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

Abstract

The invention provides a positive plate, a preparation method thereof and an all-solid-state battery. The positive plate comprises a buffer assembly, and the buffer assembly comprises a buffer frame and a buffer layer located on at least one side of the buffer frame; the buffer assembly is arranged on at least one side of the positive electrode current collector, and the buffer assembly is circumferentially arranged on the edge of the positive electrode active material layer; the buffer layer is arranged at the contact position between the buffer frame and the positive pole lug, the buffer layer is attached to the positive pole lug, and the ratio of the length of the buffer layer in the first direction to the length of the positive pole lug in the first direction is 52: (1-50). The buffer assembly provided by the invention not only can improve the interface contact performance between the electrode and the solid electrolyte, avoid the contact short circuit of the positive and negative electrodes due to deformation and effectively improve the safety of the battery, but also can provide a space for accommodating the tab in the subsequent isostatic pressing process, reduce the risk of tab breakage and improve the qualification rate and the product quality of the battery.

Description

Technical Field

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

[0002] All-solid-state batteries are a battery technology that uses solid electrolytes to replace traditional separators and liquid electrolytes. They have significant advantages such as high energy density, high safety and long life, making them a promising technology for applications in new energy vehicles, energy storage systems and consumer electronics. However, solid electrolytes still have some problems in application, such as: (1) the mechanical strength of solid electrolyte membranes is usually lower than that of traditional separators, which makes them prone to short circuits during battery operation; (2) unlike the solid-liquid interface contact in liquid batteries, the solid-solid interface contact in all-solid-state batteries requires higher pressure to achieve good interface contact and ion transport performance.

[0003] Specifically, during the assembly and operation of all-solid-state batteries, the different material properties of the positive electrode, solid electrolyte, and negative electrode lead to variations in their mechanical behavior under external pressure. For example, when a large pressure is applied to the cell, the edges of the positive electrode are prone to collapse and deformation, resulting in porosity between the electrode and the solid electrolyte. This can further cause the electrode to crack or even shatter under pressure, ultimately leading to a short circuit. Furthermore, the interface between the solid electrolyte and the positive and negative electrodes is typically a hard contact, which easily leads to stress accumulation and cracks in the electrode and electrolyte layers. The dimensional differences between the positive and negative electrodes can also generate significant shear stress at the edges of the layers. This stress can cause the electrode edges to tear or even penetrate the solid electrolyte, creating defects in the all-solid-state battery structure and further exacerbating the risk of short circuits.

[0004] In addition to the issues mentioned above, the tabs of all-solid-state batteries also face several challenges. Specifically, variations in tab thickness directly affect the current density and temperature distribution of the battery, leading to aging and failure. Furthermore, uneven tab thickness can cause them to be subjected to greater localized forces during battery assembly and operation, potentially resulting in breakage and consequently reducing the yield and safety of all-solid-state batteries.

[0005] Therefore, optimizing the interfacial contact between the electrode and the solid electrolyte, and ensuring good structural stability and integrity of the electrode and tab, thereby comprehensively improving the safety and cycle life of all-solid-state batteries, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of existing technologies and to solve the technical problems of poor interfacial performance between the electrode and the solid electrolyte membrane, as well as the high assembly stress in all-solid-state batteries that makes the electrodes and tabs prone to deformation or even breakage, this invention aims to provide a positive electrode sheet, its preparation method, and an all-solid-state battery. This ensures sufficient strength, allowing the electrode to maintain its shape at high temperatures, preventing short circuits due to deformation of the positive and negative electrodes, and effectively improving the safety of the all-solid-state battery. Simultaneously, the compression deformation of the buffer layer material during the subsequent isostatic pressing process provides space to accommodate the tabs, reducing the risk of tab breakage and improving the yield rate and product quality of the all-solid-state battery.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein a positive electrode tab is provided on the positive electrode current collector.

[0009] The positive electrode includes a buffer assembly, which includes a buffer frame and a buffer layer located on at least one side of the buffer frame;

[0010] The buffer component is disposed on at least one side of the positive electrode current collector, and the buffer component is circumferentially disposed at the edge of the positive electrode active material layer;

[0011] The buffer layer is disposed at the contact position between the buffer frame and the positive electrode tab, and the buffer layer is in contact with the positive electrode tab. The ratio of the length of the buffer layer in the first direction to the length of the positive electrode tab in the first direction is 52:(1~50).

[0012] Preferably, the tensile strength of the buffer frame is 130MPa to 170MPa.

[0013] Preferably, the elastic modulus of the buffer frame is 2000MPa to 6000MPa.

[0014] Preferably, the material of the buffer frame is selected from any one or a combination of at least two of polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyimide or polycarbonate;

[0015] Preferably, the thickness of the buffer frame satisfies the following relationship: 5μm≤D1≤(D2-9)μm, where D1 is the thickness of the buffer frame in μm and D2 is the thickness of the positive electrode active material layer in μm.

[0016] Preferably, the material of the buffer layer is selected from functional materials with elastic deformation.

[0017] Preferably, the tensile strength of the functional material with elastic deformation is 10 MPa to 150 MPa.

[0018] Preferably, the elastic modulus of the functional material with elastic deformation is 10 MPa to 1000 MPa.

[0019] Preferably, the functional material with elastic deformation is selected from any one or a combination of at least two of thermoplastic polyurethane elastomers, polydimethylsiloxane, polyolefin elastomers, ethylene-vinyl acetate elastomers, polyurethane elastomers, polyethylene, polypropylene, or nonwoven fabrics.

[0020] Preferably, the thickness of the buffer layer is 10μm to 150μm.

[0021] In a second aspect, the present invention provides a method for preparing a positive electrode sheet as described in the first aspect, the method comprising the following steps:

[0022] By combining at least one side of the buffer border with the buffer layer, a buffer component is obtained;

[0023] The positive current collector, which has a positive active material layer on at least one side, is pressed with the buffer assembly so that the inner wall of the buffer frame is in close contact with the edge of the positive active material layer, and the buffer layer is attached to the surface of the positive current collector or the positive electrode tab to obtain the positive electrode sheet.

[0024] Preferably, after the pressing process is completed, the total thickness of the buffer assembly after pressing is less than or equal to the thickness of the positive electrode active material layer.

[0025] Thirdly, the present invention provides an all-solid-state battery, the all-solid-state battery comprising a positive electrode, a negative electrode and a solid electrolyte membrane, wherein the positive electrode comprises a positive electrode prepared by the preparation method described in the first aspect or the second aspect.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides a positive electrode sheet. By adjusting the structure and composition of the buffer assembly, the interface between the positive electrode material and the solid electrolyte can be made more stable. Furthermore, while ensuring good structural stability of the electrodes and tabs, it can further alleviate the short-circuit problem caused by electrode size mismatch during isostatic pressing of all-solid-state batteries, thereby reducing the short-circuit risk of the battery. Specifically, the following are the key features:

[0028] (1) The buffer component provided by the present invention can fill the interfacial gap between the positive electrode material and the solid electrolyte membrane, improve the interfacial contact between the positive electrode material and the solid electrolyte membrane, reduce the interfacial impedance, reduce the risk of short circuit, and improve the cycle stability and safety of the all-solid-state battery.

[0029] (2) The buffer component provided by the present invention has both suitable flexibility and mechanical strength, effectively alleviates the volume change of the positive electrode material during charging and discharging, thereby preventing the electrode from cracking due to volume expansion and improving the structural stability of the all-solid-state battery.

[0030] (3) The buffer component provided by the present invention can not only prevent the edge of the electrode from collapsing and deforming during the isostatic pressing process, causing the battery to short-circuit and fail, but also avoid the tab breakage and improve the yield of all-solid-state battery manufacturing. Attached Figure Description

[0031] Figure 1 A schematic diagram of the structure of the all-solid-state battery made from the buffer component provided by the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] Among them, 10 is the positive electrode, 20 is the buffer component, 30 is the negative electrode, 110 is the positive electrode tab, 210 is the buffer layer, and 310 is the negative electrode tab. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and related drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in the detailed description is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0036] In the description of specific embodiments of the present invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, "multiple" means two or more, unless otherwise explicitly defined.

[0037] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0038] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this invention, the character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0039] Throughout this invention, numerical values ​​represent approximate measurements or limits of a range to cover minute deviations from a given value, as well as embodiments with approximately the mentioned value and embodiments with the exact mentioned value. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., quantities or conditions) in this specification (including the appended claims) should be understood to be modified in all cases by the term “about,” regardless of whether “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows for some minor inaccuracy (approaching the exact value in some way; approximately or reasonably approaching the value; almost). If the inaccuracy provided by “about” is not otherwise understood in this general sense in the art, then “about” as used in this invention at least indicates a variation that can be produced by common methods of measuring and using such a parameter. For example, “about” may include a variation less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some respects, optionally less than or equal to 0.1%.

[0040] Additionally, the disclosure of the range includes the disclosure of all values ​​across the entire range and the disclosure of further subdivided ranges, including the endpoints and subranges given for these ranges.

[0041] Currently, all-solid-state batteries face two main problems in their application: Firstly, the use of solid electrolytes instead of liquid electrolytes in all-solid-state batteries results in poor interfacial compatibility between the electrodes and the solid electrolyte, which can easily lead to voids or poor contact, thus affecting the electrochemical performance of the battery.

[0042] On the other hand, in the production process of all-solid-state batteries, significant pressure needs to be applied to the electrode components to achieve solid-solid interface bonding and maintain structural stability. Currently, this significant pressure is mainly achieved using isostatic pressing. Therefore, during isostatic pressing production, the electrodes and tabs are subjected to high pressure, causing deformation or rupture, which can lead to battery short circuits and reduce the yield of finished batteries.

[0043] To solve the above problems, such as Figure 1 As shown, in one embodiment of the present invention, a positive electrode sheet 10 is provided, including a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. A positive electrode tab 110 is provided on the positive electrode current collector.

[0044] The positive electrode 10 includes a buffer assembly 20, which includes a buffer frame and a buffer layer 210 located on at least one side of the buffer frame;

[0045] The buffer component 20 is disposed on at least one side of the positive electrode current collector, and the buffer component 20 is circumferentially disposed at the edge of the positive electrode active material layer;

[0046] The buffer layer 210 is disposed at the contact position between the buffer frame and the positive electrode tab 110, and the buffer layer 210 is attached to the positive electrode tab 110. The ratio of the length of the buffer layer 210 in the first direction to the length of the positive electrode tab 110 in the first direction is 52:(1~50).

[0047] This invention introduces a buffer component with a specific structure into the positive electrode sheet, which facilitates the formation of a tightly bonded interface and avoids the formation of voids and pores at the interface, thereby improving the safety and cycle performance of the all-solid-state battery. Furthermore, this buffer component also provides additional support and further regulates the ratio of the length of the buffer layer in the first direction to the length of the positive electrode tab in the first direction, ensuring that the electrode sheet and tab maintain a good shape at high temperatures. This prevents abnormalities such as short circuits at the positive and negative electrode connections and tab breakage caused by the collapse and deformation of the electrode assembly edges due to isostatic pressing, thus improving the production yield of the electrode assembly.

[0048] In this invention, the ratio of the length of the buffer layer 210 in the first direction to the length of the positive electrode tab 110 in the first direction is 52:(1-50), preferably 52:(25-50), and for example, it can be 52:1, 26:1, 13:1, 26:3, 52:9, 52:15, 13:5, 52:25, 52:35, 52:41, 52:41, 52:47, 13:12, or 26:25, etc. The above values ​​are only examples and are not limiting.

[0049] In one embodiment, the tensile strength of the buffer frame is 130MPa to 170MPa, for example, it can be 130MPa, 140MPa, 150MPa, 160MPa or 170MPa. The above values ​​are only examples and are not limitations.

[0050] In one embodiment, the elastic modulus of the buffer frame is 2000MPa to 6000MPa, for example, it can be 2000MPa, 3000MPa, 4000MPa, 5000MPa or 6000MPa. The above values ​​are only examples and are not limitations.

[0051] In this invention, the buffer frame can withstand a high pressure of 100 MPa during the nail puncture test.

[0052] In this invention, by adjusting the specific physical properties of the buffer frame, it is made to have high mechanical strength and good buffering performance, thereby helping to improve the overall performance and structural stability of the all-solid-state battery.

[0053] In one embodiment, the material of the buffer frame is selected from any one or a combination of at least two of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyimide (PI), or polycarbonate (PC).

[0054] In this invention, by selecting the aforementioned high-temperature resistant hard material, the stability of the all-solid-state battery at high temperatures is improved.

[0055] In one embodiment, the thickness of the buffer border satisfies the following relationship: 5μm≤D1≤(D2-9)μm, where D1 is the thickness of the buffer border in μm and D2 is the thickness of the positive electrode active material layer in μm.

[0056] In this invention, the buffer border can be a two-layer or multi-layer structure, and the composition of each layer can be the same or different. This invention does not limit this.

[0057] In one embodiment, the material of the buffer layer 210 is selected from a functional material with elastic deformation. The present invention uses a functional material with controllable deformation characteristics, which provides dynamic accommodation space for the tabs through elastic deformation, preventing the tabs from breaking due to uneven stress.

[0058] In one embodiment, the tensile strength of the functional material with elastic deformation is 10 MPa to 150 MPa, for example, it can be 10 MPa, 20 MPa, 50 MPa, 80 MPa, 100 MPa, 120 MPa or 150 MPa. The above values ​​are only examples and are not limiting.

[0059] In one embodiment, the elastic modulus of the functional material with elastic deformation is 10 MPa to 1000 MPa, for example, it can be 10 MPa, 20 MPa, 50 MPa, 80 MPa, 100 MPa, 200 MPa, 500 MPa, 800 MPa or 1000 MPa, etc. The above values ​​are only examples and are not limited.

[0060] In this invention, by adjusting the specific physical properties of the functional material with elastic deformation, it can be made to have suitable elasticity and mechanical strength, which can not only play a good buffering role, but also provide a space for the tabs, thereby improving the reliability and safety of the all-solid-state battery.

[0061] In one embodiment, the functional material with elastic deformation is selected from any one or a combination of at least two of thermoplastic polyurethane elastomer (TPU), polydimethylsiloxane (PDMS), polyolefin elastomer (POE), ethylene-vinyl acetate elastomer (EVA), polyurethane elastomer (PU), polyethylene (PE), polypropylene (PP), or nonwoven fabric.

[0062] In this invention, by selecting the above-mentioned specific types of functional materials with elastic deformation, they are made to have high mechanical strength and good buffering performance, thereby helping to improve the overall performance and structural stability of all-solid-state batteries.

[0063] In one embodiment, the thickness of the buffer layer 210 is 10 μm to 150 μm, preferably 20 μm to 130 μm, and can be, for example, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, or 150 μm. The above values ​​are merely examples and are not intended to be limiting.

[0064] In this invention, by adjusting the thickness of the buffer frame and the buffer layer to satisfy the relationship described above, the main purpose is to ensure that the thickness of the buffer component is less than or equal to the thickness of the positive electrode active material layer after subsequent pressing, so that the buffer component is within the deformation range and can accommodate the thickness of the tab.

[0065] In this invention, the outer side length of the buffer frame can be greater than, equal to or less than the outer side length of the negative electrode 30, and this invention does not impose any restrictions on this.

[0066] In this invention, the compressive strength of the positive current collector is 100MPa to 200MPa, for example, it can be 100MPa, 120MPa, 150MPa, 180MPa or 200MPa. The above values ​​are only examples and are not limitations.

[0067] In this invention, the thickness of the positive electrode current collector is 10 μm to 20 μm, for example, it can be 10 μm, 12 μm, 15 μm, 18 μm or 20 μm, etc. The above values ​​are only examples and are not limitations.

[0068] The present invention also provides a method for preparing the above-mentioned positive electrode sheet, the method comprising the following steps:

[0069] By combining at least one side of the buffer border with the buffer layer, a buffer component is obtained;

[0070] A positive current collector with a positive active material layer on at least one side is pressed together with a buffer assembly, so that the inner wall of the buffer frame is in close contact with the edge of the positive active material layer, and the buffer layer is attached to the surface of the positive current collector or the positive electrode tab, thus obtaining a positive electrode sheet.

[0071] In this invention, the pressing temperature is 75℃~85℃, for example, it can be 75℃, 78℃, 80℃, 82℃ or 85℃, etc. The above values ​​are only examples and are not limited.

[0072] In this invention, the pressure for the pressing process is 2 MPa to 5 MPa, for example, it can be 2 MPa, 3 MPa, 4 MPa or 5 MPa, etc. The above values ​​are only examples and are not limitations.

[0073] In this invention, the pressing process includes, for example, hot pressing.

[0074] In this invention, under a pressure of 2MPa to 5MPa, the buffer assembly of the above-mentioned positive electrode sheet is within a suitable deformation range, which can better accommodate the positive electrode tab.

[0075] In this invention, the pressing time is 15 min to 25 min, for example, 15 min, 18 min, 20 min, 22 min, or 25 min. The above values ​​are merely examples and are not intended to be limiting.

[0076] In one embodiment, after the pressing process is completed, the total thickness of the buffer component 20 after pressing is less than or equal to the thickness of the positive electrode active material layer.

[0077] In one embodiment, the deformation thickness of the buffer component is greater than half the thickness of the positive electrode tab.

[0078] In one embodiment, the deformation thickness of the buffer component is 5μm to 20μm, for example, it can be 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm, etc. The above values ​​are only examples and are not limitations.

[0079] The present invention also provides an all-solid-state battery, which includes the above-mentioned positive electrode, negative electrode and solid electrolyte membrane.

[0080] It is understood that the present invention does not impose any particular limitations on the positive electrode current collector material, as long as it is conductive and does not cause chemical changes in the battery. For example, the positive electrode current collector may include, but is not limited to, any one of aluminum, nickel, or stainless steel, such as aluminum foil.

[0081] It is understood that the present invention does not impose any particular limitation on the shape of the positive electrode current collector. For example, the shape of the positive electrode current collector includes, but is not limited to, metal foil, metal grid, metal mesh, etc.

[0082] It is understood that the positive electrode active material is a compound that reversibly inserts and deinserts lithium, and the positive electrode active material in this invention can be any positive electrode active material known in the art. For example, the positive electrode active material can be selected from lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium iron phosphate, lithium titanate, or lithium-rich manganese elastic base materials, etc.

[0083] In one embodiment, the negative electrode sheet 30 includes a negative electrode current collector and a negative electrode active material layer covering at least one side surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive agent. A negative electrode tab 310 is provided on the negative electrode current collector.

[0084] It is understood that the present invention does not impose any particular limitations on the negative electrode current collector material, as long as it is conductive and does not cause chemical changes in the battery. For example, the negative electrode current collector may include, but is not limited to, any one of copper, nickel, or stainless steel, such as copper foil.

[0085] It is understood that the present invention does not impose any particular limitation on the shape of the negative electrode current collector. For example, the shape of the negative electrode current collector includes, but is not limited to, metal foil, metal grid, metal mesh, etc.

[0086] It is understood that the negative electrode active material is a compound that reversibly inserts and deinserts lithium, and the negative electrode active material in this invention can be any negative electrode active material known in the art. For example, the negative electrode active material can be selected from natural graphite, artificial graphite, hard carbon, soft carbon, silicon-based materials, titanium-based materials, tin-based materials, and metallic lithium, etc.

[0087] It is understood that this invention does not specifically limit the type of conductive agent; the positive electrode active material layer and the negative electrode active material layer may use the same conductive agent or different conductive agents. Exemplarily, it includes at least one of carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Examples include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, acetylene black, carbon nanotubes, carbon nanofibers, polyaniline, polythiophene, polyacetylene, polypyrrole, or poly(3,4-ethylenedioxythiophene)polysulfonated styrene, etc.

[0088] It is understood that this invention does not specifically limit the type of binder. Any binder capable of bonding and maintaining the active material, enhancing the contact between the active material and the conductive agent, and between the active material and the current collector, thereby stabilizing the electrode structure, without departing from the concept of this invention, is within the scope of protection of this invention. The positive electrode active material layer and the negative electrode active material layer may use the same binder or different binders. Exemplarily, it includes thermoplastic resins or thermosetting resins. Examples include polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, etc.

[0089] In one embodiment, the solid electrolyte membrane may also include, but is not limited to, polymer solid electrolytes, oxide solid electrolytes, or sulfide solid electrolytes.

[0090] In specific applications, sulfide solid electrolytes can be selected from: Li2S-P2S5, Li2S-P2S5-MS. x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 Li 9.6 P3S 12 Li7P3S 11 Li9P3S9O3, Li 10.35 Si 1.35 P 1.65 S 12 Li 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si 0.5 Ge 0.5 P2S 12 Li (Ge 0.5 Sn 0.5 P2S 12 Li(Si) 0.5 Sn 0.5 PS 12 Li 10 GeP2S 12(LGPS), Li6PS5X (where X is Cl, Br or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 、Li 10 SiP2S 12 、Li 9.54 Si<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In a preferred embodiment, the solid electrolyte material is used in conjunction with the lithium metal anode as a reduction-resistant layer material. The solid electrolyte material has high reduction resistance and is characterized as being stable to Li and having high ionic conductivity. It can optimize the performance of the lithium metal anode, promote the application of lithium metal anodes and the development of high-energy lithium metal batteries.

[0095] For example, the present invention also provides a method for preparing the above-mentioned all-solid-state battery, the method comprising the following steps:

[0096] By combining the above-mentioned positive electrode, solid electrolyte membrane and negative electrode, an all-solid-state battery is obtained.

[0097] In one embodiment, the composite treatment includes isostatic pressing.

[0098] The embodiments of the present invention do not impose specific limitations on the manufacturing process of all-solid-state batteries, and can be applied to battery structures such as wound batteries (e.g., cylindrical batteries), stacked batteries (e.g., prismatic batteries, pouch batteries) and other composite structure batteries (e.g., bipolar batteries, modular batteries).

[0099] The embodiments of this invention are applicable to any tab structure, including but not limited to traditional monopole, all-pole, composite, cut tab, and multi-layer tabs. This invention is applicable to both monopole and multipole designs. For specially designed tab structures (those with complex shapes formed through cutting and angle optimization), the buffer components can be adjusted and optimized according to specific circumstances.

[0100] The beneficial effects of the present invention will be further illustrated below with reference to embodiments and comparative examples.

[0101] Example 1

[0102] 1. Preparation of positive electrode sheet

[0103] The positive electrode includes an aluminum foil current collector and a positive electrode active material layer disposed on one side of the aluminum foil current collector, with a positive electrode tab on the aluminum foil current collector. Based on 100% of the total mass of the positive electrode active material layer, the positive electrode active material layer comprises the following components: 95 wt% LiNi 0.8 Mn 0.1 Co 0.1 O2 positive electrode active material, 3 wt% conductive carbon black (Super P) and 2 wt% polyvinylidene fluoride (PVDF).

[0104] The positive electrode also includes a buffer assembly, which comprises a polyethylene terephthalate (PET) buffer frame and a buffer layer located on one side of the PET buffer frame. The PET buffer frame is disposed on one side of the aluminum foil current collector and is circumferentially disposed at the edge of the positive electrode active material layer; the buffer layer is disposed at the contact position between the PET buffer frame and the positive electrode tab, and is attached to the positive electrode tab. The material of the buffer layer is thermoplastic polyurethane elastomer (TPU).

[0105] Among them, in the buffer assembly, the tensile strength of the buffer frame is 150MPa, the elastic modulus is 4000MPa, and the thickness is 115μm; the TPU in the buffer layer has a melting point of 150℃, a tensile strength of 80MPa, an elastic modulus of 500MPa, and a thickness of 100μm.

[0106] This embodiment provides a method for preparing the above-mentioned positive electrode sheet, which includes the following steps:

[0107] According to the formula amount, LiNi 0.8 Mn 0.1 Co 0.1 O2 positive electrode active material, Super P, and PVDF were dry-mixed at 1200 rpm for 15 min. After drying, sieving, and compaction, the mixture was cut into positive electrode active material layers with dimensions of 5 cm × 6 cm and a thickness of 180 μm using a cutting die. Simultaneously, aluminum foil current collectors with dimensions of 5.2 cm × 6.2 cm were cut, with a thickness of 12 μm and a compressive strength of 110 MPa.

[0108] A 100μm thick TPU buffer layer was stacked on a 115μm thick dense, non-porous PET buffer frame. The length of the TPU buffer layer in the first direction was 10mm, and the length of the positive electrode tab in the first direction was 5.2mm, with a ratio of 25:13. The composite material was then cured and bonded using UV-curable adhesive. A cutting die was used to cut the composite material into rectangular buffer assemblies with an inner frame size of 5cm × 6cm and an outer frame size of 6cm × 7cm.

[0109] The positive electrode active material layer, aluminum foil current collector, and rectangular buffer assembly are hot-pressed and stacked to ensure that the inner wall of the rectangular buffer frame is in close contact with the edge of the positive electrode active material layer. The TPU buffer layer is placed on the side close to the aluminum foil current collector and directly contacts the positive electrode tab. After completion, the above composite structure is placed between two PTFE release sheets and hot-pressed on a flat plate at 80°C and 2MPa for 20 minutes. After cooling to room temperature, the two PTFE release sheets are peeled off to obtain the positive electrode sheet.

[0110] 2. Preparation of negative electrode sheet

[0111] The negative electrode sheet includes a copper foil current collector and a negative electrode active material layer disposed on one side of the copper foil current collector. Based on the total mass of the negative electrode active material layer (100%), the negative electrode active material layer comprises the following components: 93 wt% negative electrode active material, 0.2 wt% conductive carbon black (Super P), 1 wt% single-walled carbon nanotubes (SWCNTs), 4.5 wt% polyacrylic acid (PAA), and 1.3 wt% carboxymethyl cellulose (CMC). The negative electrode active material is composed of 50% silicon dioxide (SiO₂) by mass. x It consists of 50% graphite and 50% graphite.

[0112] This embodiment also provides a method for preparing the above-mentioned negative electrode sheet, which includes the following steps:

[0113] The above-mentioned amounts of negative electrode active material, Super P, SWCNT, PPA and CMC are mixed to prepare a negative electrode active material layer slurry. Then, the negative electrode active material layer slurry is coated onto the surface of the copper foil current collector using a coating machine, thereby forming a negative electrode active material layer on the surface of the copper foil current collector. After baking and rolling, a negative electrode sheet is obtained, which is then cut into a negative electrode sheet with a size of 5.5cm × 6.5cm using a cutting die.

[0114] 3. Preparation of solid electrolyte membranes

[0115] The Li6PS5Cl solid electrolyte membrane was cut into 6cm×7cm pieces using a cutting die.

[0116] 4. Fabrication of all-solid-state batteries

[0117] The positive electrode, Li6PS5Cl solid electrolyte membrane, and negative electrode are stacked concentrically in sequence, with the Li6PS5Cl solid electrolyte membrane placed between the positive and negative electrode. After tab welding, the electrode is placed in an aluminum-plastic film, vacuumed, and then heat-sealed to obtain the battery cell.

[0118] After encapsulation, the cells are subjected to isostatic pressing at 80°C and 500MPa for 5 minutes to obtain a solid-state battery. Before reaching the compressive strength of 100MPa for the aluminum foil current collector, the deformation thickness of the TPU buffer layer is greater than half the thickness of the positive electrode tab, thus providing space to accommodate the positive electrode tab.

[0119] Example 2

[0120] The difference between this embodiment and Embodiment 1 is that the material of the buffer layer in the buffer assembly is replaced with polyolefin elastomer (POE), which has a melting point of 60°C, a tensile strength of 20 MPa, and an elastic modulus of 15 MPa. All other aspects are the same as in Embodiment 1.

[0121] Example 3

[0122] The difference between this embodiment and Embodiment 1 is that the material of the buffer layer in the buffer assembly is replaced with a polyethylene film (PE film) with a melting point of 120°C, a tensile strength of 30 MPa, and an elastic modulus of 300 MPa. All other aspects are the same as in Embodiment 1.

[0123] Example 4

[0124] The difference between this embodiment and Embodiment 1 is that the material of the buffer layer in the buffer assembly is replaced with polyurethane elastomer (PU), which has a melting point of 120°C, a tensile strength of 35 MPa, and an elastic modulus of 400 MPa. All other aspects are the same as in Embodiment 1.

[0125] Example 5

[0126] The difference between this embodiment and Embodiment 1 is that the buffer assembly includes a polyethylene terephthalate (PET) buffer frame, a first buffer layer located on one side of the PET buffer frame, and a second buffer layer located on the other side of the PET buffer frame. The material, thickness, and preparation method of the second buffer layer are the same as those of the first buffer layer, and everything else is the same as in Embodiment 1.

[0127] Example 6

[0128] The difference between this embodiment and Embodiment 1 is that the material of the buffer frame in the buffer assembly is replaced with polycarbonate (PC), with a tensile strength of 170 MPa and an elastic modulus of 2300 MPa. All other aspects are the same as in Embodiment 1.

[0129] Example 7

[0130] The difference between this embodiment and Embodiment 1 is that the length of the TPU buffer layer in the first direction is 3mm, and the length of the positive electrode tab in the first direction is 2mm, that is, the ratio is 3:2.

[0131] Example 8

[0132] The difference between this embodiment and Embodiment 1 is that the length of the TPU buffer layer in the first direction is 50mm, and the length of the positive electrode tab in the first direction is 10mm, that is, the ratio is 5:1.

[0133] Comparative Example 1

[0134] The difference between this comparative example and Example 1 is that the buffer assembly only includes a PET buffer frame and does not have a TPU buffer layer; otherwise, it is the same as Example 1.

[0135] Comparative Example 2

[0136] The difference between this comparative example and Example 1 is that the buffer assembly only includes a TPU buffer layer and does not have a PET buffer border; otherwise, it is the same as Example 1.

[0137] Comparative Example 3

[0138] The difference between this comparative example and Example 1 is that the length of the TPU buffer layer in the first direction is 10mm, and the length of the positive electrode tab in the first direction is 15mm, that is, the ratio is 2:3.

[0139] The all-solid-state batteries provided in Examples 1-8 and Comparative Examples 1-3 were subjected to product yield and performance tests under the following conditions:

[0140] Product qualification rate: The all-solid-state batteries under test were tested using a battery tester. 120 batteries were tested and the product qualification rate was calculated.

[0141] The test results are shown in Table 1:

[0142] Table 1

[0143]

[0144]

[0145] As can be seen from Table 1, in the present invention, by introducing a buffer component with a specific structure into the positive electrode sheet, the embodiments 1 to 8 can provide additional support, ensuring that the positive electrode sheet and the positive electrode tab can still maintain a good shape at high temperature, thereby avoiding abnormalities such as short circuits between positive and negative electrodes and electrode tab breakage caused by the collapse and deformation of the electrode assembly edge due to isostatic pressure, and improving the product qualification rate of the electrode assembly.

[0146] Comparing Example 1 and Comparative Examples 1 to 2, it can be seen that setting only a single buffer component cannot significantly improve the product manufacturing yield.

[0147] Comparing Example 1 and Comparative Example 3, it can be seen that the present invention improves the product qualification rate by adjusting the ratio of the length of the buffer layer in the first direction to the length of the positive electrode tab in the first direction.

[0148] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A positive electrode sheet, comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive current collector is provided with a positive electrode tab, characterized in that: The positive electrode includes a buffer assembly, which includes a buffer frame and a buffer layer located on at least one side of the buffer frame; The buffer component is disposed on at least one side of the positive electrode current collector, and the buffer component is circumferentially disposed at the edge of the positive electrode active material layer; The buffer layer is disposed at the contact position between the buffer frame and the positive electrode tab, and the buffer layer is in contact with the positive electrode tab. The ratio of the length of the buffer layer in the first direction to the length of the positive electrode tab in the first direction is 52:(1~50).

2. The positive electrode sheet according to claim 1, characterized in that, The tensile strength of the buffer frame is 130MPa to 170MPa, and the elastic modulus is 2000MPa to 6000MPa.

3. The positive electrode sheet according to claim 1, characterized in that, The material of the buffer frame is selected from any one or a combination of at least two of polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyimide, or polycarbonate.

4. The positive electrode sheet according to claim 1, characterized in that, The thickness of the buffer frame satisfies the following relationship: 5μm≤D1≤(D2-9)μm, where D1 is the thickness of the buffer frame in μm and D2 is the thickness of the positive electrode active material layer in μm.

5. The positive electrode sheet according to claim 1, characterized in that, The material of the buffer layer is selected from functional materials with elastic deformation; The tensile strength of the elastically deformable functional material is 10MPa to 150MPa, and the elastic modulus is 10MPa to 1000MPa.

6. The positive electrode sheet according to claim 5, characterized in that, The elastically deformable functional material is selected from any one or a combination of at least two of thermoplastic polyurethane elastomers, polydimethylsiloxane, polyolefin elastomers, ethylene-vinyl acetate elastomers, polyurethane elastomers, polyethylene, polypropylene, or nonwoven fabrics.

7. The positive electrode sheet according to claim 1, characterized in that, The thickness of the buffer layer is 10μm to 150μm.

8. A method for preparing a positive electrode sheet as described in any one of claims 1-7, characterized in that, The method includes the following steps: By combining at least one side of the buffer border with the buffer layer, a buffer component is obtained; The positive current collector, which has a positive active material layer on at least one side, is pressed with the buffer assembly so that the inner wall of the buffer frame is in close contact with the edge of the positive active material layer, and the buffer layer is attached to the surface of the positive current collector or the positive electrode tab to obtain the positive electrode sheet.

9. The method according to claim 8, characterized in that, After the pressing process is completed, the total thickness of the buffer assembly after pressing is less than or equal to the thickness of the positive electrode active material layer.

10. An all-solid-state battery, characterized in that, The all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the positive electrode includes a positive electrode prepared by any one of claims 1-7 or any one of claims 8-9.

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