A positive electrode sheet and a battery cell

Abstract

The utility model discloses a positive electrode sheet and a battery core. The positive electrode sheet of the utility model comprises a current collector, a solid electrolyte layer and an active material layer. The solid electrolyte layer is coated on the current collector; the active material layer is coated on the solid electrolyte layer; wherein the surface density of the solid electrolyte layer is w1, the thickness of the solid electrolyte layer is h1, the surface density of the active material layer is w2, the thickness of the active material layer is h2, and the relationship between w1, h1, w2 and h2 is satisfied: 2g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 , h1<h2. The solid electrolyte layer and the active material layer are coated on the current collector in sequence. While the safety performance and mechanical abuse performance of the battery cell are improved, by limiting the comprehensive density of each coating on the current collector per unit area, the possibility of the positive electrode sheet being broken due to the high compaction density of the positive electrode sheet is reduced, and the possibility of the positive electrode sheet being too low in compaction density, which leads to a decrease in the charging and discharging performance and energy density of the battery cell using the positive electrode sheet, is reduced, and the performance of the battery cell is better.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium ion batteries, in particular to a positive electrode sheet and a battery core. Background Art

[0002] In the related art, in order to improve the safety performance and mechanical abuse performance of the battery cell, a solid electrolyte layer is generally coated between the positive current collector and the positive active material coating to prevent the aluminum foil from directly contacting the negative active material during the needle puncture process. However, the solid electrolyte layer will affect the compaction density of the positive electrode sheet after being compacted by a roller. After being compacted by a roller, the existing positive electrode sheet may break due to inappropriate compaction density, or when the positive electrode sheet is used in the battery cell, the inappropriate compaction density will lead to problems such as decreased charge and discharge performance of the battery cell and decreased energy density. Utility Model Content

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes a positive electrode sheet, which has good safety performance when applied to a battery cell, can make the battery cell have good charge and discharge performance, high energy density and reduce the possibility of the electrode sheet breaking.

[0004] The utility model also provides a battery core having the positive electrode sheet.

[0005] The utility model also provides another battery core having the positive electrode sheet.

[0006] The positive electrode sheet according to the first embodiment of the utility model comprises:

[0007] a current collector having a set thickness direction;

[0008] A solid electrolyte layer, coated on the current collector;

[0009] An active material layer, coated on the solid electrolyte layer;

[0010] The surface density of the solid electrolyte layer is w1, the surface density of the active material layer is w2, along the thickness direction of the current collector, the size of the solid electrolyte layer is h1, the size of the active material layer is h2, w1, h1, w2 and h2 satisfy the relationship: 2g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 , h1<h2.

[0011] The positive electrode sheet according to the embodiment of the utility model has at least the following beneficial effects: the solid electrolyte layer and the active material layer are coated on the current collector in sequence, and the safety performance of the battery cell is improved. At the same time, by limiting the comprehensive density of each coating on the current collector per unit area, the impact of too high or too low compaction density of the positive electrode sheet is reduced. For example, the possibility of the positive electrode sheet being broken due to too high compaction density is reduced, and the possibility of the positive electrode sheet being too low compaction density causing the battery cell using the positive electrode sheet to decrease in charging and discharging performance and energy density is reduced, so the performance of the battery cell is better.

[0012] According to some embodiments of the present invention, the solid electrolyte layer is coated on at least one side of the current collector in the thickness direction, and along the thickness direction of the current collector, the size of the solid electrolyte layer is 0.5 μm to 10 μm.

[0013] According to some embodiments of the present invention, the particle size distribution of the solid electrolyte layer particles satisfies: Dv90≤20μm, 0.15μm≤Dv50≤0.75μm, Dv10≤0.3μm.

[0014] According to some embodiments of the present invention, the peel strength of the positive electrode sheet is ≥20N / m.

[0015] According to some embodiments of the present invention, the peeling strength between the solid electrolyte layer and the current collector is greater than the peeling strength between the active material layer and the solid electrolyte layer.

[0016] According to some embodiments of the present invention, the absolute value of the difference between the elongation of the active material layer and the elongation of the solid electrolyte layer is ≤1%.

[0017] According to some embodiments of the present invention, the active material of the active material layer is lithium cobalt oxide, and w1, h1, w2 and h2 satisfy the relationship: 3.7 g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 .

[0018] According to some embodiments of the present invention, the active material of the active material layer is lithium iron phosphate, and w1, h1, w2 and h2 satisfy the relationship: 2.0 g / cm 3 ≤(w1+w2) / (h1+h2)≤2.6g / cm 3 .

[0019] The battery cell according to the second embodiment of the utility model includes:

[0020] Multiple negative electrode sheets;

[0021] A plurality of positive electrode sheets provided by the first embodiment above, wherein the plurality of positive electrode sheets and the plurality of negative electrode sheets are sequentially arranged along the thickness direction of the battery cell;

[0022] A plurality of separators are provided between adjacent positive electrode sheets and adjacent negative electrode sheets.

[0023] The battery cell according to the embodiment of the utility model has at least the following beneficial effects: the battery cell includes the positive electrode sheet provided by the embodiment of the first aspect above, and at least has all the advantages of the positive electrode sheet. By sequentially coating the solid electrolyte layer and the active material layer on the current collector of the positive electrode sheet, the safety performance and mechanical abuse performance of the battery cell are improved, while limiting the comprehensive density of each coating on the current collector per unit area, so that the positive electrode sheet will not be increased in possibility of fracture due to excessively high compaction density, nor will the battery cell charge and discharge performance and energy density be reduced due to too low compaction density, and the battery cell has better performance.

[0024] A battery cell according to a third aspect of the present utility model includes:

[0025] Negative electrode;

[0026] The positive electrode sheet provided by the embodiment of the first aspect above;

[0027] The separator is arranged between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet, the positive electrode sheet and the separator are wound to form the battery cell.

[0028] The battery cell according to the embodiment of the utility model has at least the following beneficial effects: the battery cell includes the positive electrode sheet provided by the embodiment of the first aspect above, and at least has all the advantages of the positive electrode sheet. The solid electrolyte layer and the active material layer are sequentially coated on the current collector of the positive electrode sheet, and the safety performance and mechanical abuse performance of the battery cell are improved while limiting the comprehensive density of each coating on the current collector per unit area, so that the possibility of the positive electrode sheet being broken due to excessively high compaction density is not increased, and the battery cell's charge and discharge performance and energy density are not reduced due to too low compaction density, and the battery cell has better performance.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described below with reference to the accompanying drawings and embodiments, wherein:

[0031] Figure 1 It is a cross-sectional view of the positive electrode sheet of the embodiment of the utility model.

[0032] Reference numerals: current collector 100 , active material layer 110 , solid electrolyte layer 120 . DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0034] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] In the description of the present utility model, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0036] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0037] In the description of the utility model, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0038] Reference Figure 1The first embodiment of the utility model provides a positive electrode sheet, including a current collector 100, a solid electrolyte layer 120 and an active material layer 110. The current collector 100 has a set thickness direction, the solid electrolyte layer 120 is coated on the current collector 100; the active material layer 110 is coated on the solid electrolyte layer 120; the surface density of the solid electrolyte layer 120 is w1, the surface density of the active material layer 110 is w2, along the thickness direction of the current collector 100, the size of the solid electrolyte layer 120 is h1, the size of the active material layer 110 is h2, and the relationship between w1, h1, w2 and h2 is satisfied: 2g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 , h1<h2.

[0039] The solid electrolyte layer 120 and the active material layer 110 are coated on the current collector 100 in sequence. When subjected to mechanical abuse such as needle puncture, the solid electrolyte layer 120 and the current collector 100 have a high bonding strength. When needle puncture occurs, the solid electrolyte layer 120 can remain on the current collector 100, preventing the current collector 100 from directly contacting the negative electrode active material, preventing the occurrence of short circuits, and improving the safety performance and mechanical abuse performance of the battery cell. At the same time, the formula (w1+w2) / (h1+h2) calculates the comprehensive density of each coating per unit area, that is, the weighted average density. The comprehensive density can be selected as 2g / cm 3 , 2.3g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 、3.0g / cm 3 、3.3g / cm 3 、3.5g / cm 3 、3.8g / cm 3 , 4.0g / cm 3 , 4.2g / cm 3 or 2g / cm 3 ~4.2g / cm 3 By limiting the comprehensive density of each coating layer per unit area on the current collector 100, the impact of too high or too low compaction density of the positive electrode sheet can be reduced. For example, the possibility of the positive electrode sheet being broken due to too high compaction density of the positive electrode sheet can be reduced, and the possibility of the positive electrode sheet being too low in compaction density can be reduced, which leads to a decrease in the charge and discharge performance and energy density of the battery cell using the positive electrode sheet.

[0040] In addition, compared to liquid batteries, when the positive electrode sheet of this embodiment is applied to the battery cell, since the ion conductivity of the solid electrolyte decreases less with temperature changes, there is an interlocking part at the junction of the solid electrolyte layer 120 and the active material layer 110, and the ion conductivity between the positive electrode active materials in the interlocking part decreases less with temperature changes, thereby improving the battery cell performance at lower temperatures and making the overall performance of the battery cell better.

[0041] If the overall density of the coating on the current collector 100 is lower than 2 g / cm 3 The low comprehensive density of the coating after rolling will cause the thickness of the electrode to be still large after rolling, which will reduce the energy density of the battery cell when applied to the battery cell. In addition, the particles of the solid electrolyte layer 120 and the active material layer 110 are not in close contact when the compaction density is low, resulting in an increase in the impedance inside the battery cell, affecting the charge and discharge efficiency of the battery cell.

[0042] If the comprehensive density of the coating on the current collector 100 is higher than 4.2g, the comprehensive density of the coating after rolling is too high. During the rolling process, the particles of the solid electrolyte layer 120 may be embedded in the current collector 100, causing damage to the current collector 100, reducing the overall strength of the electrode and making it easy to break. In addition, the particles in the active material layer 110 may be broken during the rolling process, resulting in an increase in side reactions when the battery cell is used and performance deterioration, such as deterioration in the storage performance and cycle performance of the battery cell, and the possibility of gas bulging of the battery cell is also increased accordingly.

[0043] The relevant performance of different positive electrode sheets when applied to battery cells was tested, and the test results are shown in Table 1:

[0044] Table 1

[0045]

[0046] In Table 1, the thickness of each positive electrode sheet in the experimental groups 1-4 and the control group 1 before rolling is equal. Referring to Table 1, the experimental groups 1-4 are cells made of positive electrode sheets coated with solid electrolyte layer 120, and the control group 1 is a cell made of positive electrode sheets not coated with solid electrolyte layer 120. In this test, the comprehensive density of the coating on the positive electrode sheet of the experimental group 1 is in the range of 3.7g / cm 3 Up to 4.2g / cm 3 The overall density of the coating on the positive electrode sheet of experimental group 2 is greater than 4.2g / cm 3 , while the comprehensive density of the coating on the positive electrode of Experimental Group 3 is in the range of 2.0 g / cm 3 Up to 2.6g / cm 3 The overall density of the coating on the positive electrode of experimental group 4 is less than 2.0 g / cm 3The active material selected for the experimental group 1, experimental group 2 and control group 1 is lithium cobalt oxide, and the active material selected for the positive electrode sheet of the experimental group 3 and experimental group 4 is lithium iron phosphate. By comparing the experimental group 1, experimental group 3 and control group 1, it can be seen that when dealing with mechanical abuse such as acupuncture, the solid electrolyte layer 120 can enhance the safety performance of the battery cell, avoid fire and explosion of the battery cell, and enhance the discharge performance of the battery cell in a low temperature environment.

[0047] Among experimental groups 1-4, the comprehensive density of the positive electrode sheets of experimental groups 1 and 3 meets the comprehensive density range of the present application, while the comprehensive density of the positive electrode sheets of experimental groups 2 and 4 exceeds the upper and lower limits of the comprehensive density range of the present application, respectively. It can be seen from the comparison of experimental groups 1-4 that the positive electrode sheets that meet the comprehensive density range of the present application, when used in battery cells, will not have a significant impact on the battery cell capacity and rate discharge capability, and will have a good improvement on the low temperature discharge performance of the battery cell.

[0048] In some embodiments, the solid electrolyte layer 120 includes a solid electrolyte, an adhesive and a conductive agent. The solid electrolyte includes one or more combinations of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LZO), lithium lanthanum zirconium tantalum oxide (LLZTO) and lithium aluminum germanium phosphate (LAGP), etc. The adhesive includes one or more combinations of polyvinylidene fluoride, styrene butadiene rubber (SBR), polyacrylic acid, polytetrafluoroethylene and polyvinyl alcohol, and the conductive agent includes one or more combinations of conductive carbon black, carbon nanotubes, graphene, conductive graphite and carbon fiber. The solid electrolyte layer 120 may also include an inorganic filler, and the inorganic filler includes one or more combinations of alumina, boehmite, and lithium iron phosphate.

[0049] The active material of the active material layer 110 is used to store and release lithium ions. In some embodiments, the active material of the active material layer 110 is lithium cobalt oxide, and the relationship between w1, h1, w2 and h2 is: 3.7 g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 When the active material in the active material layer 110 is lithium cobalt oxide, the overall density per unit area of ​​the positive electrode sheet is controlled at 3.7 g / cm 3 Up to 4.2g / cm 3 The overall density per unit area of ​​the positive electrode can be selected as 3.7g / cm 3 、3.8g / cm 3 、3.9g / cm 3 , 4.0g / cm 3 , 4.1g / cm 3 , 4.2g / cm 3 or 3.7g / cm 3 Up to 4.2g / cm 3Any other value in between.

[0050] In some other embodiments, the active material of the active material layer 110 is lithium iron phosphate, and the relationship between w1, h1, w2 and h2 is: 2.0 g / cm 3 ≤(w1+w2) / (h1+h2)≤2.6g / cm 3 When the active material in the active material layer 110 is lithium iron phosphate, the overall density per unit area of ​​the positive electrode sheet is controlled at 2.0 g / cm 3 Up to 2.6g / cm 3 The overall density per unit area of ​​the positive electrode can be selected as 2.0 g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 or 2.0g / cm 3 Up to 2.6g / cm 3 Any other value in between.

[0051] In other embodiments, the active material of the active material layer 110 may also be one or a combination of lithium iron manganese phosphate, lithium cobalt oxide, lithium iron manganese, and nickel cobalt manganese lithium.

[0052] In some embodiments, the active material of the active material layer 110 may be coated on the solid electrolyte layer together with a binder and a conductive agent to form the active material layer 110. The binder may be one or more combinations of polyvinylidene fluoride, styrene-butadiene rubber (SBR), polyacrylic acid, polytetrafluoroethylene and polyvinyl alcohol, and the conductive agent may be one or more combinations of conductive carbon black, carbon nanotubes, graphene, conductive graphite and carbon fiber.

[0053] In some embodiments, the solid electrolyte layer is coated on at least one side of the current collector 100 in the thickness direction, and the size of the solid electrolyte layer 120 is 0.5 μm to 10 μm along the thickness direction of the current collector 100. The size of the solid electrolyte layer 120 can be selected as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any other value between 0.5 μm and 10 μm. The coating thickness of the solid electrolyte cannot be too small. For example, when it is less than 0.5 μm, due to the large particle size of some particles in the solid electrolyte layer 120, some areas may be missed and fail to achieve a good protection effect; the coating thickness of the solid electrolyte cannot be too large. For example, when it is greater than 10 μm, excessive coating thickness will cause the overall energy density of the battery cell to decrease.

[0054] In some embodiments, the solid electrolyte layer is coated on both sides of the current collector 100 in the thickness direction. The thickness of the solid electrolyte layer 120 on both sides can be the same or different, and it is only necessary to ensure that the thickness of the solid electrolyte layer 120 on both sides is within the above-mentioned size range.

[0055] In some embodiments, the particle size distribution of the particles of the solid electrolyte layer 120 satisfies: Dv90≤20μm, 0.15μm≤Dv50≤0.75μm, Dv10≤0.3μm. Among them, Dv10 represents the first particle size, and the particles smaller than the first particle size on the particle size distribution curve account for 10% of the total number of particles, Dv50 represents the median particle size, and Dv90 represents the second particle size, and the particles smaller than the second particle size on the particle size distribution curve account for 90% of the total number of particles. The particle size of the solid electrolyte layer 120 is generally small, which is convenient for mutual embedding with the active material layer 110 after the compaction step, thereby improving the connection strength between adjacent coatings. In addition, since the solid electrolyte layer 120 has a certain influence on the energy density of the battery cell, it needs to be coated with a smaller thickness, so the use of a smaller particle size can effectively reduce the possibility of leaking the solid electrolyte layer 120.

[0056] In some embodiments, the peel strength of the positive electrode sheet is ≥20N / m, that is, the peel strength between the active material layer 110 and the current collector 100, between the solid electrolyte layer 120 and the active material layer 110, and inside each coating is not less than 20N / m, so that each coating on the current collector 100 is not easy to fall off during subsequent processing and use, ensuring the safety performance of the positive electrode sheet used in the battery cell. The peel strength of the positive electrode sheet is positively correlated with the content of the adhesive in each coating, so when the size of the adhesive force needs to be adjusted, it can be achieved by adjusting the content of the adhesive in each coating. Among them, the peel strength of the positive electrode sheet can be measured by existing equipment such as a peel tester.

[0057] Furthermore, the peel strength between the solid electrolyte layer 120 and the current collector 100 is greater than the peel strength between the solid electrolyte layer 120 and the active material layer 110. Specifically, the peel strength between the solid electrolyte layer 120 and the current collector 100 is ≥80N / m, and the peel strength between the solid electrolyte layer 120 and the active material layer 110 is ≥40N / m. The solid electrolyte layer 120 has good stability and strong adhesion to the current collector 100. Therefore, when the positive electrode sheet is applied to the battery cell and subjected to mechanical abuse such as needle puncture, the solid electrolyte layer 120 is less likely to be detached from the current collector 100 at the needle puncture site, and the solid electrolyte layer 120 can be coated on the steel needle to provide a certain degree of isolation, thereby avoiding direct contact between the negative electrode active material and the positive electrode current collector 100 to a large extent.

[0058] The bonding force between the active material layer 110 and the solid electrolyte layer 120 does not need to be too high. On the one hand, the bonding force of the active material layer 110 mainly depends on the content of the adhesive in the components, and too high a content of the adhesive will affect the energy density of the battery cell; on the other hand, after the positive electrode sheet is rolled, the particles in the active material layer 110 and the solid electrolyte layer 120 will be interlocked, so that the active material layer 110 can be tightly connected to the solid electrolyte layer 120.

[0059] In some embodiments, the absolute value of the difference between the elongation of the active material layer 110 and the elongation of the solid electrolyte layer 120 is ≤1%. After the positive electrode sheet is rolled, the active material layer 110 and the solid electrolyte layer 120 can still be well overlapped because the difference in elongation is small. When the difference in elongation is large, stress in the direction of moving away from each other will be generated between the active material layer 110 and the solid electrolyte layer 120, which may cause the bonding strength between the active material layer 110 and the solid electrolyte layer 120 to decrease.

[0060] The second embodiment of the utility model provides a battery cell (not shown in the figure), comprising a plurality of negative electrode sheets, a plurality of separators and a plurality of positive electrode sheets provided in the first embodiment above. The plurality of positive electrode sheets and the plurality of negative electrode sheets are arranged in sequence along the thickness direction of the battery cell; the separator is arranged between adjacent positive electrode sheets and negative electrode sheets. The battery cell includes the positive electrode sheet provided in the first embodiment above, and at least has all the advantages of the positive electrode sheet, which will not be repeated here.

[0061] The third aspect of the present invention provides another battery cell (not shown in the figure), comprising a negative electrode sheet, a separator and the positive electrode sheet provided in the first aspect of the present invention. The separator is arranged between the negative electrode sheet and the positive electrode sheet, and the negative electrode sheet, the positive electrode sheet and the separator are wound to form a battery cell. The battery cell includes the positive electrode sheet provided in the first aspect of the present invention, and at least has all the advantages of the positive electrode sheet, which will not be repeated here.

[0062] The embodiments of the utility model are described in detail above in conjunction with the accompanying drawings, but the utility model is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the utility model. In addition, the embodiments of the utility model and the features in the embodiments can be combined with each other without conflict.

Claims

1. A positive electrode sheet, characterized in that: include: a current collector having a set thickness direction; A solid electrolyte layer, coated on the current collector; An active material layer, coated on the solid electrolyte layer; The surface density of the solid electrolyte layer is w1, the surface density of the active material layer is w2, along the thickness direction of the current collector, the size of the solid electrolyte layer is h1, the size of the active material layer is h2, w1, h1, w2 and h2 satisfy the relationship: 2g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 , h1<h2.

2. The positive electrode sheet according to claim 1, characterized in that: The solid electrolyte layer is coated on at least one side of the current collector in the thickness direction, and the size of the solid electrolyte layer along the thickness direction of the current collector is 0.5 μm to 10 μm.

3. The positive electrode sheet according to claim 1, characterized in that: The peel strength of the positive electrode sheet is ≥20N / m.

4. The positive electrode sheet according to claim 3, characterized in that: The peel strength between the solid electrolyte layer and the current collector is greater than the peel strength between the active material layer and the solid electrolyte layer.

5. The positive electrode sheet according to claim 1, characterized in that: An absolute value of a difference between an elongation of the active material layer and an elongation of the solid electrolyte layer is ≤1%.

6. The positive electrode sheet according to claim 1, characterized in that: The active material of the active material layer is lithium cobalt oxide, and w1, h1, w2 and h2 satisfy the relationship: 3.7 g / cm 3 ≤(w1+w2) / (h1+h2)≤4.2g / cm 3 .

7. The positive electrode sheet according to claim 1, characterized in that: The active material of the active material layer is lithium iron phosphate, and w1, h1, w2 and h2 satisfy the relationship: 2.0 g / cm 3 ≤(w1+w2) / (h1+h2)≤2.6g / cm 3 .

8. A battery cell, characterized in that: include: Multiple negative electrode sheets; A plurality of positive electrode sheets according to any one of claims 1 to 7, wherein the plurality of positive electrode sheets and the plurality of negative electrode sheets are arranged in sequence along the thickness direction of the battery cell; A plurality of separators are provided between adjacent positive electrode sheets and adjacent negative electrode sheets.

9. A battery cell, characterized in that: include: Negative electrode; The positive electrode sheet according to any one of claims 1 to 7; The separator is arranged between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet, the positive electrode sheet and the separator are wound to form the battery cell.

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