Pole piece, preparation method thereof and solid-state battery

Abstract

The invention provides a pole piece, a preparation method of the pole piece and a solid-state battery. The solid-solid contact effect between a solid electrolyte and an active material in the pole piece is improved. The pole piece comprises a current collector and an active material layer arranged on the current collector, the active material layer comprises a plurality of sub-active material layers which are sequentially stacked, each sub-active material layer comprises an active material, and the compaction density of each sub-active material layer is larger than or equal to 2.50 g / cm < 3 >; the multiple sub-active material layers comprise a first sub-active material layer and a second sub-active material layer which are sequentially arranged in the direction away from the current collector, the first sub-active material layer further comprises a first solid electrolyte, and the second sub-active material layer further comprises a second solid electrolyte; the average particle size D2 of the second solid electrolyte is larger than the average particle size D1 of the first solid electrolyte, and the mass content W1 of the first solid electrolyte in the first sub active material layer is larger than the mass content W2 of the second solid electrolyte in the second sub active material layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a pole piece, a preparation method thereof and a solid-state battery. BACKGROUND

[0002] The solid-state lithium ion battery (referred to as solid-state battery) uses a solid-state electrolyte to replace the separator and electrolyte in the traditional lithium ion battery, which significantly reduces the risk of spontaneous combustion and explosion of the solid-state lithium ion battery, and the solid-state electrolyte does not decompose obviously at high temperature, has the advantages of high safety and wide working temperature range; and the solid-state electrolyte is difficult to leak and volatilize, and the electrolyte does not dry out during long-term cycling, so the cycle life and calendar life of the battery are long; in addition, the energy density of the solid-state lithium ion battery with a lithium metal negative electrode or a pure silicon negative electrode can exceed 400 Wh / kg. Therefore, the solid-state lithium ion battery with the advantages of high safety, high energy density and long calendar life is considered to be the development direction of future lithium batteries, and the development of the solid-state lithium ion battery has attracted widespread attention.

[0003] Due to the lack of electrolyte in the solid-state battery, in order to build a good lithium ion channel in the electrode, a solid-state electrolyte is usually added in the electrode, but the solid-state electrolyte itself does not provide energy density, and the addition of the solid-state electrolyte in the electrode will sacrifice the energy density, so the realization of high energy density of the solid-state battery depends on the design of thick electrodes. However, the thick electrode has the problem of difficulty in densification, which leads to the problem of solid-solid contact failure between the solid-state electrolyte and the active material in the thick electrode, thereby affecting the electrochemical performance of the solid-state battery. SUMMARY

[0004] Embodiments of the present application provide a pole piece, a preparation method thereof and a solid-state battery, which can improve the effect of solid-solid contact between the solid-state electrolyte and the active material in the pole piece.

[0005] In a first aspect, embodiments of the present application provide a pole piece, which comprises: a current collector and an active material layer arranged on the current collector, the active material layer comprising a plurality of sub-active material layers arranged in sequence, the sub-active material layer comprising an active material and the compaction density of the sub-active material layer being greater than or equal to 2.50 g / cm 3 ; the plurality of sub-active material layers comprise a first sub-active material layer and a second sub-active material layer arranged in sequence away from the current collector, the first sub-active material layer further comprising a first solid-state electrolyte, the second sub-active material layer further comprising a second solid-state electrolyte, the average particle size D2 of the second solid-state electrolyte being greater than the average particle size D1 of the first solid-state electrolyte, and the mass content W1 of the first solid-state electrolyte in the first sub-active material layer being greater than the mass content W2 of the second solid-state electrolyte in the second sub-active material layer.

[0006] In an embodiment, the multi-layered sub-active material layer further comprises a third sub-active material layer disposed on a side of the second sub-active material layer away from the first sub-active material layer, the third sub-active material layer comprising a third solid-state electrolyte, an average particle size D2 of the second solid-state electrolyte being greater than an average particle size D3 of the third solid-state electrolyte, a mass content W1 of the first solid-state electrolyte in the first sub-active material layer being greater than a mass content W3 of the third solid-state electrolyte in the third sub-active material layer.

[0007] In an embodiment, the active material comprises a cathode active material, the cathode active material comprising at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, and lithium-rich manganese-based material.

[0008] In an embodiment, the cathode active material is coated with a coating layer, the coating layer comprising at least one of Li3PO4, LiNbO3, Li4Ti5O2, Li2ZrO3, and Li3BO3.

[0009] In an embodiment, the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer each further comprise an electrically conductive agent and a binder.

[0010] In an embodiment, the binder comprises at least one of polytetrafluoroethylene, butadiene rubber, butyronitrile rubber, polyvinylidene fluoride, polyisobutylene, hydrogenated butyronitrile rubber, styrene-butadiene-styrene block copolymer, and hydrogenated styrene-butadiene block copolymer.

[0011] In an embodiment, the mass content of the binder in the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer is 0.5wt% to 10wt%.

[0012] In an embodiment, the electrically conductive agent comprises at least one of electrically conductive carbon black, carbon nanotube, carbon nanofiber, graphite, and graphene.

[0013] In an embodiment, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte each independently comprises at least one of sulfide solid-state electrolyte, halide solid-state electrolyte, and oxide solid-state electrolyte.

[0014] In an embodiment, the sulfide solid-state electrolyte comprises Li 7-a PS 6-a X a , Li3PS4, Li4SnS4, 75Li2S-25P2S5, Li7SiPS8, and Li 10 GeP2S12 At least one of the following, wherein X is a halogen element and a is 0.8 to 2.0.

[0015] In one embodiment, the halide solid electrolyte includes Li b MY4, Li b MY6, Li b MY8, and at least one of a halide oxide electrolyte, wherein M is an alkali metal element and Y is a halogen element.

[0016] In one embodiment, the oxide solid electrolyte includes at least one of a garnet-type oxide solid electrolyte, a NASICON-type oxide solid electrolyte, and a perovskite-type oxide solid electrolyte.

[0017] In one embodiment, the average particle size D1 of the first solid electrolyte is 0.2 μm to 20 μm.

[0018] In one embodiment, the average particle size D2 of the second solid electrolyte is 0.5 μm to 20 μm.

[0019] In one embodiment, the average particle size D3 of the third solid electrolyte is 0.5 μm to 10 μm.

[0020] In one embodiment, the average particle size D1 of the first solid electrolyte is 0.5 μm to 10 μm.

[0021] In one embodiment, the average particle size D2 of the second solid electrolyte is 1 μm to 8 μm.

[0022] In one embodiment, the average particle size D3 of the third solid electrolyte is 0.5 μm to 5 μm.

[0023] In one embodiment, the mass content W1 of the first solid electrolyte is 1 wt % to 40 wt %.

[0024] In one embodiment, the mass content W2 of the second solid electrolyte is 1 wt % to 40 wt %.

[0025] In one embodiment, the mass content W3 of the third solid electrolyte is 1 wt% to 40 wt%.

[0026] In one embodiment, the mass content W1 of the first solid electrolyte is 7 wt % to 30 wt %.

[0027] In one embodiment, the mass content W2 of the second solid electrolyte is 5 wt % to 30 wt %.

[0028] In one embodiment, the mass content W3 of the third solid electrolyte is 5 wt % to 20 wt %.

[0029] In an embodiment, the areal density of the active material layer is 100 g / m 2 ~ 300 g / m 2 .

[0030] In an embodiment, the areal density of the first sub-active material layer is 30 g / m 2 ~ 150 g / m 2 .

[0031] In an embodiment, the areal density of the second sub-active material layer is 30 g / m 2 ~ 150 g / m 2 .

[0032] In an embodiment, the areal density of the third sub-active material layer is 30 g / m 2 ~ 150 g / m 2 .

[0033] In an embodiment, the compaction density of the first sub-active material layer is 2.64 g / cm 3 ~ 4.49 g / cm 3 .

[0034] In an embodiment, the compaction density of the second sub-active material layer is 2.64 g / cm 3 ~ 4.55 g / cm 3 .

[0035] In an embodiment, the compaction density of the third sub-active material layer is 2.85 g / cm 3 ~ 4.55 g / cm 3 .

[0036] In an embodiment, the thickness of the active material layer is 45 μm ~ 240 μm.

[0037] In an embodiment, the thickness of the first sub-active material layer is 15 μm ~ 80 μm.

[0038] In an embodiment, the thickness of the second sub-active material layer is 15 μm ~ 80 μm.

[0039] In an embodiment, the thickness of the third sub-active material layer is 15 μm ~ 80 μm.

[0040] In a second aspect, embodiments of the present application provide a method for manufacturing a pole piece, comprising:

[0041] providing a current collector;

[0042] A first slurry is provided, the first slurry comprising a first solid-state electrolyte, and a first sub-active material layer is obtained after a first film-forming treatment and a first rolling treatment of the first slurry on the current collector;

[0043] A second slurry is provided, the second slurry comprising a second solid-state electrolyte, the second solid-state electrolyte having an average particle size D2 greater than an average particle size D1 of the first solid-state electrolyte, and a second sub-active material layer is obtained after a second film-forming treatment and a second rolling treatment of the second slurry on the first sub-active material layer, the first sub-active material layer having a mass content W1 of the first solid-state electrolyte greater than a mass content W2 of the second solid-state electrolyte in the second sub-active material layer.

[0044] In an embodiment, the method for preparing the electrode tab further comprises:

[0045] A third slurry is provided, the third slurry comprising a third solid-state electrolyte, the second solid-state electrolyte having an average particle size D2 greater than an average particle size D3 of the third solid-state electrolyte, and a third sub-active material layer is obtained after a third film-forming treatment and a third rolling treatment of the third slurry on the second sub-active material layer, the first sub-active material layer having a mass content W1 of the first solid-state electrolyte greater than a mass content W3 of the third solid-state electrolyte in the third sub-active material layer.

[0046] In a third aspect, an embodiment of the present application provides a solid-state battery, comprising a positive electrode, a negative electrode, and a solid-state electrolyte membrane between the positive electrode and the negative electrode, at least one of the positive electrode and the negative electrode comprising the electrode tab as described above or the electrode tab prepared by the method for preparing the electrode tab as described above.

[0047] In an embodiment, the negative electrode comprises at least one of a lithium metal negative electrode, a silicon negative electrode, a silver-carbon negative electrode, a lithium titanate negative electrode, and a lithium alloy negative electrode.

[0048] The embodiments of the present application have the following beneficial effects:

[0049] The pole piece provided by the embodiment of the present application is designed to include at least two high-density sub-active material layers, i.e., a first sub-active material layer and a second sub-active material layer, so that the difficulty of densification of the active material layer can be reduced, and the active material layer has a high compaction density at different thicknesses (i.e., different sub-active material layers), thereby improving the contact probability, contact area and contact stability between solid-state electrolytes and between the solid-state electrolyte and the active material in the active material layer, and further improving the solid-solid contact effect inside the pole piece. In addition, the different sub-active material layers in the active material layer are designed differently, the content of the solid-state electrolyte in the first sub-active material layer close to the current collector is higher but the particle size is smaller, so that more continuous lithium ion channels are constructed, the active material in the first sub-active material layer is effectively utilized, and the probability of inactivation of the active material is reduced; and the content of the solid-state electrolyte in the second sub-active material layer away from the current collector is lower but the particle size is larger, a low-tortuosity ion transmission channel is constructed, lithium ion transmission is promoted, and the rate performance of the solid-state battery is improved. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0051] Figure 1 is a cross-sectional structure schematic diagram of the pole piece provided by the embodiment of the present application;

[0052] Figure 2 is a structure schematic diagram of the pole piece provided by the embodiment of the present application;

[0053] Figure 3 is a cross-sectional structure schematic diagram of the solid-state battery provided by the embodiment of the present application.

[0054] Explanation of reference signs:

[0055] 10, pole piece;

[0056] 1, current collector;

[0057] 2, active material layer; 21, first sub-active material layer; 22, second sub-active material layer; 23, third sub-active material layer;

[0058] 100, solid-state battery;

[0059] 101, positive electrode;

[0060] 102, negative electrode;

[0061] 103. A solid-state electrolyte film. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative work are within the scope of protection of the present application.

[0063] In addition, it should be understood that the specific implementations described herein are merely for illustration and explanation of the present application, and are not intended to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the unit, and specifically refer to the direction of the drawing surface in the accompanying drawings; and "inner" and "outer" refer to the contour of the unit.

[0064] The terms "first", "second", "third", etc. are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0065] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection or can communicate with each other; can be directly connected, or indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0066] The terms "including", "containing" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0067] In the description of the embodiments of the present application, the word "example" or "for example" is used to mean "an example of" or "for example". Any embodiment or design solution described as "example" or "for example" in the embodiments of the present application is not to be interpreted as being more preferred than another embodiment or design solution. The use of the word "example" or "for example" is intended to present clearly a relative concept in a clear manner.

[0068] In order to facilitate the understanding of the scheme of the present application, the spline curves and arrows used in the reference signs in the drawings are described as follows: the components indicated by the spline curves without arrows are solid components, i.e. components with solid structures; the components indicated by the spline curves with arrows are virtual components, i.e. components without solid structures.

[0069] In a first aspect, referring to Figures 1 to 3 The embodiments of the present application provide an electrode sheet 10, which comprises a current collector 1 and an active material layer 2 arranged on the current collector 1, the active material layer 2 comprising a plurality of layers of sub-active material layers arranged in sequence, the sub-active material layer containing active material and the compaction density of the sub-active material layer being greater than or equal to 2.50 g / cm 3 The plurality of layers of sub-active material layers comprises a first sub-active material layer 21 and a second sub-active material layer 22 arranged in sequence in a direction away from the current collector 1, the first sub-active material layer 21 further containing a first solid-state electrolyte, the second sub-active material layer 22 further containing a second solid-state electrolyte, the average particle size D2 of the second solid-state electrolyte being greater than the average particle size D1 of the first solid-state electrolyte, and the mass content W1 of the first solid-state electrolyte in the first sub-active material layer 21 being greater than the mass content W2 of the second solid-state electrolyte in the second sub-active material layer 22.

[0070] The electrode sheet 10 can be a positive electrode sheet or a negative electrode sheet. It can be understood that when the electrode sheet 10 is a positive electrode sheet, the current collector 1 is a positive current collector and the active material layer 2 is a positive active material layer; when the electrode sheet 10 is a negative electrode sheet, the current collector 1 is a negative current collector and the active material layer 2 is a negative active material layer. Referring to Figure 3 The electrode sheet 10 can be used in a solid-state battery 100, wherein a solid-state electrolyte film 103 of the solid-state battery 100 is arranged in sequence with the electrode sheet 10, and the active material layer 2 is located between the solid-state electrolyte film 103 and the current collector 1.

[0071] The active material layer 2 is a multi-layer structure comprising a plurality of layers of sub-active material layers arranged in sequence, each sub-active material layer containing active material. It should be noted that the number of sub-active material layers in the active material layer 2 can be two, three, four or more. Alternatively, the number of sub-active material layers in the active material layer 2 is 2-4, for example 2, 3 or 4.

[0072] The sub-active material layer is a densified structure layer, wherein the compaction density of each sub-active material layer is greater than or equal to 2.50 g / cm 3 It can be understood that the sub-active material layer constituting the active material layer 2 is a densified structure layer, and then the active material layer 2 naturally has a high density. In the preparation of the active material layer 2, the multiple densified sub-active material layers are stacked together.

[0073] Generally, the thicker the material layer, the more difficult it is to densify the material layer, and the uniformity of the densification of the material layer is difficult to control. Taking the active material layer on the pole piece as an example, if the single-layer structure of the active material layer is directly rolled to improve the compaction density to achieve densification, the active material layer is easy to break due to brittleness, and the densification degree of the single-layer structure of the active material layer in the thickness direction is difficult to be consistent. Generally, the densification degree of the part of the active material layer close to the current collector and the part far away from the current collector is high, and the densification degree of the middle region of the active material layer is low.

[0074] The active material layer 2 provided by the embodiment of the present application is a multi-layer structure, compared with the single-layer structure of the active material layer with the same thickness, the active material layer 2 is composed of thinner multi-layer sub-active material layers. The sub-active material layer has better toughness due to the smaller thickness, and the sub-active material layer is not easy to break in the rolling process. The area with low densification degree after rolling is small or almost non-existent, so that the compaction density of the sub-active material layer is improved. At the same time, the sub-active material layer constitutes the active material layer 2, and the compaction density of the sub-active material layer is improved to ensure that the area of the active material layer 2 is improved. In summary, compared with the single-layer structure of the active material layer, the multi-layer structure of the active material layer 2 provided by the embodiment of the present application not only makes it easier to control the density of the active material layer at different thickness positions, but also improves the compaction density of the active material layer 2 as a whole.

[0075] Specifically, the multi-layer sub-active material layer includes at least a first sub-active material layer 21 and a second sub-active material layer 22. That is, the active material layer 2 includes at least two sub-active material layers, which are the first sub-active material layer 21 and the second sub-active material layer 22, that is, the active material layer 2 includes at least the first sub-active material layer 21 and the second sub-active material layer 22. When the active material layer 2 is arranged on the current collector 1, the first sub-active material layer 21 and the second sub-active material layer 22 are arranged in sequence in the direction away from the current collector 1. That is, the first sub-active material layer 21 is closer to the current collector 1 than the second sub-active material layer 22. As an example, the first sub-active material layer 21 is arranged on the surface of the current collector 1, and the second sub-active material layer 22 is arranged on the surface of the first sub-active material layer 21 and away from the current collector 1.

[0076] As the sub-active material layer, the first sub-active material layer 21 contains active material, and the second sub-active material layer 22 also contains active material; the compaction density of the first sub-active material layer 21 is greater than or equal to 2.50 g / cm 3 The compaction density of the second sub-active material layer 22 is also greater than or equal to 2.50 g / cm 3 However, the first sub-active material layer 21 and the second sub-active material layer 22 are not exactly the same, and the embodiments of the present application are designed differently. Specifically, the first sub-active material layer 21 also contains a first solid-state electrolyte, and the second sub-active material layer 22 also contains a second solid-state electrolyte, wherein the average particle size D2 of the second solid-state electrolyte is greater than the average particle size D1 of the first solid-state electrolyte, and the mass content W1 of the first solid-state electrolyte in the first sub-active material layer 21 is greater than the mass content W2 of the second solid-state electrolyte in the second sub-active material layer 22. As can be seen, the first sub-active material layer 21 and the second sub-active material layer 22 not only differ in the average particle size of the solid-state electrolyte, but also differ in the content of the solid-state electrolyte. Among them, the average particle size of the solid-state electrolyte (i.e. the first solid-state electrolyte) in the first sub-active material layer 21 is smaller, but the content of the solid-state electrolyte is higher, and the average particle size of the solid-state electrolyte (i.e. the second solid-state electrolyte) in the second sub-active material layer 22 is larger, but the content of the solid-state electrolyte is lower. It should be noted that the first solid-state electrolyte and the second solid-state electrolyte can be the same substance or different substances.

[0077] Please refer to Figure 2 Since the first sub-active material layer 21 is closer to the current collector 1 than the second sub-active material layer 22, the ion transmission distance is greater, and by increasing the content of the first solid-state electrolyte in the first sub-active material layer 21 and reducing the average particle size of the first solid-state electrolyte, the uniformity of the dispersion of the first solid-state electrolyte in the active material is promoted, combined with the densification of the first sub-active material layer 21, the solid-solid contact effect between the first solid-state electrolyte and the active material in the first sub-active material layer 21 can be improved, thereby facilitating the construction of more continuous lithium ion channels, so that the active material in the first sub-active material layer 21 is effectively utilized, the probability of deactivation of the active material is reduced, and the capacity of the pole piece 10 is improved.

[0078] Please refer to Figure 2The second sub-active material layer 22 is located on the side of the first sub-active material layer 21 away from the current collector 1, so that when the pole piece 10 is used in the solid-state battery 100, the second sub-active material layer 22 is closer to the solid-state electrolyte film 103 in the solid-state battery 100 than the first sub-active material layer 21, so that the lithium ions reaching the first sub-active material layer 21 need to pass through the second sub-active material layer 22 first, that is, the second sub-active material layer 22 also serves as an ion transmission structure. By increasing the average particle size of the second solid-state electrolyte in the second sub-active material layer 22, combined with the improvement of the density of the second sub-active material layer 22, it is beneficial to construct an ion transmission channel with low tortuosity, promote the rapid transmission of lithium ions, and improve the rate performance of the solid-state battery 100. At the same time, since the second sub-active material layer 22 is farther away from the current collector 1 than the first sub-active material layer 21, in the solid-state battery 100, the second sub-active material layer 22 is closer to the solid-state electrolyte film 103, the ion transmission distance is small, and the utilization rate of the active material in the second sub-active material layer 22 is higher. The content of the second solid-state electrolyte in the second sub-active material layer 22 can be appropriately reduced, and the content of the active material in the second sub-active material layer 22 is increased instead, thereby improving the capacity of the pole piece 10 and the energy density of the solid-state battery 100.

[0079] In summary, the pole piece 10 provided by the embodiments of the present application designs the active material layer 2 to include at least two high-density sub-active material layers: the first sub-active material layer 21 and the second sub-active material layer 22, which not only reduces the difficulty of densification of the active material layer 2, but also enables the active material layer 2 to have a high compaction density at different thicknesses (i.e., on different sub-active material layers), thereby improving the contact probability, contact area, and contact stability between the solid-state electrolytes and between the solid-state electrolytes and the active material in the active material layer 2, and further improving the solid-solid contact effect inside the pole piece 10. In addition, the embodiments of the present application also differentially design different sub-active material layers in the active material layer 2, by making the content of the solid-state electrolyte in the first sub-active material layer 21 close to the current collector 1 higher but the particle size smaller, thereby constructing more continuous lithium ion channels, making the active material in the first sub-active material layer 21 be effectively utilized, and reducing the probability of deactivation of the active material; and the content of the solid-state electrolyte in the second sub-active material layer 22 away from the current collector 1 is lower but the particle size is larger, constructing an ion transmission channel with low tortuosity, promoting the rapid transmission of lithium ions, and improving the rate performance of the solid-state battery 100.

[0080] In some embodiments, please refer to Figure 1The multi-layer sub-active material layer further comprises a third sub-active material layer 23, which is arranged on the side of the second sub-active material layer 22 away from the first sub-active material layer 21. The third sub-active material layer 23 also contains a third solid-state electrolyte. The average particle size D2 of the second solid-state electrolyte is greater than the average particle size D3 of the third solid-state electrolyte. The mass content W1 of the first solid-state electrolyte in the first sub-active material layer 21 is greater than the mass content W3 of the third solid-state electrolyte in the third sub-active material layer 23.

[0081] That is, the active material layer 2 further comprises a third sub-active material layer 23, that is, the number of sub-active material layers is at least three. The third sub-active material layer 23 is one of the sub-active material layers. Like the first sub-active material layer 21 and the second sub-active material layer 22, the third sub-active material layer 23 also contains an active material. The compaction density of the third sub-active material layer 23 is also greater than or equal to 2.50 g / cm 3 That is, the third sub-active material layer 23 also has a high degree of densification. The first sub-active material layer 21, the second sub-active material layer 22, and the third sub-active material layer 23 are arranged in sequence in the direction away from the current collector 1. In the case where the number of sub-active material layers is only three, the third sub-active material layer 23 also serves as a surface layer of the active material layer 2. The third sub-active material layer 23 can be used to directly contact the solid-state electrolyte film 103.

[0082] The third sub-active material layer 23 is also designed differently in the embodiments of the present application. The average particle size of the solid-state electrolyte (i.e., the third solid-state electrolyte) in the third sub-active material layer 23 is smaller than the average particle size of the solid-state electrolyte (i.e., the second solid-state electrolyte) in the second sub-active material layer 22. The content of the solid-state electrolyte in the third sub-active material layer 23 is smaller than the content of the solid-state electrolyte (i.e., the first solid-state electrolyte) in the first sub-active material layer 21. By using a small-particle-size solid-state electrolyte in the third sub-active material layer 23, the volume fraction of the solid-state electrolyte is ensured while the mass proportion of the solid-state electrolyte is reduced. The specific surface area of the third sub-active material layer 23 can be increased. When the third sub-active material layer 23 serves as a surface layer of the active material layer 2 and contacts the solid-state electrolyte film 103, the third sub-active material layer 23 can provide more contact sites. This is conducive to improving the interface contact effect between the electrode sheet 10 and the solid-state electrolyte film 103 and reducing the interface impedance.

[0083] It is to be noted that the relationship between the average particle size of the third solid-state electrolyte in the third sub-active material layer 23 and the average particle size of the first solid-state electrolyte in the first sub-active material layer 21 can be equal, or the former can be greater than the latter, or the former can be less than the latter. The relationship between the mass content of the third solid-state electrolyte in the third sub-active material layer 23 and the mass content of the second solid-state electrolyte in the second sub-active material layer 22 can be equal, or the former can be greater than the latter, or the former can be less than the latter.

[0084] In some embodiments, the active material includes a cathode active material, and the cathode active material includes at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, and lithium-rich manganese-based material. It can be understood that when the active material includes the cathode active material, the electrode tab 10 is a cathode electrode tab. The electrode tab 10 with the above structure can be suitable for various cathode material systems and has good performance, and has high universality. As an example, the NCM includes at least one of NCM83 (LiNi0.83Co0.07Mn0.10O2) and NCM523 (LiNi0.53Co0.17Mn0.30O2). 0.83 Co 0.11 Mn 0.06 O2) and NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2) and NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2) and NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2) and NCM523 (LiNi

[0085] In some embodiments, the cathode active material is coated with a coating layer. Due to the increase in the compaction density of the sub-active material layer, the active material is more likely to contact the electrolyte, so the coating layer can separate the active material and the electrolyte, reduce the probability of direct contact between the two, effectively inhibit the occurrence of element diffusion and interfacial electrochemical reaction, thereby improving the electrochemical performance of the solid-state battery 20. Optionally, the coating layer includes at least one of Li3PO4, LiNbO3, Li4Ti5O2, Li2ZrO3, and Li3BO3.

[0086] In some embodiments, the first active material layer 21, the second active material layer 22, and the third active material layer 23 each further include a conductive agent and a binder. Optionally, the binder includes at least one of polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polyvinylidene fluoride (PVDF), polyisobutylene (PIB), hydrogenated nitrile butadiene rubber (HNBR), styrene-butadiene-styrene block copolymer (SBS), and hydrogenated styrene-butadiene block copolymer (SEBS). Optionally, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, carbon nanofibers, graphite, and graphene. As an example, the conductive agent includes vapor-grown carbon fibers (VGCF).

[0087] In some embodiments, the mass content of the binder in the first sub-active material layer 21, the second sub-active material layer 22, and the third sub-active material layer 23 is 0.5wt% to 10wt%. As an example, the mass content of the binder in the first sub-active material layer 21, the mass content of the binder in the second sub-active material layer 22, and the mass content of the binder in the third sub-active material layer 23 can each independently be selected from one of the following contents: 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt%, or 10wt%.

[0088] In some embodiments, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte each independently comprises at least one of a sulfide solid-state electrolyte (LiPhosphorus Sulfur Composite, abbreviated as LPSC), a halide solid-state electrolyte, and an oxide solid-state electrolyte. That is, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte can be the same substance or different substances. As an example, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte are all sulfide solid-state electrolytes; or the first solid-state electrolyte is a sulfide solid-state electrolyte, the second solid-state electrolyte is a halide solid-state electrolyte, and the third solid-state electrolyte is an oxide solid-state electrolyte.

[0089] In some embodiments, the sulfide solid-state electrolyte comprises Li 7-a PS 6-a X a , Li3PS4, Li4SnS4, 75Li2S-25P2S5, Li7SiPS8, and Li 10 GeP2S 12 , wherein X is a halogen element, and a is 0.8 to 2.0. Optionally, the halogen element comprises one or more of F, Cl, Br, and I. The value of a is 0.8 to 2.0, for example, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0. Optionally, the value of a is 1.0 to 1.5. As an example, when a is 1 and X is Cl, the sulfide solid-state electrolyte is specifically LPSCl (Li6PS5Cl). 7-a PS 6- a X a

[0090] ​In some embodiments, the halide solid-state electrolyte includes Li b MY4, Li b MY6, Li b MY8, and at least one of oxyhalide electrolyte, wherein M is an alkali metal element, Y is a halogen element. Y refers to a halogen element, including one or more of F, Cl, Br, I. M refers to an alkali metal element, including one or more of Zr, Y, In, Sc, Ta, La, Nb, Al, Sn, Sb. The value of b depends on the valence state of the M metal element.

[0091] In some embodiments, the oxide solid-state electrolyte includes at least one of garnet-type oxide solid-state electrolyte, NASICON-type oxide solid-state electrolyte, and perovskite-type oxide solid-state electrolyte. Garnet-type oxide solid-state electrolyte is an important class of inorganic solid-state electrolyte, with high ionic conductivity, good chemical stability, and excellent interface compatibility with lithium metal. As an example, the garnet-type oxide solid-state electrolyte includes Li7La3Zr2O12(LLZO), Li5La3Ta2O12, and Li6.4La3Zr1.4Al0.6O12. 12 6.4 La 3.6 Ta2O 12 12 wherein A and B represent tetravalent and pentavalent framework ions, respectively. NASICON-type solid-state electrolyte has good ionic conductivity, thermal stability, and mechanical properties, and has high stability to air, and thus has been widely concerned and applied in the field of solid-state batteries. As an example, the NASICON-type solid-state electrolyte includes Li 1+x Al x Ti 2-x (PO4)3(LATP). Perovskite-type oxide solid-state electrolyte is a class of materials with ABO3 structure, with high ionic conductivity and good chemical stability. As an example, the perovskite-type oxide solid-state electrolyte includes Li3La2TiO7. 2 / 3- x TiO3(LLTO).

[0092] ​​In some embodiments, the average particle size D1 of the first solid-state electrolyte is 0.2 pm to 20 pm. Controlling the average particle size of the first solid-state electrolyte helps to achieve better dispersion effect and specific surface area of the first solid-state electrolyte in the first sub-active material layer 21, thereby improving the effect of solid-solid contact between the first solid-state electrolyte and the active material. For example, the average particle size D1 of the first solid-state electrolyte is 0.2 pm, 1.0 pm, 2.0 pm, 3.0 pm, 4.0 pm, 5.0 pm, 6.0 pm, 7.0 pm, 8.0 pm, 9.0 pm, 10.0 pm, 11.0 pm, 12.0 pm, 13.0 pm, 14.0 pm, 15.0 pm, 16.0 pm, 17.0 pm, 18.0 pm, 19.0 pm, or 20 pm. Alternatively, the average particle size D1 of the first solid-state electrolyte is 0.5 pm to 10 pm. Within the range, the effect of solid-solid contact between the first solid-state electrolyte and the active material can be further improved.

[0093] In some embodiments, the average particle size D2 of the second solid-state electrolyte is 0.5 pm to 20 pm. Controlling the average particle size of the second solid-state electrolyte helps to achieve better solid-solid contact effect between the second solid-state electrolyte and the active material in the second sub-active material layer 22, while at the same time shortening the path of lithium ion transmission as much as possible. For example, the average particle size D2 of the second solid-state electrolyte is 0.5 pm, 1.0 pm, 2.0 pm, 3.0 pm, 4.0 pm, 5.0 pm, 6.0 pm, 7.0 pm, 8.0 pm, 9.0 pm, 10.0 pm, 11.0 pm, 12.0 pm, 13.0 pm, 14.0 pm, 15.0 pm, 16.0 pm, 17.0 pm, 18.0 pm, 19.0 pm, or 20 pm. Alternatively, the average particle size D2 of the second solid-state electrolyte is 1 pm to 8 pm. Within the range, the effect of solid-solid contact between the second solid-state electrolyte and the active material can be further improved, and the path of lithium ion transmission can be further shortened.

[0094] In some embodiments, the average particle size D3 of the third solid-state electrolyte is 0.5 pm to 10 pm. Controlling the average particle size of the third solid-state electrolyte helps to achieve better solid-solid contact effect between the third solid-state electrolyte and the active material in the third sub-active material layer 23, while at the same time increasing the contact site as much as possible when the third sub-active material layer 23 as the surface layer of the active material layer 2 contacts the solid-state electrolyte film 103. Alternatively, the average particle size D3 of the third solid-state electrolyte is 0.5 pm to 5 pm. Within the range, the effect of solid-solid contact between the third solid-state electrolyte and the active material can be further improved, and the contact site of the third sub-active material layer 23 can be further increased.

[0095] In some embodiments, the mass content W1 of the first solid-state electrolyte is 1wt% to 40wt%. Generally, in the first sub-active material layer 21, the mass content W1 of the first solid-state electrolyte is too low to affect the solid-solid contact effect inside the electrode sheet 10, and too high to affect the energy density of the solid-state battery 20. As an example, the mass content W1 of the first solid-state electrolyte is 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%. Alternatively, the mass content W1 of the first solid-state electrolyte is 7wt% to 30wt%. Within this range, the electrode sheet 10 has a better solid-solid contact effect inside, while the energy density of the solid-state battery 20 is also considered.

[0096] In some embodiments, the mass content W2 of the second solid-state electrolyte is 1wt% to 40wt%. Generally, in the second sub-active material layer 22, the mass content W2 of the second solid-state electrolyte is too low to affect the solid-solid contact effect inside the electrode sheet 10, and too high to affect the energy density of the solid-state battery 20. As an example, the mass content W2 of the second solid-state electrolyte is 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%. Alternatively, the mass content W2 of the second solid-state electrolyte is 5wt% to 30wt%. Within this range, the electrode sheet 10 has a better solid-solid contact effect inside, while the energy density of the solid-state battery 20 is also considered.

[0097] In some embodiments, the mass content W3 of the third solid-state electrolyte is 1wt% to 40wt%. Generally, in the third sub-active material layer 23, the mass content W3 of the third solid-state electrolyte is too low to affect the solid-solid contact effect inside the electrode sheet 10, and too high to affect the energy density of the solid-state battery 20. As an example, the mass content W3 of the third solid-state electrolyte is 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%. Alternatively, the mass content W3 of the third solid-state electrolyte is 5wt% to 20wt%. Within this range, the electrode sheet 10 has a better solid-solid contact effect inside, while the energy density of the solid-state battery 20 is also considered.

[0098] In some embodiments, the areal density of the active material layer 2 is 100g / m 2 to 300g / m 2 . As an example, the areal density of the active material layer 2 is 100g / m 2 , 150g / m 2 , 200g / m 2 , 250g / m 2 or 300g / m 2 .

[0099] In some embodiments, the surface density of the first sub-active material layer 21 is 30 g / m 2 ~150g / m 2 As an example, the surface density of the first sub-active material layer 21 is 30 g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 , 100g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2 or 150g / m 2 .

[0100] In some embodiments, the surface density of the second sub-active material layer 22 is 30 g / m 2 ~150g / m 2 As an example, the surface density of the second sub-active material layer 22 is 30 g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 , 100g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2 or 150g / m 2 .

[0101] In some embodiments, the surface density of the third sub-active material layer 23 is 30 g / m 2 ~150g / m 2 As an example, the surface density of the third sub-active material layer 23 is 30 g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 , 100g / m 2 , 110g / m2 , 120 g / m 2 , 130 g / m 2 , 140 g / m 2 or 150 g / m 2 .

[0102] It should be noted that the areal densities of any two of the first sub-active material layer 21, the second sub-active material layer 22, and the third sub-active material layer 23 can be the same or different.

[0103] In some embodiments, the first sub-active material layer 21 has a compacted density of 2.64 g / cm 3 ~ 4.49 g / cm 3 . By increasing the compacted density of the first sub-active material layer 21, the solid-solid contact between the first solid-state electrolyte and the active material in the first sub-active material layer 21 can be effectively improved, thereby improving the electrochemical performance of the solid-state battery 100. For example, the first sub-active material layer 21 has a compacted density of 2.64 g / cm 3 , 2.70 g / cm 3 , 2.80 g / cm 3 , 2.90 g / cm 3 , 3.00 g / cm 3 , 3.10 g / cm 3 , 3.20 g / cm 3 , 3.30 g / cm 3 , 3.40 g / cm 3 , 3.50 g / cm 3 , 3.60 g / cm 3 , 3.70 g / cm 3 , 3.80 g / cm 3 , 3.90 g / cm 3 , 4.00 g / cm 3 , 4.10 g / cm 3 , 4.20 g / cm 3 , 4.30 g / cm 3 or 4.49 g / cm 3 .

[0104] In some embodiments, the second sub-active material layer 22 has a compacted density of 2.64 g / cm 3 ~ 4.55 g / cm 3 . By increasing the compacted density of the second sub-active material layer 22, the solid-solid contact between the second solid-state electrolyte and the active material in the second sub-active material layer 22 can be effectively improved, thereby improving the electrochemical performance of the solid-state battery 100. For example, the second sub-active material layer 22 has a compacted density of 2.64 g / cm 32.70 g / cm 3 2.80 g / cm 3 2.90 g / cm 3 3.00 g / cm 3 3.10 g / cm 3 3.20 g / cm 3 3.30 g / cm 3 3.40 g / cm 3 3.50 g / cm 3 3.60 g / cm 3 3.70 g / cm 3 3.80 g / cm 3 3.90 g / cm 3 4.00 g / cm 3 4.10 g / cm 3 4.20 g / cm 3 4.30 g / cm 3 4.40 g / cm 3 or 4.55 g / cm 3 .

[0105] In some embodiments, the third sub-active material layer 23 has a compacted density of 2.85 g / cm 3 ~ 4.55 g / cm 3 . By increasing the compacted density of the third sub-active material layer 23, the solid-solid contact effect between the third solid-state electrolyte and the active material in the third sub-active material layer 23 can be effectively improved, thereby improving the electrochemical performance of the solid-state battery 100. As an example, the third sub-active material layer 23 has a compacted density of 2.85 g / cm 3 2.90 g / cm 3 3.00 g / cm 3 3.10 g / cm 3 3.20 g / cm 3 3.30 g / cm 3 3.40 g / cm 3 3.50 g / cm 3 3.60 g / cm 3 3.70 g / cm 3 3.80 g / cm 3 3.90 g / cm 3 4.00 g / cm 3 4.10 g / cm 3 4.20 g / cm 3 4.30 g / cm 3 4.40 g / cm 3 or 4.55 g / cm3 .

[0106] It should be noted that the compaction densities of any two of the first sub-active material layer 21, the second sub-active material layer 22 and the third sub-active material layer 23 can be the same or different.

[0107] In some embodiments, the electrode tab 10 is a positive electrode tab, and the current collector 1 is a positive current collector. As an example, the positive current collector includes at least one of an aluminum foil, a carbon-coated aluminum foil, a composite foil, a stainless steel foil, and a carbon-coated stainless steel foil.

[0108] In some embodiments, the thickness of the active material layer 2 is 45 μm to 240 μm. As an example, the thickness of the active material layer 2 is 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, or 240 μm.

[0109] In some embodiments, the thickness of the first active material layer 21 is 15 μm to 80 μm. As an example, the thickness of the first active material layer 21 is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm.

[0110] In some embodiments, the thickness of the second active material layer 22 is 15 μm to 80 μm. As an example, the thickness of the second active material layer 22 is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm.

[0111] In some embodiments, the thickness of the third active material layer 23 is 15 μm to 80 μm. As an example, the thickness of the third active material layer 23 is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm.

[0112] By the above arrangement, the obtained electrode tab 10 is a thick electrode, which can effectively improve the energy density of the battery.

[0113] In a second aspect, an embodiment of the present application provides a method for preparing an electrode tab, comprising:

[0114] providing a current collector;

[0115] The first slurry is provided, the first slurry comprising a first solid electrolyte, and the first slurry is subjected to a first film forming treatment and a first rolling treatment on the current collector to obtain a first sub-active material layer;

[0116] The second slurry is provided, the second slurry comprising a second solid electrolyte, the average particle size D2 of the second solid electrolyte being greater than the average particle size D1 of the first solid electrolyte, and the second slurry is subjected to a second film forming treatment and a second rolling treatment on the first sub-active material layer to obtain a second sub-active material layer, the mass content W1 of the first solid electrolyte in the first sub-active material layer being greater than the mass content W2 of the second solid electrolyte in the second sub-active material layer.

[0117] The preparation method of the pole piece provided in the embodiments of the present application can effectively improve the compaction density of the obtained active material layer, realize high densification, and improve the uniformity of the active material layer in the thickness direction by adopting the independent film forming and independent rolling manner to respectively prepare the first sub-active material layer and the second active material layer.

[0118] In some embodiments, the preparation method of the pole piece further comprises:

[0119] The third slurry is provided, the third slurry comprising a third solid electrolyte, the average particle size D2 of the second solid electrolyte being greater than the average particle size D3 of the third solid electrolyte, and the third slurry is subjected to a third film forming treatment and a third rolling treatment on the second sub-active material layer to obtain a third sub-active material layer, the mass content W1 of the first solid electrolyte in the first sub-active material layer being greater than the mass content W3 of the third solid electrolyte in the third sub-active material layer.

[0120] Similarly, the third sub-active material layer is prepared by adopting the independent film forming and independent rolling manner, and the compaction density of the active material layer is effectively controlled.

[0121] In some embodiments, at least one of the first film forming treatment, the second film forming treatment and the third film forming treatment is a wet film forming treatment, and correspondingly, at least one of the first slurry, the second slurry and the third slurry comprises a solvent. Optionally, the solvent comprises at least one of anisole, phenetole, p-xylene, n-heptane, 1,2-dibromomethane and butyl butyrate.

[0122] As an example, the pole piece is a positive pole piece, and the preparation method of the positive pole piece comprises:

[0123] Preparation of the slurry: the positive active material, the first solid-state electrolyte, the conductive agent, the binder and the solvent are mixed uniformly in a certain proportion, and a first slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using a wet homogenizing method; the positive active material, the second solid-state electrolyte, the conductive agent, the binder and the solvent are mixed uniformly in a certain proportion, and a second slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using a wet homogenizing method; the positive active material, the third solid-state electrolyte, the conductive agent, the binder and the solvent are mixed uniformly in a certain proportion, and a third slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using a wet homogenizing method.

[0124] Multi-layer coating multi-stage continuous hot rolling: a coating machine is used to coat the first slurry on the positive current collector, and after drying, rolling densification is performed to obtain a first sub-active material layer; a coating machine is used to coat the second slurry on the first sub-active material layer, and after drying, rolling densification is performed to obtain a second sub-active material layer; a coating machine is used to coat the third slurry on the second sub-active material layer, and after drying, rolling densification is performed to obtain a third sub-active material layer.

[0125] The multi-layer coating multi-stage continuous hot rolling process is to set multiple coating heads, multiple ovens and multiple rolling devices through a coating machine, to coat an ultra-thin coating (areal density 40-80 mAh / cm 2 ) in a single coating, to realize the densification of the ultra-thin coating after drying and rolling, to obtain a sub-active material layer, and then to repeat the process (2-4 times) to finally realize the manufacturing of a high-density electrode sheet; the densification degree of each sub-active material layer and the active material layer is 75%-95%.

[0126] In a third aspect, referring to Figure 3 , the embodiment of the present application provides a solid-state battery 100, which comprises a positive electrode 101, a negative electrode 102 and a solid-state electrolyte film 103 between the positive electrode 101 and the negative electrode 102, and at least one of the positive electrode 101 and the negative electrode 102 comprises an electrode sheet or an electrode sheet prepared by the preparation method of the electrode sheet.

[0127] In some embodiments, the negative electrode 101 comprises at least one of a lithium metal negative electrode, a silicon negative electrode, a silver-carbon negative electrode, a lithium titanate negative electrode and a lithium alloy negative electrode.

[0128] The following is described in combination with specific embodiments.

[0129] Preparation Example 1

[0130] The preparation example provides an electrode sheet, referring to Table 1, and the preparation process of the electrode sheet comprises:

[0131] S11, the positive active material NCM83, the first solid-state electrolyte LPSCl (the average particle size is 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83:LPSCl:VGCF:SBR = 85:12:1.5:1.5, and a first electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenate method;

[0132] S12, the positive active material NCM83, the second solid-state electrolyte LPSCl (the average particle size is 3.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83:LPSCl:VGCF:SBR = 88:9:1.5:1.5, and a second electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenate method;

[0133] S13, the positive active material NCM83, the third solid-state electrolyte LPSCl (the average particle size is 0.5 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83:LPSCl:VGCF:SBR = 88:9:1.5:1.5, and a third electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenate method;

[0134] S14, a multi-layer coating multi-stage continuous hot roller pressing process is adopted, the first electrode slurry is coated on the positive current collector by using a coating machine, and then dried and compacted by roller pressing to obtain a first sub-active material layer, the densification degree of the first sub-active material layer is 90%, the compacted density is 3.90 g / cm 3 , and the area density is 80 g / m 2 ; then the second electrode slurry is coated on the first sub-active material layer by using a coating machine, and then dried and compacted by roller pressing to obtain a second sub-active material layer, the densification degree of the second sub-active material layer is 89%, the compacted density is 3.94 g / cm 3 , and the area density is 80 g / m 2 ; finally, the third electrode slurry is coated on the second sub-active material layer by using a coating machine, and then dried and compacted by roller pressing to obtain a third sub-active material layer, the densification degree of the third sub-active material layer is 90%, the compacted density is 3.98 g / cm 3 , and the area density is 80 g / m 2 , thereby obtaining a pole piece, which is specifically a positive pole piece. In the positive pole piece, the thicknesses of the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer are equal.

[0135] Here, the actual density of the active material layer is 真 = ρi · x i ; the densification degree D (%) = 100 - (1 - p 压实 / ptrue) x 100; p i is the true density of a component in the active material layer; x i is the mass fraction of a component in the active material layer; p 压实 is the compacted density of the active material layer. The active material layer comprises a first sub-active material layer, a second sub-active material layer and a third sub-active material layer arranged in sequence, the densification degree of the active material layer is the average of the densification degrees of the three sub-active material layers, the compacted density of the active material layer is the average of the compacted densities of the three sub-active material layers, and the area density of the active material layer is the sum of the area densities of the three sub-active material layers.

[0136] Table 1

[0137]

[0138] Preparation Example 2

[0139] The present preparation example provides a pole piece, please see Table 2, the preparation process of the pole piece includes:

[0140] S11, the positive active material NCM83, the first solid-state electrolyte LPSCl (the average particle size is 1.0 μm), the conductive agent VGCF, the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 85: 12: 1.5: 1.5, and the first electrode slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using the wet homogenization method.

[0141] S12, the positive active material NCM83, the second solid-state electrolyte LPSCl (the average particle size is 3.0 μm), the conductive agent VGCF, the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 88: 9: 1.5: 1.5, and the second electrode slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using the wet homogenization method.

[0142] S13, the positive active material NCM83, the third solid-state electrolyte LPSCl (the average particle size is 0.5 μm), the conductive agent VGCF, the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 88: 9: 1.5: 1.5, and the third electrode slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by using the wet homogenization method.

[0143] S14, multilayer coating multi-stage continuous hot rolling process: a coating machine is used to coat the first electrode slurry on the positive current collector, and after drying, the first electrode slurry is rolled and densified to obtain a first sub-active material layer, the densification degree of the first sub-active material layer is 80%, the compaction density is 3.46 g / cm 3 , and the area density is 80 g / m 2 ; then a coating machine is used to coat the second electrode slurry on the first sub-active material layer, and after drying, the second electrode slurry is rolled and densified to obtain a second sub-active material layer, the densification degree of the second sub-active material layer is 80%, the compaction density is 3.54 g / cm 3 , and the area density is 80 g / m 2 ; finally, a coating machine is used to coat the third electrode slurry on the second sub-active material layer, and after drying, the third electrode slurry is rolled and densified to obtain a third sub-active material layer, the densification degree of the third sub-active material layer is 80%, the compaction density is 3.59 g / cm 3 , and the area density is 80 g / m 2 , thereby obtaining a pole piece, which is specifically a positive pole piece. In the positive pole piece, the thicknesses of the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer are equal.

[0144] Table 2

[0145]

[0146]

[0147] Preparation Example 3

[0148] The preparation example provides a pole piece, please refer to Table 3, the preparation process of the pole piece includes:

[0149] S11, the positive active material NCM83, the first solid-state electrolyte LPSCl (the average particle size is 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 85: 12: 1.5: 1.5, and a first electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenate method;

[0150] S12, the positive active material NCM83, the second solid-state electrolyte LPSCl (the average particle size is 3.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 88: 9: 1.5: 1.5, and a second electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenate method;

[0151] S14, multilayer coating multi-stage continuous hot rolling process: a coating machine is used to coat the first electrode slurry on the positive current collector, and after drying, the first sub-active material layer is obtained by rolling densification, and the densification degree of the first sub-active material layer is 90%, and the compacted density is 3.90 g / cm 3 , and the areal density is 120 g / m 2 ; then a coating machine is used to coat the second electrode slurry on the first sub-active material layer, and after drying, the second sub-active material layer is obtained by rolling densification, and the densification degree of the second sub-active material layer is 89%, and the compacted density is 3.94 g / cm 3 , and the areal density is 120 g / m 2 , and further obtain the pole piece, which is specifically a positive pole piece.

[0152] Table 3

[0153]

[0154]

[0155] Comparative Example 1A

[0156] This comparative example provides a pole piece, please refer to Table 4, the preparation process of the pole piece includes:

[0157] The positive active material NCM83, the solid-state electrolyte LPSCl (average particle size is 1.5 μm), the conductive agent VGCF, and the binder SBR are mixed with the solvent p-xylene in a mass ratio of NCM83: LPSCl: VGCF: SBR = 87: 10: 1.5: 1.5 to obtain a uniform, stable, and well-flowing electrode slurry with appropriate viscosity.

[0158] A coating machine is used to coat the electrode slurry on the positive current collector, and after drying, the single-layer active material layer is obtained by rolling densification, and the densification degree of the active material layer is 82%, and the compacted density is 3.60 g / cm 3 , and the areal density is 240 g / m 2 , and further obtain the pole piece, which is specifically a positive pole piece.

[0159] Table 4

[0160]

[0161] Comparative Example 1B

[0162] This comparative example provides a pole piece, please refer to Table 5, the preparation process of the pole piece includes:

[0163] The positive electrode active material NCM83, the solid-state electrolyte LPSCl (average particle size 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with solvent p-xylene in a mass ratio of NCM83:LPSCl:VGCF:SBR = 85:12:1.5:1.5 to prepare a first electrode slurry that is uniform, stable, has good fluidity, and has a suitable viscosity.

[0164] The electrode slurry is coated on the positive electrode current collector using a coating machine, dried, and then roll-pressed to densify to obtain a single-layer active material layer, the densification degree of the active material layer being 83%, the compacted density being 3.59 g / cm 3 , and the area density being 240 g / m 2 . Further, a pole piece is obtained, which is specifically a positive electrode pole piece.

[0165] Table 5

[0166]

[0167] Comparative Example 1C

[0168] This comparative example provides a pole piece, please refer to Table 6, the preparation process of the pole piece includes:

[0169] S11, the positive electrode active material NCM83, the first solid-state electrolyte LPSCl (average particle size 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with solvent p-xylene in a mass ratio of NCM83:LPSCl:VGCF:SBR = 87:10:1.5:1.5 to prepare a first electrode slurry that is uniform, stable, has good fluidity, and has a suitable viscosity;

[0170] S12, the positive electrode active material NCM83, the second solid-state electrolyte LPSCl (average particle size 3.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with solvent p-xylene in a mass ratio of NCM83:LPSCl:VGCF:SBR = 87:10:1.5:1.5 to prepare a second electrode slurry that is uniform, stable, has good fluidity, and has a suitable viscosity;

[0171] S13, the positive electrode active material NCM83, the third solid-state electrolyte LPSCl (average particle size 0.5 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with solvent p-xylene in a mass ratio of NCM83:LPSCl:VGCF:SBR = 87:10:1.5:1.5 to prepare a third electrode slurry that is uniform, stable, has good fluidity, and has a suitable viscosity;

[0172] S14, multilayer coating multi-stage continuous hot rolling process: a coating machine is used to coat the first electrode slurry on the positive current collector, and after drying, the first electrode slurry is rolled and densified to obtain a first sub-active material layer, the densification degree of the first sub-active material layer is 89%, the compaction density is 3.94 g / cm 3 , the area density is 80 g / m 2 ; then a coating machine is used to coat the second electrode slurry on the first sub-active material layer, and after drying, the second electrode slurry is rolled and densified to obtain a second sub-active material layer, the densification degree of the second sub-active material layer is 88%, the compaction density is 3.87 g / cm 3 , the area density is 80 g / m 2 ; finally, a coating machine is used to coat the third electrode slurry on the second sub-active material layer, and after drying, the third electrode slurry is rolled and densified to obtain a third sub-active material layer, the densification degree of the third sub-active material layer is 89%, the compaction density is 3.90 g / cm 3 , the area density is 80 g / m 2 , thereby obtaining the electrode sheet, which is specifically a positive electrode sheet. In the positive electrode sheet, the thicknesses of the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer are equal.

[0173] Table 6

[0174]

[0175] Comparative Example 1D

[0176] This comparative example provides an electrode sheet, please refer to Table 7, the preparation process of the electrode sheet includes:

[0177] S11, the positive active material NCM83, the first solid-state electrolyte LPSCl (average particle size is 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 85: 12: 1.5: 1.5, and a first electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenization method;

[0178] S12, the positive active material NCM83, the second solid-state electrolyte LPSCl (average particle size is 1.0 μm), the conductive agent VGCF, and the binder SBR are uniformly mixed with the solvent p-xylene according to the mass ratio of NCM83: LPSCl: VGCF: SBR = 88: 9: 1.5: 1.5, and a second electrode slurry with uniformity, stability, good fluidity, and appropriate viscosity is prepared by using a wet homogenization method;

[0179] S13, the positive active material NCM83, the third solid-state electrolyte LPSCl (the average particle size is 1.0 μm), the conductive agent VGCF, the binder SBR are uniformly mixed with dimethylbenzene according to the mass ratio of NCM83:LPSCl:VGCF:SBR = 88:9:1.5:1.5, and the third electrode slurry with uniformity, stability, good fluidity and appropriate viscosity is prepared by the wet homogenization method;

[0180] S14, multi-layer coating multi-stage continuous hot rolling process: the first electrode slurry is coated on the positive current collector by using a coating machine, dried, and then rolled and densified to obtain a first sub-active material layer, the densification degree of the first sub-active material layer is 91%, the compaction density is 3.94 g / cm 3 , and the area density is 80 g / m 2 ; then the second electrode slurry is coated on the first sub-active material layer by using a coating machine, dried, and then rolled and densified to obtain a second sub-active material layer, the densification degree of the second sub-active material layer is 90%, the compaction density is 3.98 g / cm 3 , and the area density is 80 g / m 2 ; finally, the third electrode slurry is coated on the second sub-active material layer by using a coating machine, dried, and then rolled and densified to obtain a third sub-active material layer, the densification degree of the third sub-active material layer is 90%, the compaction density is 3.96 g / cm 3 , and the area density is 80 g / m 2 , thereby obtaining a pole piece, which is specifically a positive pole piece. In the positive pole piece, the thicknesses of the first sub-active material layer, the second sub-active material layer and the third sub-active material layer are equal.

[0181] Table 7

[0182]

[0183] Example 1

[0184] The present embodiment provides a solid-state battery, and a preparation process of the solid-state battery comprises:

[0185] S21, preparing a negative pole piece: the negative active material LTO, the conductive agent SP, the solid-state electrolyte Li6PS5Cl and the binder SBR are mixed with dimethylbenzene according to the mass ratio of 66:1.5:30:2.5 to obtain a negative electrode slurry, the negative electrode slurry is coated on a carbon-coated copper foil as a negative current collector, and the negative pole piece is obtained after baking and removing the solvent.

[0186] S22, preparing a solid-state battery: 100 mg of the solid-state electrolyte Li6PS5Cl is added into a solid-state prototype battery, and the powder is cold-pressed by a tablet machine at 400 MPa for more than 5 min; the positive pole piece provided in Preparation Example 1 is taken out. The positive electrode sheet is added to one side of the prototype battery, The negative electrode sheet is added to the other side of the prototype battery, and the sheet is cold-pressed at 400 MPa for more than 10 min to obtain a full solid-state battery, wherein the N / P ratio is 1.2.

[0187] Example 2

[0188] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Preparation Example 2, and the others are the same as in Example 1.

[0189] Example 3

[0190] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Preparation Example 3, and the others are the same as in Example 1.

[0191] Comparative Example 2A

[0192] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Comparative Example 1A, and the others are the same as in Example 1.

[0193] Comparative Example 2B

[0194] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Comparative Example 1B, and the others are the same as in Example 1.

[0195] Comparative Example 2C

[0196] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Comparative Example 1C, and the others are the same as in Example 1.

[0197] Comparative Example 2D

[0198] This example provides a solid-state battery, and the preparation process of the solid-state battery is different from that of Example 1 in that the positive electrode sheet is the positive electrode sheet provided in Comparative Example 1D, and the others are the same as in Example 1.

[0199] Test:

[0200] The full solid-state batteries provided in Examples 1 to 3 and Comparative Examples 2A to 2D are subjected to a pressure of 10 MPa by a clamp, and an electrochemical performance test is performed.

[0201] 1. Charge-discharge performance test: stand for 30 min, constant current and constant voltage charging: 0.1C constant current and constant voltage charging to 2.75V (cut-off current 0.05C), stand for 30 min, constant current discharging: 0.1C constant current discharging to 1.50V, obtain the first week charge specific capacity, the first week discharge specific capacity and the initial efficiency, which are recorded in Table 8.

[0202] 2. Cycle performance test: stand for 30 min, constant current and constant voltage charging: 1.0C constant current and constant voltage charging to 2.75V (cut-off current 0.05C), stand for 30 min, constant current discharging: 1.0C constant current discharging to 1.50V; cycle test: repeat the above steps, obtain the capacity of the 100th cycle and the capacity of the first cycle, and compare them to obtain the results recorded in Table 8.

[0203] Table 8

[0204]

[0205] From the test results in Table 8, it can be seen that:

[0206] Compared with Example 2, the formulation of each sub-active material layer in Example 1 remains the same, but the densification degree and the compaction density are different. Compared with Example 2, the densification degree and the compaction density of each sub-active material layer in Example 1 are higher, so that the densification degree and the compaction density of the active material layer are improved, and the specific capacity, the initial efficiency and the capacity retention rate of the solid-state battery are all significantly improved. This is because improving the compaction density of the active material layer can effectively improve the solid-solid contact effect between the active material and the solid-state electrolyte in the active material layer, promote the capacity of the electrode and improve the cycle performance. In Example 2, the porosity of the active material layer is high, so the contact between the active material inside the active material layer and the active material, the active material and the solid-state electrolyte, and the solid-state electrolyte and the solid-state electrolyte particles is poor, which causes some particles to be deactivated, and also causes the increase of ion and electron transmission tortuosity, so the performance is poorer.

[0207] Compared with Comparative Example 2C and Comparative Example 2D, the solid-state battery in Example 1 is superior in specific capacity, initial efficiency and capacity retention rate, which indicates that there is a synergistic effect between the content and particle size of the solid-state electrolyte between the sub-active material layers and the electrochemical performance of the solid-state battery is improved. The difference in different depth formulations (i.e. different formulations of sub-active material layers) affects the ion transmission effect. The high proportion of solid-state electrolyte in the first active material layer is more conducive to improving the utilization rate of active material at the depth of thick electrode and avoiding active material loss, which is beneficial to the higher capacity of the solid-state battery and the more stable capacity retention. The particle size of the solid-state electrolyte mainly affects the volume fraction of the solid-state electrolyte in the electrode and the grain boundary impedance. Specifically, when the particle size of the solid-state electrolyte in the second active material layer is reduced from 3 μm to 1 μm, i.e. the particle size of the solid-state electrolyte is reduced, the grain boundary impedance increases, and the ionic conductivity of the solid-state electrolyte decreases, and the rate performance may decrease; the particle size of the solid-state electrolyte in the third active material layer is increased from 0.5 μm to 1 μm, although the grain boundary impedance is reduced, the volume fraction of the solid-state electrolyte is reduced, and the contact area between the solid-state electrolyte and the active material is reduced.

[0208] Compared with Comparative Example 2A and Comparative Example 2B, the solid-state battery in Example 2 is superior in specific capacity, initial efficiency and capacity retention rate, which is because the layered setting in the active material layer and the independent rolling of each sub-active material layer to achieve densification can make the active material layer have a high compaction density at different thicknesses, that is, the uniformity of densification is improved, thereby improving the effect of solid-solid contact inside the electrode sheet, and further improving the electrochemical performance of the solid-state battery. Compared with Example 1 and Example 3, the specific capacity, initial efficiency and capacity retention rate of the solid-state battery in Example 1 are superior to those of Example 3, which indicates that by setting the third sub-active material layer with ultra-small particle size electrolyte, the volume fraction of the electrolyte on the surface of the electrode can be increased, more contact sites are provided, the interfacial impedance is reduced, and the electrochemical performance of the battery can be improved.

[0209] The embodiments of the present application are described in detail above, and the specific examples are applied to explain the principles and implementation modes of the present application; the above examples are only used to help understand the method and core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range can be changed, and the above description should not be understood as a limitation of the present application.

Claims

1. A pole piece, characterized in that: include: A current collector and an active material layer disposed on the current collector, wherein the active material layer comprises a plurality of sub-active material layers stacked in sequence, the sub-active material layers comprising active materials and having a compaction density greater than or equal to 2.50 g / cm 3 ; The multilayer sub-active material layer includes a first sub-active material layer and a second sub-active material layer arranged in sequence along a direction away from the current collector, the first sub-active material layer also contains a first solid electrolyte, the second sub-active material layer also contains a second solid electrolyte, the average particle size D2 of the second solid electrolyte is greater than the average particle size D1 of the first solid electrolyte, and the mass content W1 of the first solid electrolyte in the first sub-active material layer is greater than the mass content W2 of the second solid electrolyte in the second sub-active material layer.

2. The pole piece according to claim 1, characterized in that: The multi-layer sub-active material layer also includes a third sub-active material layer, which is arranged on a side of the second sub-active material layer away from the first sub-active material layer. The third sub-active material layer contains a third solid electrolyte, the average particle size D2 of the second solid electrolyte is greater than the average particle size D3 of the third solid electrolyte, and the mass content W1 of the first solid electrolyte in the first sub-active material layer is greater than the mass content W3 of the third solid electrolyte in the third sub-active material layer.

3. The pole piece according to claim 2, characterized in that: The active material includes a positive electrode active material, and the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide and lithium-rich manganese-based materials.

4. The pole piece according to claim 3, characterized in that: The surface of the positive electrode active material is coated with a coating layer, and the coating layer contains at least one of Li3PO4, LiNbO3, Li4Ti5O2, Li2ZrO3 and Li3BO3.

5. The pole piece according to any one of claims 2 to 4, characterized in that: The first sub-active material layer, the second sub-active material layer, and the third sub-active material layer each further include a conductive agent and a binder.

6. The pole piece according to claim 5, characterized in that: The binder includes at least one of polytetrafluoroethylene, styrene-butadiene rubber, nitrile rubber, polyvinylidene fluoride, polyisobutylene, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer and hydrogenated styrene-butadiene block copolymer.

7. The pole piece according to claim 6, characterized in that: In the first sub-active material layer, the second sub-active material layer, and the third sub-active material layer, the binder has a mass content of 0.5 wt % to 10 wt %.

8. The pole piece according to claim 5, characterized in that: The conductive agent includes at least one of conductive carbon black, carbon nanotubes, carbon nanofibers, graphite and graphene.

9. The pole piece according to any one of claims 2 to 4, characterized in that: The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each independently include at least one of a sulfide solid electrolyte, a halide solid electrolyte, and an oxide solid electrolyte.

10. The pole piece according to claim 9, characterized in that: The sulfide solid electrolyte includes Li 7-a PS 6-a X a 、Li3PS4、Li4SnS4、75Li2S-25P2S5、Li7SiPS8、and Li 10 GeP2S 12 At least one of, wherein X is a halogen element, a is 0.8 to 2.0; and / or, The halide solid electrolyte includes Li b MY4, Li b MY6, Li b MY8, and at least one of a halide oxide electrolyte, wherein M is an alkali metal element and Y is a halogen element; and / or, The oxide solid electrolyte includes at least one of a garnet-type oxide solid electrolyte, a NASICON-type oxide solid electrolyte, and a perovskite-type oxide solid electrolyte.

11. The pole piece according to any one of claims 2 to 4, characterized in that: The average particle size D1 of the first solid electrolyte is 0.2 μm to 20 μm; and / or The average particle size D2 of the second solid electrolyte is 0.5 μm to 20 μm; and / or The average particle size D3 of the third solid electrolyte is 0.5 μm to 10 μm.

12. The pole piece according to claim 11, characterized in that: The average particle size D1 of the first solid electrolyte is 0.5 μm to 10 μm; and / or The average particle size D2 of the second solid electrolyte is 1 μm to 8 μm; and / or The average particle size D3 of the third solid electrolyte is 0.5 μm to 5 μm.

13. The pole piece according to any one of claims 2 to 4, characterized in that: The mass content W1 of the first solid electrolyte is 1 wt% to 40 wt%; and / or The mass content W2 of the second solid electrolyte is 1 wt% to 40 wt%; and / or The mass content W3 of the third solid electrolyte is 1 wt% to 40 wt%.

14. The pole piece according to claim 13, characterized in that: The mass content W1 of the first solid electrolyte is 7wt% to 30wt%; and / or The mass content W2 of the second solid electrolyte is 5wt% to 30wt%; and / or The mass content W3 of the third solid electrolyte is 5 wt % to 20 wt %.

15. The pole piece according to any one of claims 2 to 4, characterized in that: The surface density of the active material layer is 100 g / m 2 ~300g / m 2 and / or The surface density of the first sub-active material layer is 30 g / m 2 ~150g / m 2 and / or The surface density of the second sub-active material layer is 30 g / m 2 ~150g / m 2 and / or The surface density of the third sub-active material layer is 30 g / m 2 ~150g / m 2 .

16. The pole piece according to any one of claims 2 to 4, characterized in that: The compaction density of the first sub-active material layer is 2.64 g / cm 3 ~4.49g / cm 3 and / or The compaction density of the second sub-active material layer is 2.64 g / cm 3 ~4.55g / cm 3 and / or The compaction density of the third sub-active material layer is 2.85 g / cm 3 ~4.55g / cm 3 .

17. The pole piece according to any one of claims 2 to 4, characterized in that: The thickness of the active material layer is 45 μm to 240 μm; and / or The thickness of the first sub-active material layer is 15 μm to 80 μm; and / or The thickness of the second sub-active material layer is 15 μm to 80 μm; and / or The thickness of the third sub-active material layer is 15 μm to 80 μm.

18. A method for preparing a pole piece, characterized in that: include: providing a current collector; Providing a first slurry, wherein the first slurry includes a first solid electrolyte, and performing a first film-forming process and a first roll-pressing process on the first slurry on the current collector to obtain a first sub-active material layer; A second slurry is provided, wherein the second slurry includes a second solid electrolyte, and the average particle size D2 of the second solid electrolyte is greater than the average particle size D1 of the first solid electrolyte; the second slurry is subjected to a second film-forming treatment and a second rolling treatment on the first sub-active material layer to obtain a second sub-active material layer, and the mass content W1 of the first solid electrolyte in the first sub-active material layer is greater than the mass content W2 of the second solid electrolyte in the second sub-active material layer.

19. The method for preparing a pole piece according to claim 18, characterized in that: The method for preparing the pole piece further includes: A third slurry is provided, wherein the third slurry includes a third solid electrolyte, and the average particle size D2 of the second solid electrolyte is greater than the average particle size D3 of the third solid electrolyte; the third slurry is subjected to a third film-forming treatment and a third rolling treatment on the second sub-active material layer to obtain a third sub-active material layer, and the mass content W1 of the first solid electrolyte in the first sub-active material layer is greater than the mass content W3 of the third solid electrolyte in the third sub-active material layer.

20. A solid-state battery, characterized in that: It includes a positive electrode, a negative electrode and a solid electrolyte membrane located between the positive electrode and the negative electrode, at least one of the positive electrode and the negative electrode includes the electrode piece according to any one of claims 1 to 17 or the electrode piece prepared by the method for preparing the electrode piece according to claim 18 or 19.

21. The solid-state battery according to claim 20, characterized in that The negative electrode includes at least one of a lithium metal negative electrode, a silicon negative electrode, a silver-carbon negative electrode, a lithium titanate negative electrode and a lithium alloy negative electrode.

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