A positive electrode, a solid-state battery, and an electrical device

Abstract

This application provides a positive electrode sheet, the positive electrode active material layer of which includes a positive electrode active material, a first solid electrolyte, and a second solid electrolyte. The first solid electrolyte and the second solid electrolyte are made of different materials; the second solid electrolyte includes a sulfide solid electrolyte; the first solid electrolyte is located between the positive electrode active material and the sulfide solid electrolyte to reduce the direct contact area between the sulfide solid electrolyte and the positive electrode active material; the positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g. The positive electrode sheet of this application, firstly, introduces two solid electrolytes and places the first solid electrolyte between the positive electrode active material and the sulfide solid electrolyte, reducing the thermal decomposition behavior caused by direct contact between the positive electrode active material and the sulfide solid electrolyte; secondly, it ensures that the unit positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g, further enhancing electrode stability. These two measures work synergistically to solve the safety problem of solid-state batteries.

Description

Technical Field

[0001] This application relates to the field of positive electrode sheets, specifically to a positive electrode sheet, a solid-state battery, and an electrical device. Background Technology

[0002] Solid-state batteries, which use solid electrolytes instead of traditional liquid electrolytes, represent a significant direction in current battery technology development. Sulfide solid electrolytes, in particular, have attracted considerable attention due to their advantages such as high ionic conductivity and a wide electrochemical window. However, solid-state batteries still face a series of challenges in practical applications, one of the main being their thermal safety, especially the thermal safety of the cathode. Therefore, improving the safety of the cathode, and thus addressing the overall safety issues of solid-state batteries, has become a key research challenge in this field. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this application provides a positive electrode, a solid-state battery, and an electrical device, wherein the positive electrode used in a solid-state battery helps to solve the safety issues of solid-state batteries.

[0004] This application provides a positive electrode sheet, including a positive electrode active material layer, the positive electrode active material layer including a positive electrode active material and a solid electrolyte; the solid electrolyte includes a first solid electrolyte and a second solid electrolyte, the first solid electrolyte and the second solid electrolyte being made of different materials; the second solid electrolyte includes a sulfide solid electrolyte; the first solid electrolyte is located between the positive electrode active material and the sulfide solid electrolyte to reduce the direct contact area between the sulfide solid electrolyte and the positive electrode active material; the positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g, where ω is the mass ratio of the sulfide solid electrolyte to the positive electrode active material layer, and Q is the total heat generated per unit of the positive electrode active material layer under 100% SOC state of charge, measured by differential scanning calorimetry at 25℃~500℃. To improve the thermal safety of solid-state batteries, this positive electrode employs a dual protection mechanism: First, two solid electrolytes are introduced, with the first solid electrolyte positioned between the positive electrode active material and the sulfide solid electrolyte, reducing thermal decomposition caused by direct contact between the positive electrode active material and the sulfide solid electrolyte; second, the unit positive electrode active material layer is ensured to meet the requirements of 0 J / g < ω·Q < 117 J / g, further enhancing electrode stability. These two measures work synergistically to address the safety issues of solid-state batteries.

[0005] Optionally, the first solid electrolyte is coated on the surface of the positive electrode active material; preferably, the coating amount of the first solid electrolyte is 1% to 10%; more preferably, the coating amount of the first solid electrolyte is 2% to 5%.

[0006] Optionally, 62 J / g < ω·Q < 86 J / g; and / or, 180 J / g < Q < 515 J / g; and / or, 0.05 < ω < 0.21; preferably, 0.15 ≤ ω ≤ 0.18.

[0007] Optionally, the mass ratio of the first solid electrolyte to the sulfide solid electrolyte is A, where A > 0.037; preferably, 0.08 < A ≤ 0.53.

[0008] Optionally, the positive electrode active material includes at least one of a ternary positive electrode material, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium nickelate, and lithium-rich manganese-based.

[0009] Optionally, the positive electrode active material includes a ternary positive electrode material, and the molecular formula of the ternary material is Li

[0014] ,

[0013] , ,

[0012] , ,

[0011] , , (Ni x Co y Mn z M b )O 2+d Z c , M includes one or more of Al, Zr, Ti, Y, Cr, and Fe, Z includes one or more of F, Cl, Br, and OH, - 0.10 ≤ a ≤ 0.10, 0 ≤ b ≤ 0.10, 0 ≤ c ≤ 0.20, - 0.20 ≤ d ≤ 0.20, 0.3 ≤ x ≤ 1, 0 < y ≤ 1, 0 < z ≤ 1.

[0010] Optionally, the positive electrode active material includes one or more of single crystal materials, quasi-single crystal materials, and polycrystalline materials.

[0011] Optionally, the positive electrode sheet further includes a binder; the mass ratio of the binder to the positive electrode active material layer is 0.1% - 2%; or, the positive electrode sheet further includes a conductive agent; the mass ratio of the conductive agent to the positive electrode active material layer is 0.1% - 2%; or, the positive electrode sheet further includes a binder and a conductive agent, and the mass ratios of the binder and the conductive agent to the positive electrode active material layer are 0.1% - 2% respectively. <00​​​​​​​​

[0015] Optionally, the additive is selected from at least one of LiCl, LiNO3, Li2CO3, Al2O3, Li[(FSO2)2N], Na[(FSO2)2N], K[(FSO2)2N], Rb[(FSO2)2N], and Na[(FSO2)(CF3SO2)N].

[0016] This application also provides a solid-state battery, which includes the positive electrode sheet as described above. The solid-state battery is any one of a single solid-state battery cell, a solid-state battery module, and a solid-state battery pack. This solid-state battery has high safety.

[0017] Optionally, the solid-state battery further includes a solid electrolyte membrane and a negative electrode. The solid electrolyte membrane is located between the positive electrode and the negative electrode. The solid electrolyte membrane includes a third solid electrolyte, which may be made of the same or different material as the first solid electrolyte and the second solid electrolyte.

[0018] This application also provides an electrical device, including the positive electrode as described above or the solid-state battery as described above. This electrical device possesses all the features and advantages of the aforementioned positive electrode and solid-state battery, which will not be repeated here. Detailed Implementation

[0019] To enable those skilled in the art to better understand the solutions of this application, a further detailed description of this application is provided below. The specific embodiments listed below are merely descriptions of the principles and features of this application; the examples are only for explaining this application and are not intended to limit its scope. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] Solid-state batteries, due to their high energy density, have broad application prospects in future electric vehicles, consumer electronics, and other fields. As a key material for achieving solid-state battery performance, sulfide solid electrolytes are currently the mainstream choice. Solid-state batteries are mainly composed of stacked solid materials, with the positive electrode formed by mixing the positive electrode active material and the solid electrolyte in a "solid-solid contact" manner and applying pressure. In the delithiated state, the positive electrode active material exhibits strong oxidizing properties, while the sulfide solid electrolyte is usually in a lower valence state and has reducing properties. When the two come into contact, there is a high chemical reaction potential. Once a solid-state battery experiences thermal runaway, the charged positive electrode active material decomposes and releases oxygen, which acts as a combustion promoter, intensifying the thermal decomposition reaction of the sulfide solid electrolyte. The violent exothermic reaction between the two releases a large amount of heat and generates a strong impact, thus posing a serious threat to the safety of the solid-state battery.

[0021] Currently, to improve the thermal safety of solid-state batteries, additives with endothermic properties are typically added to the positive electrode. However, this approach has the following drawbacks: the positive electrode active material in the positive electrode active material layer remains in large-area contact with the sulfide solid electrolyte, failing to effectively inhibit its thermal decomposition behavior.

[0022] Based on this, embodiments of this application provide a positive electrode sheet, including a positive electrode active material layer, which includes a positive electrode active material and a solid electrolyte; the solid electrolyte includes a first solid electrolyte and a second solid electrolyte, the first solid electrolyte and the second solid electrolyte being made of different materials; the second solid electrolyte includes a sulfide solid electrolyte; the first solid electrolyte is located between the positive electrode active material and the sulfide solid electrolyte to reduce the direct contact area between the sulfide solid electrolyte and the positive electrode active material; the positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g, where ω is the mass ratio of the sulfide solid electrolyte to the positive electrode active material layer, and Q is the total heat generated per unit positive electrode active material layer under 100% SOC state of charge, measured by differential scanning calorimetry at 25℃~500℃.

[0023] To improve the thermal safety of solid-state batteries, the positive electrode sheet provided in this application adopts a dual protection: First, two solid electrolytes are introduced, and the first solid electrolyte is placed between the positive electrode active material and the sulfide, reducing the thermal decomposition behavior caused by direct contact between the positive electrode active material and the sulfide solid electrolyte; second, the content of the sulfide solid electrolyte affects the amount of its decomposition products (H2S, SO2, etc.), and H2S and SO2 substances can further trigger thermal runaway; at the same time, the heat release Q of the positive electrode sheet in the high charge state affects the ignition point of the battery. Therefore, the inventors of this application have found through research that when the range of 0 J / g < ω·Q < 117 J / g is controlled, the electrode stability is further enhanced. These two measures work together to solve the safety problem of solid-state batteries.

[0024] In some embodiments of this application, the aforementioned sulfide solid electrolyte is Li 7-m+a-c-d M m / n P 1-a A a S 5- b D b Cl c X d (M = one or more of Na, Mg, Ca, Zn, Al; A = one or more of Si, Sn, Ge; D = one or more of O, Se; X = one or more of Br, I, 0≤m≤1, 1≤n≤3, 0≤a≤1, 0≤b≤2, 0≤c<2, 0≤d<2, 1≤c+d<2).

[0025] For example, ω·Q can be a range of 1 J / g, 10 J / g, 20 J / g, 30 J / g, 34 J / g, 40 J / g, 45 J / g, 50 J / g, 55 J / g, 60 J / g, 62 J / g, 67 J / g, 74 J / g, 80 J / g, 84 J / g, 90 J / g, 97 J / g, 100 J / g, 105 J / g, 110 J / g, 116 J / g, or any combination thereof.

[0026] The total heat generation Q of the unit positive electrode active material layer in the differential scanning calorimetry (DSC) test at 25℃~500℃ can be obtained through the following test: The solid-state battery is charged and discharged three times under a pressure of 20MPa and a voltage range of 2.5V~4.2V, with a charge / discharge current of 0.1C. During the last charge to 4.2V, the positive electrode sheet is disassembled. The positive electrode active material layer on the disassembled positive electrode sheet is scraped off with a scraper in an argon-filled glove box and weighed to obtain the mass M1 of the positive electrode active material layer. The weighed material is then placed in a gold-plated crucible, which is then sealed and placed in a differential scanning calorimeter (DSC). The temperature is increased from 25℃ to 500℃ at a rate of 10 K / min, all under an argon atmosphere (gas flow rate of 50 mL / min). The DSC instrument records each endothermic and exothermic peak during the DSC test. The total heat release is obtained by integrating each endothermic and exothermic peak in the DSC test spectrum. Q is the ratio of the total heat release obtained by integration to the mass of the positive electrode active material layer (M1), with units of J / g (joules per gram).

[0027] The mass ratio ω of the sulfide solid electrolyte to the positive electrode active material layer can be obtained through the following test: The solid-state battery is charged and discharged three times within a voltage range of 2.5V to 4.2V at a pressure of 20MPa, with a charge / discharge current of 0.1C. During the final discharge to 2.5V, the positive electrode is disassembled. In an argon-filled glove box, the positive electrode active material layer is peeled off using a scraper. 0.05-0.06 g is accurately weighed using an analytical balance, and the mass m1 (accurate to 0.0001 g) is recorded. The weighed sample is placed in a 20 mL screw-cap headspace vial and sealed tightly. In a dew point chamber, 2 mL of sodium hydroxide solution (1 mol / L) is slowly added dropwise to the sample in the headspace vial using a syringe. After shaking several times, it is allowed to stand for 30 min. Then, a 30% hydrogen peroxide solution is slowly added dropwise to the vial using a syringe, and allowed to stand for 30 min. This process ensures that the H2S overflow is 0 ppm. Next, 2 mL of dilute hydrochloric acid was poured into the bottle. After removing the cap from the screw-top headspace bottle, it was transferred to a digestion cup, and 10 mL of concentrated nitric acid (65%-68% by mass) was added to make the pH of the system < 6. The solution was then boiled on a 300°C hot plate for 30 min. The mass percentages (wt%) of S and P in the above test solution were determined using ICP-OES. For example, the general formula for LPSCl type sulfide solid electrolytes is Li. 6-x PS 5-x Cl 1+x The ratio of the mass percentage of S and P elements to their corresponding molar mass is calculated by dividing the mass percentage by the molar mass ratio. Solving for x yields the chemical formula and molar mass M of the sulfide solid electrolyte. LPSCl The calculated mass percentage of the sulfide solid electrolyte is the mass ratio ω of the sulfide solid electrolyte to the positive electrode active material layer. For special sulfide solid electrolytes doped with elements such as Br, F, and I, elemental quantitative analysis of the sulfide electrolyte region can be performed using scanning electron microscopy / transmission electron microscopy combined with energy dispersive spectroscopy (SEM-EDS), and cross-validation can be performed using XRD Rietveld refinement, XPS, and TGA weight loss analysis.

[0028] In some embodiments of this application, the first solid electrolyte is coated on the surface of the positive electrode active material. This reduces direct contact between the sulfide solid electrolyte and the positive electrode active material, thus improving the thermal stability of the positive electrode.

[0029] The first solid electrolyte is coated on the surface of the positive electrode active material. It can be premixed, ball-milled or ground, and the coating can be layered, dotted or island-shaped.

[0030] In some embodiments of this application, the coating amount of the first solid electrolyte is 1% to 10%. A coating amount within this range achieves better coating effect and improves the thermal stability of the positive electrode. More preferably, the coating amount of the first solid electrolyte is 2% to 5%.

[0031] As is understandable, coating amount refers to the mass percentage of the first solid electrolyte relative to the total weight of the positive electrode active material and the first solid electrolyte.

[0032] In some embodiments, 62 J / g < ω·Q < 86 J / g. Thus, the positive electrode exhibits better safety and can better mitigate the safety risks of solid-state batteries.

[0033] In some embodiments, 180 J / g <Q<515 J / g。

[0034] For example, Q can be a range of 180 J / g, 200 J / g, 250 J / g, 300 J / g, 307 J / g, 313 J / g, 350 J / g, 351 J / g, 380 J / g, 382 J / g, 393 J / g, 400 J / g, 415 J / g, 432 J / g, 465 J / g, 467 J / g, 500 J / g, 515 J / g, or any combination thereof.

[0035] In the positive electrode system of this application embodiment, by controlling the total heat generation Q of the unit positive electrode active material layer to meet the above range during differential scanning calorimetry testing at 25°C to 500°C, it helps to reduce the reactivity of the positive electrode and weaken the resulting impact effect, thereby improving the safety performance of the solid-state battery.

[0036] In some embodiments, 0.06 < ω < 0.21.

[0037] For example, ω can be a range of 0.07, 0.08, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, or any combination thereof.

[0038] In the positive electrode system of this application embodiment, the mass ratio ω of the sulfide solid electrolyte to the positive electrode active material layer is within the above range, which helps to balance the ionic conductivity and safety stability of the positive electrode.

[0039] In some embodiments, 0.15 ≤ ω ≤ 0.18.

[0040] In some embodiments, the mass ratio of the first solid electrolyte to the sulfide solid electrolyte is A, wherein A > 0.037.

[0041] In the positive electrode system of this application embodiment, by satisfying the above range by the mass ratio A of the first solid electrolyte to the sulfide solid electrolyte, it helps to reduce the effective contact area between the positive electrode active material and the sulfide solid electrolyte, thereby reducing safety risks.

[0042] Preferably, 0.08 < A ≤ 0.53.

[0043] For example, A can be a range of 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.32, 0.39, 0.43, 0.48, 0.51, 0.53, or any combination thereof.

[0044] In some embodiments, the positive electrode active material includes at least one of ternary positive electrode materials, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, and lithium-rich manganese-based materials.

[0045] In the positive electrode system of this application embodiment, the above-mentioned positive electrode active material and solid electrolyte work synergistically to help improve the safety of the positive electrode, suppress the safety risks of solid-state batteries, and at the same time help increase the electrochemical performance of solid-state batteries.

[0046] In some embodiments, the positive electrode active material includes a ternary positive electrode material, wherein the molecular formula of the ternary material is Li. a+1 (Ni x Co y Mn z M b )O 2+d Z c M includes one or more of Al, Zr, Ti, Y, Cr, and Fe, Z includes one or more of F, Cl, Br, and OH, -0.10≤a≤0.10, 0≤b≤0.10, 0≤c≤0.20, -0.20≤d≤0.20, 0.3≤x≤1, 0<y≤1, and 0<z≤1.

[0047] Preferably, 0.3 ≤ x ≤ 0.95; more preferably, 0.50 ≤ x ≤ 0.75.

[0048] It is understandable that x + y + z + b = 1.

[0049] In addition, the positive electrode active material may include one or more of single crystal materials, single crystal-like materials, and polycrystalline materials.

[0050] Single-crystal materials refer to materials where the entire particle is a single, continuous crystal, and the atoms inside the particle are arranged in a highly ordered and regular periodic pattern throughout the entire particle, exhibiting a consistent crystallographic orientation.

[0051] Polycrystalline materials refer to materials in which a secondary spherical particle is formed by the aggregation of a large number of primary particles (i.e., single crystals) at the nanometer or submicrometer scale. These primary particles are interconnected through grain boundaries.

[0052] Single-crystal-like materials are a concept that lies between single crystals and polycrystalline materials. They typically refer to particles formed by the fusion of a few (usually 2-5) large primary particles in a specific orientation. Unlike polycrystalline materials, which are composed of countless small grains, they are not a perfect single crystal.

[0053] In the cathode system of this application embodiment, the above-mentioned positive electrode active material includes one or more of single crystal materials, quasi-single crystal materials and polycrystalline materials, which helps to improve the safety of the cathode, suppress the safety risks of solid-state batteries, and at the same time help to increase the electrochemical performance of solid-state batteries.

[0054] In some embodiments, the positive electrode sheet further includes a binder; the mass ratio of the binder to the positive electrode active material layer is 0.1% to 2%.

[0055] For example, the mass ratio of binder to positive electrode active material layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any combination thereof.

[0056] In some embodiments, the positive electrode sheet further includes a conductive agent; the mass ratio of the conductive agent to the positive electrode active material layer is 0.1% to 2%.

[0057] For example, the mass ratio of the conductive agent to the positive electrode active material layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any combination thereof.

[0058] In some embodiments, the positive electrode sheet further includes a binder and a conductive agent, wherein the mass ratio of the binder and the conductive agent to the positive electrode active material layer is independently 0.1% to 2%.

[0059] For example, the mass ratio of the conductive agent to the positive electrode active material layer is in the range of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any two of these; the mass ratio of the binder to the positive electrode active material layer is in the range of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any two of these.

[0060] For example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), hydrogenated nitrile butadiene rubber (HNBR), natural rubber (HNR), sodium polyacrylate (SA), and polytetrafluoroethylene (PTFE).

[0061] For example, the conductive agent may include one or more of carbon nanotubes, carbon nanofibers (VGCF), conductive carbon black (CB), Ketjen black, graphene, and graphyne.

[0062] In the positive electrode system of this application embodiment, a binder and / or a conductive agent are further included, and the content is controlled within the above range. This is beneficial to further increase the adhesion between the active material layer and the current collector on the positive electrode, and / or the conductivity of the positive electrode. At the same time, it ensures the conductivity uniformity between the positive electrode active material and the sulfide solid electrolyte, which helps to better improve the safety of the positive electrode, suppress the safety risks of solid-state batteries, and also helps to increase the electrochemical performance of solid-state batteries.

[0063] In some embodiments, the first solid electrolyte includes at least one of a polymeric electrolyte, an oxide solid electrolyte, and a halide solid electrolyte.

[0064] In the positive electrode system of this application embodiment, the first solid electrolyte includes the above-mentioned substances, which can increase the stability of the positive electrode system and has ionic conductivity, suppressing the safety risks of solid-state batteries, and at the same time helping to increase the electrochemical performance of solid-state batteries.

[0065] In some embodiments, the first solid electrolyte is a halide solid electrolyte. In addition to the functions described above, the halide solid electrolyte can also capture oxygen, thereby reducing the oxygen generated by the positive electrode active material during heating, and further improving the thermal safety of the solid-state battery.

[0066] Halogen solid electrolytes include Li a MXb The element M is selected from one or more of the following elements: Mg, Ca, Sr, Ba, Zn, Al, Ga, In, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Bi, Zr, Hf, Ti, Nb, or Ta. Preferably, M is Y, Yb, or Zr. X is selected from one or more of F, Cl, and Br. Other modified novel halide solid electrolytes, such as those doped with O, may also be included. Different types of halide solid electrolytes selected in this application result in different endothermic and exothermic processes, thus affecting the thermal stability and safety of the solid-state battery. A comprehensive selection based on the electrochemical performance, safety, and cost of the solid-state battery is made to achieve superior performance from the halide solid electrolyte.

[0067] In some embodiments of this application, the coating amount of different halide solid electrolytes (the proportion of the mass of the halide solid electrolyte to the total mass of the positive electrode active material and the halide solid electrolyte) is adjusted to 1% to 10%. Preferably, the coating amount is 2% to 5%. More preferably, the coating amount is 4%.

[0068] In some embodiments, the mass ratio of the positive electrode active material to the solid electrolyte is (78~90):(22~10).

[0069] For example, the mass ratio of the positive electrode active material to the solid electrolyte is a range of 78:22, 80:20, 85:15, 90:10, or any combination thereof.

[0070] In the positive electrode system of this application embodiment, the mass ratio of positive electrode active material to solid electrolyte not only helps to improve the safety of the positive electrode and suppress the safety risks of solid-state batteries, but also helps to increase the electrochemical performance of solid-state batteries.

[0071] In some embodiments, the positive electrode also includes an additive that can undergo an endothermic phase transition.

[0072] In the positive electrode system of this application embodiment, the addition of an additive that can undergo an endothermic phase change can absorb the heat of reaction, effectively enhance the stability of the positive electrode system and reduce the release of heat.

[0073] In some embodiments, the mass ratio of the first solid electrolyte to the additive is (9~3):(1~7).

[0074] For example, the mass ratio of the first solid electrolyte to the additive is a range of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, or any two of these.

[0075] In some embodiments, the additive is selected from at least one of LiCl, LiNO3, Li2CO3, Al2O3, Li[(FSO2)2N], Na[(FSO2)2N], K[(FSO2)2N], Rb[(FSO2)2N], and Na[(FSO2)(CF3SO2)N].

[0076] In the positive electrode system of this application embodiment, the addition of the above-mentioned additives can not only reduce the exothermic reaction, but also increase the ion conduction of the positive electrode, thereby increasing the electrochemical performance of the solid-state battery.

[0077] In some embodiments, the positive electrode sheet further includes a current collector, and the positive electrode active material layer is disposed on at least one side of the current collector.

[0078] The aforementioned positive current collector may include aluminum foil current collectors, composite current collectors, stainless steel current collectors, and current collectors with conductive coatings on the above metal carriers, etc., which can be selected as needed.

[0079] This application does not impose any particular restrictions on the structure and manufacturing process of the positive electrode sheet, as long as the purpose of this application can be achieved.

[0080] The positive electrode sheet of this application embodiment can be prepared by wet or dry batching.

[0081] The positive electrode active material layer is formed by separating the positive electrode active material from the sulfide solid electrolyte using a first solid electrolyte. For example, this application designs the positive electrode active material layer as follows: a premixed coating method is used, where the first solid electrolyte first forms a coating layer on the surface of the positive electrode active material, and then it is mixed with a second solid electrolyte containing the sulfide solid electrolyte to obtain the positive electrode sheet. During the coating process of the first solid electrolyte onto the positive electrode active material, the surface of the positive electrode active material can be pretreated. For example, the surface of the positive electrode active material can be treated with inert gas (Ar) plasma to effectively remove lithium impurities (such as LiOH, Li2CO3) from the surface, thereby generating more activation sites and increasing coating stability. To increase the structural density of the positive electrode sheet, the obtained positive electrode sheet can be further pressurized, with a pressure of 20-300 MPa.

[0082] The first solid electrolyte can mitigate exothermic reactions and promote heat absorption, preventing direct contact between the positive electrode active material and the sulfide solid electrolyte. Furthermore, when the first solid electrolyte is a halide solid electrolyte, a spontaneous chemical reaction occurs between it and the charged positive electrode active material, providing Li to the positive electrode active material, thereby enhancing its structural stability and reducing the possibility of oxygen release. This high-safety positive electrode improves the thermal safety and cycle stability of the solid-state battery system.

[0083] This application also provides a solid-state battery, which includes the above-described positive electrode sheet or a positive electrode sheet obtained according to the above-described method for preparing the positive electrode sheet.

[0084] Based on the aforementioned positive electrode, this solid-state battery has corresponding advantages, which will not be elaborated here.

[0085] It can be understood that the aforementioned solid-state battery refers to any one of a single solid-state battery cell, a solid-state battery module, or a solid-state battery pack.

[0086] In some embodiments, the solid-state battery further includes a solid electrolyte membrane and a negative electrode, with the solid electrolyte membrane located between the positive electrode and the negative electrode; the solid electrolyte membrane includes a third solid electrolyte, which may be made of the same material as or different from the first solid electrolyte and the second solid electrolyte.

[0087] Understandably, the aforementioned solid-state battery also includes a casing.

[0088] Solid electrolyte membranes are dense layers made of solid electrolyte materials, and their function is to conduct lithium ions and isolate electrons.

[0089] Specifically, the third solid electrolyte material in the solid electrolyte membrane may include one or more of the following: sulfide solid electrolyte, oxide solid electrolyte, polymer electrolyte, and halide solid electrolyte.

[0090] The negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, wherein the negative electrode active material layer may include a negative electrode active material (such as a lithium-ion solid-state battery negative electrode active material) and a binder; and / or, a solid electrolyte; and / or, a conductive agent.

[0091] The aforementioned solid-state batteries may include square-shell solid-state batteries, cylindrical solid-state batteries, pouch solid-state batteries, etc.

[0092] Solid-state battery cells can be either wound cells or stacked cells.

[0093] This application also provides a method for preparing a solid-state battery, comprising:

[0094] The positive electrode active material (or negative electrode active material), solid electrolyte, conductive agent, and binder are mixed evenly by wet or dry methods and then coated onto at least one side of the positive electrode current collector (or negative electrode current collector). After drying (e.g., baking), a densification treatment (e.g., rolling) is performed to obtain a positive electrode sheet (or negative electrode sheet). The positive electrode sheet, solid electrolyte membrane, and negative electrode sheet are then arranged in an orderly manner to obtain an electrode core. The electrode core is placed in a casing (shell) and subjected to isostatic pressing. The isostatic pressing pressure can be 200~600MPa, within which the electrode particles can make close contact and short circuits at the electrode edges are minimal. Finally, formation and capacity testing are performed to obtain a solid-state battery.

[0095] In practice, the positive electrode active material (or negative electrode active material), solid electrolyte, conductive agent, binder and solvent can be mixed evenly and then applied to at least one side of the positive electrode current collector (or negative electrode current collector). After drying, a densification treatment is performed to obtain the positive electrode sheet (or negative electrode sheet).

[0096] The aforementioned densification and pressurization process can enhance the transport capacity of ions (such as lithium ions).

[0097] This application provides a solid-state battery module, which includes at least two of the above-described solid-state batteries.

[0098] This application provides a solid-state battery pack, wherein the solid-state battery module includes at least two of the above-described solid-state modules.

[0099] This application provides an electrical device, including the aforementioned solid-state battery, solid-state battery module, or solid-state battery pack, wherein the solid-state battery, solid-state battery module, or solid-state battery pack serves as the power supply for the electrical device.

[0100] The aforementioned electrical equipment may include at least one of the following: sliding chassis, electric vehicles, portable electronic devices, wearable devices, household appliances, and industrial equipment.

[0101] Specifically, electric vehicles may include at least one of electric cars, electric bicycles, and electric scooters; portable electronic devices may include at least one of smartphones, laptops, and tablets; wearable devices may include at least one of smartwatches and fitness trackers; home appliances may include at least one of robotic vacuum cleaners and portable audio equipment; and industrial equipment may include drones.

[0102] The present application will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0103] Example 1

[0104] The method for preparing the positive electrode and solid-state battery provided in this embodiment is as follows:

[0105] (1) Preparation of positive electrode

[0106] In a -50℃ dew point environment, LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811, single crystal) was subjected to inert gas (Ar) plasma treatment for 1 min. The treated NCM811 was then reacted with the halide solid electrolyte Li3Y. 0.2 Zr 0.6 Cl6 (LiYZrCl) was weighed at a halide mass ratio of 4%, thoroughly mixed, and then added to a premixing machine. The mixture was stirred at 4000 r / min for 5 minutes to ensure thorough mixing and homogeneity, yielding the LiYZrCl-coated positive electrode active material LiYZrCl@NCM811.

[0107] In a -50℃ dew point environment, the coated positive electrode active material LiYZrCl@NCM811, sulfide solid electrolyte Li6PS5Cl, conductive agent VGCF, and binder PTFE were thoroughly mixed and fibroped at a weight ratio of 83.33:16.67:1:1 (i.e., positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 80:3.33:16.67:1:1, to maintain the ratio of positive electrode active material to solid electrolyte at 80:20). After fibrosis, the mixture was repeatedly rolled at 120℃, a differential speed of 1:3, and a linear pressure of 0.1 t / cm to obtain a dry-process membrane. Subsequently, the dry-process membrane was thermally bonded to the undercoated foil at 120℃ to finally obtain the dry-process positive electrode sheet.

[0108] (2) Preparation of negative electrode

[0109] In a -50℃ dew point environment, nano-pure silicon particles, conductive carbon (carbon nanotubes), and water-based binder (sodium methyl cellulose-polyacrylic acid CMC-PAA) are dispersed in water at a dry weight ratio of 90:0.5:9.5. The mixture is dispersed by high-speed shearing to form a slurry. The slurry is then sieved and coated onto a copper foil substrate, and dried at 100℃ to obtain a negative electrode sheet.

[0110] (3) Preparation of solid electrolyte membrane

[0111] In a -50℃ dew point environment, the LPSCl type sulfide solid electrolyte Li 5.5 PS 4.5 ClBr 0.5A styrene-butadiene rubber binder (SBR) with a solid content of 13% wt was thoroughly mixed in xylene solvent at a weight ratio of 9:2. The slurry was then sieved and coated onto an aluminum foil substrate, and dried at 100°C to obtain an electrolyte membrane with a thickness of 50 μm.

[0112] (4) Preparation of solid-state pouch cells

[0113] In a -50°C dew point environment, the electrolyte membrane is transferred to both sides of the negative electrode and rolled together. The positive electrode and the transferred negative electrode are then stacked in a layered manner to form a stacked cell. The cell is first packaged and subjected to isostatic pressing at 500MPa to ensure tight interface contact. After unpacking, tabs are welded and the cell is repackaged. After standing, formation, and capacity testing at 500MPa pressure and 45°C, a solid-state battery is obtained.

[0114] Example 2

[0115] Similar to Example 1, the difference is that the mass ratio of positive electrode active material to solid electrolyte is kept constant, and the coating amount of the first solid electrolyte is adjusted to 3%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder is 80:2.47:17.53:1:1.

[0116] Example 3

[0117] Similar to Example 1, the difference is that the mass ratio of positive electrode active material to solid electrolyte is kept constant, and the coating amount of the first solid electrolyte is adjusted to 2%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder is 80:1.63:18.37:1:1.

[0118] Example 4

[0119] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, the mass ratio of the positive electrode active material to the solid electrolyte was kept constant, and the coating amount of the first solid electrolyte was adjusted to 1%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 80:0.81:19.19:1:1.

[0120] Example 5

[0121] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, the mass ratio of the positive electrode active material to the solid electrolyte was kept constant, and the coating amount of the first solid electrolyte was adjusted to 5%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 80: 4.21: 15.79: 1: 1.

[0122] Example 6

[0123] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, the mass ratio of the positive electrode active material to the solid electrolyte was kept constant, and the coating amount of the first solid electrolyte was adjusted to 8%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 80: 6.96: 13.04: 1: 1.

[0124] Example 7

[0125] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, the mass ratio of the positive electrode active material to the solid electrolyte was kept constant, and the coating amount of the first solid electrolyte was adjusted to 10%; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 80: 8.89: 11.11: 1: 1.

[0126] Example 8

[0127] Similar to Example 1, the difference is that the first solid electrolyte is Li3YBr5F.

[0128] Example 9

[0129] Similar to Example 1, the difference is that the positive electrode active material is LiNi. 0.6 Co 0.2 Mn 0.2 O2.

[0130] Example 10

[0131] Similar to Example 1, the difference is that the mass ratio of the positive electrode active material to the solid electrolyte is controlled to be 78:22; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 78:3.25:18.75:1:1.

[0132] Example 11

[0133] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, and the coating amount of the first solid electrolyte was adjusted to 1%; the mass ratio of the positive electrode active material to the solid electrolyte was 78:22; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder = 78:0.79:21.21:1:1.

[0134] Example 12

[0135] Similar to Example 1, the difference lies in that the mass ratio of the positive electrode active material to the solid electrolyte is adjusted to 90:10; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder is 90:3.75:6.25:1:1. Furthermore, the inert gas (Ar) plasma treatment step is not performed.

[0136] Example 13

[0137] Similar to Example 1, the difference lies in that: the first solid electrolyte is adjusted to Li3YBr5F with a coating amount of 8%; the mass ratio of the positive electrode active material to the solid electrolyte is 90:10; at this time, the ratio of positive electrode active material: first solid electrolyte: sulfide solid electrolyte: conductive agent: binder is 90:7.83:2.17:1:1. Furthermore, the inert gas (Ar) plasma treatment step was not performed.

[0138] Example 14

[0139] Similar to Example 1, the difference is that the positive electrode also includes LiCl, which is added during the electrode preparation process, wherein the mass ratio of the first solid electrolyte to LiCl is 9:1.

[0140] Example 15

[0141] Similar to Example 1, the difference is that the positive electrode also includes LiCl, which is added during the electrode preparation process, wherein the mass ratio of the first solid electrolyte to LiCl is 5:5.

[0142] Example 16

[0143] Similar to Example 1, the difference is that the positive electrode also includes LiCl, which is added during the electrode preparation process, wherein the mass ratio of the first solid electrolyte to LiCl is 3:7.

[0144] The main differences between Examples 1 to 16 are shown in Table 1.

[0145] Group Positive electrode active material Mass ratio of positive electrode active material to solid electrolyte First solid electrolyte additive Additive to first solid electrolyte mass ratio Coating amount (%) Example 1 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 4 Example 2 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 3 Example 3 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 2 Example 4 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 1 Example 5 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 5 Example 6 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 8 Example 7 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 10 Example 8 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3YBr5F]]> / / 4 Example 9 <![CDATA[LiNi 0.6 What 0.2 Mn 0.2 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 4 Example 10 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 78:22 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 4 Example 11 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 78:22 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 1 Example 12 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 90:10 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> / / 4 Example 13 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 90:10 <![CDATA[Li3YBr5F]]> / / 8 Example 14 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> LiCl 9:1 4 Example 15 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> LiCl 5:5 4 Example 16 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 80:20 <![CDATA[Li3Y 0.2 Zr 0.6 Cl6]]> LiCl 3:7 4

[0146] Comparative Example 1

[0147] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, the first solid electrolyte was not added to the positive electrode sheet, the ratio of positive electrode active material to solid electrolyte was controlled at 80:20, and other conditions remained unchanged.

[0148] Comparative Example 2

[0149] Similar to Example 1, the difference is that: the positive electrode active material was not treated with inert gas (Ar) plasma, and the first solid electrolyte (Li3Y) in the positive electrode sheet was not subjected to inert gas (Ar) plasma treatment. 0.2 Zr 0.6 The coating amount of Cl6 was 0.5%, the ratio of positive electrode active material to solid electrolyte was controlled at 80:20, and other conditions remained unchanged.

[0150] Comparative Example 3

[0151] The difference between the positive electrode sheet of this comparative example and Example 1 is that, similar to Example 1, the difference lies in that: the positive electrode active material was not treated with inert gas (Ar) plasma, the first solid electrolyte was not added to the positive electrode sheet, the ratio of positive electrode active material to solid electrolyte was controlled at 78:22, and other conditions remained unchanged.

[0152] Comparative Example 4

[0153] The difference between the positive electrode sheet of this comparative example and Example 1 is that, similar to Example 1, the difference lies in that: the positive electrode active material was not treated with inert gas (Ar) plasma, and the first solid electrolyte in the positive electrode sheet was not in direct contact with the positive electrode active material. The specific preparation process is as follows:

[0154] In a -50℃ dew point environment, LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), sulfide solid electrolyte, first solid electrolyte Li3Y 0.2 Zr 0.6 Cl6, conductive agent VGCF, and binder PTFE are directly mixed in a weight ratio of 80:19.19:0.81:1:1. After thorough stirring and uniform mixing, the mixture is fiberized and repeatedly rolled at 120℃, a differential speed of 1:3, and a linear pressure of 0.1t / cm to obtain a dry-process membrane. Subsequently, the dry-process membrane is thermally bonded with a base coating foil at 120℃ to finally obtain a dry-process positive electrode sheet.

[0155] Test case

[0156] The following parameters of each embodiment and comparative example were tested, and the test results are shown in Table 2.

[0157] (1) The total heat generation Q of the positive electrode active material layer in the differential scanning calorimetry test at 25℃~500℃ can be obtained by the following test: The solid-state battery is charged and discharged 3 times under a pressure of 20MPa and a voltage range of 2.5V~4.2V, with a charge and discharge current of 0.1C. When the last charge is 0.1C to 4.2V, the positive electrode sheet is disassembled. The positive electrode active material layer on the disassembled positive electrode sheet is scraped off with a ceramic knife in an argon glove box and weighed to obtain the mass M1 of the positive electrode active material layer. Then, the weighed material is placed in a gold-plated crucible, and the gold-plated crucible is sealed and placed in a DSC instrument. The temperature is increased from 25℃ to 500℃ at a heating rate of 10 K / min, and the whole process is carried out in an argon atmosphere (gas flow rate of 50 mL / min). The DSC instrument records each endothermic and exothermic peak during the DSC test process. The total heat release is obtained by integrating each endothermic and exothermic peak in the DSC test spectrum. Q is the ratio of the total heat release obtained by integration to the mass of the positive electrode active material layer (M1), with units of J / g (joules per gram).

[0158] (2) The mass ratio of the sulfide solid electrolyte to the positive electrode active material layer can be accurately determined by alkaline absorption method and ICP-OES (inductively coupled plasma atomic emission spectrometry) to estimate the content of elements such as S, P, and Li in the sulfide solid electrolyte. Specifically, the solid battery is charged and discharged three times under a pressure of 20 MPa and a voltage range of 2.5V to 4.2V, with a charge and discharge current of 0.1C. When the battery is discharged to 2.5V for the last time, the positive electrode is disassembled. In a glove box filled with argon gas, the positive electrode active material layer on the positive electrode is peeled off with a ceramic knife. The sample is accurately weighed using an analytical balance, and the mass m is recorded (accurate to 0.0001 g). The weighed sample is placed in a 20 mL screw-top headspace vial and sealed tightly. In a dew point chamber, 2 mL of sodium hydroxide solution (10 mol / L) was slowly added dropwise to the sample in a screw-top headspace vial using a syringe. After shaking several times and standing for 30 min, 30% hydrogen peroxide solution was slowly added dropwise using a syringe and allowed to stand for 30 min. This process ensures that the H2S overflow is 0 ppm. Then, 2 mL of dilute hydrochloric acid was added to the vial. After removing the cap from the screw-top headspace vial, the sample was transferred to a digestion cup, and 10 mL of concentrated nitric acid (65%-68% nitric acid) was added to make the pH < 6. The solution was then boiled on a 300℃ hot plate for 30 min. The mass percentages (wt%) of S and P in the test solution were determined using ICP-OES. The general formula for LPSCl type electrolytes is Li 6-x PS 5-x Cl 1+x The ratio of the mass percentage of S and P elements to their corresponding molar mass is calculated by dividing the mass percentage by the molar mass ratio. Solving for x yields the chemical formula and molar mass M of the electrolyte.LPSCl The calculated mass ratio of the electrolyte is the mass ratio ω of the sulfide solid electrolyte to the positive electrode active material layer. .

[0159] For special sulfide solid electrolytes doped with elements such as Br, F, and I, elemental quantitative analysis of the sulfide electrolyte region can be performed using scanning electron microscopy / transmission electron microscopy combined with energy dispersive spectroscopy (SEM-EDS), and cross-validation can be performed using XRD Rietveld refinement, XPS, and TGA weight loss analysis.

[0160] Table 2

[0161] Group ω Q (J / g) ω·Q (J / g) A Example 1 0.1634 414.56 67.74 0.2 Example 2 0.1718 431.62 74.15 0.1412 Example 3 0.1801 466.67 84.05 0.0889 Example 4 0.1882 514.81 96.89 0.0421 Example 5 0.1548 393.07 60.85 0.2667 Example 6 0.1279 350.55 44.84 0.5333 Example 7 0.1089 307.42 33.48 0.8 Example 8 0.1634 381.58 62.35 0.2 Example 9 0.1634 312.55 51.07 0.2 Example 10 0.1838 465.23 85.51 0.1733 Example 11 0.2080 560.08 116.50 0.0371 Example 12 0.0613 331.1 20.30 0.6 Example 13 0.0213 180.34 3.84 3.6 Example 14 0.1634 410.23 67.03 0.18 Example 15 0.1634 400.32 65.41 0.1 Example 16 0.1634 395.24 64.58 0.06 Comparative Example 1 0.1961 638.45 125.20 0 Comparative Example 2 0.1921 615.3 118.20 0.0205 Comparative Example 3 0.2157 672.37 145.03 0 Comparative Example 4 0.1882 632.45 119.03 0.0421

[0162] Battery performance test

[0163] The following battery performance tests were conducted on each embodiment and comparative example, and the test results are shown in Table 3.

[0164] (1) Ratio performance test

[0165] Apply a pressure of 20 MPa to the battery and charge it at 45°C at 0.1C to 4.2V. Then, charge it at a constant voltage of 4.2V until the charging current is less than or equal to 0.05C. After resting for 10 minutes, discharge it at 0.1C to 2.5V. Record the discharge capacity as C0. Charge it at 0.1C to 4.2V and charge it at a constant voltage of 4.2V until the current is less than or equal to 0.05C. Then discharge it at 1C to 2.5V. Record the 1C discharge capacity as C1. The 1C discharge capacity retention rate is C1 / C0.

[0166] (2) First-cycle coulomb efficiency test (first-cycle efficiency) and first-cycle discharge capacity test

[0167] A pressure of 20 MPa was applied to the battery, and the solid-state battery was charged at 0.1C to 4.2V at 45℃. Then, it was charged at a constant voltage of 4.2V until the charging current was less than or equal to 0.05C. After resting for 10 minutes, it was discharged at 0.1C to 2.5V, and its discharge specific capacity C was recorded. The first-cycle coulombic efficiency of the battery = first-cycle discharge specific capacity / first-cycle charge specific capacity × 100%.

[0168] (3) Battery safety test

[0169] The pouch cells prepared in the examples and comparative examples were charged to 4.2V under a pressure of 20MPa and then placed in an oven. The oven temperature was increased to 250℃±2℃ at a rate of 1℃ / min and held at this temperature for 1 hour. The cell temperature changes were monitored during the process to obtain the trigger temperature T1 and the maximum temperature T2. T1 refers to the critical temperature at which the cell surface temperature first experiences a sharp, spontaneous, nonlinear jump during the battery heating process. This jump typically indicates the onset of exothermic side reactions inside the battery, i.e., the trigger point for thermal runaway; a higher trigger temperature T1 indicates a more stable battery. T2 refers to the maximum value reached by the battery surface temperature throughout the entire test (including the heating and holding phases). This temperature reflects the severity of the thermal runaway process; a higher maximum temperature T2 indicates a greater risk of thermal runaway.

[0170] Table 3

[0171] Group Ratio performance (%) First-efficacy (%) First-cycle discharge specific capacity (mAh / g) <![CDATA[Highest temperature T2 (°C)]]> <![CDATA[Trigger temperature T1 (°C)]]> Example 1 74.5 85.67 202.7 800.12 230.25 Example 2 73.7 85.34 201.1 814.34 217.37 Example 3 73.1 85.22 200.6 820.5 202 Example 4 72.9 85.01 200 832.27 190.11 Example 5 72.6 84.93 199.2 793.82 235.29 Example 6 70.3 84.24 195.2 780.46 238 Example 7 69.4 83.7 193.1 750.33 246.15 Example 8 65.6 83.74 199 791.17 236.7 Example 9 76.6 85.71 185.2 778.5 240.04 Example 10 75.2 85.72 202.8 816.21 215.37 Example 11 73.8 85.21 200.8 844.34 185.4 Example 12 70.2 85.2 200.7 790.02 233.21 Example 13 55.8 82.90 188.1 700.25 261.9 Example 14 70.4 84.72 198.3 795.56 234 Example 15 60.8 83 190 794.08 233.6 Example 16 52.1 80.14 179.9 793.11 232.1 Comparative Example 1 85.7 83.5 204 870.51 170.55 Comparative Example 2 77.7 84.6 202.2 860.25 178.72 Comparative Example 3 86.3 84.14 204.3 890.76 165.18 Comparative Example 4 75.3 84.9 201.1 869.31 171.46

[0172] Based on the above test results, it can be seen that, compared with the positive electrode sheet in the comparative example, the positive electrode sheet in this embodiment includes a first solid electrolyte and a second solid electrolyte, and the second solid electrolyte includes a sulfide solid electrolyte; the first solid electrolyte is located between the positive electrode active material and the sulfide solid electrolyte, and the positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g, the battery has a high trigger temperature T1 and a low maximum temperature T2, which can effectively solve the safety problem of solid-state batteries.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A positive electrode plate, characterized in that, It includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material and a solid-state electrolyte; the solid-state electrolyte includes a first solid-state electrolyte and a second solid-state electrolyte, and the materials of the first solid-state electrolyte and the second solid-state electrolyte are different; the second solid-state electrolyte includes a sulfide solid-state electrolyte; the first solid-state electrolyte is located between the positive electrode active material and the sulfide solid-state electrolyte to reduce the direct contact area between the sulfide solid-state electrolyte and the positive electrode active material; the positive electrode active material layer satisfies 0 J / g < ω·Q < 117 J / g, where ω is the mass ratio of the sulfide solid-state electrolyte to the positive electrode active material layer, and Q is the total heat generation amount of the unit positive electrode active material layer during differential scanning calorimetry testing at 25°C to 500°C under 100% SOC state of charge.

2. The positive electrode sheet according to claim 1, characterized in that, The first solid-state electrolyte coats the surface of the positive electrode active material; preferably, the coating amount of the first solid-state electrolyte is 1% to 10%; more preferably, the coating amount of the first solid-state electrolyte is 2% to 5%.

3. The positive electrode sheet according to claim 1 or 2, characterized in that, 62 J / g < ω·Q < 86 J / g; and / or, 180 J / g < Q < 515 J / g; and / or, 0.06 < ω < 0.21; preferably, 0.15 ≤ ω ≤ 0.

18.

4. The positive electrode sheet according to any one of claims 1-3, characterized in that, The mass ratio of the first solid-state electrolyte to the sulfide solid-state electrolyte is A, where A > 0.037; preferably, 0.08 < A ≤ 0.53 is taken for A.

5. The positive electrode sheet according to any one of claims 1-4, characterized in that, The positive electrode active material includes at least one of ternary positive electrode materials, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, lithium nickelate, and lithium-rich manganese-based materials.

6. The positive electrode sheet according to any one of claims 5, characterized in that, The positive electrode active material includes a ternary positive electrode material, the molecular formula of which is Li. a+1 (Ni x Co y Mn z M b )O 2+d Z c M includes one or more of Al, Zr, Ti, Y, Cr, and Fe, Z includes one or more of F, Cl, Br, and OH, -0.10≤a≤0.10, 0≤b≤0.10, 0≤c≤0.20, -0.20≤d≤0.20, 0.3≤x≤1, 0<y≤1, and 0<z≤1.

7. The positive electrode sheet according to claim 5 or 6, characterized in that, The positive electrode active material includes one or more of single crystal materials, quasi-single crystal materials, and polycrystalline materials.

8. The positive electrode sheet according to any one of claims 1-7, characterized in that, The positive electrode sheet further includes a binder; the mass ratio of the binder to the positive electrode active material layer is 0.1% to 2%; or The positive electrode sheet further includes a conductive agent; the mass ratio of the conductive agent to the positive electrode active material layer is 0.1% to 2%; or, The positive electrode sheet further includes a binder and a conductive agent, and the mass ratios of the binder and the conductive agent to the positive electrode active material layer are each independently 0.1% to 2%.

9. The positive electrode sheet according to any one of claims 1-8, characterized in that, The first solid-state electrolyte includes at least one of polymer solid-state electrolytes, oxide solid-state electrolytes, and halide solid-state electrolytes; preferably, the first solid-state electrolyte is a halide solid-state electrolyte.

10. The positive electrode sheet according to any one of claims 1-9, characterized in that, The mass ratio of the positive electrode active material to the solid-state electrolyte is (78 to 90):(22 to 10).

11. The positive electrode sheet according to any one of claims 1-10, characterized in that, The positive electrode sheet further includes an additive, and the additive can undergo an endothermic phase change; preferably, the mass ratio of the first solid-state electrolyte to the additive is (9 to 3):(1 to 7).

12. The positive electrode sheet according to any one of claims 11, characterized in that, The additive is selected from at least one of LiCl, LiNO3, Li2CO3, Al2O3, Li[(FSO2)2N], Na[(FSO2)2N], K[(FSO2)2N], Rb[(FSO2)2N], and Na[(FSO2)(CF3SO2)N].

13. A solid-state battery, characterized in that, The solid-state battery includes the positive electrode sheet according to any one of claims 1-12, and the solid-state battery is any one of a single solid-state battery cell, a solid-state battery module, and a solid-state battery pack.

14. The solid-state battery according to any one of claims 13, characterized in that, It also includes a solid electrolyte membrane and a negative electrode, wherein the solid electrolyte membrane is located between the positive electrode and the negative electrode; the solid electrolyte membrane includes a third solid electrolyte, which may be made of the same material as the first solid electrolyte and the second solid electrolyte, or may be made of a different material.

15. An electrical appliance, characterized in that, Includes the positive electrode sheet as described in claims 1-12; or the solid-state battery as described in claim 13 or 14.