Positive plate, preparation method thereof and all-solid-state battery

Abstract

The invention provides a positive plate, a preparation method thereof and an all-solid-state battery. The positive plate provided by the invention comprises a positive active material and a sulfide electrolyte, the particle size D50 of the positive active material is 3-5 [mu] m, and D90 is less than or equal to 8 [mu] m; the sulfide electrolyte comprises a first sulfide electrolyte and a second sulfide electrolyte, the particle size D50 of the first sulfide electrolyte is 0.5-0.9 mu m, the particle size D90 of the first sulfide electrolyte is less than or equal to 1.2 mu m, the particle size D50 of the second sulfide electrolyte is 1-1.5 mu m, the particle size D90 of the second sulfide electrolyte is less than or equal to 1.8 mu m, and the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 1: (0.1-0.5). According to the present invention, the particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte and the second sulfide electrolyte are cooperatively controlled, such that the sizes of the three material particles are reasonably matched so as to form the compact stacking structure, such that the high ionic conductivity is ensured, the ion transmission tortuosity is reduced, and the ion conduction is uniform and efficient.

Description

Technical Field

[0001] This application relates to the field of all-solid-state battery technology, and more specifically, to a positive electrode sheet, a method for preparing the same, and an all-solid-state battery. Background Technology

[0002] All-solid-state lithium batteries are considered key to next-generation energy storage technology due to their high safety and high energy density potential. Among them, all-solid-state batteries using sulfide solid electrolytes have attracted particular attention because sulfide electrolytes possess ultra-high ionic conductivity comparable to liquid electrolytes.

[0003] However, the commercial application of sulfide all-solid-state batteries still faces severe challenges, with performance bottlenecks mainly concentrated within the composite cathode. The composite cathode is a multiphase mixture composed of cathode active material, solid electrolyte, and conductive agent, and the transport of lithium ions and electrons depends entirely on the continuous and stable conductive pathways constructed between these solid components.

[0004] Currently, existing technologies often use active materials with uniform particle size distribution, solid electrolytes, and conductive agents, mechanically mixed and then pressed into shape. This results in numerous ineffective pores within the electrode, leading to sparse solid-solid contact points and a small contact area. Ion and electron transport paths become tortuous and discontinuous, especially during high-rate charge-discharge cycles, causing a sharp increase in interfacial impedance, significant battery polarization, and poor rate performance. Furthermore, during long-cycle periods, volume changes in the active material further deteriorate the already fragile solid-solid contact, leading to interfacial contact failure and rapid capacity decay.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The main objective of this application is to provide a positive electrode sheet, its preparation method, and an all-solid-state battery, in order to solve the problems in the prior art where the positive electrode sheet obtained by mechanically mixing and pressing active materials, solid electrolytes, and conductive agents with uniform particle size distribution has a large number of ineffective pores inside, resulting in few solid-solid contact points and small contact area, poor rate performance, and rapid capacity decay during long-cycle cycling.

[0007] To achieve the above objectives, according to one aspect of this application, a positive electrode sheet is provided, comprising a positive current collector and a positive active material layer attached to the surface of the positive current collector. The positive active material layer comprises a positive active material, a sulfide electrolyte, a binder, and a conductive agent. The positive active material has a particle size D50 of 3-5 μm and a D90 ≤ 8 μm. The sulfide electrolyte comprises a first sulfide electrolyte and a second sulfide electrolyte. The first sulfide electrolyte has a particle size D50 of 0.5-0.9 μm and a D90 ≤ 1.2 μm, and the second sulfide electrolyte has a particle size D50 of 1-1.5 μm and a D90 ≤ 1.8 μm. The mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 1:(0.1-0.5).

[0008] Furthermore, the conductive agent is a composite conductive agent, which includes a first conductive agent and a second conductive agent; wherein the first conductive agent is a one-dimensional material and / or a two-dimensional material; the second conductive agent is a zero-dimensional material, and the mass ratio of the first conductive agent to the second conductive agent is 100:(20-50).

[0009] Furthermore, the first conductive agent includes at least one of VGCF, CNTs, graphene, and SWCNT.

[0010] Furthermore, the second conductive agent includes at least one of acetylene black, SuperP, and Ketjen black.

[0011] Furthermore, the positive electrode active material includes at least one of NCM and NCA.

[0012] Furthermore, the first sulfide electrolyte and the second sulfide electrolyte are each independently selected from at least one of LPSC, LPGS, and LPS.

[0013] Furthermore, the adhesive includes at least one of hydrogenated nitrile rubber, styrene-butadiene rubber, polyisobutylene, polyurethane, polyvinylidene fluoride, and hydrogenated styrene-butadiene-styrene block copolymer.

[0014] Furthermore, in the positive electrode active material layer, the mass content of the positive electrode active substance is 60%-86%, the mass content of the sulfide electrolyte is 13%-35%, the mass content of the conductive agent is 0.1%-3%, and the mass content of the binder is 0.8%-2%.

[0015] In a second aspect of this application, a method for preparing the above-mentioned positive electrode sheet is also provided. The method includes: providing a positive electrode current collector; dispersing a positive electrode active material, a sulfide electrolyte, a binder, and a conductive agent in an organic solvent to form a positive electrode active slurry; coating the positive electrode active slurry onto the surface of the positive electrode current collector; drying and rolling to obtain a positive electrode sheet.

[0016] Furthermore, the solid content of the positive electrode active slurry is 65wt%-75wt%.

[0017] Furthermore, the organic solvent is a non-polar organic solvent or a weakly polar organic solvent, preferably including at least one of xylene, anisole, alkanes, and ester solvents.

[0018] Furthermore, the drying temperature is 60℃-120℃, and the drying time is 1h-3h.

[0019] Furthermore, the pressure of the roller is 0.5MPa-3MPa.

[0020] According to a third aspect of this application, an all-solid-state battery is also provided, comprising the positive electrode sheet provided in the first aspect above or the positive electrode sheet obtained according to the preparation method provided in the second aspect above.

[0021] By applying the technical solution of this application, the positive electrode sheet provided by this application achieves a dense packing structure by synergistically controlling the particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, so that the particle sizes of the three materials are reasonably matched. This not only ensures high ionic conductivity, but also significantly reduces the tortuosity of ion transport and increases the contact area between solid and solid interfaces, making the interfacial ion conduction more uniform and efficient.

[0022] Furthermore, the positive electrode sheet provided in this application achieves three-level particle size matching through the average particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte. This reduces ineffective pores inside the positive electrode sheet, increases solid-solid contact points and contact area, shortens ion and electron transport paths, reduces the internal resistance and polarization of the electrode, and is more conducive to increasing the loading of positive electrode active material on the positive electrode sheet, thereby improving the rate performance, energy density, and cycle performance of the all-solid-state battery. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 A schematic diagram of the structure of the positive electrode sheet provided according to Embodiment 1 of this application is shown; and

[0025] Figure 2 A schematic diagram of the structure of an all-solid-state battery provided in some embodiments of this application is shown.

[0026] The above figures include the following reference numerals:

[0027] 11. Positive current collector; 12. Positive active material; 13. First sulfide electrolyte; 14. Second sulfide electrolyte; 15. First conductive agent; 16. Second conductive agent; 21. Positive electrode sheet; 22. Electrolyte layer; 23. Negative electrode sheet. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0029] As described in the background section of this application, existing technologies use active materials with uniform particle size distribution, solid electrolytes, and conductive agents, which are mechanically mixed and then pressed into shape. This results in a large number of ineffective pores inside the electrode, few solid-solid contact points, and a small contact area. The particle size distribution for ion and electron transport is tortuous and discontinuous. Especially during high-rate charge and discharge, the interfacial impedance increases, the battery polarization is significant, and the rate performance is poor. Furthermore, during long-cycle operation, the volume change of the active material further deteriorates, leading to interfacial contact failure and rapid capacity decay. To solve the above problems, this application provides a positive electrode sheet, its preparation method, and an all-solid-state battery.

[0030] In one typical embodiment of this application, a positive electrode sheet is provided, which includes a positive current collector and a positive active material layer attached to the surface of the positive current collector. The positive active material layer includes a positive active material, a sulfide electrolyte, a binder, and a conductive agent. The positive active material has a D50 of 3-5 μm and a D90 ≤ 8 μm. The sulfide electrolyte includes a first sulfide electrolyte and a second sulfide electrolyte. The first sulfide electrolyte has a D50 of 0.5-0.9 μm and a D90 ≤ 1.2 μm, and the second sulfide electrolyte has a D50 of 1-1.5 μm and a D90 ≤ 1.8 μm. The mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 1:(0.1-0.5).

[0031] The positive electrode sheet provided in this application achieves a dense packing structure by synergistically controlling the average particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, thereby ensuring a reasonable matching of particle sizes. This not only guarantees high ionic conductivity but also significantly reduces the tortuosity of ion transport and increases the contact area between solid and solid interfaces, making interfacial ion conduction more uniform and efficient.

[0032] Furthermore, the positive electrode sheet provided in this application achieves three-level particle size matching through the average particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte. This reduces ineffective pores inside the electrode, increases solid-solid contact points and contact area, shortens ion and electron transport paths, reduces the internal resistance and polarization of the electrode, and is more conducive to increasing the loading of positive electrode active material on the positive electrode sheet, thereby improving the rate performance, energy density, and cycle performance of the all-solid-state battery.

[0033] In this application, the D50 of the positive electrode active material is 3.0 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.5 μm, 4.6 μm, 4.8 μm, 5.0 μm, or any combination of two values; the maximum value of the D90 of the positive electrode active material can be 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, or 8 μm; the D50 of the first sulfide electrolyte is 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or any combination of two values; the maximum value of the D90 of the first sulfide electrolyte can be 1.0 μm, 1.05 μm, or any combination of two values. The first sulfide electrolyte has a D50 of 1.0 μm, 1.1 μm, 1.15 μm, 1.2 μm, or any two of these values; the second sulfide electrolyte has a D90 of 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any two of these values; the second sulfide electrolyte has a maximum D90 of 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, or any two of these values; the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or any two of these values.

[0034] In traditional cathode materials, conductive agents often employ single conductive carbon materials such as zero-dimensional Super P. The contact between these materials and the active material is essentially point contact, and they are prone to agglomeration during mixing. In some areas, the enrichment of conductive agent creates electron "short-circuit" paths, while in other areas, the lack of conductive agent creates "islands" of electron transport, making it difficult to form a uniform and efficient electron conduction network between active material particles. This results in low utilization of the active material and an overall electronic conductivity far below theoretical expectations. The random distribution of agglomerated conductive agent clumps physically blocks ion channels, increasing the tortuosity of ion transport. This blocking effect on ion paths, combined with the uneven electron network, leads to significant polarization within the composite electrode, especially during high-rate charge and discharge, where battery voltage polarization increases sharply and capacity decays rapidly.

[0035] In some embodiments of this application, the conductive agent is a composite conductive agent, which includes a first conductive agent and a second conductive agent. The first conductive agent is a one-dimensional material and / or a two-dimensional material, the second conductive agent is a zero-dimensional material, and the mass ratio of the first conductive agent to the second conductive agent is 100:(20-50).

[0036] By employing a first conductive agent with a one-dimensional and / or two-dimensional material structure and a second conductive agent with a zero-dimensional material structure in combination as a composite conductive agent, a synergistic conductive mechanism is formed inside the electrode. The one-dimensional / two-dimensional material achieves long-range efficient conduction within the electrode range, while the zero-dimensional material fills the gaps and enhances the point contact between the positive electrode active material particles. This helps to improve the problem of single conductive agent agglomeration and the electron transport bottleneck caused by low point contact efficiency during the preparation process.

[0037] Furthermore, this application optimizes the intrinsic properties and microstructure of the materials by controlling the D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, and by using the aforementioned composite conductive agent. This enables the construction of a highly efficient, stable, and non-interfering dual continuous network of ions and electrons within the electrode, thereby reducing the overall impedance of the electrode and improving the overall electrochemical performance of the sulfide all-solid-state battery.

[0038] In the above-mentioned composite conductive agent, the mass ratio of the first conductive agent and the second conductive agent is 100:20, 100:25, 100:30, 100:35, 100:40, 100:45, 100:50 or any range of two values.

[0039] The first conductive agent mentioned above is a conductive material commonly used in the field with a one-dimensional and / or two-dimensional structure, including but not limited to any one or more of VGCF (vapor-grown carbon fiber), CNTs (carbon nanotubes), graphene, and SWCNT (graphene nanotubes).

[0040] The aforementioned second conductive agent is a commonly used conductive agent material with a zero-dimensional structure in the art, including but not limited to any one or more of acetylene black, Super P, and Ketjen black.

[0041] In the positive electrode sheet provided in this application, the positive electrode active material is a commonly used positive electrode active material in the art, including but not limited to any one or more of NCM (lithium nickel cobalt manganese oxide) and NCA (lithium nickel cobalt aluminum oxide).

[0042] In the positive electrode provided in this application, the first sulfide electrolyte and the second sulfide electrolyte are both commonly used solid electrolytes in the art, including but not limited to any one or more of LPSC (Li2S-P2S5-C), LPGS (Li2S-P2S5-GeS2) and LPS (Li2S-P2S5).

[0043] In the positive electrode sheet provided in this application, the binder is a commonly used binder in the art, including but not limited to any one or more of hydrogenated nitrile rubber, styrene-butadiene rubber, polyisobutylene, polyurethane, polyvinylidene fluoride, and hydrogenated styrene-butadiene-styrene block copolymer.

[0044] To further improve the energy density and cycle stability of the positive electrode, the preferred positive electrode active material layer contains 60%-86% by mass of positive electrode active material, 13%-35% by mass of sulfide electrolyte, 0.1%-3% by mass of conductive agent, and 0.8%-2% by mass of binder.

[0045] Specifically, in the positive electrode active material layer provided in this application, the mass content of the positive electrode active material can be 60%, 62%, 65%, 68%, 70%, 72%, 75%, 80%, 82%, 85%, 86%, or any two of these values; the mass content of the sulfide electrolyte can be 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, or any two of these values; the mass content of the conductive agent can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 3%, or any two of these values; and the mass content of the binder can be 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2%, or any two of these values.

[0046] In some embodiments of this application, the positive current collector is a commonly used positive current collector in the art, such as aluminum foil.

[0047] In a second typical embodiment of this application, a method for preparing the above-mentioned positive electrode sheet is provided. The method includes: providing a positive electrode current collector; dispersing a positive electrode active material, a sulfide electrolyte, a binder, and a conductive agent in an organic solvent to form a positive electrode active slurry; coating the positive electrode active slurry onto the surface of the positive electrode current collector; drying and rolling to obtain a positive electrode sheet.

[0048] The method for preparing the positive electrode sheet provided in this application is applicable to large-scale production and is more conducive to further reducing costs.

[0049] The specific types of organic solvents mentioned above are not limited, and any commonly used organic solvents in the art are acceptable. In order to further improve the dispersion efficiency of each component in the positive electrode active material layer in the organic solvent, it is preferred that the organic solvent is a non-polar organic solvent or a weakly polar organic solvent, and it is further preferred that the organic solvent includes any one or more of xylene, anisole, alkanes, and ester solvents.

[0050] The alkanes mentioned above include methane, ethane, propane, etc. The ester solvents mentioned above include ethyl acetate, propyl acetate, butyl acetate, etc.

[0051] In some embodiments of this application, the solid content of the positive electrode active slurry is 65wt%-75wt% to facilitate uniform coating of the positive electrode active slurry on the positive electrode current collector. Specifically, the solid content of the positive electrode active slurry can be 65wt%, 68wt%, 70wt%, 72wt%, 75wt%, or any range of two values.

[0052] In some specific embodiments, in order to improve drying efficiency while enhancing the uniformity of the positive electrode active material layer, the preferred drying temperature is 60℃-120℃, and the drying time is 1h-3h. Specifically, the drying temperature can be 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, or any range of two values, and the drying time can be 1h, 1.5h, 2h, 2.5h, 3h, or any range of two values.

[0053] In some specific embodiments, to further improve the compaction density of the positive electrode active material lamination, the rolling pressure is preferably 0.5MPa-3MPa. Specifically, the rolling pressure is a range of 0.5MPa, 0.8MPa, 1.0MPa, 1.2MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, or any two of these values.

[0054] In some specific embodiments, when the conductive agent is a composite conductive agent, the preparation method of the above-mentioned positive electrode active slurry includes the following steps:

[0055] Step S1: Disperse the first conductive agent and the second conductive agent in an organic solvent to obtain a composite conductive agent slurry;

[0056] Step S2: Mix the positive electrode active material, the first sulfide electrolyte, the second sulfide electrolyte, the binder, and the composite conductive agent slurry evenly, and add an appropriate amount of organic solvent to obtain the positive electrode active slurry.

[0057] To further improve the preparation efficiency of the composite conductive agent slurry, it is preferable to mix and disperse the first and second conductive agents in an organic solvent using ultrasound. Specifically, the ultrasonic mixing power is 500-2000W, the ultrasonic mixing time is 10-90 minutes, a pulse mode is used, and the dispersion temperature is controlled between 25℃ and 40℃. The ultrasonic preparation method is simple and easy to operate, and can achieve efficient dispersion of the composite conductive agent.

[0058] To further improve the preparation efficiency of the above-mentioned positive electrode active slurry, it is preferable that the preparation of the positive electrode active slurry also includes a stirring process. The stirring process can be a degassing machine, a vacuum mixer, etc., such as a vacuum mixer with a stirring speed of 500 r / min-3000 r / min.

[0059] In a third typical embodiment of this application, an all-solid-state battery is also provided, which includes the positive electrode sheet provided in the first typical embodiment or the positive electrode sheet obtained according to the preparation method provided in the second typical embodiment.

[0060] The all-solid-state battery provided in this application adopts the positive electrode sheet provided in the first typical embodiment described above. By synergistically controlling the average particle size D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, the sizes of the three materials are reasonably matched to form a dense packing structure. This not only ensures high ionic conductivity but also significantly reduces the tortuosity of ion transport and increases the contact area between solid and solid interfaces, making the interfacial ion conduction more uniform and efficient.

[0061] In some embodiments, such as Figure 2 As shown, the all-solid-state battery includes a positive electrode 21, a negative electrode 23, and an electrolyte layer 22 located between the positive electrode 21 and the negative electrode 23, wherein the positive electrode 21 is the positive electrode provided in the first typical embodiment of this application.

[0062] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0063] Example 1

[0064] This embodiment provides a positive electrode, such as Figure 1 As shown, the positive electrode includes a positive current collector 11 (aluminum foil), on which a positive active material layer is attached. The positive active material layer includes a positive active material 12, a sulfide electrolyte, a conductive agent, and a binder in a mass ratio of 80:16:2:2. The positive active material is NCM811 with D50 = 4 μm and D90 ≤ 7 μm. The sulfide electrolyte includes a first sulfide electrolyte 13 and a second sulfide electrolyte 14 in a mass ratio of 7:1. The first sulfide electrolyte is LPSC with D50 = 0.7 μm and D90 ≤ 1 μm; the second sulfide electrolyte is LPSC with D50 = 1.1 μm and D90 ≤ 1.3 μm. The conductive agent includes a first conductive agent 15 and a second conductive agent 16 in a mass ratio of 3:1. The first conductive agent 15 is VGCF, and the second conductive agent 16 is Super... P; The binder is SEBS (polystyrene-ethylene-butene copolymer, purchased from Kuraray Co., Ltd., Japan, model number 4055).

[0065] The positive electrode sheet is prepared according to the following steps:

[0066] (1) The first conductive agent particles VGCF and the second conductive agent particles SP were added to xylene solvent at a mass ratio of 3:1 and ultrasonically premixed. The ultrasonic power was 1500W, the temperature was controlled at 25℃, and the ultrasonic time was 1h to obtain a uniformly dispersed composite conductive agent slurry with a solid content of 10wt%.

[0067] (2) The positive electrode active material (NCM811, D50=4μm, D90≤7μm), sulfide electrolyte (a mixture of the first sulfide electrolyte and the second sulfide electrolyte, with a mass ratio of 7:1, the first sulfide electrolyte being LPSC, D50=0.7μm, D90≤1μm; the second sulfide electrolyte being LPSC, D50=1.1μm, D90≤1.3μm), binder SEBS, and the composite conductive agent slurry prepared in step (1) (based on the mass of the composite conductive agent) are added to the tank in a mass ratio of 80:16:2:2. Xylene solvent is added, and the mixture is stirred by a degassing machine at a speed of 2000 r / min for 20 min to obtain a uniformly stirred positive electrode active slurry with a solid content of 70 wt%.

[0068] (3) The positive electrode active slurry is uniformly coated on aluminum foil, dried at 100°C for 12 hours, and then rolled into slices to obtain the positive electrode sheet, wherein the rolling pressure is 1 MPa.

[0069] Example 2

[0070] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 11:5.

[0071] Example 3

[0072] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 13:3.

[0073] Example 4

[0074] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 10:1.

[0075] Example 5

[0076] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 10:5.

[0077] Example 6

[0078] The difference from Example 1 is that the positive electrode active material NCM811 has a D50 of 3 μm and a D90 of ≤ 5 μm; the first sulfide electrolyte LPSC has a D50 of 0.9 μm and a D90 of ≤ 1.2 μm; and the second sulfide electrolyte LPSC has a D50 of 1 μm and a D90 of ≤ 1.2 μm.

[0079] Example 7

[0080] The difference from Example 1 is that the positive electrode active material NCM811 has a D50 of 5 μm and a D90 of ≤ 8 μm; the first sulfide electrolyte LPSC has a D50 of 0.5 μm and a D90 of ≤ 0.8 μm; and the second sulfide electrolyte LPSC has a D50 of 1.5 μm and a D90 of ≤ 1.8 μm.

[0081] Example 8

[0082] The difference from Example 1 is that the mass ratio of the first conductive agent to the second conductive agent is 100:20.

[0083] Example 9

[0084] The difference from Example 1 is that the mass ratio of the first conductive agent to the second conductive agent is 100:50.

[0085] Example 10

[0086] The difference from Example 1 is that the mass ratio of the first conductive agent to the second conductive agent is 100:10.

[0087] Example 11

[0088] The difference from Example 1 is that the mass ratio of the first conductive agent to the second conductive agent is 100:60.

[0089] Example 12

[0090] The difference from Example 1 is that the conductive agent is the first conductive agent, and no second conductive agent is added.

[0091] Example 13

[0092] The difference from Example 1 is that the conductive agent is the second conductive agent, and the first conductive agent is not added.

[0093] Example 14

[0094] The difference from Example 1 is that the mass ratio of the positive electrode active material, sulfide electrolyte, conductive agent and binder is 60:35:3:2.

[0095] Example 15

[0096] The difference from Example 1 is that conductive particles SWCNT are used instead of conductive particles VGCF as the first conductive agent, and the mass ratio of positive electrode active material, sulfide electrolyte, conductive agent and binder is 86:13.1:0.1:0.8.

[0097] Comparative Example 1

[0098] The difference from Example 1 is that the sulfide electrolyte is the first sulfide electrolyte, and no second sulfide electrolyte is added.

[0099] Comparative Example 2

[0100] The difference from Example 1 is that the sulfide electrolyte is the second sulfide electrolyte, and the first sulfide electrolyte is not added.

[0101] Comparative Example 3

[0102] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 10:0.05.

[0103] Comparative Example 4

[0104] The difference from Example 1 is that the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 10:8.

[0105] Comparative Example 5

[0106] The difference from Example 1 is that the positive electrode active material NCM811 has a D50 of 6 μm and a D90 ≤ 8 μm.

[0107] Comparative Example 6

[0108] The difference from Example 1 is that the first sulfide electrolyte LPSC has a D50 of 0.3 μm and a D90 ≤ 0.6 μm.

[0109] Comparative Example 7

[0110] The difference from Example 1 is that the first sulfide electrolyte LPSC has a D50 of 2 μm and a D90 ≤ 2.5 μm.

[0111] Test case

[0112] The positive electrode sheets provided in the above embodiments and comparative examples were assembled into mold half-cells in a glove box in sequence with the electrolyte layer (material LPSC) and the Li / In layer (lithium sheet and indium sheet physically bonded and pressed together), and electrochemical tests were performed:

[0113] (1) First-cycle charge and discharge performance: The battery was charged to 3.7V at 0.1C and the first-cycle charge specific capacity A0 was recorded; then it was discharged to 1.9V at 0.1C and the first-cycle discharge specific capacity A1 was recorded. The first-cycle efficiency A1 / A0 of the battery was used to represent the first-cycle charge and discharge performance of the battery. The results are shown in Table 1.

[0114] (2) Rate performance: The battery is first charged to 3.7V at 0.1C, then discharged to 1.9V at 0.1C. The discharge specific capacity is recorded as B0. Then it is charged to 3.7V at 0.1C and discharged to 1.9V at 1C. The discharge specific capacity is recorded as B1. The rate performance is expressed as the capacity retention rate of 1C / 0.1C, i.e., B1 / B0. Expressed as 100%, the results are shown in Table 1.

[0115] (3) Cycling performance: The battery was charged to 3.7V at 0.5C and then discharged to 1.9V at 0.5C. After 100 cycles, the discharge specific capacity of the 3rd cycle was recorded as C0 and the discharge specific capacity of the 100th cycle was recorded as C1. The cycle performance of the 3rd cycle was expressed as the capacity retention rate after 100 cycles, i.e., C1 / C0. Expressed as 100%, the results are shown in Table 1.

[0116] Table 1

[0117]

[0118] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0119] As can be seen from the comparison between Examples 1-15 and Comparative Examples 1-7, the positive electrode sheet provided in this application achieves three-level particle size matching through the average particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte. This reduces the ineffective pores inside the positive electrode sheet, increases the solid-solid contact points and contact area, shortens the ion and electron transport paths, reduces the internal resistance and polarization of the electrode, and is more conducive to increasing the loading of the positive electrode active material on the positive electrode sheet, thereby improving the rate performance, energy density, and cycle performance of the all-solid-state battery.

[0120] A comparison of Examples 1-9 and Examples 14-15 with Examples 10-13 shows that the positive electrode sheet provided in this application achieves three-level particle size matching through the average particle sizes D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, and controls the mass ratio of the first conductive agent to the second conductive agent to be 100:(20-50), which is more conducive to improving the rate performance, energy density, and cycle performance of the all-solid-state battery.

[0121] As can be seen from the comparison between Examples 1-9 and Comparative Examples 1-4, the positive electrode sheet provided in this application achieves three-level particle size matching through the average particle size D50 and D90 of the positive electrode active material, the first sulfide electrolyte, and the second sulfide electrolyte, and controls the mass ratio of the first sulfide electrolyte to the second sulfide electrolyte to be 1:(0.1-0.5), which is more conducive to improving the rate performance, energy density and cycle performance of the all-solid-state battery.

[0122] A comparison of Examples 1-9 with Comparative Examples 1-4 shows that the positive electrode sheet provided in this application achieves better rate performance, energy density, and cycle performance of the all-solid-state battery by controlling the particle size of the positive electrode active material to be 3-5 μm and D90≤8 μm; the particle size of the first sulfide electrolyte to be 0.5-0.9 μm and D90≤1.2 μm; and the particle size of the second sulfide electrolyte to be 1-1.5 μm and D90≤1.8 μm through a three-level particle size matching.

[0123] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer attached to the surface of the positive current collector. The positive active material layer includes a positive active material, a sulfide electrolyte, a binder, and a conductive agent. The particle size D50 of the positive active material is 3-5 μm, and D90 ≤ 8 μm. The sulfide electrolyte includes a first sulfide electrolyte and a second sulfide electrolyte. The particle size D50 of the first sulfide electrolyte is 0.5-0.9 μm, and D90 ≤ 1.2 μm. The particle size D50 of the second sulfide electrolyte is 1-1.5 μm, and D90 ≤ 1.8 μm. The mass ratio of the first sulfide electrolyte to the second sulfide electrolyte is 1:(0.1-0.5).

2. The positive electrode sheet according to claim 1, characterized in that, The conductive agent is a composite conductive agent, which includes a first conductive agent and a second conductive agent. The first conductive agent is a one-dimensional material and / or a two-dimensional material; the second conductive agent is a zero-dimensional material, and the mass ratio of the first conductive agent to the second conductive agent is 100:(20-50).

3. The positive electrode sheet according to claim 2, characterized in that, The first conductive agent includes at least one of VGCF, CNTs, graphene, and SWCNT; And / or, the second conductive agent includes at least one of acetylene black, Super P, and Ketjen black.

4. The positive electrode sheet according to claim 1, characterized in that, The positive electrode active material includes at least one of NCM and NCA; And / or, the first sulfide electrolyte and the second sulfide electrolyte are each independently selected from at least one of LPSC, LPGS, and LPS.

5. The positive electrode sheet according to claim 1, characterized in that, The adhesive includes at least one of hydrogenated nitrile rubber, styrene-butadiene rubber, polyisobutylene, polyurethane, polyvinylidene fluoride, and hydrogenated styrene-butadiene-styrene block copolymer.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that, In the positive electrode active material layer, the mass content of the positive electrode active substance is 60%-86%, the mass content of the sulfide electrolyte is 13%-35%, the mass content of the conductive agent is 0.1%-3%, and the mass content of the binder is 0.8%-2%.

7. The method for preparing the positive electrode sheet according to any one of claims 1 to 6, characterized in that, The preparation method includes: providing a positive electrode current collector; dispersing a positive electrode active material, a sulfide electrolyte, a binder, and a conductive agent in an organic solvent to form a positive electrode active slurry; coating the positive electrode active slurry onto the surface of the positive electrode current collector; drying and rolling to obtain the positive electrode sheet.

8. The preparation method according to claim 7, characterized in that, The solid content of the positive electrode active slurry is 65wt%-75wt%; And / or, the organic solvent is a nonpolar organic solvent or a weakly polar organic solvent, preferably including at least one of xylene, anisole, alkanes, and ester solvents.

9. The preparation method according to claim 7, characterized in that, The drying temperature is 60℃-120℃, and the drying time is 1h-3h; And / or, the pressure of the roller is 0.5MPa-3MPa.

10. An all-solid-state battery, characterized in that, The all-solid-state battery includes the positive electrode sheet according to any one of claims 1 to 6 or the positive electrode sheet obtained by the preparation method according to any one of claims 7 to 9.

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