Composite positive plate, preparation method thereof and solid-state battery

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a composite positive plate, a preparation method thereof and a solid-state battery. The first aspect provides a composite positive plate. The composite positive plate comprises: a positive current collector; the first positive electrode active layer is arranged on at least one side surface of the positive electrode current collector along the thickness direction, and the first positive electrode active layer comprises halide electrolyte; the polymer electrolyte layer is arranged on the surface, far away from the positive electrode current collector, of the first positive electrode active layer; the second positive electrode active layer is arranged on the surface, far away from the first positive electrode active layer, of the polymer electrolyte layer, and the second positive electrode active layer comprises sulfide electrolyte. Compared with an existing positive plate containing sulfide electrolyte, the composite positive plate has better cycling stability when being used, and also has better rate capability when being used compared with an existing positive plate containing halide electrolyte, and meanwhile, the cycling stability and the rate capability of the solid-state battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a composite positive electrode sheet and its preparation method, and a solid-state battery. Background Technology

[0002] With the development of solid-state batteries, sulfide-containing solid electrolytes, which have ionic conductivity comparable to liquid electrolytes, have become the mainstream in application and research. Halogen-containing electrolytes have also seen rapid development in solid-state battery applications due to their high-voltage resistance.

[0003] Batteries prepared with sulfur-containing solid electrolytes or halide-containing electrolytes still face significant challenges in terms of cycle stability and rate performance. These challenges include: environmental pollution caused by the decomposition of sulfur compounds in sulfur-containing electrolyte batteries during use, the generation of unexpected byproducts, and electrode degradation; and the low conductivity of halide-containing electrolytes and the harsh and complex preparation conditions due to the sensitivity of halides to solvents. All of these factors can significantly reduce the cycle stability and rate performance of batteries.

[0004] Therefore, developing a cathode material that can effectively improve the cycle stability and rate performance of solid-state batteries has become a very important research topic. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, this application provides a composite cathode sheet and its preparation method, as well as a solid-state battery. The composite cathode sheet provided by this application exhibits better cycle stability than existing cathode sheets containing sulfide electrolytes and better rate performance than existing cathode sheets containing halide electrolytes, while simultaneously improving the cycle stability and rate performance of solid-state batteries.

[0006] To achieve the above-mentioned objectives, this application provides the following technical solution: A first aspect of this application provides a composite positive electrode sheet, the composite positive electrode sheet comprising: Positive current collector; A first positive electrode active layer is disposed on at least one side surface of the positive electrode current collector along the thickness direction, and the first positive electrode active layer includes a halide electrolyte. A polymer electrolyte layer is disposed on the surface of the first positive electrode active layer away from the positive electrode current collector; A second positive electrode active layer is disposed on the surface of the polymer electrolyte layer away from the first positive electrode active layer, and the second positive electrode active layer includes a sulfide electrolyte.

[0007] As an optional implementation, the total thickness of the first positive electrode active layer and the second positive electrode active layer is 70 µm to 190 µm.

[0008] As an optional implementation, with the sum of the thickness of the first positive electrode active layer and the thickness of the second positive electrode active layer being 100%, the thickness of the first positive electrode active layer accounts for 15% to 40%.

[0009] As an optional implementation, with the sum of the thickness of the first positive electrode active layer and the thickness of the second positive electrode active layer being 100%, the thickness of the second positive electrode active layer accounts for 60% to 85%.

[0010] As an optional implementation, the first positive electrode active layer further includes a first active material, a first conductive agent, and a first binder; the second positive electrode active layer further includes a second active material, a second conductive agent, and a second binder; both the first active material and the second active material include a lithium-containing compound and an ion conductor coating layer.

[0011] As an optional implementation, the general chemical formula of the lithium-containing compound is LiNi. x Co y M z O2, wherein M includes at least one of Mn, Al, Zr, Ti, V, Mg, Fe or Mo, 0≤x<1, 0≤y<1, 0≤z<1, and x+y+z=1.

[0012] As an optional implementation, the thickness of the ion conductor coating layer is 1 nm to 10 nm.

[0013] As an optional implementation, the ionic conductor coating layer includes at least one of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3 or NaPO3.

[0014] As an optional implementation, both the first conductive agent and the second conductive agent include at least one of zero-dimensional conductive agents, one-dimensional conductive agents, or two-dimensional conductive agents.

[0015] As an alternative implementation, the first positive electrode active layer is prepared by a dry process.

[0016] As an optional implementation, the halide electrolyte includes Li3YCl6, Li2ZrCl6, Li3InCl6, and Li 2.2 InZr 0.2 Cl6, Li 2.5 Y0.5 Zr 0.5 Cl6, Li3BrY6, Li3ErCl6, Li3YbCl6, Li 2.4 Yb 0.5 Hf 0.5 Br2Cl 3.9 Li 2.1 Zr 0.95 Cu 0.05 Cl 4.4 O 0.8 or LiZn 0.1 La 0.2 Ce 0.04 Zr 0.15 P 0.09 At least one of Cl3.

[0017] As an optional implementation, the first adhesive comprises PTFE.

[0018] As an alternative implementation, the second positive electrode active layer is prepared by a wet process.

[0019] As an optional implementation, the sulfide electrolyte includes Thio-LISICON, Li 10 GeP2S 12 Li 10 SnP2S 12 Li₂S-P₂S₅, Li 10 SiP2S 12 Li₂S-Si₂S₂, Li₂S-B₂S₃ and Li 7-a PS 6-a R a At least one of them, Li 7-a PS 6-a R a R in the formula includes at least one of Cl, Br, F or I, and 0.1 ≤ a ≤ 5.9.

[0020] As an optional implementation, the second adhesive includes PVD. F and its derivatives At least one of PIB, NBR, HNBR, SBR, SBS, SEBS, PTFE, or PEO.

[0021] As an optional implementation, the number average molecular weight of the second adhesive is 100,000 to 5,000,000.

[0022] As an optional implementation, the thickness of the polymer electrolyte layer is 1 μm to 10 μm.

[0023] As an optional implementation, the room temperature (25°C) conductivity of the polymer electrolyte layer is greater than 5 × 10⁻⁶.- 5 S / cm As an optional implementation, the polymer electrolyte layer includes an ion-conducting agent and a lithium salt.

[0024] As an optional implementation, the mass ratio of the ion-conducting agent to the lithium salt is (3-5):1.

[0025] As an optional implementation, the ion-conducting agent comprises a weakly polar or non-polar polymer and polymer derivatives; the polymer is selected from at least one of polyethylene glycol dimethacrylate, polymethyl methacrylate, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene.

[0026] As an optional implementation, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonylimide, lithium chloride, lithium tetrafluoroborate, lithium hexafluorophosphate, or lithium perchlorate.

[0027] As an optional implementation, by mass percentage: the raw materials for preparing the first positive electrode active layer include 70%~90% of the first active material, 8%~29.8% of the halide electrolyte, 0.1%~1% of the first conductive agent and 0.1%~1% of the first binder.

[0028] As an optional implementation, the raw materials for preparing the second positive electrode active layer, by mass percentage, include 60% to 90% of the second active material, 7% to 39.8% of the sulfide electrolyte, 0.1% to 2% of the second conductive agent, and 0.1% to 1% of the second binder.

[0029] A second aspect of this application provides a method for preparing a composite positive electrode sheet, comprising the following steps: S1: The first positive electrode active layer is disposed on at least one side surface of the positive electrode current collector along the thickness direction to form a first preform; S2: The second positive electrode active layer and the polymer electrolyte layer are sequentially stacked on the surface of the supporting substrate to form a second preform; S3: The first preform and the second preform are laminated together to bring the first positive electrode active layer into contact with the polymer electrolyte layer; S4: Remove the supporting substrate to obtain the composite positive electrode sheet.

[0030] A third aspect of this application provides a solid-state battery, comprising: a composite positive electrode sheet as described in any embodiment of the first aspect of this application, and / or a composite positive electrode sheet obtained by the preparation method described in the second aspect of this application.

[0031] The composite cathode sheet provided in this application has the following beneficial effects: The composite positive electrode sheet provided in this application includes: a positive current collector, a first positive active layer comprising a halide electrolyte disposed on at least one side surface of the positive current collector along the thickness direction, a polymer electrolyte layer disposed on the surface of the first positive active layer away from the positive current collector, and a second positive active layer comprising a sulfide electrolyte disposed on the surface of the polymer electrolyte layer away from the first positive active layer. This design avoids the oxidation, degradation, and decomposition of the sulfide electrolyte, while solving the problem of low conductivity of the halide electrolyte, thus achieving a simultaneous improvement in cycle stability and rate performance of the composite positive electrode sheet during use.

[0032] 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

[0033] Figure 1 This is a schematic diagram of the composite positive electrode sheet of this application. In the diagram, 1 represents the positive electrode current collector, 2 represents the first positive electrode active layer, 3 represents the polymer electrolyte layer, and 4 represents the second positive electrode active layer. Detailed Implementation

[0034] To make the technical solution and beneficial effects of this application more apparent and understandable, a detailed description is provided below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional experimental conditions. Unless otherwise specified, all reagents and raw materials used in this application are commercially available.

[0035] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, to avoid confusion with this application, some technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and steps described in detail.

[0036] In the description of this application, it should be noted that the terms "first," "second," etc., are used for descriptive purposes only and are not intended to indicate or imply relative importance.

[0037] The endpoints and any values ​​of the ranges disclosed herein 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 or 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 herein.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0041] Specifically, this application adopts the following technical solution: [Composite positive electrode plate] In a first aspect, this application provides a composite positive electrode sheet, which includes: Positive current collector 1; A first positive electrode active layer 2 is disposed on at least one side surface of the positive electrode current collector 1 along the thickness direction, and the first positive electrode active layer 2 includes a halide electrolyte. A polymer electrolyte layer 3 is disposed on the surface of the first positive electrode active layer 2 away from the positive electrode current collector 1; The second positive electrode active layer 4 is disposed on the surface of the polymer electrolyte layer 3 away from the first positive electrode active layer 2, and the second positive electrode active layer 4 includes a sulfide electrolyte.

[0042] The phrase "the first positive electrode active layer 2 is disposed on at least one surface of the positive electrode current collector 1 along its thickness direction" means that the first positive electrode active layer 2 can be disposed on one surface of the positive electrode current collector 1 along its own thickness direction, or it can be disposed on two surfaces of the positive electrode current collector 1 along its own thickness direction. Here, "surface" can be the entire area of ​​the positive electrode current collector 1 or a part of the positive electrode current collector 1. As in this embodiment, the surface can be the entire area of ​​the positive electrode current collector 1. This application does not have any particular limitation in this regard, as long as the purpose of this application can be achieved.

[0043] In some embodiments, the positive electrode current collector 1 has two surfaces opposite each other in its own thickness direction, and the first positive electrode active layer 2 is disposed on one of the opposite surfaces of the positive electrode current collector 1. Further, a polymer electrolyte layer 3 is formed on the exposed surface of the first positive electrode active layer 2, in which case the polymer electrolyte layer 3 is away from the positive electrode current collector 1; even further, a second positive electrode active layer 4 is formed on the exposed surface of the polymer electrolyte layer 3.

[0044] It is understood that in other embodiments, the first positive electrode active layer 2 may also be stacked on the two surfaces of the positive electrode current collector 1.

[0045] In this application, the material of the positive current collector 1 is not specifically limited, as long as it can achieve the purpose of this application. Examples include aluminum, copper, stainless steel, titanium, aluminum alloy, copper alloy, titanium alloy, nickel alloy, carbon-coated aluminum foil, carbon-coated copper foil, metal surface composite aluminum oxide, titanium dioxide ceramic, etc.

[0046] The composite cathode provided in this application has a first positive electrode active layer 2 on the positive electrode current collector 1, which contains a halide electrolyte. This provides better voltage stability, avoids the oxidative degradation of the sulfide electrolyte, effectively suppresses the side reaction on the boundary electrode, effectively reduces the cycle capacity decay of the composite cathode during use, and improves the cycle stability of the solid-state battery.

[0047] The polymer electrolyte layer 3 is sandwiched between the first positive electrode active layer 2 and the second positive electrode active layer 4. During the thermal bonding process, the polymer electrolyte layer 3 can fill the pores on the surfaces of the first positive electrode active layer 2 and the second positive electrode active layer 4 through the action of high temperature and pressure. This not only improves the ion pathway on the surface of the composite positive electrode sheet, but also improves the transfer integrity and bonding force of the second positive electrode active layer 4 because the polymer electrolyte layer 3 holds the surfaces of the two positive electrode active layers together. This avoids transfer defects caused by uneven stress or insufficient adhesion, and ensures the structural stability and integrity of the composite positive electrode sheet provided in this application.

[0048] In some embodiments, the first positive electrode active layer 2 further includes a first active material, a first conductive agent, and a first binder; the second positive electrode active layer 4 further includes a second active material, a second conductive agent, and a second binder.

[0049] In some embodiments, the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 is 70 µm to 190 µm. As an example, the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 can be 70 µm, 80 µm, 90 µm, 100 µm, 105 µm, 110 µm, 113 µm, 115 µm, 118 µm, 120 µm, 125 µm, 129 µm, 132 µm, 135 µm, 140 µm, 145 µm, 150 µm, 155 µm, 150 µm, 157 µm, 159 µm, 165 µm, 170 µm, 175 µm, 180 µm, 182 µm, 185 µm, 188 µm, or 190 µm, etc. Of course, it can also be any value within the above range; no specific limitation is made here.

[0050] In some embodiments of this application, taking the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 as 100%, the thickness percentage of the first positive electrode active layer 2 is 15% to 40%. As an example, the thickness percentage of the first positive electrode active layer 2 can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%, etc. Of course, it can also be a value within the above range, and no specific limitation is made here. The thickness of the first positive electrode active layer 2 shall not exceed 40% of the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4. This is because the first positive electrode active layer 2 contains a halide electrolyte, and the room temperature conductivity of the halide electrolyte is usually lower than that of the sulfide electrolyte. This avoids the adverse effect of its low conductivity on the lithium-ion conduction in the composite positive electrode in the thickness direction, which would then affect the rate performance. The thinnest layer shall not be less than 15% of the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4. If it is too thin, the stability of the second positive electrode active layer 4 will be affected due to insufficient coverage.

[0051] In some embodiments of this application, taking the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 as 100%, the thickness percentage of the second positive electrode active layer 4 is 60% to 85%. As an example, the thickness percentage of the second positive electrode active layer 4 can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%, etc. Of course, it can also be any value within the above range, and no specific limitation is made here. The thickness of the second positive electrode active layer 4 is not less than 60% of the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4, because the second positive electrode active layer 4 contains a sulfide electrolyte, ensuring the advantage of the composite positive electrode sheet in rate performance. Furthermore, because the thickness percentage of the second positive electrode active layer 4 is above 60%, the use of halide electrolyte is reduced, lowering the cost of the composite positive electrode sheet.

[0052] In some embodiments, the first positive electrode active layer further includes a first active material, a first conductive agent, and a first binder; the second positive electrode active layer further includes a second active material, a second conductive agent, and a second binder. In some embodiments of this application, both the first active material and the second active material include a lithium-containing compound and an ion conductor coating layer.

[0053] In some embodiments of this application, the general chemical formula of the lithium-containing compound is LiNi.x Co y M z O2, wherein M includes at least one of Mn, Al, Zr, Ti, V, Mg, Fe, or Mo, 0 ≤ x < 1, 0 ≤ y < 1, 0 ≤ z < 1, and x + y + z = 1. As an example, x can take values ​​of 0, 0.1, 0.3, 0.5, 0.7, 0.8, or 0.9; y can take values ​​of 0, 0.2, 0.4, 0.5, 0.7, 0.8, or 0.9; and z can take values ​​of 0, 0.1, 0.3, 0.5, 0.6, 0.8, or 0.9. Of course, it can also be any value within the above ranges, without specific limitations. As an example, lithium-containing compounds include, but are not limited to, LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.5Co0.2Mn0.3O2, LiNi0.6Co0.2Mn0.2O2, LiNi0.7Co0.2Mn0.1O2, LiNi0.9Co0. 05 Mn0. 05 O2, etc.

[0054] In some embodiments of this application, the thickness of the ion conductor coating layer is 1 nm to 10 nm. As an example, the thickness of the ion conductor coating layer can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm, etc., or it can be any value within the above range, and no specific limitation is made here.

[0055] In some embodiments of this application, the ionic conductor coating layer includes, but is not limited to, at least one of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3, and NaPO3.

[0056] As an example, both the first and second active substances can be NCM811@LiNbO3, NCM622@Li2ZrO3, NCM523@Li2MnO4, NCM721@Li2TiO3, etc.

[0057] Both the first and second active materials can be purchased directly, and there are no restrictions on the manufacturers, as long as the lithium-containing compound and the ion conductor coating can meet the above requirements. For example, those produced by Beijing Dangsheng Materials Technology Co., Ltd. and Ningbo Rongbai New Energy Technology Co., Ltd. are acceptable.

[0058] In some embodiments of this application, both the first conductive agent and the second conductive agent include at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, or a two-dimensional conductive agent. As examples, the zero-dimensional conductive agent may be conductive carbon black (SP) and / or acetylene black (AB), etc.; the one-dimensional conductive agent may be carbon nanotubes (CNTs) and / or vapor-grown carbon fibers (VGCF), etc.; and the two-dimensional conductive agent may be graphene, etc.

[0059] In some embodiments, the first positive electrode active layer 2 is prepared by a dry process.

[0060] Halogen electrolytes exhibit high stability to cathode materials but are highly sensitive to solvents. Traditional wet preparation processes for halide electrolytes require strict control of solvent type, drying temperature, and drying time, resulting in high process complexity. This application innovatively employs a dry preparation method, avoiding the use of solvents in this stage, ensuring the presence of halides in the composite cathode, preserving the high voltage window (maximum voltage window > 4.5V) property of the halide electrolyte, improving the stability of the cathode material, and guaranteeing the cycle stability of the prepared composite cathode.

[0061] In some embodiments of this application, the halide electrolyte includes, but is not limited to, Li3YCl6, Li2ZrCl6, Li3InCl6, and Li 2.2 InZr 0.2 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li3BrY6, Li3ErCl6, Li3YbCl6, Li 2.4 Yb 0.5 Hf 0.5 Br2Cl 3.9 Li 2.1 Zr 0.95 Cu 0.05 Cl 4.4 O 0.8 or LiZn 0.1 La 0.2 Ce 0.04 Zr 0.15 P 0.09 At least one of Cl3.

[0062] In some embodiments of this application, the first adhesive includes, but is not limited to, polytetrafluoroethylene (PTFE), as long as it is suitable for a dry preparation process and achieves the purpose of this application. As an example, the first adhesive may be PTFE.

[0063] In some embodiments, the second positive electrode active layer 4 is prepared by a wet process.

[0064] The second positive electrode active layer 4 in this application is obtained by a wet preparation process. In the wet preparation process, the excellent fluidity and wettability of the liquid slurry can seamlessly encapsulate each particle of the second active material, fill the gaps between the particles, ensure a smooth transport path for ions between the particles, and the preparation process is not limited by solvents, has low cost, and is simple to operate.

[0065] In some embodiments, the sulfide electrolyte includes Thio-LISICON, Li 10 GeP2S 12 Li 10 SnP2S 12 Li₂S-P₂S₅, Li 10 SiP2S 12 Li₂S-Si₂S₂, Li₂S-B₂S₃ and Li 7-a PS 6-a R a At least one of them.

[0066] Furthermore, Li 7-a PS 6-a R a R in the stoichiometric electrolyte includes at least one of Cl, Br, F, or I, and 0.1 ≤ a ≤ 5.9. For example, the value of a can be 0.1, 0.5, 1.0, 1.5, 1.8, 2.3, 2.5, 3.4, 3.8, 4.1, 4.5, 4.9, 5.2, 5.5, or 5.9, or any value within the above range; no specific limitation is made here. For example, sulfide electrolytes include, but are not limited to, Li. 5.5 PS 4.5 Cl 1.5 .

[0067] In some embodiments of this application, the second adhesive includes, but is not limited to, adhesives well known to those skilled in the art; examples include at least one of polyvinylidene fluoride (PVDF) and its derivatives, polyisobutylene (PIB), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), polytetrafluoroethylene (PTFE), and polyethylene oxide (PEO); examples of polyvinylidene fluoride derivatives include PVDF5130, PVDF75130, PVDF21216, PVDF6020, PVDF-HVS900, PVDF-HFP, PVDF-LBG, etc.

[0068] In some embodiments of this application, the number average molecular weight of the second adhesive is between 100,000 and 5,000,000. As an example, the number average molecular weight of the second adhesive can be 200,000, 300,000, 500,000, 1,000,000, 2,000,000, 3,000,000, or 5,000,000, etc., or it can be a value within the above range, and no specific limitation is made here.

[0069] In some embodiments, the thickness of the polymer electrolyte layer is 1 μm to 10 μm. As an example, the thickness of the polymer electrolyte layer can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 10 μm, etc., or it can be any value within the above range, and no specific limitation is made here.

[0070] In some embodiments of this application, the polymer electrolyte layer comprises an ion-conducting agent and a lithium salt; the mass ratio of the ion-conducting agent to the lithium salt is (3-5):1. As an example, the mass ratio of the ion-conducting agent to the lithium salt can be any value among 3:1, 4:1, 5:1, or any value within the range of any two of the above values.

[0071] In some embodiments of this application, the ion-conducting agent comprises a weakly polar or nonpolar polymer and polymer derivatives; the polymer includes, but is not limited to, at least one of polyethylene glycol dimethacrylate, polymethyl methacrylate, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene. The lithium salt includes, but is not limited to, at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonylimide, lithium chloride, lithium tetrafluoroborate, lithium hexafluorophosphate, or lithium perchlorate.

[0072] In some embodiments of this application, the room temperature conductivity of the polymer electrolyte layer is greater than 5 × 10⁻⁶. -5 S / cm. The room temperature conductivity of the polymer electrolyte used in this application is greater than 5 × 10⁻⁶. -5 The high room temperature conductivity (S / cm) of the polymer electrolyte layer indicates that the Li in the battery... + Polymer electrolytes have faster carrier migration speeds, allowing ions to rapidly transport between the positive and negative electrodes during battery charging and discharging. This reduces the probability of side reactions at the cathode interface and improves battery cycle stability. However, polymer electrolytes typically have lower room temperature conductivity than halide electrolytes (10⁻⁶ Ω·cm). -3 ~3×10 -2 S / cm) and sulfide electrolyte (10 -3 ~10 -2 The thickness (S / cm) is lower, and its thickness is controlled to not exceed 10 μm when used in this application.

[0073] In this application, the room-temperature conductivity was measured using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation at a frequency range of 0.1 Hz to 10 MHz, an amplitude of 10 mV, and a temperature of 25 °C, by assembling a symmetrical cell with a steel sheet as the blocking electrode. The calculation formula is: σ = L / (Rb·S), where S represents the effective contact area (cm²) between the electrolyte and the blocking electrode. 2 L represents the thickness of the polymer electrolyte membrane (cm), and Rb represents the total impedance of the electrolyte (Ω).

[0074] In some embodiments, by mass percentage, the raw materials for preparing the first positive electrode active layer 2 include 70%~90% of the first active material, 8%~29.8% of the halide electrolyte, 0.1%~1% of the first conductive agent, and 0.1%~1% of the first binder. As an example, the mass percentage of the raw materials for preparing the first positive electrode active layer 2 can be: 70% of the first active material, 29.8% of the halide electrolyte, 0.1% of the first conductive agent, and 0.1% of the first binder; or it can be: 90% of the first active material, 8% of the halide electrolyte, 1% of the first conductive agent, and 1% of the first binder, etc. Of course, it can also be any value within the above range, and no specific limitation is made here.

[0075] In some embodiments, by mass percentage, the raw materials for preparing the second positive electrode active layer 4 include 60%~90% of the second active material, 7%~39.8% of the sulfide electrolyte, 0.1%~2% of the second conductive agent, and 0.1%~1% of the second binder. As an example, the mass percentage of the raw materials for preparing the second positive electrode active layer 4 can be: 60% of the second active material, 39.8% of the sulfide electrolyte, 0.1% of the second conductive agent, and 0.1% of the second binder; or it can be: 90% of the second active material, 7% of the sulfide electrolyte, 1.5% of the second conductive agent, and 1.5% of the second binder; or it can be: 70% of the second active material, 28% of the sulfide electrolyte, 1% of the second conductive agent, and 1% of the second binder, etc. Of course, it can also be any value within the above range, and no specific limitation is made here.

[0076] Based on the above scheme, this application creatively provides a composite cathode design, which largely balances cycle stability and rate performance through the stacked arrangement of the first positive electrode active layer 2, polymer electrolyte layer 3, and second positive electrode active layer 4. Since the first positive electrode active layer 2 contains high-valence cations, under high state of charge (SOC) conditions, direct contact between the first positive electrode active layer 2 and the second positive electrode active layer 4 at the cathode interface would lead to the oxidative decomposition of the sulfide electrolyte in the second positive electrode active layer 4, exacerbating the interface degradation between the two layers. The creative introduction of the polymer electrolyte layer 3 in this application forms a flexible chemical barrier between the first positive electrode active layer 2 and the second positive electrode active layer 4, reducing the influence of ion conduction at the interface and comprehensively improving the cycle stability and rate performance of the composite cathode.

[0077] [Preparation of composite cathode sheets] A second aspect of the present invention provides a method for preparing a composite positive electrode, comprising the following steps: S1: The first positive electrode active layer 2 is disposed on at least one side surface of the positive electrode current collector 1 along the thickness direction to form a first preform; S2: The second positive electrode active layer 4 and the polymer electrolyte layer 2 are sequentially stacked on the surface of the supporting substrate to form a second preform; S3: The first preform and the second preform are laminated together to bring the first positive electrode active layer 2 into contact with the polymer electrolyte layer 3; S4: Remove the supporting substrate to obtain the composite positive electrode sheet.

[0078] It should be understood that all the features and advantages described above regarding the "composite positive electrode sheet" also apply to the "preparation method of the composite positive electrode sheet", and will not be repeated here.

[0079] [Preparation of the first positive electrode active layer] In some embodiments, the first positive electrode active layer 2 is prepared by a dry method, the dry preparation method comprising: After mixing the first active material, halide electrolyte, and first conductive agent, a first binder is added, and the mixture is ground and drawn into fibers. This mixture is then ground into a rubbery, lumpy mass and rolled to the required thickness to obtain the first positive electrode active layer 2. Halide electrolytes exhibit high stability to the positive electrode material but are highly sensitive to solvents. Traditional wet preparation processes for halide electrolytes require strict control of solvent type, drying temperature, and drying time, resulting in high process complexity. This application innovatively employs a dry preparation method, avoiding the use of solvents in this stage, ensuring the presence of halides in the composite positive electrode, preserving the high voltage window (maximum voltage window > 4.5V) property of the halide electrolyte, improving the stability of the positive electrode material, and guaranteeing the cycle stability of the prepared composite positive electrode.

[0080] In some embodiments, the rolling temperature is 110°C to 150°C. For example, the rolling temperature can be 110°C, 120°C, 130°C, 140°C, 150°C, etc., or it can be a value within the above range. No specific limitation is made here.

[0081] In some embodiments, the required thickness is calculated as 100% of the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4, with the thickness of the first positive electrode active layer 2 accounting for 15% to 40%. The sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 is 70 µm to 190 µm, and the thickness of the first positive electrode active layer 2 is 10.5 µm to 76 µm. As an example, the thickness of the first positive electrode active layer 2 can be 10.5 µm, 15 µm, 20 µm, 28.5 µm, 35 µm, 46 µm, 58 µm, 65 µm, 76 µm, etc., or it can be a value within the above range, without specific limitation here.

[0082] [Preparation of the first preform] In some embodiments, the first positive electrode active layer 2 is combined with the positive electrode current collector 1 to obtain a first preform.

[0083] In some embodiments, the composite temperature with the positive current collector 1 is 80°C to 110°C. As an example, the composite temperature can be 80°C, 90°C, 100°C, 110°C, etc., or it can be a point value within the above range. No specific limitation is made here.

[0084] In this application, the material of the positive current collector 1 is not specifically limited, as long as it can achieve the purpose of this application. Examples include aluminum, copper, stainless steel, titanium, aluminum alloy, copper alloy, titanium alloy, nickel alloy, carbon-coated aluminum foil, carbon-coated copper foil, metal surface composite aluminum oxide, titanium dioxide ceramic, etc. As an example, it can be carbon-coated aluminum foil.

[0085] [Preparation of the second positive electrode active layer] In some embodiments, the second positive electrode active layer 4 is prepared by a wet process, wherein the wet preparation method includes: After mixing the second active material, sulfide electrolyte, and second conductive agent, the second binder dissolved in solvent is added and ball-milled to obtain the second positive electrode active layer 4 slurry. Then, the slurry is coated on the substrate according to the designed thickness, dried, and rolled to obtain the second positive electrode active layer 4 of the required thickness.

[0086] In some embodiments, the wet preparation uses a solvent, which includes, but is not limited to, dichloromethane, n-hexane, n-heptane, toluene, and 2,4-dichloromethane. At least one of dimethyl-3-pentanone, monochlorobenzene, xylene, toluene, isobutyl isobutyrate, anisole, cyclohexanone, 1,3,5-trimethylbenzene, n-decane, dodecane, and methylformamide.

[0087] In this application, the material or type of the substrate used in the preparation of the second positive electrode active layer 4 is not limited, and any substrate known in the art that can be used for the preparation of wet-process sulfide-containing electrolyte electrodes can be selected.

[0088] In this application, the grinding method, drying and rolling temperature, and other process parameters are not limited in the preparation of the second positive electrode active layer 4. They can be operated according to conditions known in the art, as long as the preparation of the second positive electrode active layer 4 can be achieved. The second positive electrode active layer 4 in this application is obtained through a wet preparation process. In this wet preparation process, the excellent fluidity and wettability of the liquid slurry can seamlessly encapsulate each particle of the second active material, filling the gaps between particles and ensuring a smooth transport path for ions between particles. Furthermore, the preparation process is not limited by solvents, has low cost, and is simple to operate.

[0089] In some embodiments, the designed thickness is calculated as 100% of the sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4, with the thickness of the second positive electrode active layer 4 accounting for 60% to 85%. The sum of the thickness of the first positive electrode active layer 2 and the thickness of the second positive electrode active layer 4 is 70 µm to 190 µm, and the thickness of the first positive electrode active layer 2 is 42 µm to 161.5 µm. As an example, the thickness of the second positive electrode active layer 4 can be 42 µm, 48 µm, 59.5 µm, 68 µm, 72 µm, 85 µm, 94 µm, 102 µm, 114 µm, 125 µm, 136 µm, 145 µm, 158 µm, 161.5 µm, etc., or it can be any value within the above range, without specific limitation here.

[0090] [Preparation of the second preform] In some embodiments, the method for preparing a second preform containing a polymer electrolyte layer includes the following steps: Take an ion-conducting agent and lithium salt, stir and dissolve them in a solvent. After complete dissolution, a polymer electrolyte layer 3 slurry is obtained. This slurry is coated on the surface of the second positive electrode active layer 4 away from the substrate and dried to form the second preform.

[0091] In some embodiments, the solvent includes, but is not limited to, dichloromethane, n-hexane, n-heptane, toluene, and 2,4-dichloromethane. At least one of dimethyl-3-pentanone, monochlorobenzene, xylene, toluene, isobutyl isobutyrate, anisole, cyclohexanone, 1,3,5-trimethylbenzene, n-decane, dodecane, and methylformamide.

[0092] In some embodiments, the drying temperature is 50℃-80℃, and the drying time is 24h-72h. As an example, the drying temperature can be 50℃, 60℃, 70℃, 80℃, etc., or any value within the above range; no specific limitation is made here. The drying time can be 24h, 30h, 48h, 60h, 72h, etc., or any value within the above range; no specific limitation is made here.

[0093] [Laminated composite of first and second preforms] In some embodiments, the first preform and the second preform are laminated together so that the first positive electrode active layer 2 is in contact with the polymer electrolyte layer 3.

[0094] In some embodiments, the lamination pressure is 10MPa-100MPa, and the temperature is 80℃-120℃. As an example, the lamination pressure can be 10MPa, 30MPa, 70MPa, 80MPa, 90MPa, etc., or any value within the above range; no specific limitation is made here. The temperature can be 80℃, 90℃, 100℃, 110℃, or 120℃, etc., or any value within the above range; no specific limitation is made here.

[0095] Therefore, based on the above scheme, the composite cathode sheet of this application uses a specific composite process sequence to ensure that the polymer electrolyte layer 3 can effectively fill the pores between the first positive electrode active layer 2 and the second positive electrode active layer 4, forming a continuous ion pathway. During the rolling process, the polymer electrolyte softens and its viscosity increases. Under pressure, it fills the pores between the first positive electrode active layer 2 and the second positive electrode active layer 4, forming a flexible chemical barrier between the first positive electrode active layer 2 and the second positive electrode active layer 4, playing an interfacial buffering role and improving the interfacial bonding force. At the same time, this design avoids the oxidative degradation and decomposition of sulfide electrolytes, and solves the problem of low conductivity of halide electrolytes. It realizes the combination of dry preparation process and wet preparation process, and successfully constructs the composite cathode sheet structure, which helps to improve the cycle stability and rate performance of solid-state batteries.

[0096] Since the solid-state battery provided in this embodiment of the invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0097] The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0098] Example 1 The structure of a composite positive electrode is as follows Figure 1 As shown, the composite positive electrode sheet includes a positive current collector 1, a first positive active layer 2, a polymer electrolyte layer 3, and a second positive active layer 4. The total thickness of the first positive active layer 2 and the second positive active layer 4 is 100µm. The thickness of the first positive active layer 2 is 25µm, which is 25% of the total thickness of the first positive active layer 2 and the second positive active layer 4. The thickness of the second positive active layer 4 is 75µm. The specific steps are as follows: S1: Take materials according to the following mass ratio (first active material (NCM811@LiNbO3): halide electrolyte (Li3InCl6): first conductive agent carbon nanotube (CNT): first binder polytetrafluoroethylene (PTFE) ratio of 70:29.8:0.1:0.1), grind and mix for 1 hour to complete the fiberization mixing, then hot roll press at 150℃ to a thickness of 25µm to obtain the first positive electrode active layer 2, and then roll press at 80℃ on the positive electrode current collector 1 (carbon-coated aluminum foil) to obtain the first preform; S2: According to the following mass ratio (second active material NCM811@LiNbO3: sulfide electrolyte Li...) 5.5 PS 4.5 Cl1.5 The ratio of the second conductive agent, vapor-grown carbon fiber (VGCF), to the second binder, polyisobutylene (PIB), is 70:28:1:1. The second active material, sulfide electrolyte, and second conductive agent are stirred and premixed for 1 hour. Then, PIB dissolved in anisole is added to the mixture and ball-milled for 1 hour to obtain the second positive electrode active layer 4 slurry. Then, it is coated on the substrate aluminum foil and dried. The second positive electrode active layer 4 is rolled to a thickness of 75µm. S3: Take the ion-conducting agent polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and lithium salt bis(trifluoromethanesulfonyl)imide in a mass ratio of 5:1, stir and dissolve them in xylene. After complete dissolution, a polymer electrolyte layer 3 slurry is obtained, which is coated on the surface of the second positive electrode active layer 4 away from the substrate. The thickness of the polymer electrolyte layer 3 is 2µm. It is dried under vacuum at 80℃ for 24h to obtain the second preform. S4: The polymer electrolyte layer 3 in the second preform obtained in S3 is bonded to the first positive electrode active layer 2 in the first preform obtained in S1, and then rolled and compounded under conditions of 90°C and 100MPa. After peeling off the substrate aluminum foil in the second preform, a composite positive electrode sheet is formed.

[0099] The first and second active materials are both NCM811@LiNbO3, and the thickness of the ion conductor coating layer is 5 nm, which was purchased from Beijing Dangsheng Materials Technology Co., Ltd.

[0100] Example 2 This embodiment provides a composite positive electrode sheet, which is implemented in the same way as in embodiment 1. The difference is that the thickness of the first positive electrode active layer 2 is adjusted to 15% of the total thickness of the first positive electrode active layer 2 and the second positive electrode active layer 4, i.e., 15µm, and the thickness of the second positive electrode active layer 4 is adjusted to 85µm.

[0101] Example 3 This embodiment provides a composite positive electrode sheet, which is implemented in the same way as in Embodiment 1. The difference is that the thickness of the first positive electrode active layer 2 is adjusted to 40% of the total thickness of the first positive electrode active layer 2 and the second positive electrode active layer 4, i.e., 40µm, and the thickness of the second positive electrode active layer 4 is adjusted to 60µm.

[0102] Example 4 This embodiment provides a composite positive electrode sheet, the specific implementation of which is the same as that of Embodiment 1. The difference from Embodiment 1 is that the ion-conducting agent and lithium salt in S3 are replaced with polymethyl methacrylate and lithium trifluoromethanesulfonylimide, respectively.

[0103] Example 5 This embodiment provides a composite positive electrode sheet, the specific implementation of which is the same as that of Embodiment 1. The difference from Embodiment 1 is that the ion-conducting agent and lithium salt in S3 are replaced with polyethylene glycol dimethacrylate and lithium bis(trifluoromethanesulfonyl)imide, respectively.

[0104] Example 6 This embodiment provides a composite positive electrode, the specific implementation of which is the same as in Embodiment 1, except that the halide electrolyte in S1 is replaced with Li. 2.5 Y 0.5 Zr 0.5 Cl6.

[0105] Example 7 This embodiment provides a composite positive electrode sheet, the specific implementation of which is the same as in Embodiment 1, except that the sulfide electrolyte in S2 is replaced with Li. 5.5 PS 4.5 Cl 0.7 Br 0.8 .

[0106] Example 8 This embodiment provides a composite positive electrode sheet, the specific implementation of which is the same as in Embodiment 1, except that the halide electrolyte in S1 is replaced with Li3YbCl6 and the sulfide electrolyte in S2 is replaced with Li 5.4 PS 4.4 Cl 1.6 .

[0107] Comparative Example 1 This example provides a positive electrode sheet with the following mass ratio: positive electrode active material NCM811@LiNbO3: halide electrolyte Li3InCl6: conductive agent CNT: binder PTFE 70:29.8:0.1:0.1. The materials were first ground and mixed for 1 hour to complete the fibrous mixing, then hot-rolled at 150°C to a thickness of 25µm, and then rolled onto carbon-coated aluminum foil at 80°C to obtain the positive electrode sheet of Comparative Example 1. The manufacturer of the positive electrode active material NCM811@LiNbO3 and the thickness of the ion conductor coating layer are the same as in Example 1.

[0108] Comparative Example 2 This example provides a positive electrode sheet, with the following mass ratio of positive electrode active material NCM811@LiNbO3: sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5The ratio of conductive agent VGCF to binder PIB is 70:28:1:1. First, the positive electrode active material, sulfide electrolyte, and conductive agent are stirred and premixed for 1 hour. Then, PIB dissolved in anisole is added to the mixture and ball-milled for 1 hour to obtain a sulfide electrolyte positive electrode slurry. This slurry is then coated onto aluminum foil, dried, and rolled to a thickness of 75 µm to obtain the positive electrode sheet of Comparative Example 2. The supplier of the positive electrode active material NCM811@LiNbO3 and the thickness of the ion conductor coating are the same as in Example 1.

[0109] Comparative Example 3 This example provides a composite positive electrode sheet. Compared with Example 1, the first positive electrode active layer 2 is prepared as a wet halide active layer using the solvent and the second binder used in S2 of Example 1, while other steps remain unchanged.

[0110] Comparative Example 4 This example provides a composite positive electrode sheet, the specific implementation of which is the same as in Example 1. The difference from Example 1 is that the positions of the first positive electrode active layer 2 and the second positive electrode active layer 4 are interchanged, while the preparation methods of each layer remain unchanged.

[0111] Comparative Example 5 This example provides a composite positive electrode sheet, the specific implementation of which is the same as in Example 1. The difference from Example 1 is that there is no polymer electrolyte layer 3, and the first positive electrode active layer 2 and the second positive electrode active layer 4 are directly pressed together in contact.

[0112] Comparative Example 6 This example provides a composite positive electrode sheet, the specific implementation of which is the same as in Example 1. The difference from the example is that the thickness of the first positive electrode active layer 2 is adjusted to 50% of the total thickness of the first positive electrode active layer 2 and the second positive electrode active layer 4, that is, 50µm, and the thickness of the second positive electrode active layer 4 is adjusted to 50µm.

[0113] Performance testing 1. Solid-state battery fabrication The positive electrode sheets prepared in the examples and comparative examples were stamped to a diameter of 10 mm. 100 mg of Li was taken. 5.5 PS 4.5 Cl 1.5 The electrolyte sheet was prepared by placing it into a mold battery with a 10mm aperture and holding it at 300MPa for 3 minutes. The sample was used as the working electrode. Then, a composite negative electrode consisting of an indium foil with a diameter of 10mm and a thickness of 100µm and a lithium copper composite strip with a lithium metal layer of 50µm was used as the counter electrode, with the indium foil facing the electrolyte layer. The solid-state mold battery was then assembled.

[0114] Rate and cycle performance tests were conducted. The mold battery was tested at a holding pressure of 100 MPa and a test temperature of 45℃. Charge-discharge tests were performed at 0.1C, 0.33C, and 1C to characterize the rate performance of the electrodes. The rate performance at 0.33C / 0.1C, the rate performance at 1C / 0.1C, and the capacity retention rate at 0.33C@200 cycles are recorded in Table 1 below. The method for testing rate performance is as follows: Using the Blue Battery Testing System, at 25℃, the battery was charged to 4.25V at a constant current and constant voltage of 0.1C, then left to stand for 5 minutes. Subsequently, it was discharged to 2.2V at a constant current of 0.1C, and left to stand for 5 minutes. This charge-discharge cycle was repeated 3 times, and the average value of the 3 discharge cycles was taken as the 0.1C discharge capacity. Then, the charge-discharge rate was changed to 0.33C and 1C in the same way to complete the 0.33C and 1C discharge capacity tests. The formula for calculating the rate capability at 0.33C / 0.1C is: Rate performance at 0.33C / 0.1C = (Discharge capacity at 0.33C) / (Discharge capacity at 0.1C) × 100%; The formula for calculating the rate capability at 1C / 0.1C is: Rate performance at 1C / 0.1C = (Discharge capacity at 1C) / (Discharge capacity at 0.1C) × 100%; The test method and calculation formula for capacity retention rate at 0.33C@200 cycles are as follows: Using the Blue Battery testing system, at 25℃, the battery was charged to 4.25V at a constant current and constant voltage of 0.33C, allowed to rest for 5 minutes, and then discharged to 2.2V at a constant current of 0.33C, allowed to rest for 5 minutes, and the capacity was recorded as the initial discharge capacity C0. After 200 cycles, the discharge capacity was recorded as C1. The capacity retention rate after 200 cycles = C1 / C0 × 100%.

[0115] Table 1. Results of Ratio and Cyclic Performance Tests

[0116] Referring to the data in Table 1, a comparison of Examples 1 to 8 and Comparative Examples 1 and 2 shows that: Compared with the single electrolyte layer structure, the composite cathode structure provided in this application has significantly improved the rate performance and cycle stability. The 1C / 0.1C rate performance of Example 1 is 79.1%, which is 1.5 times that of Example 1 (51.9%), and the cycle capacity retention rate is 90%, which is 1.36 times that of Example 2. Furthermore, the 1C / 0.1C rate performance of the schemes claimed in Examples 1 to 8 is all above 69.2%, reaching a maximum of 81.1%; the cycle capacity retention rate is all above 88.3%, reaching a maximum of 92.7%. This proves that the composite cathode structure design proposed in this application achieves complementary advantages and balances the rate performance and cycle stability of the battery.

[0117] As can be seen from the data in Table 1 and the data in Example 1 and Comparative Example 3, the dry preparation process of the first positive electrode active layer plays an important role in improving the rate performance and cycle stability of the battery. The dry preparation process avoids the failure of the halide electrolyte and ensures stable ion transport.

[0118] As can be seen from the data in Table 1 and the data in Example 1 and Comparative Example 4, the order of each layer of the composite cathode provided in this application cannot be reversed or interchanged, otherwise it will affect the ion transport path and cause a significant decrease in 1C / 0.1C rate performance and cycle capacity retention.

[0119] As can be seen from the data in Table 1 and the data in Example 1 and Comparative Example 5, the polymer electrolyte layer is an indispensable structural design, proving that this layer is the core bridge for interface compatibility and ion conduction. Direct pressing will lead to poor interface contact, and the lack of a polymer electrolyte layer will result in a significant reduction in 1C / 0.1C rate performance and cycle capacity retention.

[0120] The composite cathode provided in this application ultimately achieves simultaneous improvement in rate performance and cycle stability, thus fulfilling the purpose of the invention.

[0121] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0122] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0123] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite positive electrode, characterized in that, The composite cathode includes: Positive current collector; A first positive electrode active layer is disposed on at least one side surface of the positive electrode current collector along the thickness direction, and the first positive electrode active layer includes a halide electrolyte. A polymer electrolyte layer is disposed on the surface of the first positive electrode active layer away from the positive electrode current collector; A second positive electrode active layer is disposed on the surface of the polymer electrolyte layer away from the first positive electrode active layer, and the second positive electrode active layer includes a sulfide electrolyte.

2. The composite positive electrode sheet according to claim 1, characterized in that, The total thickness of the first positive electrode active layer and the second positive electrode active layer is 70 µm to 190 µm. And / or, based on the sum of the thickness of the first positive electrode active layer and the thickness of the second positive electrode active layer being 100%, the thickness of the first positive electrode active layer accounts for 15% to 40%; And / or, with the sum of the thickness of the first positive electrode active layer and the thickness of the second positive electrode active layer being 100%, the thickness of the second positive electrode active layer accounts for 60% to 85%.

3. The composite positive electrode sheet according to claim 1, characterized in that, The first positive electrode active layer further includes a first active material, a first conductive agent, and a first binder; the second positive electrode active layer further includes a second active material, a second conductive agent, and a second binder. Preferably, both the first active material and the second active material comprise a lithium-containing compound and an ion conductor coating layer; Preferably, the general chemical formula of the lithium-containing compound is LiNi. x Co y M z O2, wherein M includes at least one of Mn, Al, Zr, Ti, V, Mg, Fe or Mo, 0≤x<1, 0≤y<1, 0≤z<1, and x+y+z=1; Preferably, the thickness of the ion conductor coating layer is 1 nm to 10 nm; Preferably, the ion conductor coating layer includes at least one of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3 or NaPO3; Preferably, both the first conductive agent and the second conductive agent include at least one of a zero-dimensional conductive agent, a one-dimensional conductive agent, or a two-dimensional conductive agent.

4. The composite positive electrode sheet according to claim 3, characterized in that, The first positive electrode active layer satisfies at least one of the following characteristics: (1) The first positive electrode active layer is prepared by a dry method; (2) The halide electrolytes include Li3YCl6, Li2ZrCl6, Li3InCl6, and Li 2.2 InZr 0.2 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li3BrY6, Li3ErCl6, Li3YbCl6, Li 2.4 Yb 0.5 Hf 0.5 Br2Cl 3.9 Li 2.1 Zr 0.95 Cu 0.05 Cl 4.4 O 0.8 or LiZn 0.1 La 0.2 Ce 0.04 Zr 0.15 P 0.09 At least one of Cl3; (3) The first adhesive includes PTFE.

5. The composite positive electrode sheet according to claim 3, characterized in that, The second positive electrode active layer satisfies at least one of the following characteristics: (1) The second positive electrode active layer is prepared by a wet process; (2) The sulfide electrolytes include Thio-LISICON and Li 10 GeP2S 12 Li 10 SnP2S 12 Li₂S-P₂S₅, Li 10 SiP2S 12 Li₂S-Si₂S₂, Li₂S-B₂S₃ and Li 7-a PS 6-a R a At least one of them, Li 7-a PS 6-a R a R in the form includes at least one of Cl, Br, F or I, and 0.1 ≤ a ≤ 5.9; (3) The second adhesive includes at least one of PVDF and its derivatives, PIB, NBR, HNBR, SBR, SBS, SEBS, PTFE or PEO; (4) The number average molecular weight of the second adhesive is 100,000 to 5 million.

6. The composite positive electrode sheet according to claim 1, characterized in that, The thickness of the polymer electrolyte layer is 1 μm to 10 μm; And / or, the room temperature conductivity of the polymer electrolyte layer is greater than 5 × 10⁻⁶. -5 S / cm.

7. The composite positive electrode sheet according to claim 1 or 6, characterized in that, The polymer electrolyte layer includes an ion-conducting agent and a lithium salt; Preferably, the mass ratio of the ion-conducting agent to the lithium salt is (3-5):1; Preferably, the ion-conducting agent comprises a weakly polar or non-polar polymer and polymer derivatives; the polymer is selected from at least one of polyethylene glycol dimethacrylate, polymethyl methacrylate, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene. Preferably, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonylimide, lithium chloride, lithium tetrafluoroborate, lithium hexafluorophosphate, or lithium perchlorate.

8. The composite positive electrode sheet according to claim 1, characterized in that, By weight percentage: The raw materials for preparing the first positive electrode active layer include 70%~90% of a first active material, 8%~29.8% of a halide electrolyte, 0.1%~1% of a first conductive agent, and 0.1%~1% of a first binder; The raw materials for preparing the second positive electrode active layer include 60%~90% of the second active material, 7%~39.8% of the sulfide electrolyte, 0.1%~2% of the second conductive agent, and 0.1%~1% of the second binder.

9. A method for preparing a composite positive electrode sheet according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1: The first positive electrode active layer is disposed on at least one side surface of the positive electrode current collector along the thickness direction to form a first preform; S2: The second positive electrode active layer and the polymer electrolyte layer are sequentially stacked on the surface of the supporting substrate to form a second preform; S3: The first preform and the second preform are laminated together to bring the first positive electrode active layer into contact with the polymer electrolyte layer; S4: Remove the supporting substrate to obtain the composite positive electrode sheet.

10. A solid-state battery, characterized in that, It includes the composite positive electrode sheet described in any one of claims 1 to 8, or the composite positive electrode sheet prepared by the preparation method according to claim 9.

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