Positive pole piece as well as preparation method and application thereof

Abstract

The invention relates to the field of batteries, in particular to a positive pole piece as well as a preparation method and application thereof. The positive pole piece comprises a current collector and a positive active material layer coated on the surface of the current collector, and at least one edge of the positive active material layer is provided with a side coating; and the edge coating comprises the following components in parts by mass: 70-95 parts of oxide, 2-30 parts of electrolyte and 0.5-6 parts of binder. According to the positive pole piece, the edge is not easy to fall off and damage, burrs and molten beads generated during die cutting of aluminum foil are reduced, and the risk of short circuit caused by the burrs is reduced; the possibility of direct contact between the edges of the positive electrode and the negative electrode is avoided, and the structure stability can be supported.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery, in particular to a positive electrode sheet and a preparation method and application thereof. BACKGROUND

[0002] In the manufacturing process of all-solid-state batteries, the interface treatment between the electrode and the solid electrolyte layer is one of the core difficulties. Due to the brittle and hard texture of the solid electrolyte (such as sulfide, halide) and the lack of fluidity of the liquid electrolyte, micron-level burrs or cracks are easily generated at the edge of the electrode in the electrode cutting, laminating or calendering process. These burrs may directly pierce the solid electrolyte layer which is as thin as 20-50 μm after the battery is assembled, resulting in physical contact between the positive and negative electrodes, forming internal short-circuit points.

[0003] For example, if the height of the electrode edge burr exceeds 10% of the electrolyte thickness (such as 3 μm burr corresponding to 30 μm electrolyte), the short-circuit probability will increase by more than 60%. More seriously, the volume expansion of the negative electrode during charging and discharging will further amplify the mechanical stress of the burr, accelerating the interface failure. This failure is hidden - initially it may only show local micro-short circuit, but as the cycle progresses, the short-circuit points will trigger a thermal runaway chain reaction due to the accumulation of joule heat (local temperature > 200℃).

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The present application aims to provide a positive electrode sheet and a preparation method and application thereof. The edge of the positive electrode sheet is not easy to fall off and damage, and the possibility of direct contact between the positive electrode and the negative electrode edge is eliminated.

[0006] In order to achieve the above-mentioned purpose of the present application, the following technical solutions are adopted: One aspect of the present application relates to a positive electrode sheet, comprising a current collector and a positive active material layer coated on the surface of the current collector, and a side coating layer is arranged at least one edge of the positive active material layer; According to the mass fraction, the side coating layer comprises: 70-95 parts of oxide, 2-30 parts of electrolyte and 0.5-6 parts of binder.

[0007] The edge of the positive electrode sheet is not easy to fall off and damage, the burr and bead generated when the aluminum foil is die-cut are reduced, the short-circuit risk caused by the burr is reduced, the possibility of direct contact between the positive electrode and the negative electrode edge is eliminated, and the supporting structure stability can be achieved.

[0008] Another aspect of the present application also relates to a preparation method of the positive electrode sheet, comprising the following steps: A slurry containing the edge coating raw material is coated on at least one edge region of the pole piece on which the positive electrode active material layer has been coated and dried.

[0009] The preparation method of the positive electrode pole piece is an edge coating forming method with simple process and easy implementation.

[0010] Compared with the prior art, the present application has the following beneficial effects: (1) The positive electrode pole piece provided by the present application forms a solid barrier at the edge of the positive electrode, effectively covering, wrapping or passivating the metal burrs and micro-cracks generated by the slitting process, thereby fundamentally preventing them from piercing the thin and brittle solid-state electrolyte layer, thereby greatly reducing the probability of internal short circuit caused by direct contact between the positive and negative electrodes. The presence of the edge coating provides additional support points for the battery stacking structure, which can effectively buffer the mechanical stress generated on the edge of the pole piece during the charging and discharging process, especially when the negative electrode expands in volume. This reduces the risk of active material falling off from the edge and helps maintain the tight contact of the positive electrode / electrolyte interface, improving the interface stability. The solid-state electrolyte component contained in the edge coating helps maintain the lithium ion transport channel in the edge region, reduces the interface impedance, and makes the current distribution more uniform. At the same time, the coating can inhibit the side reactions at the edge of the positive electrode under high voltage (such as electrolyte decomposition), which helps to improve the cycle life and capacity retention rate of the battery. Due to the similar rolling characteristics of the edge coating and the main coating of the positive electrode, defects such as edge curling and wavy edge caused by different material compression ratios can be effectively avoided in the subsequent rolling process, thereby improving the production yield and consistency of the pole piece.

[0011] (2) The preparation method of the positive electrode pole piece provided by the present application uses conventional slurry stirring and coating equipment, without the need to modify the existing large production line. It can embed the edge coating process in the standard positive electrode pole piece manufacturing process, facilitating the rapid promotion and application of the technology. By controlling the viscosity of the slurry and combining with precise coating techniques such as inkjet printing, the width and thickness of the edge coating can be accurately controlled, ensuring that the coating shape is regular, the boundary is clear, and the performance of each pole piece is consistent and reliable. The two-step drying method of "first surface drying, then thorough vacuum drying" can effectively prevent the coating from cracking or curling during the drying process due to rapid solvent evaporation, and ensure that the solvent is fully removed, so that the edge coating and the current collector form a firm bond, avoiding falling off during subsequent processing or use. The slurry preparation method has wide inclusiveness in the selection of binders, oxides and solid-state electrolytes. Enterprises can adjust within the given preferred range according to their own material supply chain and specific performance requirements, and the method is highly versatile. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings required to be used in the description of the specific embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings without creative labor.

[0013] Figure 1 The positive electrode edge coating structure provided by the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be described clearly and completely in combination with the drawings and specific embodiments below. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are all conventional products that can be purchased on the market.

[0015] The edge coating technology of lithium ion battery positive electrode sheet was proposed to meet the demand for improving battery safety and manufacturing defects. Early lithium ion battery sheets used full-width coating process, but the active material coating on the edge of the sheet was prone to burrs, cracks or coating peeling off (especially for high-nickel positive electrode materials) during slitting or winding. These edge defects can pierce the separator and cause internal short circuit of the battery. As the energy density of power batteries increases (such as NCM811, NCA material application), the risk of thermal runaway caused by edge burrs increases. For example, after a car company experienced multiple battery fire accidents caused by edge burrs of the sheet, edge coating technology was included in industry standards (such as GB / T 38031-2020). Since 2010, laser cutting and precision coating technology has matured, providing an engineering basis for edge coating process, and gradually becoming a standard for high-end battery production.

[0016] Edge coating technology achieves the following core functions by coating insulating or buffer materials on the edge area of the sheet: 1. Suppress short circuit risk: Cover the exposed metal current collector (aluminum foil) after cutting the sheet to prevent contact short circuit with the negative electrode; Passivate edge burrs (such as reduce burr height from 5-10 μm to below 1 μm) to reduce the probability of piercing the separator.

[0017] 2. Improve structural stability: reduce the edge of the pole piece in the process of winding / coating flaking, avoid the shedding of active substances; relieve the mechanical stress of the edge of the pole piece during the cycle process (such as the interface protection of the silicon-carbon negative electrode expansion rate>300%).

[0018] 3. Optimize electrochemical performance: inhibit the side reaction of the edge area (such as the decomposition of electrolyte at the edge of the high-voltage positive electrode to produce gas), improve the uniformity of current distribution, and reduce the capacity attenuation caused by polarization.

[0019] Based on the above principles, the present application is proposed.

[0020] One aspect of the present application relates to a positive electrode sheet, comprising a current collector and a positive active material layer coated on the surface of the current collector, and a side coating layer is provided at least one edge of the positive active material layer; According to the mass fraction, the side coating layer comprises: Oxide 70-95 parts, electrolyte 2-30 parts and binder 0.5-6 parts.

[0021] In some specific embodiments, according to the mass fraction, the oxide may be, but not limited to, any one of 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 95 parts, or a range value between any two of them; The electrolyte may be, but not limited to, any one of 2 parts, 5 parts, 10 parts, 15 parts, 20 parts, 24 parts or 30 parts, or a range value between any two of them; The binder may be, but not limited to, any one of 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts or 6 parts, or a range value between any two of them.

[0022] The positive electrode sheet defines the basic function of the structure by limiting the basic components of the side coating layer and its core ratio range. It fundamentally provides a physical barrier to prevent the edge burr from piercing the solid-state electrolyte layer. This specific combination of components ensures that the side coating layer has good electronic insulation (mainly provided by the oxide), certain ion conductivity (provided by the solid-state electrolyte), and the necessary mechanical bonding strength (provided by the binder), thereby significantly reducing the risk of internal short circuit while ensuring normal operation of the battery.

[0023] The present application solves the problem of all-solid-state battery by adding a side coating layer to the edge of the positive electrode sheet coating. The side coating layer has a similar composition to the positive electrode coating, consisting of aluminum oxide, solid-state electrolyte, and binder, and has similar rolling characteristics to the positive electrode sheet, thereby avoiding problems such as edge curling and wavy edges during electrode manufacturing.

[0024] Technical advantages of the present application: (1) Reduce the risk of positive electrode sheet edge shedding and damage; (2) Reduce the burr and bead produced when die-cutting aluminum foil, reduce the risk of short circuit caused by burr; (3) Eliminate the possibility of direct contact between the positive and negative edges, and can play a supporting structure stability role.

[0025] Further, the edge coating includes, in terms of mass fraction: 80-85 parts of oxide, 10-18 parts of electrolyte, and 2-4 parts of binder. Further optimize the ratio range of each component to achieve a better balance of insulation, ionic conductivity and mechanical properties of the edge coating material. The preferred range can ensure that the edge coating better deforms in coordination with the positive active material layer in the rolling process, effectively avoiding defects such as curling and wavy edges caused by mismatch of physical properties, thereby further improving the structural integrity of the electrode sheet and the yield of the battery.

[0026] Further, the width of the edge coating is 1-3 mm, including but not limited to any one of 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, or a range value between any two of them. By limiting the width range of the edge coating, it is ensured that the coating can fully cover the potential burr area of the positive electrode sheet cutting edge, providing an effective protection width. Too narrow may not be fully covered, and too wide will excessively sacrifice the active area and increase the internal resistance of the battery. This range can achieve the optimal balance between safety and energy density.

[0027] Further, the thickness of the edge coating is 90%-110% of the thickness of the positive active material layer, including but not limited to any one of 90%, 95%, 100%, 105% or 110%, or a range value between any two of them. By limiting the proportional relationship between the thickness of the edge coating and the thickness of the positive active material layer, it is ensured that the edge coating can play an effective supporting role after the battery is stacked, avoiding the problems of insufficient support caused by too thin edge coating, or poor positive and negative interface contact and increased internal resistance caused by too thick edge coating. This makes the edge coating compatible with the internal structure of the battery, maintaining the close contact of the interface.

[0028] Further, the binder includes but is not limited to at least one of nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene rubber, polyisoprene, ethylene-methyl acrylate copolymer, or hydrogenated styrene-isoprene-styrene block copolymer, and derivatives thereof. By limiting the specific type of binder, these polymer materials have good flexibility, chemical stability and adhesion to the current collector. The above binder can firmly bond the oxide and electrolyte powders to the edge of the electrode sheet, and is not easy to crack or fall off during the volume change in the rolling and cycling process of battery preparation, ensuring the durability and reliability of the edge coating function.

[0029] In some embodiments, the binder is any one of the binders described above; or, the binder is any two of the binders described above; or, the binder is any three of the binders described above; or, the binder is any four of the binders described above; or, the binder is any five of the binders described above; or, the binder is any six of the binders described above. When the binder includes multiple binders, the binders can be combined in any ratio.

[0030] Further, the oxide includes, but is not limited to, at least one of aluminum oxide, silicon oxide, zirconium oxide, lithium aluminum titanium phosphate, lithium lanthanum zirconium tantalum oxide, or lithium lanthanum titanium oxide, and derivatives thereof. These materials have high hardness and good electrochemical stability. The technical effect is that it can effectively passivate, cover or isolate the metal burrs, prevent the electronic conduction of the burrs even if they exist, and is the core material guarantee for realizing the protection function.

[0031] In some embodiments, the oxide is any one of the oxides described above; or, the oxide is any two of the oxides described above; or, the oxide is any three of the oxides described above; or, the oxide is any four of the oxides described above; or, the oxide is any five of the oxides described above; or, the oxide is any six of the oxides described above. When the oxide includes multiple oxides, the oxides can be combined in any ratio.

[0032] Further, the electrolyte includes, but is not limited to, a sulfide electrolyte. The electrolyte is further limited to a sulfide electrolyte. The sulfide electrolyte has extremely high ionic conductivity, and the technical effect is that it can reduce the hindrance of the edge coating to lithium ion transmission, reduce the interface impedance of the battery, and be beneficial to maintaining the good rate performance and capacity of the battery.

[0033] Further, the sulfide electrolyte includes, but is not limited to, at least one of Li6PS5X (X = Cl, Br, I), Li 10 GeP2S 12 , Li 3.2 5 Ge 0.2 5 P0S4, Li2S-P2S5-based (such as 70Li2S·30P2S5), or Li6PS5Cl 1-x O x , and derivatives thereof.

[0034] Another aspect of the present application also relates to a method for preparing the positive electrode tab, comprising the following steps: coating a slurry containing edge coating raw materials on at least one edge region of the tab on which the positive active material layer has been coated and drying.

[0035] The preparation method of the positive electrode sheet is a simple and easy-to-implement edge coating forming method. Through the steps of "first coating the main material and then coating the edge", the functional coating can be accurately constructed in the edge area, which is suitable for industrial production and can ensure that the shape and position of the edge coating are controllable.

[0036] In some specific embodiments, the preparation method of the positive electrode sheet comprises the following steps: 1. Add the binder to the solvent at a solid content of 5%, continuously stir at 100 rpm for 12 h until the binder is completely dissolved in the solvent to form a uniform and stable glue solution; add the oxide powder and sulfide electrolyte powder to the glue solution in sequence, and continuously stir at 3500 rpm for 3 h to form a uniform and stable slurry, and then continuously add the solvent until the viscosity of the slurry is adjusted to <50 mPs; 2. Put the glue solution of step 1 into an inkjet printer, and print on the edge area of the positive electrode sheet, with a spraying width of 1-3 mm and a thickness of 90%-110% of the positive electrode coating; then put the treated sheet into a forced air oven and bake at 80℃ for 30 min until the edge coating is in a tack-free state; finally, transfer the tack-free sheet into a 90℃ vacuum drying oven and bake for 5-12 h for further drying, to obtain the prepared positive electrode sheet.

[0037] Further, the solvent includes at least one of dimethylbenzene, anisole, cyclohexane, butyl butyrate or heptane, and derivatives thereof.

[0038] Further, the viscosity of the slurry containing the edge coating raw material is <50 mPs, including but not limited to any one of 1 mPs, 5 mPs, 10 mPs, 15 mPs, 20 mPs, 30 mPs, 40 mPs or 49 mPs, or a range value between any two of them. By limiting the viscosity of the edge coating slurry (<50 mPs), it is ensured that the slurry has good flowability and atomization characteristics, which is particularly suitable for advanced coating technologies such as high-precision inkjet printing. This can ensure that the edge coating has uniform thickness and clear boundaries, further improving the consistency of production and product quality.

[0039] Another aspect of the present application also relates to a solid-state battery comprising the positive electrode sheet or the positive electrode sheet prepared by the preparation method of the positive electrode sheet.

[0040] The solid-state battery containing the positive electrode sheet has higher safety performance and better cycle life, significantly reduces the risk of short circuit caused by edge burrs, and thus improves the reliability and market competitiveness of the entire battery product.

[0041] Further, as Figure 1As shown, the positive electrode sheet is die-cut into the same size as the negative electrode sheet, and the positive electrode sheet, electrolyte film, negative electrode sheet, etc. are sequentially stacked, and then the solid-state battery is formed through the processes of adhesive application, tab welding, assembly, top sealing, side sealing, isostatic pressing, and second sealing.

[0042] The embodiments of the present application will be described in detail below with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained by purchase.

[0043] Example 1 The positive electrode sheet provided in this example includes, in terms of mass fraction, the edge coating layer comprising: 85 parts of oxide, 13.5 parts of electrolyte, and 1.5 parts of binder; The binder is nitrile rubber, the solvent is butyl acetate, the oxide powder is aluminum oxide, the sulfide powder is Li6PS5Cl, and the thickness ratio of the positive electrode coating layer is 100%, and the width of the edge coating layer is 2 mm.

[0044] The preparation method of Example 10 is used.

[0045] Example 2 The positive electrode sheet provided in this example includes, in terms of mass fraction, the edge coating layer comprising: 80.5 parts of oxide, 13.5 parts of electrolyte, and 0.5 parts of binder; The binder is nitrile rubber, the solvent is butyl acetate, the oxide powder is aluminum oxide, the sulfide powder is Li6PS5Cl, and the thickness ratio of the positive electrode coating layer is 100%, and the width of the edge coating layer is 2 mm.

[0046] The preparation method of Example 10 is used.

[0047] Example 3 The positive electrode sheet provided in this example includes, in terms of mass fraction, the edge coating layer comprising: 85 parts of oxide, 13.5 parts of electrolyte, and 6.0 parts of binder; The binder is nitrile rubber, the solvent is butyl acetate, the oxide powder is aluminum oxide, the sulfide powder is Li6PS5Cl, and the thickness ratio of the positive electrode coating layer is 100%, and the width of the edge coating layer is 2 mm.

[0048] The preparation method of Example 10 is used.

[0049] Example 4 The positive electrode sheet provided in this example includes, in terms of mass fraction, the edge coating layer comprising: Oxide 70 parts, electrolyte 28.5 parts and binder 1.5 parts; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is alumina, the sulfide powder is Li6PS5Cl, the ratio of the thickness of the positive electrode coating to the thickness of the edge coating is 100%, and the width of the edge coating is 2 mm.

[0050] The preparation method of Example 10 is adopted.

[0051] Example 5 The positive electrode tab provided in this example includes, in terms of mass fraction: Oxide 95 parts, electrolyte 3.5 parts and binder 1.5 parts; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is alumina, the sulfide powder is Li6PS5Cl, the ratio of the thickness of the positive electrode coating to the thickness of the edge coating is 100%, and the width of the edge coating is 2 mm.

[0052] The preparation method of Example 10 is adopted.

[0053] Example 6 The positive electrode tab provided in this example includes, in terms of mass fraction: Oxide 85 parts, electrolyte 13.5 parts and binder 1.5 parts; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is alumina, the sulfide powder is Li6PS5Cl, the ratio of the thickness of the positive electrode coating to the thickness of the edge coating is 120%, and the width of the edge coating is 2 mm.

[0054] The preparation method of Example 10 is adopted.

[0055] Example 7 The positive electrode tab provided in this example includes, in terms of mass fraction: Oxide 85 parts, electrolyte 13.5 parts and binder 1.5 parts; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is alumina, the sulfide powder is Li6PS5Cl, the ratio of the thickness of the positive electrode coating to the thickness of the edge coating is 80%, and the width of the edge coating is 2 mm.

[0056] The preparation method of Example 10 is adopted.

[0057] Example 8 The positive electrode tab provided in this example includes, in terms of mass fraction: Oxide 85 parts, electrolyte 13.5 parts and binder 0.5-6 parts; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is aluminum oxide, the sulfide powder is Li6PS5Cl, the positive electrode coating thickness ratio is 100%, and the edge coating width is 0.5mm.

[0058] The preparation method of Example 10 is adopted.

[0059] Example 9 The edge coating of the positive electrode plate provided in the example comprises, in terms of mass fraction: 85 parts of oxide, 13.5 parts of electrolyte, and 1.5 parts of binder; The binder is nitrile rubber, the solvent is butyl butyrate, the oxide powder is aluminum oxide, the sulfide powder is Li6PS5Cl, the positive electrode coating thickness ratio is 100%, and the edge coating width is 4mm.

[0060] The preparation method of Example 10 is adopted.

[0061] Example 10 The preparation method of the positive electrode plate provided in the example comprises the following steps: 1. Edge coating slurry preparation: The binder is added to the solvent at a solid content of 5%, and continuously stirred at 100 rpm for 12 h until the binder is completely dissolved in the solvent to form a uniform and stable glue solution. The oxide powder and the sulfide electrolyte powder are sequentially added to the glue solution, and continuously stirred at 3500 rpm for 3 h to form a uniform and stable slurry, and then solvent is continuously added until the viscosity of the slurry is adjusted to <50 mPs.

[0062] 2. Inkjet printing of the edge coating: The glue solution described in step one is loaded into an inkjet printer and printed on the edge area of the positive electrode plate. The treated plate is placed in a forced air oven at 80°C and baked for 30 min until the edge coating is in a tack-free state. Finally, the tack-free plate is transferred to a 90°C vacuum drying oven and baked for 10 h for further drying to obtain the prepared positive electrode plate.

[0063] Comparative Example 1 A positive electrode plate without an edge coating is used for battery assembly and testing.

[0064] Experimental Example The positive electrode plates prepared in the examples and comparative examples are die-cut into plates of the same size as the negative electrode, and the positive electrode plate, electrolyte film, negative electrode plate, etc. are sequentially stacked, and then subjected to the processes of gluing, tab welding, assembly, top sealing, side sealing, isostatic pressing, and secondary sealing to form a solid-state battery, and the capacity, initial efficiency, cycle, rate, and other basic performance of the battery are tested.

[0065] Battery Test Method 1) Resistance test: ACR test was performed on each battery to be tested by using an alternating current resistance meter, and the alternating current resistance and corresponding voltage value of each battery to be tested were recorded, and the test temperature was 25°C; 2) Cycle performance test: 3 batteries to be tested were taken for capacity calibration. According to the actual capacity of the battery cell, the battery was subjected to cycle charge-discharge test, and the test procedure was: 1C constant current charging to 4.3V, 4.3V constant voltage charging to 0.05C, standing for 0.5h, constant current discharging to 2.75V, standing for 0.5h. The above procedure was cycled until the discharge capacity of the battery cell was reduced to below 80% of the calibrated capacity, the test temperature was 25°C, and the final capacity retention was the average value of the capacity retention of 3 batteries to be tested.

[0066] 3) Rate performance test: 3 batteries to be tested were taken for capacity calibration. According to the actual capacity of the battery cell, the battery was subjected to rate performance test. The test method was to use 0.2C, 0.33C, 0.5C, 1C, 2C, 3C current for continuous discharge. Before each discharge, 1C constant current charging to 4.2V was used, and then 4.2V constant voltage charging to 0.05C, the test temperature was 25°C, and the final capacity retention was the average value of the capacity retention of 3 batteries to be tested.

[0067] The test results are shown in Table 1 below.

[0068] Table 1

[0069] It can be seen from Comparative Examples 1-3 that when the amount of the binder added is >5%, there is a serious rebound after the edge coating is rolled, resulting in poor internal contact of the electrode, increased internal resistance and deteriorated performance. When the amount of the binder added is <1%, the edge coating is prone to falling off during the operation of the battery, losing the supporting effect on the internal part of the battery cell and resulting in deteriorated cycle performance. It can be seen from Comparative Examples 1, 4 and 5 that when the proportion of the oxide and the sulfide electrolyte is not in the optimal range, the electrode sheet is prone to serious edge curling and wavy edge after rolling due to the large difference in physical properties (flexibility, compression ratio, etc.) between the positive electrode coating, thus the overall performance of the battery is poor. It can be seen from Comparative Examples 1, 6 and 7 that when the thickness of the edge coating is more than 110% of the thickness of the positive electrode layer, the contact between the positive and negative electrodes is not tight due to the thick edge coating, the internal resistance of the battery is increased and the performance is deteriorated. When the thickness of the edge coating is less than 80% of the thickness of the positive electrode layer, the edge coating cannot provide good support to the battery cell due to the insufficient thickness, thus the performance is deteriorated seriously after long cycle. It can be seen from Comparative Examples 1, 8 and 9 that too narrow edge coating will result in deteriorated short-circuit prevention effect, thus short-circuit occurs after long cycle. Too wide edge coating will result in large difference between the positive and negative overhangs and large loss of active lithium during the cycle. It can be seen from Comparative Example 1 and Comparative Example 1 that when the electrode sheet does not have edge coating, the risk of short-circuit of the battery is extremely high. The risk of short-circuit of the battery is reduced and the cycle performance is good after the addition of the edge coating.

[0070] Although the present application has been illustrated and described with reference to specific embodiments, it is to be understood that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, and are not intended to limit the present application; ordinarily skilled in the art should understand: the technical solutions recorded in the above-mentioned embodiments can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, it means that all these replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A positive electrode plate, characterized in that, It includes a current collector and a positive electrode active material layer coated on the surface of the current collector, wherein at least one edge of the positive electrode active material layer is provided with a side coating; The edge coating comprises, by weight parts: 70-95 parts oxide, 2-30 parts electrolyte and 0.5-6 parts binder.

2. The positive electrode sheet according to claim 1, characterized in that, The edge coating comprises, by weight parts: 80-85 parts oxide, 10-18 parts electrolyte and 2-4 parts binder.

3. The positive electrode sheet according to claim 1, characterized in that, The width of the edge coating is 1~3mm.

4. The positive electrode sheet according to claim 1, characterized in that, The thickness of the edge coating is 90% to 110% of the thickness of the positive electrode active material layer.

5. The positive electrode sheet according to claim 1, characterized in that, The adhesive includes at least one of the following: nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene rubber, polyisoprene, ethylene-methyl acrylate copolymer, or hydrogenated styrene-isoprene-styrene block copolymer.

6. The positive electrode sheet according to claim 1, characterized in that, The oxide includes at least one of the following: aluminum oxide, silicon oxide, zirconium oxide, lithium titanium aluminum phosphate, lithium lanthanum zirconium tantalum oxide, or lithium lanthanum titanium oxide.

7. The positive electrode sheet according to claim 1, characterized in that, The electrolyte includes: sulfide electrolyte.

8. The method for preparing the positive electrode sheet according to any one of claims 1 to 7, characterized in that, Includes the following steps: The slurry containing the edge coating material is coated onto at least one edge region of the electrode sheet that has been coated with the positive electrode active material layer and then dried.

9. The method for preparing the positive electrode sheet according to claim 8, characterized in that, The viscosity of the slurry containing the edge coating material is <50 mPs.

10. A solid-state battery, characterized in that, The positive electrode sheet prepared by the method of any one of claims 1 to 7 or the positive electrode sheet prepared by claim 8 or 9 is included.

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