Positive plate, preparation method thereof and solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, and provides a positive plate, a preparation method thereof and a solid-state battery. The positive plate comprises a positive current collector and a positive active material layer arranged on at least one side surface of the positive current collector; the positive electrode active material layer comprises a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent and a binder; the binder comprises a first binder and a second binder; the first binder comprises polymer nanofibers, and the length-diameter ratio of the polymer nanofibers is 30-90; the mass ratio of the first binder in the positive active material layer is 0.8%-5%; the second binder includes a catechol group-containing polymer. According to the invention, the first binder and the second binder are combined for use to form a tough composite adhesion system, so that the adhesion of the positive plate is remarkably improved, and the high and low temperature performance and flexibility of the solid-state battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a positive electrode sheet, a preparation method thereof, and a solid-state battery. Background Art

[0002] With the rapid development of new energy technologies, solid-state batteries, with their advantages of high energy density and high safety, have become a core development direction for next-generation power battery technology. Among solid-state battery preparation processes, the dry process has attracted much attention due to its solvent-free, environmentally friendly, and high-areal-density coating capability. However, this process still faces significant technical bottlenecks in the cathode system.

[0003] Existing solutions often focus on optimizing a single factor, failing to fundamentally address the problem of insufficient interfacial adhesion. This severely restricts the cycle life and safety of solid-state batteries, becoming a key obstacle to their large-scale application. Therefore, there is an urgent need to develop a new technology that combines strong interfacial bonding with high adhesion stability to overcome the technical bottleneck of solid-state battery industrialization. Summary of the Invention

[0004] The insufficient adhesion of solid-state dry-process positive electrode membranes is a core technical bottleneck in the preparation process of solid-state batteries. The research of this invention found that the main reasons for the insufficient adhesion of positive electrode membranes include the following three aspects: First, the mechanical bite between the positive electrode active material, solid electrolyte and current collector is insufficient, resulting in a high risk of positive electrode membrane delamination, which greatly weakens the stability of the battery structure; second, traditional polytetrafluoroethylene adhesives mainly rely on physical winding to achieve bonding, and are prone to creep at high temperatures or long-term cycles, resulting in bonding failure; third, the alkaline substances remaining on the surface of the positive electrode material are chemically inert, which hinders the chemical bonding between the positive electrode active material and the binder and solid electrolyte, further reducing the interfacial adhesion strength.

[0005] The present invention aims to overcome the aforementioned problems of the prior art and provides a positive electrode sheet, a method for preparing the same, and a solid-state battery. The present invention utilizes a first binder and a second binder in combination to form a strong composite adhesion system, significantly enhancing the adhesion of the positive electrode sheet and thus improving the cycling performance, high- and low-temperature performance, and flexibility of the solid-state battery.

[0006] To achieve the above-mentioned object, the present invention provides a positive electrode sheet in a first aspect, 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; the positive electrode active material layer comprises a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent, and a binder; the binder comprises a first binder and a second binder; The first binder includes polymer nanofibers, and the aspect ratio of the polymer nanofibers is 30-90; the mass proportion of the first binder in the positive electrode active material layer is 0.8%-5%; The second binder includes a polymer containing catechol groups.

[0007] A second aspect of the present invention provides a method for preparing the positive electrode sheet according to the first aspect, comprising the following steps: Step S1: dry-mixing a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent, a first binder, and a second binder to obtain a mixed material; Step S2: Covering the mixed material obtained in step S1 on the surface of the positive electrode current collector, and then performing a hot pressing process; The hot pressing treatment includes a first hot pressing stage, a second hot pressing stage and a third hot pressing stage in sequence; The temperature of the first hot pressing stage is 70°C-100°C and the pressure is 8-15Mpa; The temperature of the second hot pressing stage is 110°C-140°C and the pressure is 12-20 MPa; The temperature of the third hot pressing stage is 50° C.-80° C., and the pressure is 18-25 MPa.

[0008] A third aspect of the present invention provides a solid-state battery, which includes the positive electrode sheet described in the first aspect of the present invention.

[0009] The present invention adopts the above technical solution to achieve the following beneficial effects: (1) The positive electrode sheet provided by the present invention is used in combination with a first binder and a second binder. The first binder constructs a preliminary physical adhesion framework, and the second binder and the first binder are interwoven to form a strong composite adhesion system, which significantly improves the adhesion of the positive electrode sheet.

[0010] (2) The solid-state battery provided by the present invention includes a positive electrode sheet with better adhesion, and has the advantages of good cycle performance, stable high and low temperature performance, and good flexibility.

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, unless otherwise specified, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Shown is a schematic structural diagram of a positive electrode current collector in one example.

[0013] Figure 2Shown is a schematic diagram of the internal structure of a solid-state battery in one example.

[0014] Figure 3 Shown is a schematic diagram of the external structure of a solid-state battery in an example. DETAILED DESCRIPTION

[0015] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0016] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention relates.

[0017] A first aspect of 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; the positive electrode active material layer comprises a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent, and a binder; the binder comprises a first binder and a second binder; The first binder includes polymer nanofibers, and the aspect ratio of the polymer nanofibers is 30-90; the mass proportion of the first binder in the positive electrode active material layer is 0.8%-5%; The second binder includes a polymer containing catechol groups.

[0018] In the present invention, the aspect ratio of the polymer nanofibers in the first binder is 30-90. This unique nanoscale slender structure gives it extremely strong winding and filling capabilities, and can fully penetrate and entangle the structural pores of the positive electrode active material layer, so that a mechanical interlocking structure is formed between the positive electrode active material, the solid electrolyte and the positive electrode current collector; when the diaphragm is subjected to external force, this mechanical interlocking can effectively disperse stress and prevent the positive electrode active material layer from separating from the current collector; moreover, the content of the first binder is limited to a suitable range, which can give full play to the role of the first binder and maintain the adhesion performance of the positive electrode sheet. At the same time, the second binder is a polymer containing catechol groups. The catechol groups have strong chemical activity and can react with Ni in the nickel-containing positive electrode active material. 3+ A catechol-metal coordination reaction occurs to form a stable coordination bond, thereby tightly anchoring the positive electrode active material to the surface of the positive electrode current collector, further enhancing the adhesion of the positive electrode sheet. The present invention uses a first binder and a second binder in combination. The first binder is extended and filled in the positive electrode active material to construct a preliminary physical adhesion framework; the second binder forms a chemical connection network with the nickel-containing positive electrode active material, fills the weak links in the physical structure formed by the first binder, and is interwoven with the polymer nanofibers, so that physical entanglement and chemical bonding are organically integrated to form a strong composite adhesion system, which significantly improves the adhesion of the positive electrode sheet.

[0019] In some embodiments, the aspect ratio of the polymer nanofiber is 30-90, for example, it can be 30, 40, 45, 50, 55, 60, 70, 80, 90 or any point value in the range of two points, preferably 45-55. The larger the aspect ratio of the polymer nanofiber, the longer the fiber length, the smaller the diameter, the longer the conductive path, the linear conduction is long-range conduction, and the conductivity is worse than short-range conduction. The present invention adjusts the aspect ratio of the polymer nanofiber within the above range and adjusts the mass proportion of the first binder within an appropriate range to improve the electronic conductivity of the electrode.

[0020] In some embodiments, the mass proportion of the first binder in the positive electrode active material layer is 0.8%-5%; for example, the mass proportion can be 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, or any point in a range consisting of two points. When the mass proportion of the first binder is less than 0.8%, it is difficult for the polymer nanofibers to form an effective physical entanglement network in the positive electrode active material layer, resulting in insufficient mechanical support. When the membrane is subjected to external forces or when the battery changes in volume during charge and discharge, it is easy to become loose and the active material will fall off. In addition, the formed fiber network structure is insufficient, the internal porosity of the electrode is greater, the electronic conductive path is tortuous, and the electronic conductive path is long, resulting in poor electronic conductivity of the positive electrode. When the mass proportion of the first binder exceeds 5%, the excess first binder will increase the rigidity of the diaphragm, reduce its flexibility, and make the diaphragm prone to cracks when bent or subjected to thermal stress; and the binder itself is not conductive, and excessive addition will weaken the single-electron conductivity of the positive electrode.

[0021] In some embodiments, the polymer nanofibers have a diameter of 200 nm to 400 nm, for example, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, or any value within a range consisting of two values. When the aspect ratio of the polymer nanofibers is ≥100, further adjusting the polymer nanofiber diameter to meet the above range can avoid the polymer nanofibers having an excessively small diameter (e.g., <200 nm), which can easily lead to agglomeration of the polymer nanofibers and insufficient mechanical support of individual polymer nanofibers, making it difficult to effectively embed into the pore structure of the positive electrode active material; and avoid the polymer nanofibers having an excessively large diameter (e.g., >400 nm), which can hinder the polymer nanofibers from extending and filling the positive electrode active material, making it difficult to form a stable mechanically interlocking structure.

[0022] In some embodiments, the length of the polymer nanofibers is between 10,000 nm and 20,000 nm, for example, 10,000 nm, 12,000 nm, 14,000 nm, 15,000 nm, 16,000 nm, 18,000 nm, 20,000 nm, or any value within a range consisting of two values. The present invention further limits the fiber length to a suitable range, making it less likely for the polymer nanofibers to entangle and agglomerate during the mixing process, more easily and evenly dispersed in the active material, ensuring the stability of the electrode structure and providing a more uniform contact area with the active material. This effectively avoids problems such as low electron transfer efficiency and structural instability caused by long-range conductivity of long fibers, thereby achieving synergistic optimization of the conductivity and mechanical properties of the electrode material.

[0023] In some embodiments, the polymer nanofibers include at least one of polyetheretherketone nanofibers, polytetrafluoroethylene, and polyacrylic acid fibers.

[0024] In some embodiments, the polymer nanofibers have a glass transition temperature of 140-160° C. When the glass transition temperature of the polymer nanofibers is within the above range, the polymer nanofibers have excellent high-temperature stability, are less likely to experience creep failure during high-temperature cycling, and can maintain a stable physical form, further improving the adhesion performance of the positive electrode sheet.

[0025] In some embodiments, the polymer nanofibers are polyetheretherketone nanofibers. The glass transition temperature of polyetheretherketone nanofibers is in the range of 140-160° C., which can better play the role of the first bonding and improve the adhesion performance of the positive electrode sheet.

[0026] In some embodiments, the catechol group-containing polymer includes at least one of polydopamine, polycatecholamine, tannic acid-based polymer, and polycatechol vinyl ether.

[0027] In some embodiments, the polymer containing catechol groups is polydopamine (polyDOPA). There are a large number of catechol groups, amine groups, imine groups, etc. in the polydopamine molecule. The catechol groups give polyDOPA more active chemical properties. In the positive electrode material system, for high nickel materials, the Ni on its surface 3+ It can undergo a catechol-metal coordination reaction with the catechol group of polyDOPA, forming a stable and strong coordination bond. This coordination bond tightly fixes the positive electrode active material to the current collector surface, greatly enhancing the bonding between the two, effectively preventing the positive electrode active material from falling off the current collector surface during the battery charge and discharge cycle, and ensuring the stability and integrity of the electrode structure.

[0028] In order to further optimize and improve the adhesion of the dry-process positive electrode sheet, the present invention further adjusts the content of the second binder, specifically as follows: In some embodiments, the mass proportion of the second binder in the positive electrode active material layer is 0.3%-4%; for example, the mass proportion can be 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3.0%, 3.3%, 3.5%, 3.8%, 4%, or any point value in the range of two points. If the mass proportion of the second binder is less than 0.3%, the number of catechol groups it contains is insufficient to bind to the Ni on the surface of the high nickel material. 3+ Even with sufficient coordination, it is difficult to form a sufficiently dense covalent bond network during the hot pressing process, resulting in weak interfacial bonding. When the proportion exceeds 4%, the excessive amount of second binder will make the membrane hard and brittle after cross-linking, and may hinder the transmission of lithium ions.

[0029] The present invention further controls the contents of the first binder and the second binder within the above range, which can not only enhance the adhesion of the diaphragm, but also ensure that the diaphragm has a certain flexibility, adapts to the deformation of the battery under different working conditions, and maintains the integrity of the electrode structure.

[0030] It should be noted that the mass proportion of the first binder and the second binder in the positive electrode active material layer refers to the percentage of the mass of the first binder and the mass of the second binder in the total mass of each component in the positive electrode active material layer (such as positive electrode active material, solid electrolyte, conductive agent, binder, etc.) when preparing the positive electrode sheet ingredients.

[0031] Furthermore, in some embodiments, the positive electrode active material layer further includes a silane coupling agent.

[0032] Silane coupling agent has a unique bifunctional structure, and its amino (-NH2) end can react with S in the solid electrolyte. 2- This forms a hydrogen bond network, tightly connecting the positive electrode active material layer and the solid electrolyte, effectively strengthening the interfacial bonding between the two. Furthermore, the silanol groups (-Si(OH)3) generated by the hydrolysis of the silane coupling agent can undergo a condensation reaction with hydroxyl groups on the surface of the electrode current collector or active material, forming stable Si-O-Si covalent bonds. This creates a strong chemical bridge between the active material layer and the current collector, further enhancing the stability of the overall structure. The physical entanglement of the silane coupling agent with the first binder and the chemical coordination of the second binder synergistically construct a strong composite interface from the current collector to the solid electrolyte.

[0033] In some embodiments, the mass proportion of the silane coupling agent in the positive electrode active material layer is 0.1%-1%; for example, the mass proportion can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any point value in the range consisting of two points.

[0034] In some embodiments, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane (KH-550), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602), and diethylenetriaminopropyltrimethoxysilane.

[0035] In some embodiments, the silane coupling agent is γ-aminopropyltriethoxysilane (KH-550).

[0036] When the content and type of the silane coupling agent are further limited within the above range, the silane coupling agent can achieve optimal synergy with the first binder and the second binder, enhance interfacial bonding strength, and provide a more stable basis for the physical entanglement of the first binder and the chemical bonding of the second binder; at the same time, the three work together to optimize the ion transmission channel, improve the overall performance of the positive electrode active material layer, and thereby improve the cycle performance of the solid-state battery.

[0037] Illustratively, the mass proportion of the silane coupling agent in the positive electrode active material layer refers to the percentage of the mass of the silane coupling agent in the total mass of each component in the positive electrode active material layer (such as the positive electrode active material, solid electrolyte, conductive agent, binder, etc.) when preparing the positive electrode sheet ingredients.

[0038] In order to further optimize and enhance the adhesion of the dry-process positive electrode sheet, the present invention further improves the structure of the positive electrode current collector, with the following specific adjustments: In some embodiments, a protrusion is provided on the surface of the positive electrode current collector on the side where the positive electrode active material layer is provided.

[0039] When a protrusion is provided on the surface of the current collector, the roughness of the current collector surface will increase, and the contact area between the current collector and the positive electrode active material layer will be greatly increased. The first binder and the positive electrode active material in the positive electrode active material layer can be more fully embedded in the gap of the protrusion, forming a mechanical interlocking structure to ensure the long-term stable combination of the positive electrode active material layer and the current collector, thereby improving the adhesion of the positive electrode sheet and effectively preventing the positive electrode active material layer from falling off due to volume changes during the battery charging and discharging process.

[0040] In some embodiments, the protrusions are distributed in a spaced array; the protrusions may be arranged in a uniform spaced array, or the arrangement may be adjusted according to actual needs, such as partially in a uniform spaced array and partially in a non-uniform spaced array.

[0041] In some embodiments, the diameter of the protrusion is 5 μm-10 μm; and / or the height of the protrusion is 3 μm-5 μm; and / or the distance between adjacent protrusions is 2 μm-5 μm.

[0042] The present invention further defines the diameter, height, and spacing of the protrusions within the aforementioned ranges to provide ample attachment sites for the first and second binders, while also facilitating the filling of the solid electrolyte therein. The first binder can be tightly wrapped around the protrusion structure, allowing the positive electrode active material particles to fully embed within the gaps between the protrusions, forming a continuous mechanical interlocking network. This effectively enhances the bonding strength between the positive electrode active material layer and the current collector, effectively resisting the stress generated by volume changes during battery charge and discharge, preventing the positive electrode active material layer from falling off, and improving the cycling stability and capacity retention of the solid-state battery.

[0043] In some embodiments, the protrusions are shaped like at least one of a mushroom, a gecko's foot, and an octopus's foot suction cup. The biomimetic structure of the protrusions, through their complex microscopic morphology, significantly increases the specific surface area of ​​the current collector, greatly increasing the contact area between the positive electrode active material layer and the current collector, strengthening the interfacial chemical bonding, and further improving the adhesion of the positive electrode sheet.

[0044] For example, Figure 1 As shown, protrusions 111 are dispersedly provided on one side of the positive electrode current collector 11 , and the shape of the protrusions 111 is similar to that of a gecko's foot (this figure is only a schematic diagram, and the actual height of the protrusions is less than the thickness of the current collector).

[0045] In some embodiments, a nanoporous layer is provided at the end of the protrusion distal to the positive electrode current collector. The nanoporous layer has a high specific surface area, providing abundant adsorption sites for the binder. The first binder can penetrate into the nanoporous layer, forming a mechanical interlock between the fibers and the pores, enhancing the bond strength between the binder and the positive electrode current collector and effectively preventing the loss of the positive electrode active material during battery cycling.

[0046] In some embodiments, the nanoporous layer has a pore size of 50 nm to 200 nm. The pore size of the nanoporous layer matches the size of the nanoscale binder molecules and solid electrolyte particles, and the pores in the nanoporous layer serve as stress buffers. When the electrode undergoes volume changes, the elastic deformation of the pores in the nanoporous layer absorbs stress, preventing structural damage caused by stress concentration and extending the electrode's service life.

[0047] In order to introduce the components of the positive electrode sheet in more detail and completely, the present invention further limits the selection of components such as nickel-containing positive electrode active materials and solid electrolytes, as follows: In some embodiments, the chemical formula of the nickel-containing positive electrode active material is Li a Ni x Co y Mn z O2, where 0.9≤a≤1.1, 0.7≤x<1, 0≤y≤1, 0≤z≤1.

[0048] In some embodiments, the Dv50 of the nickel-containing positive electrode active material is 4 μm-12 μm, for example, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any point value in a range consisting of two points. When the Dv50 of the nickel-containing positive electrode active material is within the above range, the nickel-containing positive electrode active material forms a good size match with the first binder, the second binder, and the silane coupling agent. The nickel-containing positive electrode active material can be fully wrapped by the binder and embedded in the micron-scale bionic protrusions and nanoporous layer of the current collector, forming a stable mechanical-chemical composite interface, effectively improving the overall bonding strength of the electrode.

[0049] In some embodiments, the solid electrolyte includes at least one of a sulfide solid electrolyte, an oxide solid electrolyte, and a polymer-based solid electrolyte.

[0050] In some embodiments, the solid electrolyte is preferably a sulfide solid electrolyte. The sulfide solid electrolyte has good compatibility with the nickel-containing positive electrode active material in terms of chemical properties. 2-It can form a hydrogen bond network with the amino group of the silane coupling agent, enhancing the adhesion of the positive electrode. At the same time, the soft properties of the sulfide electrolyte enable it to closely contact with the positive electrode active material particles, reducing interfacial gaps, lowering interfacial impedance, and improving the battery's cycle stability.

[0051] In some embodiments, the sulfide solid electrolyte includes glassy 20Li2S-80P2S5, glass-ceramic Li7P3S 11 、Crystalline Li 10 GeP2S 12 , Li6PS5Cl.

[0052] In some embodiments, the mass ratio of the nickel-containing positive electrode active material to the solid electrolyte is (3-5):1, for example, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any point in a range consisting of two points. When the mass ratio of the nickel-containing positive electrode active material to the solid electrolyte is within the above range, the positive electrode active material and the solid electrolyte form a compact and uniform composite structure, which synergizes with the biomimetic microstructure of the current collector (such as mushroom-shaped protrusions and nanoporous layers) to enhance the mechanical strength of the electrode. During the battery's charge and discharge process, the volume change of the positive electrode active material can be effectively buffered, reducing damage to the electrode structure and the shedding of the active material, thereby improving the structural stability of the battery.

[0053] The conductive agent of the positive electrode active material layer of the present invention is not particularly limited, and conventional conductive agents in solid-state batteries can be selected, such as conductive carbon black or one or more mixed conductive agents of carbon nanotubes, graphene, and carbon fibers.

[0054] The second aspect of the present invention provides a method for preparing the positive electrode sheet according to the first aspect of the present invention, comprising the following steps: Step S1: dry-mixing a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent, a first binder, and a second binder to obtain a mixed material; Step S2: Covering the mixed material obtained in step S1 on the surface of the positive electrode current collector, and then performing a hot pressing process; The hot pressing treatment includes a first hot pressing stage, a second hot pressing stage and a third hot pressing stage in sequence; The temperature of the first hot pressing stage is 70°C-100°C and the pressure is 8Mpa-15Mpa; The temperature of the second hot pressing stage is 110°C-140°C and the pressure is 12Mpa-20Mpa; The temperature of the third hot pressing stage is 50° C.-80° C., and the pressure is 18 MPa-25 MPa.

[0055] In some embodiments, in step S1, the dry mixing conditions include: using ultrasound-assisted mixing, an ultrasound frequency of 30-50 kHz, and an ultrasound time of 8-15 minutes. The ultrasound conditions can also be adjusted based on the quality of the mixed material.

[0056] In some embodiments, step S2 adopts three consecutive hot pressing treatments, and the entire dynamic hot pressing process is controlled by temperature-pressure coupling, so that the first adhesive and the second adhesive can play their respective advantages at different stages and cooperate with each other.

[0057] Illustratively, the temperature in the first hot pressing stage is 70°C-100°C (for example, it can be 70°C, 80°C, 90°C, 100°C, or any point in the range consisting of two points), and the pressure is 8 MPa-15 MPa (for example, it can be 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, or any point in the range consisting of two points).

[0058] Illustratively, the temperature in the second hot pressing stage is 110°C-140°C (for example, it can be 110°C, 120°C, 130°C, 140°C, or any point in a range consisting of two points), and the pressure is 12 MPa-20 MPa (for example, it can be 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, or any point in a range consisting of two points).

[0059] Illustratively, the temperature in the third hot pressing stage is 50°C-80°C (for example, it can be 50°C, 60°C, 70°C, 80°C, or any point in the range consisting of two points), and the pressure is 18 MPa-25 MPa (for example, it can be 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa, 25 MPa, or any point in the range consisting of two points).

[0060] There is no particular limitation on the temperature of the first hot pressing stage, the second hot pressing stage, and the third hot pressing stage, and they can be adjusted according to conditions such as the compaction density of the electrode.

[0061] During the first hot pressing stage, the glass transition of the first binder (polymer nanofibers) is activated, allowing the first binder to expand and fill pores under pressure and relatively low temperature, thereby constructing a preliminary physical adhesion framework. During the second hot pressing stage, the second binder undergoes a cross-linking reaction at higher temperature and pressure to form a covalent bond network, filling the weak links in the physical structure of the polymer nanofibers and interweaving with the polymer nanofibers, organically integrating physical entanglement and covalent bonds to form a strong composite adhesion system. The third hot pressing stage is a re-pressing process, in which high pressure is used to stabilize the previously formed microstructure morphology and chemical bonding state, avoiding excessive rebound rate of the electrode after the first two hot pressings, ensuring stable and high-strength adhesion between the positive electrode membrane and the current collector, active material, and solid electrolyte, thereby improving the overall performance and stability of the solid-state battery dry-process positive electrode sheet.

[0062] In some embodiments, before step S1, the method for preparing a positive electrode sheet further includes a step of pre-treating the positive electrode current collector: treating the positive electrode current collector with a laser process to form a protrusion on at least one surface of the positive electrode current collector on which the positive active material layer is provided.

[0063] In some embodiments, a protrusion array structure is generated on the surface of the positive electrode current collector on the side where the positive electrode active material layer is disposed by laser induction.

[0064] In some embodiments, a pulsed laser is used to form a nanoporous layer at the end of the protrusion away from the positive electrode current collector.

[0065] In some embodiments, the parameters of the laser process include: wavelength of 1000 nm-1500 nm, power of 40 W-60 W, and frequency of 80 kHz-150 kHz.

[0066] In some embodiments, prior to step S1, the nickel-containing positive electrode active material may be pretreated to remove residual alkali. Specifically, the nickel-containing positive electrode active material may be cleaned with an acidic solution to remove residual alkali on the surface. For example, the acidic solution may be a 2 wt % citric acid solution. Optionally, after cleaning the nickel-containing positive electrode active material with the acidic solution, a washing operation may be performed to prevent residual substances from forming an impurity layer on the surface of the nickel-containing positive electrode active material.

[0067] Through interdisciplinary innovation in bionics and materials chemistry, this invention overcomes the core technical bottleneck of insufficient adhesion of high-nickel solid-state dry-process positive electrode membranes, providing key process guarantees for the large-scale application of high-reliability solid-state batteries, while also having the advantages of green manufacturing and low cost.

[0068] A third aspect of the present invention provides a solid-state battery, which includes the positive electrode sheet described in the first aspect of the present invention.

[0069] Applying the positive electrode sheet provided by the present invention to a solid-state battery can improve the cycle performance, high and low temperature performance and flexibility of the solid-state battery.

[0070] For example, the internal structure diagram of the solid-state battery is as follows Figure 2 shown.

[0071] For example, the external structure diagram of the solid-state battery is as follows: Figure 3 shown.

[0072] The solid-state battery provided by the present invention can be used in high-vibration environments (such as engineering machinery, aerospace), wide-temperature range energy storage systems (such as polar / desert areas), and ultra-thin and flexible scenarios (such as foldable electronic devices).

[0073] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0074] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0075] The present invention will be described in detail below with reference to specific embodiments. These embodiments are intended to help you understand the present invention but are not intended to limit it.

[0076] Example 1a 1. Preparation of positive electrode: (1) Current collector pretreatment: After cleaning the aluminum foil (thickness 12 μm) with acetone, a femtosecond laser (wavelength 1030 nm) was used to process an array of mushroom-shaped protrusions (diameter 5-10 μm, height 3-5 μm, spacing 2-5 μm) on one side of the aluminum foil; and a pulsed laser (power 50 W, frequency 100 kHz) was used to control the formation of a nanoporous layer (pore size 100-150 nm) on the top of the protrusions. (2) Removal of residual alkali from high-nickel materials: The high-nickel material NCM9235 (Dv50 = 6 μm) was cleaned with 2 wt% citric acid solution to remove residual alkali on the surface; then washed with deionized water and dried; (3) Material compounding: The high nickel material NCM9235 after the removal of residual alkali, solid electrolyte Li6PS5Cl, PEEK fiber, polyDOPA, and KH-550 were dry-mixed in a mass ratio of 80:20:2:1:0.5, and ultrasonic assisted mixing was used with an ultrasonic frequency of 40 kHz and an ultrasonic time of 10 min. Among them, the average diameter of PEEK fiber is about 300nm, the aspect ratio is 39, and the glass transition temperature is 149℃; (4) Dynamic hot pressing: The mixed material obtained in step (3) is spread on the surface of the pretreated aluminum foil and subjected to three-stage hot pressing; the temperature of the first hot pressing stage is 80°C, the pressure is 10 MPa, and the hot pressing time is 20 s; the temperature of the second hot pressing stage is 120°C, the pressure is 15 MPa, and the hot pressing time is 30 s; the temperature of the third hot pressing stage is 60°C, the pressure is 20 MPa, and the hot pressing time is 25 s; and a dry positive electrode sheet is obtained.

[0077] 2. Preparation of negative electrode sheet: Nano-Ag powder, nano-carbon black, and PVDF binder are dispersed and slurried in a double planetary mixer in a mass ratio of 72:24:4, with NMP as the solvent. The slurry is sprayed on the surface of copper foil for sheeting, and the target specification negative electrode sheet is obtained by roller pressing and cutting.

[0078] 3. Solid electrolyte film: Solid electrolyte Li6PS5Cl powder and PTFE powder, with a mass ratio of 3:1, are dispersed and mixed evenly at high speed. After film formation and roller pressing, a solid electrolyte film with a thickness of 40μm is obtained; 4. Battery assembly After the negative electrode sheet (welded tab), solid electrolyte film, and positive electrode sheet (welded tab) are stacked in sequence, they are encapsulated with aluminum-plastic film and then compacted by isostatic pressing equipment to achieve close contact between the electrode sheet and the electrolyte film; low current formation, 0.1C constant current and constant voltage charging to 40% SOC.

[0079] Refer to Example 1a, and the main differences between the remaining examples and comparative examples are shown in Table 1. Among them, the aspect ratio of the PEEK fiber is changed mainly by shearing the PEEK fiber to change its length, thereby adjusting its aspect ratio; the mass proportion of the first binder is changed in the addition amount during the batching step (3). In Examples 1a-1e, the aspect ratio of the polymer nanofibers and the mass proportion of the first binder are both within the protection scope of the present invention. In Comparative Examples 1 and 2, the aspect ratio of the polymer nanofibers and the mass proportion of the first binder are both outside the protection scope of the present invention. In Comparative Example 3, the mass proportion of the first binder is not within the protection scope of the present invention. In Comparative Example 4, the aspect ratio of the polymer nanofibers is not within the protection scope of the present invention. In Comparative Example 5, no second binder is added.

[0080] Table 1 As can be seen from the contents of Table 1, the present invention can improve the adhesion, high and low temperature performance and flexibility of the positive electrode sheet by combining the first binder and the second binder and adjusting the aspect ratio and content of the first binder within a suitable range.

[0081] The positive electrode sheets or batteries obtained in the above examples and comparative examples were subjected to the following performance tests: (1) Adhesion of the positive electrode The test method for the adhesion of the positive electrode sheet includes: testing the peel strength between the tape sample and the stainless steel plate according to the method standard GB / T 2792-2014 "Test method for peel strength of adhesive tape".

[0082] ① Place the adhesive tape sample in an environment at 23±1°C and 50±5% RH for 24 hours. ② Wipe the surface of the stainless steel plate four times with acetone and allow to air dry for 10 minutes. ③ Remove the four layers of adhesive tape from the surface of the sample and use a cutter to cut a specimen 24 mm wide and 300 mm long from the remaining sample. ④ Fold the adhesive surface of one end of the cut specimen over to form a fold approximately 12 mm long. Attach the other end of the specimen to one end of the steel plate and roll it twice using an adhesive tape roller at 600 mm / min. ⑤ Peel approximately 25 mm of adhesive tape from the steel plate at the folded end of the specimen. Clamp the steel plate and the free end of the specimen into the upper and lower clamps of the equipment, respectively. ⑥ Set the test speed (300 mm / min) and specimen width (24 mm). Click the test option to begin the test. The equipment automatically records the force during the peeling process and reports the peel strength of the specimen accordingly. ⑦ Repeat the sample cutting, preparation, and testing procedures from (3) to (6) to test the peel strength of the three samples. If the peel strength is ≥6 N / m, the test is qualified; if the peel strength is <6 N / m, the test is unqualified.

[0083] (2) High and low temperature performance test Set the temperature of the high / low temperature chamber to 60°C / -20°C. Place the battery in the chamber for 2 hours. Set the charge and discharge process to: 0.1C constant current and constant voltage charge to 4.25V, 0.1C constant current discharge to 2.5V. Cycle three times. Ratio the charge and discharge capacity at 60°C / -20°C to the charge and discharge capacity at room temperature (25°C). Determine whether the ratio is ≥80%. If the ratio of the charge and discharge capacity at 60°C / -20°C to the charge and discharge capacity at room temperature (25°C) is ≥80%, the battery passes; if it is <80%, the battery fails.

[0084] (3) Flexibility test Cut the positive electrode sheet into 15mm long and 10mm wide, fold the electrode sheet 180°, and fold it back and forth 3 times. If the result is not light-transmitting and does not break, it passes the flexibility test (recorded as qualified), otherwise it fails (recorded as unqualified).

[0085] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A positive electrode sheet, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side surface of the positive electrode current collector; The positive electrode active material layer includes a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent and a binder; the binder includes a first binder and a second binder; The first binder includes polymer nanofibers, and the aspect ratio of the polymer nanofibers is 30-90; the mass proportion of the first binder in the positive electrode active material layer is 0.8%-5%; The second binder includes a polymer containing catechol groups.

2. The positive electrode sheet according to claim 1, characterized in that The mass proportion of the second binder in the positive electrode active material layer is 0.3%-4%.

3. The positive electrode sheet according to claim 1, characterized in that The polymer nanofiber includes at least one of polyetheretherketone nanofiber, polytetrafluoroethylene, and polyacrylic acid fiber; and / or, the aspect ratio of the polymer nanofibers is 45-55; and / or, the polymer nanofibers have a diameter of 200 nm to 400 nm; And / or, the length of the polymer nanofiber is 10000 nm-20000 nm.

4. The positive electrode sheet according to claim 1, characterized in that The glass transition temperature of the polymer nanofiber is 140-160°C; And / or, the polymer nanofiber is polyetheretherketone nanofiber.

5. The positive electrode sheet according to claim 1, characterized in that: The catechol group-containing polymer includes at least one of polydopamine, polycatecholamine, tannic acid-based polymer, and polycatechol vinyl ether.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The positive electrode active material layer further includes a silane coupling agent; The mass proportion of the silane coupling agent in the positive electrode active material layer is 0.1%-1%; The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and diethylenetriaminopropyltrimethoxysilane.

7. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: A protrusion is provided on the surface of the positive electrode current collector on the side where the positive electrode active material layer is provided.

8. The positive electrode sheet according to claim 7, characterized in that: The protrusions are distributed in an interval array; and / or, the diameter of the protrusion is 5 μm-10 μm; and / or, the height of the protrusion is 3 μm-5 μm; and / or, the distance between adjacent protrusions is 2 μm-5 μm; And / or, the shape of the protrusion includes at least one of a mushroom shape, a gecko foot shape, and an octopus foot suction cup shape.

9. The positive electrode sheet according to claim 7, characterized in that: The end of the protrusion away from the positive electrode current collector is provided with a nanoporous layer; The pore size of the nanoporous layer is 50 nm-200 nm.

10. The positive electrode sheet according to claim 1, characterized in that: The chemical formula of the nickel-containing positive electrode active material is Li a Ni x Co y Mn z O2, where 0.9≤a≤1.1, 0.7≤x<1, 0≤y≤1, 0≤z≤1; And / or, the Dv50 of the nickel-containing positive electrode active material is 4 μm-12 μm.

11. The positive electrode sheet according to claim 1, characterized in that: The solid electrolyte includes at least one of a sulfide solid electrolyte, an oxide solid electrolyte and a polymer-based solid electrolyte; The sulfide solid electrolyte includes glassy 20Li2S-80P2S5, glass ceramic Li7P3S 11 、Crystalline Li6PS5Cl、Li 10 GeP2S 12 At least one of .

12. The positive electrode sheet according to claim 1, characterized in that: The mass ratio of the nickel-containing positive electrode active material to the solid electrolyte is (3-5):

1.

13. A method for preparing the positive electrode sheet according to any one of claims 1 to 12, characterized in that: The following steps are involved: Step S1: dry-mixing a nickel-containing positive electrode active material, a solid electrolyte, a conductive agent, a first binder, and a second binder to obtain a mixed material; Step S2: Covering the mixed material obtained in step S1 on the surface of the positive electrode current collector, and then performing a hot pressing process; The hot pressing treatment includes a first hot pressing stage, a second hot pressing stage and a third hot pressing stage in sequence; The temperature of the first hot pressing stage is 70°C-100°C and the pressure is 8Mpa-15Mpa; The temperature of the second hot pressing stage is 110°C-140°C and the pressure is 12Mpa-20Mpa; The temperature of the third hot pressing stage is 50° C.-80° C., and the pressure is 18 MPa-25 MPa.

14. The method according to claim 13, characterized in that Before step S1, the method further includes a step of pre-treating the positive electrode current collector: treating the positive electrode current collector with a laser process to form a protrusion on at least the surface of the positive electrode current collector on the side where the positive electrode active material layer is provided; The parameters of the laser process include: wavelength 1000 nm-1500 nm, power 40W-60W, and frequency 80kHz-150kHz.

15. A solid-state battery, characterized in that: The positive electrode sheet comprises the positive electrode sheet according to any one of claims 1 to 12.

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