Positive plate and preparation method thereof, solid-state battery and power utilization device

Abstract

The invention relates to the technical field of batteries, in particular to a positive plate and a preparation method thereof, a solid-state battery and an electric device. The provided positive plate comprises: a positive current collector; the positive electrode active material layer is arranged on at least one side surface of the positive electrode current collector along the thickness direction; the insulation frame is arranged on the surface of at least one side of the positive electrode current collector in the thickness direction, the insulation frame is arranged on the edge of the positive electrode active material layer in the circumferential direction, and the insulation frame comprises kaolin and a binder. The solid-state battery comprises the positive plate, a negative plate and a solid-state electrolyte membrane. The problem of short circuit caused by mismatching of pole piece sizes in the isostatic pressing process of the solid-state battery can be relieved, and the short circuit risk of the battery can be reduced.

Description

Technical Field

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

[0002] Traditional lithium-ion batteries are facing more and more safety problems. Among them, the volatile, flammable and explosive organic electrolyte is the main factor causing the safety problems of lithium-ion batteries. As the next-generation lithium battery technology, solid-state batteries have outstanding advantages such as good safety and high energy density on the basis of inheriting the advantages of traditional lithium batteries.

[0003] The battery core of a solid-state battery usually consists of a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane (electrolyte layer). The solid electrolyte membrane is arranged between the positive electrode sheet and the negative electrode sheet. However, in the preparation process of a solid-state battery, such as during the large-pressure pressing process, the mismatch of the sizes of the electrode sheets easily causes the edge of the positive electrode sheet to generate a shearing force on the electrolyte layer. This shearing force may cause the edge of the positive electrode sheet to pierce the electrolyte layer and then contact the negative electrode layer, resulting in a short circuit of the battery.

[0004] In related technologies, in order to solve the above problems, an insulating ring sleeve is used to prevent short circuits between the positive and negative electrodes, for example, using polypropylene / polyamide (PP / PA) materials. However, the introduction of these insulating rings, although isolating the positive and negative electrodes to a certain extent, also brings problems of reduced energy density and reduced pressure-bearing capacity.

[0005] In view of this, the present application is specifically proposed. Summary of the Invention

[0006] In view of this, the present invention aims to at least solve one of the technical problems in the related technologies to some extent. For this purpose, the present invention provides a positive electrode sheet, a preparation method thereof, a solid-state battery, and an electrical device, which are beneficial to reducing the risk of battery short circuit.

[0007] In order to solve the above technical problems, the present application is implemented as follows:

[0008] According to one aspect of the present application, an embodiment of the present application provides a positive electrode sheet, which includes:

[0009] A positive electrode current collector;

[0010] A positive electrode active material layer, arranged on at least one surface of the positive electrode current collector along the thickness direction; and

[0011] An insulating frame, arranged on at least one surface of the positive electrode current collector along the thickness direction, and the insulating frame is circumferentially arranged at the edge of the positive electrode active material layer. The insulating frame includes kaolin and a binder.

[0012] In addition, the positive electrode sheet according to the present application may further have the following additional technical features:

[0013] In some embodiments thereof, the mass ratio of the kaolin to the binder is (50-99.9):(0.1-50).

[0014] In some embodiments thereof, the average particle size of the kaolin is 0.1 μm to 100 μm.

[0015] In some embodiments thereof, the binder includes at least one of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylic acid, polyacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol or polyurethane.

[0016] In some embodiments thereof, the binder is filled in the voids between the kaolin particles, and / or the binder coats the surfaces of the kaolin particles.

[0017] In some embodiments thereof, the positive electrode sheet satisfies at least one of the following characteristics:

[0018] (1) The thickness of the positive electrode active material layer is 30 μm to 200 μm;

[0019] (2) The thickness of the insulating frame is 30 μm to 200 μm;

[0020] (3) The thickness of the positive electrode active material layer is the same as the thickness of the insulating frame;

[0021] (4) The width of the insulating frame is 1 mm to 5 mm;

[0022] (5) The inner wall of the insulating frame is in close contact with the edge of the positive electrode active material layer.

[0023] In some embodiments thereof, the positive electrode current collector includes one or more of aluminum foil, carbon-coated aluminum foil, nickel foil, titanium foil or stainless steel.

[0024] According to another aspect of the present application, an embodiment of the present application provides a method for preparing the positive electrode sheet as described above, the method comprising:

[0025] Mix kaolin, binder and solvent evenly to obtain a mixed slurry;

[0026] Coat the mixed slurry on the surface of the positive electrode current collector by means of screen printing, dry, and form an insulating frame on the surface of the positive electrode current collector;

[0027] Place the positive electrode active material layer within the insulating frame and compound it with the positive electrode current collector to obtain the positive electrode sheet.

[0028] According to another aspect of the present application, an embodiment of the present application provides a solid-state battery, which includes a negative electrode sheet, a solid electrolyte membrane, and the positive electrode sheet as described above, or includes a positive electrode sheet prepared according to the foregoing preparation method. The solid electrolyte membrane is disposed between the positive electrode sheet and the negative electrode sheet.

[0029] In some of these embodiments, the solid-state battery satisfies at least one of the following characteristics:

[0030] (1) The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the thickness of the negative electrode active material layer is 10 μm to 150 μm;

[0031] (2) The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; the negative electrode current collector, the negative electrode active material layer, the solid electrolyte membrane, the positive electrode active material layer, and the positive electrode current collector are sequentially arranged in a first direction;

[0032] The projections of the negative electrode current collector and the negative electrode active material layer in the first direction coincide with each other; and / or, the projections of the negative electrode active material layer and the solid electrolyte membrane in the first direction coincide with each other;

[0033] (3) Along the first direction, the sum of the projected areas of the positive electrode active material layer and the insulating frame is equal to the projected area of the solid electrolyte membrane.

[0034] (4) Along the first direction, the sum of the projected areas of the positive electrode active material layer and the insulating frame is equal to the projected area of the negative electrode sheet.

[0035] According to yet another aspect of the present application, an embodiment of the present application provides an electrical device, which includes the positive electrode sheet as described above, or includes a positive electrode sheet prepared according to the foregoing preparation method, or includes the foregoing solid-state battery.

[0036] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0037] In the present application, the provided positive electrode sheet includes a positive electrode current collector and a positive electrode active layer and an insulating border disposed on the surface of the current collector. The insulating border is circumferentially disposed along the edge of the positive electrode active material layer, and the composition of the insulating border includes kaolin and a binder. Thus, by using the insulating border of kaolin material, which has soft texture, is easily dispersed and suspended in water, has good plasticity and high adhesiveness, and excellent electrical insulation performance, it can effectively play an insulating role, not only increasing the physical insulation performance of the battery cell and preventing the risk of short circuit. For example, it can effectively prevent short circuit problems caused by step problems or problems with the mismatch of the sizes of the electrode sheets. At the same time, the positive electrode insulating border based on kaolin helps to enhance the mechanical strength and extend the battery life, thereby achieving the improvement of the battery energy density and the overall optimization of the performance.

[0038] Additional aspects and advantages of the present application will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The following shows a schematic structural view of a positive electrode sheet provided by an embodiment of the present invention;

[0040] Figure 2 The following shows another schematic structural view of a positive electrode sheet provided by an embodiment of the present invention.

[0041] DESCRIPTION OF THE REFERENCE NUMERALS

[0042] 10 - Positive electrode sheet;

[0043] 110 - Positive electrode current collector;

[0044] 120 - Positive electrode active material layer;

[0045] 130 - Insulating border. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The following further elaborates the present application in combination with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and not to limit the scope of the present application.

[0047] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values or individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0048] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application mean open-ended or closed-ended. For example, the terms "comprising" and "including" may mean that other components not listed may also be included or contained, or only the listed components may be included or contained.

[0049] As mentioned in the background art, in order to alleviate the shear force generated during the pressing process under high pressure due to the size difference between the electrolyte layer and the positive and negative electrodes in the solid-state battery in the related art, which may cause the edge of the positive electrode sheet to pierce the electrolyte layer and then contact the negative electrode layer, leading to battery short-circuit problems, an insulating ring sleeve is used to prevent short-circuit between the positive and negative electrodes, such as using PP / PA materials. However, although the introduction of these insulating rings isolates the positive and negative electrodes to a certain extent, it also brings problems such as a decrease in energy density and a decrease in pressure-bearing capacity. In order to improve the energy density of the battery cell, some attempts in the related art have replaced the material of the short-circuit prevention ring with a sulfide solid electrolyte. Although this material has certain ionic conductivity, due to the gap between the insulating ring and the positive electrode sheet, the problem of lithium dendrite piercing and short-circuit still exists. Especially under high-load conditions, the traditional negative electrode wrapping positive electrode structure still faces the risk of short-circuit. In addition, if a non-isostatic pressing or confined flat pressing method, such as rolling, is used, the electrode sheet is prone to deformation, making it difficult to implement the insulating ring in the process.

[0050] In view of this, in order to alleviate the above problems, it is urgent to develop a new short-circuit prevention method to address the challenges encountered in the practical application of all-solid-state batteries. This method should not only provide physical insulation but also suppress the generation of lithium dendrites to a certain extent, thereby significantly reducing the risk of battery short-circuit. Furthermore, it helps to improve the safety and reliability of all-solid-state batteries and promotes their wide application in the new energy field. Based on the above research, the inventors of this application have fully considered the deficiencies of the existing short-circuit prevention methods and provided a positive electrode sheet, a preparation method of the positive electrode sheet, a solid-state battery including the positive electrode sheet, and an electrical device. The following is a detailed description of this application.

[0051] Please refer to Figures 1 to 2 As shown, in some embodiments, a positive electrode sheet 10 is provided, and the positive electrode sheet 10 includes:

[0052] A positive electrode current collector 110;

[0053] A positive electrode active material layer 120 disposed on at least one surface of the positive electrode current collector 110 in the thickness direction; and

[0054] An insulating frame 130 disposed on at least one surface of the positive electrode current collector 110 in the thickness direction, and the insulating frame 130 is circumferentially disposed at the edge of the positive electrode active material layer 120. The insulating frame 130 includes kaolin and a binder.

[0055] The positive electrode sheet 10 generally includes a positive electrode current collector 110 and a positive electrode active material layer 120. The positive electrode active material layer 120 is directly or indirectly coated on the positive electrode current collector 110. In this application, the positive electrode sheet 10 not only includes the positive electrode current collector 110 and the positive electrode active material layer 120, but also includes an insulating frame 130 which is circumferentially arranged along the edge of the positive electrode active material layer 120. Through the arrangement of the insulating frame 130, this application can effectively alleviate the short-circuit problem caused by the size mismatch of the electrode sheet during the isostatic pressing process of the solid-state battery.

[0056] The positive electrode current collector 110 has two surfaces in the thickness direction, such as a first surface and a second surface. The positive electrode active material layer 120 is provided on at least one surface of the positive electrode current collector 110 in the thickness direction. That is, the positive electrode active material layer 120 can be provided on both surfaces of the positive electrode current collector 110 in the thickness direction, that is, the positive electrode active material layer 120 is provided on both the first surface and the second surface; or, the positive electrode active material layer 120 can also be provided on one surface of the positive electrode current collector 110 in the thickness direction, such as on the first surface or the second surface.

[0057] As an example, this embodiment mainly describes the case where the positive electrode active material layer 120 is provided on both surfaces of the positive electrode current collector 110 in its own thickness direction, that is, the first surface and the second surface. It can be understood that in other embodiments, the positive electrode active material layer 120 can also be provided on any one of the first surface or the second surface of the positive electrode current collector 110. Further, when the positive electrode active material layer 120 is provided on both surfaces of the positive electrode current collector 110 in its own thickness direction, the insulating frame 130 is also provided on both surfaces of the positive electrode current collector 110 in its own thickness direction, and the insulating frame 130 is circumferentially arranged along the edge of the positive electrode active material layer 120. That is, the insulating frame 130 can surround the positive electrode active material layer 120.

[0058] The inventors of the present application have found through research that in a solid-state battery, due to the size mismatch of the electrode sheets or the occurrence of step problems, short-circuit problems are likely to occur. In view of this, in the present invention, an insulating border 130 is provided in the positive electrode sheet 10, and the insulating border 130 is provided at the edge of the positive electrode active material layer 120. The insulating border 130 can surround the positive electrode active material layer 120 and is connected to the edge of the positive electrode active material layer 120, thereby forming a border-like structure. The insulating border 130 can be made of kaolin and a binder. Thus, by providing the insulating border 130 made of kaolin material at the edge of the positive electrode active material layer 120, an insulating border 130 with high insulation and low Young's modulus can be formed by utilizing the softness, easy dispersion and suspension in water, good plasticity, high adhesiveness and excellent electrical insulation properties of kaolin, which can not only effectively prevent the short-circuit phenomenon caused by step problems, but also effectively prevent the cracking problem of the insulating border 130 during the operation of the battery.

[0059] When the positive electrode sheet 10 of the present invention is applied to a solid-state battery, the positive electrode sheet 10, the solid electrolyte membrane and the negative electrode sheet can be arranged in sequence. The size of the positive electrode sheet is smaller than that of the negative electrode sheet, and its orthographic projection is located within the negative electrode sheet. An insulating border 130 based on kaolin is provided around it to make up for the size difference, effectively improving the structural stability and safety of the battery. This design not only enhances the physical insulation performance of the battery and prevents the short-circuit risk. At the same time, the Young's modulus of the insulating border 130 based on kaolin is small, which helps to enhance the mechanical strength of the border and extend the battery life, thereby realizing the improvement of the battery energy density and the overall optimization of the performance, providing a new direction for the progress of solid-state battery technology.

[0060] Thus, through the setting of the insulating border 130, the present invention alleviates the size mismatch problem between the solid electrolyte membrane and the positive electrode sheet, or the step problem caused by multi-layer stacking, effectively avoids the contact short-circuit problem between the electrode sheets, reduces the short-circuit risk, improves the safety performance of the battery, and also ensures the cycle performance of the battery. Applying the positive electrode sheet of the present invention to a solid-state battery can obtain a solid-state battery with good electrochemical performance and stability at the same time.

[0061] In addition, by adopting the insulating border 130 based on kaolin, the present invention can avoid the problems of reduced energy density and decreased pressure-bearing capacity caused by the existing insulating ring sleeves using PP / PA materials, and can also avoid the problem of short-circuit caused by lithium dendrite piercing in the existing anti-short-circuit rings using sulfide solid electrolytes. It is beneficial to suppress the generation of lithium dendrites to a certain extent on the basis of providing effective physical insulation, thereby significantly reducing the risk of battery short-circuit, and further contributing to improving the safety and reliability of all-solid-state batteries.

[0062] In some embodiments, the mass ratio of kaolin to the binder is (50 to 99.9):(0.1 to 50). As an example, the mass ratio of kaolin to the binder is 50:50, 60:40, 70:30, 80:20, 90:10, 99.9:0.1, etc.

[0063] In the present application, based on the mass of the insulating frame 130, the mass proportion of kaolin can be 50% to 99.9%; the mass proportion of kaolin can be any one of the point values of 50%, 60%, 70%, 80%, 90%, 95%, 99%, 99.9% or the range value between any two of them.

[0064] In the present application, based on the mass of the insulating frame 130, the mass proportion of the binder can be 0.1% to 50%; the mass proportion of the binder can be any one of the point values of 0.1%, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50% or the range value between any two of them.

[0065] By controlling the contents of kaolin and the binder within the above suitable ranges, on the basis of ensuring the bonding performance, the electrical insulation performance of kaolin can be fully exerted, providing the insulating frame 130 with high insulation performance and low Young's modulus, effectively avoiding the problem of short circuit caused by contact between the electrode plates, and effectively preventing the cracking problem of the insulating frame 130 during the operation of the battery.

[0066] In some embodiments, the average particle size of kaolin is 0.1 μm to 100 μm. As an example, the average particle size of kaolin can be any one of the point values of 0.1 μm, 0.5 μm, 1 μm, 10 μm, 20 μm, 30 μm, 50 μm, 60 μm, 80 μm, 100 μm or the range value between any two of them.

[0067] In the present application, the average particle size can be understood as the equivalent diameter. The present application does not particularly limit the regulation method of the average particle size of kaolin, as long as the purpose of the present application can be achieved. For example, it can be achieved by directly purchasing kaolin with an average particle size within the range of the present application, or by means of crushing, grinding or ball milling.

[0068] It should also be noted that in the present application, the average particle size or particle size can be measured by any known method in the art, and there is no limitation thereto. For example, the average particle size can be measured by a Malvern high-sensitivity nano particle size analyzer.

[0069] The inventors of the present invention have found that when the particle size of kaolin in the insulating frame 130 is within the above range, it can not only effectively avoid the agglomeration of the slurry used to form the insulating frame 130, but also be beneficial to improving the air permeability of the insulating frame 130 or improving the mechanical strength of the insulating frame 130, and improving the structural stability of the positive electrode sheet.

[0070] Optionally, the purity of the above kaolin is ≥99.9%.

[0071] Thus, in the above insulating frame 130, with kaolin as the main material, the kaolin particles are fine and have strong viscosity, and have excellent electrical insulation properties. In addition, kaolin has good adsorption properties, good chemical stability, is not easily damaged by chemical reactions, and has stable physical properties and is not affected by external environments such as temperature and humidity.

[0072] In some embodiments, the binder is filled in the gaps between the kaolin particles, and / or the binder is coated on the surfaces of the kaolin particles.

[0073] In the present application, when forming the insulating frame 130 on the surface of the positive electrode current collector 110, the binder and kaolin are mixed evenly, and the binder therein can be filled in the gaps between the kaolin particles, and the kaolin can also be coated on at least part of the surfaces of the kaolin particles.

[0074] In some embodiments, in the insulating frame 130, the binder includes, but is not limited to, any one or a combination of at least two of styrene-butadiene rubber (styrene-butadiene latex, SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyacrylic acid (PAA), polyacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, or polyurethane. For the sake of brevity, the combinations within the above range will not be listed one by one.

[0075] Preferably, the binder is selected from one or more of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, and polyacrylic acid.

[0076] The preferred material of the binder in the insulating frame 130 of the present application is an aqueous binder, such as aqueous binders such as SBR, CMC, PTFE, and PAA.

[0077] For the binder used in the preparation of solid-state batteries, it is usually required to maintain the slurry viscosity unchanged for a long time, and it will not settle or fail due to the placement of the slurry; it is easy to form during rolling and will not rebound, has flexibility, and will not form fragments when the electrode breaks. Thus, by selecting aqueous binders such as SBR, CMC, PTFE, and PAA, the above requirements can be met.

[0078] In some embodiments, the thickness of the positive electrode active material layer 120 is 30 μm to 200 μm; that is, the thickness of the positive electrode active material layer 120 on one side of the positive electrode current collector 110 is 30 μm to 200 μm. As an example, the thickness of the positive electrode active material layer 120 can be any point value among 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 150 μm, 200 μm or a range value between any two of them.

[0079] In some embodiments, the thickness of the positive electrode active material layer 120 and the thickness of the insulating frame 130 can be the same. In this way, by making the thickness of the positive electrode active material layer 120 the same as the thickness of the insulating frame 130, the step problem can be avoided, which is beneficial to improving the short - circuit phenomenon caused by the step problem.

[0080] Thus, the thickness of the insulating frame 130 is the same as the thickness of the positive electrode active material layer 120, and the thickness range can be 30 μm to 200 μm.

[0081] In some embodiments, the width of the insulating frame 130 is 1 mm to 5 mm; as an example, the width of the insulating frame 130 can be any point value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm or a range value between any two of them.

[0082] If the width of the insulating frame 130 is too small, it cannot prevent the short - circuit phenomenon caused by the step problem, and the effect on reducing the short - circuit risk of the battery is not obvious; if the width of the insulating frame 130 is too large, it will occupy too much position on the positive electrode current collector or affect the arrangement of the positive electrode active material layer 120, thereby having a certain impact on the electrochemical performance of the battery.

[0083] In some embodiments, the inner wall of the insulating frame 130 is in close contact with the edge of the positive electrode active material layer.

[0084] This application does not particularly limit the positive electrode current collector 110, as long as the purpose of this application can be achieved. For example, in some embodiments, the positive electrode current collector 110 includes, but is not limited to, one or more of aluminum foil, carbon - coated aluminum foil, nickel foil, titanium foil or stainless steel.

[0085] It should be noted that the positive electrode current collector 110 includes but is not limited to the several substances listed above, and those skilled in the art can select any known positive electrode current collector 110 in the prior art according to actual needs.

[0086] Preferably, the positive electrode current collector 110 is made of carbon - coated aluminum foil.

[0087] In the present application, there is no particular limitation on the thickness of the positive electrode current collector 110, as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector 110 is 5 μm to 50 μm, preferably 6 μm to 20 μm.

[0088] In the present application, the positive electrode active material layer 120 includes a positive electrode active material, an optional conductive agent, and an optional binder. Among them, the positive electrode active material can adopt materials known in the art, and the embodiments of the present application do not limit this. As an example, the positive electrode active material can deintercalate and intercalate lithium ions. In some embodiments, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. The lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. The lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. These positive electrode active materials can be used alone or in combination of two or more.

[0089] The present application has no particular limitation on the type of the conductive agent in the positive electrode active material layer 120. In some embodiments, as an example, the conductive agent in the positive electrode active material layer 120 may include one or more of conductive carbon black (such as acetylene black, Ketjen black), conductive graphite, carbon nanotubes, graphene, or carbon fibers.

[0090] The present application has no particular limitation on the type of the binder in the positive electrode active material layer 120. In some embodiments, as an example, the binder in the positive electrode active material layer 120 may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride - tetrafluoroethylene - propylene, a terpolymer of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, a copolymer of tetrafluoroethylene - hexafluoropropylene, etc.

[0091] Optionally, the positive electrode active material layer 120 may further include an electrolyte material.

[0092] Thus, based on the above, the positive electrode sheet 10 of the kaolin-based insulating frame 130 provided by the present application has good electrochemical performance and stability. When the positive electrode sheet 10 is applied to a solid-state battery, a solid-state battery with both good electrochemical performance and stability can be obtained.

[0093] In some embodiments, the embodiments of the present application provide a method for preparing a positive electrode sheet 10, the method comprising:

[0094] Mix kaolin, a binder, and a solvent uniformly to obtain a mixed slurry;

[0095] The mixed slurry is coated on the surface of the positive current collector 110 by screen printing, dried, and an insulating frame 130 is formed on the surface of the positive current collector 110;

[0096] The positive electrode active material layer 120 is placed within the insulating frame 130 and compounded with the positive current collector 110 to obtain the positive electrode sheet 10.

[0097] It should be understood that all the features and advantages described above for the "positive electrode sheet" equally apply to the "method for preparing the positive electrode sheet", and will not be elaborated herein one by one.

[0098] In the present application, when preparing the positive electrode sheet 10, the insulating frame 130 can be first prepared on the positive current collector 110, and then the positive electrode active material layer 120 is prepared, or the pre-prepared positive electrode active material layer 120 is compounded with the positive current collector 110 to obtain the positive electrode sheet 10.

[0099] Optionally, the preparation of the insulating frame 130 may include: uniformly mixing kaolin, a binder, and a solvent to obtain a mixed slurry; then, the mixed slurry is coated on the surface of the positive current collector 110 by screen printing and dried to form the insulating frame 130. Among them, water can be used as the solvent.

[0100] Optionally, the drying temperature can be normal temperature or under heating conditions, for example, the drying temperature can be 25°C to 200°C.

[0101] It should be noted that the present application does not limit the specific preparation process of the positive electrode active material layer 120, and conventional operation methods in the art can be adopted. For example, the positive electrode active material layer 120 can be prepared by a dry film-forming method, and then the prepared positive electrode active material layer 120 is compounded with the positive current collector 110. Alternatively, the positive electrode active material layer 120 can also be formed on the positive current collector 110 by a wet method. Those skilled in the art can select and adjust according to the actual situation, and will not be elaborated herein.

[0102] In some embodiments, the present application provides a solid-state battery, which includes the aforementioned positive electrode sheet 10, or the positive electrode sheet 10 prepared by the aforementioned method.

[0103] Since the solid-state battery provided by the embodiments of the present invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated herein one by one.

[0104] In addition, the solid-state battery further includes a negative electrode sheet and a solid electrolyte membrane, and the solid electrolyte membrane is disposed between the positive electrode sheet 10 and the negative electrode sheet. As an example, the solid-state battery includes an alternately stacked negative electrode sheet, a solid electrolyte membrane, and a positive electrode sheet 10.

[0105] In the present application, the negative electrode sheet and the solid electrolyte membrane can adopt the negative electrode sheet and the solid electrolyte membrane known in the prior art applied to solid-state batteries.

[0106] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0107] In this embodiment, for the negative electrode sheet, the specific materials, structures, etc. of the negative electrode current collector and the negative electrode active material layer are not limited, and the negative electrode sheet structures and components known to those skilled in the art and applicable to solid-state batteries can be selected.

[0108] As an example, in some embodiments, the thickness of the negative electrode active material layer is 10 μm to 150 μm. As an example, the thickness of the negative electrode active material layer can be any one of the point values of 10 μm, 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 150 μm or the range value between any two of them.

[0109] Optionally, the negative electrode active material layer may include a negative electrode active material, an optional conductive agent, and an optional binder.

[0110] Optionally, the negative electrode active material layer may further include an electrolyte material.

[0111] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, in some embodiments, the negative electrode current collector includes, but is not limited to, one or more of copper foil, carbon-coated copper foil, nickel foil, titanium foil, or stainless steel.

[0112] It should be noted that the negative electrode current collector includes but is not limited to the several substances listed above, and those skilled in the art can select any negative electrode current collector known in the prior art according to actual needs.

[0113] Preferably, the negative electrode current collector is selected from carbon-coated copper foil.

[0114] In the solid-state battery of the present application, the negative current collector, the negative active material layer, the solid electrolyte membrane, the positive active material layer 120, and the positive current collector 110 are arranged in sequence along the first direction; that is, the negative active material layer in the negative electrode sheet is connected to the other surface of the solid electrolyte membrane. Among them, the first direction can be the x-axis direction.

[0115] In some embodiments, the projections of the negative current collector and the negative active material layer in the first direction coincide with each other; and / or, the projections of the negative active material layer and the solid electrolyte membrane in the first direction coincide with each other.

[0116] In some embodiments, along the first direction, the sum of the projected areas of the positive active material layer 120 and the insulating frame 130 is equal to the projected area of the solid electrolyte membrane.

[0117] In some embodiments, along the first direction, the sum of the projected areas of the positive active material layer 120 and the insulating frame 130 is equal to the projected area of the negative electrode sheet.

[0118] In the present application, in the first direction, the projection of the negative active material layer coincides with the projection of the negative current collector, and moreover, the projection of the negative active material layer coincides with the projection of the solid electrolyte membrane connected thereto. That is, the projected areas of the negative current collector, the negative active material layer, and the solid electrolyte membrane can be the same.

[0119] In the above-mentioned solid-state battery, the positive electrode sheet 10 includes a positive current collector 110, a positive active material layer 120, and an insulating frame 130 provided on at least one surface of the positive current collector 110. Among them, the positive active material layer 120 is projected on the positive current collector 110, the area of the positive active material layer 120 is smaller than the area of the positive current collector 110, and the insulating frame 130 is provided on the periphery of the positive active material layer 120. The sum of the areas of the positive active material layer 120 and the insulating frame 130 can be equal to the area of the negative active material layer, that is, the sum of the areas of the positive active material layer 120 and the insulating frame 130 can be equal to the area of the solid electrolyte membrane.

[0120] Thus, based on the above settings, for the solid-state battery provided by the present invention, its battery core includes alternately stacked negative electrode sheets, solid electrolyte membranes, and positive electrode sheets, wherein the size of the positive electrode sheet is smaller than that of the negative electrode sheet, and its orthographic projection is located within the negative electrode sheet. An insulating frame based on kaolin is provided around the positive electrode sheet to make up for the size difference, effectively improving the structural stability and safety of the battery. This design not only enhances the physical insulation performance of the battery core and prevents the risk of short circuit. At the same time, the insulating frame based on kaolin helps to enhance the mechanical strength and extend the battery life, thereby realizing the improvement of the battery energy density and the overall optimization of the performance, providing a new direction for the progress of solid-state battery technology.

[0121] In some embodiments, the present application provides an electrical device, which includes the aforementioned positive electrode sheet, or includes a positive electrode sheet prepared according to the aforementioned preparation method, or includes the aforementioned solid-state battery.

[0122] The above solid-state battery can be used as the power supply of the electrical device or as the energy storage unit of the electrical device. Therefore, the electrical device in the embodiments of the present application has better stability and higher safety.

[0123] Optionally, the electrical device can be but is not limited to being used in mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, electric bicycles, electric motorcycles, electric trucks, as well as ships, aircraft, energy storage systems, and the like.

[0124] To better understand the present invention, the specific implementation process of the present invention will be elaborated in detail in the following specific implementation manners. The implementation manners described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those without specific technologies or conditions noted in the implementation manners, the technologies or conditions described in the literature in the art or the product specifications shall be followed.

[0125] Example 1

[0126] 1. Preparation of the positive electrode sheet, including the following steps:

[0127] Mix kaolin, binder SBR and water by stirring. The mixer continuously stirs at a constant speed of 1400 rpm for 1 min to obtain a mixed slurry; wherein the mass ratio of kaolin to the binder is 99.9:0.1, and the solid content of the mixed slurry is 60%;

[0128] Use screen printing to uniformly coat the above mixed slurry on the surface of the carbon-coated aluminum foil of the positive electrode current collector, and dry it in an oven at 60°C to form an insulating border on the surface of the positive electrode current collector;

[0129] Place a positive electrode active material layer with a size of 43*56 mm inside the insulating border and laminate it with the positive electrode current collector under a pressure of 2 MPa to obtain a positive electrode sheet.

[0130] Among them, the thickness of the positive electrode active material layer is the same as that of the insulating border, and its thickness is 140 μm; the width of the insulating border is 2 mm.

[0131] 2. Preparation of the solid-state battery

[0132] (1) Provide a negative electrode sheet: Weigh the following materials in proportion. The mass ratio of silicon-carbon negative electrode: solid electrolyte: conductive agent: binder is 70:25:3:2. Disperse the materials in isobutyl isobutyrate solvent and disperse them at a speed of 1400 rmp to obtain a negative electrode slurry. Coat the negative electrode slurry on a carbon-coated copper foil and dry it to obtain a negative electrode sheet.

[0133] (2) Provide a solid electrolyte membrane: Weigh the following materials in proportion. The mass ratio of solid electrolyte: binder is 98:2. Disperse the materials in isobutyl isobutyrate solvent and disperse them at a speed of 2000 rmp to obtain an electrolyte slurry. Dry or press the electrolyte slurry to obtain a solid electrolyte membrane.

[0134] (3) Assembly of the battery: Stack the negative electrode sheet, solid electrolyte membrane and positive electrode, and press them under the condition of 300 MPa to obtain a all-solid-state battery.

[0135] Example 2

[0136] The difference between Example 2 and Example 1 is that:

[0137] In the preparation of the positive electrode sheet, the mass ratio of kaolin to binder is 99:1.

[0138] The rest are the same as those in Example 1.

[0139] Example 3

[0140] The difference between Example 3 and Example 1 is that:

[0141] In the preparation of the positive electrode sheet, the mass ratio of kaolin to binder is 98:2.

[0142] The rest are the same as those in Example 1.

[0143] Example 4

[0144] The difference between Example 4 and Example 1 is that:

[0145] In the preparation of the positive electrode sheet, the mass ratio of kaolin to binder is 95:5.

[0146] The rest are the same as those in Example 1.

[0147] Example 5

[0148] The difference between Example 5 and Example 1 is that:

[0149] In the preparation of the positive electrode sheet, the mass ratio of kaolin to binder is 90:10.

[0150] The rest are the same as those in Example 1.

[0151] Example 6

[0152] Example 6 is different from Example 1 in that:

[0153] In the preparation of the positive electrode sheet, the mass ratio of kaolin to the binder is 80:20.

[0154] The rest are the same as in Example 1.

[0155] Example 7

[0156] Example 7 is different from Example 1 in that:

[0157] In the preparation of the positive electrode sheet, the mass ratio of kaolin to the binder is 50:50.

[0158] The rest are the same as in Example 1.

[0159] Example 8

[0160] Example 8 is different from Example 1 in that:

[0161] In the preparation of the positive electrode sheet, the width of the insulating frame is 1 mm.

[0162] The rest are the same as in Example 1.

[0163] Example 9

[0164] Example 9 is different from Example 1 in that:

[0165] In the preparation of the positive electrode sheet, the width of the insulating frame is 3 mm.

[0166] The rest are the same as in Example 1.

[0167] Example 10

[0168] Example 10 is different from Example 1 in that:

[0169] In the preparation of the positive electrode sheet, the width of the insulating frame is 5 mm.

[0170] The rest are the same as in Example 1.

[0171] Comparative Example 1

[0172] Comparative Example 1 is different from Example 1 in that:

[0173] In the preparation of the positive electrode sheet, sulfide electrolyte is used to replace kaolin, and the mass ratio of sulfide electrolyte to the binder is 90:10.

[0174] The rest are the same as in Example 1.

[0175] Comparative Example 2

[0176] The difference between Comparative Example 2 and Example 1 is as follows:

[0177] In the preparation of the positive electrode sheet, boehmite is used to replace kaolin.

[0178] The rest are the same as those in Example 1.

[0179] Comparative Example 3

[0180] The difference between Comparative Example 3 and Example 1 is as follows:

[0181] In the preparation of the positive electrode sheet, alumina is used to replace kaolin.

[0182] The rest are the same as those in Example 1.

[0183] Comparative Example 4

[0184] The difference between Comparative Example 4 and Example 1 is as follows:

[0185] In the preparation of the positive electrode sheet, the insulating frame is omitted, that is, the positive electrode sheet only includes a positive electrode current collector and a positive electrode active material layer.

[0186] The rest are the same as those in Example 1.

[0187] Performance test

[0188] The solid-state batteries obtained from the above examples and comparative examples are subjected to performance tests.

[0189] (1) Capacity retention rate (cycling performance) test: At 60 °C, discharge at 0.5C to 2.6V, stand for 5 min, charge at 0.5C to 4.25V, charge at constant voltage until 0.01C and then stand for 5 minutes, activate at 0.01C for two weeks, and then perform charge and discharge cycling at 0.5C.

[0190] (2) Frame cracking condition test: Disassemble the solid-state battery and observe the state of frame cracking.

[0191] The test results are shown in Table 1.

[0192] Table 1 Performance test results of solid-state batteries of each example and comparative example

[0193]

[0194]

[0195] As can be seen from Table 1, compared with Examples 1-10 of the present invention, in Comparative Example 4, no insulating frame was provided, resulting in a direct short circuit. This shows that the absence of the insulating frame material easily leads to short circuits, which poses a huge challenge to battery manufacturing. Further, in the cell structure with an insulating frame, different frame materials also have a certain impact on the performance of the battery. In the present invention, if the content of the binder is too high, the frame may be prone to deformation, and if the content of the binder is too low, the frame material may be prone to cracking. Therefore, the mass ratio of kaolin to the binder in the present invention is (50-99.9):(0.1-50); as a preferred embodiment of the present invention, based on the total mass of the insulating frame, the content of the binder can be 5-20 wt%. In addition, if the frame width of the insulating frame is too large, the energy density may be reduced, and if the frame width of the insulating frame is too small, the cell may be short-circuited. Therefore, the frame width of the insulating frame can be 1 mm to 5 mm, preferably 1.5 mm to 3 mm.

[0196] The parts not detailed in the present invention are well-known technologies to those skilled in the art.

[0197] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, advantages, effects, etc. mentioned in the present invention are only examples and not limitations. It cannot be considered that these advantages, advantages, effects, etc. are essential for each embodiment of the present invention. In addition, the above-disclosed specific details are only for the purposes of illustration and easy understanding, and not for limitation. The above details do not limit the present invention to necessarily adopt the above specific details to implement.

[0198] It should be noted that the term "and / or" or " / " used herein is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0199] In the specific embodiments and claims, a list of items connected by the terms "at least one of", "at least a", "at least one kind of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the present invention in each embodiment.

Claims

1. A positive electrode sheet, characterized in that: The positive electrode sheet comprises: Positive electrode current collector; A positive electrode active material layer is disposed on at least one side of the positive electrode current collector along the thickness direction; and An insulating frame is arranged on at least one side surface of the positive electrode current collector along the thickness direction, and the insulating frame is circumferentially arranged at the edge of the positive electrode active material layer, and the insulating frame includes kaolin and a binder.

2. The positive electrode sheet according to claim 1, characterized in that: The mass ratio of the kaolin to the binder is (50-99.9):(0.1-50).

3. The positive electrode sheet according to claim 1, characterized in that: The average particle size of the kaolin is 0.1 μm to 100 μm.

4. The positive electrode sheet according to claim 1, characterized in that: The binder comprises at least one of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylic acid, polyacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol or polyurethane; and / or, The binder fills the gaps between the kaolin particles, and / or the binder is coated on the surface of the kaolin particles.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The positive electrode sheet satisfies at least one of the following characteristics: (1) The thickness of the positive electrode active material layer is 30 μm to 200 μm; (2) The thickness of the insulating frame is 30 μm to 200 μm; (3) The thickness of the positive electrode active material layer is the same as the thickness of the insulating frame; (4) The width of the insulating frame is 1 mm to 5 mm; (5) The inner wall of the insulating frame is in close contact with the edge of the positive electrode active material layer.

6. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The positive electrode current collector includes one or more of aluminum foil, carbon-coated aluminum foil, nickel foil, titanium foil or stainless steel.

7. The method for preparing a positive electrode sheet according to any one of claims 1 to 6, characterized in that: The method comprises: Mixing kaolin, a binder and a solvent uniformly to obtain a mixed slurry; The mixed slurry is coated on the surface of the positive electrode current collector by screen printing, and dried to form an insulating frame on the surface of the positive electrode current collector; The positive electrode active material layer is placed in the insulating frame and combined with the positive electrode current collector to obtain the positive electrode sheet.

8. A solid-state battery, characterized in that: The solid-state battery comprises a negative electrode sheet, a solid electrolyte membrane, and a positive electrode sheet as described in any one of claims 1 to 6, or comprises a positive electrode sheet prepared by the preparation method according to claim 7, and the solid electrolyte membrane is arranged between the positive electrode sheet and the negative electrode sheet.

9. The solid-state battery according to claim 8, characterized in that: The solid-state battery meets at least one of the following characteristics: (1) The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector; the thickness of the negative electrode active material layer is 10 μm to 150 μm; (2) The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector; the negative electrode current collector, the negative electrode active material layer, the solid electrolyte membrane, the positive electrode active material layer and the positive electrode current collector are disposed in sequence along a first direction; The projections of the negative electrode current collector and the negative electrode active material layer in the first direction overlap with each other; and / or the projections of the negative electrode active material layer and the solid electrolyte membrane in the first direction overlap with each other; (3) Along the first direction, the sum of the projected area of ​​the positive electrode active material layer and the projected area of ​​the insulating frame is equal to the projected area of ​​the solid electrolyte membrane; (4) Along the first direction, the sum of the projected area of ​​the positive electrode active material layer and the projected area of ​​the insulating frame is equal to the projected area of ​​the negative electrode sheet.

10. An electrical device, characterized in that: The electrical device comprises the positive electrode sheet as described in any one of claims 1 to 6, or comprises the positive electrode sheet prepared according to the preparation method according to claim 7, or comprises the solid-state battery as described in any one of claims 8 to 9.

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