Composite positive pole piece and diaphragm-free battery cell

Abstract

The utility model belongs to the technical field of batteries, and discloses a composite positive pole piece and a diaphragm-free battery cell. The composite positive pole piece comprises a positive pole piece and an insulating protective layer, the positive pole piece comprises a main body part and an edge part which are connected with each other, the edge part is located at the circumferential edge of the main body part, and the maximum thickness of the edge part is not greater than that of the main body part; the insulation protection layer wraps the edge part, and the surface of the insulation protection layer is not higher than the surface of the main body part. The thickness of the edge part is smaller than the thickness of the main body part, so that the peripheral thickness of the composite positive pole piece can be prevented from being increased after the insulation protection layer is protected, and on the basis of realizing diaphragm-free battery cell preparation, the battery cell is prevented from being damaged during pressurization due to too high peripheral thickness of the battery cell; and effective contact between the composite positive pole piece and the negative pole piece is ensured, so that the cycle performance of the battery cell is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a composite positive electrode sheet and a diaphragm-free battery cell. Background Art

[0002] In the process of thermal runaway of traditional liquid cells, the positive and negative electrodes are directly short-circuited after the diaphragm shrinks, generating a large amount of heat instantly, causing the cell to catch fire and explode. However, by replacing the diaphragm with a solid electrolyte layer, a diaphragm-free cell can be obtained. The diaphragm-free cell eliminates the diaphragm component, and the solid electrolyte layer has extremely high heat resistance, avoiding the safety hazards caused by the thermal performance weaknesses of the diaphragm, improving the intrinsic thermal safety performance of the cell as a whole, and reducing the production cost of the cell.

[0003] The key problem in the preparation process of diaphragm-free cells is the metal burrs, flanges and other defects generated after the die-cutting of the electrode pieces. The metal burrs, flanges and other defects on the edge of the positive electrode piece will directly contact the negative electrode piece, thereby causing the risk of short circuits between the positive and negative electrode pieces, reducing the qualified rate of the battery and seriously affecting the safety performance of the cell. Therefore, it is necessary to protect the edge of the positive electrode piece to better avoid short circuits inside the battery.

[0004] In the prior art, the method for protecting the edge of the positive electrode is to set an insulating protective layer around it after die-cutting to prevent short circuits caused by contact between the positive and negative electrodes. However, after adding the insulating protective layer, the thickness around the battery cell is too high, which will affect the performance of the battery. For example, when the battery is pressurized, it will cause excessive pressure and damage the battery; it will affect the effective contact between the positive and negative electrodes of the battery cell, and reduce the cycle performance of the battery cell. Utility Model Content

[0005] The utility model aims to provide a composite positive electrode plate and a diaphragm-free battery cell, which can solve the problem that the insulating protective layer causes the battery cell periphery to be too thick and affects the battery performance.

[0006] To achieve this purpose, the utility model adopts the following technical solutions:

[0007] A composite positive electrode sheet, comprising:

[0008] A positive electrode sheet, the positive electrode sheet comprising a main body portion and an edge portion connected to each other, the edge portion being located at a circumferential edge of the main body portion, and a maximum thickness of the edge portion being no greater than a maximum thickness of the main body portion;

[0009] An insulating protective layer is coated on the edge portion, and a surface of the insulating protective layer is not higher than a surface of the main body portion.

[0010] As an optional solution of the above-mentioned composite positive electrode plate, the positive electrode plate includes:

[0011] Positive electrode current collector;

[0012] A positive electrode coating is covered on the surface of the positive electrode collector, wherein the positive electrode coating includes a first coating area and a second coating area arranged around the edge of the first coating area, the thickness of the first coating area is greater than the thickness of the second coating area, and the edge portion is formed at the second coating area.

[0013] As an optional solution of the above composite positive electrode sheet, the thickness of the second coating area gradually decreases in a direction away from the edge of the positive electrode current collector.

[0014] As an optional solution of the above-mentioned composite positive electrode plate, the positive electrode plate includes:

[0015] A positive electrode current collector, wherein the surface of the positive electrode current collector comprises a coating area and a non-coating area arranged around the circumferential edge of the coating area;

[0016] The positive electrode coating covers the coating area and exposes the non-coating area, and the non-coating area forms the edge portion.

[0017] As an optional solution of the above-mentioned composite positive electrode sheet, the positive electrode sheet also includes a solid electrolyte layer, the solid electrolyte layer has a uniform thickness and covers the positive electrode coating.

[0018] As an optional solution of the above-mentioned composite positive electrode plate, the thickness of the positive electrode solid electrolyte layer is 1 μm-50 μm.

[0019] As an optional solution for the above-mentioned composite positive electrode sheet, along the direction from the edge of the positive electrode sheet toward the center of the positive electrode sheet, the size of the edge portion covered by the insulating protection layer is 0.5mm-1mm.

[0020] As an optional solution for the above-mentioned composite positive electrode sheet, the insulating protection layer extends to the outside of the edge of the positive electrode sheet.

[0021] As an optional solution for the above-mentioned composite positive electrode plate, the insulating protection layer extends to the outside of the edge of the positive electrode plate by a size of 0.5 mm-1 mm.

[0022] As an optional solution of the above-mentioned composite positive electrode sheet, the positive electrode sheet further includes a positive electrode ear connected to the edge portion, and the insulating protection layer extends from the edge portion to cover a portion of the positive electrode ear.

[0023] As an optional solution of the above-mentioned composite positive electrode plate, along the extension direction of the positive electrode ear, the size of the positive electrode ear covered by the insulating protection layer is 1.5mm-3mm.

[0024] As an optional solution of the above-mentioned composite positive electrode plate, the insulating protective layer is a heat-resistant tape, a heat-resistant polymer layer or a ceramic glue coating;

[0025] And / or, the thickness of the insulating protective layer is 5 μm-50 μm;

[0026] And / or, the insulating protective layer is bonded and fixed to the positive electrode sheet.

[0027] As an optional solution of the above-mentioned composite positive electrode sheet, the edge portion includes a first surface and a second surface arranged opposite to each other, and the first surface and the second surface are both covered with the insulating protective layer.

[0028] A diaphragm-free battery cell comprises stacked negative electrode sheets and the above-mentioned composite positive electrode sheet.

[0029] As an optional solution for the above-mentioned membrane-free battery cell, the negative electrode plate includes a negative electrode collector and a negative electrode coating covering the negative electrode collector, and the projection of the negative electrode coating on the composite positive electrode plate is located within the range surrounded by the insulating protective layer.

[0030] Beneficial effects of the utility model:

[0031] In the composite positive electrode plate provided by the utility model, by setting the thickness of the edge portion to be smaller than the thickness of the main portion, it is possible to avoid an increase in the peripheral thickness of the composite positive electrode plate after protecting the insulating protective layer. On the basis of realizing the preparation of a diaphragm-free battery cell, it is possible to avoid damage to the battery cell during pressurization due to excessive thickness around the battery cell, which is beneficial to ensuring effective contact between the composite positive electrode plate and the negative electrode plate, thereby ensuring the cycle performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a cross-sectional view of the first type of diaphragm-free battery cell provided by the utility model;

[0033] Figure 2 This is a schematic structural diagram of the first composite positive electrode sheet provided by the utility model;

[0034] Figure 3 This is a schematic diagram of the structure of the first composite positive electrode sheet provided by the utility model after the plate is coated with a positive electrode coating during the preparation process;

[0035] Figure 4 This is a schematic diagram of the structure of the first composite positive electrode sheet provided by the utility model after the plate is coated with a positive electrode solid electrolyte layer during the preparation process;

[0036] Figure 5 This is a schematic diagram of the structure of the second composite positive electrode sheet provided by the utility model;

[0037] Figure 6 It is a cross-sectional view of a second type of diaphragm-free battery cell provided by the utility model.

[0038] In the figure:

[0039] 10. Composite positive electrode sheet; 11. Positive electrode current collector; 111. Non-coating area; 12. Positive electrode coating; 121. First coating area; 122. Second coating area; 14. Positive electrode solid electrolyte layer; 15. Positive electrode ear; 16. Insulating protective layer; 20. Negative electrode sheet; 21. Negative electrode current collector; 22. Negative electrode coating; 23. Negative electrode solid electrolyte layer; 24. Negative electrode ear. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0041] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] In the description of this embodiment, the terms "upper", "lower", "right", etc., are based on the directions or positions shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0044] This embodiment provides a membrane-free battery cell, such as Figure 1 As shown, it includes a stacked negative electrode sheet 20 and a composite positive electrode sheet 10, the negative electrode sheet 20 includes a negative solid electrolyte layer 23, and the composite positive electrode sheet 10 includes a positive solid electrolyte layer 14. When the negative electrode sheet 20 and the composite positive electrode sheet 10 are stacked, the negative solid electrolyte layer 23 and the positive solid electrolyte layer 14 are in contact, so as to replace the diaphragm in the traditional battery cell. The solid electrolyte layer has extremely high heat resistance, can avoid the safety hazard caused by the thermal shrinkage of the diaphragm, improve the thermal safety performance of the battery cell, and can reduce the cost of the battery cell.

[0045] Optionally, the negative electrode solid electrolyte layer 23 and the positive electrode solid electrolyte layer 14 may be organic solid electrolyte layers, inorganic electrolyte layers, or composite solid electrolyte layers formed by a composite of an organic electrolyte and an inorganic electrolyte.

[0046] like Figure 1 As shown, both the negative electrode sheet 20 and the composite positive electrode sheet 10 include a current collector and an electrode coating covering the current collector, and the area where the electrode coating is located is the material area of ​​the electrode sheet. For the convenience of introduction, the current collector in the negative electrode sheet 20 is the negative electrode current collector 21, and the electrode coating is the negative electrode coating 22; the current collector of the composite positive electrode sheet 10 is the positive electrode current collector 11, and the electrode coating is the positive electrode coating 12.

[0047] In order to ensure that the corresponding surface of the composite positive electrode sheet 10 has the negative electrode coating 22 to accept lithium ions and prevent the formation of lithium dendrites, in the membrane-free battery cell, the projection of the negative electrode coating 22 on the composite positive electrode sheet 10 must exceed the area where the positive electrode coating 12 is located, resulting in the size of the negative electrode collector 21 generally being larger than the size of the positive electrode collector 11.

[0048] The positive current collector is formed by die-cutting, and defects such as metal burrs and flanges will appear on the edge after die-cutting. Since the positive electrode coating 12 will be fully covered by the negative electrode sheet 20, the metal burrs, flanges and other defects on the edge of the positive current collector 11 will directly contact the negative electrode sheet 20, thereby causing the risk of short circuit between the composite positive electrode sheet 10 and the negative electrode sheet 20, reducing the qualified rate of the diaphragm-free battery cell, and seriously affecting the safety performance of the diaphragm-free battery cell.

[0049] The existing battery cell adds an insulating protective layer on the edge of the positive electrode plate. Although it can isolate metal burrs, flange defects and other defects from contacting the negative electrode plate, it will increase the thickness of the edge of the positive electrode plate, thereby affecting the performance of the diaphragm-free battery cell. For example, in the close contact between the composite positive electrode plate 10 and the negative electrode plate 20, the effective contact area between the composite positive electrode plate 10 and the negative electrode plate 20 will be reduced, resulting in a decrease in the cycle performance of the battery cell.

[0050] To solve the above problems, the composite positive electrode sheet 10 includes a positive electrode sheet and an insulating protective layer 16. The positive electrode sheet includes a positive electrode collector 11 and a positive electrode coating 12. The positive electrode sheet includes a main body and an edge portion that are connected to each other. The edge portion is located at the circumferential edge of the main body, and the maximum thickness of the edge portion is not greater than the maximum thickness of the main body; the insulating protective layer 16 is coated on the edge portion, and the surface of the insulating protective layer 16 is not higher than the surface of the main body.

[0051] In this embodiment, the insulating protective layer 16 is coated on the edge portion to protect the edge of the positive electrode sheet and prevent metal burrs, flange defects and other defects on the edge of the positive electrode sheet from directly contacting the negative electrode sheet 20; by setting the maximum thickness of the edge portion to be no greater than the maximum thickness of the main body, a coating space can be provided for the insulating protective layer 16, so that after adding the insulating protective layer 16, the surface of the insulating protective layer 16 is no higher than the surface of the main body, thereby ensuring the planar contact area of ​​the composite positive electrode sheet 10 and the negative electrode sheet 20, thereby ensuring the cycle performance of the battery cell.

[0052] Optionally, the insulating protection layer 16 and the positive electrode sheet can be bonded and fixed, which is convenient to fix, has good reliability, and can reduce the impact on the thickness of the composite positive electrode sheet 10 .

[0053] In this embodiment, the insulating protective layer 16 is a heat-resistant tape, which has good heat resistance and low cost. It can be adhered to the edge according to its own characteristics to achieve bonding and fixing of the insulating protective layer 16 and the positive electrode sheet, which is easy to operate.

[0054] In some embodiments, the insulating protective layer 16 may be a heat-resistant polymer layer or a ceramic glue coating, which can also isolate metal burrs, flange defects and the like, and has improved heat resistance, thereby ensuring the safety of the use of the diaphragm-free battery cell.

[0055] Optionally, the thickness of the insulating protective layer 16 can be 5 μm-50 μm, so as to prevent the surface of the insulating protective layer 16 from being higher than the surface of the main body while ensuring the protection effect on defects such as metal burrs and flanges. Exemplarily, typical but non-limiting data of the thickness of the insulating protective layer 16 are as follows: 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm.

[0056] In this embodiment, the thickness difference between the edge and the main body can be formed by a coating process. Specifically, the thickness of the edge of the positive electrode coating 12 is reduced so that the thickness of the edge of the positive electrode sheet is smaller than the thickness of the main body.

[0057] refer to Figure 1As shown, the positive electrode coating 12 includes a first coating area 121 and a second coating area 122 arranged around the edge of the first coating area 121. The thickness of the first coating area 121 is greater than the thickness of the second coating area 122. The second coating area 122 forms an edge portion, and the first coating area 121 forms a main body portion. By adjusting the coating process parameters when coating the positive electrode coating 12, the height difference between the edge portion and the main body portion is formed, and no additional process is required, which is conducive to reducing costs and improving the processing efficiency of the composite positive electrode sheet 10.

[0058] In this embodiment, the maximum thickness of the second coating area 122 is equal to the maximum thickness of the first coating area 121 , and the thickness of the second coating area 122 gradually decreases in a direction away from the edge of the positive electrode current collector 11 to provide space for the insulating protection layer 16 .

[0059] The positive electrode sheet also includes a positive electrode solid electrolyte layer 14, which covers the positive electrode coating 12. In other words, the insulating protective layer 16 is coated on the outside of the positive electrode solid electrolyte layer 14. This arrangement facilitates rolling after the solid electrolyte is introduced to increase the adhesion of the positive electrode solid electrolyte layer 14, thereby ensuring the cycle performance of the membrane-free battery cell.

[0060] In this embodiment, the thickness of the positive electrode solid electrolyte layer 14 is uniform, so as to avoid the different thicknesses of the positive electrode solid electrolyte layer 14 affecting the thickness relationship between the edge portion and the main portion.

[0061] Optionally, the thickness of the positive electrode solid electrolyte layer 14 may be 1 μm-50 μm. Exemplarily, typical but non-limiting data of the thickness of the positive electrode solid electrolyte layer 14 are as follows: 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm.

[0062] In order to improve the covering effect of the insulating protective layer 16 on the metal burrs, flanges and other defects at the edge of the positive electrode sheet, the size of the edge covered by the insulating protective layer 16 along the edge of the positive electrode sheet toward the center of the positive electrode sheet is L2, and L2 is 0.5mm-1mm. Within this range, the insulating protective layer 16 can better cover defects such as metal burrs and flanges, and prevent metal burrs, flanges and other defects from contacting the negative electrode sheet 20, thereby preventing the short circuit of the diaphragm-free battery cell.

[0063] Illustratively, typical non-limiting values ​​of L2 are 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm.

[0064] In this embodiment, the shape of the positive electrode sheet is roughly rectangular, and the insulating protective layer 16 covers the four side edges of the positive electrode sheet. The width of each side edge of the positive electrode sheet covered by the insulating protective layer 16 can be equal or unequal, as long as it can cover the position with defects such as metal burrs and flanges.

[0065] Since the size of the negative electrode sheet 20 is larger than that of the composite positive electrode sheet 10 , in order to prevent the positive electrode sheet from directly contacting the material area of ​​the negative electrode sheet 20 , the insulating protective layer 16 extends to the outside of the edge of the positive electrode sheet to completely cover the edge of the positive electrode sheet and avoid contact with the negative electrode sheet 20 .

[0066] In this embodiment, the front and back sides of the positive current collector 11 are provided with a positive electrode coating 12 and a positive solid electrolyte layer 14, and the edge portion includes a first surface and a second surface arranged opposite to each other, and the first surface and the second surface are both covered with an insulating protective layer 16, so as to avoid short circuit between the composite positive electrode sheet 10 and the negative electrode sheet 20 adjacent to the two sides when the composite positive electrode sheet 10 and the negative electrode sheet 20 are stacked in sequence.

[0067] The portions of the insulating protective layers 16 on both sides that extend beyond the edge of the positive electrode sheet are tightly fitted to fully wrap the surface of the edge portion to improve the insulation effect.

[0068] like Figure 1 As shown, the dimension of the insulating protective layer 16 extending to the outer side of the edge of the positive electrode sheet is L3, and L3 is 0.5mm-1mm to improve the insulation effect on the edge. Exemplarily, the typical non-limiting value of L3 is 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm.

[0069] In this embodiment, the projection of the negative electrode coating 22 on the composite positive electrode sheet 10 is located within the range surrounded by the insulating protective layer 16, which is beneficial to protect the edge of the positive electrode sheet from directly contacting the material area of ​​the negative electrode sheet 20 and causing a short circuit, thereby improving the safety performance of the membrane-free battery cell.

[0070] Combination Figure 1 and Figure 2 As shown, the positive electrode sheet further includes a positive electrode tab 15 connected to the edge portion. Specifically, the positive electrode tab 15 is formed by extending the positive electrode current collector 11, that is, the positive electrode tab 15 and the positive electrode current collector 11 are integrally formed.

[0071] Since the size of the negative electrode plate 20 is larger than that of the composite positive electrode plate 10, in order to prevent the positive electrode ear 15 from contacting the material area of ​​the negative electrode plate 20, the insulating protection layer 16 extends from the edge to cover part of the positive electrode ear 15, so as to provide insulation protection for the end of the positive electrode ear 15 connected to the positive electrode collector 11, and prevent it from contacting the material area of ​​the negative electrode plate 20, thereby preventing the composite positive electrode plate 10 and the negative electrode plate 20 from short circuiting.

[0072] like Figure 4 As shown, along the extension direction of the positive electrode ear 15, the insulating protective layer 16 covers the positive electrode ear 15 with a dimension L4, and L4 is 1.5 mm-3 mm. Within this dimension range, on the one hand, the positive electrode ear 15 can be prevented from contacting the material area of ​​the negative electrode plate 20, and on the other hand, the portion of the positive electrode ear 15 extending out of the insulating protective layer 16 can be ensured to have a sufficient dimension.

[0073] Exemplarily, typical non-limiting values ​​for L4 are 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm or 3 mm.

[0074] like Figure 2 As shown, in this embodiment, the insulating protective layer 16 is only partially extended at the position corresponding to the positive ear 15, so that the insulating protective layer 16 can extend to cover the positive ear 15. Specifically, the insulating protective layer 16 includes four long insulating parts connected end to end in sequence, wherein the widths of the three insulating parts are the same and are L1, and L1 is the sum of L2 and L3, that is, the width of the edge covered by the three insulating parts is L2, and the width extending to the outside of the positive electrode sheet is L3. The width of the other insulating part is divided into two parts, one part is relatively narrow and is L1, and the other part is larger and extends to the positive ear 15, and the width of this part is the sum of L1 and L4.

[0075] The steps for preparing the composite positive electrode sheet 10 provided in this embodiment are as follows:

[0076] like Figure 3 As shown, the positive electrode coating 12 is coated on the current collector plate at intervals by intermittent coating, wherein the positive electrode coating 12 includes a first coating area 121 located in the middle and a second coating area 122 surrounding the first coating area 121, and the thickness of the second coating area 122 gradually decreases in the direction away from the first coating area 121 to form a thinning area.

[0077] like Figure 4 As shown, the solid electrolyte is introduced onto the current collector plate and covered onto the positive electrode coating 12. After the solid electrolyte is dried, it is rolled to form a positive electrode solid electrolyte layer 14 of uniform thickness.

[0078] The current collector plate is die-cut to obtain a positive electrode sheet; an insulating protective layer 16 is provided at the edge of the positive electrode sheet, and the insulating protective layer 16 can be attached to the front and back of the positive electrode sheet by a glue sticking machine, and then the excess tape is cut to obtain a composite positive electrode sheet 10.

[0079] In some embodiments, Figure 5 As shown, the surface of the positive electrode current collector 11 includes a coating area and a non-coating area 111 arranged around the circumferential edge of the coating area; the positive electrode coating 12 covers the coating area and exposes the non-coating area 111, and the non-coating area 111 forms an edge portion. By providing the non-coating area 111, the surface of the positive electrode sheet can have a height difference, so as to provide space for the insulating protective layer 16, and ensure that the surface of the insulating protective layer 16 is not higher than the surface height of the positive electrode sheet.

[0080] like Figure 6 As shown, when the composite positive electrode sheet 10 and the negative electrode sheet 20 are stacked, the insulating protective layer 16 can be spaced apart from the negative electrode sheet 20 , that is, the thickness of the insulating protective layer 16 is less than the sum of the thicknesses of the positive electrode coating 12 and the positive solid electrolyte layer 14 .

[0081] Combination Figure 1 and Figure 6 As shown, the negative electrode plate 20 includes a negative electrode collector 21 , a negative electrode coating 22 covering the front and back sides of the negative electrode collector 21 , and a negative electrode solid electrolyte layer 23 covering the negative electrode coating 22 . The negative electrode collector 21 extends to form a negative electrode ear 24 .

[0082] In some embodiments, the negative electrode plate 20 may not be provided with the negative electrode solid electrolyte layer 23 , that is, the negative electrode plate 20 only includes the negative electrode current collector 21 and the negative electrode coating 22 .

[0083] In some embodiments, the negative electrode plate 20 may be a graphite negative electrode, a silicon-carbon negative electrode, or a lithium metal negative electrode.

[0084] Embodiment 1

[0085] In the membrane-free battery cell provided in this embodiment, reference Figure 1 As shown, when preparing the composite positive electrode sheet 10, an intermittent coating method is adopted to form a positive electrode coating 12 having a first coating area 121 and a second coating area 122 on the positive electrode collector 11, so as to form a thinning area around the edges of the material area of ​​the positive electrode sheet, and the coating method of the negative electrode sheet 20 is not limited.

[0086] The thickness of the positive electrode solid electrolyte layer 14 and the negative electrode solid electrolyte layer 23 is 5 μm, and the thickness is uniform. The insulating protective layer 16 is a 30 μm thick polyimide tape, the dimension L2 of the insulating portion covering the positive electrode sheet is 1 mm, the dimension L3 beyond the edge of the positive electrode sheet is 1 mm, and the dimension L4 extending to the positive electrode ear 15 is 3 mm.

[0087] Embodiment 2

[0088] This embodiment provides a membrane-free battery cell, which is different from the first embodiment in that the edge of the positive electrode sheet is coated with glue on both sides by a coating process to form an insulating protective layer 16, and the insulating protective layer 16 is a 10 μm thick mixed glue of polyimide and SiO2.

[0089] Comparative Example 1

[0090] The battery cell provided in this comparative example is a battery cell with a diaphragm, that is, the battery cell is not provided with a positive electrode solid electrolyte layer and a negative electrode solid electrolyte layer, and the edge of the positive electrode sheet is not provided with an insulating protective layer. It uses a positive electrode sheet and a negative electrode sheet with a diaphragm.

[0091] Comparative Example 2

[0092] The battery cell provided in this comparative example is a diaphragm-free battery cell, that is, both the positive electrode plate and the negative electrode plate are provided with a solid electrolyte layer, but the edge of the positive electrode plate is not provided with an insulating protective layer.

[0093] Comparative Example 3

[0094] The battery cell provided in this comparative example is a diaphragm-free battery cell, that is, both the positive electrode plate and the negative electrode plate are provided with a solid electrolyte layer, but only the edge of one side of the positive electrode plate connected to the positive electrode ear is provided with an edge portion, and an insulating protective layer is provided correspondingly, and the other three side edges are not provided with an edge portion with reduced thickness, nor are insulating protective layers provided.

[0095] Comparative Example 4

[0096] The battery cell provided in this comparative example is different from that in the first embodiment in that after the insulating protection layer is provided, the surface of the edge thereof is higher than the surface of the main body.

[0097] The cells in Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were subjected to lamination, pressurization and heating experiments, and the results obtained are as follows:

[0098]

[0099]

[0100] As can be seen from the above table, in the diaphragm-free battery cell provided by the utility model, by setting a thinned edge portion and setting an insulating protective layer 16 at the edge portion, the higher thermal and mechanical properties of the insulating protective layer 16 are used to protect the edge of the positive electrode sheet, thereby avoiding a short circuit when the composite positive electrode sheet 10 and the negative electrode sheet 20 are in contact, thereby realizing the preparation of a diaphragm-free battery cell and improving the safety performance of the diaphragm-free battery cell. By designing that the thickness of the insulating protective layer 16 after setting the edge portion does not exceed the planar area of ​​the positive electrode sheet, it is avoided that after setting the insulating protective layer 16, the thickness around the battery cell is too high, which affects the battery performance test.

[0101] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the scope of protection of the present invention. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A composite positive electrode sheet, characterized in that: include: A positive electrode sheet, the positive electrode sheet comprising a main body portion and an edge portion connected to each other, the edge portion being located at a circumferential edge of the main body portion, and a maximum thickness of the edge portion being no greater than a maximum thickness of the main body portion; An insulating protective layer (16) is coated on the edge portion, and a surface of the insulating protective layer (16) is not higher than a surface of the main body portion.

2. The composite positive electrode sheet according to claim 1, characterized in that: The positive electrode sheet comprises: A positive electrode current collector (11); A positive electrode coating (12) is coated on the surface of the positive electrode current collector (11), wherein the positive electrode coating (12) comprises a first coating area (121) and a second coating area (122) arranged around the edge of the first coating area (121), the thickness of the first coating area (121) is greater than the thickness of the second coating area (122), and the edge portion is formed at the second coating area (122).

3. The composite positive electrode sheet according to claim 2, characterized in that: The thickness of the second coating region (122) gradually decreases in a direction away from the edge of the positive electrode current collector (11).

4. The composite positive electrode sheet according to claim 1, characterized in that: The positive electrode sheet comprises: A positive electrode current collector (11), wherein the surface of the positive electrode current collector (11) comprises a coating area and a non-coating area (111) arranged around the circumferential edge of the coating area; The positive electrode coating (12) covers the coating area and exposes the non-coating area (111), and the non-coating area (111) forms the edge portion.

5. The composite positive electrode sheet according to any one of claims 2 to 4, characterized in that: The positive electrode sheet also includes a positive electrode solid electrolyte layer (14), the positive electrode solid electrolyte layer (14) has a uniform thickness and covers the positive electrode coating (12).

6. The composite positive electrode sheet according to claim 5, characterized in that: The thickness of the positive electrode solid electrolyte layer (14) is 1 μm-50 μm.

7. The composite positive electrode sheet according to any one of claims 1 to 4, characterized in that: Along the direction from the edge of the positive electrode sheet toward the center of the positive electrode sheet, the size of the edge portion covered by the insulating protection layer (16) is 0.5 mm-1 mm.

8. The composite positive electrode sheet according to any one of claims 1 to 4, characterized in that: The insulating protective layer (16) extends to the outside of the edge of the positive electrode sheet.

9. The composite positive electrode sheet according to claim 8, characterized in that: The insulating protective layer (16) extends to the outside of the edge of the positive electrode sheet in a size of 0.5 mm to 1 mm.

10. The composite positive electrode sheet according to any one of claims 1 to 4, characterized in that: The positive electrode sheet also includes a positive electrode tab (15) connected to the edge portion, and the insulating protection layer (16) extends from the edge portion to cover a portion of the positive electrode tab (15).

11. The composite positive electrode sheet according to claim 10, characterized in that: Along the extension direction of the positive electrode tab (15), the size of the insulating protective layer (16) covering the positive electrode tab (15) is 1.5 mm to 3 mm.

12. The composite positive electrode sheet according to any one of claims 1 to 4, characterized in that: The insulating protective layer (16) is a heat-resistant adhesive tape, a heat-resistant polymer layer or a ceramic adhesive coating; And / or, the thickness of the insulating protective layer (16) is 5 μm-50 μm; And / or, the insulating protective layer (16) is bonded and fixed to the positive electrode sheet.

13. The composite positive electrode sheet according to any one of claims 1 to 4, characterized in that: The edge portion comprises a first surface and a second surface arranged opposite to each other, and both the first surface and the second surface are covered with the insulating protective layer (16).

14. A diaphragm-free battery cell, characterized in that: It comprises a stacked negative electrode sheet (20) and a composite positive electrode sheet as claimed in any one of claims 1 to 13.

15. The membrane-free battery cell according to claim 14, characterized in that: The negative electrode plate (20) comprises a negative electrode current collector (21) and a negative electrode coating (22) covering the negative electrode current collector (21), and the projection of the negative electrode coating (22) on the composite positive electrode plate is located within the range surrounded by the insulating protective layer (16).

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