Pole piece, battery cell, battery and electric device

Abstract

The utility model relates to a pole piece, a battery cell, a battery and a power utilization device, the pole piece comprises an active layer, the active layer comprises a first active area and a plurality of second active areas, and the first active area separates the second active areas; a compaction density of the first active region is lower than a compaction density of the second active region. Wherein the total length H of the first active region, the length L1 of the active layer and the width L2 of the active layer meet the condition that H / [2 * (L1 + L2)] is larger than or equal to 0.01 and smaller than or equal to 1. According to the technical scheme, the battery capacity can be considered while the electrode liquid permeation effect and the exhaust effect of the pole piece are improved so as to improve the cycle performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to pole pieces, battery cells, battery packs and electrical devices. Background Art

[0002] The capacity of power cells is generally high, and there are many pole pieces inside a single cell. In order to improve the production efficiency of the cell, the pole pieces of the single cell tend to be longer and larger. For large-sized pole pieces, the pole piece area is large, and the electrolyte infiltration effect is poor in a short period of time, which is prone to lithium precipitation in the middle area of ​​the pole piece, causing the cell cycle to dive. If the infiltration time is extended, it is not conducive to the control of the injection process. Moreover, the small amount of gas generated inside the cell during the formation stage of the large-sized pole piece is easy to remain between the pole pieces, and form spots in the local area of ​​the pole piece. The spot position will accelerate lithium precipitation, resulting in a poor pole piece interface, which is not conducive to the stability of the cell cycle. Utility Model Content

[0003] Based on this, the present application provides a pole piece, a battery cell, a battery and an electrical device, which can not only accelerate the infiltration of the electrolyte into the pole piece, but also facilitate the discharge of gas between the pole pieces, alleviate the lithium plating of the battery, and improve the cycle performance of the battery cell.

[0004] A pole piece, comprising:

[0005] An active layer, comprising a first active region and a plurality of second active regions, wherein the first active region separates the second active regions; and a compaction density of the first active region is lower than a compaction density of the second active region;

[0006] The total length H of the first active area, the length L1 of the active layer, and the width L2 of the active layer satisfy: 0.01≤H / [2*(L1+L2)]≤1.

[0007] In some embodiments, the first active region and the second active region are arranged with equal thickness, and the surface density of the first active region is lower than the surface density of the second active region.

[0008] In some embodiments, the first active region extends to an end surface of the active layer, and the end surface includes at least one end surface of the active layer in a width direction thereof and / or at least one end surface of the active layer in a length direction thereof.

[0009] In some embodiments, the first active area includes at least one active segment arranged in a thin strip shape, each of the active segments extends in a straight line or in a zigzag manner, and each of the active segments is separated between adjacent second active areas.

[0010] In some embodiments, the at least one active segment includes a plurality of longitudinal active segments arranged at intervals along the length direction of the active layer, each of the longitudinal active segments is separated between adjacent second active areas; each of the longitudinal active segments extends from one end surface to the other end surface in the width direction of the active layer.

[0011] In some embodiments, all of the longitudinal active segments are arranged in parallel.

[0012] In some embodiments, the longitudinal active section extends in a straight line or in a curve.

[0013] In some embodiments, the at least one active segment further comprises a transverse active segment, and the transverse active segment is staggeredly connected to the plurality of longitudinal active segments.

[0014] In some embodiments, at least some of the active segments are interlaced with at least one other active segment.

[0015] In some embodiments, the width w of the first active area satisfies: 10 μm ≤ w ≤ 800 μm; and / or,

[0016] The H, L1, and L2 satisfy: 0.1≤H / [2*(L1+L2)]≤0.8; and / or,

[0017] The compaction density of the first active area is 60%-80% of the compaction density of the second active area.

[0018] A battery cell comprises the pole piece as described in the above embodiment.

[0019] A battery comprises the battery cell as described in the above embodiment.

[0020] An electrical device comprises the battery as described in the above embodiment, wherein the battery is used to provide electrical energy.

[0021] In actual application, the first active area of ​​the above-mentioned pole piece, battery cell, battery and power-consuming device can be used as a channel for electrolyte penetration during the injection stage to guide the flow of electrolyte in the middle area of ​​the pole piece, so as to accelerate the electrolyte penetration efficiency, shorten the injection time, and alleviate the problem of lithium precipitation in the pole piece caused by poor electrolyte penetration in the middle area of ​​the pole piece, which helps to improve the cycle stability of the battery cell. In addition, the first active area can also be used as a gas discharge channel during the formation stage, guiding the gas generated in the middle area of ​​the pole piece to be discharged outside the pole piece, alleviating the problem of accelerated lithium precipitation caused by spots formed by residual gas, which helps to improve the cycle stability of the battery cell.

[0022] In addition, H, L1, and L2 satisfy: 0.01≤H / [2*(L1+L2)]≤1, and the total length of the first active area can take a larger value as the perimeter of the active layer increases, so that the active layer area passed by the first active area is wider, and a longer channel for electrolyte infiltration and exhaust can be set on the pole piece, which helps to improve the electrolyte infiltration effect and exhaust effect. Moreover, within the above range, the first active area occupies an appropriate area of ​​the active layer, has little effect on the active material of the active layer, and has little negative impact on the pole piece interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0024] Figure 1 Schematic diagram of the structure of pole pieces in some embodiments.

[0025] Figure 2 Schematic diagrams of the structures of pole pieces in other embodiments.

[0026] Figure 3 Schematic diagrams of the structures of pole pieces in other embodiments.

[0027] The reference numerals in the specific implementation manner are as follows:

[0028] 10. Pole piece; 11. Active layer; 11A. First active area; A1. Active segment; A11. Longitudinal active segment; A12. Transverse active segment; 11B. Second active area; 12. Pole ear. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0030] In the description of the present application, it should be understood that terms such as “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships, if any, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application 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 should not be understood as a limitation on the present application.

[0031] In addition, if present, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0032] In this application, unless otherwise clearly specified and limited, if any, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In the present application, if it appears, unless otherwise clearly specified and limited, a first feature “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature “above”, “above” and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature “below”, “below” and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0034] It should be noted that, if present, when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0035] In view of the problems mentioned in the background technology, the embodiments of the present application propose a pole piece.

[0036] Reference Figure 1 The pole piece 10 provided in the embodiment of the present application includes an active layer 11, the active layer 11 includes a first active area 11A and a plurality of second active areas 11B, the first active area 11A separates the second active areas 11B, and the compaction density of the first active area 11A is lower than the compaction density of the second active area 11B. Among them, the total length H of the first active area 11A, the length L1 of the active layer 11, and the width L2 of the active layer 11 satisfy: 0.01≤H / [2*(L1+L2)]≤1.

[0037] The active layer 11 is the surface structure of the pole piece 10, which is formed by an electrode active material. In addition to the active layer 11, the pole piece 10 also includes a current collector, and the active layer 11 is arranged on one side or both sides in the thickness direction of the current collector. The active layer 11 is usually obtained by coating the electrode active slurry on the current collector. The current collector is used to collect current and can be a metal current collector, a composite current collector, etc. The portion of the current collector that is not coated with the active layer 11 can be used as the pole ear 12 of the pole piece 10 for connecting an external circuit. Regarding the specific structure of the current collector and the active layer 11, reference can be made to the conventional settings in the art.

[0038] The active layer 11 may be a positive electrode active layer 11 or a negative electrode active layer 11. The positive electrode active layer 11 contains a positive electrode active material, which includes but is not limited to lithium cobalt oxide, lithium nickel oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron phosphate, lithium iron titanate, cobalt trifluoride, etc. The negative electrode active layer 11 contains a negative electrode active material, which includes but is not limited to graphite, soft carbon, hard carbon, lithium titanate, metallic lithium, tin-based materials, silicon-based materials, etc.

[0039] It can be understood that the width direction of the active layer 11 is consistent with the width direction of the pole piece 10 , the length direction of the active layer 11 is consistent with the length direction of the pole piece 10 , and the thickness direction of the active layer 11 is consistent with the thickness direction of the pole piece 10 .

[0040] The active layer 11 is divided into a plurality of second active regions 11B, and the first active region 11A is separated between the second active regions 11B. Specifically, the first active region 11B may completely separate two adjacent second active regions 11B, or may partially separate two adjacent second active regions 11B.

[0041] It should be noted that the first active area 11A and the second active area 11B are adjacently arranged in a plane perpendicular to the thickness direction of the active layer 11. Generally, the area of ​​the second active area 11B is larger than that of the first active area 11A, and is used to provide a main reaction interface of the active layer 11. The specific layout of the plurality of second active areas 11B is flexibly set according to the specific structure of the first active area 11A.

[0042] The compaction density of the first active area 11A is lower than the compaction density of the second active area 11B. The compaction density refers to the content of active material per unit volume. Specifically, the compaction density can be expressed by the mass of active material per unit volume. The higher the compaction density, the higher the content of active material per unit volume, the tighter the active material, and the lower the porosity of the active area. On the contrary, the lower the compaction density, the lower the content of active material per unit volume, the looser the active material, and the higher the porosity of the active area.

[0043] In actual application, since the second active areas 11B are separated by the first active areas 11B, the first active areas 11B penetrate into the internal area of ​​the active layer 11, and the holes between the first active areas 11A with lower porosity can accelerate the penetration of electrolyte into the electrode 10, and accelerate the flow of gas inside the electrode 10 to discharge the gas. Therefore, the first active areas 11A can constitute channels to accelerate the penetration of electrolyte and exhaust of gas in the active layer 11.

[0044] The total length H of the first active area 11A is its total extended length. Generally, the length L1 of the active layer 11 is not less than the width L2 of the active layer 11. In particular, for the long strip-shaped pole piece 10, the length L1 of the active layer 11 is generally much greater than the width L2 of the active layer 11. At this time, the pole piece 10 is suitable for winding a battery cell.

[0045] In the embodiment of the present application, H, L1, and L2 satisfy: 0.01≤H / [2*(L1+L2)]≤1. Among them, 2*(L1+L2) represents the circumference of the active layer 11. As the size of the pole piece 10 is larger, that is, the circumference of the active layer 11 is larger, the value of H is often designed to be larger, so as to meet the electrode liquid penetration effect and exhaust effect of the larger size pole piece 10. However, the value of H should not be too large, otherwise the first active area 11A occupies too much area of ​​the active layer 11, reducing the active material content of the active layer 11, which is not conducive to the battery capacity. Specifically, H / [2*(L1+L2)] can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 and any value between adjacent values.

[0046] In actual application, the first active area 11A of the above-mentioned pole piece 10 can be used as a channel for electrolyte penetration during the injection stage to guide the electrolyte to flow in the middle area of ​​the pole piece 10, so as to accelerate the electrolyte penetration efficiency, shorten the injection time, and alleviate the problem of lithium precipitation of the pole piece 10 caused by poor electrolyte penetration in the middle area of ​​the pole piece 10, which helps to improve the cycle stability of the battery cell. Moreover, the first active area 11A thereon can also be used as a channel for gas discharge during the formation stage, guiding the gas generated in the middle area of ​​the pole piece 10 to be discharged outside the pole piece 10, alleviating the problem of accelerated lithium precipitation caused by spots formed by residual gas, which helps to improve the cycle stability of the battery cell.

[0047] In addition, H, L1, and L2 satisfy: 0.01≤H / [2*(L1+L2)]≤1, and the total length of the first active area 11A can take a larger value as the perimeter of the active layer 11 increases, so that the active layer 11 area passed by the first active area 11A is wider, and a longer channel for electrolyte infiltration and exhaust can be set on the pole piece 10, which helps to improve the electrolyte infiltration effect and exhaust effect. Moreover, within the above range, the first active area 11A occupies an appropriate area of ​​the active layer 11, has little effect on the active material of the active layer 11, and has little negative impact on the pole piece interface.

[0048] In actual application, in order to obtain the first active area 11A and the second active area 11B with different compaction densities on the active layer 11, it can be obtained by gravure coating combined with equal thickness rolling. It can also be obtained by using a comb tool to scrape off part of the active material in the area with a smaller compaction density on the basis of equal thickness coating, and then adopting equal thickness rolling.

[0049] Specifically, in some embodiments, the first active area 11A and the second active area 11B are arranged with equal thickness, and the surface density of the first active area 11A is lower than the surface density of the second active area 11B.

[0050] The surface density of the first active area 11A is lower than that of the second active area 11B. Surface density refers to the content of active material per unit area in a plane perpendicular to the thickness direction of the active layer 11. Since the first active area 11A and the second active area 11B are set to be of equal thickness, the area with higher surface density has higher content of active material per unit area, the active materials are tightly packed together, the lower the porosity, and the higher the compaction density. On the contrary, the area with lower surface density has lower content of active material per unit area, the active materials are looser, the higher the porosity, and the lower the compaction density.

[0051] In practical applications, the active layer 11 can be coated on the flat surface of one side of the current collector, and the first active area 11A and the second active area 11B with equal thickness and different surface density can be obtained by gravure coating combined with equal thickness rolling, so that the surfaces of the first active area 11A and the second active area 11B are flush, that is, the surface of the active layer 11 is flat. In this way, not only is the coating operation of the active layer 11 more convenient, but the active layer 11 with a flat surface is also conducive to the utilization of the space inside the battery cell.

[0052] Of course, in some cases, if the surface of the current collector used to cover the active layer 11 is a non-flat surface, the surfaces of the first active area 11A and the second active area 11B may not be flush. In other cases, the surface of the current collector used to cover the active layer 11 may be a non-flat surface, and the surfaces of the first active area 11A and the second active area 11B may be flush, as long as the compaction densities are different.

[0053] In some embodiments, the first active region 11A extends to an end surface of the active layer 11. The end surface includes at least one end surface of the active layer 11 in its width direction and / or at least one end surface of the active layer 11 in its length direction.

[0054] When the first active area 11A extends to the end surface of the active layer 11, the first active area 11A is connected to the outside of the active layer 11 through the end surface, so that the electrolyte can penetrate into the middle area of ​​the active layer 11 through the first active area 11A, and the gas generated in the middle area of ​​the active layer 11 during the formation stage can be smoothly discharged from the pole piece 10 through the first active area 11A. In this way, the exhaust efficiency and the penetration efficiency can be improved.

[0055] In specific applications, the first active area 11A may extend only to the two end surfaces of the active layer 11 in the width direction or only to the two end surfaces of the active layer 11 in the length direction, or partially extend to the end surfaces of the active layer 11 in the width direction and partially extend to the end surfaces of the active layer 11 in the length direction.

[0056] Specifically in some embodiments, refer to Figure 1 and Figure 2The first active region 11A extends to at least one end surface of the active layer 11 in the width direction.

[0057] For the long strip electrode 10, most of them are wound to form a battery cell. For the wound battery cell, the electrolyte is easier to infiltrate into the battery cell from the width direction of the electrode 10. Therefore, in the embodiment of the present application, the first active area 11A extends to one end surface or both end surfaces of the active layer 11 in the width direction. The electrolyte infiltration path and the gas discharge path are both short, which helps the electrolyte to infiltrate into the electrode 10 and also helps the gas inside the electrode 10 to be discharged quickly.

[0058] In some embodiments, the first active area 11A includes at least one active segment A1 arranged in a thin strip shape, each active segment A1 extends in a straight line or in a curve, and each active segment A1 is separated between adjacent second active areas 11B.

[0059] The active segment A1 is in the form of a thin strip, which means that its dimension in the extension direction is much larger than its width. Specifically, it can be in the form of a straight line or a curve. The thin strip-shaped active segment A1 will not occupy too much area of ​​the active layer 11, and can increase the active material content of the active layer 11, which is beneficial to the improvement of the battery capacity.

[0060] Generally, the more active segments A1 the first active region 11A includes, and the more active segments A1 are evenly distributed on the active layer 11, the first active region 11A can guide the electrolyte to more evenly penetrate into the interior of the active layer 11. When there is only one active segment A1, the active segment A1 can extend in a meandering manner like a river to expand the area of ​​the active layer 11 through which it passes, thereby improving the penetration effect.

[0061] It can be understood that the total length of the first active area 11A is the extended length of the entire active segment A1.

[0062] In some embodiments, at least one active segment A1 includes a plurality of longitudinal active segments A11 spaced apart along the length direction of the active layer 11, each longitudinal active segment A11 being separated between adjacent second active regions 11B. Each longitudinal active segment A11 extends from one end surface of the active layer 11 in the width direction to the other end surface.

[0063] At this time, the first active area 11A can guide the electrolyte to extend from both ends of the active layer 11 in the width direction to the central area thereof, and guide the gas to be discharged from the central area of ​​the active layer 11 to both ends in the width direction thereof, and both the electrolyte penetration efficiency and the exhaust efficiency are relatively high.

[0064] Specifically in one embodiment, refer to Figure 1 The longitudinal active section A11 extends in a straight line, which makes it easy to simplify the gravure coating tool and facilitates the formation of the first active area 11A.

[0065] In other embodiments, reference Figure 2 , the longitudinal active segment A11 extends in a curved shape.

[0066] For example, part of the active material is scraped off along a curved path by a comb tool. In this case, the longitudinal active segment A11 has a longer extension length and a wider area of ​​the active layer 11 along its path, resulting in better electrolyte wetting and exhaust effects.

[0067] In some embodiments, reference Figure 1 and Figure 2 , all longitudinal active segments A11 are arranged in parallel.

[0068] Specifically, all longitudinal active sections A11 may extend in a straight line. Specifically, all longitudinal active sections A11 may extend in a curve.

[0069] All longitudinal active segments A11 are arranged in parallel and can be processed in the same manner, which simplifies the processing of the active layer 11 and improves the processing efficiency of the active layer 11 .

[0070] In some embodiments, at least a portion of the active segments A1 are interlaced with at least one other active segment A1.

[0071] Reference Figure 3 In some examples, at least one active segment A1 further includes a transverse active segment A12, and the transverse active segment A12 is staggeredly connected with a plurality of longitudinal active segments A11. The transverse active segment A12 can extend from one end to the other end in the length direction of the active layer 11, and be staggeredly connected with the longitudinal active segment A11. Furthermore, the transverse active segment A12 can extend to the end surface of the active layer 11 to further improve the wetting efficiency and the exhaust efficiency.

[0072] In other examples, a plurality of active segments A1 may be staggered to form a first active region 11A in a tree-like, radial, or network-like shape.

[0073] At this time, the staggered active segments 11A increase the electrode liquid infiltration path and exhaust path, which helps to improve the electrolyte infiltration uniformity, so that the infiltration efficiency and exhaust efficiency are improved, which helps to improve the cycle performance of the battery cell.

[0074] In some embodiments, the width w of the first active region 11A satisfies 10 μm≤w≤800 μm.

[0075] The width w of the first active area 11A refers to the average width of the first active area 11A in the horizontal direction on a cross section perpendicular to its extension direction. Generally, the width of the first active area 11A is equal at all locations on the cross section.

[0076] Specifically, the width w of the first active area 11A can be 10 μm, 210 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm and any value between adjacent values.

[0077] When w is within the above range, the area of ​​the active layer 11 occupied by the first active region 11A is more appropriate, which can take into account both the electrolyte infiltration effect and the good exhaust effect, as well as the good battery cell capacity and cycle performance.

[0078] In some embodiments, H, L1 and L2 satisfy: 0.1≤H / [2*(L1+L2)]≤0.8. In this case, the first active region 11A occupies an appropriate area of ​​the active layer 11, and both the electrolyte wetting effect and the exhaust effect are good.

[0079] In some embodiments, the compaction density of the first active area 11A is 60%-80% of the compaction density of the second active area 11B. Specifically, the compaction density of the first active area 11A is 60%, 65%, 70%, 75%, 80% of the compaction density of the second active area 11B, and values ​​therebetween.

[0080] At this time, the active material content in the first active area 11A is relatively high, and the formed porosity is relatively high, which can take into account the battery capacity, permeation efficiency and exhaust efficiency.

[0081] The following provides a performance comparison of a battery cell prepared by a specific embodiment of the electrode sheet and a comparative example battery cell. Comparative Example 1 and Comparative Example 2 are both conventional negative electrode sheets of the same specifications, and the length L1 and width L2 of the active layer are 590 mm and 110 mm respectively. The embodiment is a negative electrode sheet of the same specifications as Comparative Example 1 and Comparative Example 2, except that a negative electrode sheet is processed and formed on the active layer of the negative electrode sheet. Figure 1 As shown, multiple longitudinal active segments A11 extending in a straight line are arranged at intervals along the length direction of the active layer 11, and are designed to be H / 2*(L1+L2)=0.63. The compaction density of the longitudinal active segments A11 is designed to be 60% of the compaction density of a conventional negative electrode sheet (i.e., the compaction density of the second active area 11B of the electrode sheet in the embodiment).

[0082] The negative electrode sheets of Comparative Example 1, Comparative Example 2 and the embodiment are assembled into battery cells according to the same process. The battery cell assembly process is consistent except for the negative electrode sheets used.

[0083] After the battery cells formed by the corresponding pole pieces of comparative document 1 and the embodiment were injected with liquid and soaked for 20 hours, they were divided into two groups, one of which was used to test its cycle performance, and the other group was fully charged and then the pole pieces were disassembled to observe the pole piece interface. Similarly, the battery cells formed by the corresponding pole pieces of comparative example 2 were injected with liquid and soaked for 48 hours and then divided into two groups, one of which was used to test its cycle performance, and the other group was fully charged and then the pole pieces were disassembled to observe the pole piece interface. Among them, the specific means for cycle performance testing can be referred to "GB / T31484-2015 Cycle Life Requirements and Test Methods for Power Batteries for Electric Vehicles"). As for disassembling the pole pieces after the battery cells are fully charged, it is a conventional means in this field and is not limited here.

[0084] Table 1 records the experimental results of Comparative Example 1, Comparative Example 2, and Example.

[0085] Table 1

[0086]

[0087] From the analysis of Table 1, we can see that:

[0088] Comparative Example 1: After the conventional negative electrode sheet was immersed in the electrolyte for 20 hours, the electrolyte infiltration effect was poor, the negative electrode sheet in the fully charged state was in poor condition, there was a phenomenon of poor black lithium embedding in the central position, and there were black spots caused by the generation of gas that was not discharged.

[0089] Comparative Example 2: The electrolyte infiltration time of the conventional negative electrode sheet was extended to 48 hours, and the electrolyte infiltration was improved. The state of the fully charged negative electrode sheet was slightly worse, and there was still a phenomenon of poor black lithium embedding in the central position, and there were black spots caused by the generation of gas that was not discharged.

[0090] Embodiment: For the negative electrode sheet having a longitudinal active segment A11 extending in a straight line, after 20 hours of electrolyte infiltration, the electrolyte infiltration is significantly improved, the interface of the negative electrode sheet in a fully charged state is good, there is no black spot phenomenon of poor lithium insertion in the central position, and no gas black spot is generated.

[0091] In summary, by forming the first active area in the active layer of the electrode, the electrode immersion time can ensure a good liquid injection effect on the basis of the original time, and the gas generated by formation and volume separation is easier to discharge and does not remain on the surface of the electrode to form black spots, which has a positive effect on improving the cycle performance of the battery cell and the interface conditions of the electrode.

[0092] In addition, the embodiment of the present application further provides a battery cell, including the pole piece 10 in the above embodiment. The battery cell has all the beneficial effects of the above embodiment. The pole piece 10 can be used as a positive pole piece or a negative pole piece.

[0093] In a specific example, the battery cell includes a shell, an end cap and an electrode assembly, and the shell and the end cap cooperate to form an internal space of the battery cell, and the electrode assembly is contained in the internal space. The electrode assembly is a unit for electrochemical reaction in the battery cell, usually including a positive electrode sheet, a negative electrode sheet and a separator, which is arranged between the positive electrode sheet and the negative electrode sheet, plays the role of insulating and isolating the positive electrode sheet and the negative electrode sheet, and can allow ions to pass through itself. The separator can be a diaphragm. The electrode assembly can be a winding type or a laminated type. Generally, a pole, an explosion-proof structure, an injection hole, etc. can be arranged on the end cap. The pole is electrically connected to the electrode assembly for connection with an external circuit. The explosion-proof structure can break and release pressure when the internal air pressure of the battery cell exceeds a threshold value, which can be an explosion-proof valve, a thinned low surface density area, etc. The injection hole is used to inject electrolyte into the battery cell. The battery cell can be a primary battery cell, a secondary battery cell, etc. The specific shape can be a cylindrical battery cell, a square battery cell, etc.

[0094] Regarding the specific structure of the battery cell, those skilled in the art can make routine settings.

[0095] In addition, the present application also provides a battery, which includes the above-mentioned battery cell. In addition to the battery cell, in some embodiments, the battery also includes a box. Multiple battery cells are arranged side by side in the box. A battery pipeline system for managing the battery cells and a liquid cooling structure for dissipating heat from the battery cells can also be arranged in the box. Those skilled in the art can make conventional settings regarding the specific structure of the battery.

[0096] In addition, the embodiment of the present application also provides an electric device, including the above-mentioned battery, which is used to provide electric energy. The electric device can be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery car, an electric car, a ship, etc. Taking the electric device as a vehicle as an example, the battery can be set at the rear, front or bottom of the vehicle, and the battery can provide electric energy for the drive of the vehicle, and can also provide electric energy for the control system of the vehicle.

[0097] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A pole piece, characterized in that: The pole piece comprises: An active layer (11), comprising a first active area (11A) and a plurality of second active areas (11B), wherein the first active area (11A) separates each of the second active areas (11B); the compaction density of the first active area (11A) is lower than the compaction density of the second active area (11B); The total length H of the first active area (11A), the length L1 of the active layer (11), and the width L2 of the active layer (11) satisfy: 0.01≤H / [2*(L1+L2)]≤1.

2. The pole piece according to claim 1, characterized in that: The first active area (11A) and the second active area (11B) are arranged with equal thickness, and the surface density of the first active area (11A) is lower than the surface density of the second active area (11B).

3. The pole piece according to claim 1, characterized in that: The first active area (11A) extends to the end surface of the active layer (11), and the end surface includes at least one end surface of the active layer (11) in its width direction and / or at least one end surface of the active layer (11) in its length direction.

4. The pole piece according to any one of claims 1 to 3, characterized in that: The first active area (11A) comprises at least one active segment (A1) arranged in a thin strip shape, each active segment (A1) extends in a straight line or in a zigzag manner, and each active segment (A1) is separated between adjacent second active areas (11B).

5. The pole piece according to claim 4, characterized in that: The at least one active segment (A1) comprises a plurality of longitudinal active segments (A11) arranged at intervals along the length direction of the active layer (11), each of the longitudinal active segments (A11) being separated between adjacent second active areas (11B); each of the longitudinal active segments (A11) extending from one end surface to the other end surface in the width direction of the active layer (11).

6. The pole piece according to claim 4, characterized in that: At least part of the active segments (A1) are arranged alternately with at least one other active segment (A1).

7. The pole piece according to any one of claims 1 to 3, characterized in that: The width w of the first active area (11A) satisfies: 10 μm ≤ w ≤ 800 μm; and / or, The H, L1, and L2 satisfy: 0.1≤H / [2*(L1+L2)]≤0.8; and / or, The compaction density of the first active area (11A) is 60%-80% of the compaction density of the second active area (11B).

8. A battery cell, characterized in that: Comprising a pole piece as claimed in any one of claims 1 to 7.

9. A battery, characterized in that: Comprising the battery cell as claimed in claim 8.

10. An electrical device, characterized in that: Comprising a battery as claimed in claim 9, the battery is used to provide electrical energy.

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