Cells and Batteries

Abstract

The utility model provides a battery cell and a battery, the battery cell comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a first positive electrode active material layer, the coating start end of the first positive electrode active material layer is a positive electrode short head, and the coating end end of the first positive electrode active material layer is a positive electrode short tail; the negative electrode sheet comprises a negative electrode current collector and a first negative electrode active material layer, the coating start end of the first negative electrode active material layer is a negative electrode short head, and the coating end 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 to 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. The battery cell of the utility model is conducive to reducing the risk of lithium plating of the battery cell and improving the performance of the battery cell.

Description

Technical Field

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

[0002] During the charging process of the battery cell, lithium ions will be deintercalated from the positive electrode and embedded in the negative electrode. However, when some abnormal conditions occur and the lithium ions deintercalated from the positive electrode cannot be embedded in the negative electrode, the lithium ions will precipitate on the surface of the negative electrode and form a layer of gray material, resulting in lithium precipitation. Lithium precipitation will not only affect the performance of the battery cell, such as causing the capacity of the battery cell to decrease, but also affect the safety of the battery cell.

[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-coated, the tail of the film surface is thinner. When the existing conventional winding process is used to make a wound battery cell, the tail of the short film surface of the negative electrode will correspond to the tail of the short film surface of the positive electrode. Since the tail of the film surface is not easy to be thinned, the unit area capacity of the anode (negative electrode) in the area near the short film surface of the negative electrode 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. Utility Model Content

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

[0005] The utility model also provides a battery comprising the battery core.

[0006] According to the first aspect of the utility model, the battery cell comprises: 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, 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 current 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, comprising a negative electrode current 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 The first negative electrode active material layer is respectively arranged on the two side surfaces of the negative electrode collector that are back to back to 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 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, 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.

[0007] The battery cell according to the first aspect of the present utility model has at least the following beneficial effects: Figure 1 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. In the present application, near the negative electrode short tail ( 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, thereby reducing the risk of lithium deposition 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 deposition is not easy to occur at the negative electrode.

[0008] 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.

[0009] According to some embodiments of the utility model, the coating starting end of the second positive electrode active material layer is the positive electrode long head, and the positive electrode long head is aligned with the positive electrode short tail. The coating starting end of the second negative electrode active material layer is the negative electrode long head, and the negative electrode long head is aligned with the negative electrode short tail.

[0010] 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.

[0011] According to some embodiments of the present invention, the ratio of the capacity of the negative electrode short head to the capacity of the positive electrode short tail is less than 1.1.

[0012] According to some embodiments of the present invention, the ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is less than 1.1.

[0013] According to some embodiments of the present invention, the minimum thickness of the first thinned area is smaller than the minimum thickness of the second thinned area.

[0014] According to some embodiments of the present invention, the second positive electrode active material layer includes a third thinned area, the coating starting end of the second positive electrode active material layer is the positive electrode long head, and one side edge of the third thinned area is the positive electrode long head.

[0015] According to some embodiments of the utility model, the first positive electrode active material layer is provided with a first slot, and the positive electrode short head and the positive electrode short tail are respectively located on both sides of the first slot; the second positive electrode active material layer is provided with a second slot, the first slot and the second slot are arranged back to back, 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 positive electrode long head and the positive electrode long tail are respectively arranged on both sides of the second slot; the first negative electrode active material layer is provided with a third slot, and the negative electrode short head and the negative electrode short tail are respectively located on both sides of the third slot; the second negative electrode active material layer is provided with a fourth slot, the third slot and the fourth slot are arranged back to back, 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 negative electrode long head and the negative electrode long tail are respectively arranged on both sides of the fourth slot.

[0016] The battery according to the embodiment of the second aspect of the utility model includes the battery cell described in the embodiment of the first aspect.

[0017] The beneficial effects of the battery of the second aspect embodiment are the same as the beneficial effects of the battery cell of the first aspect embodiment, and will not be described again here.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described below with reference to the accompanying drawings and embodiments, wherein:

[0020] Figure 1 A schematic diagram of a positive electrode sheet and a negative electrode sheet of a battery cell in the prior art;

[0021] Figure 2 It is a schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell in the first embodiment of the utility model;

[0022] Figure 3 It is a schematic diagram of the positive electrode sheet and the negative electrode sheet of the battery cell in the second embodiment of the utility model;

[0023] Figure 4 A graph showing the battery capacity retention rate of the battery cell of the utility model and the prior art;

[0024] Figure 5 A curve diagram showing the thickness change of the battery cell of the utility model and the prior art;

[0025] Figure 6 A schematic cross-sectional view of a battery cell according to an embodiment of the utility model;

[0026] Figure 7 It is a cross-sectional schematic diagram of a battery cell according to another embodiment of the utility model.

[0027] Reference numerals:

[0028] 100-battery cell, 101-positive electrode sheet, 102-negative electrode sheet, 103-insulating diaphragm;

[0029] 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 thinning area, 212-third thinning area, 213-first slot, 214-second slot;

[0030] 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

[0031] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] In the description of the present utility model, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0034] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0035] Figure 1The positive electrode sheet 101 and the negative electrode sheet 102 of the battery cell 100 in the prior art are shown. The positive electrode sheet 101 includes a positive electrode current collector 201 and two positive electrode active material layers extending in the same direction, and the two positive electrode active material layers are respectively a second positive electrode active material layer 202 and a first positive electrode active material layer 203. The positive electrode current collector 201 includes a first surface 209 and a second surface 210 facing each other, the second positive electrode active material layer 202 is arranged on the first surface 209, and the first positive electrode active material layer 203 is arranged on the second surface 210, and 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 second positive electrode active material layer 202 and the first positive electrode active material layer 203 are provided with a positive electrode ear welding groove 208, and the positive electrode ear welding groove 208 is used to accommodate the positive electrode ear. The negative electrode sheet 102 includes a negative electrode current collector 301 and two negative electrode active material layers extending in the same direction, and 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 arranged on the third surface 309, and the first negative electrode active material layer 303 is arranged 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 a negative electrode ear welding groove 308, and the negative electrode ear welding groove 308 is used to accommodate the negative electrode ear.

[0036] 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.

[0037] 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 to each other. The coating start end of the first positive electrode active material layer 203 is the positive electrode short head 206, and the coating end end of the first positive electrode active material layer 203 is the positive electrode short tail 207. The coating start end of the first negative electrode active material layer 303 is the negative electrode short head 306, and the coating end end of 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 correspondingly, and the positive electrode short tail 207 and the negative electrode short tail 307 are arranged correspondingly.

[0038] The coating start end 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 end of the active material layer refers to the position where the active material slurry used to form the active material layer finally falls on the positive electrode current collector 201.

[0039] 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.

[0040] The applicant has found that compared with the thickness of the active material layer at the starting end of coating, the thickness of the active material layer at the ending end of coating is more difficult to control within the preset thickness range. During the coating process of the electrode, the thinning at the starting end of coating can be controlled by parameters such as the gasket of the coating head, the pump speed of the pump used to transport the slurry, and the distance between the coating head and the electrode, but the thinning at the ending end of coating cannot be controlled by these parameters. When the coating head reaches the ending end of coating, 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 ending end of coating will flow to the surroundings. The randomness of the leveling effect is relatively large, which makes it difficult to control the thickness at the ending end of coating. 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.

[0041] In order to reduce the risk of lithium plating, the ratio of the negative electrode active material to the positive electrode active material of the battery cell 100 needs to be maintained within an appropriate range (usually between 1-1.05). The amount of the active material layer is related to the thickness of the active material layer. The difficulty in 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. 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. 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.

[0042] Figure 2 The battery cell 100 of the first embodiment of the utility model is shown, and the battery cell 100 of this embodiment is conducive to solving the above technical problems. Figure 2As shown, in the first embodiment, the negative electrode short head 306 is arranged correspondingly to the positive electrode short tail 207, and the negative electrode short tail 307 is arranged correspondingly to the positive electrode short head 206. It should be noted that the battery cell 100 also includes a diaphragm not shown in the drawings, the diaphragm is insulating, and the diaphragm is arranged between the positive electrode sheet 101 and the negative electrode sheet 102, so as to prevent the positive electrode sheet 101 and the negative electrode sheet 102 from directly contacting each other and short-circuiting. In the utility model, the corresponding arrangement of the negative short head 306 and the positive short tail 207 means that the negative short head 306 and the positive short tail 207 are both located on the same side of the positive ear welding groove 208 (for example, both are located on the left side), and the corresponding arrangement of the negative short tail 307 and the positive short head 206 means that the negative short tail 307 and the positive short head 206 are both located on the same side of the positive ear welding groove 208 (for example, both are located on the right side); and the negative short head 306 and the negative short tail 307 are respectively located on different sides of the negative ear welding groove 308, and the positive short head 206 and the positive short tail 207 are respectively located on different sides of the positive ear welding groove 208.

[0043] 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 the figure, 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.

[0044] 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 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 precipitation is not easy 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 head 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 tail 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. Further, in order to prevent the cathode (positive electrode) capacity from being too large, causing material waste and cathode instability, the above capacity ratios can also meet the following conditions: 1<N1 / P2<1.1, 1<N2 / P1<1.1.

[0045] 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 a 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 a 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 conducive 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 deposition in 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 , and one side edge of the third thinned area 212 is a positive electrode long head 204 .

[0046] like Figure 2As shown, in some embodiments, the pole piece adopts a design in which the pole ear is placed in the middle to reduce the difference between the electron gain and loss rates of each region of the active material layer, give full play to 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 is provided with a first slot 213, and the positive short head 206 and the positive short tail 207 are respectively located on both sides of the first slot 213. The second positive active material layer 202 is provided with a second slot 214, the first slot 213 and the second slot 214 are arranged back to back, and the positive long head 204 and the positive long tail 205 are respectively arranged on both sides of the second slot 214. One of the first slot 213 and the second slot 214 is used as a positive ear welding slot 208. The first negative active material layer 303 is provided with a third slot 312, and the negative short head 306 and the negative short tail 307 are respectively located on both sides 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, and the negative electrode long head 304 and the negative electrode long tail 305 are respectively arranged on both sides of the fourth slot 313. One of the third slot 312 and the fourth slot 313 is used as a negative electrode ear welding slot 308.

[0047] The utility model also provides a method for manufacturing a battery cell, which is used to manufacture the battery cell 100 mentioned in the utility model, and the manufacturing method comprises the following steps:

[0048] S10: manufacturing a positive electrode sheet 101, wherein the manufactured positive electrode sheet 101 comprises 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 sides 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 start end of the first positive electrode active material layer 203 is a positive electrode short head 206, and the coating end end of the first positive electrode active material layer 203 is a positive electrode short tail 207;

[0049] S20: manufacturing a negative electrode sheet 102, wherein the manufactured negative electrode sheet 102 comprises 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 sides 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 a negative electrode short head 306, the coating ending end of the first negative electrode active material layer 303 is a 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;

[0050] 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.

[0051] Figure 3 The positive electrode sheet 101 and the negative electrode sheet 102 of the battery cell 100 of the second embodiment of the utility model are shown. In the first embodiment, the positive electrode short tail 207, the negative electrode terminal head, the positive electrode short head 206 and the negative electrode short tail 307 are spaced from left to right in sequence; in the second embodiment, the positive electrode short head 206, the negative electrode short tail 307, the positive electrode short tail 207 and the negative electrode terminal head are spaced from left to right in sequence. The second embodiment also satisfies: the negative electrode short head 306 is arranged correspondingly to the positive electrode short tail 207, and the negative electrode short tail 307 is arranged correspondingly to the positive electrode short head 206. The battery cell 100 of the second embodiment has a lower risk of lithium plating.

[0052] like Figure 2 As shown, in the first embodiment, the positive electrode long head 204 is aligned with the positive electrode short tail 207, and the negative electrode long head 304 is aligned with the negative electrode short tail 307. Among them, the coating start end of the second positive electrode active material layer 202 is the positive electrode long head 204, the coating end end of the second positive electrode active material layer 202 is the positive electrode long tail 205, the coating start end of the second negative electrode active material layer 302 is the negative electrode long head 304, and the coating end end of the second negative electrode active material layer 302 is the negative electrode long tail 305. As mentioned above, the thickness of the coating start end of the active material layer is easier to control, so the thickness of the positive electrode long head 204 and the thickness of the negative electrode long head 304 are relatively easy to control within an acceptable error range. Such a setting is conducive to improving the controllability of the thickness of the electrode sheet to prevent the electrode sheet from being too thick or too thin in part.

[0053] 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:

[0054] S11: coating the first surface 209 of the positive electrode current collector 201 to form a second positive electrode active material layer 202, wherein the direction from the positive electrode long head 204 to the positive electrode long tail 205 is a first direction;

[0055] S12 : coating along the second direction on the second surface 210 to form a first positive electrode active material layer 203 , the length of the first positive electrode active material layer 203 is smaller than the length of the second positive electrode active material layer 202 , and the positive short tail 207 is aligned with the positive long head 204 .

[0056] 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.

[0057] 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:

[0058] 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;

[0059] 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 smaller than the length of the second negative electrode active material layer 302 , and the negative electrode short tail 307 is aligned with the negative electrode long head 304 .

[0060] The third surface 309 and the fourth surface 310 are arranged back to back to each other, and the third direction is opposite to the fourth direction.

[0061] 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 for improving the controllability of the thickness of the electrode sheet.

[0062] 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:

[0063] S13: coating the first surface 209 of the positive electrode current collector 201 to form a second positive electrode active material layer 202, wherein the direction from the positive electrode long head 204 to the positive electrode long tail 205 is a first direction;

[0064] S14 : coating along the second direction on the second surface 210 to form a first positive active material layer 203 , the length of the first positive active material layer 203 is smaller than the length of the second positive active material layer 202 , and the positive short head 206 is aligned with the positive long tail 205 .

[0065] 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:

[0066] S23: 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;

[0067] S24 : coating along a fourth direction on the fourth surface 310 to form a first negative electrode active material layer 303 , wherein the length of the first negative electrode active material layer 303 is smaller than that of the second negative electrode active material layer 302 , and the extremely short head is aligned with the negative electrode long tail 305 .

[0068] 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 utility model 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 A battery cell 100 according to another embodiment of the present invention is shown. 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 .

[0069] 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 shell, and the battery cell 100 is arranged inside the shell. The shell can be a hard shell made of aluminum, steel or other metal materials, or a soft shell made of aluminum-plastic film.

[0070] Figure 4 The performances of the battery cell 100 of the present application and the battery cell 100 in the prior art are shown. Figure 4The figure shows the relationship between the capacity retention and the number of cycles of the battery cell 100. The test method for the battery cell 100 is: the battery cell 100 is charged to 4.30V at 3.5C constant current and constant voltage, with a cut-off ratio of 2.7C; charged to 4.40V at 2.7C constant current and constant voltage, with a cut-off ratio of 1.8C; charged to 4.53V at 1.8C constant current and constant voltage, with a cut-off ratio of 1.5C; charged to 4.58V at 1.5C constant current and constant voltage, with a cut-off ratio of 0.129C; the above is one cycle, which is repeated 800 times.

[0071] exist Figure 4 In the figure, 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" means 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 at a slower rate, and the battery cell 100 of the present application can still retain about 90% of its capacity after 600 cycles. Therefore, the capacity of the battery cell 100 decreases at a slower rate, and the performance of the battery cell 100 of the present application is better.

[0072] 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 dots that are "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, and the red points 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 battery cell 100 of the present application has better performance.

[0073] In the description of the utility model, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A battery 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 two opposite sides of the positive electrode current collector, 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, 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 two opposite sides of the negative electrode current collector, 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 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 electrode 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 the ratio of the capacity of the negative short tail to the capacity of the positive short head is greater than 1.

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

4. The battery cell according to claim 1, characterized in that: 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.

5. The battery cell according to claim 1, characterized in that: The ratio of the capacity of the negative electrode short head to the capacity of the positive electrode short tail is less than 1.

1.

6. The battery cell according to claim 1, characterized in that: The ratio of the capacity of the negative electrode short tail to the capacity of the positive electrode short head is less than 1.

1.

7. The battery cell according to claim 2, characterized in that: The minimum thickness of the first thinned region is smaller than the minimum thickness of the second thinned region.

8. The battery cell according to claim 1, characterized in that: The second positive electrode active material layer includes a third thinned area, the coating start end of the second positive electrode active material layer is the positive electrode long end, and one side edge of the third thinned area is the positive electrode long end.

9. The battery cell according to claim 1, characterized in that: The first positive electrode active material layer is provided with a first slot, and the positive electrode short head and the positive electrode short tail are respectively located at two sides of the first slot; The second positive electrode active material layer is provided with a second slot, the first slot and the second slot are arranged back to back, the coating start end of the second positive electrode active material layer is the positive electrode long head, the coating end end of the second positive electrode active material layer is the positive electrode long tail, and the positive electrode long head and the positive electrode long tail are respectively arranged on both sides of the second slot; The first negative electrode active material layer is provided with a third slot, and the negative electrode short head and the negative electrode short tail are respectively located on two sides of the third slot; The second negative electrode active material layer is provided with a fourth slot, the third slot and the fourth slot are arranged back to back to each other, the coating starting end of the second negative electrode active material layer is the negative electrode long head, and the coating ending end of the second negative electrode active material layer is the negative electrode long tail, and the negative electrode long head and the negative electrode long tail are respectively arranged on both sides of the fourth slot.

10. A battery, characterized in that The invention comprises the battery cell as claimed in any one of claims 1 to 9.

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