Secondary battery and preparation method therefor

Abstract

Provided in the present application are a secondary battery and a preparation method therefor. The secondary battery comprises a first electrode sheet, a second electrode sheet, and an insulating support part, wherein the first electrode sheet and the second electrode sheet are alternately stacked in a first direction to form a stack; the first electrode sheet is provided with extension parts extending outwards compared with the second electrode sheet, gap parts being formed between adjacent extension parts in the first direction; and the insulating support part comprises filling parts and covering parts, the filling parts filling the gap parts, and the covering parts covering the ends of the extension parts. The secondary battery of the present application ensures high safety.

Description

Secondary battery and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on the Chinese patent application with application number 202311032817.2 and application date of August 16, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a secondary battery and a preparation method thereof. Background Art

[0004] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. Despite significant development, current secondary batteries still pose safety risks.

[0005] Therefore, how to improve the safety performance of secondary batteries has become an urgent problem to be solved in this field.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its object is to provide a secondary battery with high safety and a method for manufacturing the same.

[0008] A first aspect of the present application provides a secondary battery, characterized in that it includes a first pole piece, a second pole piece and an insulating support portion, the first pole piece and the second pole piece are alternately stacked along a first direction to form a stack, the first pole piece has an extension portion extending outward compared to the second pole piece, and a gap portion is formed between the adjacent extension portions in the first direction, the insulating support portion includes a filling portion and a covering portion, the filling portion fills the gap portion, and the covering portion covers the end portion of the extension portion.

[0009] Therefore, the present application greatly strengthens the structural stability by providing insulating support portions in the protruding portions and gap portions in the electrode stack, thereby improving the safety of the battery.

[0010] In any embodiment, the filling portion is connected to the covering portion and fills the gap. Optionally, the filling portion fills the gap to the end of the second pole piece located in the gap. By making the filling portion fully fill the gap, the structure is made more stable and the battery safety is improved.

[0011] In any embodiment, the height of the filling portion in the first direction is equal to the height of the gap in the first direction. By making the filling portion fully fill the gap, the structure is made more stable and the battery safety is improved.

[0012] In any embodiment, the covering portion and the filling portion are integrally formed, thereby making the insulating support body securely arranged on the protruding portion and the gap portion as a whole, thereby enhancing structural stability and improving battery safety.

[0013] In any embodiment, the covering portion covers the entire stack along the first direction. Thus, the insulating support body itself has a stronger pressure resistance, which enhances the stability of the battery stack structure and improves battery safety.

[0014] In any embodiment, an insulating support portion is formed outside the stack and around the entire circumference of the stack, thereby further improving the structural stability of the entire battery stack.

[0015] In any embodiment, the secondary battery includes N+1 layers of the first electrode sheet and N layers of the second electrode sheet (N≥1), and a solid electrolyte membrane is arranged between the first electrode sheet and the second electrode sheet adjacent to each other stacked in a first direction. The first electrode sheet is a negative electrode sheet, and the second electrode sheet is a positive electrode sheet.

[0016] By providing an insulating support portion in a solid-state battery stack, the safety of the solid-state battery is improved.

[0017] In any embodiment, the laminate having the insulating support portion is subjected to a compression treatment, wherein the compression treatment comprises applying pressure to each surface of the laminate having the insulating support portion at a pressure greater than 0 MPa and less than or equal to 1000 MPa, and optionally at a pressure between 50 MPa and 1000 MPa. Optionally, the laminate having the insulating support portion is subjected to an isostatic pressing treatment. This allows the solid-state battery to have both excellent safety and high volumetric energy density.

[0018] In any embodiment, the insulating support portion is made of a polymer, and optionally, the polymer has a glass transition temperature of -30°C to 200°C. The polymer has insulating and curable properties, and by controlling the conditions, it can easily fill the gap and cover the end of the extension, achieving both insulation and structural support.

[0019] A second aspect of the present application further provides a method for preparing a secondary battery, comprising the following steps:

[0020] a stacking step of alternately stacking a first pole piece and a second pole piece along a first direction to form a stacked body, wherein the first pole piece is formed with an extension portion extending outwardly compared to the second pole piece, and a gap portion is formed between adjacent extension portions in the first direction; and

[0021] Filling step: filling the gap and the end of the protruding portion with a slurry containing a high molecular polymer to form an insulating support portion.

[0022] By using the above preparation method, a secondary battery with strong structural stability and high safety can be obtained.

[0023] In any embodiment, prior to the lamination step, a negative electrode film layer is formed on at least one surface of the negative electrode current collector to form the first electrode sheet, a positive electrode film layer is formed on at least one surface of the positive electrode current collector to form the second electrode sheet, and a solid electrolyte is coated on the surface of the first electrode sheet or the second electrode sheet to form a solid electrolyte membrane. This can provide a solid-state battery with strong structural stability and high safety.

[0024] In any embodiment, in the filling step, the slurry is filled by dipping, coating, or injecting. The insulating support portion can be formed by the above filling method.

[0025] In any embodiment, after the filling step, a compression step is further included: pressing each surface of the laminate having the insulating support portion formed thereon at a pressure greater than 0 MPa and less than or equal to 1000 MPa, optionally at a pressure between 50 MPa and 1000 MPa. Optionally, the laminate having the insulating support portion formed thereon is subjected to isostatic pressing. This step can significantly improve the volumetric energy density of the prepared solid-state battery while maintaining excellent safety.

[0026] A third aspect of the present application provides an electrical device, characterized in that it includes the above-mentioned secondary battery, or a secondary battery obtained by the above-mentioned preparation method.

[0027] Effects of the Invention

[0028] According to the present application, a secondary battery with high structural stability and excellent safety can be provided. Furthermore, according to the present invention, a solid-state battery with high safety and high volume energy density can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a partial schematic cross-sectional view of a secondary battery according to one embodiment of the present application.

[0030] FIG2 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present application.

[0031] FIG3 is a schematic cross-sectional view of a secondary battery according to an embodiment of the present application.

[0032] FIG4 is a CT image of the solid-state battery of Example 1 of the present application.

[0033] FIG5 is a disassembled photo of the solid-state battery of Comparative Example 1 of the present application.

[0034] Description of reference numerals:

[0035] 1 first pole piece; 11 extension portion; 111 end portion of the extension portion; 2 second pole piece; 3 insulating support portion; 31 filling portion; 32 covering portion; 1' negative electrode; 1'a negative electrode current collector; 1'b negative electrode film layer; 2' positive electrode; 2'a positive electrode current collector; 2'b positive electrode film layer; 3' insulating support portion. DETAILED DESCRIPTION

[0036] Below, the embodiments of the secondary battery and the method for preparing the same of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0039] At present, existing secondary batteries have a multi-layer electrode stacking structure formed by alternating stacking of first electrode sheets and second electrode sheets, and overhang portions are formed at the ends of adjacent first electrode sheets in a direction perpendicular to the stacking direction (that is, the first electrode sheet extends outward relative to the second electrode sheet adjacent to it in the stacking direction, thereby forming a gap between adjacent protruding portions). This causes the protruding electrode sheets to be squeezed and broken when the secondary battery is subjected to external forces such as impact or external pressure, exposing the internal metal and causing an internal short circuit, greatly reducing the safety of the battery and even causing battery failure. In particular, this phenomenon often occurs during the battery preparation process, which also makes the battery manufacturability poor.

[0040] In view of the above situation, the first aspect of the present application provides a secondary battery, as shown in Figure 1, the secondary battery includes a first pole piece 1, a second pole piece 2 and an insulating support portion 3, the above-mentioned first pole piece 1 and the above-mentioned second pole piece 2 are alternately stacked along a first direction, the above-mentioned first pole piece 1 has an extension portion 11 extending outward compared to the second pole piece 2, and a gap portion is formed between the above-mentioned extension portions 11 adjacent to each other in the first direction, the above-mentioned insulating support portion 3 includes a filling portion 31 and a covering portion 32, the above-mentioned filling portion 31 fills the above-mentioned gap portion, and the above-mentioned covering portion 32 covers the end portion 111 of the above-mentioned extension portion.

[0041] Here, the so-called "first direction" refers to the stacking direction of the pole pieces, and the so-called "outer side" refers to the outer side relative to the middle of the pole piece.

[0042] The length of the protruding portion 11 (ie, the length of the first pole piece 1 protruding outward compared to the second pole piece 2 ) is less than 100 mm, and can be optionally 0.5 mm to 10 mm, or optionally 1 mm to 6 mm.

[0043] In the above-mentioned secondary battery, an insulating support portion 3 is provided on the overhang portion (the above-mentioned protruding portion and the gap portion), thereby filling the gap portion and playing a role in structural reinforcement of the protruding portion 11 of the electrode, thereby preventing the protruding portion 11 of the electrode from being conductive due to breaking (for example, when the first electrode 1 is the negative electrode, the electrode breaks and the copper is exposed). At the same time, the end portion 111 of the protruding portion is covered, thereby preventing the end portion 111 from exposing metal and causing a short circuit. The structural stability is improved, and the safety of the battery is excellent.

[0044] In some embodiments, the filling portion 31 is connected to the covering portion 32 and fills the gap. Optionally, the filling portion 31 fills the gap to the end of the second pole piece 2 located in the gap. The length of the filling portion 31 in the second direction is equal to the length of the protruding portion 11. Here, the so-called "second direction" refers to a direction perpendicular to the first direction. In some embodiments, the height of the filling portion 31 in the first direction is equal to the height of the gap in the first direction. As a result, the filling portion 31 fully fills the gap, further reducing the risk of the protruding portion breaking due to the presence of the gap, making the structure more stable, and improving battery safety.

[0045] In some embodiments, the covering portion 32 is integrally formed with the filling portion 31 , so that the insulating support 3 is firmly disposed on the protruding portion 11 and the gap portion as a whole, thereby enhancing structural stability and improving battery safety.

[0046] In some embodiments, the covering portion 32 covers the entire stack along the first direction. Optionally, the height of the covering portion 32 in the first direction is equal to the stack thickness of the stack in the first direction. Optionally, the length of the covering portion 32 in the second direction is greater than 0 mm and less than or equal to 10 mm, and optionally is 0.5 mm to 6 mm. This enhances the pressure resistance of the insulating support body and improves the stability of the battery stack structure.

[0047] In some embodiments, an insulating support portion is formed on the outside of the stack and around its entire circumference. For example, the pole pieces that make up the stack can be quadrilateral, circular, or the like. Insulating support portions can be formed on all four sides of a rectangular stack or on the entire circumference of a cylindrical stack. In other words, insulating support portions can be formed on all sides of the stack except for the top and bottom surfaces in the stacking direction. This further improves the overall structural stability of the battery stack.

[0048] In some embodiments, as long as the material forming the above-mentioned insulating support portion (covering portion + filling portion) is insulating and can play a structural supporting role, a material that can be cured under certain conditions can be used. For example, a material including a polymer can be used. Preferably, the glass transition temperature of the above-mentioned polymer is -30°C to 200°C, and more preferably 80°C to 120°C. As the polymer, for example, polyolefins such as polypropylene and polyethylene, polystyrene (PS), ethylene acetate-ethylene copolymer, epoxy resin, silicone rubber, and polyurethane, polyacrylic acid, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT) resin, epoxy resin, etc. can be used. One or more mixtures can be used. As the slurry containing the polymer, hot melt adhesive, Kraft AB adhesive, glass prepreg, etc. are preferably used.

[0049] When hot melt adhesive is used, the insulating support portion is a structure formed by curing the hot melt adhesive. It has a certain viscosity and hardness, which can fill the gap and cover the end of the extension. At the same time, the hot melt adhesive also has a certain hardness, which can enhance the structural strength and improve the bending resistance. The hot melt adhesive used in this application can be a conventional hot melt adhesive, such as polyethylene hot melt adhesive, polypropylene hot melt adhesive, ethylene and its copolymer hot melt adhesive, polyester hot melt adhesive, polyamide hot melt adhesive, and of course, a specially configured hot melt adhesive can also be used, which is not limited in the embodiments of this application.

[0050] In addition, for existing solid-state batteries, during the preparation process, it is difficult for the solid electrolyte to fit tightly with the pole piece under conventional pressure (1-40Mpa) during hot pressing, and its compactness cannot be achieved, resulting in a large overall resistance and low energy density of the battery. In order to improve the energy density, it is necessary to perform six-sided pressurization at a pressure greater than 0Mpa and less than or equal to 1000Mpa, especially at a pressure of 50-1000Mpa, after hot pressing. However, due to the presence of an overhang portion in the battery, the structural stability is poor, resulting in the negative electrode protruding outward compared to the positive electrode during the six-sided pressurization process, especially when hot pressing the side of the stack (except the upper and lower surfaces in the stacking direction), which is easy to break and expose copper, causing the battery cell to short-circuit, making it difficult to prepare into a battery, and the battery manufacturability is poor.

[0051] In view of this, in some embodiments, according to the stacking method of first electrode sheet (negative electrode sheet) / solid electrolyte membrane / second electrode sheet (positive electrode sheet) / solid electrolyte membrane / first electrode sheet / solid electrolyte membrane...first electrode sheet (negative electrode sheet), a solid electrolyte membrane is arranged between the adjacent first electrode sheets (negative electrode sheets) and the second electrode sheets (positive electrode sheets) stacked in the first direction, thereby forming a stacked body, which includes N+1 layers of negative electrode sheets and N layers of positive electrode sheets, where N≥1.

[0052] The solid-state battery of the present application is provided with an insulating support part, which effectively solves the problem of the negative electrode extension part breaking and exposing copper, improves the stability of the battery structure, avoids the risk of internal short circuit of the battery, improves the battery safety, and improves the battery manufacturability, which has a huge promoting effect on the mass production of solid-state batteries.

[0053] In some embodiments, the above-mentioned stack formed with the insulating support portion of the solid-state battery is subjected to a compression treatment, and the compression treatment is: pressurizing each surface of the stack formed with the insulating support portion under a pressure greater than 0 MPa and less than or equal to 1000 MPa, optionally under a pressure of 50 MPa to 1000 MPa, and optionally, performing isostatic pressing on the stack formed with the insulating support portion.

[0054] The solid-state battery provided with an insulating support portion has a strong structural stability, and even after the above-mentioned compression treatment, the negative electrode extension will not break and expose the copper. Therefore, while the solid-state battery has excellent battery safety, the volume of the battery is reduced after the above-mentioned compression treatment, so that the volume energy density of the battery can be greatly improved.

[0055] The positive electrode sheet may include a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector and including a positive electrode active material. The type of the positive electrode active material is not specifically limited and may be selected according to actual needs.

[0056] Alternatively, the positive electrode active material may be selected from LiFe x1 Mn y1 M z1 PO4 (0≤x1≤1, 0≤y1≤1, 0≤z1≤1, x1+y1+z1=1, M is selected from one or more of Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo), Li3V2(PO4)3, Li3V3(PO4)3, LiVPO4F, LiNi 0.5-x2 Mn 1.5- y2 M′ x2+y2 O4 (-0.1≤x2≤0.5, 0≤y2≤1.5, M′ is selected from one or more of Mn, Co, Fe, Al, Mg, Ca, Ti, Mo, Cr, Cu, Zn), Li1+x2Ni 1－y2－z2 Co y2 M″ z2 O2 (M″ is selected from one or more of Mn, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, -0.1≤x2≤0.2, 0≤y2≤1, 0≤z2≤1, 0≤y2+z2≤1) one or more. Further preferably, the above-mentioned positive electrode active material is selected from LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V3(PO4)3, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCoO2, LiNiO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2、LiNi 0.8 Co 0.1 Al 0.1 O2、LiNi 0.8 Co 0.1 Mn 0.1 When the positive electrode active material is the lithium salt positive electrode active material, the corresponding negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, silicon carbon, metallic lithium, and lithium alloy.

[0057] Optionally, the positive electrode active material may be selected from one or more of V2O5, MnO2, TiS2, FeS2, SnS2, and CuS2. When the positive electrode active material is a non-lithium salt positive electrode active material, the corresponding negative electrode active material should be a negative electrode active material that can release lithium ions, such as metallic lithium or a lithium alloy.

[0058] The positive electrode film layer may further include a conductive agent and a binder. There is no specific limitation on the types of the conductive agent and the binder, and they may be selected according to actual needs.

[0059] The negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector and including a negative electrode active material. The type of the negative electrode active material is not specifically limited and may be selected according to actual needs. For example, the negative electrode active material may be a Si-based material, a silicon-carbon material, a mixture of carbon and alloy elements, lithium metal, lithium alloy, graphite, hard carbon, etc.

[0060] The negative electrode film layer may further include a conductive agent and a binder. There is no specific limitation on the types of the conductive agent and the binder, and they may be selected according to actual needs.

[0061] The solid electrolyte in the solid electrolyte membrane can be any solid electrolyte commonly used in solid-state batteries. There is no particular limitation on the type of the solid electrolyte, and the type can be selected based on actual needs. For example, the sulfide solid electrolyte described in CN111864256B can be used.

[0062] A second aspect of the present application provides a method for preparing a secondary battery, comprising the following steps:

[0063] Laminating step: alternately laminating the first pole piece and the second pole piece along a first direction to form a laminate, wherein the first pole piece is formed with an extension portion extending outward compared to the second pole piece, and a gap portion is formed between the adjacent extension portions in the first direction; and

[0064] Filling step: filling the gap and the end of the protruding portion with a slurry containing a high molecular polymer to form an insulating support portion.

[0065] Through the above preparation method, the problem of the negative electrode extension breaking and exposing copper is effectively solved, the stability of the battery structure is improved, the risk of internal short circuit of the battery is avoided, and the battery safety is improved. At the same time, the battery preparability is improved, which has a huge promoting effect on the mass production of solid-state batteries.

[0066] In one embodiment, prior to the lamination step, a negative electrode film layer is formed on at least one surface of the negative electrode current collector to form the first electrode sheet, a positive electrode film layer is formed on at least one surface of the positive electrode current collector to form the second electrode sheet, and a solid electrolyte is coated on the surface of the first or second electrode sheet to form a solid electrolyte membrane. This results in a solid-state battery with a strong structural stability and high safety.

[0067] In one embodiment, in the filling step, there is no specific limitation on the filling method, as long as the slurry can be filled into the gap. For example, dipping, coating, or injection can be used. As an injection method, for example, a method of high-pressure glue injection can be used after sealing the side of the secondary battery, thereby protecting the battery cell and preventing exposed copper at the negative electrode from overlapping the positive electrode. Alternatively, a method of injecting glue into the entire hard-shell battery cell can be used, thereby solving the problem of hard-shell solid-state battery damage.

[0068] In one embodiment, after the filling step, a compression step is further included: at a pressure greater than 0 MPa and less than or equal to 1000 MPa, optionally at a pressure of 50 MPa to 1000 MPa, each surface of the laminate having the insulating support portion is pressurized, optionally, the laminate having the insulating support portion is subjected to isostatic pressing, optionally, the laminate having the insulating support portion is subjected to warm isostatic pressing. There is no particular limitation on the pressure, temperature, and time of warm isostatic pressing, for example, it is greater than 100 MPa and less than 2000 MPa, greater than 10°C and less than 2000°C, and greater than 5 seconds and less than 6000 seconds. Through this step, the volume of the battery is reduced, and the volume energy density of the prepared solid-state battery can be greatly improved.

[0069] The following is a detailed description of the method for preparing the secondary battery of the present application. The method comprises the following steps:

[0070] Electrode preparation

[0071] In an environment with an ambient humidity of 0.03% to 0.05% and an ambient temperature of -60°C to -55°C, the above-mentioned negative electrode active materials (e.g., silicon-based materials, MC materials (alloy / C materials), etc.), additives, conductive agents, binders, and any other components are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on both surfaces of the negative electrode current collector to form a negative electrode film layer, and after drying, cold pressing, and other processes, a negative electrode sheet is obtained. A solid electrolyte (e.g., a sulfide solid electrolyte) is coated on the entire surface of the negative electrode film layer of the negative electrode sheet to form a solid electrolyte membrane. In addition, the above-mentioned positive electrode active materials, conductive agents, binders, lithium supplements, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on both surfaces of the positive electrode current collector to form a positive electrode film layer, and after drying, cold pressing, and other processes, a positive electrode sheet is obtained.

[0072] Cascade

[0073] In an environment with an ambient humidity of 0.03% to 0.05% and a temperature of -60°C to -55°C, the negative electrode sheets with the solid electrolyte membranes formed thereon and the positive electrode sheets are alternately stacked in a first direction to form a stack of negative electrode sheets / solid electrolyte membranes / positive electrode sheets. The negative electrodes extend outward relative to the positive electrodes by a distance greater than 2 mm, and gaps are formed between adjacent negative electrodes in the stacking direction.

[0074] In addition, the above-mentioned solid electrolyte (for example, a sulfide solid electrolyte) can also be coated on the entire surface of the positive electrode film layer of the positive electrode sheet to form a solid electrolyte membrane. Thereafter, the positive electrode sheet formed with the solid electrolyte membrane and the above-mentioned negative electrode sheet are alternately stacked along the first direction to form the above-mentioned stacked body.

[0075] Hot Pressing

[0076] Next, hot pressing is performed at a humidity of 0.03% to 0.05% and a temperature of -60°C to -55°C, with parameters of 6 MPa to 8 MPa, 85°C to 95°C, and 20 to 130 seconds. This ensures that the solid-state battery maintains a relatively stable structure and avoids pole piece dislocation caused by looseness.

[0077] filling

[0078] Next, in an environment with an ambient humidity of 0.03% to 0.05% and -60degc to -55degc, place it in a glue injection mold, the single side of which is 1mm to 10mm larger than the outer contour of the battery cell. After sealing, inject hot melt adhesive (containing polyolefin, such as polypropylene or a mixture of polypropylene and other polymers) with an injection pressure of 0.3Mpa to 0.6Mpa, a temperature of 150°C to 200°C, and a holding time of 5s to 30s. Then, cool water is passed into the water channel inside the glue injection mechanism for 10s to 30s to allow the hot melt adhesive to cool and harden rapidly, thereby filling the gap and covering the end of the negative electrode extension to form an insulating support portion. Figures 2 and 3 are schematic cross-sectional views thereof.

[0079] Specifically, Figure 2 is a schematic cross-sectional view along the width of the electrode sheet, and Figure 3 is a schematic cross-sectional view along the length of the electrode sheet. As shown in Figures 2 and 3, a negative electrode film layer 1'b is formed on the surface of the negative electrode current collector 1'a, a solid electrolyte membrane (not shown) is formed on the surface of the negative electrode film layer 1'b, and a positive electrode film layer 2'b is formed on the surface of the positive electrode current collector 2'a. The negative electrode sheets 1' and the positive electrode sheets 2' are alternately stacked. An insulating support portion 3' is formed on the outside of the stack and around the entire circumference of the stack (i.e., on both sides in the horizontal direction in the cross-sectional views of Figures 2 and 3), filling the gaps between adjacent negative electrode sheets 1' and covering their ends. In Figure 3, there is an empty foil area on the negative electrode current collector 1'a where the negative electrode film layer 1'b is not formed. The portion of the empty foil area close to the negative electrode film layer 1'b is covered by the insulating support portion 3', and the portion away from the negative electrode film layer 1'b constitutes the negative electrode tab. Similarly, there is an empty foil area on the positive electrode current collector 2'a where the positive electrode film layer 2'b is not formed. The portion of the empty foil area close to the positive electrode film layer 2'b is covered by the insulating support portion 3', and the portion away from the positive electrode film layer 2'b constitutes the positive electrode tab, and the positive electrode tab and the negative electrode tab are located on the same side of the stack.

[0080] Encapsulation

[0081] The aluminum-plastic film is packaged in an environment with an ambient humidity of 0.03% to 0.05% and a temperature of -60°C to -55°C, and then negative pressure is drawn to seal the solid-state battery to ensure that the solid-state battery is isolated from the environment.

[0082] compression

[0083] Warm isostatic pressing is performed in an atmospheric environment, wherein the warm isostatic pressing parameters are a pressure of 100 MPa or more and 2000 MPa or less and 600 MPa or less, a temperature of 10°C or more and 2000°C or less, and a time of 5 seconds or more and 6000 seconds or less. A solid-state battery is obtained by applying pressure on six sides.

[0084] In addition, the third aspect of the present application provides an electric device, which includes the secondary battery of the present application or the secondary battery obtained by the preparation method of the present application. The secondary battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0085] Example

[0086] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0087] Example 1

[0088] (1) Electrode

[0089] Under an ambient humidity of 0.04% and a temperature of -60°C, a negative electrode slurry (the negative electrode active material is Si compound) is applied to the negative electrode current collector (copper) to form a negative electrode film layer. After drying and cold pressing, a negative electrode sheet is formed. Then, a solid electrolyte (sulfide) is gravure-coated on the negative electrode film layer of the negative electrode sheet to form a solid electrolyte membrane. Separately, a positive electrode slurry (the positive electrode active material is a high-nickel ternary material) is applied to the positive electrode current collector (aluminum foil) to form a positive electrode film layer. After drying and cold pressing, a positive electrode sheet is formed.

[0090] (2) Stacking

[0091] In an environment with an ambient humidity of 0.04% and -60 degrees Celsius, the negative electrode sheet / positive electrode sheet / negative electrode sheet / positive electrode sheet / negative electrode sheet (each electrode sheet is a quadrilateral) is alternately stacked by a stacking machine. After stacking, the length of the protruding part of the negative electrode sheet extending outward is greater than 2 mm compared with the positive electrode sheet.

[0092] The obtained stack is configured from bottom to top in sequence: a negative electrode film layer (the active material is Si compound), a portion of the negative electrode current collector, a negative electrode film layer (the active material is Si compound), a solid electrolyte layer (sulfide), a positive electrode film layer (the active material is a high-nickel ternary material), a portion of the positive electrode current collector, and a positive electrode film layer (the active material is a high-nickel ternary material).

[0093] (3) Hot pressing

[0094] Hot pressing is performed in an environment with an ambient humidity of 0.04% and -60 degrees Celsius, with hot pressing parameters of 7 MPa, 90°C, and 120 seconds, so that the solid-state battery obtained in step (2) maintains a relatively stable structure and avoids pole piece dislocation caused by looseness.

[0095] (4) Filling

[0096] The hot-pressed solid-state battery is placed in a glue injection mold. The single side of the glue injection mold is 1mm larger than the outer contour of the solid-state battery. After sealing, hot melt glue (polyolefin) is injected. The injection pressure is 0.5Mpa, the temperature is 200°C, and the holding time is 10s. Then, cooling water is passed into the water channel inside the glue injection mechanism for 10s to allow the polyolefin to cool and harden rapidly, filling and fixing the negative electrode sheet beyond the position of the positive electrode sheet, thereby forming insulating support parts on all four sides of the stack.

[0097] (5) Packaging

[0098] Then, the battery is packaged with aluminum-plastic film in an environment with an ambient humidity of 0.04% and a temperature of -60°C, and then sealed under negative pressure to ensure that the solid-state battery is isolated from the environment.

[0099] (6) Compression

[0100] In an atmospheric environment, a warm isostatic press (warm isostatic pressing parameters are 600 MPa, 90°C, 30 min) is used to perform six-sided pressurization to produce a solid-state battery.

[0101] Example 2

[0102] The same preparation as in Example 1 was performed except that Kraft AB glue was used as the hot melt adhesive.

[0103] Comparative Example 1

[0104] The same procedure as in Example 1 was carried out except that the filling step (4) was not carried out.

[0105] Next, the safety performance of the all-solid-state batteries obtained in Examples and Comparative Examples was evaluated.

[0106] CT images of the electrode stacks of Examples 1 and 2 were taken at 150 kV, 120 uA, and a cutting depth of 5 mm, confirming that none of the negative electrode sheets were broken. Figure 4 is a CT image of the solid-state battery of Example 1. As shown in Figure 4, the hot melt adhesive fills the gaps and covers the ends of the negative electrode extensions, and the electrode sheets are not broken, indicating good battery safety. Furthermore, the solid-state batteries of the examples were disassembled, and it was again confirmed that no electrode sheets were broken.

[0107] In addition, the solid-state battery from Comparative Example 1 was disassembled to confirm that the electrode was broken and copper was exposed and overlapped. A digital camera was used to photograph the disassembled portion, as shown in Figure 5. The area indicated by the black frame in Figure 5 shows copper leakage, indicating an internal short circuit in the battery.

[0108] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, wherein: It includes a first pole piece, a second pole piece and an insulating support portion, The first pole piece and the second pole piece are alternately stacked along a first direction to form a stacked body. The first pole piece has a protruding portion protruding outward compared to the second pole piece, and a gap is formed between the protruding portions adjacent to each other in the first direction. The insulating support portion includes a filling portion and a covering portion, the filling portion filling the gap portion, and the covering portion covering an end portion of the protruding portion.

2. The secondary battery according to claim 1, wherein The filling part is connected to the covering part and fills the gap part. Optionally, the filling portion is filled to an end portion of the second pole piece located in the gap portion.

3. The secondary battery according to claim 1 or 2, wherein: The height of the filling portion in the first direction is equal to the height of the gap portion in the first direction.

4. The secondary battery according to any one of claims 1 to 3, wherein The covering portion and the filling portion are integrally formed.

5. The secondary battery according to any one of claims 1 to 4, wherein The covering portion covers the entire stacked body along the first direction.

6. The secondary battery according to any one of claims 1 to 5, wherein An insulating support portion is formed outside the stacked body and around the entire circumference of the stacked body.

7. The secondary battery according to any one of claims 1 to 6, wherein The secondary battery comprises N+1 layers of the first pole piece and N layers of the second pole piece, N≥1, A solid electrolyte membrane is disposed between the first pole piece and the second pole piece stacked adjacent to each other in a first direction, The first pole piece is a negative pole piece, and the second pole piece is a positive pole piece.

8. The secondary battery according to claim 7, wherein The laminated body formed with the insulating support portion is subjected to compression processing, The compression treatment is: under a pressure greater than 0 MPa and less than or equal to 1000 MPa, optionally under a pressure of 50 MPa to 1000 MPa, the laminated body having the insulating support portion formed thereon is compressed. Each surface is pressurized, and optionally, the laminated body formed with the insulating support portion is subjected to isostatic pressing.

9. The secondary battery according to any one of claims 1 to 8, wherein The material of the insulating support portion includes a high molecular polymer. Optionally, the glass transition temperature of the high molecular polymer is -30°C to 200°C.

10. A method for preparing a secondary battery, wherein: The steps include: A stacking step: alternately stacking a first pole piece and a second pole piece along a first direction to form a stacked body, wherein the first pole piece is formed with an extension portion extending outward compared to the second pole piece, and a gap portion is formed between adjacent extension portions in the first direction; and Filling step: Filling the gap and the end of the extension portion with a slurry containing a high molecular polymer to form an insulating support portion.

11. The preparation method according to claim 10, wherein: Before the stacking step, a negative electrode film layer is arranged on at least one surface of the negative electrode collector to form the first electrode sheet, a positive electrode film layer is arranged on at least one surface of the positive electrode collector to form the second electrode sheet, and a solid electrolyte is coated on the surface of the first electrode sheet or the second electrode sheet to form a solid electrolyte membrane.

12. The preparation method according to claim 10 or 11, wherein: In the filling step, the slurry is filled by dipping, coating or injecting.

13. The preparation method according to any one of claims 10 to 12, wherein A compression step is also included after the padding step: The surfaces of the laminated body formed with the insulating support portion are pressurized at a pressure greater than 0 MPa and less than or equal to 1000 MPa, and optionally at a pressure of 50 MPa to 1000 MPa. Optionally, the laminated body formed with the insulating support portion is subjected to isostatic pressing.

14. An electrical device, wherein: A secondary battery comprising the secondary battery according to any one of claims 1 to 9, or a secondary battery obtained by the preparation method according to any one of claims 10 to 13.

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