Electrode assembly, battery and electric equipment

Abstract

The utility model provides an electrode assembly, a battery and electric equipment, and relates to the technical field of batteries. The electrode assembly includes a wound body. The winding body comprises a wound pole piece, and the pole piece comprises a pole piece body, a tab area and a transition area. The pole piece body is coated with an active substance, and the pole piece body is connected with the tab region through the transition region. And the tab region comprises a plurality of tabs which are arranged at intervals along the winding circumferential direction. The tab area comprises a first section and a second section, one end of the first section is connected with one end, far away from the pole piece body, of the transition area, the second section is connected with one end, far away from the transition area, of the first section, the first section is bent towards the direction far away from the winding center along the leveling direction of the tab area towards the pole piece body, and the second section is bent towards the direction of the winding center. In the leveling process of the tabs, the first section and the second section can be regularly leveled to the pole piece body according to the bending direction, so that the problem that metal chips are generated due to rubbing is effectively avoided, and the distribution rule of the tabs is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrode assembly, a battery and an electric device. BACKGROUND

[0002] The preparation process of the electrode assembly of the full-tab battery cell generally includes winding of the tab and flattening of the tab. In some related technologies, the flattening of the tab adopts a mechanical flattening manner, which causes irregular bending of the tab and leads to irregular arrangement of the tab. In some other related technologies, the tab is mechanically flattened after the winding of the tab is completed, which can improve the regularity of the tab arrangement, but in the flattening process, metal scraps are easily generated between the tabs due to collision and extrusion, which may cause short circuit risk. CONTENT OF THE UTILITY MODEL

[0003] Embodiments of the present application provide an electrode assembly, a battery and an electric device to improve the problem that the tab in the electrode assembly cannot simultaneously reduce the generation of metal scraps and regular arrangement of the tab in the flattening process.

[0004] In a first aspect, embodiments of the present application provide an electrode assembly, comprising a winding body, the winding body comprising a winding arrangement of tabs, the tab comprising a tab body, a tab ear area and a transition area, the tab body being coated with an active material, the tab ear area and the transition area both being uncoated with the active material, the tab body being connected with the tab ear area through the transition area, the tab ear area comprising a plurality of tab ears arranged along the winding circumferential direction;

[0005] The tab ear area comprises a first section and a second section, one end of the first section is connected with one end of the transition area away from the tab body, the second section is connected with the other end of the first section away from the transition area, in the state that the tab ear area is flattened to the winding body, one of the first section and the second section is bent in the direction away from the winding center, and the other is bent in the direction close to the winding center.

[0006] In some embodiments of the present application, the length of the first section is d1, and the length of the second section is d2.

[0007] d2>d1.

[0008] In some embodiments of the present application, the winding body comprises a separation film, the separation film being wound between two adjacent tabs with different polarities, along the axial direction of the winding body, the separation film comprises a first end point close to the first section.

[0009] The first segment and the transition zone are connected to form a first bending point, the second segment and the first segment are connected to form a second bending point, and the distance between the first bending point and the first end point in the axial direction of the winding body is d3, and the distance between the second bending point and the first end point is Y1;

[0010] Wherein, Y1=d1×X±d3, X is a correction coefficient, X is greater than 0 and less than 1.

[0011] In some embodiments of the present application, when the first bending point is located on the side of the first end point close to the pole piece body, Y1, d1, d3 satisfy the following formula in the axial direction of the winding body:

[0012] Y1=d1×X-d3;

[0013] When the first bending point is located on the side of the first end point away from the pole piece body, Y1, d1, d3 satisfy the following formula in the axial direction of the winding body:

[0014] Y1=d1×X+d3.

[0015] In some embodiments of the present application, the pole piece includes a first pole piece and a second pole piece, the isolation film is arranged between the first pole piece and the second pole piece, the polarities of the first pole piece and the second pole piece are opposite, the thickness of the first pole piece is b1, the thickness of the second pole piece is b2, and the thickness of the isolation film is b3. The total thickness t of the adjacent first pole piece, second pole piece and two isolation films is b1+b2+2b3.

[0016] Wherein, the number of winding turns e1 covered by the first segment in the radial direction of the winding body satisfies:

[0017] e1≤d1÷t.

[0018] In some embodiments of the present application, the number of winding turns e2 covered by the second segment in the radial direction of the winding body satisfies:

[0019] e2≤d2÷t.

[0020] In some embodiments of the present application, the angle formed by the extension line of the first segment and the extension line of the second segment is greater than 0° and less than 30°.

[0021] In some embodiments of the present application, the proportion of the overlapping area between the two adjacent pole ears in the total area of the two pole ears in the same winding turn is S1, and the proportion of the overlapping area between the two adjacent pole ears in the total area of the two pole ears in the radial direction of the winding body is S2.

[0022] wherein S1 is in the range of 0 < S1 < 30%;

[0023] S2 = (d2 + d1 - d4 - t / cosθ) / (d1 + d2), and S2 is in the range of 50% < S2 < 95%;

[0024] d4 is the length of the non-overlapping portion between the adjacent two tabs in the radial direction of the winding body, and θ is the included angle formed by the extension line of the first segment and the extension line of the second segment.

[0025] In some embodiments of the present application, the plurality of tabs of the first tab are bent and stacked to form a first welding surface, and the thickness of the first welding surface that can be welded is greater than 0.04 mm and less than 1.2 mm;

[0026] The plurality of tabs of the second tab are bent and stacked to form a second welding surface, and the thickness of the second welding surface that can be welded is greater than 0.03 mm and less than 0.6 mm.

[0027] In some embodiments of the present application, the winding direction of the windingly arranged tab comprises, in sequence, an inner circumferential tab-free winding segment, a tabbed winding segment, and an outer circumferential tab-free winding segment, the maximum radius of the inner circumferential tab-free winding segment is r, the radius of the central hole formed by the winding body is r0, and the maximum tab height of the first tab of the tabbed winding segment in the winding direction is h1 < r - r0.

[0028] In some embodiments of the present application, the length of the inner circumferential tab-free winding segment in the winding direction satisfies: L2 ≥ L1 - L0; and the length of the outer circumferential tab-free winding segment in the winding direction satisfies: L5 ≥ L4 - L3.

[0029] wherein L0 refers to the virtual arc length of the spiral trajectory of the inner circumferential tab-free winding segment when winding with the radius of the central hole as the maximum radius, L1 refers to the minimum winding path length from the winding radius of 0 to the minimum winding radius of the inner circumferential tab-free winding segment, L2 refers to the length of the inner circumferential tab-free winding segment in the winding direction, L3 refers to the total winding length of the winding body from the winding radius of 0 to the radius at which the winding head of the outer circumferential tab-free winding segment is located, L4 refers to the winding path length from the winding radius of 0 to the maximum winding radius, and L5 refers to the length of the outer circumferential tab-free winding segment in the winding direction.

[0030] The L0, L1, L3, and L4 all satisfy the following formula:

[0031] L = (a / 2) × {φ·√(1+φ 2 ) + ln[φ+√(1+φ 2 )]}

[0032] wherein a is a helix parameter, and φ is a rotation angle.

[0033] In some embodiments of the present application, the stacking thickness of the first segments of the plurality of the tabs in the axial direction of the winding body satisfies: D1≤d1÷t×H;

[0034] The stacking thickness of the second segments of the plurality of the tabs in the axial direction of the winding body satisfies: D2≤d2÷t×H;

[0035] wherein D1 is the stacking thickness of the first segments of the plurality of the tabs in the axial direction of the winding body, D2 is the stacking thickness of the second segments of the plurality of the tabs in the axial direction of the winding body, and H is the thickness of the transition zone.

[0036] In some embodiments of the present application, a gap is formed between the first segments and the second segments of the tabs in the stacking direction, and the height of the gap in the stacking direction satisfies: D3=k1×D1+k2×D2;

[0037] The total stacking thickness of the first segments and the second segments of the plurality of the tabs after stacking satisfies: D4=D1+D2+D3;

[0038] wherein K1 and K2 are coefficients, K1 satisfies: 0.2

[0039] In some embodiments of the present application, the length of the tab body of the first tab is less than the length of the tab body of the second tab in the axial direction of the winding body, and the shortest distance between the tab body of the second tab and the first segment of the first tab is not greater than 5 mm.

[0040] In a second aspect, embodiments of the present application provide a battery, comprising a shell and an electrode assembly as described in the first aspect, wherein the electrode assembly is installed in the shell.

[0041] In a third aspect, embodiments of the present application provide a use-electric device, comprising a battery as described in the second aspect.

[0042] The beneficial effects of embodiments of the present application are as follows:

[0043] The application provides an electrode assembly, a battery and an electric device. The electrode assembly comprises a plurality of electrode tabs, and each of the electrode tabs comprises a first section and a second section. The first section and the second section are pre-bent towards different directions. In the flattening process of the winding body, the first section and the second section can be regularly flattened onto the electrode tab body according to the bending directions. The flattening process of the electrode tab does not involve the mechanical flattening process, so that the problem of metal scraps caused by the flattening process can be effectively avoided. In addition, because the first section and the second section are bent towards different directions, the first section and the second section can be flattened according to the bending directions in the flattening process, so that the distribution of the plurality of electrode tabs can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a structural schematic diagram of an electrode assembly provided by an embodiment of the application;

[0045] Figure 2 is a structural schematic diagram of adjacent electrode tabs in an electrode assembly (a state when the electrode tabs are not bent) provided by an embodiment of the application;

[0046] Figure 3 is a structural schematic diagram of adjacent electrode tabs in an electrode assembly (a state when the electrode tabs are bent) provided by an embodiment of the application;

[0047] Figure 4 is a structural schematic diagram of adjacent electrode tabs in an electrode assembly, in which a first bending point is located above a first end point, provided by an embodiment of the application;

[0048] Figure 5 is a structural schematic diagram of adjacent electrode tabs in an electrode assembly, in which a first bending point is located below a first end point, provided by an embodiment of the application;

[0049] Figure 6 is a structural schematic diagram of adjacent electrode tabs and isolation films in an electrode assembly provided by an embodiment of the application.

[0050] BRIEF DESCRIPTION OF DRAWINGS

[0051] 1, winding body; 11, electrode tab; 111, electrode tab body; 112, electrode tab area; 1121, first section; 1122, second section; 113, transition area; 114, first bending point; 115, second bending point; 116, inner peripheral non-electrode tab winding section; 117, outer peripheral non-electrode tab winding section; 118, electrode tab winding section; 12, isolation film; 121, first end point. DETAILED DESCRIPTION

[0052] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the contour of the device.

[0053] Please refer to Figure 1 , Figure 2 and Figure 3 The embodiment of the present application provides an electrode assembly, comprising a winding body 1. The winding body 1 comprises a winding electrode tab 11, the electrode tab 11 comprising an electrode tab body 111, an ear region 112 and a transition region 113. The electrode tab body 111 is coated with an active material, and the electrode tab body 111 is connected to the ear region 112 through the transition region 113. It should be noted that the electrode tab body 111, the transition region 113 and the ear region 112 are essentially part of the electrode tab 11, and are integrally formed, but the ear region 112 and the transition region 113 are not coated with an active material, the electrode tab body 111 is coated with an active material, and the main difference between the ear region 112 and the transition region 113 is whether to be bent, the ear region 112 needs to be bent, and the transition region 113 does not need to be bent, so the electrode tab 11 is divided into three parts. The ear region 112 further comprises a plurality of tabs spaced along the winding circumferential direction.

[0054] The ear region 112 comprises a first section 1121 and a second section 1122, one end of the first section 1121 is connected to the end of the transition region 113 away from the electrode tab body 111, the second section 1122 is connected to the end of the first section 1121 away from the transition region 113, and along the flattening direction of the ear region 112 towards the electrode tab body 111, the first section 1121 is bent towards the direction away from the winding center, and the second section 1122 is bent towards the direction of the winding center.

[0055] It should be noted that the flattening direction refers to the direction in which the machine for flattening the tab is pressed flat during the flattening process of the tab.

[0056] The technical scheme provided in the application divides the tab into a first section 1121 and a second section 1122, and pre-bends the first section 1121 and the second section 1122 towards different directions, so that the first section 1121 and the second section 1122 can be regularly flattened onto the tab body 111 according to the bending directions during the flattening process, the flattening process of the tab does not involve the mechanical flattening process, and the problem of metal chips caused by flattening is effectively avoided. In addition, because the first section 1121 and the second section 1122 are bent towards different directions, the first section 1121 and the second section 1122 can be flattened according to the bending directions when the tab is flattened, and the distribution of the plurality of tabs is improved. In detail, first, the active substance is coated on the tab 11, the tab 11 is divided into the tab body 111 coated with the active substance and the transition zone 113 and the tab zone 112 not coated with the active substance, and then the tab is bent to form the first section 1121 and the second section 1122. The first section 1121 is bent towards the direction away from the winding center, and the second section 1122 is bent towards the direction of the winding center. The bending direction is provided for the tab to be flattened regularly according to the bending direction.

[0057] In some embodiments, referring to Figure 2 and Figure 3 , the first section 1121 is bent towards the outer circle of the winding body, and the second section 1122 is bent towards the inner circle, thereby forming a double folding structure from the outside to the inside. This structure can effectively avoid the problem of disordered direction and distribution of the tab during the mechanical flattening process, and this structure also does not need to use the mechanical flattening method, but only needs to be directly flattened to form a regular tab distribution. Further, the length of the first section 1121 is d1, and the length of the second section 1122 is d2. Wherein, d2>d1. Specifically, the length of d1 ranges from 0 to 10 mm, and the length of d2 ranges from 0 to 20 mm. The first section 1121 and the second section 1122 are both pre-bent to a certain extent to ensure that the first section 1121 and the second section 1122 can be bent according to the predetermined direction during the flattening process. The first section 1121 can play a certain supporting role, and the first section 1121 and the second section 1122 are stacked and bent, which can effectively increase the thickness of the tab and facilitate subsequent welding.

[0058] Further, the winding body 1 comprises an isolation film 12, the isolation film 12 is wound between two adjacent pole pieces 11, along the axial direction of the winding body 1, the isolation film 12 comprises a first end point 121 close to the first section 1121. The first section 1121 and the transition zone form a first bending point 114, the second section 1122 and the first section 1121 form a second bending point 115, along the axial direction of the winding body 1, the distance between the first bending point 114 and the first end point 121 is d3, and the distance between the second bending point 115 and the first end point 121 is Y1.

[0059] Wherein, Y1 = d1 x X ± d3, X is a correction coefficient, X is greater than 0 and less than 1.

[0060] By arranging the isolation film 12 between the adjacent pole pieces 11, the risk of short circuit between the adjacent pole pieces 11 can be effectively avoided, and the bending part of the tab can also be supported and protected. By limiting the distance Y1 between the second bending point 115 and the first end point 121 and the distance between the first bending point 114 and the first end point 121 along the axial direction of the winding body 1, it can be ensured that the distribution of the bent tab does not interfere with the isolation film 12.

[0061] Further, please refer to Figure 4 and Figure 5 , along the axial direction of the winding body 1, when the first bending point 114 is below the first end point 121, Y1, d1, d3 satisfy the following formula:

[0062] Y1 = d1 x X - d3.

[0063] Along the axial direction of the winding body 1, when the first bending point 114 is above the first end point 121, Y1, d1, d3 satisfy the following formula:

[0064] Y1 = d1 x X + d3.

[0065] By reasonably calculating the distance between the first end point 121 and the second bending point 115 of the isolation film 12 according to the position of the first bending point 114 in the axial direction, the influence of the tab bending on the isolation film 12 can be effectively avoided.

[0066] In some embodiments, the pole piece 11 comprises a first pole piece and a second pole piece. The isolation film 12 is arranged between the first pole piece and the second pole piece, and the polarities of the first pole piece and the second pole piece are opposite. The thickness of the first pole piece is b1, the thickness of the second pole piece is b2, the thickness of the isolation film 12 is b3, and the total thickness of the adjacent first pole piece, second pole piece and two isolation films 12 is t = b1 + b2 + 2b3. Wherein, the number of winding turns covered by the second section 1122 along the radial direction of the winding body 1 satisfies: e2 ≤ d2 ÷ t.

[0067] Specifically, the first and second pole pieces are coated with active materials for electrochemical reactions of the positive and negative electrodes, respectively. One layer of the separator film 12 is located between the first and second pole pieces, and another layer of the separator film 12 is located on the side of the first pole piece away from the second pole piece or on the side of the second pole piece away from the first pole piece. The first and second pole pieces and the two layers of the separator film 12 together form a winding core basic unit, and the winding body 1 is formed by spirally winding a plurality of winding core basic units in the winding direction. The separator film 12 is usually made of porous polypropylene (PP) or polyethylene (PE) material. The number of winding turns is controlled by the ratio of the length of the second segment 1122 tab to the total thickness, the distribution of the tabs in the radial direction is more uniform, and the welding area is fully covered, thereby avoiding local overheating or stress concentration problems during the welding process. Under the premise of the same electrode assembly radius, an excessively thick t will reduce the stacking density of the tabs in the radial direction, which may affect the welding strength and may also cause the problem of burning of the separator film 12. An excessively thin t is difficult to process. By controlling a reasonable value of t, the welding strength and the overall performance of the battery are balanced.

[0068] In some embodiments, referring to Figure 6 , the number of winding turns covered by the first segment 1121 in the radial direction of the winding body 1 satisfies e1≤d1÷t, which is beneficial to improve the regularity of the first segment 1121 of the plurality of tabs after being bent and flattened.

[0069] In some embodiments, the extension line of the first segment 1121 and the extension line of the second segment 1122 form an included angle, and the angle of the included angle is greater than 0° and less than 30°. When the angle between the first segment 1121 and the second segment 1122 satisfies greater than 0° and less than 30°, it is beneficial to meet the regularity of the distribution of the tabs during the winding process, and also provides reasonable stacking support and stability during welding. Specifically, when the included angle is close to 0°, the first segment 1121 and the second segment 1122 tend to be parallel, resulting in excessively dense tab stacking and increasing local stress. When the included angle is close to 30°, the first segment 1121 and the second segment 1122 tend to separate, forming a larger distribution range, which is helpful to the uniformity of stacking, but an excessively large angle will increase the gap between the stacking areas, affecting the welding strength.

[0070] Further, the ratio of the overlapping area between the two adjacent tabs in the same winding turn to the total area of the two tabs is S1, and the ratio of the overlapping area between the two adjacent tabs to the total area of the two tabs in the radial direction of the winding body 1 is S2.

[0071] wherein S1 ranges from 0<S1<30%; S2=(d2+d1-d4-t / cosθ) / (d1+d2), and S2 ranges from 50%<S2<95%. d4 is the length of the non-overlapping part between the two adjacent tabs in the radial direction of the winding body 1.

[0072] The two adjacent tabs in the same winding circle will overlap, and the area ratio of the overlapping part is S1, which satisfies 0 < S1 < 30%. The two adjacent tabs in different winding circles will also overlap, and the area ratio of the overlapping part is S2, which satisfies: 50% < S2 < 95%. The specific calculation formula of S2 is as follows:

[0073] S2 = (d2 + d1 - d4 - t / cosθ) / (d1 + d2).

[0074] Wherein, d1 and d2 are the lengths of the first segment 1121 and the second segment 1122 respectively; d4 is the length of the non-overlapping part between the two adjacent tabs in the winding radial direction; t is the thickness of the winding core basic unit; θ is the included angle formed by the extension line of the first segment 1121 and the extension line of the second segment 1122. In the same winding circle, due to the close distribution of adjacent tabs, local overlap of the tabs occurs. By controlling the overlapping area to be 0%-30%, the problem of excessive thickness of the stacked thickness caused by excessive overlap can be avoided, while the compactness of the structure is ensured. The tabs of adjacent winding circles overlap in the radial direction, and the overlapping area ratio ranges from 50% to 95%. This proportion is set to improve the welding strength of the stack, while avoiding excessive gaps between adjacent tabs, ensuring the uniformity and supportability of the overall stack.

[0075] By limiting the range of S1 and S2, the compactness of the tab stack is ensured, while avoiding the problems of excessive local pressure caused by excessive stacking density or unstable welding caused by excessive loose stacking. S1 controls the overlap ratio of the tabs in the same winding circle. If the value is too large (such as > 30%), it will cause the thickness of the stacked area to increase significantly, affecting the uniformity of the stack, and there is a risk of end face defects, tab folding, and uncontrolled process. S2 controls the overlap ratio of the tabs between adjacent winding circles. If the value is too small (such as < 50%), it will result in insufficient welding strength of the stacked area and increased internal resistance. If the value is too large (such as > 95%), it will increase the difficulty of the process, affecting the electrode performance. The calculation formula of S2 clearly defines the overlap relationship between adjacent tabs, making the thickness and distribution of the welding area more uniform, and reducing the risk of failure caused by thermal stress during welding.

[0076] In some embodiments, referring to Figure 1 , the tab 11 arranged by winding includes an inner circumferential tab-free winding segment 116, a tabbed winding segment 118, and an outer circumferential tab-free winding segment 117 connected in sequence in the winding direction. The maximum radius of the inner circumferential tab-free winding segment 116 is r, the radius of the central hole formed by the winding body 1 is r0, and the maximum tab height of the first tab of the tabbed winding segment 118 in the winding direction is h1 < r - r0.

[0077] Further, the length of the tab in the axial direction is in the range of 1-6 mm. The length of the plurality of tabs in the axial direction can be the same or gradually increase in the winding direction. If gradually increasing, the length difference of the adjacent tabs in the axial direction is in the range of 0.2-2 mm in the winding direction. The shape of the tab can be rectangular, trapezoidal or other irregular shape, which is not limited. After the winding body 1 is formed, the tab is also wound with the winding of the tab body 111, and the curvature of the tab after winding is less than 30°, and the curvature difference of the tabs of the adjacent two turns is less than 3°.

[0078] It should be noted that the inner peripheral tab-free winding section 116 refers to the part of the winding body 1 close to the winding center in the winding direction and without tabs, the outer peripheral tab-free winding section 117 refers to the part of the winding body 1 close to the winding edge in the winding direction and without tabs, and the tabbed winding section 118 refers to the part of the winding body between the inner peripheral tab-free winding section 116 and the outer peripheral tab-free winding section 117 in the winding direction.

[0079] By providing the inner peripheral tab-free winding section 116, the stability of the core of the electrode assembly is optimized. By providing the outer peripheral tab-free winding section 117, the outer circle of the electrode assembly is protected and stress concentration is reduced. After the flattening process is performed, the second section 1122 is flattened, according to the formula h1

[0080] According to the spiral line parameter calculation formula: a = t ÷ 2π, where t is the thickness of the core basic unit. For the electrode assembly, t is equivalent to the thickness of the first tab, the second tab (generally the thickness of the first tab is 50-200 um; the thickness of the second tab is 50-250 um) and the thickness of the two layers of isolation film 12. The relationship between the radius r of the core and the rotation angle φ of the core corresponding to the radius satisfies: r = r0 + a·φ. Wherein, r0 is the center hole radius. According to the Archimedes spiral theory, the following formula can be used to calculate the virtual arc length of the spiral trajectory of the inner peripheral tab-free winding section 116, the minimum arc length of the inner peripheral tab-free winding section 116, the winding length of the winding body 1 in the winding direction, and the total winding length of the winding body 1 from the winding radius of 0 to the winding starting radius of the outer peripheral tab-free winding section 117, taking the radius of the center hole as the maximum radius. The specific formula is:

[0081] L = (a / 2) × {φ·√(1+φ2) + ln[φ+√(1+φ2)]}.

[0082] Further, the length of the inner-lead-free winding section 116 in the winding direction satisfies: L2≥L1-L0. The length of the outer-lead-free winding section 117 in the winding direction satisfies: L5≥L4-L3.

[0083] wherein L0 refers to a virtual arc length of the spiral track of the inner-lead-free winding section 116 simulated with the radius of the center hole as the maximum radius, L1 refers to a minimum winding path length from a winding radius of 0 to the minimum radius of the inner-lead-free winding section 116, L2 refers to the length of the inner-lead-free winding section 116 in the winding direction, L3 refers to the total winding length of the winding body 1 from a winding radius of 0 to the radius at which the winding head of the outer-lead-free winding section 117 is located, L4 refers to a winding path length from a winding radius of 0 to the maximum winding radius, and L5 refers to the length of the outer-lead-free winding section 117 in the winding direction.

[0084] According to the foregoing embodiments, it can be known that L0, L1, L3, and L4 all satisfy the following formula:

[0085] L=(a / 2)×{φ·√(1+φ2)+ln[φ+√(1+φ2)]}, a is a spiral line parameter, and φ refers to a rotation angle.

[0086] It should be noted that, before L4-L3 is used to calculate the length of the outer-lead-free winding section 117 in the winding direction, L4 and L3 need to be calculated. The calculation of L4 and L3 is different from the calculation of L0 and L1 described above. Specifically, the maximum radius of the winding body 1 is r3, and it can be known from the polar coordinate formula that the total rotation angle φ1 of the winding body 1 satisfies: φ1=r3 / a, and the total rotation angle includes the winding angle of the center virtual part of the winding body 1. The outer-lead-free winding section 117 of the winding body 1 has an outer-lead-free cutting number e3, and the total rotation angle of the winding body 1 from a winding radius of 0 to the radius at which the winding head of the outer-lead-free winding section 117 is located is φ2=r3 / a-2π·e3. Based on the obtained rotation angle and spiral line parameter, the rotation angle and the spiral line parameter are respectively brought into the two formulas of L=(a / 2)×{φ·√(1+φ2)+ln[φ+√(1+φ2)]} and L5≥L4-L3, and the length of the outer-lead-free winding section 117 in the winding direction can be obtained.

[0087] In some embodiments, referring to Figure 6 , the stacking thickness of the first section 1121 of the plurality of lead ears in the axial direction of the winding body 1 satisfies: D1≤d1÷t×H.

[0088] The stacking thickness of the second section 1122 of the plurality of lead ears in the axial direction of the winding body 1 satisfies: D2≤d2÷t×H.

[0089] D1 is the stacking thickness of the first section 1121 of the plurality of tabs in the axial direction of the winding body 1, D2 is the stacking thickness of the second section 1122 of the plurality of tabs in the axial direction of the winding body 1, and H is the thickness of the transition region 113.

[0090] By limiting the stacking thickness of the first section 1121 and the stacking thickness of the second section 1122 in the axial direction of the winding body 1, the stacking uniformity of the tabs in the axial direction is ensured, and the mechanical instability problem caused by excessive or insufficient stacking thickness is reduced.

[0091] Further, a gap is formed between the stacking of the first section 1121 and the second section 1122 of the tabs, and the height of the gap in the stacking direction satisfies: D3=k1xD1+k2xD2. The total stacking thickness after the stacking of the first section 1121 and the second section 1122 of the plurality of tabs satisfies: D4=D1+D2+D3. Wherein, K1 and K2 are coefficients, K1 satisfies: 0.2

[0092] In some embodiments, the plurality of tabs of the first tab are folded and stacked to form a first welding surface, and the welding thickness of the first welding surface is greater than 0.04 mm and less than 1.2 mm. The plurality of tabs of the second tab are folded and stacked to form a second welding surface, and the welding thickness of the second welding surface is greater than 0.03 mm and less than 0.6 mm.

[0093] In some embodiments, in the axial direction of the winding body 1, the length of the tab body 111 of the first tab is less than the length of the tab body 111 of the second tab, and the distance between the tab body 111 of the second tab and the first section 1121 of the first tab is D5, D5≤5 mm. By limiting the distance between the tab body 111 of the second tab and the first section 1121 of the first tab to be not greater than 5 mm, the safety margin of the battery is improved to cope with possible abnormal tab layout situations, such as abnormal folding and lodging between the upper and lower tabs in this area, and to cope with the expansion of the electrode assembly. A margin is left for the expansion of the electrode assembly in the axial direction.

[0094] Embodiments of the present application also provide a battery, which can be a cylindrical battery. The battery comprises a shell and an electrode assembly as described in any of the preceding embodiments, and the electrode assembly is installed in the shell. The battery has the structure of the electrode assembly and the corresponding beneficial effects described in the preceding embodiments, which will not be repeated here.

[0095] The embodiments of the present application also provide a power-using device, which comprises the battery described in the foregoing embodiments. The power-using device has the structure of the battery described in the foregoing embodiments and corresponding advantages, which will not be described herein again.

[0096] The embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples. The above embodiment descriptions are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present description should not be understood as a limitation of the present application.

Claims

1. An electrode assembly, characterized in that, The invention includes a winding body, the winding body including a wound electrode sheet, the electrode sheet including an electrode sheet body, an electrode tab region and a transition region, the electrode sheet body being coated with an active material, the electrode tab region and the transition region not being coated with an active material, the electrode sheet body and the electrode tab region being connected through the transition region, and the electrode tab region including a plurality of electrodes tabs arranged along the winding circumference; The tab region includes a first segment and a second segment. One end of the first segment is connected to the end of the transition region away from the electrode body, and the second segment is connected to the other end of the first segment away from the transition region. When the tab region is flattened to the winding body, one of the first segment and the second segment bends away from the winding center, and the other bends towards the winding center.

2. The electrode assembly as described in claim 1, characterized in that, The length of the first segment is d1, and the length of the second segment is d2; Where d2 > d1.

3. The electrode assembly as described in claim 2, characterized in that, The wound body includes a separator film, which is wound between two adjacent electrodes of different polarities. Along the axial direction of the wound body, the separator film includes a first end point near the first segment. A first bend point is formed at the connection between the first segment and the transition zone, and a second bend point is formed at the connection between the second segment and the first segment. Along the axial direction of the winding body, the distance between the first bend point and the first end point is d3, and the distance between the second bend point and the first end point is Y1. Where Y1 = d1 × X ± d3, and X is a correction coefficient, which is greater than 0 and less than 1.

4. The electrode assembly as described in claim 3, characterized in that, Along the axial direction of the wound body, when the first bending point is located on the side of the first end point closer to the electrode body, Y1, d1, and d3 satisfy the following formula: Y1 = d1 × X - d3; Along the axial direction of the wound body, when the first bending point is located on the side of the first end point away from the electrode body, Y1, d1, and d3 satisfy the following formula: Y1 = d1 × X + d3.

5. The electrode assembly as described in claim 3 or 4, characterized in that, The electrode includes a first electrode and a second electrode, and the separator is disposed between the first electrode and the second electrode. The first electrode and the second electrode have opposite polarities. The first electrode has a thickness of b1, the second electrode has a thickness of b2, and the separator has a thickness of b3. The total thickness of adjacent first electrodes, second electrodes and two separators is t = b1 + b2 + 2b3. Wherein, the number of winding turns e1 covered by the first segment along the radial direction of the wound body satisfies: e1≤d1÷t.

6. The electrode assembly as claimed in claim 5, characterized in that, The number of turns e2 covered by the second segment along the radial direction of the wound body satisfies: e2≤d2÷t.

7. The electrode assembly as described in claim 5, characterized in that, The angle formed by the extension of the first segment and the extension of the second segment is greater than 0° and less than 30°.

8. The electrode assembly as claimed in claim 7, characterized in that, The percentage of the overlapping area between two adjacent tabs in the same winding loop to the total area of ​​the two tabs is S1, and the percentage of the overlapping area between two adjacent tabs to the total area of ​​the two tabs along the radial direction of the winding body is S2. Wherein, the range of S1 is 0 < S1 < 30%; S2 = (d2 + d1 - d4 - t / cosθ) / (d1 + d2), and the range of S2 is 50% < S2 < 95%; d4 is the length of the non-overlapping portion between two adjacent tabs along the radial direction of the winding body, and θ is the angle formed by the extensions of the first segment and the second segment.

9. The electrode assembly as claimed in claim 5, characterized in that, The first electrode sheet is formed by bending and stacking multiple tabs to form a first welding surface. The thickness range that can be welded on the first welding surface is greater than 0.04 mm and less than 1.2 mm. The second electrode sheet is formed by bending and stacking multiple tabs to form a second welding surface. The thickness range that can be welded on the second welding surface is greater than 0.03 mm and less than 0.6 mm.

10. The electrode assembly as claimed in claim 1, characterized in that, The electrode sheet with winding configuration includes an inner peripheral electrodeless winding section, a electrode winding section, and an outer peripheral electrodeless winding section connected in sequence along the winding direction. The maximum radius of the inner peripheral electrodeless winding section is r, and the radius of the central hole formed by the winding body is r0. Along the winding direction, the maximum electrode height of the first electrode of the electrode winding section is h1 < r - r0.

11. The electrode assembly as claimed in claim 10, characterized in that, The length of the inner circumferential electrodeless winding section in the winding direction satisfies: L2≥L1-L0; the length of the outer circumferential electrodeless winding section in the winding direction satisfies: L5≥L4-L3; Wherein, L0 refers to the virtual arc length of the inner circumferential electrodeless winding segment, which is wound with the radius of the center hole as the maximum radius, simulating the spiral trajectory of the inner circumferential electrodeless winding segment; L1 refers to the minimum winding path length from the winding radius of 0 to the minimum radius of the inner circumferential electrodeless winding segment; L2 refers to the length of the inner circumferential electrodeless winding segment in the winding direction; L3 refers to the total winding length of the winding body from the winding radius of 0 to the radius of the winding start end of the outer circumferential electrodeless winding segment; L4 refers to the winding path length from the winding radius of 0 to the maximum winding radius; and L5 refers to the length of the outer circumferential electrodeless winding segment in the winding direction. L0, L1, L3, and L4 all satisfy the following formula: L=(a / 2)×{φ·√(1+φ 2 )+ln[φ+√(1+φ 2 )]}; Where 'a' is the helix parameter and 'φ' is the rotation angle.

12. The electrode assembly as claimed in claim 5, characterized in that, The stacking thickness of the first segment of the plurality of said tabs in the axial direction of the winding body satisfies: D1≤d1÷t×H; The stacking thickness of the second segment of the plurality of said tabs in the axial direction of the winding body satisfies: D2≤d2÷t×H; Wherein, D1 refers to the stacking thickness of the first segment of the plurality of electrodes in the axial direction of the winding body, D2 refers to the stacking thickness of the second segment of the plurality of electrodes in the axial direction of the winding body, and H refers to the thickness of the transition zone.

13. The electrode assembly as claimed in claim 12, characterized in that, A gap is formed between the first and second stacked segments of the electrode tab, and the height of the gap in the stacking direction satisfies: D3=k1×D1+k2×D2; The total stacking thickness of the first and second segments of the plurality of electrodes after stacking satisfies: D4 = D1 + D2 + D3; Wherein, K1 and K2 are both coefficients, wherein K1 satisfies: 0.2 < K1 < 2, and K2 satisfies: 0.2 < K2 < 2.

14. The electrode assembly as claimed in claim 5, characterized in that, Along the axial direction of the winding body, the length of the electrode body of the first electrode is less than the length of the electrode body of the second electrode, and the shortest distance between the electrode body of the second electrode and the first segment of the first electrode is no greater than 5 mm.

15. A battery, characterized in that, It includes a housing and an electrode assembly as described in any one of claims 1 to 14, the electrode assembly being mounted within the housing.

16. An electrical appliance, characterized in that, Includes the battery as described in claim 15.

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