Battery cell, secondary battery, and electric device

Abstract

The present application discloses a battery cell, a secondary battery, and an electric device. The battery cell comprises a plurality of electrode sheets; each electrode sheet comprises a current collector and active substance coatings; the electrode sheet has a first region covered with the active substance coatings and a second region not covered with the active substance coatings; the first region is provided with a clearance notch; the second region forms a tab of the battery cell; among the plurality of stacked electrode sheets, for two adjacent electrode sheets, the first region of one electrode sheet is provided with a clearance notch so as to expose the second region of the other electrode sheet; the width of the electrode sheet is W mm, the area of the clearance notch is S1 mm2, the area of the second region is S2 mm2, and the thickness of the battery cell is H; when H is greater than 7 mm, S1+S2＜A*W is satisfied, and A is 3.6 mm; or, when H is less than or equal to 7 mm, S1+S2＜B*W is satisfied, and B is 1.6 mm. By means of such design, when a bare battery cell is formed by stacking, the tabs are accommodated in the main body region of the bare battery cell, and there is no need to perform multi-tab transfer welding, thereby improving space utilization; moreover, by setting the maximum value of S1+S2, it is ensured that the overall energy density of the battery cell is increased.

Description

Battery cells, secondary batteries and electrical equipment Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a secondary battery, and an electrical device. Background Art

[0002] The laminated battery cell uses lamination technology to stack multiple positive and negative current collector units together, and the current can flow through each current collector unit in turn. During the lamination process, diaphragms are needed to insulate and connect the current collectors to ensure that they can work in coordination and stably provide electrical energy. The laminated structure means that the battery can work as a multi-pole battery, making the battery itself less resistive, thereby generating less heat during charging or discharging, and extending the battery life.

[0003] In a multi-tab laminated cell, multiple layers of bare foil are gathered and cut in one direction to form a tab cluster, which is then connected to an additional tab connector. This tab structure creates a large gap between the electrode assembly and the casing, reducing space utilization.

[0004] Application Contents

[0005] The embodiments of the present application aim to provide a current collector, an electrode assembly, a battery cell, a secondary battery, and an electrical device, which can solve the technical problem of low space utilization of laminated battery cells in the prior art.

[0006] The embodiments of the present application solve the technical problems by adopting the following technical solutions:

[0007] According to the first aspect of the present application, the present application discloses a laminated battery cell, including a pole piece, the pole piece including: a current collector and an active material coating; the pole piece has a first area covered with the active material coating and a second area not covered with the active material coating; wherein the first area is provided with an avoidance gap, the avoidance gap is used to avoid the second area of ​​the adjacent current collector, and the second area forms the pole ear of the current collector; among a plurality of stacked pole pieces, for two adjacent pole pieces, the first area of ​​one pole piece is provided with an avoidance gap to expose the second area of ​​the other pole piece; the width of the pole piece is Wmm, and the avoidance gap area is S1mm 2 , the area of ​​the second region is S2mm 2 , the cell thickness is H; when H>7mm, S1+S2<A*W, A is 3.6mm; or, when H≤7mm, S1+S2<B*W, B is 1.6mm.

[0008] In this way, after the bare cells are stacked, the tabs will be accommodated in the main body area of ​​the bare cells. There is no need to set up multiple tab transfer welding outside the main body area of ​​the bare cell head, which can improve space utilization. At the same time, by setting the maximum value of S1+S2 to less than 3.6W, the overall energy density of the cell is ensured to increase.

[0009] In one or more / optional embodiments above, H≤7mm, S1+S2<C*W, and C is 1.0mm. Implementing this structure on a battery cell with H≤7mm can ensure an overall increase in energy density.

[0010] In one or more / optional embodiments above, the area S1 of the avoidance gap is 5 mm 2 -100mm 2 ; The area S2 of the second region is 5mm 2 -100mm 2 .

[0011] In one or more / optional embodiments above, the area S1 of the avoidance gap is 10 mm 2 -60mm 2 ; The area S2 of the second region is 10mm 2 -60mm 2 .

[0012] In one or more / optional embodiments described above, the pole piece has multiple corners; the relief notch is located at one corner of the pole piece, and the second region is located at another corner of the pole piece. Positioning the relief notch and the second region at different corners of the pole piece allows the portion of the current collector at the corner to function as a tab, reducing the gap between the electrode assembly and the cell casing and improving energy density.

[0013] In one or more / optional embodiments above, the pole piece is rectangular, having a first side and a second side parallel to each other, a third side perpendicular to the first side, and a fourth side perpendicular to the second side; wherein the avoidance gap is located at a first end angle formed by the first side and the third side; and the second area is located at a second end angle formed by the first side and the fourth side.

[0014] In one or more / optional embodiments above, the current collector has a first direction parallel to the third side and a second direction parallel to the first side; the maximum dimension of the second region in the first direction is 1mm-15mm; and the maximum dimension in the second direction is 1mm-15mm; in the first direction, the distance between the end of the first side adjacent to the third side and the third side is 1mm-15mm; and in the second direction, the distance between the end of the third side adjacent to the first side and the first side is 1mm-15mm. In this way, limiting the size of the tab to a reasonable range can prevent the tab from being too large, which would reduce the energy density of the battery cell, and also prevent the tab from being too small, which would result in poor electrical connectivity.

[0015] In one or more / optional embodiments above, the maximum dimension of the second area in the first direction is 3mm-10mm; and the maximum dimension in the second direction is 3mm-10mm; in the first direction, the distance between one end of the first side adjacent to the third side and the third side is 3mm-10mm; and in the second direction, the distance between one end of the third side adjacent to the first side and the first side is 3-10mm.

[0016] In one or more / optional embodiments above, the avoidance gap and the second area are both polygonal; wherein the number of line segments constituting the polygon is 3 to 8.

[0017] In one or more / optional embodiments above, the battery cell further comprises an electrode assembly, the battery cell assembly comprising: a plurality of anode plates, cathode plates arranged in a stacked manner, and a separator located between the anode plates and the cathode plates; wherein, a plurality of anode plates; each of the anode plates is made of the anode active material coated with the current collector described above; wherein, when viewed along the thickness direction of the electrode assembly, the tab of the anode plate is located at a first position, and the avoidance notch provided in the anode plate is located at a second position; a plurality of cathode plates; each of the cathode plates is formed by the cathode active material coated with the current collector described above; wherein, when viewed along the thickness direction of the electrode assembly, the tab of the cathode plate is located at a second position, and the avoidance notch provided in the cathode plate is located at a first position; a separator; when viewed along the thickness direction of the electrode assembly, the separator is provided with avoidance notches at both the first position and the second position; wherein, a plurality of anode plates and cathode plates are stacked, and the separator is located between the anode plates and the cathode plates; a plurality of tabs located at the same position form a tab group; in a tab group, at least a portion of the area between any two adjacent tabs contacts each other to form an electrical connection.

[0018] In this way, after the anode and cathode plates are stacked to form a bare cell, the tabs will be accommodated in the main body area of ​​the bare cell. There is no need to set up multiple tab transfer welds outside the main body area of ​​the bare cell head, which can improve space utilization. Moreover, during mechanical abuse, the tab group formed by the tabs gathered together is not easily impacted, swung, or twisted, avoiding safety problems such as short circuit between the tabs and the bare cell current collector.

[0019] In one or more / optional embodiments above, the tab group is formed by a plurality of tabs located at the same position, tilted in a direction close to the thickness center of the electrode assembly; wherein the thickness center is selected from: any point in the middle area of ​​the electrode assembly in the thickness direction, away from the two side surfaces of the electrode assembly.

[0020] In one or more / optional embodiments above, in the thickness direction, the distance between the tab group and one side surface of the electrode assembly is between 0.3T and 0.7T; wherein T is the thickness of the electrode assembly.

[0021] In one or more / optional embodiments above, for any one tab in the tab group, an angle between the tab and the current collector surface of the pole piece where the tab is located is greater than 90°.

[0022] This can prevent misalignment between adjacent tabs, which can cause the tab edges to warp outward and prevent a loose fit with adjacent tabs, affecting the conductivity of the tab group. Setting the preset angle greater than 90° will cause adjacent tabs to converge toward parallel alignment, resulting in a closer fit, lowering the resistance of the tab group and improving charge and discharge efficiency.

[0023] According to the second aspect of the present application, the present application also discloses another battery cell, comprising: the electrode assembly described above; a packaging shell, in which the electrode assembly is housed; at least two tab connecting pieces; wherein, one tab connecting piece is electrically connected to a tab group of the electrode assembly, one end of the tab connecting piece is electrically connected to the tab group, and the other end extends to the outside of the packaging shell to form an electric energy transmission channel.

[0024] In one or more / optional embodiments above, the tab connecting piece is arranged at one of the following positions: the upper surface of the tab group in the thickness direction; the lower surface of the tab group in the thickness direction; or between any two adjacent tabs inside the tab group.

[0025] According to a third aspect of the present application, the present application further discloses a secondary battery, comprising: a battery housing; and the above battery cells, wherein the battery cells are housed in the battery housing.

[0026] According to the fourth aspect of the present application, the present application further discloses an electrical device, including: the above secondary battery.

[0027] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the following description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0029] FIG1 is a schematic diagram of the structure of a pole piece in an embodiment of the present application;

[0030] FIG2 is a cross-sectional view of a pole piece in an embodiment of the present application;

[0031] FIG3 is a schematic structural diagram of an electrode assembly in an embodiment of the present application;

[0032] FIG4 is an assembly diagram of an electrode assembly in an embodiment of the present application;

[0033] FIG5 is a schematic diagram of the three-dimensional structure of the electrode assembly in an embodiment of the present application;

[0034] FIG6 is a top view of an electrode assembly in an embodiment of the present application;

[0035] FIG7 is a CC sectional view in FIG6;

[0036] FIG8 is a schematic diagram of a partial structure of a battery cell in an embodiment of the present application.

[0037] Figure numbers and corresponding meanings:

[0038] Pole piece 100;

[0039] Current collector 1, first side 101, second side 102, third side 103, fourth side 104, tab 10, anode tab 10a, cathode tab 10b, first region 11, second region 12, tab group 13, anode tab group 131, cathode tab group 132;

[0040] Active material layer 2, anode active material 21, cathode active material 22;

[0041] Avoidance gap 3, anode avoidance gap 31, cathode avoidance gap 32;

[0042] Electrode assembly 4, anode electrode piece 41, cathode electrode piece 42, separator 43, first position 44, second position 45;

[0043] Encapsulation shell 5, sealing area 50;

[0044] Tab connecting piece 6 and sealant area 60. DETAILED DESCRIPTION

[0045] To facilitate understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more elements can be interposed therebetween. When an element is described as being "connected to" another element, it can be directly connected to the other element, or one or more elements can be interposed therebetween. The terms "upper," "lower," "inner," "outer," "vertical," "horizontal," etc. used in this specification to indicate an orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings and are intended solely for the purpose of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present application. In addition, the terms "first," "second," etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Include" or "comprising" and similar words mean that the element or object preceding the word includes the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Unless otherwise defined, the features such as "parallel", "perpendicular" and "same" used in the embodiments of the present application include situations such as "parallel", "perpendicular", "same" in a strict sense, as well as situations such as "approximately parallel", "approximately perpendicular", "approximately the same" that contain a certain error. For example, the above-mentioned "approximately" may mean that the difference between the compared objects is 10% of the average value of the compared objects, or within 5%. When the number of a component or element is not specifically indicated below in the embodiments of the present application, it means that the component or element may be one or more, or may be understood as at least one. "At least one" refers to one or more, and "a plurality" refers to at least two.

[0046] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the relevant listed items.

[0047] In addition, the technical features involved in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] The present application discloses a laminated battery cell, including a pole piece 100. As shown in Figures 1 and 2, the pole piece 100 includes a current collector 1 and an active material coating 2 covering the current collector 1. The current collector 1 has a first region 11 covering the active material coating 2 and a second region 12 not covering the active material coating. The current collector 1 is a foil. The surface of the pole piece 100 is processed by laser cleaning, solvent wiping, or adhesive peeling, and the active material coating 2 of the pole piece 100 is locally removed to form the second region 12. The exposed empty foil in the second region 12 forms the pole lug 10 of the pole piece 100. Among them, the first region 11 is provided with an avoidance gap 3. The avoidance gap 3 is used to expose the second region 12 of the adjacent pole piece 100 when multiple pole pieces 100 are stacked on each other, so as to facilitate contact between two adjacent pole lugs 10 of the same polarity. That is, the avoidance gap 3 plays a role in avoiding air when two spaced pole lugs 10 are brought together.

[0049] The tabs of existing laminated cells are located outside the electrode assembly, making them susceptible to impact and vibration, posing a high safety risk. Furthermore, the method of folding the empty foil in one direction results in a thicker area at the folded portion, taking up more space.

[0050] In this embodiment, after the bare cells are stacked to form the battery, the tabs 10 will be accommodated in the main body area of ​​the bare cell. There is no need to set up multiple tab transfer welds outside the main body area of ​​the bare cell head, which can improve space utilization. Moreover, during mechanical abuse, the tab group formed by the tabs gathering together is not easily impacted, swung, or twisted, thus avoiding safety issues such as short circuit between the tabs and the bare cell current collector.

[0051] In this embodiment, there is a pole piece 100 of opposite polarity between two adjacent pole pieces 100 of the same polarity in the bare battery cell, and the two pole tabs 10 of the same polarity can only be gathered together to achieve electrical connection through the avoidance gap 3 on the middle pole piece 100 of opposite polarity, thereby forming a pole tab group.

[0052] In the existing laminated battery cells, since the tabs 10 of multiple layers of empty foils are gathered and cut in one direction to form a tab group, as the number of stacked electrode sheets 100 increases, the thickness H of the battery cell increases, and the thickness of the tab group also increases. Thus, the gap K between the electrode assembly and the packaging shell becomes larger as the thickness H of the battery cell increases, and consequently, the damaged area S0 inside the packaging shell due to the gap K also increases. The larger the damaged area S0, the lower the proportion of the active substances participating in the electrochemical reaction, and the lower the energy density of the battery cell. Here, S0 = KW, where W is the width of the electrode sheet 100.

[0053] Specifically, in the industry, when the battery cell thickness H > 7 mm, the gap K1 between the electrode assembly and the packaging shell is 4 mm, and the corresponding damaged area S0 = K1W; when H ≤ 7 mm, the gap K2 between the electrode assembly and the packaging shell is 2 mm, and the corresponding damaged area S0 = K2W.

[0054] In this embodiment, the empty foil at the second region 12 of the electrode sheet 100 forms the electrode sheet 100. The battery cell manufactured using this electrode sheet 100 can reduce the gap K3 between the electrode assembly and the packaging shell to 0.4 mm, and the corresponding damaged area S0 = (0.4 mm) * W.

[0055] Thus, compared with the prior art, when the battery cell thickness H > 7 mm, the beneficial area △S1 of the battery cell = (K1 - K3)W = (3.6 mm) * W; when the battery cell thickness H ≤ 7 mm, the beneficial area △S1 of the battery cell = (K2 - K3)W = (1.6 mm) * W. Here, the beneficial area of the battery cell is the area where the active substances increase. The larger the beneficial area of the battery cell, the higher the energy density of the battery cell of the same size.

[0056] However, since there are a first region 11 and a second region 12 in the electrode sheet 100 in this embodiment, and some active substances on the surface of the current collector 1 need to be washed away in the first region 11 and the second region 12, this in turn leads to an increase in the loss area △S2 of the space occupied by the active substances. Here, △S2 = S1 + S2, where S1 is the area of the avoidance notch 3, and S2 is the area of the second region 12.

[0057] To ensure an increase in the energy density of the battery cell, in this embodiment, △S2 < △S1. Thus, as long as it is ensured that the maximum value of S1 + S2 is less than 3.6W, it can be ensured that the overall energy density of the thick battery cell with H > 7 mm is increased compared with the prior art. Therefore, in this embodiment, the total area of the first region 11 and the second region 12 is less than (3.6 mm) * W, that is, S1 + S2 < A * W, where A is 3.6 mm.

[0058] Furthermore, in order to increase the overall energy density of the thin battery cell with H ≤ 7 mm in this embodiment, the total area of the first region 11 and the second region 12 in this embodiment is less than (1.6 mm * W), that is, S1 + S2 < B * W, where B is 1.6 mm.

[0059] Furthermore, in order to increase the overall energy density of the thin battery cell with H ≤ 7 mm, it is specified that the total area of the first region 11 and the second region 12 in this embodiment is less than (1.0 mm * W), that is, S1 + S2 < C * W, where C is 1.0 mm.

[0060] In this embodiment, since the purpose of the avoidance notch 3 is to expose the tab 10, if the area of the second region 12 exceeds that of the first region 11, the excess part of the second region 12 cannot be exposed, so it has no practical significance and instead causes unnecessary loss of active material. On the contrary, when the area of the first region 11 is greater than that of the second region 12, not only the tab 10 is exposed, but also some active materials are exposed through the avoidance notch 3, which also causes unnecessary loss of active material. Therefore, in this embodiment, the area S2 of the avoidance notch 3 is equal to the area S1 of the second region 12 to ensure the maximum energy density of the battery cell.

[0061] Since the greater the overlapping area between the two tabs 10, the better the electrical connectivity of the two tabs 10. And the greater the area of the avoidance notch 3 or the second region 12, the more the energy density of the battery cell is lost. When the area of the avoidance notch 3 is less than 5 mm 2 , the area of the tab 10 is too small, which will cause poor contact between adjacent tabs 10 and affect the electrical connectivity of the tab group. When the area of the avoidance notch 3 is greater than 100 mm 2 , it will also make the overall energy density of the battery cell too low. Therefore, in order to ensure good electrical connectivity when the tabs 10 gather to form a tab group, in this embodiment, the area of the avoidance notch 3 is 5 - 100 mm 2 .

[0062] Considering the energy density of the battery cell, the area S1 of the avoidance notch 3 and the area S2 of the second region 12 are preferably 5 - 60 mm 2 , within this range, the highest energy density can be ensured, and the electrical connectivity between multiple tabs 10 is strong enough to meet the safety requirements.

[0063] Furthermore, the area S1 of the avoidance notch 3 and the area S2 of the second region 12 are preferably 10 - 40 mm 2 , within this range, the energy density and the electrical connectivity of the tab 10 are further improved.

[0064] As shown in Figures 1 and 2, the pole piece 100 has multiple end angles, and the avoidance notch 3 and the second area 12 are respectively located at two different end angles. Specifically, as shown in Figure 1, the present embodiment below takes the pole piece 100 as a rectangle as an exemplary description. The pole piece 100 has a set of parallel sides, a first side 101 and a second side 102, forming a rectangle, and another set of parallel sides, a third side 103 and a fourth side 104, wherein the first side wall plate 101 connects one end of the third side 103 and the fourth side 104, and the second side 102 connects the other end of the third side 103 and the fourth side 104. The connection between the first side 101 and the third side 103 forms a first end angle, and the connection between the first side 101 and the fourth side 104 forms a second end angle. The avoidance notch 3 is set at the first end angle, and the second area 12 is located at the second end angle. In this embodiment, as shown in Figure 1, the specific structure of the avoidance notch 3 and the second area 12 is a chamfer set at the first end angle.

[0065] In this embodiment, the chamfered edges of the avoidance gap 3 and the second region 12 are polygonal, and the number of sides thereof is between 3 and 8. That is, the chamfered edges of the avoidance gap 3 and the second region 12 can be three to eight line segments.

[0066] As shown in Figures 3 and 4, the embodiment of the present application also discloses an electrode assembly 4 formed by stacking the above-mentioned electrode sheets 100. The electrode assembly 4 includes a plurality of stacked anode current collectors 41, a plurality of cathode current collectors 42, and an isolation membrane 43 located between the anode current collectors 41 and the cathode current collectors 42.

[0067] Multiple anode plates 41, cathode plates 42 and diaphragms 43 can be stacked in the following manner: ① anode plate 41, diaphragm 43, cathode plate 42, diaphragm 43, in this order of stacking in a cycle; ② cathode plate 42, diaphragm 43, anode plate 41, diaphragm 43, in this order of stacking in a cycle; ③ the upper and lower surfaces of the anode plate 41 are first hot-pressed and compounded with the diaphragm 43, and then compounded with the cathode plate 42 in turn, and then the anode plate 41 is checked, and they are stacked in this order; ④ the upper and lower surfaces of the cathode plate 42 are first hot-pressed and compounded with the diaphragm 43, and then the anode plate 41 and the cathode plate 42 are stacked in turn, and they are stacked in this order.

[0068] Specifically, as shown in FIG2 , the active material coating 2 coated on the surface of the current collector 1 includes an anode active material 21 and a cathode active material 22. As shown in FIG4 , the tab 10 further includes an anode tab 10a and a cathode tab 10b depending on the polarity of the tab 100. Depending on the polarity of the tab 10 to be avoided, the avoidance notch 3 further includes an anode avoidance notch 31 provided on the cathode tab 42 and a cathode avoidance notch 32 provided on the anode tab 41. The anode avoidance notch 31 is used to avoid the anode tab 10a, and the cathode avoidance notch 32 is used to avoid the cathode tab 10b.

[0069] Each anode electrode sheet 41 is made of a current collector 1 coated with an anode active material 21, and each cathode electrode sheet 42 is made of a current collector 1 coated with a cathode active material 22. When viewed along the thickness direction of the electrode assembly 4 (from a top view), the anode tab 10a of the anode electrode sheet 41 is located in a first position 44, and the cathode avoidance notch 32 provided on the anode electrode sheet 41 is located in a second position 45; the cathode tab 10b of the cathode electrode sheet 42 is located in a second position 45, and the anode avoidance notch 31 provided on the cathode electrode sheet 42 is located in a first position 44. That is, the avoidance notch 3 and the tab 10 are arranged in opposite positions on the anode electrode sheet 41 and the cathode electrode sheet 42.

[0070] The separator 43 is provided with an escape notch 3 at both the first position 44 and the second position 45. That is, the separator 43 is provided with an anode escape notch 31 at the first position 44 and a cathode escape notch 32 at the second position 45. Thus, the anode tab 10a and the anode escape notch 31 are both located at the first position 44, and the cathode tab 11 and the cathode escape notch 32 are both located at the second position 45. Multiple tabs 10 located at the same position form a tab group 13. Specifically, the anode tab 10a is brought together with the adjacent anode tab 10a through the separator 43 and the anode escape notch 31 of the cathode plate 42 to form an anode tab group 131 corresponding to the anode plate 41. The cathode tab 10b is brought together with the adjacent cathode tab 10b through the separator 43 and the cathode escape notch 32 of the anode plate 41 to form a cathode tab group 132 corresponding to the cathode plate 42.

[0071] In a tab group 13, at least a portion of any two adjacent tabs 10 are in contact with each other to form an electrical connection. That is, in the tab group 13 corresponding to the anode electrode sheet 41, two adjacent anode tabs 10a are overlapped along the convergence direction.

[0072] As shown in Figure 4, the tab group 13 is formed by multiple tabs 10 located in the same position, which are tilted toward the thickness center of the electrode assembly 4. The thickness center is located at a point in the middle of the thickness of the electrode assembly 4, which is away from the outermost tabs 10 on both sides of the electrode assembly 4. In other words, the anode tab group 131 is formed by the anode tabs 10a located on both sides converging toward the anode tab 10a located in the center. The cathode tab group 132 is formed by the cathode tabs 10b located on both sides converging toward the cathode tab 10b located in the center.

[0073] As shown in FIG. 5 , the distance d5 between the collapsed tab group 13 and the outermost tab 10 is between 0.3T and 0.7T, where T is the thickness of the electrode assembly 4 .

[0074] In addition, in this embodiment, as shown in FIG7 , for any one tab 10 in the tab group 13, a preset angle a is formed between the tab and the current collector surface of the pole piece where the tab is located. The preset angle a is greater than 90°. This can avoid the misalignment tolerance between adjacent tabs 10, which causes the edge of the tab 10 to warp outward and not fit tightly with the adjacent tab 10, thereby affecting the conductive performance of the tab group 13. When the preset angle a is set to be greater than 90°, the two adjacent tabs 10 tend to be parallel along the convergence direction, so that they fit more closely with each other, thereby reducing the resistance of the tab group 13 and improving the efficiency of charge and discharge.

[0075] The embodiment of the present application also discloses a battery cell, as shown in Figures 5 and 6, comprising an electrode assembly 4 and a packaging shell 5 for accommodating the electrode assembly 4, and at least two tab connecting pieces 6, each tab connecting piece 6 being electrically connected to a tab group 13 of the electrode assembly 4 to form an electric energy transmission channel. Specifically, as shown in Figure 8, the packaging shell 5 is filled with electrolyte, and the electrode assembly 4 is encapsulated in the packaging shell 5. One end of the tab connecting piece 6 is located inside the packaging shell 5 and is electrically connected to the tab group 13. The tab connecting piece 6 is electrically connected to the tab group 13 by laser welding or ultrasonic welding, and the location of the electrical connection between the two can be at the center of the tab group 13 or on both sides of the tab group 13. The tab connecting piece 6 is provided with a sealant area 60, which is located in the sealing area 50 of the packaging shell 5 to increase the sealing performance of the sealing area 50 and prevent leakage when the battery cell falls.

[0076] In the actual production of laminated battery cells, they need to pass drop tests and tab connection plate sealing tests.

[0077] Among them, (1) the drop test process is as follows:

[0078] After the sample is fully charged according to the specified test method, it is dropped from a drop height of 1m (battery pack: 1m for batteries above 1000mAh; 1.5m for portable electronic products below 1000mAh or with a planned use height higher than 1.0m). Cylindrical and button-shaped samples are dropped once on each end face and twice on the cylindrical surface, for a total of four drop tests; square and soft-packaged battery samples are dropped once on each face, for a total of six tests. For battery packs, after the test, a discharge and charge cycle drop is continued according to the specified charge and discharge method.

[0079] Pass standard: The battery should not catch fire or explode. The battery pack should not catch fire, explode or leak. The battery cell drop pass rate ≥ 80% is considered qualified.

[0080] (2) Lug connection plate sealing test:

[0081] Based on the actual battery cell production process, the ratio P of the sealant area 60 on the tab connecting plate 6 out of the sealing area 50 is collected.

[0082] Pass standard: P≤10%, the product is considered qualified and ready for mass production.

[0083] Because the area S1 of the avoidance notch 3 and the area S3 of the second region 12 affect the size of the tab, and the size of the tab 10 affects the relative position of the sealant area 60 of the tab connector 6 and the sealing area 50, the size of the tab 10 is related to the sealing performance of the battery cell. Specifically, if the tab 10 is too small, the contact area between the tab group 13 and the tab connector 6 is too small, which can easily cause the tab connector 6 to separate from the tab group 13 during a drop test, making the battery cell unable to function properly and posing the risk of a cathode and anode short circuit leading to combustion or explosion, thereby affecting the drop test pass rate. At the same time, if the tab 1 is too small, the tab connector 6 can move out of position, increasing the proportion of the sealant area 60 moving out of the sealing area 50, compromising the sealing performance of the battery cell and resulting in a low sealing test pass rate. While setting the tab 10 too large can significantly increase the drop test pass rate and reduce the proportion of the sealant area 60 leaving the sealing area 50, it will occupy space for the electrochemical reaction and reduce the energy density of the battery cell.

[0084] Therefore, the size of the tab 10 cannot be too large, which would reduce the energy density of the battery cell, nor too small, which would affect the safety standards required by the drop test and the tab connector 6 folding ratio test. To this end, the inventors of this application conducted a large number of experiments on the size of the tab 10, and the experimental data are as follows:

[0085] In this embodiment, the energy density level is a relative comparison concept, indicating the difference between the energy density of the current sample and the optimal energy density.

[0086] Among them, the greater the energy density level, the greater the difference between the two, and the lower the energy density of the corresponding sample. Vice versa, the lower the energy density level, the closer it is to the optimal energy density. When the energy density level is higher than or equal to level 10, it indicates that there is a significant difference between the two, and the product can be evaluated as unqualified. That is, the energy density level between 1-9 is a qualified product. According to the experimental data, the area S1 of the avoidance gap 3 and the area S2 of the second area are between 5-100mm 2 When S1 and S2 are between 5-60mm, the energy density level, drop pass rate, and sealing test failure rate all meet the standards; when S1 and S2 are between 5-60mm 2 When S1 and S2 are between 10-40mm, the cell energy density is high. 2 The energy density, drop pass rate and sealing test are all at a high level.

[0087] The embodiments of the present application further disclose a secondary battery and an electrical device including the secondary battery, wherein the secondary battery includes a battery housing and the above-mentioned battery cell accommodated in the battery housing.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell comprising a plurality of stacked pole pieces, the pole pieces comprising: A current collector and an active material coating; wherein the pole piece has a first region covered with the active material coating and a second region not covered with the active material coating; The first region is provided with an avoidance gap, the avoidance gap is used to avoid the second region of the adjacent electrode piece, and the second region forms the electrode ear of the battery cell; Among the plurality of stacked electrode pieces, for two adjacent electrode pieces, the first region of one of the electrode pieces is provided with the avoidance notch to expose the second region of the other electrode piece; The width of the pole piece is Wmm, and the area of the avoidance gap is S1mm. 2 , the area of the second region is S2mm 2 , the thickness of the battery cell is H; When H>7mm, S1+S2<A*W, A is 3.6mm; Alternatively, when H≤7mm, S1+S2<B*W, and B is 1.6mm.

2. The battery cell according to claim 1, characterized in that H≤7mm, S1+S2<C*W, C is 1.0mm.

3. The battery cell according to claim 1, characterized in that The area S1 of the avoidance gap is 5mm 2 -100mm 2 The area S2 of the second region is 5mm 2 -100mm 2 .

4. The battery cell according to claim 1, characterized in that The area S1 of the avoidance gap is 5mm 2 -60mm 2 The area S2 of the second region is 5mm 2 -60mm 2 .

5. The battery cell according to claim 1, characterized in that The area S1 of the avoidance gap is 10 mm 2 -40mm 2 , the area S2 of the second region is 10mm 2 -40mm 2 .

6. The battery cell according to any one of claims 1 to 5, characterized in that: The pole piece has a plurality of end angles; Wherein, the avoidance gap is arranged at one end corner of the pole piece; and the second area is located at the other end corner of the pole piece.

7. The battery cell according to claim 6, characterized in that The pole piece has a first side and a second side parallel to each other, a third side perpendicular to the first side, and a fourth side perpendicular to the second side; The avoidance gap is located at a first end angle formed by the first side and the third side; and the second area is located at a second end angle formed by the first side and the fourth side.

8. The battery cell according to claim 7, characterized in that: The pole piece has a first direction parallel to the third side, and a second direction parallel to the first side; The maximum dimension of the second area in the first direction is 1 mm to 15 mm; and the maximum dimension in the second direction is 1 mm to 15 mm; In the first direction, a distance between one end of the first side adjacent to the third side and the third side is 1mm-15mm; and in the second direction, a distance between one end of the third side adjacent to the first side and the first side is 1mm-15mm.

9. The battery cell according to claim 8, characterized in that The maximum dimension of the second area in the first direction is 3 mm to 10 mm; and the maximum dimension in the second direction is 3 mm to 10 mm; In the first direction, the distance between one end of the first side adjacent to the third side and the third side is 3mm-10mm; and in the second direction, the distance between one end of the third side adjacent to the first side and the first side is 3mm-10mm.

10. The battery cell according to any one of claims 1 to 5, characterized in that: The avoidance gap and the second area are both polygonal; The number of line segments constituting the polygon is 3 to 8.

11. The battery cell according to any one of claims 1 to 5, characterized in that: The electrode assembly further comprises: a plurality of anode pole pieces and cathode pole pieces stacked in layers, and a separator located between the anode pole pieces and the cathode pole pieces; A plurality of anode plates; each of the anode plates is made of the current collector coated with an anode active material; wherein, when viewed along the thickness direction of the electrode assembly, the tab of the anode plate is located at a first position, and the avoidance notch provided on the anode plate is located at a second position; a plurality of cathode plates; each cathode plate is formed by coating a cathode active material on the current collector; wherein, when viewed along the thickness direction of the electrode assembly, the tab of the cathode plate is located at the second position, and the avoidance notch provided on the cathode plate is located at the first position; Separator; observed along the thickness direction of the electrode assembly, the separator is provided with avoidance notches at the first position and the second position; Among them, multiple anode plates and cathode plates are stacked together, and the isolation membrane is located between the anode plates and the cathode plates; multiple tabs located at the same position form a tab group; in a tab group, at least a portion of the area between any two adjacent tabs is in contact with each other to form an electrical connection.

12. The battery cell according to claim 11, characterized in that The tab group is formed by a plurality of tabs located at the same position and tilted toward the thickness center of the electrode assembly; The thickness center is selected from any point in the middle area of the electrode assembly in the thickness direction and away from the two side surfaces of the electrode assembly.

13. The battery cell according to claim 11, characterized in that In the thickness direction, the distance between the tab group and one side surface of the electrode assembly is between 0.3T and 0.7T; Wherein, T is the thickness of the electrode assembly.

14. The battery cell according to claim 11, characterized in that For any one tab in the tab group, an angle between the tab and the current collector surface of the pole piece where the tab is located is greater than 90°.

15. The battery cell according to claim 11, characterized in that Also includes: a packaging shell, wherein the electrode assembly is housed in the packaging shell; At least two tab connectors; Among them, one of the tab connecting pieces is electrically connected to a tab group of the electrode assembly, one end of the tab connecting piece is electrically connected to the tab group, and the other end extends to the outside of the packaging shell to form an electric energy transmission channel.

16. The battery cell according to claim 15, characterized in that: The tab connection piece is arranged in one of the following positions: the upper surface of the tab group in the thickness direction; the lower surface of the tab group in the thickness direction; or Between any two adjacent tabs within the tab group.

17. A secondary battery, characterized in that: include: Battery housing; as well as The battery cell according to any one of claims 1 to 16, wherein the battery cell is housed in the battery casing.

18. An electrical device, characterized in that: include: The secondary battery according to claim 17.

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