Battery cell and battery

Abstract

The utility model discloses a battery cell and a battery. The battery cell comprises: a positive plate comprising a first foil and a first active material layer connected to the first foil; the negative plate comprises a second foil and a second active substance layer, and the second active substance layer is connected to the second foil; the diaphragm, the positive plate, the diaphragm and the negative plate are sequentially stacked and wound into a winding structure, and the surface density of the second active material layer is gradually increased from the winding starting end to the winding tail end of the winding structure. The battery cell disclosed by the utility model can effectively avoid the waste of active substances of the negative electrode.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of battery, concretely relates to electric core and battery. BACKGROUND

[0002] In the field of lithium battery manufacturing, coating technology is one of the key process steps, and its main purpose is to uniformly coat the battery slurry on the metal foil to form a pole piece with a certain surface density. At present, the commonly used coating methods for lithium batteries include transfer coating and extrusion coating. Both methods aim to achieve uniform distribution of slurry on the substrate surface to form a coating with constant surface density.

[0003] The key structure of the transfer coating machine includes a doctor blade, a coating roller and a backing roller. Its working principle is to control the amount of slurry transferred by adjusting the gap between the doctor blade and the coating roller, thereby achieving uniform coating. Extrusion coating, also known as slit coating, controls the width and shape of the pole piece through the die gap, controls the surface density through the coating pump speed, affects the production efficiency through the coating speed, and relates to the stability of the pole piece shape and weight through the coating pressure.

[0004] However, in the production of cylindrical batteries, the N / P value (ratio of negative electrode capacity to positive electrode capacity) of different areas of the roll core formed by winding the pole piece with a fixed surface density is not consistent. Specifically, the active material of the negative electrode in the inner circle of the cylindrical battery is much more than that of the positive electrode. Therefore, the waste of materials will lead to high manufacturing cost of the battery. SUMMARY

[0005] The utility model aims at at least solves one of the technical problems existing in the prior art. To this end, the utility model provides an electric core which can effectively avoid the waste of active material of the negative electrode.

[0006] The utility model further provides a battery with the above-mentioned electric core.

[0007] According to the electric core of the first aspect embodiment of the utility model, comprising:

[0008] The positive pole piece comprises a first foil and a first active material layer, and the first active material layer is connected to the first foil.

[0009] The negative pole piece comprises a second foil and a second active material layer, and the second active material layer is connected to the second foil.

[0010] The separator, the positive pole piece, the separator and the negative pole piece are sequentially stacked and wound into a winding structure. Along the winding start end to the winding tail end of the winding structure, the surface density of the second active material layer gradually increases.

[0011] According to the embodiment of the utility model, the positive and negative electrode sheets are coated with the slurry on the substrate, and the surface density of the single side of the positive and negative electrode sheets remains consistent from the winding start end to the winding tail end in the prior art, the N / P value (positive and negative electrode sheet capacity ratio) of the inner circle layer at the winding start end of the winding structure is relatively high after the winding structure is formed, and the N / P value decreases with the increase of the winding number. This is because the active material coated on the winding start end of the negative electrode sheet is excessive, which leads to the N / P value of the inner circle layer at the winding start end being too high, and thus the active material of the negative electrode and the available space inside the battery are wasted. In the battery of the application, the surface density of the second active material layer connected to the second foil gradually increases from the winding start end to the winding tail end of the winding structure. Thus, by increasing and decreasing the surface density of the active material in different regions of the negative electrode sheet, i.e. the surface density of the active material coated at the winding start end is less than the surface density of the active material coated at the winding tail end, the N / P value at the winding start end (inner circle layer) is avoided from being too high. Thus, the battery of the application can effectively avoid the waste of the active material of the negative electrode.

[0012] According to some embodiments of the utility model, the thickness of the second active material layer gradually increases from the winding start end to the winding tail end of the negative electrode sheet.

[0013] According to some embodiments of the utility model, the difference between the thickness of the winding start end of the second active material layer and the thickness of the winding tail end of the second active material layer is L, and 5um≤L≤10um.

[0014] According to some embodiments of the utility model, the second active material layer comprises a first coating layer and a second coating layer, wherein the first coating layer is coated on the second foil, and the second coating layer is coated on the first coating layer.

[0015] From the winding start end to the winding tail end, the surface density of the first coating layer remains unchanged, and the surface density of the second coating layer gradually increases.

[0016] According to some embodiments of the utility model, the thickness of the first coating layer remains unchanged, and the thickness of the second coating layer gradually increases from the winding start end to the winding tail end of the negative electrode sheet.

[0017] According to some embodiments of the utility model, the second coating layer comprises a plurality of intermittent coating layers, and each intermittent coating layer is arranged in a spaced manner.

[0018] According to some embodiments of the utility model, the second active material layer comprises a first coating layer and a second coating layer, wherein the first coating layer is coated on the second foil, and the second coating layer is coated on the first coating layer.

[0019] The second coating includes a plurality of intermittent coatings, each of the intermittent coatings is arranged at intervals p, the thickness of the intermittent coatings remains unchanged, and the intervals p gradually decrease from the winding start end to the winding end.

[0020] According to some embodiments of the present application, the surface density of the first active material gradually increases from the winding start end to the winding end of the positive electrode sheet.

[0021] According to some embodiments of the present application, the thickness of the first active material gradually increases from the winding start end to the winding end of the positive electrode sheet.

[0022] According to the second aspect of the embodiments of the present application, the battery includes the battery cell.

[0023] According to the battery of the embodiments of the present application, at least the following beneficial effects are achieved: in the battery cell of the present application, the surface density of the second active material layer connected to the second foil gradually increases from the winding start end to the winding end of the winding structure. Thus, by increasing and decreasing the surface density of the active material in different regions of the negative electrode sheet, i.e., the surface density of the active material coated at the winding start end is less than the surface density of the active material coated at the winding end, the N / P value at the winding start end (inner coil layer) is avoided. Thus, the battery with the above battery cell can effectively avoid the waste of the active material of the negative electrode.

[0024] Additional aspects and advantages of the present application will be given in part in the following description, some of which will become apparent from the following description, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present application will be further described below in conjunction with the drawings and embodiments, in which:

[0026] Figure 1 is a schematic view of the negative electrode sheet of the first embodiment of the present application;

[0027] Figure 2 is a schematic view of the negative electrode sheet of the second embodiment of the present application;

[0028] Figure 3 is a schematic view of the negative electrode sheet of the third embodiment of the present application;

[0029] Figure 4 is a schematic view of the negative electrode sheet of the fourth embodiment of the present application;

[0030] Figure 5 is a schematic view of the negative electrode sheet of the fifth embodiment of the present application;

[0031] Figure 6 is a schematic view of the positive electrode sheet of the sixth embodiment of the present application.

[0032] Reference signs:

[0033] Positive electrode sheet 100; first foil 110; first active material layer 120; negative electrode sheet 200; second foil 210; second active material layer 220; first coating layer 221; second coating layer 222; intermittent coating layer 212a; separator 300. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary only, and are used only for the purpose of explaining the present application, and are not to be understood as a limitation of the present application.

[0035] In the description of the present application, it should be understood that, in relation to the orientation description, for example, the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application.

[0036] In the description of the present application, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If it is described as first, second, it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0037] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be understood in a broad sense, and the person skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0038] In the description of the present application, the description of the reference terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0039] In the related art, in the manufacturing process of cylindrical lithium batteries, the winding structure formed by the fixed areal density of the electrode sheet winding technology has inconsistent N / P values in different internal regions. In particular, the inner circle part of the battery, the excessive amount of active material of the negative electrode causes the N / P value of the inner circle part to be higher than that of the outer circle part. This unbalanced active material ratio leads to waste of materials. Due to the excess of negative electrode active material in the inner circle, not only the effective utilization of battery materials is affected, but also the overall manufacturing cost is increased. In addition, this uneven N / P value distribution may also affect the electrochemical performance and cycle stability of the battery, because during the charging and discharging process of the battery, the electrochemical reaction activity and heat distribution in different regions may differ, thereby affecting the overall performance and life of the battery. Therefore, achieving uniform distribution of N / P value in the winding core is of great significance to improve the performance of the battery, reduce the cost, and improve the consistency and reliability of the battery.

[0040] Based on the above problems, the present application proposes an electric core which aims to solve the problems existing in the related art to some extent.

[0041] In some embodiments, the electric core includes a positive electrode sheet 100, a negative electrode sheet 200, and a separator 300. The positive electrode sheet 100 includes a first foil 110 and a first active material layer 120 connected to the first foil 110. The negative electrode sheet 200 includes a second foil 210 and a second active material layer 220 connected to the second foil 210. The positive electrode sheet 100, the separator 300, and the negative electrode sheet 200 are sequentially stacked and wound into a winding structure, and the areal density of the second active material layer 220 gradually increases from the winding start end to the winding tail end of the winding structure.

[0042] In the prior art, the single-sided coating areal density of the positive and negative electrodes remains consistent from the winding start end to the winding tail end, forming a flat plate-shaped coating. After forming the winding structure, the N / P value (positive and negative electrode sheet 200 gram capacity ratio) of the inner circle layer of the winding start end of the negative electrode sheet 200 of the winding structure is relatively high, and the N / P value decreases as the number of winding increases. The excessive active material coated at the winding start end causes the N / P value of the inner circle layer at the winding start end of the negative electrode sheet 200 to be too high, thereby wasting the active material of the negative electrode and reducing the available space inside the battery.

[0043] In the battery cell of the present application, the face density of the second active material layer 220 of the negative electrode sheet 200 connected to the second foil 210 gradually increases from the winding start end to the winding end of the winding structure. In this way, by increasing and decreasing the face density of the active material in different regions of the negative electrode sheet 200, i.e., the face density of the active material coated at the winding start end is less than the face density of the active material coated at the winding end, the N / P value at the winding start end (inner layer) is further avoided to be too high. In this way, the battery cell of the present application can effectively avoid the waste of the active material of the negative electrode, and can increase the available space inside the battery.

[0044] Further, there are many ways to increase and decrease the face density of the second active material layer 220, for example, by controlling the coating thickness of the second active material layer 220, or coating the second active material layer 220 twice, the first time coating the active material with consistent face density from the winding start end to the winding end, and the second time coating the active material with inconsistent spacing or thickness on the active material coated in the first time, all of which can achieve the change of the face density of the second active material layer 220, which will be described in detail below.

[0045] Therefore, compared with the related art, since the battery cell of the present application reduces the active material coated in the inner layer of the negative electrode sheet 200, the waste of the negative electrode active material can be reduced, the manufacturing cost can be saved, and due to the reduction of the active material, the space occupied by the negative electrode sheet 200 at the winding start end is reduced, and the available space inside the battery is saved. At the same time, by reducing the amount of active material of the negative electrode sheet 200 at the winding start end (inner layer), the N / P value at the winding start end (inner layer) can be reduced, so that the N / P value of the battery from the inner layer to the outer layer is generally consistent, and the overall performance of the battery is improved.

[0046] In the present application, the negative electrode active material can use the negative electrode active material commonly known in the art for batteries. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used only one kind alone, or two or more kinds in combination.

[0047] Reference Figure 1According to some embodiments of the present application, the thickness of the second active material layer 220 gradually increases from the winding start end to the winding end of the negative electrode sheet 200. As described above, one of the methods for changing the surface density of the second active material layer 220 will be described in detail, that is, by changing the thickness of the second active material layer 220.

[0048] Since the related art negative electrode sheet 200 is coated with an active material of a uniform thickness on the foil, that is, an active material layer of a substantially flat plate shape with a constant thickness is formed on the foil, the coating method of the prior art can cause the N / P value of the winding start end (inner circle layer) to be significantly greater than the N / P value of the winding end (outer circle layer). The calculation formula of the N / P value is: gram capacity of negative electrode active material * negative electrode surface density * negative electrode active material content ratio / (gram capacity of positive electrode active material * positive electrode surface density * positive electrode active material content ratio). Therefore, in order to make the N / P value inside the battery consistent as a whole, the thickness of the active material of the negative electrode sheet 200 at the winding start end can be appropriately reduced, and the thickness of the active material of the negative electrode sheet 200 at the winding end can be appropriately increased. Through this adjustment, the N / P value inside the winding core can be balanced, the possibility of lithium precipitation in the N / P minimum value region inside the related art battery cell can be reduced, the use amount of active material in the N / P maximum value region can be reduced, costs can be saved, the available space inside the battery can be increased, and thus the energy density of the battery is improved.

[0049] According to some embodiments of the present application, the difference between the thickness of the winding start end of the second active material layer 220 and the thickness of the winding end of the second active material layer 220 is L, and 5um≤L≤10um. Specifically, although it has been limited above that the thickness of the second active material layer 220 gradually increases from the winding start end to the winding end of the negative electrode sheet 200, the change in the thickness of the coated second active material layer 220 is extremely small. In this embodiment, it is preferred that the difference L between the maximum thickness and the minimum thickness of the second active material layer 220 is 5um≤L≤10um. For example, 5um, 6um, or 10um. An excessively high N / P value means that the negative electrode capacity is too much relative to the positive electrode capacity, which can cause the negative electrode to be shallowly charged and discharged, and the positive electrode to be deeply charged and discharged, affecting the cycle stability and safety of the battery. An excessively low N / P value means that the positive electrode capacity is too much relative to the negative electrode capacity, which can cause lithium metal to be precipitated from the negative electrode during charging and discharging, forming lithium dendrites, and increasing the risk of battery short circuit and thermal runaway.

[0050] Therefore, by setting the difference L between the maximum thickness and the minimum thickness of the second active material layer 220 to be 5um≤L≤10um, the N / P value inside the battery can neither be too high nor too low, the energy density of the battery can be improved, and the consistency and reliability of the battery can be improved.

[0051] Further, with reference to Figure 2According to some embodiments of the present application, the second active material layer 220 comprises a first coating layer 221 and a second coating layer 222, wherein the first coating layer 221 is coated on the second foil 210, and the second coating layer 222 is coated on the first coating layer 221. The area density of the first coating layer 221 remains unchanged from the winding start end to the winding end, and the area density of the second coating layer 222 gradually increases. In addition to the above-mentioned manner, the second active material layer 220 can also be coated by two coating layers in two times, for example, the first coating layer 221 can be first coated on the second foil 210, and the first coating layer 221 is arranged to have uniform area density from the winding start end to the winding end, and then the second coating layer 222 is coated on the first coating layer 221, and the area density of the second coating layer 222 can gradually increase from the winding start end to the winding end.

[0052] It should be noted that, with reference to Figure 3 The second coating layer 222 coated on the first coating layer 221 can not start from the start end of the first coating layer 221, and can start from a position separated from the start end of the first coating layer 221 by a distance according to the required area density, so as to achieve the purpose of gradually increasing the area density of the second active material layer 220 from the winding start end to the winding end.

[0053] According to some embodiments of the present application, the thickness of the first coating layer 221 remains unchanged from the winding start end to the winding end of the negative plate 200, and the thickness of the second coating layer 222 gradually increases.

[0054] Specifically, the spraying mode of controlling the thickness of the first coating layer 221 to remain unchanged and the thickness of the second coating layer 222 to gradually increase can adopt the following mode:

[0055] Preparation of uniformly mixed slurry (active material), and transportation of the slurry to the spraying equipment, and setting of the preset plate area density parameters on the spraying equipment;

[0056] The spraying equipment starts to spray the slurry on the foil to form the first coating layer 221, and the transmission shaft controls the uniform transmission of the base material according to the preset area density and the slurry spraying amount (at this time, the area density and the slurry spraying amount are set as fixed values).

[0057] The spraying equipment starts to spray the slurry on the first coating layer 221 to form the second coating layer 222, and the transmission shaft controls the transmission speed of the base material according to the preset area density and the slurry spraying amount, and when the preset area density decreases, the transmission speed increases, and the spraying area density decreases.

[0058] After spraying is completed, the first coating layer 221 is formed into a structure of an approximate flat plate shape, and the second coating layer 222 is formed into a structure of an approximate trapezoidal shape, so that the thickness of the first coating layer 221 remains unchanged, and the thickness of the second coating layer 222 gradually increases.

[0059] Further, with reference toFigure 4 According to some embodiments of the present application, the second coating layer 222 comprises a plurality of discontinuous coating layers 212a, each of which is arranged at a spacing p. As described above, in addition to the continuous second coating layer 222 with gradually increasing thickness, a plurality of discontinuous coating layers 212a with gradually increasing thickness can also be provided. By arranging equal spacing p between each discontinuous coating layer 212a, the amount of active substance can be further reduced, and the manufacturing cost can be saved.

[0060] 1um≤p≤5um. The value of p is set to be between 1um and 5um, for example, 1um, 2um, 3um, 4um or 5um, etc. If the value of p is too large, the distribution of each discontinuous coating layer 212a will be too sparse, and each discontinuous coating layer 212a will not meet the required N / P value. If the value of p is too small, each discontinuous coating layer 212a will be combined together and form a flat surface under the action of surface tension, and cannot form a spaced state.

[0061] Further, with reference to Figure 5 According to some embodiments of the present application, the second active substance layer 220 comprises a first coating layer 221 and a second coating layer 222, wherein the first coating layer 221 is coated on the second foil 210, and the second coating layer 222 is coated on the first coating layer 221. The second coating layer 222 comprises a plurality of discontinuous coating layers 212a, each of which is arranged at a spacing p. The thickness of the discontinuous coating layer 212a remains unchanged, and the spacing p gradually decreases from the winding start end to the winding tail end. If the thickness of the first coating layer 221 and the thickness of the second coating layer 222 remain unchanged, the area density of the second coating layer 222 can be changed by changing the size of the spacing p of each discontinuous coating layer 212a. In this embodiment, the thickness of each discontinuous coating layer 212a remains unchanged, and the area density of the second coating layer 222 gradually increases from the winding start end to the winding tail end by gradually reducing the spacing p of each discontinuous coating layer 212a from the winding start end to the winding tail end (i.e., the discontinuous coating layers 212a are arranged more and more closely), that is, the area density of the second active substance layer 220 gradually increases from the winding start end to the winding tail end.

[0062] Further, with reference to Figure 6 According to some embodiments of the present application, the area density of the first active substance layer 120 gradually increases from the winding start end to the winding tail end of the positive electrode sheet 100. Now the specific situation of the positive electrode sheet 100 will be described. As known from the above, the single-sided coating area density of the positive and negative electrodes remains unchanged from the winding start end to the winding tail end, forming a flat plate coating. After forming the winding structure, the N / P value (ratio of positive and negative electrode sheet 200 gram capacity) of the inner circle layer at the winding start end of the negative electrode sheet 200 of the winding structure is relatively high, and the N / P value decreases as the number of winding increases.

[0063] The positive electrode sheet 100 is opposite to the negative electrode sheet 200, after forming the winding structure, the N / P value (the ratio of the positive and negative electrode sheet 200 gram capacity) of the inner layer of the winding start end of the positive electrode sheet 100 of the winding structure is low, as the number of winding increases, the N / P value increases. Therefore, the adjustment of the area density of the first active material layer 120 of the positive electrode sheet 100 is opposite to the adjustment of the area density of the second active material layer 220 of the negative electrode sheet 200, that is, the area density of the first active material layer 120 is gradually increased from the winding start end to the winding end.

[0064] Therefore, by appropriately increasing the area density of the active material of the negative electrode sheet 200 at the winding start end and appropriately reducing the thickness of the active material of the negative electrode sheet 200 at the winding end, the N / P value inside the battery can be made consistent as a whole. Through such adjustment, the N / P value inside the winding core can be balanced, the possibility of lithium precipitation in the N / P minimum region inside the winding core of the related art can be reduced, the use amount of active material in the N / P maximum region can be reduced, costs can be saved, the available space inside the battery can be increased, and thus the energy density of the battery can be improved.

[0065] In the present application, as an example, the positive electrode active material can include at least one of lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination with two or more. Among them, examples of lithium-containing phosphates can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (which can also be referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMN / PO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to as NCM523), LiNi 0.5 Co0. 25 Mn 0.25 O2 (which can also be referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2O2 (which can also be referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof.

[0066] Further, according to some embodiments of the present application, the thickness of the first active material layer 120 gradually increases from the winding start end to the winding tail end of the positive electrode sheet 100. As in the case of the negative electrode sheet 200, adjusting the area density of the first active material layer 120 can be achieved by adjusting the thickness of the first active material layer 120, or the adjustment of the area density of the first active material layer 120 can also be selected to be coated twice, similar to the negative electrode sheet 200, which will not be described here again, and can be referred to the setting of the negative electrode sheet 200.

[0067] Further, the battery according to the second aspect of the present application comprises the battery cell according to any one of the above.

[0068] The battery according to the present application has at least the following beneficial effects: in the battery cell of the present application, the area density of the second active material layer 220 connected to the second foil 210 gradually increases from the winding start end to the winding tail end of the winding structure. Therefore, by increasing and decreasing the area density of the active material in different regions of the negative electrode sheet 200, i.e. the area density of the active material coated at the winding start end is less than the area density of the active material coated at the winding tail end, and further avoiding the N / P value being too high at the winding start end (inner circle layer). Therefore, the battery with the above battery cell can effectively avoid the waste of active material of the negative electrode.

[0069] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. An electric cell, characterized by, The positive electrode sheet includes a first foil and a first active material layer connected to the first foil. The negative electrode sheet includes a second foil and a second active material layer connected to the second foil. The separator, the positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked and wound into a wound structure, and the face density of the second active material layer gradually increases from the winding start end to the winding end of the wound structure. The thickness of the second active material layer gradually increases from the winding start end to the winding end of the negative electrode sheet.

2. The electric cell of claim 1, wherein, The difference between the thickness of the winding start end of the second active material layer and the thickness of the winding end of the second active material layer is L, and 5 um≤L≤10 um.

3. The electric cell of claim 2, wherein, The second active material layer includes a first coating layer coated on the second foil and a second coating layer coated on the first coating layer.

4. The electric cell of claim 1, wherein, The face density of the first coating layer remains unchanged, and the face density of the second coating layer gradually increases from the winding start end to the winding end. The thickness of the first coating layer remains unchanged, and the thickness of the second coating layer gradually increases from the winding start end to the winding end of the negative electrode sheet.

5. The electric cell of claim 4, wherein, The second coating layer includes a plurality of intermittent coating layers, and each intermittent coating layer is arranged with a spacing p.

6. The electric cell of claim 5, wherein, The second active material layer includes a first coating layer coated on the second foil and a second coating layer coated on the first coating layer.

7. The electric cell of claim 1, wherein, The second coating layer includes a plurality of intermittent coating layers, and each intermittent coating layer is arranged with a spacing p, the thickness of the intermittent coating layer remains unchanged, and the spacing p gradually decreases from the winding start end to the winding end. The face density of the first active material layer gradually increases from the winding start end to the winding end of the positive electrode sheet.

8. The electric cell of claim 1, wherein, The thickness of the first active material layer gradually increases from the winding start end to the winding end of the positive electrode sheet.

9. The electric cell of claim 8, wherein, The battery cell includes the battery cell of any one of claims 1-9.

10. A battery, characterized by ​

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