled, the positive electrode sheet can be removed and cleaned, and then an ion beam can be used to cut along the thickness direction of the positive electrode sheet. TEM can be used to test the thicknesses of the first and second positive electrode active layers based on the interfaces of each layer, and then the thickness ratio of the first positive electrode active layer to the second positive electrode active layer can be calculated.

[0127] In some embodiments, the lithium-ion conductivity of the material in the positive electrode active layer is ≥3.4×10⁻⁶. -4 S / cm, or 7.3×10 -4 S / cm – 3.5 × 10 -3 S / cm, for example 3.4×10 -4 S / cm, 3.5×10 -4 S / cm, 3.7×10 -4 S / cm, 4×10 - 4 S / cm, 5×10 -4 S / cm, 6×10 -4 S / cm, 7×10 -4 S / cm, 7.3×10 -4 S / cm, 7.8×10 -4 S / cm, 8×10 - 4 S / cm, 8.5×10 -4 S / cm, 9×10 -4 S / cm, 9.4×10 -4 S / cm, 1×10 -3 S / cm, 1.1×10 -3 S / cm, 1.14×10 - 3 S / cm, 1.21×10 -3 S / cm, 1.27×10 -3 S / cm, 1.44×10-3 S / cm, 1.47×10 -3 S / cm, 1.5×10 -3 S / cm, 1.83×10 -3 S / cm, 2×10 -3 S / cm, 2.26×10 -3 S / cm, 2.5×10 -3 S / cm, 3×10 -3 S / cm, 3.5×10 -3 S / cm or any of the above values. Therefore, improving the lithium-ion conductivity of the positive electrode active layer material is beneficial to improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell.

[0128] In this application, the material in the positive electrode active layer refers to the material included in the positive electrode active layer, which can be obtained, for example, by scraping or crushing.

[0129] In this application, the lithium-ion conductivity of the positive electrode active layer material can be tested using conventional methods in the art. For example, it can be tested by constructing an electron-blocking electrode; the specific method can be as follows: disassemble the battery cell, remove the positive electrode sheet, clean and dry it, and scrape off the positive electrode active layer material powder (e.g., 150 mg); take a cylinder with a certain inner diameter, and add lithium powder, sulfide solid electrolyte, positive electrode active layer powder, sulfide solid electrolyte, and lithium powder to the cylinder in sequence, and then compact it under a certain pressure to form an electrode; perform a DC polarization test on the electrode, apply different voltages to the two ends of the electrode, and test the corresponding current; according to Ohm's law R=U / I, obtain the lithium-ion impedance of the electrode, and then calculate the lithium-ion conductivity using σ=L / (R×S), which is the lithium-ion conductivity of the positive electrode active layer material (the lithium-ion impedance formed by lithium powder and sulfide solid electrolyte can be ignored), where σ is the lithium-ion conductivity, R is the lithium-ion impedance of the electrode, L is the thickness of the positive electrode active layer powder after compaction in the cylinder, and S is the area calculated based on the inner diameter of the cylinder.

[0130] Another embodiment of this application provides a method for preparing a positive electrode sheet, which is either method one or method two;

[0131] Method 1 includes the following steps:

[0132] The first positive electrode active layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain a pretreated first positive electrode active layer.

[0133] The pretreated first positive electrode active layer is composited onto at least one side of the positive electrode current collector to obtain a positive electrode sheet;

[0134] The second method includes the following steps:

[0135] The first positive electrode active layer is composited on at least one side of the positive electrode current collector to obtain a composite layer;

[0136] The composite layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain the positive electrode sheet;

[0137] The solvent in the solution containing the sulfide solid electrolyte includes one or more of ethanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and propanol.

[0138] The positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The second positive active layer includes a sulfide solid electrolyte.

[0139] Therefore, this application employs a specific solution including a sulfide solid electrolyte to wet the first positive electrode active layer, avoiding the side reactions that occur between the sulfide solid electrolyte and the positive electrode material under high-speed shearing and stirring during dry processing. Furthermore, the solvent in the specific solution is less likely to react with the sulfide solid electrolyte, reducing the content of impurity byproducts in the positive electrode active layer. This enables the formation of a second positive electrode active layer with high coverage including the sulfide solid electrolyte on at least one side of the first positive electrode active layer, improving the lithium-ion transport rate between the positive electrode material and the sulfide solid electrolyte, and increasing the lithium-ion conductivity of the positive electrode active layer material. Consequently, this improves the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell.

[0140] In some embodiments, in method one, a heat treatment is performed after drying to obtain a pretreated first positive electrode active layer; or,

[0141] In method two, the positive electrode sheet is obtained by heating after drying.

[0142] In some embodiments, the heat treatment temperature is 90°C-150°C or 100°C-150°C, for example, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or any range of the above values; and / or,

[0143] The heating treatment time is 3h–12h or 5h–12h, for example, 3h, 4h, 5h, 6h, 8h, 10h, 12h or any range of the above values.

[0144] Therefore, heat treatment is beneficial for removing residual solvents, reducing the content of impurities and byproducts in the positive electrode active layer, and improving the lithium-ion conductivity of the positive electrode active layer material, thereby improving the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell.

[0145] In some embodiments, the mass content of the sulfide solid electrolyte in the solution is 10%-70% or 30%-70%, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or any range of the above values.

[0146] In some embodiments, the soaking time is 2h-8h, for example, 2h, 3h, 4h, 5h, 6h, 8h or any range of the above values.

[0147] In some embodiments, the impregnation is performed at room temperature.

[0148] In this application, room temperature has the commonly used definition in the art; for example, room temperature refers to general temperature or room temperature, which is approximately in the range of 15℃-30℃, such as 25℃.

[0149] In some embodiments, the volume ratio of the solution to the first positive electrode active layer or the volume ratio of the solution to the composite layer is 1:9-8:2 or 1:1-7:3, for example, 1:9, 2:8, 3:7, 4:6, 1:1, 6:4, 7:3, 8:2 or any range of the above values.

[0150] In some embodiments, the drying temperature is -80°C to 150°C, for example -80°C, -70°C, -60°C, -50°C, -40°C, -20°C, -10°C, 0°C, 5°C, 10°C, 30°C, 50°C, 70°C, 80°C, 100°C, 120°C, 140°C, 150°C, or any combination of the above values.

[0151] In some embodiments, the drying is carried out at -20 to 0 Pa or at atmospheric pressure.

[0152] In some embodiments, the drying time is 5h-12h, for example 5h, 6h, 8h, 10h, 12h or any range of the above values.

[0153] Therefore, the aforementioned drying temperature and / or time can effectively suppress the side reactions between the sulfide solid electrolyte and the positive electrode active material, reduce the impurity content in the positive electrode active layer, improve the lithium-ion conductivity of the positive electrode active layer material, and effectively remove residual solvent.

[0154] In some implementations, the composite is performed at 60°C-100°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C or any combination of the above values.

[0155] In some embodiments, the composite time is 2 min to 10 min, for example, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or any combination of the above values.

[0156] In some embodiments, the first positive electrode active layer is prepared by a dry process.

[0157] In some embodiments, lithium nickel cobalt manganese oxide materials include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 One or more of the following.

[0158] In this application, the dry process for preparing the positive electrode active layer is a conventional process in the field; for example, it can specifically involve mixing and dispersing the positive electrode active material and additives at high speed, and then hot rolling to form the positive electrode active layer. The high-speed mixing and dispersion rate and the hot rolling conditions are parameters or conditions commonly used in dry processes in the field.

[0159] In some embodiments, the positive electrode is the positive electrode described above in this application.

[0160] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0161] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0162] As examples, cathode materials may also include composite materials of lithium iron phosphate and carbon, composite materials of lithium manganese iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt aluminum oxide (such as LiNi). 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the aforementioned substances. However, this application is not limited to these materials; other conventional materials that can be used as battery cathode materials may also be used. These cathode materials may be used alone or in combination of two or more.

[0163] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0164] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0165] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder 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.

[0166] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0168] [Negative electrode plate]

[0169] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0170] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. 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, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0171] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0172] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0173] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0174] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0175] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0176] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0177] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0178] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0179] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0180] [Electrolytes]

[0181] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be solid-state.

[0182] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0183] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0184] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0185] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0186] In some embodiments, the sulfide solid electrolyte includes Li6PS5Cl, Li2S, P2S5, and Li7P3S. 11 Li 10 GeP2S 12 One or more of them.

[0187] [Structure of the electrode assembly]

[0188] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0189] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0190] In some implementations, the electrode assembly is a stacked structure.

[0191] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0192] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0193] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0194] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0195] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0196] [shell]

[0197] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0198] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0199] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0200] [Electrode terminals]

[0201] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0202] [Pressure relief mechanism]

[0203] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0204] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0205] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0206] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0207] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0208] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0209] The emissions from battery cells mentioned in this application include, but are not limited to: electrolytes, dissolved or split positive and negative electrode plates, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0210] [Battery Device]

[0211] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0212] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0213] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0214] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0215] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0216] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0217] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0218] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0219] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0220] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0221] For example, Figure 1 shows a square-structured battery cell 5 as an example.

[0222] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, solid electrolyte, and negative electrode sheet may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0223] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0224] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0225] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0226] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0227] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0228] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0229] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0230] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0231] [Example]

[0232] 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.

[0233] Example 1

[0234] (1) Preparation of the positive electrode sheet:

[0235] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1O2, conductive agent vapor-grown carbon fiber (VGCF), and binder polytetrafluoroethylene (PTFE) are mixed at a mass ratio of 93.5:3.5:3 using a high-speed dispersion method. After uniform mixing, the powder is rolled into a film by a hot roller at a temperature of 80°C to obtain the first positive electrode active layer prepared by the dry process.

[0236] The sulfide solid electrolyte Li6PS5Cl was dissolved in ethanol at a mass ratio of 50:50 to obtain a solution. The first positive electrode active layer was immersed in the above solution at 25°C for 12 hours, with a solution volume to first positive electrode active layer volume ratio of 7:3. Then, it was freeze-dried at -70°C and -10Pa negative pressure for 12 hours, followed by heat treatment at 110°C for 12 hours to obtain a pretreated first positive electrode active layer.

[0237] A positive electrode sheet is obtained by combining a pretreated first positive electrode active layer with a positive electrode current collector aluminum foil coated with a primer at 80°C. The positive electrode sheet includes a positive electrode current collector, a first positive electrode active layer located on one side of the positive electrode current collector, and a second positive electrode active layer located on the side of the first positive electrode active layer away from the positive electrode current collector. The thickness of the first positive electrode active layer and the second positive electrode active layer is 300:1.

[0238] (2) Preparation of negative electrode sheet:

[0239] Nano-silicon, graphite, conductive agent vapor-grown carbon fiber (VGCF), and binder polyvinylidene fluoride (PVDF) were mixed uniformly in a mass ratio of 62:35:1:2. N-methylpyrrolidone (NMP) was then added to obtain a negative electrode slurry with a solid content of 30% by mass. The negative electrode slurry was continuously coated on both sides of a copper foil current collector, dried at 80°C, and rolled to obtain the negative electrode sheet.

[0240] (3) Preparation of solid electrolytes:

[0241] The sulfide solid electrolyte Li6PS5Cl and polytetrafluoroethylene (PTFE) were mixed evenly at a mass ratio of 98:2, heated on a heating table at 80°C, and rolled into a dry solid electrolyte.

[0242] (4) Battery cell:

[0243] The positive electrode, solid electrolyte, and negative electrode prepared above are stacked in sequence, hot-pressed, and then sealed with aluminum-plastic film under negative pressure to obtain a soft-pack all-solid-state battery cell.

[0244] Battery test:

[0245] (1) Test methods for the 0.1C discharge specific capacity and initial coulombic efficiency of a single battery cell:

[0246] At an ambient temperature of 25℃ and a pressure of 50MPa, the battery cell was charged to 4.3V at a constant current of 0.1C, allowed to stand for 10 minutes, and then discharged to 2.0V at a constant current of 0.1C. The initial charge capacity and the initial discharge capacity were recorded. The initial coulombic efficiency of the battery cell was obtained by dividing the initial discharge capacity by the initial charge capacity (unit: mAh / g).

[0247] (2) Test methods for the cycle performance of individual battery cells:

[0248] At an ambient temperature of 25℃ and a pressure of 50MPa, the battery cells were charged to 4.8V at a constant current of 0.1C, left to stand for 10 minutes, and then discharged to 2.0V at a constant current of 0.1C. This process was repeated for a total of 3 cycles.

[0249] Then, at an ambient temperature of 25°C and a pressure of 50 MPa, the battery cells were charged at a constant current of 0.33C to 4.8V, allowed to stand for 10 minutes, and then discharged at a constant current of 0.33C to 2.0V. This process was repeated for a total of 50 cycles. The cycle capacity retention rate was obtained by dividing the discharge capacity of the 50th cycle at 0.33C by the discharge capacity of the first cycle at 0.33C.

[0250] Examples 2-3 and Comparative Example 1

[0251] In Example 2-3 and Comparative Example 1, step (1) was performed by replacing the solvent in the Li6PS5Cl solution in Example 1 with equal masses of propanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and methanol. The remaining operations and steps (2) to (4) were the same as in Example 1.

[0252] Comparative Example 4

[0253] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, sulfide electrolyte Li6PS5Cl, conductive agent nanofiber carbon fiber VGCF, and binder polytetrafluoroethylene PTFE were mixed in a mass ratio of 70:26:2:2 and dispersed by stirring at 4000 rpm for 0.5 h. The dry-mixed powder was then rolled into a film using a hot roller at 80 °C to obtain the initial positive electrode active layer. This initial positive electrode active layer was then treated in a vacuum oven at 200 °C for 12 h. Finally, the positive electrode active layer was laminated with a positive electrode current collector aluminum foil coated with a primer at 80 °C to obtain the positive electrode sheet.

[0254] Table 1. Some parameters and test results of Examples 1-3 and Comparative Examples 1 and 4.

[0255] It can be seen from the above table:

[0256] Compared with Comparative Example 1, which uses methanol as the solvent for the sulfide solid electrolyte solution, Examples 1-3 of this application use ethanol, propanol, or 1,2-ethylenediamine-1,2-ethylenedithiol as the solvent for the sulfide solid electrolyte solution. The content of impurity byproducts in the positive electrode active layer is significantly reduced, the thickness of the second positive electrode active layer is significantly increased, and the lithium-ion conductivity of the positive electrode active layer material is significantly improved. The initial coulombic efficiency, specific capacity, and cycle performance of the battery cells are significantly improved.

[0257] Compared with Comparative Example 4, which uses a completely dry method to prepare the positive electrode sheet, the positive electrode sheet of this application has significantly reduced the content of impurity byproducts in the positive active layer, significantly improved the lithium-ion conductivity of the positive active layer material, and significantly improved the initial coulombic efficiency, specific capacity and cycle performance of its battery cell.

[0258] In Examples 1, 3, and 2 of this application, ethanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and propanol are used sequentially as solvents for the sulfide solid electrolyte solution. This causes the content of impurities and byproducts in the positive electrode active layer to increase sequentially, the thickness of the second positive electrode active layer to decrease sequentially, and the lithium-ion conductivity of the positive electrode active layer material to decrease sequentially. Consequently, the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell decrease sequentially.

[0259] Examples 4-5

[0260] In step (1) of Examples 4-5, the heating treatment at 110°C for 12 hours in Example 1 is adjusted to heating treatment at 130°C for 6 hours and heating treatment at 90°C for 3 hours respectively. The remaining operations and steps (2) to (4) are the same as in Example 1.

[0261] Table 2. Some parameters and test results of Examples 1 and 4-5

[0262] It can be seen from the above table:

[0263] Compared with Example 5, which uses a heating treatment temperature of 90°C and a time of 3 hours, the impurity byproduct content in the positive electrode active layer of Examples 1 and 4 of this application is significantly reduced, the lithium-ion conductivity of the positive electrode active layer material is significantly increased, and the initial coulombic efficiency, specific capacity, and cycle performance of the battery cells are significantly improved.

[0264] Example 6

[0265] The soaking time in step (1) of Example 1 was adjusted to 6 hours, and the remaining operations and steps (2) to (4) were the same as in Example 1.

[0266] Example 7

[0267] In step (1) of Example 7, the mass content of Li6PS5Cl in the solution is adjusted to 30%, and the volume ratio of the solution to the first positive electrode active layer is adjusted to 5:5. The remaining operations and steps (2) to (4) are the same as in Example 1.

[0268] Example 8

[0269] In step (1) of Example 7, the mass content of Li6PS5Cl in the solution is adjusted to 10%, and the volume ratio of the solution to the first positive electrode active layer is adjusted to 1:9. The remaining operations and steps (2) to (4) are the same as in Example 1.

[0270] Table 3. Some parameters and test results of Examples 1 and 6-8

[0271] It can be seen from the above table:

[0272] In Examples 1, 7, and 8, the concentration of the sulfide solid electrolyte solution decreases sequentially, the volume ratio of the solution to the first positive electrode active layer decreases sequentially, the thickness of the second positive electrode active layer decreases sequentially, the lithium-ion conductivity of the positive electrode active layer material decreases sequentially, and the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell decrease sequentially.

[0273] Example 9

[0274] The positive electrode active material in step (1) of Example 1 is replaced with an equal mass of lithium iron phosphate material, and the remaining operations and steps (2) to (4) are the same as in Example 1.

[0275] Examples 10-11 and Comparative Example 2

[0276] In step (1) of Examples 10-11 and Comparative Example 2, the solvent in the Li6PS5Cl solution of Example 9 was replaced with equal masses of propanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and methanol. The remaining operations and steps (2) to (4) were the same as in Example 9.

[0277] Table 4. Some parameters and test results of Examples 9-11 and Comparative Example 2.

[0278] It can be seen from the above table:

[0279] Compared with Comparative Example 2, which uses methanol as the solvent for the sulfide solid electrolyte solution, Examples 9-11 of this application use ethanol, propanol, or 1,2-ethylenediamine-1,2-ethylenedithiol as the solvent for the sulfide solid electrolyte solution. The content of impurity byproducts in the positive electrode active layer is significantly reduced, the thickness of the second positive electrode active layer is significantly increased, and the lithium-ion conductivity of the positive electrode active layer material is significantly improved. The initial coulombic efficiency, specific capacity, and cycle performance of the battery cell are significantly improved.

[0280] In Examples 9, 11, and 10 of this application, ethanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and propanol are used sequentially as solvents for the sulfide solid electrolyte solution. This causes the content of impurities and byproducts in the positive electrode active layer to increase sequentially, the thickness of the second positive electrode active layer to decrease sequentially, and the lithium-ion conductivity of the positive electrode active layer material to decrease sequentially. Consequently, the initial coulombic efficiency, specific capacity, and cycle performance of the battery cell decrease sequentially.

[0281] Example 12

[0282] The positive electrode active material in step (1) of Example 1 is replaced with an equal mass of lithium manganese iron phosphate material, and the remaining operations and steps (2) to (4) are the same as in Example 1.

[0283] Comparative Example 3

[0284] The solvent in the Li6PS5Cl solution in Example 12 was replaced with an equal mass of methanol, and the remaining operations and steps (2) to (4) were the same as in Example 12.

[0285] Table 5. Some parameters and test results of Example 12 and Comparative Example 3

[0286] It can be seen from the above table:

[0287] Compared with Comparative Example 3, which uses methanol as the solvent for the sulfide solid electrolyte solution, Example 12 of this application uses ethanol as the solvent for the sulfide solid electrolyte solution. The content of impurity byproducts in the positive electrode active layer is significantly reduced, the thickness of the second positive electrode active layer is significantly increased, the lithium-ion conductivity of the positive electrode active layer material is significantly improved, and the initial coulombic efficiency, specific capacity and cycle performance of the battery cell are significantly improved.

[0288] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A solid-state battery cell, comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active layer located on at least one side of the positive current collector, the positive active layer comprising a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on a side of the first positive active layer away from the positive current collector and / or close to the positive current collector, the first positive active layer comprising a positive electrode material, and the second positive active layer comprising a sulfide solid electrolyte; The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

2. The solid-state battery cell according to claim 1, wherein, The total mass content of impurities in the positive electrode active layer is ≤1.4%, ≤1.29%, or ≤1%.

3. The solid-state battery cell according to claim 1 or 2, wherein, The battery cell includes one or more of the following: The mass content of nickel oxide impurities in the positive electrode active layer is ≤1%, ≤0.4%, or ≤0.3%. The mass content of lithium sulfide impurities in the positive electrode active layer is ≤0.7% or ≤0.31%; The mass content of phosphorus sulfide impurities in the positive electrode active layer is ≤0.5% or ≤0.36%; The mass content of lithium phosphate impurities in the positive electrode active layer is ≤0.45% or ≤0.35%; The mass content of elemental sulfur impurities in the positive electrode active layer is ≤1% or ≤0.3%. The mass content of iron sulfide impurities in the positive electrode active layer is ≤0.35%; The mass content of lithium pyrophosphate impurities in the positive electrode active layer is ≤0.4% or ≤0.31%. The mass content of cobalt sulfide impurities in the positive electrode active layer is ≤0.5%; The mass content of cobalt phosphorus sulfide impurities in the positive electrode active layer is ≤0.3%; The impurities in the positive electrode active layer include one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2. The cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

4. The solid-state battery cell according to any one of claims 1 to 3, wherein, When the cathode material includes lithium nickel cobalt manganese oxide, the impurities include one or more sulfides of nickel, cobalt, lithium, and phosphorus, one or more oxides of nickel, cobalt, lithium, and phosphorus, elemental sulfur, and at least one of lithium phosphate, and may be selected as one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, and elemental sulfur.

5. The solid-state battery cell according to any one of claims 1 to 3, wherein, When the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, the impurities include at least one of iron sulfide, phosphorus sulfide, lithium sulfide, elemental sulfur, lithium phosphate, and lithium pyrophosphate, and may be selected as one or more of Li2S, P2S5, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

6. The solid-state battery cell according to any one of claims 1 to 5, wherein, The thickness ratio of the first positive electrode active layer to the second positive electrode active layer is 100:1-5000:1 or 200:1-1500:1; and / or, The thickness of the second positive electrode active layer is 100nm–1μm or 100nm–700nm.

7. The solid-state battery cell according to any one of claims 1 to 6, wherein, The lithium-ion conductivity of the material in the positive electrode active layer is ≥3.4×10⁻⁶. -4 S / cm, or 7.3×10 -4 S / cm – 3.5 × 10 -3 S / cm.

8. The solid-state battery cell according to any one of claims 1 to 7, wherein, The sulfide solid electrolyte includes Li6PS5Cl, Li2S, P2S5, and Li7P3S. 11 Li 10 GeP2S 12 One or more of them.

9. A positive electrode sheet, comprising a positive current collector and a positive active layer located on at least one side of the positive current collector, the positive active layer comprising a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on a side of the first positive active layer away from the positive current collector and / or close to the positive current collector, the first positive active layer comprising a positive electrode material, and the second positive active layer comprising a sulfide solid electrolyte; The total mass content of impurities in the positive electrode active layer is ≤1.5%; the impurities include one or more sulfides of nickel, cobalt, lithium, iron, and phosphorus, one or more oxides of nickel, cobalt, lithium, iron, and phosphorus, elemental sulfur, lithium phosphate, and at least one of lithium pyrophosphate.

10. The positive electrode sheet according to claim 9, wherein, The total mass content of impurities in the positive electrode active layer is ≤1.4%, ≤1.29%, or ≤1%.

11. The positive electrode sheet according to claim 9 or 10, comprising one or more of the following: The mass content of nickel oxide impurities in the positive electrode active layer is ≤1%, ≤0.4%, or ≤0.3%. The mass content of lithium sulfide impurities in the positive electrode active layer is ≤0.7% or ≤0.31%; The mass content of phosphorus sulfide impurities in the positive electrode active layer is ≤0.5% or ≤0.36%; The mass content of lithium phosphate impurities in the positive electrode active layer is ≤0.45% or ≤0.35%; The mass content of elemental sulfur impurities in the positive electrode active layer is ≤1% or ≤0.3%. The mass content of iron sulfide impurities in the positive electrode active layer is ≤0.35%; The mass content of lithium pyrophosphate impurities in the positive electrode active layer is ≤0.4% or ≤0.31%. The mass content of cobalt sulfide impurities in the positive electrode active layer is ≤0.5%; The mass content of cobalt phosphorus sulfide impurities in the positive electrode active layer is ≤0.3%; The impurities in the positive electrode active layer include one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2. The cathode material includes one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

12. The positive electrode according to any one of claims 9 to 11, wherein, When the cathode material includes lithium nickel cobalt manganese oxide, the impurities include one or more sulfides of nickel, cobalt, lithium, and phosphorus, one or more oxides of nickel, cobalt, lithium, and phosphorus, elemental sulfur, and at least one of lithium phosphate, and may be selected as one or more of NiO, NiS, Ni3S2, Li2S, P2S5, Co3S4, lithium phosphate, and elemental sulfur.

13. The positive electrode according to any one of claims 9 to 11, wherein, When the cathode material includes lithium iron phosphate and / or lithium manganese iron phosphate, the impurities include at least one of iron sulfide, phosphorus sulfide, lithium sulfide, elemental sulfur, lithium phosphate, and lithium pyrophosphate, and may be selected as one or more of Li2S, P2S5, lithium phosphate, elemental sulfur, lithium pyrophosphate, and FeS2.

14. The positive electrode according to any one of claims 9 to 13, wherein, The thickness ratio of the first positive electrode active layer to the second positive electrode active layer is 100:1-5000:1 or 200:1-1500:1; and / or, The thickness of the second positive electrode active layer is 100nm–1μm or 100nm–700nm.

15. The positive electrode according to any one of claims 9 to 14, wherein, The lithium-ion conductivity of the material in the positive electrode active layer is ≥3.4×10⁻⁶. -4 S / cm, or 7.3×10 -4 S / cm – 3.5 × 10 -3 S / cm.

16. The positive electrode according to any one of claims 9 to 15, wherein, The sulfide solid electrolyte includes Li6PS5Cl, Li2S, P2S5, and Li7P3S. 11 Li 10 GeP2S 12 One or more of them.

17. A method for preparing a positive electrode sheet, which is either method one or method two; Method 1 includes the following steps: The first positive electrode active layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain a pretreated first positive electrode active layer. The pretreated first positive electrode active layer is composited onto at least one side of the positive electrode current collector to obtain a positive electrode sheet; The second method includes the following steps: The first positive electrode active layer is composited on at least one side of the positive electrode current collector to obtain a composite layer; The composite layer is immersed in a solution containing a sulfide solid electrolyte, removed and dried to obtain a positive electrode sheet; in, The solvent in the solution containing the sulfide solid electrolyte includes one or more of ethanol, 1,2-ethylenediamine-1,2-ethylenedithiol, and propanol. The positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a first positive active layer located on at least one side of the positive current collector and a second positive active layer located on the side of the first positive active layer away from the positive current collector and / or close to the positive current collector. The second positive active layer includes a sulfide solid electrolyte.

18. The method according to claim 17, wherein, In method one, after drying, a heat treatment is performed to obtain the pretreated first positive electrode active layer; or, In method two, the positive electrode sheet is obtained by heating after drying.

19. The method according to claim 18, wherein, The heat treatment temperature is 90℃-150℃ or 100℃-150℃; and / or, The heating treatment time is 3h–12h or 5h–12h.

20. The method according to any one of claims 17 to 19, comprising one or more of the following: The mass content of the sulfide solid electrolyte in the solution is 10%-70% or 30%-70%; The soaking time is 2h–8h; The impregnation is carried out at room temperature; During the wetting process, the volume ratio of the solution to the first positive electrode active layer or the volume ratio of the solution to the composite layer is 1:9-8:2 or 1:1-7:

3. The composite process is carried out at 60℃-100℃; The compounding time is 2 min-10 min; The first positive electrode active layer is prepared by a dry process; The positive electrode is the positive electrode as described in any one of claims 1 to 16.

21. A battery device comprising a battery cell according to any one of claims 1 to 8, a positive electrode according to any one of claims 9 to 16, or a positive electrode prepared by the method according to any one of claims 17 to 20.

22. An electrical device comprising a battery cell as described in any one of claims 1 to 8 or a battery device as described in claim 21.

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