A positive electrode sheet, a battery, and an electric device

Abstract

This application provides a positive electrode sheet comprising a positive electrode current collector; a positive electrode active layer disposed on at least one side of the positive electrode current collector in the thickness direction; the positive electrode active layer comprising a positive electrode active material and a solid electrolyte; wherein the positive electrode active material comprises lithium metal oxide and lithium metal sulfide. The positive electrode sheet provided in this application introduces a solid electrolyte into the positive electrode active layer and employs a composite active material composed of lithium metal oxide and lithium metal sulfide. Through the synergistic effect of these three materials, a highly efficient ion and electron conduction network is constructed, effectively reducing the solid-solid interface impedance, thereby improving the specific capacity, rate performance, and cycle performance of the solid-state battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode, a battery, and an electrical device. Background Technology

[0002] With the increasing urgency of electric vehicles and large-scale energy storage systems demanding high safety and high energy density, the research and development of next-generation power battery technology has become a core focus in the new energy field. Solid-state batteries, which use non-flammable solid electrolytes instead of traditional electrolytes, are hailed as one of the ultimate forms of next-generation batteries. Theoretically, they can fundamentally solve the safety hazards of battery thermal runaway and have the potential to break through the energy density limits of existing lithium-ion batteries. The key to achieving high performance in solid-state batteries lies in their core components, such as the cathode. This cathode is composed of a mixture of positive electrode active material and solid electrolyte, and its microstructure and composition directly determine the battery's performance. To pursue higher energy density, the mass ratio of positive electrode active material in the cathode must be increased. However, while increasing the proportion of positive electrode active material to increase energy density, it leads to a decrease in the relative content of solid electrolyte, significantly increasing the tortuosity of ion transport paths and thus impairing the "effective ionic conductivity" of the cathode. This insufficient effective ionic conductivity can cause ion transport polarization, resulting in the active material inside the cathode not being fully utilized under high current, and a decrease in the battery's rate performance. Therefore, how to achieve synergistic optimization of high energy density, high rate performance and long cycle life is the core technical challenge that solid-state batteries need to overcome. Summary of the Invention

[0003] This application provides a positive electrode, a battery, and an electrical device to at least partially solve the above-mentioned problems.

[0004] In a first aspect, this application provides a positive electrode sheet, comprising: a positive current collector; and a positive active layer disposed on at least one side of the positive current collector in the thickness direction; the positive active layer comprising a positive active material and a solid electrolyte; wherein the positive active material comprises lithium metal oxide and lithium metal sulfide.

[0005] The positive electrode sheet provided in this application introduces a solid electrolyte into the positive electrode active layer and uses a composite active material composed of lithium metal oxide and lithium metal sulfide. Through the synergistic effect of the three, a highly efficient ion and electron conduction network is constructed, which effectively reduces the solid-solid interface impedance, thereby improving the specific capacity, rate performance and cycle performance of the solid-state battery.

[0006] According to embodiments of this application, the mass ratio of the lithium metal oxide to the lithium metal sulfide is 3:1 to 19:1.

[0007] According to an embodiment of this application, the mass ratio of the positive electrode active material to the solid electrolyte is 60:40 to 90:10.

[0008] According to an embodiment of this application, the positive electrode active layer includes a plurality of positive electrode active sub-layers stacked sequentially; wherein, the positive electrode active sub-layer away from the current collector includes a lithium metal sulfide, the lithium metal oxide, and the solid electrolyte.

[0009] According to an embodiment of this application, the positive electrode active layer includes a first positive electrode active sublayer and a second positive electrode active sublayer stacked sequentially; the first positive electrode active sublayer is close to the current collector, and the second positive electrode active sublayer is located on the surface of the first positive electrode active sublayer away from the current collector; the second positive electrode active sublayer includes the lithium metal sulfide, the lithium metal oxide, and the solid electrolyte; the first positive electrode active sublayer includes the lithium metal oxide and the solid electrolyte.

[0010] According to an embodiment of this application, the positive electrode active layer satisfies: 0.32 ≤ G × D c / D P +|d1-d2|<8.57; preferably, 0.45≤G×D c / D P +|d1-d2|≤5.45; where G is the mass ratio of the lithium metal oxide to the lithium metal sulfide in the second positive electrode active sublayer; d1 is the thickness of the first positive electrode active sublayer; d2 is the thickness of the second positive electrode active sublayer; D P D represents the mass percentage of the positive electrode active material in the positive electrode active layer. C This refers to the mass percentage of the solid electrolyte in the positive electrode active layer.

[0011] According to embodiments of this application, in the second positive electrode active sublayer, the mass ratio of the lithium metal oxide to the lithium metal sulfide is 55:30 to 80:20; and / or, the thickness d1 of the first positive electrode active sublayer is ≥58 μm, the thickness d2 of the second positive electrode active coating is ≥58 μm, and |d1-d2|≤5 μm; and / or, the thickness D of the positive electrode active layer is ≥116 μm, preferably, the thickness 116 μm≤D≤126 μm; and / or, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0012] According to embodiments of this application, the solid electrolyte includes one or more of oxide solid electrolytes, sulfide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes; preferably, the solid electrolyte includes sulfide solid electrolytes and / or halide solid electrolytes.

[0013] According to embodiments of this application, the lithium-ionized metal oxide includes LiNi. x Co y M 1−x−y O2, wherein 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, wherein M is at least one of manganese or aluminum; and / or, the lithium metal sulfide includes Li x M a N 1-a S y Wherein, M and N are selected non-repeatingly from one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, niobium, copper and zinc, a≥0, and x and y are both integers greater than 0; preferably, the lithium metal sulfide includes at least one of Li2TiS2, Li2FeS2, LiMoS2, Li2TiS3, Li3NbS4, Li3CuS2 or LiVS2.

[0014] According to embodiments of this application, the active layer further includes an adhesive and / or a conductive agent; preferably, the adhesive has a mass percentage of 0.1wt% to 5wt%; and / or, the conductive agent has a mass percentage of 0.1wt% to 5wt%.

[0015] In a second aspect, this application provides a battery, including the aforementioned positive electrode; the battery is any one of a single cell, a battery module, and a battery pack. The specific capacity and rate performance of this solid-state battery are also described.

[0016] A third aspect of this application provides an electrical device comprising the battery described above. Other features and advantages of this application will be described in detail in the following detailed description section. Detailed Implementation

[0017] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0018] This application is based on the inventor's discoveries and understanding of the following facts and problems:

[0019] With the increasing urgency of electric vehicles and large-scale energy storage systems demanding high safety and high energy density, the research and development of next-generation power battery technology has become a core focus in the new energy field. Solid-state batteries, which use non-flammable solid electrolytes instead of traditional electrolytes, are hailed as one of the ultimate forms of next-generation batteries. Theoretically, they can fundamentally solve the safety hazards of battery thermal runaway and have the potential to break through the energy density limits of existing lithium-ion batteries. The key to achieving high performance in solid-state batteries lies in their core components, such as the cathode. This cathode is composed of a mixture of positive electrode active material and solid electrolyte, and its microstructure and composition directly determine the battery's performance. To pursue higher energy density, the mass ratio of positive electrode active material in the cathode must be increased. However, while increasing the proportion of positive electrode active material to increase energy density, it leads to a decrease in the relative content of solid electrolyte, significantly increasing the tortuosity of ion transport paths and thus impairing the "effective ionic conductivity" of the cathode. This insufficient effective ionic conductivity can cause ion transport polarization, resulting in the active material inside the cathode not being fully utilized under high current, leading to a decrease in the battery's rate performance and affecting cycle life. Therefore, how to achieve synergistic optimization of high energy density, high rate performance and long cycle life is the core technical challenge that solid-state batteries need to overcome.

[0020] To solve the above-mentioned technical problems, the first aspect of this application provides a positive electrode sheet.

[0021] According to an embodiment of this application, a positive electrode sheet includes: a positive current collector; a positive active layer disposed on at least one side in the thickness direction of the positive current collector; the positive active layer includes a positive active material and a solid electrolyte; wherein the positive active material includes lithium metal oxide and lithium metal sulfide.

[0022] The positive electrode provided in this application introduces a solid electrolyte into the positive electrode active layer and employs a composite active material composed of lithium metal oxide and lithium metal sulfide. Through the synergistic effect of these three materials, a highly efficient ion and electron conduction network is constructed, effectively reducing the solid-solid interface impedance and thus improving the specific capacity, rate performance, and cycle life of the solid-state battery. The reason for this is that the high voltage, stability, and relatively high conductivity of lithium metal oxide, combined with the high capacity and fast ion conduction characteristics of lithium metal sulfide, overcome the problems of slow ion and electron conduction and high interface impedance faced by single materials in solid-state battery systems, thereby achieving a comprehensive improvement in the specific capacity, rate performance, and cycle life of the solid-state battery.

[0023] Lithium-ion metal oxides are compounds whose crystal structure contains lithium (Li) ions, metallic elements (such as nickel, cobalt, manganese, iron, aluminum, titanium, vanadium, etc., and combinations thereof), and oxygen (O). Lithium ions can be reversibly extracted and inserted into this material, thereby providing the capacity required for lithium-ion batteries. In this invention, lithium-ion metal oxides include, but are not limited to, layered materials (LiCoO2, LiNi...). x Co y Mn z O2, LiNi x Co y Al z O2, 0≤x≤1, 0≤y≤1, 0≤z≤1), spinel structure materials (LiMn2O4), and lithium-rich manganese-based materials (xLi2MnO3·(1-x)LiMO2, 0<x<1), etc.

[0024] Lithium metal sulfides are compounds whose crystal structure contains lithium (Li) ions, transition metal elements (such as nickel, cobalt, manganese, iron, aluminum, titanium, vanadium, etc., and combinations thereof), and sulfur (S). Compared with oxides, sulfur ions have a larger radius and lower electronegativity; therefore, these lithium metal sulfides have the potential for higher theoretical specific capacity and better ionic conductivity. In this invention, lithium metal sulfides include, but are not limited to, Li... x M a N 1-a S y ; where M and N are selected without repetition from one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, niobium, copper and zinc, a≥0, and x and y are both integers greater than 0.

[0025] According to embodiments of this application, the mass ratio of lithium metal oxide to lithium metal sulfide is 3:1 to 19:1.

[0026] When the mass ratio of lithium metal oxide to lithium metal sulfide is within the above range, it can better improve the overall specific capacity and rate performance of solid-state batteries.

[0027] As an example, the mass ratio of lithium metal oxide to lithium metal sulfide can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or any two of them.

[0028] Specifically, the mass ratio of lithium metal oxide to lithium metal sulfide can be determined by the following method: Carefully scrape the active layer material from a very small area of ​​the cathode using a sharp tool, observe the cross-section using a scanning electron microscope (SEM), and remove residual binder using a solvent such as dimethyl carbonate. Dissolve the separated sample completely in acid and bring the volume to a suitable level to prepare the test solution. Simultaneously determine the content of elements such as Ni, Co, Mn, Ti, and S in the solution using ICP-OES. Based on the measured total molar amounts of Ni, Co, and Mn, and the XRD pattern of the cathode, determine the theoretical chemical formula of the lithium metal oxide material used (e.g., NCM811), and calculate the mass of the lithium metal oxide component. Based on the measured molar amount of Ti, and the XRD patterns of the cathode and the cathode, estimate the theoretical chemical formula of the lithium metal sulfide material used (e.g., Li2TiS3), and calculate the mass of the lithium metal sulfide component. Divide the two masses to obtain the mass ratio of lithium metal oxide to lithium metal sulfide.

[0029] According to embodiments of this application, the mass ratio of the positive electrode active material to the solid electrolyte is 60:40 to 90:10.

[0030] When the mass ratio of positive electrode active material to solid electrolyte is within the above range, it can better improve the overall performance of solid-state battery specific capacity and rate capability.

[0031] As an example, the mass ratio of the positive electrode active material to the solid electrolyte can be 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10 or any two of them.

[0032] According to an embodiment of this application, the positive electrode active layer includes a plurality of positive electrode active sublayers stacked sequentially; wherein, the positive electrode active sublayer on the side away from the current collector includes lithium metal sulfide, lithium metal oxide and solid electrolyte.

[0033] This multi-layer structure design helps to increase the overall active material loading of the positive electrode active layer, thereby increasing the specific capacity of the battery. At the same time, the active sublayer on the side away from the current collector contains lithium metal sulfide, lithium metal oxide and solid electrolyte. Through synergistic effect, the three can not only provide efficient ion transport channels, but also contribute additional capacity and cycle stability by means of the redox reaction and plasticity of lithium metal sulfide, thereby improving the energy density, rate performance and cycle performance of the all-solid-state battery.

[0034] It is understood that when the positive electrode active layer includes multiple positive electrode active sublayers, the positive electrode active sublayer on the side away from the current collector can be one or more. For example, when the positive electrode active layer includes three positive electrode active sublayers, they are sequentially arranged as a first positive electrode active sublayer, a second positive electrode active sublayer, and a third positive electrode active sublayer on the same side as the current collector, moving away from the current collector; wherein the second positive electrode active sublayer and / or the third positive electrode active sublayer includes a lithium metal sulfide, a lithium metal oxide, and a solid electrolyte. The first positive electrode active sublayer includes a lithium metal oxide and the solid electrolyte.

[0035] According to an embodiment of this application, the positive electrode active layer includes a first positive electrode active sublayer and a second positive electrode active sublayer stacked sequentially; the first positive electrode active sublayer is close to the current collector, and the second positive electrode active sublayer is located on the surface of the first positive electrode active sublayer away from the current collector; the second positive electrode active sublayer includes a lithium metal sulfide, a lithium metal oxide, and a solid electrolyte; the first positive electrode active sublayer includes the lithium metal oxide and the solid electrolyte.

[0036] When the positive electrode active layer has two layers, it can ensure that the positive electrode sheet has excellent specific capacity, rate performance, and cycle life, while also having excellent production efficiency. When the number of active sublayers is further increased, additional processes such as slurry preparation, buffering, and coating are added, resulting in increased production complexity and reduced production efficiency and electrode yield.

[0037] According to embodiments of this application, the positive electrode active layer satisfies: 0.32 ≤ G × D c / D P +|d1-d2|<8.57; where G is the mass ratio of lithium metal oxide to lithium metal sulfide in the second positive electrode active sublayer; d1 is the thickness of the first positive electrode active sublayer; d2 is the thickness of the second positive electrode active sublayer; D P D represents the mass percentage of the positive electrode active material in the positive electrode active layer. c This represents the mass percentage of the solid electrolyte in the positive electrode active layer.

[0038] By controlling the positive electrode active layer to meet the above formula range, it can be ensured that solid-state batteries can have the characteristics of long cycle life, high energy density and excellent kinetic performance under high positive electrode active material load.

[0039] As an example, the formula is: G×D c / D P +|d1-d2| can specifically be 0.32, 0.45, 0.52, 0.59, 0.66, 0.71, 0.80, 1.32, 1.88, 2.82, 3.45, 3.78, 4.33, 5.45, 6.33, 7.33, 8.45, or any two of them.

[0040] Preferably, 0.45 ≤ G × D c / D P +|d1-d2|≤5.45.

[0041] According to an embodiment of this application, in the second positive electrode active sublayer, the mass ratio of lithium metal oxide to lithium metal sulfide is 55:30 to 80:20.

[0042] By controlling the mass ratio of lithium metal oxide to lithium metal sulfide in the second positive electrode active sublayer to meet the above formula range, the energy density, rate performance and cycle performance of the all-solid-state battery can be improved.

[0043] As an example, the mass ratio of lithium metal oxide to lithium metal sulfide in the second positive electrode active sublayer can be 55:30, 61:24, 63:22, 65:20, 67:18, 68:17, 70:30, 75:25, 80:20 or any two of them.

[0044] According to an embodiment of this application, the thickness d1 of the first positive electrode active sublayer is ≥ 58 μm, the thickness d2 of the second positive electrode active coating is ≥ 58 μm, and |d1-d2|≤ 5 μm.

[0045] Generally, the thicker the positive electrode active material layer, the greater the battery capacity. However, excessive thickness of the positive electrode active material layer can increase the internal resistance of the positive electrode sheet, affecting the battery's output power and cycle life. Therefore, this invention controls d1 and d2 within a certain value range, and also controls the difference between their thicknesses within a certain range, which is beneficial for further optimizing battery performance.

[0046] As an example, the thickness d1 of the first positive electrode active sublayer can be 58μm, 59μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm or any two of them; as an example, the thickness d2 of the second positive electrode active sublayer can be 58μm, 59μm, 60μm, 61μm, 62μm, 63μm, 64μm, 65μm or any two of them; |d1-d2| can be 0μm, 1μm, 2μm, 3μm, 4μm, 5μm or any two of them.

[0047] The thickness of each active sublayer in the positive electrode sheet can be obtained by the following method: cut small pieces (5×5 mm) from the edge, center, and four corners (5 points) of the positive electrode sheet, avoiding the most significant isostatic depressions / protrusions (such as the edges which are easily crushed); use a diamond blade (no thermal damage) in a glove box, with the cut surface perpendicular to the coating direction (to ensure that the cross-section shows the upper and lower layers); embed the sample with low-temperature epoxy resin (Araldite 2020, room temperature curing), with a curing time ≤2 hours (to avoid thermal decomposition of the solid electrolyte); polish stepwise with 0.5μm diamond polishing slurry to ensure that the cross-section is free of scratches and burrs (critical: test immediately after polishing to avoid exposure to air). Thickness measurement (optical microscope + ImageJ image analysis to distinguish each active sublayer of the positive electrode) resolution ≥ 0.1 μm / pixel, 5 point cross sections were photographed (each point was repeated 3 times); second active sublayer thickness: from the positive electrode interface (where the positive electrode contacts the solid electrolyte membrane) to the current collector (interface calibrated by EDS); first active sublayer thickness: from the second active sublayer to the current collector.

[0048] According to embodiments of this application, the thickness D of the positive electrode active layer is ≥116μm, preferably 116μm≤D≤126μm; and / or, the thickness of the positive electrode current collector is 10μm~15μm.

[0049] As an example, the thickness D of the positive electrode active layer can be 116μm, 118μm, 120μm, 122μm, 124μm, 126μm or any two of them; as an example, the thickness of the positive electrode current collector can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or any two of them.

[0050] According to embodiments of this application, the solid electrolyte includes one or more of oxide solid electrolytes, sulfide solid electrolytes, and polymer solid electrolytes; preferably, the solid electrolyte includes sulfide solid electrolytes and / or chloride solid electrolytes.

[0051] Halogen solid electrolytes include Li a MX b Furthermore, 0.5 ≤ a ≤ 4.5, 2.5 ≤ b ≤ 8.5, and M is selected from one or more of the elements Mg, Ca, Sr, Ba, Zn, Al, Ga, In, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Bi, Zr, Hf, Ti, Nb, or Ta. Further, M is Y, Yb, or Zr. X is selected from one or more of F, Cl, and Br; it may also include other forms of modified novel halide solid electrolytes such as O doping.

[0052] The above-mentioned sulfide solid electrolyte is Li7-m+a-c-d M m / n P 1-a A a S 5-b D b Cl c X d (M = one or more of Na, Mg, Ca, Zn, Al; A = one or more of Si, Sn, Ge; D = one or more of O, Se; X = one or more of Br, I, 0≤m≤1, 1≤n≤3, 0≤a≤1, 0≤b≤2, 0≤c<2, 0≤d<2, 1≤c+d<2).

[0053] Oxide solid electrolytes include: garnet-type electrolytes (such as Li7La3Zr2O) 12 LLZO (Lithium-ion-ion) is a perovskite-type electrolyte (such as Li₂O� 3x La 2 / 3-x TiO3, abbreviated as LLTO), and NASICON-type electrolytes (such as Li) 1+3 Al x Ti 2-x (PO4)3, abbreviated as LATP), in addition, LISICON and its related derivatives (such as Li 14 Zn(GeO4)4, etc.

[0054] Polymer solid electrolytes are mainly composed of a polymer matrix that can dissolve lithium salts, such as polyethylene oxide and its derivatives or modifications.

[0055] According to embodiments of this application, the solid electrolyte is preferably a sulfide solid electrolyte and / or a halide solid electrolyte. Sulfide solid electrolytes and halide solid electrolytes have higher ionic conductivity and Young's modulus that is compatible with the positive electrode active material, which is more conducive to the electrochemical performance of solid-state batteries.

[0056] According to embodiments of this application, the positive electrode active material may include LiNi. x Co y M 1−x−y O2, where 0≤x≤1, 0≤y≤1, and M is at least one of manganese or aluminum. Compared to other positive electrode active materials, the above materials exhibit better ionic and electronic conductivity and are more compatible with solid-state battery systems. The above materials also include LiNi obtained through coating and / or doping modification. x Co y M 1−x−y O2.

[0057] According to embodiments of this application, the lithium metal sulfide includes Li x M a N1-a S y Wherein, M and N are selected non-repeatingly from one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, niobium, copper and zinc, a≥0, and x and y are both integers greater than 0; preferably, the lithium metal sulfide includes at least one of Li2TiS2, Li2FeS2, LiMoS2, Li2TiS3, Li3NbS4, Li3CuS2 or LiVS2.

[0058] According to embodiments of this application, the active layer further includes an adhesive and / or a conductive agent.

[0059] According to embodiments of this application, the content of the adhesive is 0.1wt% to 5wt% based on the mass of the active layer.

[0060] For example, the content of the adhesive may be 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, or any combination thereof.

[0061] According to embodiments of this application, the content of the conductive agent is 0.1wt% to 5wt% based on the mass of the active layer.

[0062] For example, the content of the conductive agent may be 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, or any combination thereof.

[0063] According to embodiments of this application, based on the mass of the active layer, the content of the adhesive and the conductive agent are each independently 0.1wt%~5wt%.

[0064] For example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), hydrogenated nitrile butadiene rubber (HNBR), natural rubber (HNR), sodium polyacrylate (SA), and polytetrafluoroethylene (PTFE).

[0065] For example, the conductive agent may include one or more of carbon nanotubes, carbon nanofibers (VGCF), conductive carbon black (CB), Ketjen black, graphene, and graphyne.

[0066] In the positive electrode sheet of this application embodiment, the content of binder and / or conductive agent is controlled within the above range, which is beneficial to further increase the adhesion between the active layer and the current collector, as well as between each active sublayer, and / or the conductivity of the positive electrode sheet; at the same time, it ensures the conductivity uniformity between the positive electrode active material and the solid electrolyte, which helps to better improve the safety of the positive electrode sheet, suppress the safety risks of solid-state batteries, and also helps to increase the electrochemical performance of solid-state batteries.

[0067] According to embodiments of this application, the positive current collector may include an aluminum foil current collector, a composite current collector, a stainless steel current collector, or a current collector with a conductive coating on the above metal carriers, and can be selected as needed.

[0068] This application does not impose any particular restrictions on the structure and manufacturing process of the positive electrode sheet, as long as the purpose of this application can be achieved.

[0069] The positive electrode sheet of this application embodiment can be prepared by wet or dry batching.

[0070] Specifically, the process includes: dispersing lithium metal sulfide, lithium metal oxide, solid electrolyte, binder and / or conductive agent in a solvent to obtain a slurry; coating the slurry onto one or both functional surfaces of the current collector and performing a pressing process to obtain the above-mentioned positive electrode sheet; wherein the pressing process is performed at a temperature of 80℃~150℃, a pressure of 100 MPa~400 MPa, and a time of 10min~30min.

[0071] If the active layer is multilayered, specifically, it includes: dispersing a lithium metal oxide, a first solid electrolyte, a first binder, and / or a first conductive agent in a solvent to obtain a first slurry; and so on, dispersing an nth lithium metal oxide, an n-1th lithium metal sulfide, an nth solid electrolyte, an nth binder, and / or an nth conductive agent in a solvent to obtain an nth slurry; coating the first slurry onto one or both functional surfaces of the current collector... and then coating the nth slurry onto the surface of the n-1th active material layer, and performing a pressing process to obtain the above-mentioned positive electrode sheet; wherein the pressing process is performed at a temperature of 80℃~150℃, a pressure of 100 MPa~400 MPa, and a time of 10 min~30 min. The lithium metal oxide, solid electrolyte, binder, and conductive agent in each slurry can be the same or different.

[0072] In practical applications, it has been found that the positive electrode sheet of the present application embodiment can be obtained by applying the above pressing treatment at a temperature of 80℃~150℃, a pressure of 100 MPa~400 MPa, and a time of 10min~30min.

[0073] For example, the temperature of the pressing process can be a range of 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or any combination thereof; the pressure of the pressing process can be a range of 100MPa, 150MPa, 200MPa, 300MPa, 350MPa, 400MPa or any combination thereof; and the time of the pressing process can be a range of 10min, 20min, 30min or any combination thereof.

[0074] According to an embodiment of this application, the above preparation process further includes: ball milling and mixing the lithium metal oxide and / or lithium metal sulfide required for each active sublayer with a solid electrolyte to obtain the raw material system required for each active sublayer; then mixing the raw material system required for each active sublayer, the conductive agent required for each active sublayer, and the binder required for each active sublayer, adding a solvent, and then stirring under the action of a vacuum mixer to obtain the positive electrode slurry required for each active sublayer; sequentially coating the positive electrode slurry required for each active sublayer onto at least one side of the positive electrode current collector, and then drying and rolling to form an active layer.

[0075] The rotational speed of the ball mill can be from 50 r / min to 150 r / min, and exemplaryly, it can be a range of 50 r / min, 60 r / min, 70 r / min, 80 r / min, 90 r / min, 100 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min, or any combination thereof. The ball milling time can be from 0.5 h to 2 h, and exemplaryly, it can be a range of 0.5 h, 0.8 h, 1 h, 1.5 h, 2 h, or any combination thereof.

[0076] In addition, drying can be carried out in an oven at a temperature of 90℃ to 95℃ for 2 to 3 hours.

[0077] Understandably, the aforementioned positive electrode slurry also includes one or more solvents, such as anisole, xylene, difluorophenyl ether, butyl butyrate, and N-methyl-2-pyrrolidone (NMP).

[0078] In the preparation process of the positive electrode sheet provided in this application embodiment, the parameters such as the amount of each substance added, average particle size, and mass ratio may deviate from the parameters such as the average particle size and mass ratio of each substance obtained from the positive electrode sheet obtained after disassembly from the battery, but they are within the error range. Therefore, the amount of each substance added and the particle size during the preparation process of the positive electrode sheet are basically consistent with the parameters such as the average particle size and mass ratio of each substance in the positive electrode active layer of the positive electrode sheet.

[0079] In practice, the pressing process described above can also be performed during the solid-state battery manufacturing process. For example, after assembling a cell consisting of a positive electrode precursor without a pressed active layer, a solid electrolyte membrane, and a negative electrode, a pressing process is performed to form a positive electrode precursor, thereby obtaining a solid-state battery including the positive electrode.

[0080] According to embodiments of this application, a battery is also provided, including the aforementioned positive electrode plate. This battery can be any of a single cell, a battery module, or a battery pack. This battery has advantages corresponding to the aforementioned positive electrode plate, which will not be elaborated further.

[0081] The battery described above is preferably a solid-state battery.

[0082] The aforementioned solid-state battery also includes a negative electrode and a solid electrolyte membrane existing between the positive and negative electrodes.

[0083] The solid-state battery of this application embodiment can be prepared using conventional methods in the art. Specifically, a positive electrode sheet can be attached to the positive electrode side of a solid electrolyte membrane, and after pressing, a negative electrode sheet (or a negative electrode precursor) can be placed on the negative electrode side of the solid electrolyte membrane, and then pressed to obtain a solid-state battery.

[0084] This application also provides an electrical device including the aforementioned solid-state battery, which serves as the power supply for the device. This device offers advantages corresponding to the aforementioned positive electrode, which will not be elaborated further.

[0085] According to embodiments of this application, the specific type of electrical equipment is not particularly limited and can be any device that uses a battery as a power source or energy storage unit. For example, electrical equipment includes, but is not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, etc.

[0086] It is understandable that, in addition to the solid-state battery mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies, such as electric vehicles, which may include the body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be elaborated here.

[0087] The present application will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0088] Example 1

[0089] 100g of a mixture of lithium niobate-coated nickel-cobalt-manganese (LNO@Ni88, lithium metal oxide), Li2TiS3 (lithium metal sulfide), sulfide electrolyte (Li6PS5Cl), conductive agent (VGCF), and binder (HNBR) were mixed in a mass ratio of 75:10:15:0.5:0.75 with xylene as the solvent and stirred until homogeneous to obtain a slurry. The slurry was coated onto the surface of a current collector in a drying chamber with a dew point of -50 to -60℃ and then dried. Following this, the material was rolled, cut, and slit to prepare the positive electrode sheet. The drying temperature was 80℃, the drying time was 10 min, and the pressing pressure was 350 MPa.

[0090] Ultimately, the thickness of the single-layer active layer prepared in this embodiment is 120 μm, the active material accounts for 84% of the total mass of the active material layer, the sulfide electrolyte accounts for 15%, and the thickness of the current collector is 12 μm.

[0091] First, 0.12g of solid electrolyte material Li6PS5Cl was placed in a mold with a diameter of 10mm and pressed into a sheet under 300MPa. Then, the positive electrode sheet (cut into a sheet with a diameter of 10mm) was placed on one side of the pressed sulfide electrolyte layer and held under pressure at 400MPa for 5min. Finally, the lithium indium negative electrode was placed on the other side of the sulfide electrolyte layer and the electrochemical performance of the battery was tested at 100MPa.

[0092] Example 2

[0093] Similar to Example 1, the difference is that the mass ratio of lithium metal oxide (LNO@Ni88) to lithium metal sulfide (Li2TiS3) in the positive electrode is 80.75:4.25.

[0094] Example 3

[0095] Similar to Example 1, the difference is that the mass ratio of lithium metal oxide (LNO@Ni88) to lithium metal sulfide (Li2TiS3) in the positive electrode is 63.75:21.25.

[0096] Example 4

[0097] Similar to Example 1, the difference is that the mass ratio of the positive electrode active material (the sum of the masses of lithium metal oxide (LNO@Ni88) and lithium metal sulfide (Li2TiS3)) to the solid electrolyte material Li6PS5Cl in the positive electrode sheet is 60:40, wherein the mass ratio of lithium metal oxide (LNO@Ni88) to lithium metal sulfide (Li2TiS3) remains unchanged.

[0098] Example 5

[0099] Similar to Example 1, the difference is that the mass ratio of the positive electrode active material (the sum of the masses of lithium metal oxide (LNO@Ni88) and lithium metal sulfide (Li2TiS3)) to the solid electrolyte material Li6PS5Cl in the positive electrode sheet is 90:10, wherein the mass ratio of lithium metal oxide (LNO@Ni88) to lithium metal sulfide (Li2TiS3) remains unchanged.

[0100] Example 6

[0101] Similar to Example 1, the difference lies in the use of a double-layer design for the positive electrode active layer. Specifically, 50g of lithium niobate-coated nickel-cobalt-manganese material (LNO@Ni88), sulfide electrolyte (Li6PS5Cl), conductive agent (VGCF), and binder (HNBR) are mixed in a mass ratio of 85:15:0.5:0.75, with xylene as the solvent, and stirred evenly to obtain the first slurry. In a drying room with a dew point of -50 to -60°C, the first slurry is wet-coated onto the current collector and dried at 90°C to form the primary first active sublayer. 50g of lithium niobate-coated nickel-cobalt-manganese material (LNO@Ni88), Li2TiS3, sulfide electrolyte (Li6PS5Cl), conductive agent (VGCF), and binder (HNBR) are mixed in a mass ratio of 61:24:15:0.5:0.75, with xylene as the solvent, and stirred evenly to obtain the second slurry. In a drying chamber with a dew point of -50 to -60°C, the second slurry is coated onto the surface of the first active sublayer and dried. Then, it is rolled, cut, and slit to prepare a positive electrode sheet containing two active sublayers. The drying temperature is 80°C, the drying time is 10 minutes, and the pressing pressure is 350 MPa.

[0102] Ultimately, in the bilayer active layer prepared in this embodiment, the thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer are both 60 μm, the absolute value of the difference between the thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer is 0, the active material accounts for 84%, and the sulfide electrolyte accounts for 15%.

[0103] Example 7

[0104] Similar to Example 6, the difference is that the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 63:22:15:0.5:0.75.

[0105] Example 8

[0106] Similar to Example 6, the difference is that the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 65:20:15:0.5:0.75.

[0107] Example 9

[0108] Similar to Example 6, the difference is that the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 67:18:15:0.5:0.75.

[0109] Example 10

[0110] Similar to Example 6, the difference is that the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 55:30:15:0.5:0.75.

[0111] Example 11

[0112] Similar to Example 6, the difference is that the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 68:17:15:0.5:0.75.

[0113] Example 12

[0114] Similar to Example 6, the difference is that the thickness d1 of the first active sublayer is 65 μm, the thickness d2 of the second active sublayer is 60 μm, and the absolute value of the difference between the thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer is 5 μm.

[0115] Example 13

[0116] Similar to Example 6, the difference is that the thickness d1 of the first active sublayer is 61 μm, the thickness d2 of the second active sublayer is 58 μm, and the absolute value of the difference between the thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer is 3 μm.

[0117] Example 14

[0118] Similar to Example 6, the difference is that the thickness d1 of the first active sublayer is 65 μm, the thickness d2 of the second active sublayer is 57 μm, and the absolute value of the difference between the thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer is 8 μm.

[0119] Example 15

[0120] Similar to Example 6, the difference lies in the interchangeability of the contents of the substances in the first and second active sublayers. Specifically, the mass ratio of LNO@Ni88, Li2TiS3, Li6PS5Cl, VGCF, and HNBR in the first active sublayer near the current collector is 61:24:15:0.5:0.75; while the mass ratio of LNO@Ni88, Li6PS5Cl, VGCF, and HNBR in the second active sublayer is 85:15:0.5:0.75. The thickness d1 of the first active sublayer and the thickness d2 of the second active sublayer are both 60 μm, and the absolute value of the difference between the thicknesses d1 and d2 is 0. The active material accounts for 84%, and the sulfide electrolyte accounts for 15%.

[0121] Comparative Example 1

[0122] Similar to Example 1, the difference is that the positive electrode active material is only lithium metal oxide, that is, a mixture of LNO@Ni88, Li6PS5Cl, VGCF and HNBR in a mass ratio of 85:15:0.5:0.75, with xylene as the solvent, and the mixture is stirred evenly to obtain a slurry.

[0123] Comparative Example 2

[0124] Similar to Example 1, the difference is that the positive electrode active material is only a lithium metal sulfide, that is, a mixture of Li2TiS3, Li6PS5Cl, VGCF and HNBR in a mass ratio of 85:15:0.5:0.75, with anisole as the solvent, and the mixture is stirred evenly to obtain a slurry.

[0125] The characteristics of the positive electrode sheets prepared according to Examples 1-15 and Comparative Examples 1-2 are shown in Table 1.

[0126] Table 1:

[0127] G <![CDATA[D p ]]> <![CDATA[D c ]]> <![CDATA[d 1（μm） ]]> <![CDATA[d 2（μm） ]]> <![CDATA[|d1-d2|]]> <![CDATA[G×D c / D P +|d1-d2|]]> Example 1 / 84% 15% / / / / Example 2 / 84% 15% / / / / Example 3 / 84% 15% / / / / Example 4 / 59% 40% / / / / Example 5 / 89% 10% / / / / Example 6 2.5 84% 15% 60 60 0 0.45 Example 7 2.9 84% 15% 60 60 0 0.52 Example 8 3.3 84% 15% 60 60 0 0.59 Example 9 3.7 84% 15% 60 60 0 0.66 Example 10 1.8 84% 15% 60 60 0 0.32 Example 11 4 84% 15% 60 60 0 0.71 Example 12 2.5 84% 15% 65 60 5 5.45 Example 13 2.5 84% 15% 61 58 3 3.45 Example 14 2.5 84% 15% 65 57 8 8.45 Example 15 / 84% 15% 60 60 0 / Comparative Example 1 / 84% 15% / / / / Comparative Example 2 / 84% 15% / / / /

[0128] Electrochemical tests were performed on the batteries prepared according to Examples 1-15 and Comparative Examples 1-2 above. The test methods are as follows, and the test results are shown in Table 2.

[0129] 1. Specific capacity test:

[0130] The battery was charged at a constant current of 0.1C to 3.7V and then stopped; it was left to stand for 10 minutes; then discharged at a constant current of 0.1C to 2V. This cycle was repeated 3 times. The discharge capacity of the third cycle was taken, and the specific capacity of the positive electrode was calculated by combining it with the amount of auxiliary material of the positive electrode.

[0131] 2. Cyclic Test: The batteries were allowed to stand at room temperature (25℃) for 10 minutes; then charged at a constant current of 0.1C to 3.7V and stopped; allowed to stand for 10 minutes; and then discharged at a constant current of 0.1C to 2V, constituting one cycle. This process was repeated, and the discharge capacity was recorded. The cycle was terminated after 100 cycles, and the capacity retention rate was calculated. The final measured capacity retention rate was the average of the capacity retention rates of the three tested batteries. The average test results are listed in Table 2. The capacity retention rate after 100 cycles = (specific capacity after 100 cycles ÷ specific capacity after initial discharge) × 100%.

[0132] 3. Rate test: The above battery was charged at room temperature (25℃) with a constant current of 0.1C to 3.7V and then discharged at a constant current of 0.1C to 2V. The charge and discharge performance was tested at 0.1C and 1C rates respectively, and the 1C / 0.1C discharge capacity retention rate was calculated.

[0133] Table 2:

[0134] First discharge specific capacity (mAh / g) Capacity retention rate (%) after 100 cycles 1C / 0.1C rate performance (%) Example 1 201.6 90.3 78.2 Example 2 200.5 89.6 76.7 Example 3 197.7 88.5 75.3 Example 4 178.9 88.3 80 Example 5 195.3 87.7 68.4 Example 6 202.8 90.8 80.5 Example 7 203.5 91.5 80.8 Example 8 203.7 91.7 81.2 Example 9 204.4 92.0 81.8 Example 10 201.8 88.7 79.3 Example 11 205.1 92.2 82.0 Example 12 205.8 92.8 82.6 Example 13 206.5 93.2 83.8 Example 14 202.2 89.8 80.2 Example 15 182 80.4 72.2 Comparative Example 1 170.3 59.2 64.5 Comparative Example 2 167.9 52 66.2

[0135] Based on the comparative examples and embodiments, it can be seen that the composite active material composed of lithium metal oxide and lithium metal sulfide constructs a highly efficient ion and electron conduction network through the synergistic effect of the three, effectively reducing the solid-solid interface impedance, thereby improving the specific capacity, rate performance and cycle performance of solid-state batteries.

[0136] In the description of this application, 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 features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0137] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0138] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0139] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A positive electrode plate, characterized in that, include: Positive current collector; A positive electrode active layer is disposed on at least one side in the thickness direction of the positive electrode current collector; The positive electrode active layer includes a positive electrode active material and a solid electrolyte; wherein the positive electrode active material includes lithium metal oxide and lithium metal sulfide.

2. The positive electrode sheet according to claim 1, characterized in that, The mass ratio of the lithium metal oxide to the lithium metal sulfide is 3:1 to 19:1; and / or, The mass ratio of the positive electrode active material to the solid electrolyte is 60:40 to 90:

10.

3. The positive electrode sheet according to claim 1 or 2, characterized in that, The positive electrode active layer includes a plurality of positive electrode active sub-layers stacked sequentially. The positive electrode active sublayer on the side away from the current collector includes the lithium metal sulfide, the lithium metal oxide, and the solid electrolyte.

4. The positive electrode sheet according to claim 3, characterized in that, The positive electrode active layer includes a first positive electrode active sublayer and a second positive electrode active layer stacked sequentially; The first positive electrode active sublayer is close to the current collector, and the second positive electrode active sublayer is located on the surface of the first positive electrode active sublayer away from the current collector; The second positive electrode active sublayer includes the lithium metal sulfide, the lithium metal oxide, and the solid electrolyte; The first positive electrode active sublayer includes the lithium metal oxide and the solid electrolyte.

5. The positive electrode sheet according to claim 4, characterized in that, The positive electrode active layer satisfies: 0.32 ≤ G × D c / D P +|d1-d2|<8.57; preferably, 0.45≤G×D c / D P +|d1-d2|≤5.45; Wherein, G is the mass ratio of the lithium metal oxide to the lithium metal sulfide in the second positive electrode active sublayer; d1 is the thickness of the first positive electrode active sublayer; d2 is the thickness of the second positive electrode active sublayer; D P D represents the mass percentage of the positive electrode active material in the positive electrode active layer. c This refers to the mass percentage of the solid electrolyte in the positive electrode active layer.

6. The positive electrode sheet according to claim 4 or 5, characterized in that, In the second positive electrode active sublayer, the mass ratio of the lithium metal oxide to the lithium metal sulfide is 55:30 to 80:20; and / or, The thickness of the first positive electrode active sublayer, d1, is ≥ 58 μm; the thickness of the second positive electrode active coating, d2, is ≥ 58 μm; and |d1 - d2| ≤ 5 μm; and / or, The thickness D of the positive electrode active layer is ≥ 116 μm, preferably, the thickness 116 μm ≤ D ≤ 126 μm; and / or, The thickness of the positive electrode current collector is 10μm to 15μm.

7. The positive electrode sheet according to any one of claims 1-6, characterized in that, The solid electrolyte includes one or more of oxide solid electrolytes, sulfide solid electrolytes, polymer solid electrolytes, and halide solid electrolytes; The active layer also includes an adhesive and / or a conductive agent; Preferably, the adhesive has a mass percentage of 0.1 wt% to 5 wt%; and / or, the conductive agent has a mass percentage of 0.1 wt% to 5 wt%. Preferably, the solid electrolyte includes a sulfide solid electrolyte and / or a halide solid electrolyte.

8. The positive electrode sheet according to any one of claims 1-7, characterized in that, The lithium metal oxide includes LiNi x Co y M 1−x−y O2, wherein 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, wherein M is at least one of manganese or aluminum; and / or, The lithium metal sulfide includes Li x M a N 1-a S y ; where M and N are selected without repetition from one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, molybdenum, niobium, copper and zinc, a≥0, and x and y are both integers greater than 0; Preferably, the lithium metal sulfide includes at least one of Li2TiS2, Li2FeS2, LiMoS2, Li2TiS3, Li3NbS4, Li3CuS2 or LiVS2.

9. A battery, characterized in that, Includes the positive electrode sheet as described in any one of claims 1-8; the battery is any one of a single cell, a battery module, and a battery pack.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.