Composite active material and preparation method therefor, solid-state battery cell, battery device, and electric device

Abstract

The present application relates to a composite active material and a preparation method therefor, a solid-state battery cell, a battery device, and an electric device. The solid-state battery cell comprises a current collector and a film layer arranged on at least one side surface of the current collector, wherein the film layer comprises a composite active material and a sulfide solid electrolyte. The composite active material comprises an inner core, at least one first coating layer and a second coating layer, wherein the at least one first coating layer is coated on at least part of the surface of the inner core, and the second coating layer is coated on at least part of the surface of the outermost first coating layer. The second coating layer comprises a selenium-containing compound, and the chemical formula of the selenium-containing compound is SeaMb, wherein M comprises at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co, and Mn, 0<a≤5, and 0<b≤20. The embodiments of the present application can improve the cycle stability and initial coulombic efficiency of the solid-state battery cell.

Description

Composite active materials and their preparation methods, solid-state battery cells, battery devices and electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411407379.8, filed on October 10, 2024, entitled “Composite active materials and preparation methods thereof, solid-state battery cells, battery devices and power devices”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, and in particular to a composite active material and its preparation method, a solid-state battery cell, a battery device, and an electrical device. Background Technology

[0004] In solid-state battery cells, the components are in solid-solid contact, and the gaps between these components hinder interfacial charge transport. Therefore, improving the cycle stability and initial coulombic efficiency of solid-state batteries is a pressing issue that needs to be addressed. Summary of the Invention

[0005] This application provides a composite active material and its preparation method, a solid-state battery cell, a battery device, and an electrical device, which can improve the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0006] In a first aspect, this application provides a solid-state battery cell, including a current collector and a film layer disposed on at least one side surface of the current collector. The film layer includes a composite active material and a sulfide solid electrolyte. The composite active material includes a core, at least one first coating layer, and a second coating layer. The first coating layer covers at least a portion of the surface of the core, and the second coating layer covers at least a portion of the surface of the outermost first coating layer. The second coating layer includes a selenium-containing compound with the chemical formula Se. a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

[0007] The composite active material of this application embodiment includes a core, a first coating layer disposed on at least a portion of the surface of the core, and a second coating layer disposed on at least a portion of the surface of the outermost first coating layer. By providing a selenium-containing compound in the second coating layer of the composite active material, the good compatibility between the selenium-containing compound and the sulfide solid electrolyte is utilized to reduce direct contact between the core and the sulfide solid electrolyte, thereby reducing the decomposition of the sulfide solid electrolyte and improving the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0008] In some embodiments, the selenium-containing compound includes one or more of sulfur selenium compounds, molybdenum selenium compounds, and antimony selenium compounds.

[0009] The aforementioned selenium-containing compounds exhibit good compatibility with sulfide solid electrolytes and do not react with them. Coating at least a portion of the surface of the outermost first coating layer reduces direct contact between the positive electrode active material and the sulfide solid electrolyte, minimizing its decomposition and thus further improving the cycle stability and initial coulombic efficiency of the solid-state battery cell. The selenium-containing compounds possess certain electronic and ionic conductivity; using them as a second coating layer allows for good charge exchange between the positive electrode active material and other components in the positive electrode film, thereby reducing the impact of the first and second coating layers on the solid-state battery cell capacity. Furthermore, the aforementioned selenium-containing compounds are relatively soft and have good thermal stability, which can buffer the volume expansion of the positive electrode active material during cycling, improving the cycle stability of the solid-state battery cell at both room temperature and high temperature.

[0010] In some embodiments, the sulfur-selenium compound includes SeS2, Se5S, SeS, Se5S2, Se3S2, Se3S5, SeS7, and SeS. 20 One or more of them.

[0011] In some embodiments, the selenium-containing compound content is 0.5%-5% by mass, optionally 0.5%-2%, based on 100% of the total mass of the composite active material. By adjusting the mass content of the selenium-containing compound, the thickness of the coating layer can be adjusted, thereby further improving the conductivity of the composite active material and further improving the cycle stability and first coulombic efficiency of the solid-state battery cell.

[0012] In some embodiments, the thickness of the second coating layer is 1-100 nm.

[0013] In some embodiments, the thickness of the second coating layer is 5-20 nm.

[0014] The thickness of the second coating layer, within the aforementioned range, can improve the ionic and electronic conductivity of the coating layer, reduce the impedance of the solid-state battery cell, and further enhance the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0015] In some embodiments, the specific surface area of ​​the composite active material is 1.3-3.5 m². 2 / g.

[0016] In some embodiments, the volumetric particle size distribution Dv50 of the composite active material is 2-8 μm.

[0017] The specific surface area and / or volumetric particle size distribution of composite active materials within the above range can enhance the charge migration dynamics of the positive electrode film, thereby improving the capacity performance of solid-state battery cells.

[0018] In some embodiments, the electronic conductivity of the composite active material is 8-18 mS / cm, and the ionic conductivity of the composite active material is 0.1-1 mS / cm.

[0019] In some embodiments, the compaction density of the composite active material is 1-3 g / cm³. 3 .

[0020] In some embodiments, the electronic conductivity of the first coating layer is 0.5-10 mS / cm, and the ionic conductivity of the first coating layer is 0.001-0.01 mS / cm.

[0021] In some embodiments, the electronic conductivity of the second coating layer is 0.1-1 mS / cm, and the ionic conductivity of the second coating layer is 0.01-0.1 mS / cm.

[0022] In some embodiments, the first coating layer includes one or more of P, B, W, Al, Nb, Zr, Mg, Ca, Li, C, Cl, Br, In, Y, Ta, La, and Fe.

[0023] Secondly, this application provides a method for preparing a composite active material, comprising:

[0024] Provide a core material including a first coating layer;

[0025] The core material coated by the first coating layer and the coating material of the second coating layer are mixed and then ball-milled to obtain a composite active material.

[0026] The second coating layer includes a selenium-containing compound with the chemical formula Se. a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

[0027] Ball milling allows the coating material of the second coating layer to be uniformly coated onto the surface of the core, improving the coating uniformity of the second coating layer. Furthermore, ball milling directly coats the selenium compound onto the surface of the core coated by the first coating layer, increasing the purity of the selenium-containing compound in the coating layer and further enhancing the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0028] In some embodiments, the selenium-containing compound content is 0.1%-10% based on the total mass of the composite active material (100%).

[0029] In some embodiments, the selenium-containing compound content is 0.5%-2% based on the total mass of the composite active material (100%).

[0030] This allows for adjustment of the coating thickness, further enhancing the conductivity of the composite active material and improving the cycle stability and initial coulombic efficiency of solid-state battery cells.

[0031] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling speed is 300-1000 rpm.

[0032] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling time is 5-20 hours.

[0033] Setting the ball milling speed and / or time within the above range can make the second coating layer uniformly coat the surface of the first coating layer.

[0034] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling process is carried out in an intermittent ball milling manner.

[0035] Ball milling generates heat. Intermittent ball milling can dissipate this heat and reduce side reactions caused by excessively high temperatures during the ball milling process.

[0036] Thirdly, this application provides a composite active material, which is prepared by the preparation method of the second aspect of this application.

[0037] Fourthly, this application provides a battery device including a plurality of solid-state battery cells according to the first aspect of this application.

[0038] Fifthly, this application provides an electrical device, including the battery device of the fourth aspect of this application. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described 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.

[0040] Figure 1 is a schematic diagram of one embodiment of the solid-state battery cell of this application.

[0041] Figure 2 is a schematic diagram of one embodiment of an electrical device that uses the battery device of this application as a power source.

[0042] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0043] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the composite active material and its preparation method, solid-state battery cell, battery device, 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.

[0044] 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.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of this application.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the content of this application.

[0047] 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 method may also include step (c), indicating 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.

[0048] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0049] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0050] The solid-state battery cells mentioned in the embodiments of this application can independently perform charging and discharging functions. Solid-state battery cells can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited in this respect. Figure 1 shows a cuboid solid-state battery cell 5 as an example.

[0051] The battery apparatus mentioned in the embodiments of this application may include one or more solid-state battery cell assemblies for providing voltage and capacity. A solid-state battery cell assembly may include multiple solid-state battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0052] In some embodiments, a solid-state battery cell assembly is typically formed by arranging multiple solid-state battery cells. As an example, a solid-state battery cell assembly can be a battery module, which is formed by arranging and fixing multiple solid-state battery cells together to form a single module. As an example, a battery module can be formed by bundling multiple solid-state battery cells together with cable ties.

[0053] In some embodiments, the battery device may be a battery pack, which may include a housing and one or more solid-state battery cell assemblies housed within the housing. As an example, the solid-state battery cell assembly may be a battery module, which can be housed within the housing by securing the battery module to the housing. Alternatively, as an example, the solid-state battery cell assembly may be housed within the housing by directly securing multiple solid-state battery cells to the housing.

[0054] 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 solid-state battery cell assembly. 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.

[0055] 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.

[0056] 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.

[0057] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use solid-state battery cells and battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, 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. Solid-state battery cells and battery devices are used to store or provide electrical energy.

[0058] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0059] In a solid-state battery cell, the components are in solid-solid contact, and there are gaps between the components. During cycling, the volume change of the active material will further lead to the expansion of the interfacial gaps, which will increase the impedance of the solid-state battery cell, limit the capacity and reduce the cycle stability.

[0060] In addition, side reactions exist between the active material and the sulfide solid electrolyte, which can lead to the breakage of the active material and the oxidative decomposition of the sulfide solid electrolyte. These conditions can also deteriorate the initial coulombic efficiency and cycle stability of solid-state battery cells.

[0061] In view of this, this application provides a solid-state battery cell, including a current collector and a film layer disposed on at least one side surface of the current collector, the film layer including a composite active material and a sulfide solid electrolyte;

[0062] The composite active material includes a core, at least one first coating layer and a second coating layer, wherein at least one first coating layer covers at least a portion of the surface of the core, and the second coating layer covers at least a portion of the surface of the outermost first coating layer;

[0063] The second coating layer includes a selenium-containing compound with the chemical formula Se.a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

[0064] In the case where the current collector and the membrane layer are used as the positive electrode, the current collector can be a positive electrode current collector, the membrane layer can be a positive electrode membrane layer, the composite active material can be a composite positive electrode active material, and the core can be a positive electrode active material.

[0065] Selenium-containing compounds may undergo side reactions with the positive electrode active material under high voltage. Coating at least a portion of the surface of the positive electrode active material with a first coating layer can reduce the contact between the selenium-containing compounds and the positive electrode active material, thereby improving the stability of the positive electrode active material. Here, "high voltage" usually refers to a measurement or operating voltage greater than or equal to 3V.

[0066] In the embodiments of this application, the total thickness of the first and second coating layers is relatively thick, which may affect charge transfer. The selenium-containing compound is relatively soft and has good contact with the sulfide solid electrolyte. In addition, it has good ion conduction and electron conduction capabilities, which can promote charge transfer between the positive electrode active material and the outside world, thereby reducing the negative effect of multilayer coating on charge transfer.

[0067] The composite active material of this application embodiment includes a core, a first coating layer disposed on at least a portion of the surface of the core, and a second coating layer disposed on at least a portion of the surface of the outermost first coating layer. By providing a selenium-containing compound in the second coating layer of the composite active material, the good compatibility between the selenium-containing compound and the sulfide solid electrolyte is utilized to reduce direct contact between the core and the sulfide solid electrolyte, thereby reducing the decomposition of the sulfide solid electrolyte and improving the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0068] In some embodiments, the first coating layer can enhance the electron transport capability of the composite active material.

[0069] In some embodiments, the first covering layer can be one layer or two or more layers. It is understood that the technical effects of the embodiments of this application can be achieved when the first covering layer is one layer.

[0070] In some embodiments, the surface of the second covering layer may also include an optional third covering layer.

[0071] In some embodiments, the selenium-containing compound may include one or more of sulfur selenium compounds, molybdenum selenium compounds, and antimony selenium compounds.

[0072] The aforementioned selenium-containing compounds exhibit good compatibility with sulfide solid electrolytes and do not react with them. Coating at least a portion of the surface of the outermost first coating layer reduces direct contact between the positive electrode active material and the sulfide solid electrolyte, minimizing its decomposition and thus further improving the cycle stability and initial coulombic efficiency of the solid-state battery cell. The selenium-containing compounds possess certain electronic and ionic conductivity; using them as a second coating layer allows for good charge exchange between the positive electrode active material and other components in the positive electrode film, thereby reducing the impact of the first and second coating layers on the solid-state battery cell capacity. Furthermore, the aforementioned selenium-containing compounds are relatively soft and have good thermal stability, which can buffer the volume expansion of the positive electrode active material during cycling, improving the cycle stability of the solid-state battery cell at both room temperature and high temperatures. Here, "room temperature" typically refers to 20-30℃, and "high temperature" typically refers to 45-80℃.

[0073] In some embodiments, the sulfur-selenium compound may include SeS2, Se5S, SeS, Se5S2, Se3S2, Se3S5, SeS7, and SeS. 20 One or more of them.

[0074] In some embodiments, the sulfur-selenium compound may include SeS2.

[0075] SeS2 combines the high specific capacity of sulfur (S) with the high conductivity of se, thereby further enhancing the electronic and ionic conductivity of the second coating layer. This facilitates good charge exchange between the positive electrode active material and other components in the positive electrode film, reducing the impact of the second coating layer on the capacity of the solid-state battery cell. SeS2 is relatively soft and has good thermal stability, which can buffer the volume expansion of the positive electrode active material during cycling, improving the cycle stability of the solid-state battery cell at both room temperature and high temperature. Furthermore, SeS2 has good compatibility with sulfide solid electrolytes; using SeS2 as the second coating layer for the positive electrode active material can also reduce the decomposition of the sulfide solid electrolyte.

[0076] In some embodiments, the volumetric particle size distribution Dv50 of the sulfur-selenium compound can be 5-200 nm, optionally 5-50 nm. This can further improve the uniformity of coating.

[0077] In some embodiments, the selenium-containing compound content can be 0.5%-5% by mass, preferably 0.5%-2%, based on the total mass of the composite active material as 100%. For example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, or any range of the above values.

[0078] The thickness of the coating layer can be adjusted by regulating the mass content of selenium-containing compounds, thereby further improving the electrical conductivity of the composite active material.

[0079] In some embodiments, the first coating layer may be located on 90% to 100% of the surface of the positive electrode active material. Optionally, the first coating layer is located on 100% of the surface of the positive electrode active material.

[0080] In some embodiments, the second overlay may be located on 90% to 100% of the surface of the outermost first overlay. Optionally, the second overlay may be located on 100% of the surface of the outermost first overlay.

[0081] In some embodiments, the selenium-containing compound in the second coating layer is 100% by mass. This allows for the complete coating of the outermost first coating layer, i.e., the positive electrode active material, by the selenium-containing compound, reducing direct contact between the positive electrode active material and the sulfide solid electrolyte, reducing the decomposition of the sulfide solid electrolyte, and thereby further improving the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0082] In some embodiments, the thickness of the second coating layer can be 1-100 nm, for example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any range of the above values.

[0083] In some embodiments, the thickness of the second coating layer can be 5-20 nm.

[0084] The thickness of the second coating layer, within the aforementioned range, can improve the ionic and electronic conductivity of the coating layer, reduce the impedance of the solid-state battery cell, and further enhance the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0085] In some embodiments, the specific surface area of ​​the composite active material can be 1.3-3.5 m². 2 / g.

[0086] Specific surface area can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0087] In some embodiments, the volumetric particle size distribution Dv50 of the composite active material can be 2-8 μm.

[0088] The volumetric particle size distribution (Dv50) of composite active materials can be determined using a laser particle size analyzer (such as the Malvern Mastersizer 3000) in accordance with GB / T 19077-2016. The physical definition of Dv50 is the particle size corresponding to a cumulative volumetric distribution percentage of 50% for the material.

[0089] The specific surface area and / or volumetric particle size distribution of composite active materials within the above range can enhance the charge migration dynamics of the positive electrode film and improve the capacity performance of solid-state battery cells.

[0090] The composite active material in this application embodiment has high electronic conductivity and ionic conductivity.

[0091] In some embodiments, the electronic conductivity of the composite active material can be 8-18 mS / cm, and the ionic conductivity of the composite active material can be 0.1-1 mS / cm.

[0092] In some embodiments, the compaction density of the composite active material can be 1-3 g / cm³. 3 .

[0093] The compaction density can be determined according to standard GB / T24533-2009 using an electronic pressure testing machine (e.g., UTM7305). An exemplary test method is as follows: Weigh 1g of the above-mentioned composite active material and add it to a container with a base area of ​​1.327cm². 2 In the mold, pressure is applied to 40kN and held for 30s, then pressure is released and held for 10s. The compaction density of the composite active material under 40kN pressure is then recorded and calculated.

[0094] When the compaction density of the composite active material is within the above range, the stacking performance of the composite active material can be improved, thereby further improving the cycle stability and first coulombic efficiency of the solid-state battery cell.

[0095] In some embodiments, the electronic conductivity of the first coating layer can be 0.5-10 mS / cm, and the ionic conductivity of the first coating layer can be 0.001-0.01 mS / cm.

[0096] In some embodiments, the electronic conductivity of the second coating layer can be 0.1-1 mS / cm, and the ionic conductivity of the second coating layer can be 0.01-0.1 mS / cm.

[0097] In some embodiments, the thickness of the first coating layer includes, but is not limited to, 5-100 nm.

[0098] In some embodiments, based on the total mass of the composite active material being 100%, the mass content of the coating material in the first coating layer includes, but is not limited to, 0.5-5%.

[0099] In some embodiments, the first coating layer may include one or more of P, B, W, Al, Nb, Zr, Mg, Ca, Li, C, Cl, Br, In, Y, Ta, La, and Fe.

[0100] In some embodiments, the first coating layer may include one or more of lithium niobate (LiNbO2), lithium titanate, lithium nickelate, lithium manganese oxide, lithium phosphate, lithium borate, lithium zirconate, and lithium tungstate.

[0101] In some embodiments, the positive electrode active material may include one or more of lithium cobalt oxide and its modified materials, lithium iron phosphate and its modified materials, lithium manganese iron phosphate and its modified materials, lithium nickel cobalt manganese oxide and its modified materials, lithium nickel cobalt aluminum oxide and its modified materials, lithium nickel oxide and its modified materials, lithium manganese oxide and its modified materials, lithium niobate and its modified materials, lithium titanate, sulfur, selenium, and tellurium. The modified materials for the above-mentioned positive electrode active materials may be those obtained by doping and / or surface coating modification of the positive electrode active material.

[0102] As an example, positive electrode active materials may include, but are not limited to, LiCoO2 and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, Li4Ti5O 12 and one or more of their respective modified materials.

[0103] During the charging and discharging process, solid-state battery cells undergo Li insertion / extraction and consumption, resulting in varying Li molar content at different discharge states. In the examples of positive electrode active materials in this application, the Li molar content refers to the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to a solid-state battery cell, the Li molar content changes after charge-discharge cycles. Similarly, in the examples of positive electrode active materials in this application, the O molar content is only a theoretical value. Lattice oxygen release causes changes in the O molar content, leading to fluctuations in the actual O molar content.

[0104] In some embodiments, the sulfide solid electrolyte contains sulfur atoms in its electrolyte composition, but is not limited to a specific composition, and may include one or more of crystalline solid electrolytes, amorphous solid electrolytes (glassy solid electrolytes), or glass-ceramic solid electrolytes.

[0105] In some embodiments, the sulfide solid electrolyte may include sulfide-germanium sulfide, binary sulfide, and ternary sulfide.

[0106] In some embodiments, sulfide of the silver-germanium type may include sulfides with the chemical formula Li 6±s P 1-j A j S 5±s- t B t X 1±s The material has the following properties: 0≤j<1, 0≤t<1, 0≤s<1. A includes one or more elements selected from Ge, Si, Sn, and Sb; B includes one or more elements selected from O, Se, and Te; and X includes one or more elements selected from Cl, Br, I, and F. Australite-type sulfides can include Li6PS5Cl.

[0107] In some embodiments, the binary sulfide may include one or more of Li2S-GeS2, Li2S-P2S5, Li2S-SiS2, and Li2S-B2S3.

[0108] In some embodiments, the ternary sulfide may include one or more of Li2S-SiS2-P2S5, Li2S-GeS2-P2S5, Li2S-SnS2-P2S5, and Li2S-AlS2-P2S5.

[0109] In some embodiments, the solid electrolyte may further include one or both of halide solid electrolytes and oxide solid electrolytes.

[0110] In some embodiments, the positive electrode film may further include a positive electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and vapor-grown carbon fibers (VGCF). For example, the positive electrode conductive agent may be vapor-grown carbon fibers.

[0111] The positive electrode may or may not include a positive electrode binder, depending on the manufacturing process of the positive electrode and the solid-state battery cell.

[0112] In some embodiments, the positive electrode sheet includes a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0113] In some embodiments, the current density of the positive electrode can be 1-5 mAh / cm². 2 .

[0114] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, the metal material in the metal material layer may be one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may be one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0115] [Preparation Method of Composite Active Materials]

[0116] This application provides a method for preparing a composite active material, comprising:

[0117] Provide a core material including a first coating layer;

[0118] The core material coated by the first coating layer and the coating material of the second coating layer are mixed and then ball-milled to obtain a composite active material.

[0119] The second coating layer includes a selenium-containing compound with the chemical formula Se. a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

[0120] Ball milling allows the coating material of the second coating layer to be uniformly coated onto the surface of the core, improving the coating uniformity of the second coating layer. Furthermore, ball milling directly coats the selenium compound onto the surface of the core coated by the first coating layer, thereby increasing the purity of the selenium-containing compound in the coating layer and further improving the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0121] The preparation methods for the core material coated by the first coating layer include, but are not limited to, ball milling and liquid phase coating.

[0122] In some embodiments, the mass content of the selenium-containing compound can be 0.1%-10% based on the total mass of the composite active material (100%), for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of the above values.

[0123] In some embodiments, the selenium-containing compound content can be 0.5%-2% based on the total mass of the composite active material (100%). This allows for adjustment of the coating thickness, further improving the conductivity of the composite active material, thereby further enhancing the cycle stability and initial coulombic efficiency of the solid-state battery cell.

[0124] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling speed can be 300-1000 rpm, for example, it can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, or any range of the above values.

[0125] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling time can be 5-20 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 15 hours, 20 hours, or any range of the above values.

[0126] Setting the ball milling speed and / or time within the above range can make the second coating layer uniformly coat the surface of the first coating layer.

[0127] In some embodiments, in the step of mixing the core material covered by the first coating layer and the coating material of the second coating layer and then performing ball milling, the ball milling process can be carried out in an intermittent ball milling manner.

[0128] Ball milling generates heat. Intermittent ball milling can dissipate this heat and reduce side reactions caused by excessively high temperatures during the ball milling process.

[0129] [Composite Active Materials]

[0130] The composite active material was prepared using the method described in this application.

[0131] [Negative electrode plate and electrolyte plate]

[0132] In some embodiments, the solid-state battery cell further includes a negative electrode and an electrolyte sheet. The electrolyte sheet is located between the positive and negative electrode. The negative electrode includes a negative electrode active material, which may include one or more of the following: graphite, graphene, carbon nanotubes, mesophase microcarbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, metal oxides, lithium metal, lithium alloys, and lithium composite materials.

[0133] Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon carbides, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin compounds, and tin alloys. Metal oxides may include one or more of TiO2, MoO2, In2O3, Al2O3, Cu2O, VO2, Ga2O3, Sb2O5, and Bi2O5. Other elements in lithium alloys may include one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe, for example, Li-In alloys, Li-Mg alloys, Li-Al alloys, Li-Zn alloys, and Li-Fe alloys.

[0134] The negative electrode can be a metal sheet, such as a lithium sheet, which can be prepared by dry method or wet method.

[0135] In some embodiments, the negative electrode may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0136] In some embodiments, the negative electrode sheet may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0137] The negative electrode sheet may or may not include a negative electrode current collector. In some embodiments, the negative electrode sheet includes a negative electrode current collector, with the negative electrode active material located on at least one surface of the negative electrode current collector. The negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, foamed copper, foamed nickel, and foamed aluminum. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include, but is not limited to, one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0138] The electrolyte sheet includes a solid electrolyte. The solid electrolyte includes one or more of sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes. Optionally, the solid electrolyte includes a sulfide solid electrolyte. In this application, the material of the solid electrolyte can refer to the selection of sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes in the above-described positive electrode sheet, and will not be elaborated further here.

[0139] Understandably, the second coating layer can reduce the direct contact between the core and the sulfide solid electrolyte in the positive electrode, as well as the direct contact between the core and the sulfide solid electrolyte in the electrolyte sheet.

[0140] Solid-state battery cells can be prepared using methods known in the art. For example, the assembly methods of solid-state battery cells include, but are not limited to, coin cells, molded cells, hard-case cells, and pouch cells.

[0141] Example

[0142] The following embodiments describe the contents of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0143] Example 1

[0144] Preparation of composite active materials

[0145] LiNbO2 (0.05g) and LiNi were weighed according to a mass ratio of 5:95. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) (0.95g) was mixed and then ball-milled at 500 rpm for 12 hours, with a 5-minute interval between every 10 minutes of operation, to obtain a positive electrode active material with lithium niobate coated on the surface.

[0146] SeS2 was weighed at a mass ratio of 0.5:99.5 and mixed with the positive electrode active material coated with lithium niobate. The mixture was then ball-milled at 500 rpm for 12 hours, with a 5-minute pause between every 10 minutes of milling. The resulting composite active material had a second coating layer thickness of 5 nm.

[0147] Preparation of positive electrode sheet

[0148] The composite active material, sulfide solid electrolyte Li6PS5Cl, and vapor-grown carbon fiber (VGCF) positive electrode conductive agent prepared above were uniformly mixed at a mass ratio of 70:27:3 for 10 min to obtain composite positive electrode powder. Polytetrafluoroethylene (PTFE) positive electrode binder, equivalent to 1% of the total mass of the first three components, was added, and then rolled into a positive electrode film. Finally, the positive electrode film was hot-rolled and laminated with aluminum foil positive electrode current collector to obtain the positive electrode sheet. The thickness of the positive electrode sheet was 100 μm.

[0149] Preparation of solid-state battery cells

[0150] 100 mg of sulfide solid electrolyte Li6PS5Cl was weighed and added to a battery mold. The electrolyte sheet was obtained by pressing. Then, the positive electrode sheet was placed on one side of the electrolyte sheet, and InLi alloy was added to the other side as the negative electrode sheet. The molar ratio of Li to In was 1:3. The solid battery cell was pressed into a solid battery cell under a pressure of 10 MPa and then sealed in a mold battery fixture with an external pressure of 50 MPa.

[0151] Example 2

[0152] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0153] SeS2 was weighed at a mass ratio of 1:99 and mixed with the positive electrode active material coated with lithium niobate. The mixture was then ball-milled at 500 rpm for 12 hours, with a 5-minute pause between every 10 minutes of milling. The resulting composite active material had a second coating layer thickness of 10 nm.

[0154] Example 3

[0155] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0156] SeS2 was weighed and mixed with the positive electrode active material coated with lithium niobate at a mass ratio of 20:80, and then ball-milled at 500 rpm for 12 hours, with a 5-minute pause after every 10 minutes of operation. The resulting composite active material had a second coating layer thickness of 200 nm.

[0157] Example 4

[0158] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0159] MoSe2 was weighed and mixed with the positive electrode active material coated with lithium niobate at a mass ratio of 1:99, and then ball-milled at 500 rpm for 12 hours, with a 5-minute pause after every 10 minutes of operation. The thickness of the second coating layer of the resulting composite active material was 8 nm.

[0160] Example 5

[0161] Except for the following differences, the preparation method of the solid-state battery cell is the same as that in Example 1.

[0162] SeS2 was weighed and mixed with lithium niobate-coated cathode active material at a mass ratio of 10:90, and then ball-milled at 500 rpm for 12 hours, with a 5-minute pause after every 10 minutes of operation. The resulting composite active material had a second coating layer thickness of 100 nm.

[0163] Comparative Example 1

[0164] Except for the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 Apart from the O2 (NCM811) coating, the preparation method of the solid-state battery cell is the same as in Example 1.

[0165] Comparative Example 2

[0166] Except for the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 Except for the first coating of O2 (NCM811) and the absence of a second coating, the preparation method of the solid-state battery cell is the same as in Example 1.

[0167] Performance testing

[0168] (1) Performance testing of solid-state battery cells, materials or electrodes

[0169] Charge-discharge tests were conducted on the Blue Battery testing platform at temperatures of 25℃ and 60℃, with a charge-discharge voltage range of 2.6V-4.3V (vs. Li). + / Li), the external pressure during the test was 50MPa.

[0170] After three charge-discharge cycles at 0.1C, a long-cycle test at 0.33C was conducted on a single solid-state battery cell. By collecting and processing the first charge-discharge data at 0.1C, the initial charge and discharge specific capacity and initial coulombic efficiency at 0.1C can be obtained. Initial coulombic efficiency (%) = (First discharge specific capacity / First charge specific capacity) × 100%.

[0171] Divide the discharge specific capacity of the 203rd cycle by the discharge specific capacity of the 4th cycle to obtain the capacity retention rate after 200 cycles at a 0.33C rate.

[0172] (2) Morphological analysis

[0173] SEM images of a uniform coating layer containing element Se observed on the surface of the positive electrode active material were obtained using a scanning electron microscope (Hitachi JSM 6700) and an energy dispersive spectroscopy (EDS) instrument attached to the SEM instrument.

[0174] The thickness and uniformity of the coating layer can be observed using high-resolution transmission electron microscopy (HRTEM).

[0175] The test results of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1.

[0176] Table 1

[0177] As can be seen from the test results in Table 1, the composite active material in this embodiment utilizes the good compatibility between selenium-containing compounds and sulfide solid electrolytes to reduce the direct contact between the core and the sulfide solid electrolytes and the decomposition of the sulfide solid electrolytes, thereby improving the cycle stability and first coulombic efficiency of the solid battery cell.

[0178] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A solid-state battery cell, comprising a current collector and a film layer disposed on at least one side surface of the current collector, the film layer comprising a composite active material and a sulfide solid electrolyte; The composite active material includes a core, at least one first coating layer and a second coating layer, wherein the at least one first coating layer covers at least a portion of the surface of the core, and the second coating layer covers at least a portion of the surface of the outermost first coating layer; The second coating layer comprises a selenium-containing compound with the chemical formula Se. a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

2. The solid-state battery cell according to claim 1, wherein, The selenium-containing compounds include one or more of sulfur selenium compounds, molybdenum selenium compounds, and antimony selenium compounds.

3. The solid-state battery cell according to claim 2, wherein, The sulfur-selenium compounds include SeS2, Se5S, SeS, Se5S2, Se3S2, Se3S5, SeS7, and SeS. 20 One or more of them.

4. The solid-state battery cell according to any one of claims 1-3, wherein, Based on the total mass of the composite active material as 100%, the mass content of the selenium-containing compound is 0.5%-5%, optionally 0.5%-2%.

5. The solid-state battery cell according to any one of claims 1-4, wherein, The thickness of the second coating layer is 1-100 nm.

6. The solid-state battery cell according to any one of claims 1-5, wherein, The thickness of the second coating layer is 5-20 nm.

7. The solid-state battery cell according to any one of claims 1-6, wherein, The composite active material satisfies one or more of the following conditions (1)-(6): (1) The specific surface area of ​​the composite active material is 1.3-3.5 m². 2 / g; (2) The volume particle size distribution Dv50 of the composite active material is 2-8 μm; (3) The electronic conductivity of the composite active material is 8-18 mS / cm, and the ionic conductivity of the composite active material is 0.1-1 mS / cm; (4) The compaction density of the composite active material is 1-3 g / cm³. 3 ; (5) The electronic conductivity of the first coating layer is 0.5-10 mS / cm, and the ionic conductivity of the first coating layer is 0.001-0.01 mS / cm; (6) The electronic conductivity of the second coating layer is 0.1-1 mS / cm, and the ionic conductivity of the second coating layer is 0.01-0.1 mS / cm.

8. The solid-state battery cell according to any one of claims 1-7, wherein, The first coating layer includes one or more of P, B, W, Al, Nb, Zr, Mg, Ca, Li, C, Cl, Br, In, Y, Ta, La and Fe.

9. A method for preparing a composite active material, comprising: Provide a core material including a first coating layer; The core material coated by the first coating layer and the coating material of the second coating layer are mixed and then ball-milled to obtain a composite active material. The second coating layer comprises a selenium-containing compound with the chemical formula Se. a M b M includes at least one of Li, Na, K, Mg, Ca, S, Mo, Cr, Zn, In, Ga, Co and Mn, where 0 < a ≤ 5 and 0 < b ≤ 20.

10. The preparation method according to claim 9, wherein, Based on the total mass of the composite active material being 100%, the mass content of the selenium-containing compound is 0.1%-10%.

11. The preparation method according to claim 9 or 10, wherein, Based on the total mass of the composite active material being 100%, the mass content of the selenium-containing compound is 0.5%-2%.

12. The preparation method according to any one of claims 9-11, wherein, In the step of ball milling the core material coated by the first coating layer and the coating material of the second coating layer, the ball milling process satisfies one or more of the following conditions (1)-(3): (1) The ball milling speed is 300-1000 rpm; (2) The ball milling treatment time is 5-20 hours; (3) The ball milling process is carried out by intermittent ball milling.

13. A composite active material, said composite active material being prepared by any one of the preparation methods of claims 9-12.

14. A battery device comprising a plurality of solid-state battery cells as described in any one of claims 1-8.

15. An electrical device comprising the battery device of claim 14.

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