Laminated battery, preparation method of positive electrode sheet, and electric device

Abstract

The embodiment of the application provides a laminated battery, a preparation method of a positive electrode tab and an electric device, wherein the provided laminated battery discards the traditional negative electrode double-end structure, adopts a first positive electrode tab end with only a single positive active material layer, eliminates the invalid outer negative electrode tab, improves the utilization rate of the negative electrode material, saves the internal space of the battery cell, and thus improves the energy density of the laminated battery; meanwhile, through the positive electrode single-end structure, all the negative electrode tabs can realize double-side lithium intercalation, ensures uniform expansion stress during the lithium intercalation process of the high-silicon negative electrode, avoids problems such as tab curling, coating falling off, current collector breaking and the like, and improves the cycle life and structural stability of the battery cell; in addition, a first insulating coating is coated on the other side of the first positive electrode tab, thereby protecting the empty foil area and improving the safety of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a stacked battery, a method for preparing a positive electrode, and an electrical device. Background Technology

[0002] Currently, in the lithium-ion battery stacking process, the outermost layer of the bare cell generally adopts a negative electrode double-sided sheet and a separator as the finishing structure. That is, after the stacking is completed, the outermost part of the cell consists of an electrode sheet and a separator coated with negative electrode active material on both sides.

[0003] However, in the traditional structure described above, the outermost double-sided negative electrode sheet, which faces outward and is not opposite to the positive electrode, cannot participate in the lithium intercalation reaction and becomes an ineffective active material. This increases the weight and thickness of the cell, directly reducing the overall energy density of the cell. At the same time, with the development of high energy density requirements, negative electrode materials tend to adopt high silicon content systems. However, silicon materials undergo a huge volume expansion of about 300% during lithium intercalation, which causes severe uneven stress on both sides of the outermost negative electrode sheet, generating huge internal stress. This makes it very easy for the electrode sheet to bend to one side, wrinkle, or even cause the active coating to peel off from the current collector, thereby causing a sharp drop in cell capacity, a rapid decline in cycle life, and even internal short circuits. Summary of the Invention

[0004] This application provides a method for preparing a stacked battery, a positive electrode sheet, and an electrical device, aiming to improve the problem that the existing stacked battery structure easily affects the energy density and cycle life of the battery cell.

[0005] To solve the above problems, this application provides the following technical solution: This application proposes a stacked battery, which includes two first positive electrode plates, a negative electrode plate, and a second positive electrode plate stacked together. The first positive electrode plate includes a first positive current collector, a first positive active material layer disposed on one surface of the first positive current collector, and a first insulating coating disposed on the other surface of the first positive current collector. The second positive electrode plate includes a second positive current collector and a second positive active material layer disposed on both surfaces of the second positive current collector. The negative electrode is disposed between the two first positive electrode sheets, and the first positive active material layer faces the negative electrode sheet. A second positive electrode sheet is disposed between adjacent negative electrode sheets.

[0006] The stacked battery provided in this application abandons the traditional double-sided negative electrode termination structure and adopts a first positive electrode sheet with only a single-sided positive electrode active material layer to terminate the battery. This eliminates ineffective outer negative electrode sheets, improves the utilization rate of negative electrode materials, and saves internal space of the cell, thereby increasing the energy density of the stacked battery. At the same time, the single-sided positive electrode termination structure enables all negative electrode sheets to achieve double-sided lithium insertion, ensuring uniform expansion stress during the lithium insertion process of high-silicon negative electrodes, avoiding problems such as electrode sheet curling, coating peeling, and current collector breakage, and improving the cycle life and structural stability of the cell. In addition, a first insulating coating is applied to the empty foil area on the other side of the first positive electrode sheet to protect the empty foil area and improve the safety of the cell.

[0007] Furthermore, in the stacked battery, the first insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the first insulating coating is 5 μm to 30 μm; and / or, The adhesive strength of the first insulating coating is >100 N / m.

[0008] Furthermore, in the stacked battery, the first positive electrode sheet further includes a second insulating coating, which is disposed on the surface of the first positive current collector along the edge of the first positive active material layer. The second positive electrode sheet further includes a third insulating coating, which is disposed on the surface of the second positive current collector along the edge of the second positive active material layer.

[0009] Furthermore, in the stacked battery, the second insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the second insulating coating is 5 μm to 30 μm; and / or, The adhesion strength of the second insulating coating is >100 N / m; and / or, The third insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the third insulating coating is 5μm~30μm; and / or, The adhesion strength of the third insulating coating is >100N / m.

[0010] Furthermore, in the stacked battery, the porosity of the first positive electrode active material layer is 15%~35%; and / or, The porosity of the second positive electrode active material layer is 15%~35%.

[0011] Furthermore, in the stacked battery, the thickness of the first positive electrode active material layer is 30 μm to 150 μm; and / or, The thickness of the second positive electrode active material layer is 30μm~150μm; Furthermore, in the stacked battery, the areal density of the second positive electrode active material layer disposed on both surfaces of the second positive electrode current collector is the same; and / or, The negative electrode sheet includes a negative current collector and negative active material layers disposed on two surfaces of the negative current collector, wherein the areal density of the negative active material layers disposed on the two surfaces of the negative current collector is the same.

[0012] Furthermore, in the stacked battery, the negative electrode active material layer includes a silicon-based negative electrode material.

[0013] Furthermore, in the stacked battery, the stacked battery also includes a separator, which is folded and cyclically disposed between the negative electrode and the first positive electrode, and between the negative electrode and the second positive electrode.

[0014] This application also proposes a method for preparing a positive electrode sheet, used to prepare the aforementioned first and second positive electrode sheets, comprising: A gap coating method is used to coat the first insulating paste and the first positive electrode paste on the first surface of the positive electrode current collector. A second positive electrode slurry is coated onto the second surface of the positive electrode current collector using a continuous coating method to obtain a positive electrode preform. After the positive electrode preform is dried, the first positive electrode sheet is die-cut out in the coating area of ​​the first insulating slurry, and the second positive electrode sheet is die-cut out in the coating area of ​​the first positive electrode slurry.

[0015] Further, in the preparation method, coating the first insulating paste and the first positive electrode paste in the gap between the first surface of the positive electrode current collector includes: A first insulating paste is applied by gravure coating in a first region of the first surface, and then the first positive electrode paste is applied by extrusion coating in a second region of the first surface, wherein the first region is different from the second region.

[0016] Furthermore, in the preparation method, after coating the second positive electrode slurry onto the second surface of the positive electrode current collector, the method further includes: A second insulating paste is applied to both sides of the positive current collector near the tab edge.

[0017] This application also proposes an electrical device comprising a stacked battery as described above, wherein the battery serves as the power supply for the electrical device. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the first angle structure of the stacked battery in the embodiments of this application; Figure 2This is a schematic diagram of the second angle structure of the stacked battery in the embodiments of this application; Figure 3 This is a schematic diagram of the front structure of the first positive electrode sheet in the embodiments of this application; Figure 4 This is a schematic diagram of the back structure of the first positive electrode sheet in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of the second positive electrode in the embodiments of this application; Figure 6 This is a flowchart illustrating the preparation of the first positive electrode and the second positive electrode in one embodiment of this application; Figure 7 This is a flowchart illustrating the preparation of the negative electrode sheet in one embodiment of this application. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] The inventors discovered that in existing lithium-ion battery stacking processes, the outermost layer of the bare cell typically uses a double-sided negative electrode sheet and a separator as the finishing structure. That is, after stacking, the outermost layer of the cell consists of an electrode sheet and a separator coated with negative electrode active material on both sides. However, this traditional structure has the following drawbacks: On the one hand, in the outermost double-sided negative electrode sheet, the negative electrode coating on the side facing outward and not opposite to the positive electrode cannot participate in the lithium intercalation reaction, becoming an ineffective active material, which increases the weight and thickness of the cell and directly reduces the overall energy density of the cell.

[0021] On the other hand, with the increasing demand for high energy density, anode materials tend to adopt high silicon content systems. Silicon materials experience a massive volume expansion of approximately 300% during lithium intercalation. In traditional double-sided anode designs, only the inner side of the outermost anode sheet faces the positive electrode and undergoes lithium intercalation and expansion, while the outer side remains unaffected by lithium intercalation and expansion. This results in severely uneven stress on both sides of the electrode, generating enormous internal stress. This makes the electrode prone to bending and wrinkling to one side, and can even cause the active coating to peel off from the current collector, leading to a sharp drop in cell capacity, a rapid decline in cycle life, and even internal short circuits. These problems severely restrict the commercial application of high-silicon anodes in stacked batteries.

[0022] To address the aforementioned problems, this application provides a stacked battery 100, such as... Figures 1-4As shown, the device includes two first positive electrode plates 10, a negative electrode plate 20, a second positive electrode plate 30, and a separator 40 stacked together. The first positive electrode plate 10 includes a first positive current collector 11, a first positive active material layer 12 disposed on one surface of the first positive current collector 11, and a first insulating coating 13 disposed on the other surface of the first positive current collector 11. The second positive electrode plate 30 includes a second positive current collector 31 and a second positive active material layer 32 disposed on both surfaces of the second positive current collector 31. The negative electrode plate 20 is disposed between the two first positive electrode plates 10, with the first positive active material layer facing the negative electrode plate 20. A second positive electrode plate 30 is disposed between adjacent negative electrode plates 20.

[0023] In this embodiment, the outermost layer of the stacked battery is a first positive electrode sheet with positive active material on only one side, while the middle area uses a negative electrode sheet with negative active material on both sides and a second positive electrode sheet with positive active material on both sides. The stacking sequence starts from one side of the cell and is stacked alternately in the order of "first positive electrode sheet → separator → negative electrode sheet → separator → second positive electrode sheet → negative electrode sheet → separator…first positive electrode sheet". The first positive electrode sheet has the first positive active material layer facing the negative electrode sheet, that is, the side with the positive active material is facing inward and the side with the first insulating coating is facing outward.

[0024] In this embodiment, the traditional double-sided negative electrode termination structure is abandoned. Instead, a first positive electrode sheet with only a single-sided positive electrode active material layer is used for termination, eliminating ineffective outer negative electrode sheets, improving the utilization rate of negative electrode materials, and saving internal space of the cell, thereby increasing the energy density of the stacked battery. At the same time, the single-sided positive electrode termination structure enables all negative electrode sheets to achieve double-sided lithium insertion, ensuring uniform expansion stress during the lithium insertion process of the high-silicon negative electrode, avoiding problems such as electrode sheet curling, coating peeling, and current collector breakage, and improving the cycle life and structural stability of the cell. In addition, a first insulating coating is applied to the empty foil area on the other side of the first positive electrode sheet to protect the empty foil area and improve the safety of the cell.

[0025] Therefore, the stacked battery provided in this application can improve the problem that the existing stacked battery structure easily affects the energy density and cycle life of the cell.

[0026] Charging process: When the battery is charged, lithium ions are released from the positive electrode. These lithium ions move through the electrolyte to the negative electrode and are then embedded in the micropores of the negative electrode material. After the lithium ions are embedded in the negative electrode, the material volume increases, and the electrode expands.

[0027] Discharge process: When the battery is discharged (that is, when we use the battery), lithium ions embedded in the negative electrode are released and move back to the positive electrode.

[0028] In some embodiments, the first insulating coating includes at least one of boehmite and ceramic, that is, the first insulating coating is formed by applying boehmite and / or ceramic materials. The above materials are not only insulating and have high thermal stability, which can fully realize the insulating effect and are not easily decomposed. Moreover, they have high coating feasibility and small coating fluctuations, which can effectively protect the empty foil area and improve the safety of the battery cell.

[0029] In some embodiments, the thickness of the first insulating coating is 5μm to 30μm, which can effectively prevent the insulating coating from being missed or scratched while ensuring the overall energy density.

[0030] In some embodiments, the thickness of the first insulating coating can be a range of one or any two of 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm.

[0031] In some embodiments, the adhesion strength of the first insulating coating is >100 N / m, making the coating less prone to peeling off and ensuring the safety of the battery cell.

[0032] In some implementations, such as Figures 4-5 As shown, the first positive electrode 10 also includes a second insulating coating 14, which is disposed on the surface of the first positive current collector 11 along the edge of the first positive active material layer 12. The second positive electrode 30 also includes a third insulating coating 33, which is disposed on the surface of the second positive current collector 31 along the edge of the second positive active material layer 32. By disposing the second and third insulating coatings on the edge of the first positive active material layer and the second positive active material layer, respectively, burrs on the surfaces of the first and second positive current collectors can be effectively prevented from piercing the separator and forming a short circuit with the negative electrode, further improving the safety of the battery cell.

[0033] In some embodiments, a first positive electrode tab 15 is also provided on the first positive electrode plate 10, and a second positive electrode tab 34 is also provided on the second positive electrode plate 30. The second insulating coating 14 is disposed on the surface of the first positive electrode current collector 11 along the edge of the first positive electrode active material layer 12 near the first positive electrode tab 15, and the third insulating coating 33 is disposed on the surface of the second positive electrode current collector 31 along the edge of the second positive electrode active material layer near the second positive electrode tab 34. This can effectively prevent burrs on the surface from piercing the separator and forming a short circuit with the negative electrode, thereby improving the safety of the battery cell.

[0034] In some embodiments, the second insulating coating includes at least one of boehmite and ceramic, that is, the first insulating coating is formed by applying boehmite and / or ceramic materials. The above materials are not only insulating and have high thermal stability, which can fully realize the insulating effect and are not easily decomposed. Moreover, they have high coating feasibility and small coating fluctuations, which can effectively protect the empty foil area and improve the safety of the battery cell.

[0035] In some embodiments, the thickness of the second insulating coating is 5μm to 30μm, which can effectively prevent the insulating coating from being missed or scratched while ensuring the overall energy density.

[0036] In some embodiments, the thickness of the second insulating coating can be a range of one or any two of 5μm, 6μm, 8μm, 10μm, 15μm, 20μm, 25μm, and 30μm.

[0037] In some embodiments, the adhesion strength of the second insulating coating is >100 N / m, making the coating less prone to peeling off and ensuring the safety of the battery cell.

[0038] In some embodiments, the third insulating coating includes at least one of boehmite and ceramic, that is, the first insulating coating is made of boehmite and / or ceramic materials. The above materials are not only insulating and have high thermal stability, which can fully realize the insulating effect and are not easily decomposed. Moreover, they have high coating feasibility and small coating fluctuations, which can effectively protect the empty foil area and improve the safety of the battery cell.

[0039] In some embodiments, the thickness of the third insulating coating is 5μm to 30μm, which can effectively prevent the insulating coating from being missed or scratched while ensuring the overall energy density.

[0040] In some embodiments, the thickness of the third insulating coating can be a range of one or any two of 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm.

[0041] In some implementations, the adhesion strength of the third insulating coating is >100 N / m, making the coating less prone to peeling off and ensuring the safety of the battery cell.

[0042] In some implementations, the porosity of the first positive electrode active material layer is 15% to 35%, which facilitates electrolyte wetting, ensures subsequent cell cycle performance, and also takes into account the energy density of the battery.

[0043] In some embodiments, the porosity of the first positive electrode active material layer can be a range of one or any two of 15%, 16%, 18%, 20%, 25%, 30%, and 35%.

[0044] In some embodiments, the thickness of the first positive electrode active material layer is 30μm~150μm, which can effectively balance energy density, poor low-temperature discharge performance and processing difficulty.

[0045] In some embodiments, the thickness of the first positive electrode active material layer can be a range of one or any two of 30 μm, 32 μm, 35 μm, 40 μm, 50 μm, 80 μm, 100 μm, 120 μm, and 150 μm.

[0046] In some implementations, the porosity of the second positive electrode active material layer is 15% to 35%, which facilitates electrolyte wetting, ensures subsequent cell cycle performance, and also takes into account the energy density of the battery.

[0047] In some embodiments, the porosity of the second positive electrode active material layer can be a range of one or any two of 15%, 16%, 18%, 20%, 25%, 30%, and 35%.

[0048] In some embodiments, the thickness of the second positive electrode active material layer is 30μm~150μm, which can effectively balance energy density, poor low-temperature discharge performance and processing difficulty.

[0049] In some embodiments, the thickness of the second positive electrode active material layer can be one or any two of the following: 30 μm, 32 μm, 35 μm, 40 μm, 50 μm, 80 μm, 100 μm, 120 μm, and 150 μm.

[0050] In some embodiments, the areal density of the second positive electrode active material layer disposed on both surfaces of the second positive electrode current collector is the same. In this embodiment, curling is avoided by controlling the areal density of the second positive electrode sheet to be consistent on both sides.

[0051] Optionally, in one embodiment, the layer structure of the first positive electrode and the second positive electrode can be detected by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS).

[0052] Optionally, in one embodiment, the first positive electrode active material layer and the second positive electrode active material layer independently include a positive electrode active material, wherein the positive electrode active material includes at least one of lithium metal oxide and polyanionic compound.

[0053] Optionally, in one embodiment, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium-rich manganese-based oxide, lithium nickel manganese oxide, and lithium vanadium oxide phosphate.

[0054] The first positive current collector and the second positive current collector can be independently selected as metal foil or composite current collector.

[0055] Optionally, in one embodiment, the first positive current collector and the second positive current collector independently include at least one of pure aluminum current collector and composite aluminum current collector.

[0056] Optionally, in one embodiment, the first positive current collector and the second positive current collector are pure aluminum current collectors, and the thickness of the pure aluminum current collector is 8~15 μm, for example, it can be one or any two of the following values: 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm.

[0057] Optionally, in one embodiment, the composite aluminum current collector includes a polymer substrate layer, a base layer, and a conductive layer stacked together, wherein the base layer is disposed between the polymer substrate layer and the conductive layer, and the base layer is used to increase the bonding force between the polymer substrate layer and the conductive layer.

[0058] In this embodiment, by providing an underlayer between the polymer substrate layer and the conductive layer, the bonding force between the polymer substrate layer and the conductive layer can be increased.

[0059] Optionally, in one embodiment, the material of the polymer substrate layer is selected from one or more blends or copolymers of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyamide (PA), and polyphenylene sulfide (PPS). The thickness of the polymer substrate layer can be 1~8 μm, which can effectively balance safety, battery energy density, and processing economy.

[0060] Optionally, the thickness of the polymer substrate layer can be a range of one or any two of 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm.

[0061] Optionally, in one embodiment, the material of the underlayer is selected from one or more composites of metallic nickel, metallic titanium, and aluminum oxide, and the thickness of the underlayer is 10~1000 nm, which can effectively increase the bonding force between the polymer substrate layer and the conductive layer.

[0062] Optionally, the thickness of the underlayer can be 10 nm, 15 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 800 nm, or 1000 nm.

[0063] Optionally, in one embodiment, the conductive layer can be metallic aluminum or aluminum alloy, and the thickness of the conductive layer can be 0.1~2 μm, which is convenient to prepare by physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating and other methods, and can also effectively improve the overall conductivity of the composite current collector.

[0064] Optionally, the thickness of the conductive layer can be one or any two of the following: 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm.

[0065] In the battery provided in this application embodiment, the first positive electrode active material layer and the second positive electrode active material layer also independently include a first conductive agent and a first binder; optionally, the first conductive agent includes at least one of graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black (Super P), acetylene black, and furnace black, and the first binder includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silicone rubber, styrene-butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), boronized polyethylene glycol, cellulose, cellulose ester, cellulose ether, nitrocellulose, carboxyalkyl cellulose, cellulose salt, sodium carboxymethyl cellulose and cellulose salt derivatives, polyacrylic acid (PAA), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), and polyimide (PI).

[0066] In some embodiments, the mass percentage of each component in the first positive electrode active material layer and the second positive electrode active material layer is: 80-99 wt% of positive electrode active material, 0.5-10 wt% of first conductive agent, and 0.5-10 wt% of additives.

[0067] When the mass ratio of the positive active material in the first positive electrode active material layer and the second positive electrode active material layer is within the above range, each positive electrode sheet can have a high specific capacity, which can fully utilize the rate performance of the battery and meet the battery's fast charging and discharging requirements.

[0068] In some embodiments, the first positive electrode active material layer and the second positive electrode active material layer also independently contain 0.1~30wt% of solid electrolyte, while the proportions of the remaining components remain unchanged. Solid electrolytes include, but are not limited to, one or more of the following: NASICON (sodium fast ion conductor) type solid electrolyte, LISICON (lithium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, perovskite type solid electrolyte, anti-perovskite type solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolytes. Polymer electrolytes include polymers and lithium salts; polymers include, but are not limited to, PEO (ethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile); lithium salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, and LiDFOB.

[0069] In some embodiments, the first positive electrode is prepared in the following manner: (1) Single-sided coated rolls: The components used to prepare the first positive electrode sheet, including the above-mentioned positive active material, the first binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry. This is achieved through a single-sided coating mode using a coating machine. The positive electrode paste is coated on one side of the aluminum foil, and an insulating coating is applied to the other side. The thickness of the insulating coating is 5~30μm.

[0070] (2) Positive electrode rolling Single-sided roller pressing control is used to suppress curling and ensure flatness, while controlling thickness and porosity. The roller pressing pressure is controlled at 50~100 tons, which can roll to the corresponding thickness while avoiding over-pressure of the positive electrode material, which could cause particle breakage and electrode breakage.

[0071] (3) Slitting and tab forming Using metal die-cutting or laser die-cutting, the outline of the electrode tab is die-cut on the edge of the electrode sheet, and at the same time it is cut to the length of the single electrode sheet, for example, 5cm~150cm.

[0072] In some embodiments, the second positive electrode is prepared in the following manner: (1) Double-sided coated rolls: The components used to prepare the first positive electrode sheet, including the above-mentioned positive active material, the first binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry. A double-layer coating machine is used to continuously coat the positive electrode slurry on both sides of the aluminum foil (positive electrode current collector). After coating, the solvent is dried in a drying oven to form a double-sided coating area. During coating, it is necessary to control the surface density of both sides to avoid curling.

[0073] (2) Positive electrode rolling A double-roll press is used to compact the coating on both sides simultaneously, controlling the thickness and porosity.

[0074] (3) Slitting and tab forming Metal die-cutting or laser die-cutting is used to die-cut the electrode tab outline on the edge of the electrode sheet, and at the same time cut to the length of the single electrode sheet.

[0075] This application also proposes a method for preparing a positive electrode sheet, used to prepare the aforementioned first and second positive electrode sheets, comprising steps 201 to 203: Step 201: Using a gap coating method, the first insulating paste and the first positive electrode paste are gap coated on the first surface of the positive electrode current collector; Step 203: Using a continuous coating method, a second positive electrode slurry is coated on the second surface of the positive electrode current collector to obtain a positive electrode preform; Step 205: After drying the positive electrode preform, the first positive electrode sheet is die-cut out in the coating area of ​​the first insulating slurry, and the second positive electrode sheet is die-cut out in the coating area of ​​the first positive electrode slurry.

[0076] In this embodiment, the first insulating slurry is used to form the first insulating coating; the first positive electrode slurry is used to form the first positive electrode active material layer, and may include the above-mentioned positive electrode active material, the first adhesive and any other components dispersed in a solvent such as N-methylpyrrolidone; the second positive electrode slurry is used to form the second positive electrode active material layer, and may also include the above-mentioned positive electrode active material, the first adhesive and any other components dispersed in a solvent such as N-methylpyrrolidone.

[0077] In this embodiment of the application, during the die-cutting process, metal die-cutting or laser die-cutting can be used to die-cut the electrode tab outline on the edge of the electrode sheet and simultaneously cut to the length of the single electrode sheet.

[0078] In this embodiment, by gap-coating a first insulating slurry and a first positive electrode slurry on one surface of the positive current collector, and continuously coating a second positive electrode slurry on another surface, then drying and die-cutting according to the coating areas of the first insulating slurry and the first positive electrode slurry, a first positive electrode sheet and a second positive electrode sheet can be obtained simultaneously.

[0079] In some embodiments, coating a first insulating paste and a first positive electrode paste onto the first surface gap of the positive current collector includes: A first insulating paste is applied by gravure coating in a first region of the first surface, and then the first positive electrode paste is applied by extrusion coating in a second region of the first surface, wherein the first region is different from the second region.

[0080] In this embodiment, a first insulating slurry is first applied to a first region of the first surface of the positive current collector using a gravure coating to form a first insulating coating. Then, a positive electrode active material layer is formed by applying a first positive electrode slurry to a second region of the first surface through extrusion coating, thereby forming a first insulating layer and a positive electrode active material layer arranged side by side on the first surface.

[0081] In some embodiments, the provided preparation method further includes step 204 after coating the second positive electrode slurry onto the second surface of the positive electrode current collector: A second insulating slurry and a third insulating slurry are applied to both sides of the positive current collector near the edge of the tab.

[0082] In this embodiment, the second insulating slurry is used to form the second insulating coating and the third insulating coating. By applying the insulating slurry to both sides of the positive current collector near the tab side edge, the first positive electrode sheet with both the first and second insulating coatings and the third insulating coating can be obtained by die cutting. This effectively prevents burrs on the surface of the positive current collector from piercing the separator and forming a short circuit with the negative electrode, further improving the safety of the battery cell.

[0083] In some implementations, such as Figure 6 As shown, the first positive electrode and the second positive electrode are prepared in the following manner: (1) Coated roll material: The components used to prepare the first positive electrode sheet, including the above-mentioned positive active material, the first binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry. An insulating layer is applied to the A side of an Al foil using a gravure coating method, followed by extrusion coating of the positive electrode paste; the insulating coating thickness is 5~30μm. A continuous coating method is used, in which the positive electrode slurry is coated on one side of the B side of the Al foil using a coating machine, and the solvent is dried in a drying oven after coating. A continuous coating method is used to coat the insulating layer on both sides of the Al foil near the tab edge using a coating machine; the thickness of the insulating coating is 5~30μm.

[0084] (2) Positive electrode rolling Roller pressing is used to suppress curling and ensure flatness, while controlling thickness and porosity. The roller pressing pressure is controlled at 50-100 tons, which can roll to the corresponding thickness while avoiding over-pressure of the positive electrode material, which could cause particle breakage and electrode breakage.

[0085] (3) Slitting and tab forming Metal die-cutting or laser die-cutting is used to die-cut the electrode tab outline on the edge of the electrode sheet, and at the same time cut to the length of the single electrode sheet.

[0086] In some implementations, during the die-cutting process of the first and second positive electrode sheets, the length and width tolerances of the electrode sheets are controlled within ±0.2mm to ensure alignment of subsequent stacking. After cutting, the positive electrode sheet is rectangular, and the positive electrode tab is rectangular or trapezoidal, with chamfering. After die-cutting, online burr detection (such as laser ranging or microscopic sampling) is required, and the burrs must be smaller than the coating thickness (usually ≤15μm) to avoid puncturing the diaphragm.

[0087] In some embodiments, the positive electrode sheet is prepared by fibrillation: the components used to prepare the positive electrode sheet, such as the positive active material, binder and any other components, are mixed, and shear force is applied to the mixed powder to fibrillate the binder to obtain a preform; the preform is extruded or rolled into a self-supporting film; the self-supporting film is loaded onto a positive current collector that is rolled between two rollers and has a base coating on its upper and lower surfaces, and after processes such as rolling, cutting and slitting, the positive electrode sheet can be obtained.

[0088] In some embodiments, the negative electrode sheet 20 includes a negative electrode current collector 21 and negative electrode active material layers 22 disposed on both surfaces of the negative electrode current collector 21, wherein the areal density of the negative electrode active material layers 22 disposed on both surfaces of the negative electrode current collector 21 is the same. In this embodiment, curling is avoided by controlling the areal density of both sides of the negative electrode sheet to be consistent.

[0089] In some embodiments, the negative electrode active material layer includes a silicon-based negative electrode material. Specifically, the silicon-based negative electrode material can be silicon-carbon material, silicon-oxygen-carbon material, etc., such as one or more of fumed silicon-carbon, milled silicon-carbon, silicon suboxide, pre-lithiated silicon suboxide, and pre-magnesiated silicon suboxide. Because the embodiments of this application use a single-sided positive electrode termination and coat an insulating layer on the single-sided empty foil, all negative electrode sheets can achieve double-sided lithium intercalation. This not only improves the energy density but also ensures uniform expansion stress on the negative electrode sheets during the process, avoiding electrode curling, coating peeling, and current collector breakage. It effectively improves the problem of high-silicon single-sided lithium intercalation electrode sheet detachment and is therefore suitable for high-silicon negative electrode materials.

[0090] In some embodiments, the negative electrode sheet can be a graphite negative electrode, a silicon-oxygen negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a tin negative electrode, a tin oxide negative electrode, a tin alloy negative electrode (Sn-Fe, Sn-Co, Sn-Cu, etc.), a lithium metal sheet, or a lithium alloy sheet, and the thickness is 0~100 μm. The lithium alloy Li-M can be an alloy formed by lithium metal with one or more of the following substances: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, and phosphorus, wherein the lithium metal content is 1~99% by mass.

[0091] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a second conductive agent, a second binder, and a thickener.

[0092] In one embodiment, the negative electrode active material includes, but is not limited to, one or more of lithium metal (Li) or lithium metal alloy (Li-M), artificial graphite, natural graphite, modified graphite, fast-charging graphite, soft carbon, hard carbon, fumed silicon carbide, ground silicon carbide, silicon suboxide, pre-lithiated silicon suboxide, and pre-magnesiated silicon suboxide; wherein, the lithium metal alloy (Li-M) can be an alloy formed by lithium metal and one or more of the following substances: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, and phosphorus, wherein the mass content of lithium metal is 1-99%.

[0093] In some embodiments, the second conductive agent includes one or more of Super-P (conductive carbon black), VGCF (vapor-grown carbon fiber), and CNT (carbon nanotube).

[0094] In some embodiments, the second adhesive includes one or more of PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber), NBR (nitrile rubber), BR (polybutadiene rubber), CMC (sodium carboxymethyl cellulose), and PAA (polyacrylic acid).

[0095] In some embodiments, the thickener includes one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0096] In some embodiments, the mass percentage of each component in the negative electrode active material layer is: 80-100 wt% negative electrode active material, 0-10 wt% conductive agent and 0-10 wt% binder.

[0097] The negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes one or more of aluminum, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0098] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically formed by coating a negative electrode slurry, consisting of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components, onto a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited to it.

[0099] In some embodiments, the negative electrode sheet 20 is further formed with a negative electrode tab 23.

[0100] In some embodiments, when the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, such as Figure 7As shown, the negative electrode sheet is prepared as follows: The components used to prepare the negative electrode sheet, such as the negative electrode active material, binder and conductive agent, are dispersed in a solvent such as deionized water to form a negative electrode slurry; the negative electrode slurry is coated on both sides of a negative electrode current collector such as copper foil; after baking, rolling, cutting and slitting, the negative electrode sheet can be obtained.

[0101] The cutting process involves using metal or laser die-cutting to control burrs and dimensional accuracy, and to shape the negative electrode tab position. The negative electrode die-cutting burrs are ≤10μm, effectively preventing negative electrode burrs from piercing the diaphragm.

[0102] The electrode sheet has an empty foil area at the edge for cutting the tab. After cutting, the negative electrode sheet is rectangular and the negative electrode tab is rectangular or trapezoidal, and the corners are beveled.

[0103] The battery provided in this embodiment of the invention also includes a separator 40, which is disposed between the negative electrode 20 and the first positive electrode 10, and between the negative electrode 20 and the second positive electrode 30.

[0104] In some embodiments, the diaphragm 40 is folded and cyclically disposed between the negative electrode 20 and the first positive electrode 10, and between the negative electrode 20 and the second positive electrode 30, so that it can be bent in a "Z" shape throughout the entire stacked structure to achieve effective isolation between the positive and negative electrodes.

[0105] In some embodiments, the diaphragm includes a base membrane, which may be one or more of PE diaphragm, PP diaphragm, nonwoven fabric diaphragm, and PI diaphragm.

[0106] In some embodiments, the diaphragm is a PE diaphragm with high air permeability and high mechanical strength.

[0107] In some embodiments, the base film has a coating on at least one side; the coating comprises: an oxide solid electrolyte, an alkaline oxide, and a polymer adhesive; the oxide solid electrolyte and the alkaline oxide are dispersed in the polymer adhesive; the alkaline oxide includes at least one of alumina and boehmite. The oxide solid electrolyte includes at least one of NASICON-type solid electrolyte, garnet-type solid electrolyte, and perovskite-type solid electrolyte.

[0108] The battery provided in this application embodiment also includes an electrolyte.

[0109] The electrolyte plays a role in conducting ions between the positive and negative electrodes. The electrolyte can be in liquid or gel state.

[0110] Electrolytes include electrolytes, which include liquid electrolytes, semi-solid electrolytes, and all-solid electrolytes. Semi-solid electrolytes are obtained by mixing liquid electrolytes and solid electrolytes in any proportion.

[0111] Liquid electrolytes, semi-solid electrolytes, and all-solid electrolytes are all used in one or more of the following: pouch cells, cylindrical cells, or prismatic cells.

[0112] In some embodiments, the electrolyte may be selected from inorganic solid electrolytes (halide solid electrolytes, oxide solid electrolytes, sulfide solid electrolytes), polymer solid electrolytes, and composite solid electrolytes (inorganic filler + polymer matrix).

[0113] In some embodiments, the solid electrolyte includes, but is not limited to, one or more of the following: NASICON (sodium fast ion conductor) type solid electrolyte, LISICON (lithium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, perovskite type solid electrolyte, anti-perovskite type solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolyte. Polymer electrolytes include polymers and lithium salts; polymers include, but are not limited to, PEO (ethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile); lithium salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, and LiDFOB.

[0114] In some embodiments, the electrolyte is a liquid electrolyte comprising an electrolyte salt and a solvent. The electrolyte salt is a lithium salt, and the solvent may be a carbonate, ether, nitrile, etc. In some embodiments, the solvent includes, but is not limited to, one or more of the following: ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, diphenyl carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, and acetonitrile AN.

[0115] In some implementations, additives may be added to the liquid electrolyte. These additives can be general types such as those for film formation, flame retardancy, overcharge protection, and low-temperature improvement, or they can be interface stabilizers for lithium anodes such as FEC and LiNO3.

[0116] In some embodiments, the electrolyte is a gel electrolyte, comprising a polymer matrix, a plasticizing solvent, and a lithium salt.

[0117] In some embodiments, the electrolyte is an in-situ polymerized electrolyte, comprising polymer monomers, lithium salts, solvents, and initiators.

[0118] In some embodiments, the electrolyte is a eutectic electrolyte, comprising a small molecule polar matrix and a lithium salt; or an ionic liquid electrolyte, comprising an ionic liquid and a lithium salt.

[0119] In some embodiments, the lithium salts mentioned above include, but are not limited to, lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonyate (LiSbF6), lithium bis(trifluoromethanesulfonate imide) (LiTFSI or LiN(SO2CF3)2), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiFSI or LiN(SO2CF3)2), lithium perchlorate (LiClO4), lithium iodide (LiI), and lithium magnesium bis(fluorosulfonyl)imide (Li2Mg(N(SO2CF3)2)2).

[0120] In practical applications, the negative electrode, separator, and positive electrode are stacked in sequence, packaged, and then a bare cell is obtained. After baking, the bare cell is injected with electrolyte, formed, resealed, and sorted to obtain the battery described above.

[0121] In some implementations, a liquid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking negative electrode plates, positive electrode plates, a composite separator, and an electrolyte. In some implementations, a semi-solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking negative electrode plates, positive electrode plates, and gel electrolyte. In some implementations, a semi-solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking negative electrode plates, positive electrode plates, a solid electrolyte, and 0.5-50% electrolyte additives. In some implementations, a solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking negative electrode plates, positive electrode plates, and a solid electrolyte.

[0122] In some implementations, the lamination process is as follows: (1) Initial positioning: Place the first positive electrode sheet (with the insulating coating facing outwards and the positive electrode material coating facing inwards) on the stacking platform and fix it by vacuum adsorption.

[0123] (2) Initial membrane laying: The starting end of the PE membrane is placed on the first positive electrode and extends beyond the edge of the electrode.

[0124] (3) Z-shaped folding cycle: a. Place the negative electrode: Accurately place a double-sided negative electrode sheet on the diaphragm, aligning it with the first positive electrode sheet below (positioned by CCD vision, alignment tolerance ≤ ±0.3mm).

[0125] c. First fold: The stacker grippers fold the diaphragm over the negative electrode sheet from above, covering it.

[0126] d. Place the double-sided positive electrode: Place a second positive electrode on the folded diaphragm, aligning it with the negative electrode.

[0127] e. Second fold: Fold the diaphragm over to cover the second positive electrode sheet on both sides.

[0128] f. Repeat: Continue in the order of "negative electrode sheet → diaphragm fold → second positive electrode sheet → diaphragm fold" until the designed number of layers is reached (the second to last sheet is the negative electrode sheet).

[0129] (4) Termination of sealing: The last piece is the first positive electrode sheet on one side (the negative electrode sheet with the coated side facing down and the insulating coating side facing out). After placement, the separator is finally folded over to cover the electrode sheet, and the separator is cut off. The end of the separator is fixed with hot melt or tape to complete the entire stack.

[0130] The present invention also proposes an electrical device, which includes the aforementioned stacked battery, the stacked battery serving as the power supply for the electrical device.

[0131] Stacked batteries can be used as a power source for electrical devices or as an energy storage unit for electrical devices. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0132] The above-described electrical device embodiment includes the aforementioned stacked battery and achieves the same technical effect. To avoid repetition, it will not be described again here. For relevant details, please refer to the description of the battery embodiment.

[0133] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0134] The present invention will be described in detail below through embodiments.

[0135] Test method: (1) Energy density test: At room temperature of 25℃, the battery is charged at a constant current of 0.1C to 4.25V (different upper limit voltages are set based on different positive electrode materials), and then charged at a constant voltage until the current drops to 0.05C and charging stops; then discharged at 0.1C to the cutoff voltage of 2.8V, the discharge capacity and voltage plateau are recorded, the cell weight is measured, and the battery mass energy density is calculated.

[0136] (2) Cycle life test: The lithium-ion battery was activated by charging and discharging three times at 25°C at a rate of 0.1C / 0.1C and a voltage range of 2.8~4.25V. Then, it was charged and discharged at the same voltage range at a rate of 0.33C / 1C. The capacity of the cell in the first cycle at this rate was recorded in Ah. Then, the number of cycles when the cell capacity retention rate dropped to 80% was recorded.

[0137] Unless otherwise specified, the techniques or conditions described in the literature in this field or the product instructions shall be followed. Reagents or instruments whose manufacturers are not specified are all commercially available standard products.

[0138] Example 1 (1) Preparation of the first positive electrode plate S11. Mix the positive electrode active material, high-nickel ternary material NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 95:3:2. Add NMP solvent and stir under vacuum to form a positive electrode slurry. S12. Achieved by single-sided coating mode of coating machine, positive electrode slurry is coated on one side of aluminum foil, and insulating coating borosilicate with a thickness of 25μm is coated on the other side; S13. Single-sided roller pressing control is used to suppress curling and ensure flatness, while controlling the thickness to 50μm and the porosity to 25%; the roller pressing pressure is controlled at 75 tons.

[0139] S14. Using metal die-cutting, the outline of the electrode tab is die-cut on the edge of the electrode sheet, and at the same time it is cut to the length of the single electrode sheet.

[0140] (2) Preparation of the second positive electrode plate S21. Mix the positive electrode active material, high-nickel ternary material NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 95:3:2. Add NMP solvent and stir under vacuum to form a positive electrode slurry. S22. Using a double-layer coating machine, the positive electrode slurry is continuously coated on both sides of the aluminum foil (positive electrode current collector). After coating, the solvent is dried in a drying oven to form a double-sided coating area. During coating, the surface density of both sides must be controlled to be consistent.

[0141] S23. A double-roll press is used to compact the coating on both sides simultaneously, while controlling the thickness to 50μm and the porosity to 25%.

[0142] S24. Use metal die-cutting or laser die-cutting to cut the outline of the electrode tab on the edge of the electrode sheet, and cut it to the length of the single electrode sheet at the same time.

[0143] (3) Preparation of negative electrode sheet Silica, conductive agent Super P (conductive carbon black), binder CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were uniformly mixed in a mass ratio of 95.5:1.5:1.2:1.8, with deionized water as the solvent. After stirring evenly to obtain a slurry, the mixture was coated onto a copper foil current collector. The negative current collector was a 6μm copper foil. The mixture was then cut into negative electrode sheets for later use.

[0144] (4) Preparation of electrolyte Lithium salt LiFSI was dissolved in the organic solvent dimethyl carbonate (DMC) at a concentration of 1M, and an inert diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE, molar percentage 30%) was added to obtain a liquid electrolyte. (5) Battery manufacturing S51. Place the first positive electrode sheet (with the insulating coating facing outwards and the positive electrode material coating facing inwards) on the stacking platform and fix it by vacuum adsorption.

[0145] S52. Cover the first positive electrode with the starting end of the PE separator and extend it beyond the edge of the electrode.

[0146] S53, Z-shaped folding cycle: a. Place the negative electrode: Accurately place a double-sided negative electrode sheet on the diaphragm, aligning it with the first positive electrode sheet below (positioned by CCD vision, alignment tolerance ≤ ±0.3mm).

[0147] c. First fold: The stacker grippers fold the diaphragm over the negative electrode sheet from above, covering it.

[0148] d. Place the double-sided positive electrode: Place a second positive electrode on the folded diaphragm, aligning it with the negative electrode.

[0149] e. Second fold: Fold the diaphragm over to cover the second positive electrode on both sides.

[0150] f. Repeat: Continue in the order of "negative electrode sheet → diaphragm fold → second positive electrode sheet → diaphragm fold" until the designed number of layers is reached (the second to last sheet is the negative electrode sheet).

[0151] S54. Termination and sealing: The last piece is the first positive electrode sheet on one side (the negative electrode sheet with the coated side facing down and the insulating coating side facing out). After placement, the separator is finally folded over to cover the electrode sheet, and the separator is cut. The end of the separator is fixed with hot melt or tape to complete the entire stack. It is then placed in the outer packaging shell, baked and dried, and injected with the above-mentioned electrolyte. After standing, formation, aging, and capacity testing, the stacked battery is made.

[0152] Examples 2-4 The difference between Examples 2-4 and Example 1 is that, in step S12, the borosilicate is adjusted to be ceramic, the insulating coating thickness is adjusted to 5 μm, and the insulating coating thickness is adjusted to 30 μm, respectively.

[0153] Comparative Example 1 (1) Preparation of positive electrode sheet S11. Mix the positive electrode active material, high-nickel ternary material NCM811, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 95:3:2. Add NMP solvent and stir under vacuum to form a positive electrode slurry. S12. Using a double-layer coating machine, the positive electrode slurry is continuously coated on both sides of the aluminum foil (positive electrode current collector). After coating, the solvent is dried in a drying oven to form a double-sided coating area. During coating, the surface density of both sides must be controlled to be consistent.

[0154] S13. A double-roll press is used to compact the coating on both sides simultaneously, while controlling the thickness to 50μm and the porosity to 25%.

[0155] S14. Use metal die-cutting or laser die-cutting to cut the outline of the electrode tab on the edge of the electrode sheet, and cut it to the length of the single electrode sheet at the same time.

[0156] (2) Preparation of negative electrode sheet Silica, conductive agent Super P (conductive carbon black), binder CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber) were uniformly mixed in a mass ratio of 95.5:1.5:1.2:1.8, with deionized water as the solvent. After stirring evenly to obtain a slurry, the mixture was coated onto a copper foil current collector. The negative current collector was a 6μm copper foil. The mixture was then cut into negative electrode sheets for later use.

[0157] (3) Preparation of electrolyte Lithium salt LiFSI was dissolved in the organic solvent dimethyl carbonate (DMC) at a concentration of 1M, and an inert diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE, molar percentage 30%) was added to obtain a liquid electrolyte. (4) Battery preparation The prepared positive electrode, separator (PP or PE separator), and negative electrode are stacked in sequence, so that each positive electrode film layer and negative electrode film layer are covered with a separator. The outermost layer is the negative electrode. Then, the cells are stacked into the designed number of layers, hot-pressed, and the tabs are welded and put into the outer packaging shell. After baking and drying, the electrolyte is injected. Then, after standing, formation, aging and capacity testing, the stacked battery is made.

[0158] The energy density and cycle life of the batteries in each embodiment and comparative example were tested under constant temperature environment, and the state of the outermost ring of the cell when fully charged was observed. The results are shown in Table 1.

[0159] Table 1

[0160] By comparing Examples 1-4 with Comparative Example 1, it can be seen that the present application can improve the energy density of the laminated battery cell, solve the problem of detachment of the single-sided area of ​​the high silicon content negative electrode sheet due to the difference in expansion stress, and improve the service life of the battery cell.

[0161] In summary, this embodiment abandons the traditional double-sided negative electrode termination structure and adopts a first positive electrode sheet with only a single-sided positive electrode active material layer for termination, eliminating ineffective outer negative electrode sheets, improving the utilization rate of negative electrode materials, and saving internal space of the cell, thereby increasing the energy density of the stacked battery. At the same time, through the single-sided positive electrode termination structure, all negative electrode sheets can achieve double-sided lithium insertion, ensuring uniform expansion stress during the lithium insertion process of high-silicon negative electrodes, avoiding problems such as electrode sheet curling, coating peeling, and current collector breakage, and improving the cycle life and structural stability of the cell. In addition, a first insulating coating is applied to the empty foil area on the other side of the first positive electrode sheet to protect the empty foil area and improve the safety of the cell.

[0162] Terminology Explanation In this application, "multiple" refers to two or more.

[0163] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0164] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0165] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0166] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A stacked battery, characterized in that, The stacked battery includes two first positive electrode sheets, a negative electrode sheet, and a second positive electrode sheet stacked together. The first positive electrode sheet includes a first positive current collector, a first positive active material layer disposed on one surface of the first positive current collector, and a first insulating coating disposed on the other surface of the first positive current collector. The second positive electrode sheet includes a second positive current collector and a second positive active material layer disposed on both surfaces of the second positive current collector. The negative electrode is disposed between the two first positive electrode sheets, and the first positive active material layer faces the negative electrode sheet. A second positive electrode sheet is disposed between adjacent negative electrode sheets.

2. The stacked battery according to claim 1, characterized in that, The first insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the first insulating coating is 5 μm to 30 μm; and / or, The adhesive strength of the first insulating coating is >100 N / m.

3. The stacked battery according to claim 1, characterized in that, The first positive electrode sheet further includes a second insulating coating, which is disposed on the surface of the first positive current collector along the edge of the first positive active material layer. The second positive electrode sheet further includes a third insulating coating, which is disposed on the surface of the second positive current collector along the edge of the second positive active material layer.

4. The stacked battery according to claim 3, characterized in that, The second insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the second insulating coating is 5 μm to 30 μm; and / or, The adhesion strength of the second insulating coating is >100 N / m; and / or, The third insulating coating comprises at least one of burlite and ceramic; and / or, The thickness of the third insulating coating is 5μm~30μm; and / or, The adhesion strength of the third insulating coating is >100N / m.

5. The stacked battery according to claim 1, characterized in that, The porosity of the first positive electrode active material layer is 15%~35%; and / or, The porosity of the second positive electrode active material layer is 15%~35%.

6. The stacked battery according to claim 1, characterized in that, The thickness of the first positive electrode active material layer is 30 μm to 150 μm; and / or, The thickness of the second positive electrode active material layer is 30μm~150μm.

7. The stacked battery according to claim 1, characterized in that, The surface density of the second positive electrode active material layer disposed on both surfaces of the second positive electrode current collector is the same; and / or, The negative electrode sheet includes a negative current collector and negative active material layers disposed on two surfaces of the negative current collector, wherein the areal density of the negative active material layers disposed on the two surfaces of the negative current collector is the same.

8. The stacked battery according to claim 7, characterized in that, The negative electrode active material layer includes silicon-based negative electrode material.

9. The stacked battery according to any one of claims 1 to 8, characterized in that, The stacked battery also includes a separator, which is folded and cyclically disposed between the negative electrode and the first positive electrode, and between the negative electrode and the second positive electrode.

10. A method for preparing a positive electrode sheet, used to prepare the first positive electrode sheet and the second positive electrode sheet as described in claims 1 to 9, characterized in that, include: A gap coating method is used to coat the first insulating paste and the first positive electrode paste on the first surface of the positive electrode current collector. A second positive electrode slurry is coated onto the second surface of the positive electrode current collector using a continuous coating method to obtain a positive electrode preform. After the positive electrode preform is dried, the first positive electrode sheet is die-cut out in the coating area of ​​the first insulating slurry, and the second positive electrode sheet is die-cut out in the coating area of ​​the first positive electrode slurry.

11. The preparation method according to claim 10, characterized in that, Applying a first insulating paste and a first positive electrode paste to the first surface gap of the positive electrode current collector includes: A first insulating paste is applied by gravure coating in a first region of the first surface, and then the first positive electrode paste is applied by extrusion coating in a second region of the first surface, wherein the first region is different from the second region.

12. The preparation method according to claim 10, characterized in that, After coating the second positive electrode slurry onto the second surface of the positive electrode current collector, the process further includes: A second insulating paste is applied to both sides of the positive current collector near the edge of the tab.

13. An electrical appliance, characterized in that, It includes the stacked battery as described in claims 1 to 9, wherein the stacked battery serves as the power supply for the electrical device.

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