Battery cell, battery and battery cell manufacturing method

Abstract

The present invention provides a battery cell, a battery, and a battery cell manufacturing method. The battery cell includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a first positive electrode active material layer. The coating starting end of the first positive electrode active material layer is a positive electrode short head, and the coating ending end of the first positive electrode active material layer is a positive electrode short tail. The negative electrode sheet includes a negative electrode current collector and a first negative electrode active material layer. The coating starting end of the first negative electrode active material layer is a negative electrode short head, and the coating ending end of the negative electrode active material layer is a negative electrode short tail. The first negative electrode active material layer and the first positive electrode active material layer are arranged opposite each other, and the positive electrode short tail and the negative electrode short head are arranged correspondingly. The battery cell and battery cell manufacturing method of the present invention are conducive to reducing the risk of lithium plating in the battery cell and improving the performance of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell, a battery, and a method for manufacturing the battery cell. Background Art

[0002] During the charging process of a battery cell, lithium ions are deintercalated from the positive electrode and intercalated into the negative electrode. However, if an abnormal condition occurs and the deintercalated lithium ions cannot be intercalated into the negative electrode, the lithium ions will precipitate onto the surface of the negative electrode, forming a gray layer of material known as lithium plating. Lithium plating not only affects the performance of the battery cell, such as reducing its capacity, but also affects its safety.

[0003] In order to increase the capacity of the battery cell, the existing positive and negative electrode sheets are usually double-sided coated structures, that is, the active material layer is coated on both sides of the current collector, and a long film surface and a short film surface are formed. In addition, after coating, there is often a phenomenon that the tail of the film surface is thin, especially when the negative electrode is double-layer coated, the thinness of the tail of the film surface is more serious. When the existing conventional winding process is used to make a wound battery cell, the tail of the short negative electrode film surface will correspond to the tail of the short positive electrode film surface. Since the tail of the film surface is difficult to be thinned, the unit area capacity of the anode (negative electrode) in the area near the short negative electrode film surface is smaller than the unit area capacity of the cathode (positive electrode), that is, the CB value is less than 1, which leads to lithium deposition at the tail of the anode. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a battery cell with a low risk of lithium plating.

[0005] The present invention also provides a battery comprising the above-mentioned battery cell.

[0006] The present invention also provides a method for manufacturing the battery cell.

[0007] According to the first aspect of the present invention, the battery cell includes: a positive electrode sheet, including a positive electrode collector, a first positive electrode active material layer and a second positive electrode active material layer, the second positive electrode active material layer and the first positive electrode active material layer are respectively arranged on the two side surfaces of the positive electrode collector facing each other, the second positive electrode active material layer and the first positive electrode active material layer have the same extension direction, the length of the second positive electrode active material layer is greater than the length of the first positive electrode active material layer, the coating starting end of the first positive electrode active material layer is a positive electrode short head, and the coating ending end of the first positive electrode active material layer is a positive electrode short tail; a negative electrode sheet, including a negative electrode collector, a first negative electrode active material layer and a second negative electrode active material layer, the second negative electrode active material layer and the first A negative electrode active material layer is respectively arranged on the two side surfaces of the negative electrode collector facing each other, the second negative electrode active material layer and the first negative electrode active material layer have the same extension direction, the length of the second negative electrode active material layer is greater than the length of the first negative electrode active material layer, the coating starting end of the first negative electrode active material layer is the negative electrode short head, and the coating ending end of the first negative electrode active material layer is the negative electrode short tail, the positive electrode sheet and the negative electrode sheet are stacked on each other, and the first negative electrode active material layer and the first positive electrode active material layer are arranged facing each other; the positive electrode short tail and the negative electrode short head are arranged correspondingly, the ratio of the capacity of the negative electrode short head to the capacity of the positive electrode short tail is greater than 1, and the ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is greater than 1.

[0008] The battery cell according to the first embodiment of the present invention has at least the following beneficial effects: Figure 1 In the present application, the amount of the positive electrode active material and the amount of the negative electrode active material near the negative electrode short tail are not easy to control. Figure 2 B area), the amount of positive electrode active material is easily controlled within the required range, and the present application reduces the uncontrollable factors near the negative electrode short tail. Compared with the prior art, the present embodiment enhances the controllability of the amount of positive electrode active material near the negative electrode short tail by changing the position of the positive electrode short head and the positive electrode short tail, thereby reducing the uncontrollability of the ratio of negative electrode active material to positive electrode active material near the negative electrode short tail, and further reducing the risk of lithium plating at the negative electrode short tail. Moreover, the ratio of the capacity of the negative electrode short head to the capacity of the positive electrode short tail is greater than 1, and the ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is greater than 1. The amount of lithium ions that can be absorbed by the negative electrode is greater than the amount of lithium ions that can be precipitated by the positive electrode, and lithium plating is not easy to occur at the negative electrode.

[0009] According to some embodiments of the present invention, the first positive electrode active material layer includes a first thinned area, one side edge of which is the positive electrode short head, and the first negative electrode active material layer includes a second thinned area, one side edge of which is the negative electrode short tail.

[0010] According to some embodiments of the present invention, the coating starting end of the second positive electrode active material layer is the long end of the positive electrode, and the long end of the positive electrode is aligned with the short tail of the positive electrode; the coating starting end of the second negative electrode active material layer is the long end of the negative electrode, and the long end of the negative electrode is aligned with the short tail of the negative electrode.

[0011] According to some embodiments of the present invention, the coating end of the second positive electrode active material layer is the positive electrode long tail, and the positive electrode short head is aligned with the positive electrode long tail; the coating end of the second negative electrode active material layer is the negative electrode long tail, and the negative electrode long tail is aligned with the negative electrode short head.

[0012] A battery according to an embodiment of the second aspect of the present invention includes the battery cell described in the embodiment of the first aspect.

[0013] The beneficial effects of the battery of the second embodiment are the same as the beneficial effects of the battery cell of the first embodiment, and are not described again here.

[0014] According to the third aspect of the present invention, the battery cell manufacturing method includes the following steps: manufacturing a positive electrode sheet, wherein the positive electrode sheet includes a positive electrode collector, a first positive electrode active material layer and a second positive electrode active material layer, the second positive electrode active material layer and the first positive electrode active material layer are respectively arranged on the two side surfaces of the positive electrode collector facing each other, the second positive electrode active material layer and the first positive electrode active material layer have the same extension direction, the length of the second positive electrode active material layer is greater than the length of the first positive electrode active material layer, the coating starting end of the first positive electrode active material layer is a positive electrode short head, and the coating ending end of the first positive electrode active material layer is a positive electrode short tail; manufacturing a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode collector, a first negative electrode active material layer and a second negative electrode active material layer , the second negative electrode active material layer and the first negative electrode active material layer are respectively arranged on the two side surfaces of the negative electrode collector facing each other, the second negative electrode active material layer and the first negative electrode active material layer have the same extension direction, the length of the second negative electrode active material layer is greater than the length of the first negative electrode active material layer, the coating starting end of the first negative electrode active material layer is the negative electrode short head, and the coating ending end of the first negative electrode active material layer is the negative electrode short tail, and the ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is greater than 1; the positive electrode sheet and the negative electrode sheet are stacked, and so that: the first negative electrode active material layer and the first positive electrode active material layer are arranged facing each other, the positive electrode short tail and the negative electrode short head are arranged correspondingly, and the positive electrode short head and the negative electrode short tail are arranged correspondingly.

[0015] The battery cell manufacturing method according to the third embodiment of the present invention has at least the following beneficial effects: the battery cell described in the first embodiment can be manufactured by this method.

[0016] According to some embodiments of the present invention, the steps of manufacturing the positive electrode sheet include: coating on the first surface of the positive electrode current collector to form a second positive electrode active material layer, the coating starting end of the second positive electrode active material layer is the positive electrode long head, the coating ending end of the second positive electrode active material layer is the positive electrode long tail, and the direction from the positive electrode long head to the positive electrode long tail is the first direction; coating along the second direction on the second surface of the positive electrode current collector to form the first positive electrode active material layer, the length of the first positive electrode active material layer is less than the length of the second positive electrode active material layer, the coating ending end of the first positive electrode active material layer is the positive electrode short tail, and the positive electrode short tail is aligned with the positive electrode long head; wherein, the first surface and the second surface are arranged back to back to each other, and the first direction is opposite to the second direction.

[0017] According to some embodiments of the present invention, the steps of manufacturing the negative electrode sheet include: coating on the third surface of the negative electrode current collector to form a second negative electrode active material layer, the coating starting end of the second negative electrode active material layer is the negative electrode long head, the coating ending end of the second negative electrode active material layer is the negative electrode long tail, and the direction from the negative electrode long head to the negative electrode long tail is the third direction; coating along the fourth direction on the fourth surface of the negative electrode current collector to form the first negative electrode active material layer, the length of the first negative electrode active material layer is less than the length of the second negative electrode active material layer, the coating ending end of the first negative electrode active material layer is the negative electrode short tail, and the negative electrode short tail is aligned with the negative electrode long head; wherein, the third surface and the fourth surface are arranged back to back to each other, and the third direction is opposite to the fourth direction.

[0018] According to some embodiments of the present invention, the steps of manufacturing the positive electrode sheet include: coating on the first surface of the positive electrode current collector to form a second positive electrode active material layer, the coating starting end of the second positive electrode active material layer is the positive electrode long head, the coating ending end of the second positive electrode active material layer is the positive electrode long tail, and the direction from the positive electrode long head to the positive electrode long tail is the first direction; coating along the second direction on the second surface of the positive electrode current collector to form the first positive electrode active material layer, the length of the first positive electrode active material layer is less than the length of the second positive electrode active material layer, the coating starting end of the first positive electrode active material layer is the positive electrode short head, and the positive electrode short head is aligned with the positive electrode long tail; wherein, the first surface and the second surface are arranged back to back to each other, and the first direction is opposite to the second direction.

[0019] According to some embodiments of the present invention, the steps of manufacturing the negative electrode sheet include: coating on the third surface of the negative electrode current collector to form a second negative electrode active material layer, the coating starting end of the second negative electrode active material layer is the negative electrode long head, the coating ending end of the second negative electrode active material layer is the negative electrode long tail, and the direction from the negative electrode long head to the negative electrode long tail is the third direction; coating along the fourth direction on the fourth surface of the negative electrode current collector to form the first negative electrode active material layer, the length of the first negative electrode active material layer is less than the length of the second negative electrode active material layer, the coating starting end of the first negative electrode active material layer is the negative electrode short head, and the negative electrode short head is aligned with the negative electrode long tail; wherein, the third surface and the fourth surface are arranged back to back to each other, and the third direction is opposite to the fourth direction.

[0020] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0022] Figure 1 Schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell in the prior art;

[0023] Figure 2 Schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell in the first embodiment of the present invention;

[0024] Figure 3 Schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell in the second embodiment of the present invention;

[0025] Figure 4 A graph showing the battery capacity retention rate of the battery cells of the present invention and the prior art;

[0026] Figure 5 A graph showing thickness changes of battery cells according to the present invention and the prior art;

[0027] Figure 6 is a schematic cross-sectional view of a battery cell according to an embodiment of the present invention;

[0028] Figure 7 Schematic cross-sectional view of a battery cell according to another embodiment of the present invention.

[0029] Reference numerals:

[0030] 100-battery cell, 101-positive electrode sheet, 102-negative electrode sheet, 103-insulating separator;

[0031] 201-positive electrode current collector, 202-second positive electrode active material layer, 203-first positive electrode active material layer, 204-positive electrode long head, 205-positive electrode long tail, 206-positive electrode short head, 207-positive electrode short tail, 208-positive electrode ear welding groove, 209-first surface, 210-second surface, 211-first thinned area, 212-third thinned area, 213-first slot, 214-second slot;

[0032] 301-negative electrode current collector, 302-second negative electrode active material layer, 303-first negative electrode active material layer, 304-negative electrode long head, 305-negative electrode long tail, 306-negative electrode short head, 307-negative electrode short tail, 308-negative electrode ear welding groove, 309-third surface, 310-fourth surface, 311-second thinning area, 312-third slot, 313-fourth slot. DETAILED DESCRIPTION

[0033] The following describes embodiments of the present invention in detail. 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 intended only to explain the present invention and are not to be construed as limiting the present invention.

[0034] In the description of the present invention, it should be understood that descriptions involving orientations, 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. They 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. Therefore, they cannot be understood as limitations on the present invention.

[0035] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0036] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting 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] Figure 1The figure shows the positive electrode sheet 101 and negative electrode sheet 102 of a battery cell 100 in the prior art. The positive electrode sheet 101 includes a positive current collector 201 and two positive active material layers extending in the same direction: a second positive active material layer 202 and a first positive active material layer 203. The positive current collector 201 includes a first surface 209 and a second surface 210 facing each other. The second positive active material layer 202 is disposed on the first surface 209, and the first positive active material layer 203 is disposed on the second surface 210. The second positive active material layer 202 is longer than the first positive active material layer 203. The second positive active material layer 202 and the first positive active material layer 203 are provided with positive tab welding grooves 208 for accommodating positive tabs. The negative electrode sheet 102 includes a negative electrode current collector 301 and two negative electrode active material layers extending in the same direction. The two negative electrode active material layers include a second negative electrode active material layer 302 and a first negative electrode active material layer 303. The negative electrode current collector 301 includes a third surface 309 and a fourth surface 310 facing each other. The second negative electrode active material layer 302 is disposed on the third surface 309, and the first negative electrode active material layer 303 is disposed on the fourth surface 310. The second negative electrode active material layer 302 and the first negative electrode active material layer 303 are provided with negative electrode tab welding grooves 308 for accommodating negative electrode tabs.

[0038] It should be noted that Figures 1 to 3 The battery cell 100 shown is actually a wound battery cell 100, but Figures 1 to 3 The positive electrode sheet 101 and the negative electrode sheet 102 are in a state before being wound, and both the positive electrode sheet 101 and the negative electrode sheet 102 are in a flattened state.

[0039] like Figure 1 As shown, the first positive electrode active material layer 203 and the first negative electrode active material layer 303 are arranged opposite each other. The starting end of coating the first positive electrode active material layer 203 is the positive electrode short head 206, and the ending end of coating the first positive electrode active material layer 203 is the positive electrode short tail 207. The starting end of coating the first negative electrode active material layer 303 is the negative electrode short head 306, and the ending end of coating the first negative electrode active material layer 303 is the negative electrode short tail 307. The positive electrode short head 206 and the negative electrode short head 306 are arranged in correspondence, and the positive electrode short tail 207 and the negative electrode short tail 307 are arranged in correspondence.

[0040] The coating start point of the active material layer refers to the position where the active material slurry used to form the active material layer first falls on the positive electrode current collector 201. The coating end point of the active material layer refers to the position where the active material slurry used to form the active material layer last falls on the positive electrode current collector 201.

[0041] From another perspective, since the coating of the active material slurry is achieved through a coating head, the coating starting end of the active material layer can also be understood as: the position where the active material layer first passes through the coating head; similarly, the coating ending end of the active material layer can also be understood as: the position where the active material layer last passes through the coating head.

[0042] The applicant has found that compared with the thickness of the active material layer at the coating starting end, the thickness of the active material layer at the coating ending end is more difficult to control within a preset thickness range. During the coating process of the electrode, the thinning of the coating starting end can be controlled by parameters such as the gasket of the coating head, the pump speed of the pump for conveying the slurry, and the distance between the coating head and the electrode, but the thinning of the coating ending end cannot be controlled by these parameters. When the coating head reaches the coating ending end, the slurry at the coating head will stop flowing out, and then under the action of the gravity of the slurry itself, the slurry at the coating ending end will flow to the surroundings. The randomness of the leveling effect is relatively large, which makes the thickness of the coating ending end difficult to control. Therefore, the thickness of the negative electrode short tail 307 and the positive electrode short tail 207 is actually not easy to be controlled within the preset size.

[0043] To reduce the risk of lithium plating, the ratio of the negative electrode active material to the positive electrode active material in the battery cell 100 needs to be maintained within an appropriate range (usually between 1 and 1.05). The amount of active material layer is related to the thickness of the active material layer. Difficulty controlling the thickness at the coating end means that the amount of active material near the coating end is also difficult to control. Figure 1 The negative electrode short tail 307 and the positive electrode short tail 207 are set correspondingly. In fact, the thickness of the negative electrode short tail 307 and the positive electrode short tail 207 is not easy to be controlled within the preset size. Therefore, near the negative electrode short tail 307 ( Figure 1 In the middle A area), the ratio of negative electrode active material to positive electrode active material is difficult to control, and this ratio is likely to exceed a reasonable range, resulting in a higher risk of lithium plating near the negative electrode short tail 307.

[0044] Figure 2 FIG1 shows a battery cell 100 according to a first embodiment of the present invention. The battery cell 100 according to this embodiment is conducive to solving the above technical problems. Figure 2As shown, in the first embodiment, the negative electrode shorting head 306 is provided corresponding to the positive electrode shorting tail 207, and the negative electrode shorting tail 307 is provided corresponding to the positive electrode shorting head 206. It should be noted that the battery cell 100 further includes a separator not shown in the drawings. The separator is insulating and is provided between the positive electrode sheet 101 and the negative electrode sheet 102 to prevent the positive electrode sheet 101 and the negative electrode sheet 102 from direct contact and short circuit. In the present invention, the corresponding arrangement of the negative electrode short head 306 and the positive electrode short tail 207 means that the negative electrode short head 306 and the positive electrode short tail 207 are both located on the same side of the positive electrode ear welding groove 208 (for example, both are located on the left side), and the corresponding arrangement of the negative electrode short tail 307 and the positive electrode short head 206 means that the negative electrode short tail 307 and the positive electrode short head 206 are both located on the same side of the positive electrode ear welding groove 208 (for example, both are located on the right side); and, the negative electrode short head 306 and the negative electrode short tail 307 are respectively located on different sides of the negative electrode ear welding groove 308, and the positive electrode short head 206 and the positive electrode short tail 207 are respectively located on different sides of the positive electrode ear welding groove 208.

[0045] In the prior art (such as Figure 1 In the first embodiment, the amount of the positive electrode active material and the amount of the negative electrode active material near the negative electrode short tail 307 are not easy to control. Figure 2 The amount of the positive electrode active material can be easily controlled within the required range, and this embodiment reduces the uncontrollable factors at the negative electrode short tail 307. Figure 1 Compared with the prior art shown in FIG, this embodiment enhances the controllability of the amount of positive electrode active material near the negative electrode short tail 307 by changing the positions of the positive electrode short head 206 and the positive electrode short tail 207, thereby reducing the uncontrollability of the ratio of the negative electrode active material to the positive electrode active material near the negative electrode short tail 307, and further reducing the risk of lithium plating at the negative electrode short tail 307.

[0046] In addition, the ratio of the capacity of the negative electrode short head 306 to the capacity of the positive electrode short tail 207 is greater than 1, and the ratio of the capacity of the negative electrode short tail 307 to the capacity of the positive electrode short head 206 is greater than 1. In this way, the amount of lithium ions that the negative electrode can absorb is greater than the amount of lithium ions that can be released by the positive electrode, and lithium deposition is less likely to occur at the negative electrode. Among them, the capacity of the positive electrode short head 206 is P1, the capacity of the positive electrode short tail 207 is P2, the capacity of the negative electrode short head 306 is N1, and the capacity of the negative electrode short tail 307 is N2, N1 / P2>1, N2 / P1>1. At the positive electrode short head 206, the product of the gram capacity of the positive electrode active material, the density of the positive and negative electrode active materials, and the positive electrode active material content ratio is equal to P1; at the positive electrode short tail 207, the product of the gram capacity of the positive electrode active material, the density of the positive and negative electrode active materials, and the positive electrode active material content ratio is equal to P2. At the negative electrode short end 306, the product of the gram capacity of the negative electrode active material, the density of the negative electrode active material, and the negative electrode active material content ratio is equal to N1. At the negative electrode short end 307, the product of the gram capacity of the negative electrode active material, the density of the negative electrode active material, and the negative electrode active material content ratio is equal to N2. Furthermore, to prevent excessive cathode (positive electrode) capacity from causing material waste and cathode instability, the above capacity ratios can also meet the following requirements: 1 < N1 / P2 < 1.1, and 1 < N2 / P1 < 1.1.

[0047] like Figure 2 As shown, in order to achieve the above capacity ratio, in the first embodiment, the first positive electrode active material layer 203 includes a first thinned area 211, one side edge of the first thinned area 211 is the positive electrode short head 206, the first negative electrode active material layer 303 includes a second thinned area 311, one side edge of the second thinned area 311 is the negative electrode short tail 307, and the minimum thickness of the first thinned area 211 is less than the minimum thickness of the second thinned area 311. Figure 2 At the angle shown, the first thinned area 211 and the second thinned area 311 are both trapezoidal. This arrangement is beneficial to reducing the amount of positive electrode active material near the negative electrode short tail 307, thereby reducing the amount of lithium ions migrating to the negative electrode short tail 307 per unit time, thereby reducing the risk of lithium plating of the negative electrode short tail 307. Figure 2 As shown, in some embodiments, in order to reduce the capacity of the cathode (positive electrode) and thus reduce the risk of lithium plating, the second positive electrode active material layer 202 includes a third thinned area 212 , one side edge of the third thinned area 212 being the positive electrode long head 204 .

[0048] like Figure 2As shown, in some embodiments, the electrode sheet adopts a central tab design to reduce the difference in the electron gain and loss rates between different regions of the active material layer, fully utilize the performance of each region of the active material layer, and thus improve the charge and discharge rate of the battery cell. Specifically, the first positive active material layer 203 has a first slot 213, with the positive electrode short head 206 and the positive electrode short tail 207 located on either side of the first slot 213. The second positive active material layer 202 has a second slot 214, with the first slot 213 and the second slot 214 arranged back to back, and the positive electrode long head 204 and the positive electrode long tail 205 located on either side of the second slot 214. One of the first slot 213 and the second slot 214 serves as the positive tab welding slot 208. The first negative active material layer 303 has a third slot 312, with the negative electrode short head 306 and the negative electrode short tail 307 located on either side of the third slot 312. The second negative electrode active material layer 302 is provided with a fourth slot 313. The third slot 312 and the fourth slot 313 are arranged back to back. The negative electrode long head 304 and the negative electrode long tail 305 are respectively arranged on either side of the fourth slot 313. One of the third slot 312 and the fourth slot 313 serves as a negative electrode tab welding slot 308.

[0049] The present invention also provides a method for manufacturing a battery cell, which is used to manufacture the battery cell 100 mentioned in the present invention. The manufacturing method comprises the following steps:

[0050] S10: manufacturing a positive electrode sheet 101, wherein the manufactured positive electrode sheet 101 includes a positive electrode current collector 201, a first positive electrode active material layer 203, and a second positive electrode active material layer 202, wherein the second positive electrode active material layer 202 and the first positive electrode active material layer 203 are respectively arranged on two opposite surfaces of the positive electrode current collector 201, the second positive electrode active material layer 202 and the first positive electrode active material layer 203 extend in the same direction, the length of the second positive electrode active material layer 202 is greater than the length of the first positive electrode active material layer 203, the coating starting end of the first positive electrode active material layer 203 is a positive electrode short head 206, and the coating ending end of the first positive electrode active material layer 203 is a positive electrode short tail 207;

[0051] S20: manufacturing a negative electrode sheet 102, wherein the manufactured negative electrode sheet 102 includes a negative electrode current collector 301, a first negative electrode active material layer 303, and a second negative electrode active material layer 302, wherein the second negative electrode active material layer 302 and the first negative electrode active material layer 303 are respectively arranged on two opposite surfaces of the negative electrode current collector 301, the second negative electrode active material layer 302 and the first negative electrode active material layer 303 extend in the same direction, the length of the second negative electrode active material layer 302 is greater than the length of the first negative electrode active material layer 303, the coating starting end of the first negative electrode active material layer 303 is the negative electrode short head 306, and the coating ending end of the first negative electrode active material layer 303 is the negative electrode short tail 307, and the ratio of the capacity of the negative electrode short tail 307 to the capacity of the positive electrode short tail 207 is greater than 1;

[0052] S30: stacking the positive electrode sheet 101 and the negative electrode sheet 102 so that: the first negative electrode active material layer 303 is arranged opposite to the first positive electrode active material layer 203, the positive electrode short tail 207 and the negative electrode short head 306 are arranged correspondingly, and the positive electrode short head 206 and the negative electrode short tail 307 are arranged correspondingly.

[0053] Figure 3 The diagram shows the positive electrode sheet 101 and negative electrode sheet 102 of a battery cell 100 according to a second embodiment of the present invention. In the first embodiment, the positive electrode short tail 207, the negative electrode terminal, the positive electrode short tail 206, and the negative electrode short tail 307 are sequentially spaced from left to right. In the second embodiment, the positive electrode short tail 206, the negative electrode short tail 307, the positive electrode short tail 207, and the negative electrode terminal are sequentially spaced from left to right. The second embodiment also satisfies the following requirements: the negative electrode short tail 306 is provided in correspondence with the positive electrode short tail 207, and the negative electrode short tail 307 is provided in correspondence with the positive electrode short tail 206. The battery cell 100 according to the second embodiment has a lower risk of lithium plating.

[0054] like Figure 2 As shown, in the first embodiment, the positive electrode long end 204 is aligned with the positive electrode short end 207, and the negative electrode long end 304 is aligned with the negative electrode short end 307. The starting end of coating the second positive electrode active material layer 202 is the positive electrode long end 204, and the ending end of coating the second positive electrode active material layer 202 is the positive electrode long end 205. The starting end of coating the second negative electrode active material layer 302 is the negative electrode long end 304, and the ending end of coating the second negative electrode active material layer 302 is the negative electrode long end 305. As described above, the thickness of the active material layer at the starting end of coating is easier to control. Therefore, the thickness of the positive electrode long end 204 and the thickness of the negative electrode long end 304 are relatively easy to control within an acceptable error range. This arrangement helps to improve the controllability of the electrode thickness, thereby preventing the electrode from being locally too thick or too thin.

[0055] If the manufacturing method is used to manufacture the battery cell 100 of the first embodiment, the steps of manufacturing the positive electrode sheet 101 include:

[0056] S11: coating the first surface 209 of the positive electrode current collector 201 to form a second positive electrode active material layer 202, with the direction from the positive electrode long head 204 to the positive electrode long tail 205 being a first direction;

[0057] S12 : coating the second surface 210 along the second direction to form a first positive active material layer 203 , wherein the length of the first positive active material layer 203 is smaller than that of the second positive active material layer 202 , and the positive short tail 207 is aligned with the positive long head 204 .

[0058] The first surface 209 and the second surface 210 are arranged back to back with each other, and the first direction is opposite to the second direction.

[0059] If the manufacturing method is used to manufacture the battery cell 100 of the first embodiment, the steps of manufacturing the negative electrode sheet 102 include:

[0060] S21: coating the third surface 309 of the negative electrode current collector 301 to form a second negative electrode active material layer 302 , wherein the direction from the negative electrode long head 304 to the negative electrode long tail 305 is the third direction;

[0061] S22 : coating along a fourth direction on the fourth surface 310 to form a first negative electrode active material layer 303 . The length of the first negative electrode active material layer 303 is shorter than that of the second negative electrode active material layer 302 . The negative electrode short tail 307 is aligned with the negative electrode long head 304 .

[0062] The third surface 309 and the fourth surface 310 are arranged back to back with each other, and the third direction is opposite to the fourth direction.

[0063] like Figure 3 As shown, in the second embodiment, the positive electrode short head 206 is aligned with the positive electrode long tail 205, and the negative electrode long tail 305 is aligned with the negative electrode short head 306. This arrangement is also intended to improve the controllability of the thickness of the electrode sheet.

[0064] If the manufacturing method is used to manufacture the battery cell 100 of the second embodiment, the steps of manufacturing the positive electrode sheet 101 include:

[0065] S13: coating the first surface 209 of the positive electrode current collector 201 to form a second positive electrode active material layer 202, with the direction from the positive electrode long head 204 to the positive electrode long tail 205 being the first direction;

[0066] S14 : coating the second surface 210 along the second direction to form a first positive active material layer 203 . The length of the first positive active material layer 203 is smaller than that of the second positive active material layer 202 , and the positive short head 206 is aligned with the positive long tail 205 .

[0067] If the manufacturing method is used to manufacture the battery cell 100 of the second embodiment, the steps of manufacturing the negative electrode sheet 102 include:

[0068] S23: coating the third surface 309 of the negative electrode current collector 301 to form a second negative electrode active material layer 302 , with the direction from the negative electrode long head 304 to the negative electrode long tail 305 being the third direction;

[0069] S24 : coating along a fourth direction on the fourth surface 310 to form a first negative electrode active material layer 303 . The length of the first negative electrode active material layer 303 is shorter than that of the second negative electrode active material layer 302 , and the short end is aligned with the long negative electrode tail 305 .

[0070] The above describes the structure of the electrode when it is flattened. The following describes the actual situation of the electrode in the battery cell 100. Figure 6 The battery cell 100 of one embodiment of the present invention is shown. The battery cell 100 is a wound battery cell. The battery cell 100 includes a positive electrode sheet 101, a negative electrode sheet 102, and an insulating separator 103. The insulating separator 103 separates the positive electrode sheet 101 and the negative electrode sheet 102. The positive electrode sheet 101, the negative electrode sheet 102, and the insulating separator 103 are stacked on each other and wound together. Figure 6 As shown, the negative electrode long tail 305 and the negative electrode short head 306 are located in the central area of ​​the battery cell 100 , and the positive electrode short head 206 and the positive electrode long tail 205 are located in the peripheral area of ​​the battery cell 100 . Figure 7 FIG. 1 shows a battery cell 100 according to another embodiment of the present invention. Figure 7 As shown, the negative electrode long head 304 and the negative electrode short tail 307 are located in the central area of ​​the battery cell 100 , and the positive electrode short tail 207 and the positive electrode long head 204 are located in the peripheral area of ​​the battery cell 100 .

[0071] The battery cell 100 in any of the above embodiments can be used in a battery. The battery includes the battery cell 100 and a housing, with the battery cell 100 disposed within the housing. The housing can be a hard shell made of aluminum, steel, or other metal material, or a soft shell made of aluminum-plastic film.

[0072] Figure 4 The performance of the battery cell 100 of the present application and the battery cell 100 in the prior art are shown. Figure 4 The figure shows the relationship between the capacity retention and the number of cycles for the battery cell 100. The test method for the battery cell 100 is as follows: the battery cell 100 is charged at 3.5C constant current and constant voltage to 4.30V, with a cut-off rate of 2.7C; then charged at 2.7C constant current and constant voltage to 4.40V, with a cut-off rate of 1.8C; then charged at 1.8C constant current and constant voltage to 4.53V, with a cut-off rate of 1.5C; and finally charged at 1.5C constant current and constant voltage to 4.58V, with a cut-off rate of 0.129C. This constitutes one cycle, which was repeated 800 times.

[0073] exist Figure 4 The horizontal axis is the number of cycles of the battery cell 100, and the vertical axis is the capacity retention rate. The black curve of "unchanged" refers to Figure 1 The curve of the battery cell 100 shown in FIG. 1 is the curve of the battery cell 100 of the second embodiment, the green curve of “changing the anode” is the curve of the battery cell 100 of the second embodiment, and the red curve of “changing the cathode” is the curve of the battery cell 100 of the first embodiment. Figure 4 It can be seen that as the number of cycles of the battery cell 100 increases, the capacity of the battery cell 100 of the prior art decreases rapidly, while the capacity of the battery cell 100 of the present application decreases more slowly. After 600 cycles, the battery cell 100 of the present application can still retain approximately 90% of its capacity. Therefore, the capacity of the battery cell 100 decreases more slowly, and the battery cell 100 of the present application has better performance.

[0074] exist Figure 5 In the figure, the horizontal axis is the number of cycles of the battery cell 100, and the vertical axis is the thickness rebound. The black points of "unchanged" are Figure 1 The data of the battery cell 100 shown in FIG. 1 are the data of the battery cell 100 of the second embodiment. The green points of “changing the anode” are the data of the battery cell 100 of the second embodiment. The red points of “changing the cathode” are the data of the battery cell 100 of the first embodiment. Figure 5 It can be seen that as the number of cycles of the battery cell 100 increases, the thickness rebound of the battery cell 100 of the present application increases slowly. Therefore, the performance of the battery cell 100 of the present application is better.

[0075] In the description of the present invention, reference to terms such as "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 present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Claims

1. A wound cell, characterized in that: include: A positive electrode sheet comprising a positive electrode current collector, a first positive electrode active material layer, and a second positive electrode active material layer, wherein the second positive electrode active material layer and the first positive electrode active material layer are respectively arranged on opposite sides of the positive electrode current collector, the second positive electrode active material layer and the first positive electrode active material layer extend in the same direction, the second positive electrode active material layer is longer than the first positive electrode active material layer, the coating starting end of the first positive electrode active material layer is a positive electrode short head, and the coating ending end of the first positive electrode active material layer is a positive electrode short tail; A negative electrode sheet, comprising a negative electrode current collector, a first negative electrode active material layer, and a second negative electrode active material layer, wherein the second negative electrode active material layer and the first negative electrode active material layer are respectively arranged on opposite sides of the negative electrode current collector, the second negative electrode active material layer and the first negative electrode active material layer extend in the same direction, the length of the second negative electrode active material layer is greater than the length of the first negative electrode active material layer, the coating starting end of the first negative electrode active material layer is a negative electrode short head, and the coating ending end of the first negative electrode active material layer is a negative electrode short tail, the positive electrode sheet and the negative electrode sheet are stacked on each other, and the first negative electrode active material layer and the first positive active material layer are arranged facing each other; The positive short tail and the negative short head are arranged correspondingly, the positive short head and the negative short tail are arranged correspondingly, the ratio of the capacity of the negative short head to the capacity of the positive short tail is greater than 1 and less than 1.1, and the ratio of the capacity of the negative short tail to the capacity of the positive short head is greater than 1 and less than 1.

1.

2. The wound battery cell according to claim 1, characterized in that The first positive electrode active material layer includes a first thinned area, one side edge of which is the positive electrode short head, and the first negative electrode active material layer includes a second thinned area, one side edge of which is the negative electrode short tail.

3. The wound battery cell according to claim 1, characterized in that The coating starting end of the second positive active material layer is the positive electrode long end, which is aligned with the positive electrode short tail. The coating starting end of the second negative active material layer is the negative electrode long end, which is aligned with the negative electrode short tail.

4. The wound battery cell according to claim 1, wherein: The coating end of the second positive active material layer is the positive electrode long tail, and the positive electrode short head is aligned with the positive electrode long tail. The coating end of the second negative active material layer is the negative electrode long tail, and the negative electrode long tail is aligned with the negative electrode short head.

5. A battery, characterized in that The invention comprises the wound battery cell according to any one of claims 1 to 4.

6. A method for manufacturing a wound battery cell, characterized in that: The following steps are involved: Manufacturing a positive electrode sheet, the prepared positive electrode sheet comprising a positive electrode current collector, a first positive electrode active material layer, and a second positive electrode active material layer, wherein the second positive electrode active material layer and the first positive electrode active material layer are respectively disposed on opposite sides of the positive electrode current collector, the second positive electrode active material layer and the first positive electrode active material layer extend in the same direction, the second positive electrode active material layer is longer than the first positive electrode active material layer, the coating starting end of the first positive electrode active material layer is a positive electrode short head, and the coating ending end of the first positive electrode active material layer is a positive electrode short tail; Manufacturing a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector, a first negative electrode active material layer, and a second negative electrode active material layer, wherein the second negative electrode active material layer and the first negative electrode active material layer are respectively disposed on opposite sides of the negative electrode current collector, the second negative electrode active material layer and the first negative electrode active material layer extend in the same direction, the second negative electrode active material layer is longer than the first negative electrode active material layer, the coating starting end of the first negative electrode active material layer is a negative electrode short head, the coating ending end of the first negative electrode active material layer is a negative electrode short tail, the ratio of the capacity of the negative electrode short head to the capacity of the positive electrode short tail is greater than 1 and less than 1.1, and the ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is greater than 1 and less than 1.1; The positive electrode sheet and the negative electrode sheet are stacked so that: the first negative electrode active material layer is arranged opposite to the first positive electrode active material layer, the positive electrode short tail and the negative electrode short head are arranged correspondingly, and the positive electrode short head and the negative electrode short tail are arranged correspondingly.

7. The method for manufacturing a wound battery cell according to claim 6, wherein: The steps of manufacturing the positive electrode sheet include: Coating a second positive electrode active material layer on the first surface of the positive electrode current collector to form a second positive electrode active material layer, wherein the coating starting end of the second positive electrode active material layer is the positive electrode long head, the coating ending end of the second positive electrode active material layer is the positive electrode long tail, and the direction from the positive electrode long head to the positive electrode long tail is the first direction; coating the first positive electrode active material layer on the second surface of the positive electrode current collector along a second direction to form the first positive electrode active material layer, wherein the length of the first positive electrode active material layer is shorter than the length of the second positive electrode active material layer, and the coating end of the first positive electrode active material layer is a positive electrode short tail, and the positive electrode short tail is aligned with the positive electrode long head; The first surface and the second surface are arranged back to back with each other, and the first direction is opposite to the second direction.

8. The method for manufacturing a wound battery cell according to claim 7, wherein: The steps of manufacturing the negative electrode sheet include: coating the third surface of the negative electrode current collector to form a second negative electrode active material layer, wherein the coating starting end of the second negative electrode active material layer is the negative electrode long head, the coating ending end of the second negative electrode active material layer is the negative electrode long tail, and the direction from the negative electrode long head to the negative electrode long tail is the third direction; coating the first negative electrode active material layer on the fourth surface of the negative electrode current collector along a fourth direction to form the first negative electrode active material layer, wherein the length of the first negative electrode active material layer is shorter than the length of the second negative electrode active material layer, and the coating end of the first negative electrode active material layer is a negative electrode short tail, and the negative electrode short tail is aligned with the negative electrode long head; The third surface and the fourth surface are arranged back to back with each other, and the third direction is opposite to the fourth direction.

9. The method for manufacturing a wound battery cell according to claim 6, wherein: The steps of manufacturing the positive electrode sheet include: Coating a second positive electrode active material layer on the first surface of the positive electrode current collector to form a second positive electrode active material layer, wherein the coating starting end of the second positive electrode active material layer is the positive electrode long head, the coating ending end of the second positive electrode active material layer is the positive electrode long tail, and the direction from the positive electrode long head to the positive electrode long tail is the first direction; coating the first positive electrode active material layer on the second surface of the positive electrode current collector along a second direction to form the first positive electrode active material layer, wherein the length of the first positive electrode active material layer is shorter than the length of the second positive electrode active material layer, and the coating starting end of the first positive electrode active material layer is the positive electrode short end, and the positive electrode short end is aligned with the positive electrode long tail; The first surface and the second surface are arranged back to back with each other, and the first direction is opposite to the second direction.

10. The method for manufacturing a wound battery cell according to claim 9, wherein: The steps of manufacturing the negative electrode sheet include: coating the third surface of the negative electrode current collector to form a second negative electrode active material layer, wherein the coating starting end of the second negative electrode active material layer is the negative electrode long head, the coating ending end of the second negative electrode active material layer is the negative electrode long tail, and the direction from the negative electrode long head to the negative electrode long tail is the third direction; coating the first negative electrode active material layer on the fourth surface of the negative electrode current collector along a fourth direction to form the first negative electrode active material layer, wherein the length of the first negative electrode active material layer is shorter than the length of the second negative electrode active material layer, and the coating starting end of the first negative electrode active material layer is the negative electrode short end, and the negative electrode short end is aligned with the negative electrode long end; The third surface and the fourth surface are arranged back to back with each other, and the third direction is opposite to the fourth direction.

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