Composite positive electrode sheet, method for manufacturing composite positive electrode sheet, secondary battery, and electric device

Abstract

The application discloses a composite positive electrode sheet, a preparation method of the composite positive electrode sheet, a secondary battery and an electric device. The application adopts a printing coating mode, compared with a full coating mode, reduces the influence of a solid-state electrolyte layer on the energy density of a lithium ion battery, and improves the safety performance of the battery; the area and the interval of the solid-state electrolyte pattern are controllable, the influence on the charging and discharging performance of the battery is reduced, and thus the influence on the energy density and the cycle energy of the battery is reduced; meanwhile, the printing coating can increase the liquid retention capacity of the electrode sheet, effectively improves the cycle capacity of the battery cell, and thus the service life of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, and in particular to a composite positive electrode sheet, a preparation method of the composite positive electrode sheet, a secondary battery and an electric device. BACKGROUND

[0002] Ternary lithium ion batteries have become an indispensable energy storage method in mobile electronic devices, electric vehicles and energy storage systems due to their high energy density, long service life and good charging performance. However, with the wide application of lithium ion batteries, their safety problems have also attracted increasing attention. Lithium ion batteries may cause internal short circuit under excessive charging, physical damage or other abnormal conditions, which may further cause battery overheating, explosion or fire and other safety accidents.

[0003] In order to improve the safety performance of lithium ion batteries, existing technologies mainly focus on improving battery materials and structural design. For example, by using more stable and safer electrolyte materials, such as solid-state electrolyte, to replace traditional liquid electrolyte; or by improving the chemical composition of the positive and negative materials of the battery to improve the thermal stability of the battery.

[0004] Although the existing technologies have improved the safety performance of lithium ion batteries to some extent, there are still some problems and limitations. First, the use of solid-state electrolyte can improve the safety of the battery, but it will significantly reduce the energy density of the battery, affecting the performance and capacity of the battery. Second, improving battery materials and structural design can improve the safety of the battery, but it requires large-scale modification of existing battery production processes, which is costly and may affect the manufacturing efficiency of the battery. Therefore, how to further improve the safety performance of lithium ion batteries without significantly reducing the energy density of the battery is a problem to be solved in the current field. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0006] To this end, an embodiment of the present application proposes a composite positive electrode sheet, a preparation method of the composite positive electrode sheet, a secondary battery and an electric device.

[0007] In a first aspect, the present application proposes a composite positive electrode sheet, comprising:

[0008] a positive electrode sheet;

[0009] a solid-state electrolyte layer printed on the entire surface of the positive electrode sheet, the solid-state electrolyte layer comprising a plurality of spaced solid-state electrolyte patterns.

[0010] The application prints the solid electrolyte layer on the positive pole piece by pattern interval coating, so that the safety of the solid electrolyte is realized, the influence of the solid electrolyte layer on the energy density of the battery is reduced, the liquid retention capacity of the pole piece is increased, the thermal stability of the battery cell is effectively increased, and the safety performance of the battery is improved.

[0011] Further, the distance between two points on the solid electrolyte pattern is within 10 mu m, and the area of the surface corresponding to the solid electrolyte pattern on the positive pole piece is 1-80 mu m 2 .

[0012] The surface corresponding to the solid electrolyte pattern on the positive pole piece is the surface in contact with the solid electrolyte pattern on the positive pole piece. A suitable area can improve the safety of the solid-state battery, reduce the influence of the solid electrolyte on the energy density of the battery, enhance the liquid retention capacity of the pole piece, and improve the thermal stability of the battery cell; if the area is too large, the internal resistance of the battery will increase, thereby reducing the output power and energy density of the battery; if the area is too small, an effective ion conduction network cannot be formed, resulting in increased battery resistance and reduced battery performance.

[0013] The area of a single solid electrolyte pattern is 1-80 mu m 2 , and the distance between two points on the solid electrolyte pattern is within 10 mu m. The smaller the area of the solid electrolyte pattern and the smaller the distance, the larger the specific surface area of the overall pattern, and the more the seepage paths of the electrolyte, so that the liquid seepage is faster, and the liquid retention capacity is improved.

[0014] Further, the distance between the centers of two adjacent solid electrolyte patterns is 1-10 mu m.

[0015] The distance between the centers of two adjacent solid electrolyte patterns can be 1 mu m, 3 mu m, 5 mu m, 8 mu m, 10 mu m, or a value within a range composed of any two numerical values. A suitable distance between two adjacent solid electrolyte patterns reduces the influence of the solid electrolyte layer on the charge and discharge performance of the battery, thereby reducing the influence on the energy density and cycle capacity of the battery. If the distance between two adjacent solid electrolyte patterns is too large, the solid electrolyte layer cannot effectively cover the positive pole piece, thereby affecting the safety performance of the battery; if the distance is too small, the energy density of the battery and the liquid retention capacity of the pole piece are affected.

[0016] Further, the thickness of the solid electrolyte pattern is less than 10 mu m.

[0017] The thickness of the solid electrolyte pattern can be 1 mu m, 3 mu m, 5 mu m, 7 mu m, 9 mu m, 10 mu m, or a value within a range composed of any two numerical values.

[0018] A suitable solid electrolyte layer thickness can balance battery safety and performance. It can effectively isolate the positive and negative electrodes, reducing the risk of short circuits and thermal runaway, while ensuring the conductivity of ions and the smooth flow of charge. It can provide sufficient mechanical strength to prevent cracking or damage during battery manufacturing and use. It can reduce interface problems between the positive electrode and the solid electrolyte layer, improve charge transfer efficiency, and enhance battery performance. It can maintain the electrolyte retention capacity of the electrodes, prevent electrolyte leakage, and ensure battery performance and lifespan.

[0019] Excessive thickness of the solid electrolyte increases the battery's internal resistance, thereby reducing the battery's output power and energy density; it also reduces ion conductivity, resulting in slower charging and discharging speeds and longer charging times; it increases the battery's manufacturing cost; and it increases the battery's weight, thereby reducing the battery's energy density.

[0020] When the solid electrolyte layer is too thin, it cannot effectively isolate the positive and negative electrodes, increasing the risk of short circuits and thermal runaway, and reducing the safety performance of the battery; it also leads to a decrease in mechanical strength, making the battery more prone to cracking or damage during manufacturing and use; and it increases interface problems between the positive electrode and the solid electrolyte layer, resulting in poor charge transfer and reduced battery performance.

[0021] Furthermore, the solid electrolyte pattern is one or more of a circle, triangle, or square.

[0022] It is understandable that the shape of the solid electrolyte pattern can be regular or irregular. The shape of the solid electrolyte pattern is not limited and can be selected according to the specific working conditions.

[0023] Secondly, the present invention proposes a method for preparing the composite positive electrode sheet mentioned in the first aspect above, such as... Figure 1 As shown, it includes the following steps:

[0024] Prepare the positive electrode sheet;

[0025] Preparation of solid electrolyte slurry: After mixing solid electrolyte powder with binder, add solvent and stir evenly;

[0026] The solid electrolyte slurry is coated onto the positive electrode sheet using a printing process and then dried to obtain a composite positive electrode sheet.

[0027] The positive electrode can be a lithium nickel cobalt manganese oxide positive electrode, a lithium iron phosphate positive electrode, or other suitable positive electrode.

[0028] Furthermore, the drying temperature is 100–200℃, and the drying time is 1–10 h. After coating the solid electrolyte slurry onto the positive electrode sheet, it is placed in an oven to dry, thus obtaining the cured solid electrolyte layer.

[0029] Furthermore, the solid electrolyte includes an oxide solid electrolyte.

[0030] Oxide solid electrolytes possess high ionic conductivity and good stability, which can improve battery safety performance while minimizing their impact on battery energy density. Oxide solid electrolytes can be LATP, LLZO, LLTO, LLZTO, etc. It can also be understood that solid electrolytes can be sulfide solid electrolytes or polymer solid electrolytes.

[0031] Furthermore, the adhesive includes one or more of PVDF, PEO, PVA, PAA, and PMMA.

[0032] Furthermore, the solvent includes one or more of NMP, acetonitrile, acetone, and ethanol, and the mixture of solid electrolyte and binder is coated onto the positive electrode sheet using the solvent as a carrier.

[0033] Furthermore, the amount of binder added is 5% to 20% of the mass of the solid electrolyte powder.

[0034] An appropriate amount of binder can ensure good adhesion between the oxide solid electrolyte slurry and the electrode surface, preventing the coating from falling off during battery charging and discharging; it can form a uniform coating, which is beneficial for ion conduction, thereby improving battery performance; the oxide solid electrolyte itself has high thermal stability, and an appropriate amount of binder can further enhance the thermal stability of the coating and reduce the risk of thermal runaway.

[0035] When too little binder is added, the adhesion between the oxide solid electrolyte slurry and the electrode surface is insufficient, the coating is easy to fall off, affecting the safety and performance of the battery; the inability to form a uniform coating leads to a decrease in thermal stability and increases the risk of thermal runaway; the coating lacks sufficient mechanical strength and is prone to cracking during battery charging and discharging, affecting the long-term stability and safety of the coating.

[0036] Adding too much binder can thicken the coating, increase the battery's internal resistance, and thus reduce battery performance; it can also hinder ion conduction, leading to a decrease in battery charge and discharge efficiency; increase battery production costs; and make the coating more brittle, making it prone to cracking during battery charge and discharge, thus affecting the coating's long-term stability and safety.

[0037] Furthermore, the particle size of the solid electrolyte powder is 0.2–0.8 μm.

[0038] A suitable solid electrolyte powder particle size can provide more ion transport channels, thereby improving the ion conductivity of the coating, which helps reduce the internal impedance of the battery and improve the charge and discharge efficiency of the battery; it can form a denser coating, thereby enhancing the mechanical strength of the coating and helping to resist physical stresses that the battery may encounter during use, such as bending and impact; it can better contact with electrode materials to form a stable interface, which helps to reduce side reactions at the interface and improve the cycle stability of the battery.

[0039] When the particle size of solid electrolyte powder is too large, it will cause more grain boundaries and defects to form inside the coating, thereby reducing the ionic conductivity of the coating, increasing the internal impedance of the battery, and reducing the charge and discharge efficiency of the battery. The coating formed by excessively large particles may not be dense enough and has low mechanical strength, making the coating easy to crack under physical stress, thus affecting the safety and life of the battery. It will also lead to poor contact with the electrode material, resulting in increased interfacial impedance, which in turn increases the internal impedance of the battery, reducing the charge and discharge efficiency and cycle stability of the battery.

[0040] When the particle size of solid electrolyte powder is too small, the resulting coating may not be dense enough and has low mechanical strength, making it prone to cracking under physical stress, thus affecting the safety and lifespan of the battery. It also results in poor contact with the electrode material, leading to increased interfacial impedance and increased internal impedance of the battery, reducing charge-discharge efficiency and cycle stability. Furthermore, it requires more preparation steps and equipment, thus increasing production costs. In addition, excessively small particles are more likely to agglomerate during storage and transportation, thereby affecting its performance.

[0041] Thirdly, the present invention proposes a secondary battery comprising the composite positive electrode sheet proposed in the first aspect or the composite positive electrode sheet prepared by the method proposed in the second aspect.

[0042] Fourthly, the present invention proposes an electrical device comprising the secondary battery described in the third aspect above.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] This invention improves battery safety by coating a solid electrolyte layer onto the positive electrode sheet, thereby enhancing the thermal stability of the cell and improving the battery's thermal stability while maintaining the safety of the solid electrolyte.

[0045] This invention employs a printed coating method, which, compared to full coating, reduces the impact of the solid electrolyte layer on the energy density of lithium-ion batteries and improves battery safety performance. The area and spacing of the solid electrolyte pattern are controllable, reducing the impact on battery charge and discharge performance, thereby lowering the impact on battery energy density and cycle energy. At the same time, printed coating can increase the electrolyte retention capacity of the electrode sheets, effectively improving the cell cycle capacity and thus extending battery life.

[0046] This invention uses a printed coating method to reduce the amount of solid electrolyte coated, maintaining the battery's portability. At the same time, the printed coating method is easier to implement than the full coating method, and the required materials and processes are simpler, thereby reducing manufacturing costs. Attached Figure Description

[0047] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0048] Figure 1 This is a flowchart of the preparation method of the composite positive electrode sheet of the present invention. Detailed Implementation

[0049] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0050] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0051] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0052] Example 1

[0053] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0054] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, with a diameter of 2μm, a spacing of 5μm between the dots, and a thickness of 10μm.

[0055] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0056] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0057] Example 2

[0058] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0059] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, the diameter of the dots is 2μm, the spacing between the dots is 5μm, and the thickness is 4μm.

[0060] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0061] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0062] Example 3

[0063] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0064] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, with a diameter of 5μm, a spacing of 5μm between the dots, and a thickness of 10μm.

[0065] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0066] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0067] Example 4

[0068] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0069] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, with a diameter of 5μm, a spacing of 8μm between the dots, and a thickness of 10μm.

[0070] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0071] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0072] Example 5

[0073] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0074] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, with a diameter of 10 μm, a spacing of 10 μm between the dots, and a thickness of 10 μm.

[0075] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0076] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0077] Example 6

[0078] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0079] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is square with a side length of 3μm, the spacing between the dot patterns is 7μm, and the thickness is 6μm.

[0080] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0081] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0082] Example 7

[0083] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0084] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is an equilateral triangle with a side length of 8μm, a spacing of 9μm between the dot patterns, and a thickness of 5μm.

[0085] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0086] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0087] Comparative Example 1

[0088] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0089] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, with a diameter of 2μm, a spacing of 15μm between the dots, and a thickness of 4μm.

[0090] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0091] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0092] Comparative Example 2

[0093] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0094] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and print and coat the solid electrolyte slurry onto the positive electrode sheet. The solid electrolyte pattern is in the form of dots, the diameter of the dots is 2μm, the spacing between the dots is 5μm, and the thickness is 15μm.

[0095] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0096] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0097] Comparative Example 3

[0098] Mix 100g of solid electrolyte powder with 5ml of PVDF binder, add 200ml of NMP, and stir until homogeneous to obtain solid electrolyte slurry.

[0099] Prepare a lithium nickel cobalt manganese oxide positive electrode sheet, and uniformly coat the surface of the positive electrode sheet with a solid electrolyte slurry, the thickness of which is 10μm.

[0100] The positive electrode sheet coated with the solid electrolyte layer is placed in an oven and cured at 120°C for 5 hours to obtain the cured solid electrolyte layer.

[0101] The positive electrode sheet coated with a solid electrolyte layer is assembled into a lithium battery, and the specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0102] Comparative Example 4

[0103] Prepare lithium nickel cobalt manganese oxide positive electrode sheets and assemble them into a lithium battery. The specific operation steps are carried out in accordance with the conventional lithium battery manufacturing process.

[0104] The manufacturing process of lithium batteries includes the following steps:

[0105] Positive electrode sheet: The positive electrode slurry consists of NCM, SP, and PVDF in a mass ratio of 96:2:2. The positive electrode slurry is coated onto the current collector, and the areal density of the coated positive electrode slurry is 19.8 mg / cm³. 2 After roller pressing, the compacted density is 3.5 g / cm³. 3 The electrode sheet is obtained by die-cutting and has a length and width of 90×59mm; where NCM refers to nickel-cobalt-manganese ternary cathode material, SP refers to conductive carbon black, and PVDF refers to polyvinylidene fluoride.

[0106] Negative electrode sheet: The negative electrode slurry comprises graphite, conductive agent (SP), binder (SBR), and thickener (CMC) in a mass ratio of 95.5:1:2:1.5; the negative electrode slurry is coated onto the current collector, with a coating surface density of 11.5 mg / cm³. 2 The negative electrode sheet with a length and width of 93×62mm is obtained by rolling and die cutting.

[0107] Diaphragm: The diaphragm is a PP / PE diaphragm;

[0108] The positive electrode / separator / negative electrode is stacked, and then packaged in a soft pack, followed by electrolyte injection and sealing to obtain a 5Ah battery.

[0109] The battery needle penetration test method is as follows: Use a steel needle with a diameter of 5mm to penetrate the battery at a speed of 25mm / s and leave it inside the battery for 60 minutes. Observe whether there is any fire or explosion. If there is no fire or explosion, the test is passed.

[0110] The test method for battery overcharge test is as follows: The initial voltage of the battery is 4.2V. Charge it with a constant current of 1C to 6.3V or charge it for 1 hour and then stop charging. Observe whether there is any fire or explosion. If there is no fire or explosion, the test is passed.

[0111] Battery energy density testing methods:

[0112] ① Discharge at a constant current of 1 / 3C until the termination voltage is reached, then let stand for 30 minutes;

[0113] ② Charge at a constant current of 1 / 3C until the termination voltage is reached, then switch to constant voltage charging until the charging current drops to 0.05C and stop charging. Let stand for 30 minutes.

[0114] ③ Discharge at a constant current of 1 / 3C until the termination voltage is reached, let stand for 30 minutes, and record the discharge capacity and average discharge voltage.

[0115] ④ Calculate battery energy density = battery capacity * average discharge voltage / battery weight.

[0116] Battery cycle performance testing methods:

[0117] ① Discharge at a constant current of 1C until the termination voltage is reached, then let stand for 30 minutes;

[0118] ② Charge at a constant current of 1C until the termination voltage is reached, then switch to constant voltage charging until the charging current drops to 0.05C and stop charging. Let stand for 30 minutes.

[0119] ③ Discharge at a constant current of 1C until the termination voltage is reached, let stand for 30 minutes, and record the discharge capacity;

[0120] ④ Repeat steps ② to ③ for 500 consecutive cycles, and use the ratio of the discharge capacity after 500 cycles to the initial discharge capacity as the discharge capacity retention rate.

[0121] The lithium-ion batteries prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to energy density, cycle performance, nail penetration and overcharge tests. Three batteries were tested in each group of tests, and the energy density and discharge capacity retention rate were the average values ​​of the three batteries. The test results are shown in Table 1.

[0122] Table 1:

[0123]

[0124]

[0125] Comparing Examples 1-7 with Comparative Examples 3 and 4, it can be seen that the safety performance of the battery is improved after coating the positive electrode sheet with a solid electrolyte layer. Compared with full-coverage coating, the energy density and cycle performance of the printed coating battery are significantly improved. At the same time, the needle penetration and overcharge test results show that the safety performance of the printed coating battery is consistent with that of the full-coverage coating.

[0126] Comparing Example 2 and Comparative Example 1, it can be seen that when the spacing of the dot pattern in the coating layer is too large, the energy density and cycle performance of the battery are improved, but the safety performance is reduced.

[0127] Comparing Example 2 and Comparative Example 2, it can be seen that when the thickness of the dot pattern in the coating layer is too large, the energy density and cycle performance of the battery decrease, while the safety performance remains the same.

[0128] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0129] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0130] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A composite positive electrode, characterized in that, include: Positive electrode sheet; A solid electrolyte layer is printed onto the entire surface of the positive electrode sheet. The solid electrolyte layer includes multiple spaced solid electrolyte patterns. The distance between two points on the solid electrolyte pattern is within 10 μm, and the area of ​​the side of the solid electrolyte pattern corresponding to the positive electrode sheet is 1~80 μm². 2 The distance between the centers of two adjacent solid electrolyte patterns is 1~10μm. The method for preparing the composite positive electrode includes the following steps: Prepare the positive electrode sheet; Preparation of solid electrolyte slurry: After mixing solid electrolyte powder with binder, add solvent and stir evenly; The solid electrolyte slurry is coated onto the positive electrode sheet using a printing process and then dried to obtain a composite positive electrode sheet.

2. The composite positive electrode sheet as described in claim 1, characterized in that, The thickness of the solid electrolyte pattern is less than 10 μm.

3. The composite positive electrode sheet as described in claim 1, characterized in that, The solid electrolyte pattern is one or more of a circle, triangle, or square.

4. The composite positive electrode sheet as described in claim 1, characterized in that, The solid electrolyte includes an oxide solid electrolyte; And / or, the adhesive comprises one or more of PVDF, PEO, PVA, PAA, and PMMA; And / or, the solvent includes one or more of NMP, acetonitrile, acetone, and ethanol.

5. The composite positive electrode sheet as described in claim 1, characterized in that, The amount of binder added is 5% to 20% of the mass of the solid electrolyte powder.

6. The composite positive electrode sheet as described in claim 1, characterized in that, The particle size of the solid electrolyte powder is 0.2~0.8μm.

7. A secondary battery, characterized in that, Includes the composite positive electrode sheet as described in any one of claims 1 to 6.

8. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 7.

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