Positive pole piece, solid-state battery and electric device

Abstract

The invention discloses a positive pole piece, a solid-state battery and an electric device. The positive pole piece comprises a current collector and an active layer, the active layer is arranged on at least one surface of the current collector, the active layer comprises a middle layer and a surrounding layer arranged around the middle layer, and the conductivity of the surrounding layer is larger than that of the middle layer. Therefore, the conductivity of the periphery of the positive pole piece is higher than that of the middle part, so that the problem that the diffusion speed of lithium ions on the periphery of the positive pole piece is slower than that of the middle part due to non-uniform heat distribution can be solved, and the battery capacity exertion and cycle performance is improved.

Description

Technical Field

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

[0002] Currently, solid-state batteries are demonstrating an increasingly important research position in the field of novel batteries due to their excellent safety performance. Solid electrolytes, as one of the components of solid-state batteries, are non-wetting, therefore they need to be mixed with active materials and conductive agents to prepare a slurry during the preparation of the positive electrode. Due to particle obstruction, the connectivity between solid electrolytes is reduced, resulting in low ionic conductivity of the positive electrode, and the prepared battery can only be charged and discharged under low-rate conditions. With the improvement of the performance of electrical products, the demand for high-energy-density solid-state batteries is increasing, which also means that the corresponding positive electrode loading is becoming increasingly higher. The fluidity of solid electrolytes is much lower than that of liquid electrolytes, resulting in significant differences in lithium-ion transport during the positive electrode process. The thicker the positive electrode, the more difficult the lithium-ion transport near the current collector becomes, seriously affecting the rate performance and capacity utilization of the battery.

[0003] Therefore, how to comprehensively optimize the lithium-ion diffusion path of high-load electrode to achieve high rate and long cycle performance of battery has become a hot topic and key issue in the field of solid-state batteries. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art.

[0005] The first aspect of this application discloses a positive electrode sheet. According to an embodiment of this application, the positive electrode sheet includes: a current collector and a composite active layer, the composite active layer being disposed on at least one surface of the current collector, the composite active layer including an intermediate layer and a surrounding layer disposed around the intermediate layer, the conductivity of the surrounding layer being greater than the conductivity of the intermediate layer. The positive electrode sheet according to the embodiment of this application, by making the conductivity at the periphery of the positive electrode sheet higher than that at the center, can solve the problem of slower lithium-ion diffusion at the periphery of the positive electrode sheet due to uneven heat distribution, thereby improving battery capacity utilization and cycle performance.

[0006] According to embodiments of this application, the positive electrode sheet may also have the following additional technical features:

[0007] According to an embodiment of this application, the conductivity of the intermediate layer on the side away from the current collector is less than the conductivity of the intermediate layer on the side closer to the current collector, and the conductivity of the surrounding layer is greater than the conductivity of the intermediate layer on the side closer to the current collector.

[0008] According to an embodiment of this application, the intermediate layer includes: a first conductive active layer and a second conductive active layer, wherein the first conductive active layer is disposed on one surface of the current collector, and the second conductive active layer is disposed on the surface of the first conductive active layer away from the current collector; the surrounding layer is disposed at least around the second conductive active layer, and the surrounding layer is in contact with the second conductive active layer; wherein the conductivity of the first conductive active layer is greater than the conductivity of the second conductive active layer.

[0009] According to an embodiment of this application, the surrounding layer is disposed on the surface of the first conductivity active layer away from the current collector.

[0010] According to an embodiment of this application, the thickness of the surrounding layer is the same as the thickness of the second conductivity active layer.

[0011] According to an embodiment of this application, the orthographic projection of the second conductive active layer on the current collector overlaps with the orthographic projection of the first conductive active layer on the current collector, and the surrounding layer is further disposed around the first conductive active layer, and the surrounding layer is in contact with the first conductive active layer.

[0012] According to an embodiment of this application, the thickness of the surrounding layer is the same as the sum of the thicknesses of the first conductive active layer and the second conductive active layer.

[0013] According to an embodiment of this application, the thickness of the surrounding layer is 100μm-450μm.

[0014] According to an embodiment of this application, the thickness of the second conductivity active layer is 100μm-250μm.

[0015] According to an embodiment of this application, the thickness of the first conductivity active layer is 100μm-200μm.

[0016] According to an embodiment of this application, the thickness of the positive electrode sheet is 206μm-465μm.

[0017] According to an embodiment of this application, the area ratio of the surrounding layer to the first conductive active layer is (10-40):100.

[0018] According to an embodiment of this application, the area ratio of the surrounding layer to the first conductive active layer is (15-25):100.

[0019] According to an embodiment of this application, the area ratio of the surrounding layer to the first conductive active layer is (10-40):(90-60).

[0020] According to an embodiment of this application, the area ratio of the surrounding layer to the first conductive active layer is (10-20):(90-80).

[0021] According to an embodiment of this application, the first conductivity active layer includes a first active material, a first conductive agent, a first binder, and a first solid electrolyte.

[0022] According to an embodiment of this application, the second conductivity active layer includes a second active material, a second conductive agent, a second binder, and a second solid electrolyte.

[0023] According to an embodiment of this application, the surrounding layer includes a third active material, a third conductive agent, a third binder, and a third solid electrolyte.

[0024] According to an embodiment of this application, the conductivity of the third solid electrolyte is greater than that of the first solid electrolyte, and the conductivity of the first solid electrolyte is greater than that of the second solid electrolyte.

[0025] According to an embodiment of this application, the mass ratio of the first active material, the first conductive agent, the first binder and the first solid electrolyte is (60-90):(1-10):(0-3):(0-30).

[0026] According to an embodiment of this application, the mass ratio of the second active material, the second conductive agent, the second binder and the second solid electrolyte is (60-90):(1-10):(0-3):(0-30).

[0027] According to an embodiment of this application, the mass ratio of the third active material, the third conductive agent, the third binder and the third solid electrolyte is (60-90):(1-10):(0-3):(0-30).

[0028] According to embodiments of this application, the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each independently include at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte, and satisfy at least one of the following conditions: the D of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles... 50 The thicknesses are 0.5 μm to 50 μm, respectively; the polymer solid electrolyte accounts for 10% to 100% of the weight of the third solid electrolyte.

[0029] In a second aspect of this application, a solid-state battery is proposed. According to an embodiment of this application, the solid-state battery includes the positive electrode described in the first aspect.

[0030] In a third aspect, this application proposes an electrical device. According to an embodiment of this application, the electrical device includes the solid-state battery described in the second aspect.

[0031] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0032] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0033] Figure 1 This is a three-dimensional schematic diagram of the first structure of the positive electrode sheet according to an embodiment of this application;

[0034] Figure 2 This is a schematic cross-sectional view of the first structure of the positive electrode sheet according to an embodiment of this application;

[0035] Figure 3 This is a three-dimensional schematic diagram of a second structure of the positive electrode sheet according to an embodiment of this application;

[0036] Figure 4 This is a schematic cross-sectional view of a second structure of the positive electrode sheet according to an embodiment of this application;

[0037] Reference numerals: 100: Current collector; 200: First conductivity active layer; 300: Second conductivity active layer; 400: Surrounding layer. Detailed Implementation

[0038] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0039] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0040] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0041] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0042] Commercial lithium-ion batteries use organic liquid electrolytes, which pose risks of leakage and explosion. Solid-state electrolytes, due to their non-flammable properties, greatly improve battery safety. Therefore, all-solid-state lithium batteries, which use solid electrolytes instead of liquid electrolytes, have gained increasing attention in recent years.

[0043] For batteries, the key to improving energy density lies in increasing the loading of active materials in the electrodes. However, as the loading and thickness of the positive electrode increase, the transport of lithium ions and electrons is more severely restricted, and severe polarization occurs due to the significant increase in charge transport distance. Because the heat generated during battery charging and discharging cannot be evenly distributed across the entire positive electrode in a timely manner, the temperature in the center of the positive electrode is higher than that around the periphery, resulting in a slower lithium ion transport rate and higher polarization around the periphery, leading to severe electrode degradation after long cycles.

[0044] To address these issues, existing technologies primarily focus on two aspects. One is the modification of the cathode material, involving coating the surface of the active material with materials exhibiting high ionic conductivity or doping heteroatoms into the active material to optimize lithium-ion transport at the interface. However, the coating / doping process is complex, and the coating / doping amount is uncontrollable, leading to significant local differences in ionic conductivity. The other aspect is the optimization of the formulation, improving the diffusion mechanism of lithium ions within the active material, electrolyte, and conductive agent by adjusting their composition and proportions. However, the degree of improvement in ionic conductivity is limited.

[0045] In view of this, this application proposes a positive electrode sheet. According to an embodiment of this application, the positive electrode sheet includes: a current collector and a composite active layer, the composite active layer being disposed on at least one surface of the current collector, the composite active layer including an intermediate layer and a surrounding layer disposed around the intermediate layer, the conductivity of the surrounding layer being greater than the conductivity of the intermediate layer. The positive electrode sheet according to the embodiment of this application, by making the conductivity at the periphery of the positive electrode sheet greater than that at the center, can solve the problem of slower lithium-ion diffusion at the periphery of the positive electrode sheet due to uneven heat distribution compared to the center, thereby improving battery capacity utilization and cycle performance.

[0046] According to an embodiment of this application, the conductivity of the intermediate layer on the side away from the current collector is less than the conductivity of the intermediate layer on the side closer to the current collector, and the conductivity of the surrounding layer is greater than the conductivity of the intermediate layer on the side closer to the current collector. By making the conductivity of the intermediate layer on the side away from the current collector less than the conductivity of the intermediate layer on the side closer to the current collector, a gradient of increasing ion conductivity can be formed in the middle of the positive electrode sheet. This can improve the utilization rate of the active material, increase capacity, balance charge distribution, reduce polarization, optimize the lithium-ion transport path, and thus improve the rate performance of the battery.

[0047] It should be noted that the positional relationship between the intermediate layer and the surrounding layer mentioned above is defined for the same side of the current collector, and the above definition also applies to the other side.

[0048] According to an embodiment of this application, the intermediate layer includes: a first conductive active layer and a second conductive active layer, wherein the first conductive active layer is disposed on one surface of the current collector; the second conductive active layer is disposed on the surface of the first conductive active layer away from the current collector; the surrounding layer is disposed at least around the second conductive active layer, and the surrounding layer is in contact with the second conductive active layer; wherein the conductivity of the first conductive active layer is greater than the conductivity of the second conductive active layer.

[0049] According to the embodiments of this application, the positive electrode sheet achieves the highest conductivity around the periphery by making the conductivity of the surrounding layer greater than that of the intermediate layer. This solves the problem of slower lithium-ion diffusion around the periphery compared to the center due to uneven heat distribution, thereby improving battery capacity and cycle performance. Furthermore, the conductivity of the first conductive active layer is greater than that of the second conductive active layer. By placing the second conductive active layer on the surface of the first conductive active layer away from the current collector, the conductivity in the center of the positive electrode sheet increases from the second conductive active layer towards the current collector. This improves the utilization rate of the active material and increases capacity, balances the charge in the depth direction of the electrode sheet and reduces polarization, optimizes the lithium-ion transport path, and improves battery rate performance.

[0050] It should be noted that the positive electrode sheet of this application has two structures, which will be described in detail below.

[0051] The first structure of the positive electrode plate, see reference. Figure 1 and Figure 2The positive electrode includes a current collector 100, a first conductive active layer 200, a second conductive active layer 300, and a surrounding layer 400. The first conductive active layer 200 is disposed on one surface of the current collector 100. The second conductive active layer 300 and the surrounding layer 400 are disposed on the surface of the first conductive active layer 200 away from the current collector 100. The surrounding layer 400 surrounds the second conductive active layer 300 and is in contact with it. Therefore, this structure creates an increasing gradient of ionic conductivity in the central part of the positive electrode from the second conductive active layer 300 towards the current collector 100, which improves the utilization rate of the active material, increases capacity, reduces polarization, and enhances battery rate performance. Furthermore, the highest conductivity is found around the perimeter of the positive electrode, addressing the issue of slower lithium-ion diffusion around the perimeter due to uneven heat distribution, further improving battery capacity and cycle performance.

[0052] In some embodiments of this application, in a first structure, the thickness of the surrounding layer is the same as the thickness of the second conductive active layer. Therefore, the manufacturing process can be simplified, structural consistency can be ensured, and product quality can be more easily controlled during production.

[0053] In some embodiments of this application, in the first structure, the thickness of the second conductive active layer is 100 μm-250 μm. For example, it can be 100 μm, 150 μm, 200 μm, or 250 μm, or any range of the above values. Therefore, a thickness of the second conductive active layer within the above range ensures sufficient active material is provided, increasing the energy storage capacity of the battery, while reducing electrode cracking and polarization surges.

[0054] In some embodiments of this application, in the first structure, the thickness of the first conductive active layer is 100μm-200μm. For example, it can be 100μm, 150μm, or 200μm, or any range of the above values. Therefore, a thickness of the first conductive active layer within the above range is beneficial for structural stability and improving its peel force with the current collector, thereby increasing the current collection efficiency of the current collector, reducing internal resistance, and increasing the power density of the battery. At the same time, it makes the lithium ion diffusion distance shorter, which can reduce polarization and thus maintain a lower overpotential during high-rate charge and discharge.

[0055] In some embodiments of this application, in the first structure, the thickness of the surrounding layer is 100μm-250μm. For example, it can be 100μm, 150μm, 200μm, or 250μm, or any range of the above values. Therefore, with the surrounding layer within the above range, it can ensure stable drying of the surrounding layer, while providing sufficient active material to increase the energy storage capacity of the battery and ensure that ions can effectively diffuse during battery charging and discharging.

[0056] In some embodiments of this application, in the first structure, the thickness of the positive electrode sheet is 206μm-465μm. For example, it can be 206μm, 250μm, 305μm, 350μm, 380μm, 395μm, 420μm, 465μm, etc., or it can be any range of the above values.

[0057] In some embodiments of this application, in a first structure, the area ratio of the surrounding layer to the first conductive active layer is (10-40):100. For example, it can be 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, or 40:100, or any range of the above values. In some embodiments of this application, the area ratio of the surrounding layer to the first conductive active layer is (15-25):100. Therefore, with the area ratio of the surrounding layer to the first conductive active layer within the above range, the surrounding layer can more completely cover the area with low ionic conductivity due to thermal diffusion, while reducing the problems of numerous internal voids, cracking, and material shedding in the positive electrode sheet, as well as the probability of a large number of irreversible cracks forming internally after long cycling.

[0058] It should be noted that in the first structure, both the second conductive active layer and the surrounding layer are located on the surface of the first conductive active layer away from the current collector; that is, the area of ​​the first conductive active layer is the sum of the areas of the second conductive active layer and the surrounding layer. Once the area ratio of the surrounding layer to the first conductive active layer is defined, the area ratio of the second conductive active layer to the first conductive active layer can be obtained through calculation.

[0059] The second structure of the positive electrode plate, see reference. Figure 3 and Figure 4The positive electrode includes a current collector 100, a first conductive active layer 200, a second conductive active layer 300, and a surrounding layer 400. The first conductive active layer 200 is disposed on one surface of the current collector 100, and the second conductive active layer 300 is disposed on the surface of the first conductive active layer 200 away from the current collector 100. The orthographic projection of the second conductive active layer 300 onto the current collector 100 overlaps with the orthographic projection of the first conductive active layer 300 onto the current collector 100. The surrounding layer 400 is disposed around the first conductive active layer 200 and the second conductive active layer 300, and is in contact with both the first conductive active layer 200 and the second conductive active layer 300. Therefore, this structure enables a gradient of increasing ionic conductivity to be formed in the middle of the positive electrode from the second conductive active layer 300 to the current collector 100, which can improve the utilization rate of the active material and increase capacity, reduce polarization, and improve the rate performance of the battery. At the same time, the conductivity is highest at the periphery of the positive electrode, which can solve the problem that the lithium ion diffusion rate at the periphery of the positive electrode is slower than that in the middle of the positive electrode due to uneven heat distribution, further improving the battery capacity and cycle performance.

[0060] In some embodiments of this application, in the second structure, the thickness of the surrounding layer is the same as the sum of the thicknesses of the first and second conductive active layers. This helps to enhance the structural integrity of the positive electrode, reduce stress concentration caused by inconsistent thicknesses, and simultaneously simplify the manufacturing process while ensuring structural consistency.

[0061] In some embodiments of this application, in the second structure, the thickness of the second conductive active layer is 100 μm-250 μm. For example, it can be 100 μm, 150 μm, 200 μm, or 250 μm, or any range of the above values. Therefore, a thickness of the second conductive active layer within the above range ensures sufficient active material is provided, increasing the energy storage capacity of the battery, while reducing electrode cracking and polarization surges.

[0062] In some embodiments of this application, in the second structure, the thickness of the first conductive active layer is 100μm-200μm. For example, it can be 100μm, 150μm, or 200μm, or any range of the above values. Therefore, a thickness of the first conductive active layer within the above range is beneficial for structural stability and improving its peel force with the current collector, thereby increasing the current collection efficiency of the current collector, reducing internal resistance, and increasing the power density of the battery. At the same time, it makes the lithium ion diffusion distance shorter, which can reduce polarization and thus maintain a lower overpotential during high-rate charge and discharge.

[0063] In some embodiments of this application, in the second structure, the thickness of the surrounding layer is 200μm-450μm. For example, it can be 200μm, 250μm, 300μm, 350μm, 400μm, or 450μm, or any range of the above values. Therefore, with the surrounding layer within the above range, stable drying of the surrounding layer can be ensured, while providing sufficient active material to increase the energy storage capacity of the battery and ensure that ions can effectively diffuse during battery charging and discharging.

[0064] In some embodiments of this application, in the second structure, the thickness of the positive electrode sheet is 206μm-465μm. For example, it can be 206μm, 250μm, 305μm, 350μm, 380μm, 395μm, 420μm, 465μm, etc., or it can be any range of the above values.

[0065] In some embodiments of this application, in the second structure, the area ratio of the surrounding layer to the first conductive active layer is (10-40):(90-60). For example, it can be 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, or 40:60, or any range of the above values. In some embodiments of this application, the area ratio of the surrounding layer to the first conductive active layer is (10-20):(90-80). Therefore, with the area ratio of the surrounding layer to the first conductive active layer within the above range, the surrounding layer can more completely cover the area with low ionic conductivity due to thermal diffusion, while reducing the problems of numerous internal voids, cracking, and material shedding in the positive electrode sheet, as well as the probability of a large number of irreversible cracks forming internally after long cycles.

[0066] It should be noted that in the second structure, the orthographic projection of the second conductivity active layer on the current collector overlaps with the orthographic projection of the first conductivity active layer on the current collector, that is, the area of ​​the second conductivity active layer is the same as the area of ​​the first conductivity active layer. When the area ratio of the first conductivity active layer to the surrounding layer is defined, the area ratio of the second conductivity active layer to the surrounding layer can also be obtained.

[0067] In some embodiments of this application, the current collector is a conventional component in the art. Those skilled in the art can select the thickness of the current collector according to actual needs. For example, the current collector thickness used in this application is 6-15 μm. For example, it can be 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 15 μm, or it can be any range of the above values.

[0068] In some embodiments of this application, the thickness of the current collector, the thickness of the first conductive active layer, the thickness of the second conductive active layer, and the thickness of the surrounding layer can be measured using a micrometer.

[0069] In some embodiments of this application, the first conductive active layer comprises a first active material, a first conductive agent, a first binder, and a first solid electrolyte. The mass ratio of the first active material, the first conductive agent, the first binder, and the first solid electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or any range of the above values. Therefore, the first conductive active layer prepared using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode.

[0070] In some embodiments of this application, the second conductive active layer comprises a second active material, a second conductive agent, a second binder, and a second solid electrolyte. The mass ratio of the second active material, the second conductive agent, the second binder, and the second solid electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or any range of the above values. Therefore, the second conductive active layer prepared using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode.

[0071] In some embodiments of this application, the surrounding layer comprises a third active material, a third conductive agent, a third binder, and a third solid electrolyte. The mass ratio of the third active material, the third conductive agent, the third binder, and the third solid electrolyte is (60-90):(1-10):(0-3):(0-30). For example, it can be 60:5:2:10, 65:6:1:30, 70:8:3:7, 75:10:2:20, 82:2:2:14, 90:1:3:25, or any range of the above values. Therefore, the surrounding layer prepared using the above ratio has good electronic conductivity and high energy density, while maintaining the mechanical stability and structural integrity of the positive electrode.

[0072] In the prior art, the active material near the current collector cannot fully participate in the electrochemical reaction, so the capacity cannot be fully exerted. This exacerbates the instability of the electrode structure and accelerates the deterioration of the electrochemical-mechanical coupling of the electrode. In addition, the solid electrolyte in the positive electrode directly affects the ion transport and stability in the positive electrode, and is an important factor affecting the battery capacity exertion and retention rate. Therefore, in this application, by regulating the conductivity of the solid electrolyte at different positions in the active layer, the lithium ion transport path is optimized, thereby improving the battery rate performance. That is, in this application, the conductivity of the third solid electrolyte is greater than that of the first solid electrolyte, and the conductivity of the first solid electrolyte is greater than that of the second solid electrolyte. Thereby, the ionic conductivity of the surrounding layer in the active layer can be made greater than the ionic conductivity of the first conductivity active layer, and the ionic conductivity of the first conductivity active layer is greater than the ionic conductivity of the second conductivity active layer.

[0073] It should be noted that the mass ratios of the first active material, the first conductive agent, the first binder, and the first solid electrolyte in the first conductivity active layer, the mass ratios of the second active material, the second conductive agent, the second binder, and the second solid electrolyte in the second conductivity active layer, and the mass ratios of the third active material, the third conductive agent, the third binder, and the third solid electrolyte in the surrounding layer can be the same or different, as long as they can satisfy that the ionic conductivity of the surrounding layer is greater than the ionic conductivity of the first conductivity active layer, and the ionic conductivity of the first conductivity active layer is greater than the ionic conductivity of the second conductivity active layer.

[0074] In some embodiments of this application, the first active material, the second active material, and the third active material are conventional materials in the art. Those skilled in the art can respectively select the specific types of the first active material, the second active material, and the third active material according to the actual situation. For example, lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium manganese phosphate (LiMnPO4), lithium nickel phosphate (LiNiPO4), lithium manganate (LiMnO2), binary material LiNi x A (1-x) O2 (where A is selected from one of Co and Mn, 0 < x < 1), ternary material LiNimBnC (1-m-n) O2 (where B and C are independently selected from at least one of Co, Al, and Mn, and B and C are different, 0 < m < 1, 0 < n < 1).

[0075] In some embodiments of this application, the first conductive agent, the second conductive agent, and the third conductive agent are conventional components in the art. Those skilled in the art can select the specific types of the first conductive agent, the second conductive agent, and the third conductive agent according to actual conditions. For example, at least one of acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotubes, and Ketjen black can be used independently.

[0076] In some embodiments of this application, the first adhesive, the second adhesive, and the third adhesive are conventional materials in the art. Those skilled in the art can select the specific types of the first adhesive, the second adhesive, and the third adhesive according to actual needs. For example, at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyethylene oxide (PEO), and ethylene oxide-propylene oxide copolymer (PEO-PO) can be used independently.

[0077] In some embodiments of this application, the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte are conventional materials in the art. Those skilled in the art can select the specific types of the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte according to the actual situation. For example, at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte can be used independently.

[0078] It should be noted that the differences in ionic conductivity between the first, second, and surrounding layers of this application are due to the differences in ionic conductivity of the solid electrolytes in each layer. The first, second, and third solid electrolytes can be the same or different. When the first, second, and third solid electrolytes are the same, the ionic conductivity of the solid electrolytes can be controlled by adjusting factors such as particle size and composition, as long as the ionic conductivity of the surrounding layer is greater than that of the first active layer, and the ionic conductivity of the first active layer is greater than that of the second active layer.

[0079] In some embodiments of this application, the D50 of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles are all between 0.5 μm and 50 μm. For example, the D50 can be 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm, or any range of the above values. Therefore, by making the D50 of the particles within the above range, the ion conduction channels of the solid electrolyte can be increased, improving ion mobility and overall ionic conductivity. Simultaneously, the contact area between the solid electrolyte and the active material can be increased, reducing interfacial impedance, thereby improving the charge-discharge performance of the electrode. In some embodiments of this application, the D50 of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles are all between 0.5 μm and 10 μm. In some embodiments of this application, the D50 of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles are all between 0.5 μm and 5 μm.

[0080] In this application, the volume average particle size D50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%. For example, the volume average particle size D50 test method can refer to the standard GB / T 19077-2016 and be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000).

[0081] In some embodiments of this application, the oxide solid electrolyte is a conventional electrolyte in the art. Those skilled in the art can select the specific type of oxide solid electrolyte according to actual needs. For example, it can be AB2(MO4)3 (A includes alkali metals, B includes Ge, Zr, Ti or V, and M includes i, Mo or P), Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP), Li 0.5 La 0.5 TiO3(LLTO), Li5La3M2O 12 (M includes Ta, Nb, or Zr), Li x M 1-y A y S4 (M includes Si or Ge, A includes P, Al, Zn, Ga or Sb) and LiAlO2 are at least one of them.

[0082] In some embodiments of this application, the sulfide solid electrolyte is a conventional electrolyte in the art. Those skilled in the art can select the specific type of sulfide solid electrolyte according to actual needs. For example, it can be Li6PS5Br or Li7P3S. 11 Li 10 GeP2S 12Li6PS5Cl, Li 6+x P 1-x Ge x S5I (x = 0~1), Li6PS5Cl x Br 1-x (x=0~1), Li6PS5Cl x Br 1-x (x=0~1), Li5PS4X2 (X includes Cl, Br or I), xLi2S·(100-x)P2S5 (60≤x≤80), Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 Li 10 MP2S 12 (M includes Si, Ge or Sn) and at least one of Li5PS4X2 (X includes Cl, Br or I).

[0083] In some embodiments of this application, the halide solid electrolyte is a conventional electrolyte in the art. Those skilled in the art can select the specific type of halide solid electrolyte according to actual needs. For example, it can be Li3ErX6 (X includes Cl, Br or I), Li3LaI6, Li3LuCl6, or Li3InBr. 6-x Cl x (x≤4), Li3InBr3Cl3, Li3InBr6, Li3InCl6, LiInBr4, CsSnCl3, Li x ScCl 3+x (x = 0–0.6), Li3ScX6 (X includes Cl, Br, or I), Li 3-x Er 1-x Zr x Cl6 (x≤0.6), Li 3-x Y 1-x Zr x Cl6 (x≤0.6), Li3YX6 (X includes Cl, Br or I), Li3Y 1-x In x At least one of Cl6 (0≤x<1).

[0084] In some embodiments of this application, the polymer solid electrolyte includes at least one of a polymer backbone, a lithium salt, and a plasticizer.

[0085] In some embodiments of this application, the mass ratio of the polymer backbone, lithium salt, and plasticizer is (30-60):(10-50):(0-50). For example, it can be 30:10:25, 35:25:40, 40:20:30, 45:10:20, 50:25:10, 55:30:40, or 60:45:50, or any range of the above values. Therefore, the polymer solid electrolyte can possess excellent ion transport performance, good flexibility, and film-forming properties.

[0086] In some embodiments of this application, the polymer backbone is a conventional material in the art. Those skilled in the art can select the specific type of polymer backbone according to actual needs. For example, it can be at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polypropylene carbonate (PPC), polyethylene oxide (PEO), and ethylene oxide-propylene oxide copolymer (PEO-PO).

[0087] In some embodiments of this application, the molecular weight of the polymer backbone is 10,000-600,000 g / mol. For example, it can be 10,000 g / mol, 50,000 g / mol, 100,000 g / mol, 200,000 g / mol, 300,000 g / mol, 400,000 g / mol, 500,000 g / mol, or 600,000 g / mol, or any range of the above values. Therefore, by keeping the molecular weight of the polymer backbone within the above range, the polymer solid electrolyte helps to possess better tensile strength and toughness.

[0088] In some embodiments of this application, the lithium salt is a conventional material in the art. Those skilled in the art can select the specific type of lithium salt according to the actual situation. For example, it can be one or more of organic lithium salts and inorganic lithium salts, such as LiPF6, LiBF4, LiClO4, LiAsF6, LiTFSI, LiFSI, LiBOB, LiDFOB, and LiTFOP.

[0089] In some embodiments of this application, the plasticizer is a conventional material in the art. Those skilled in the art can select the specific type of plasticizer according to actual needs. For example, it can be at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, succinate (SN), and polyethylene glycol dimethyl ether with a molecular weight of less than 1000.

[0090] In some embodiments of this application, the polymer solid electrolyte in the third solid electrolyte comprises 10% to 100% by weight. For example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, or any range of the above values. Therefore, by ensuring the weight percentage of the polymer solid electrolyte is within the above range, it helps the surrounding layer to have better stability and improves the overall robustness.

[0091] In some embodiments of this application, the current collector 100 is a conventional component in the art. Those skilled in the art can select the specific type of current collector 100 according to actual needs, such as aluminum foil, aluminum foam, carbon-coated aluminum foil, carbon mesh, or carbon cloth.

[0092] In some embodiments of this application, the ionic conductivity testing methods for each active layer are as follows: Taking the first conductive active layer as an example, the positive electrode slurry of the first conductive active layer is uniformly coated onto one surface of polyester resin (PET) material using a scraping method. After heating and baking to remove the solvent, the positive electrode film of the first conductive active layer is obtained. This positive electrode film is coated on the release surface of the PET and peeled off when assembling the coin cell. The coin cell is fabricated using a steel sheet-electrolyte-positive electrode film-electrolyte-steel sheet structure and kept at 50-80℃ for 20-40 minutes to promote interface fusion. Finally, the ionic conductivity of the positive electrode sheet is tested using an electrochemical workstation-EIS program, and the calculation formula is as follows:

[0093] σ=L / (SR)

[0094] Where σ represents the ionic conductivity of the positive electrode, L represents the thickness of the positive electrode, S represents the area of ​​the steel sheet, and R represents the resistance of the positive electrode.

[0095] In some embodiments of this application, the method for testing the ionic conductivity of the composite active layer on the positive electrode sheet is as follows: Three conductive active layers (a surrounding layer, a first conductive active layer, and a second conductive active layer) are uniformly coated onto one surface of a PET material using a special coating process. The composite active layer is then peeled off from the release surface of the PET. The ionic conductivity of the composite active layer is tested using a single-layer method.

[0096] The second aspect of this application discloses a solid-state battery, the battery comprising the positive electrode sheet described in the first aspect of this application.

[0097] In some embodiments of this application, the solid-state battery includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the solid-state battery, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode.

[0098] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one side surface of the negative current collector, the negative active layer comprising a negative active material, a conductive agent and a binder.

[0099] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0100] In some embodiments of this application, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. Silicon-based materials may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide compounds, and tin alloys.

[0101] In some embodiments of this application, the adhesive may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0102] In some embodiments of this application, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments of this application, the negative electrode active layer may optionally include other additives, such as thickeners, and plasticizers including at least one selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, 1,3-dioxolane, 1,4-dioxane, propylene carbonate, ethylene carbonate, diethyl carbonate or dimethyl carbonate, succinate, and adiponitrile.

[0104] In some embodiments of this application, the negative electrode comprises lithium metal and / or a lithium metal alloy.

[0105] In some embodiments of this application, the electrolyte, as described above, includes at least one of oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, and polymer solid electrolytes.

[0106] In some embodiments of this application, the solid-state battery may include an outer packaging. This outer packaging is used to encapsulate the positive electrode, the negative electrode, and the electrolyte.

[0107] In some embodiments of this application, the outer packaging may include a shell and a cover. The shell may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover plate can be placed over the opening to close the receiving cavity.

[0108] In some embodiments of this application, the outer packaging of the solid-state battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0109] Solid-state batteries can also be packaged in a pouch, such as a soft-pack. The material of the pouch can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0110] The solid-state battery of this application may be in the form of a solid-state battery cell, a solid-state battery module, or a solid-state battery pack. In some embodiments, solid-state battery cells may be assembled into solid-state battery modules, and the number of solid-state battery cells contained in a solid-state battery module may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the solid-state battery module. In some embodiments, solid-state battery modules may also be assembled into solid-state battery packs, and the number of battery modules contained in a solid-state battery pack may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the solid-state battery pack.

[0111] A third aspect of this application discloses an electrical device. According to an embodiment of this application, the electrical device includes the solid-state battery described in the second aspect above. Therefore, the electrical device of this application has high-efficiency energy output, as well as excellent service life and safety performance.

[0112] Solid-state battery cells, solid-state battery modules, and solid-state battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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.

[0113] As an electrical device, solid-state battery cells, solid-state battery modules, or solid-state battery packs can be selected according to their usage requirements.

[0114] As one example, the electrical device can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device for solid-state batteries, solid-state battery packs or solid-state battery modules can be used.

[0115] Another example of the device could be a mobile phone, tablet computer, laptop computer, etc. Such devices typically require a thin and light design and can use solid-state battery cells as a power source.

[0116] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0117] Example 1

[0118] The structure of the positive electrode is as follows: Figure 1 and Figure 2 As shown, LiNi is selected. 0.8 Co 0.1 Mn 0.1 O2 is the active material, Super P is the conductive agent, PVDF is the binder, LATP is the oxide solid electrolyte, Li6PS5Cl is the sulfide solid electrolyte, PEO+LiTFSI+SN(SPE) is the polymer solid electrolyte, and 8μm aluminum foil is the current collector.

[0119] The active material, conductive agent, binder, and solid electrolyte are in the same mass ratio in the first conductive active layer, the second conductive active layer, and the surrounding layer.

[0120] The mass ratio of the active material, conductive agent, binder and solid electrolyte is 82:2:2:14.

[0121] The mass ratio of PEO, LiTFSI, and SN in the SPE is 50:25:25.

[0122] The positive electrode sheet has the first structure, in which:

[0123] The first conductive active layer has a thickness of 120 μm, and the solid electrolyte is Li6PS5Cl (abbreviated as S111), with a D50 of 2 μm.

[0124] The second conductive active layer has a thickness of 150 μm, and the solid electrolyte is Li6PS5Cl (abbreviated as S121), with a D50 of 1 μm.

[0125] The surrounding layer is 150 μm thick, and the solid electrolytes are Li6PS5Cl (abbreviated as S131) ​​and SPE (abbreviated as P132). The D50 of S131 is 3 μm, the molecular weight of PEO in P132 is 200000 g / mol, and the mass ratio of S131 to P132 is 9:1.

[0126] The area ratio of the surrounding layer to the first conductive active layer is 20:100.

[0127] Example 2

[0128] The structure and raw materials of the positive electrode sheet are the same as in Example 1, and the mass ratio of active material, conductive agent, binder and solid electrolyte is the same as in Example 1.

[0129] The first conductivity active layer has a thickness of 120 μm, and the solid electrolytes are Li6PS5Cl (abbreviated as S211) and LATP (abbreviated as S212). The D50 of S211 is 2 μm, and the D50 of S212 is 10 μm; the mass ratio of S211 to S212 is 9:1.

[0130] The second conductivity active layer has a thickness of 150 μm, and the solid electrolytes are Li6PS5Cl (abbreviated as S221) and LATP (abbreviated as S222). The D50 of S221 is 1 μm, and the D50 of S222 is 5 μm; the mass ratio of S211 to S212 is 8:2.

[0131] The surrounding layer is 150 μm thick, and the solid electrolytes are Li6PS5Cl (abbreviated as S231) and SPE (abbreviated as S232). The D50 of S131 is 3 μm, the molecular weight of PEO in S232 is 200000 g / mol, and the mass ratio of S131 to S232 is 9:1.

[0132] The area ratio of the surrounding layer to the first conductive active layer is 20:100.

[0133] Example 3

[0134] The structure and raw materials of the positive electrode sheet are the same as in Example 1. The mass ratio of active material, conductive agent, binder and solid electrolyte is the same as in Example 1, that is, the mass ratio of active material, conductive agent, binder and solid electrolyte is 82:2:2:14.

[0135] The first conductive active layer has a thickness of 120 μm, and the solid electrolytes are Li6PS5Cl (abbreviated as S311) and SPE (abbreviated as S312). The D50 of S311 is 2 μm, and the molecular weight of PEO in S312 is 100000 g / mol; the mass ratio of S311 to S312 is 9:1.

[0136] The second conductive active layer has a thickness of 150 μm, and the solid electrolytes are Li6PS5Cl (referred to as S321) and SPE (referred to as S322). The D50 of S321 is 1 μm, and the molecular weight of PEO in S322 is 100,000 g / mol; the mass ratio of S321 to S322 is 8:2.

[0137] The surrounding layer is 150 μm thick, and the solid electrolytes are Li6PS5Cl (abbreviated as S331) and SPE (abbreviated as S332). The D50 of S331 is 3 μm, and the molecular weight of PEO in S332 is 200,000 g / mol; the mass ratio of S331 to S332 is 9:1.

[0138] The area ratio of the surrounding layer to the first conductive active layer is 20:100.

[0139] Example 4

[0140] The structure and composition of the positive electrode are the same as in Example 3, except that the area ratio of the surrounding layer to the first conductivity active layer is 10:100.

[0141] Example 5

[0142] The structure and composition of the positive electrode are the same as in Example 3, except that the area ratio of the surrounding layer to the first conductivity active layer is 40:100.

[0143] Example 6

[0144] The composition of the positive electrode is the same as in Example 3, and the structure of the positive electrode is as follows: Figure 3 and Figure 4 As shown, this is the second structure.

[0145] The first conductive active layer has a thickness of 120 μm; the second conductive active layer has a thickness of 150 μm; and the surrounding layer has a thickness of 270 μm.

[0146] The area ratio of the surrounding layer to the first conductive active layer is 10:90.

[0147] Example 7

[0148] The structure and composition of the positive electrode are the same as in Example 6, except that the area ratio of the surrounding layer to the first conductivity active layer is 15:85.

[0149] Example 8

[0150] The structure and composition of the positive electrode are the same as in Example 6, except that the area ratio of the surrounding layer to the first conductivity active layer is 40:60.

[0151] Example 9

[0152] The structure and composition of the positive electrode are the same as in Example 3, and the area ratio of the active layers is the same as in Example 3, only the thickness of each active layer is different. The first conductivity active layer has a thickness of 100 μm; the second conductivity active layer has a thickness of 100 μm; and the surrounding layer has a thickness of 100 μm.

[0153] Example 10

[0154] The structure and composition of the positive electrode are the same as in Example 3, and the area ratio of the active layers is the same as in Example 3, only the thickness of each active layer is different. The first conductivity active layer has a thickness of 200 μm; the second conductivity active layer has a thickness of 250 μm; and the surrounding layer has a thickness of 250 μm.

[0155] Example 11

[0156] The structure and composition of the positive electrode are the same as in Example 6, and the area ratio of the active layers is the same as in Example 6, only the thickness of each active layer is different. The first conductivity active layer has a thickness of 100 μm; the second conductivity active layer has a thickness of 100 μm; and the surrounding layer has a thickness of 200 μm.

[0157] Example 12

[0158] The structure and composition of the positive electrode are the same as in Example 6, and the area ratio of the active layers is the same as in Example 6, only the thickness of each active layer is different. The first conductivity active layer has a thickness of 200 μm; the second conductivity active layer has a thickness of 250 μm; and the surrounding layer has a thickness of 450 μm.

[0159] Example 13

[0160] The specific implementation scheme is the same as in Example 1, except that the surrounding layer uses a single solid electrolyte, as detailed below:

[0161] The first conductive active layer has a thickness of 120 μm, and the solid electrolyte is Li6PS5Cl (abbreviated as S111), with a D50 of 2 μm.

[0162] The second conductive active layer has a thickness of 150 μm, and the solid electrolyte is Li6PS5Cl (abbreviated as S121), with a D50 of 1 μm.

[0163] The surrounding layer is 150 μm thick, and the solid electrolyte is Li6PS5Cl (abbreviated as S131). The D50 of S131 is 3 μm.

[0164] Example 14

[0165] The specific implementation scheme is the same as that in Example 1, except that it only contains a second conductivity active layer and a surrounding layer, as detailed below:

[0166] The second conductive active layer has a thickness of 150 μm, and the solid electrolyte is Li6PS5Cl (abbreviated as S121), with a D50 of 1 μm.

[0167] The surrounding layer is 150 μm thick, and the solid electrolytes are Li6PS5Cl (abbreviated as S131) ​​and SPE (abbreviated as P132). The D50 of S131 is 3 μm, the molecular weight of PEO in P132 is 200000 g / mol, and the mass ratio of S131 to P132 is 9:1.

[0168] The area ratio of the surrounding layer to the second conductive active layer is 20:80.

[0169] Comparative Example 1

[0170] The raw materials for the positive electrode are the same as those for the first conductivity active layer in Example 1, except that the positive electrode has only one active layer. The specific process is as follows:

[0171] LiNi was selected 0.8 Co 0.1 Mn 0.1 O2 is the active material, Super P is the conductive agent, PVDF is the binder, and Li6PS5Cl is the solid electrolyte. The active material, conductive agent, binder and solid electrolyte are mixed evenly in a mass ratio of 82:2:2:14. The slurry is then directly and evenly coated onto the current collector with a scraper and baked for a certain time to obtain a composite positive electrode sheet with a thickness of 270μm.

[0172] Comparative Example 2

[0173] The structure and raw materials of the positive electrode are the same as in Example 3. The difference lies in the type of solid electrolyte in the first conductivity active layer, the second conductivity active layer, and the surrounding layer, as well as the formulation of the positive electrode. These are the same as those in the first conductivity active layer of Example 3, as detailed below:

[0174] The first conductive active layer has a thickness of 120 μm, and the solid electrolytes are Li6PS5Cl (abbreviated as SD11) and SPE (abbreviated as SD12). The D50 of SD11 is 2 μm, and the molecular weight of PEO in SD12 is 100,000 g / mol; the mass ratio of SD11 to SD12 is 9:1.

[0175] The second conductive active layer has a thickness of 150 μm, and the solid electrolytes are Li6PS5Cl (abbreviated as SD21) and SPE (abbreviated as SD22). The D50 of SD21 is 2 μm, and the molecular weight of PEO in SD22 is 100,000 g / mol; the mass ratio of SD21 to SD22 is 9:1.

[0176] The surrounding layer is 150 μm thick, and the solid electrolytes are Li6PS5Cl (abbreviated as SD31) and SPE (abbreviated as SD32). The D50 of SD31 is 2 μm, and the molecular weight of PEO in SD32 is 100,000 g / mol; the mass ratio of SD31 to SD32 is 9:1.

[0177] The specific differences between Examples 1-12 are shown in Table 1.

[0178] Table 1

[0179]

[0180]

[0181]

[0182] I. Materials used in battery assembly:

[0183] The positive electrode is the positive electrode sheet obtained in this patent;

[0184] The solid electrolyte is Li6PS5Cl with a thickness of 40 μm, wherein the mass ratio of Li6PS5Cl to binder PVDF is 99:1.

[0185] The negative electrode coating layer is made of pure silicon material with a thickness of 25μm, and the mass ratio of pure silicon to binder PVDF is 96:4.

[0186] The negative electrode current collector is made of pure copper and has a thickness of 10μm.

[0187] II. Button cell assembly for testing ionic conductivity:

[0188] A coin cell casing (model 2025) and a 16mm diameter steel sheet were used. After ultrasonic removal of impurities using deionized water and ethanol, the casings were dried and ready for use. The battery was assembled sequentially: negative electrode casing, steel sheet, solid electrolyte, positive electrode film, solid electrolyte, steel sheet, and positive electrode casing. The assembled battery was sealed using a sealing machine at 700 PPa for 5 seconds. The prepared coin cell was then incubated at 60°C for 20 minutes to promote interfacial fusion. Finally, the ionic conductivity of the positive electrode was tested using an electrochemical workstation (EIS) program.

[0189] III. Assembly of Soft-Pack Batteries for Electrochemical Performance Testing

[0190] First, the positive and negative electrode plates are welded together with tabs; then, the pre-cut solid electrolyte sheet is transferred onto the negative electrode plate using a roller press; next, the positive electrode plates are neatly stacked on the surface of the solid electrolyte to form a sandwich structure; then, aluminum-plastic film is added for outer packaging, and the package is sealed under vacuum to obtain the soft-pack battery to be tested.

[0191] IV. Ionic Conductivity Testing Process and Procedure Setting

[0192] (1) Test environment preparation: Set the constant temperature oven to 25℃;

[0193] (2) Balancing battery temperature: Connect the test leads of the electrochemical workstation to the oven, place the battery to be tested into the oven, connect the electrochemical workstation, and start the test after the oven temperature and battery temperature have reached the test temperature and stabilized.

[0194] (3) EIS test program settings: Set the test frequency to 100kHz~50MHz; voltage protection range -10V~10V; disturbance voltage set to 5mV.

[0195] V. Ratio and Cyclic Testing Process and Program Settings

[0196] (1) Preparation before battery testing: Apply a restraining force of 20 MPa to the soft-pack battery using a self-made steel clamp;

[0197] (2) Test environment preparation: Set the constant temperature oven to 25℃;

[0198] (3) Balancing battery temperature: Connect the test lines of the Blue Battery Test Cabinet to the oven, put the battery to be tested into the oven, connect the Blue Battery Test Cabinet, and start the test after the oven temperature and battery temperature have reached the test temperature and stabilized.

[0199] (4) Rate test program setting: Set the upper and lower limits of the test voltage to 2.5V-4.2V. After the soft pack battery completes the capacity calibration, set the battery to complete one charge and discharge cycle under the program of 0.2C charging / 1C discharging according to the current value corresponding to the calibrated capacity, and record the battery overpotential data under the 1C discharge condition.

[0200] (5) Cyclic Test Program Setting: Set the upper and lower limits of the test voltage to 2.5V-4.2V. After the soft-pack battery completes capacity calibration, set the battery to perform a cyclic test under the program of 0.2C charging / 0.5C discharging according to the current value corresponding to the calibrated capacity. When the remaining capacity of the battery is 80% of the calibrated capacity, stop the test and record the corresponding number of cycles.

[0201] The specific test results are shown in Table 2:

[0202] Table 2

[0203]

[0204]

[0205] Comparing Examples 1-14 with Comparative Example 1, it can be seen that the structure of this application can effectively improve the ionic conductivity of the positive electrode, reduce polarization, and thus improve the battery rate and cycle performance. The ionic conductivity around the positive electrode is slightly higher than that in the middle, which can effectively avoid the problem of poor battery cycle performance caused by uneven lithium-ion transport rate due to thermal diffusion during battery charging and discharging.

[0206] Comparing Examples 1-14 with Comparative Example 2, it can be seen that the ionic conductivity of the positive electrode can only be effectively improved when the conductivity of the surrounding layer in the active layer is greater than that of the intermediate layer. Setting the conductivity at different positions of the active layer is the key to improving the ionic conductivity of the positive electrode, reducing polarization, and improving the battery rate and cycle performance.

[0207] As can be seen from Examples 1-3, the type of electrolyte has a significant impact on battery performance. Polymer electrolytes, due to their lower ionic conductivity, cause a slight decrease in the ionic conductivity of the positive electrode. However, their excellent processability and fluidity reduce the interfacial impedance within the positive electrode and between the positive electrode and the electrolyte, thereby improving the battery's cycle performance.

[0208] As can be seen from Examples 3-5 and Examples 6-8, the design structure of the positive electrode (the first structure or the second structure) has little impact on the performance of the electrode and the battery; the area ratio of the surrounding layer and the first conductive active layer has a significant impact on the performance of the electrode and the battery, and too low or too high ratios will lead to a decrease in the cycle performance of the electrode.

[0209] As can be seen from the comparison of Examples 3 and 9-10, and Examples 6 and 11-12, the loading of the positive electrode (i.e., the thickness of the active layer) has a significant impact on the rate capability and cycle performance of the battery. If the loading is too low, the battery energy density is low, making it unsuitable for mass production; if the loading is too high, the migration of lithium ions from the positive electrode surface to the interior of the electrode increases significantly, leading to increased polarization and increased battery capacity decay.

[0210] A comparison of Examples 1 and 13 shows that the use of a composite electrolyte containing a polymer electrolyte in the surrounding layer can effectively bond the gaps between it and the first and second conductivity active layers, thereby improving the cycle performance of the battery.

[0211] A comparison of Examples 1 and 14 shows that designing a gradient in conductivity on the current collector surface can effectively optimize the overall ion transport path of the electrode.

[0212] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A positive electrode plate, characterized in that, include: A current collector and a composite active layer, the composite active layer being disposed on at least one surface of the current collector, the composite active layer comprising an intermediate layer and a surrounding layer disposed around the intermediate layer, the conductivity of the surrounding layer being greater than that of the intermediate layer.

2. The positive electrode sheet according to claim 1, characterized in that, The conductivity of the intermediate layer on the side away from the current collector is less than the conductivity of the intermediate layer on the side closer to the current collector, and the conductivity of the surrounding layer is greater than the conductivity of the intermediate layer on the side closer to the current collector.

3. The positive electrode sheet according to claim 2, characterized in that, The intermediate layer includes: a first conductive active layer and a second conductive active layer, wherein the first conductive active layer is disposed on one surface of the current collector; and the second conductive active layer is disposed on the surface of the first conductive active layer away from the current collector. The surrounding layer is disposed at least around the periphery of the second conductive active layer, and the surrounding layer is in contact with the second conductive active layer; The conductivity of the first conductivity active layer is greater than that of the second conductivity active layer.

4. The positive electrode sheet according to claim 3, characterized in that, The surrounding layer is disposed on the surface of the first conductivity active layer away from the current collector.

5. The positive electrode sheet according to claim 4, characterized in that, The thickness of the surrounding layer is the same as the thickness of the second conductivity active layer.

6. The positive electrode sheet according to claim 3, characterized in that, The orthographic projection of the second conductive active layer on the current collector overlaps with the orthographic projection of the first conductive active layer on the current collector. The surrounding layer is further disposed around the first conductive active layer, and the surrounding layer is in contact with the first conductive active layer.

7. The positive electrode sheet according to claim 6, characterized in that, The thickness of the surrounding layer is the same as the sum of the thicknesses of the first conductive active layer and the second conductive active layer.

8. The positive electrode sheet according to any one of claims 3-7, characterized in that, The thickness of the surrounding layer is 100μm-450μm; And / or, the thickness of the second conductive active layer is 100 μm-250 μm; And / or, the thickness of the first conductive active layer is 100μm-200μm.

9. The positive electrode sheet according to any one of claims 8, characterized in that, The thickness of the positive electrode sheet is 206μm-465μm.

10. The positive electrode sheet according to any one of claims 3-7, characterized in that, The area ratio of the surrounding layer to the first conductive active layer is (10-40):100, preferably (15-25):100; Alternatively, the area ratio of the surrounding layer to the first conductive active layer is (10-40):(90-60), preferably (10-20):(90-80).

11. The positive electrode sheet according to any one of claims 3-7, characterized in that, The first conductivity active layer includes a first active material, a first conductive agent, a first binder, and a first solid electrolyte; And / or, the second conductivity active layer includes a second active material, a second conductive agent, a second binder, and a second solid electrolyte; And / or, the surrounding layer includes a third active material, a third conductive agent, a third binder, and a third solid electrolyte.

12. The positive electrode sheet according to claim 11, characterized in that, The conductivity of the third solid electrolyte is greater than that of the first solid electrolyte, and the conductivity of the first solid electrolyte is greater than that of the second solid electrolyte.

13. The positive electrode sheet according to claim 12, characterized in that, The mass ratio of the first active material, the first conductive agent, the first binder and the first solid electrolyte is (60-90):(1-10):(0-3):(0-30); And / or, the mass ratio of the second active material, the second conductive agent, the second binder and the second solid electrolyte is (60-90):(1-10):(0-3):(0-30); And / or, the mass ratio of the third active material, the third conductive agent, the third binder and the third solid electrolyte is (60-90):(1-10):(0-3):(0-30).

14. The positive electrode sheet according to claim 13, characterized in that, The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each independently comprise at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer solid electrolyte, and satisfy at least one of the following conditions: The D of the oxide solid electrolyte, the sulfide solid electrolyte, and the halide solid electrolyte particles 50 The ranges from 0.5μm to 50μm. The polymer solid electrolyte in the third solid electrolyte accounts for 10% to 100% by weight.

15. A solid-state battery, wherein, Includes the positive electrode sheet as described in any one of claims 1 to 14.

16. An electrical appliance, wherein, Including the solid-state battery as described in claim 15.

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