Wound battery and lithium ion secondary battery

Abstract

The utility model relates to the technical field of batteries, and discloses a winding battery and a lithium ion secondary battery, the winding battery is formed by laminating and winding a positive plate, a diaphragm and a negative plate, and the negative plate comprises a straight area and arc areas positioned on two sides of the straight area along a first direction; the negative pole piece comprises a pole piece body, the negative pole piece comprises a negative pole current collector and a negative pole active layer arranged on at least one side of the negative pole current collector, and the negative pole active layer is at least provided with a wire slot part at a position corresponding to the straight area; a punching part is formed in the position, corresponding to the arc area, of the pole piece body. According to the winding battery provided by the utility model, the infiltration and storage of the pole pieces to electrolyte can be improved, the dynamics can be improved, the two sides of the pole pieces are communicated, so that the electrolyte can be accommodated among the pole pieces, the electrolyte can permeate more quickly, lithium ions can be transmitted more quickly, the problem of lithium precipitation in an arc area is solved, the overall stability of a battery cell is ensured, and the deformation degree of the battery is relieved; meanwhile, the purposes of reducing battery impedance, improving multiplying power, prolonging battery life and the like are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of battery, concretely relates to a winding battery and lithium ion secondary battery. BACKGROUND

[0002] In the field of batteries, although graphite negative electrode is still mainstream, its energy density has approached the limit. In order to solve the problems of endurance and energy supplement, the application of silicon-based negative electrode is gradually increasing.

[0003] However, although the silicon-based negative electrode has excellent energy density, when silicon is completely lithiated, the volume of silicon will expand by more than 300%. For winding batteries, especially silicon-doped negative electrode batteries, the middle region of the winding core is poorly infiltrated, and the infiltration effect is worse under high compaction. Although the negative electrode sheet is treated by wire punching in the related technology, the storage capacity of the electrolyte is improved, but as the number of cycles increases, the cycle expansion increases, and there are still problems such as easy lithium precipitation in the circular arc area. SUMMARY

[0004] Therefore, the utility model provides a winding battery and lithium ion secondary battery to solve the problem of easy lithium precipitation in the circular arc area of the silicon-doped negative electrode winding battery.

[0005] In a first aspect, the utility model provides a winding battery, which is formed by stacking and winding a positive electrode sheet, a separator and a negative electrode sheet, the negative electrode sheet includes a flat area and a circular arc area located on both sides of the flat area along a first direction;

[0006] The negative electrode sheet includes a sheet body, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, and the negative electrode active layer is provided with a wire slot part at least at a position corresponding to the flat area;

[0007] The sheet body is provided with a punching part at a position corresponding to the circular arc area.

[0008] In an optional embodiment, the negative electrode sheet includes a tab connected to the sheet body;

[0009] The negative electrode active layer includes a first recess, and the tab is located in the first recess and electrically connected to the negative electrode current collector;

[0010] The number of punching parts is at least one, a plurality of punching parts adjacent to the same circular arc area form a punching area, the width of the punching area along the first direction is W1, and it satisfies: 0

[0011] In an optional embodiment, the width of the circular arc area corresponding to the punching area along the first direction is F, and it satisfies: W1

[0012] In an optional embodiment, the projection of the punching region on the pole piece body at least partially overlaps with the circular arc region, and at least partially overlaps with at least part of the flat region located on both sides of the circular arc region along the first direction;

[0013] The width of the pole piece body along the second direction is W, wherein the second direction is perpendicular to the first direction;

[0014] The width of the part of the punching region overlapping with the flat region in the projection of the pole piece body along the first direction is G, satisfying: 500 μm≤G≤W / 2.

[0015] In an optional embodiment, the distance between the punching region along the second direction and the edge of the pole piece body is J, satisfying: 0.5 mm≤J≤5 mm.

[0016] In an optional embodiment, the center distance between two adjacent punching portions is D1, satisfying: 100 μm≤D1≤2000 μm.

[0017] And / or; the aperture of the punching portion is D4, satisfying: 30 μm≤D4≤200 μm.

[0018] In an optional embodiment, the punching portion includes a through hole and / or a non-through hole,

[0019] wherein the depth of the through hole is the same as the thickness of the pole piece body, and the depth of the non-through hole is less than the thickness of the pole piece body.

[0020] In an optional embodiment, the number of punching portions is at least one, and multiple punching portions adjacent to the same circular arc region form a punching region;

[0021] The number of wire slot portions is at least one, and multiple wire slot portions close to each other jointly form a wire slot region;

[0022] The wire slot region is arranged apart from the punching region along the first direction;

[0023] The minimum distance between the wire slot portion and the adjacent punching portion along the first direction is D3, satisfying: 200 μm<D3≤1000 μm.

[0024] In an optional embodiment, the number of wire slot portions is at least one, and multiple wire slot portions close to each other jointly form a wire slot region; the wire slot region covers the entire surface of the negative active layer.

[0025] In an optional embodiment, the number of wire slot portions is at least one, and multiple wire slot portions close to each other jointly form a wire slot region;

[0026] At least one punching portion is located in the wire slot region.

[0027] In an alternative embodiment, the extension direction of the wire slot portion is parallel to the first direction, or the extension direction of the wire slot portion is perpendicular to the first direction, or the extension direction of the wire slot portion is at an angle to the first direction.

[0028] In an alternative embodiment, the number of wire slot portions is multiple, and the spacing between adjacent wire slot portions in the direction perpendicular to the extension direction of the wire slot portion is D2, which satisfies: 500 μm≤D2≤3000 μm.

[0029] In an alternative embodiment, the ratio between the depth of the wire slot portion and the thickness of the active material layer on the side where the wire slot portion is formed, in the direction perpendicular to the thickness direction of the pole piece body, ranges from 0.1 to 0.5.

[0030] In an alternative embodiment, the depth of the wire slot portion, in the direction perpendicular to the thickness direction of the pole piece body, ranges from 5 μm to 30 μm.

[0031] In an alternative embodiment, the negative pole piece comprises a negative active material, the negative active material comprises a silicon-based material, and the silicon content in the negative active material ranges from 5% to 50%.

[0032] In an alternative embodiment, the positive pole piece and the negative pole piece are both provided with a punching portion at the position corresponding to the circular arc region.

[0033] The punching portion of the positive pole piece coincides with and / or is staggered with the punching portion of the negative pole piece.

[0034] In an alternative embodiment, the ratio between the length of the wound battery along the first direction and the width along the second direction ranges from 0.3 to 1.5.

[0035] In a second aspect, the utility model further provides a lithium ion secondary battery, which comprises the wound battery as described above.

[0036] Advantages:

[0037] 1. The wound battery provided by the embodiments of the utility model can improve the impregnation and storage of electrolyte by the pole piece, improve the kinetics, etc., facilitate the accommodation of electrolyte between the pole pieces by penetrating through the two sides of the pole piece, make the electrolyte penetrate faster, and make the lithium ions transmit faster, thereby improving or solving the lithium precipitation problem in the circular arc region, ensuring the stability of the whole battery cell, relieving the deformation degree of the battery, and achieving the purposes of reducing the impedance of the battery, improving the rate, improving the service life of the battery, etc.

[0038] 2. The winding battery provided by the embodiment of the utility model, the pole piece body is provided with the punching part in the position corresponding to the circular arc area and adjacent to the pole lug along the first direction, so that after the winding of the pole piece body is completed, the punching part is in the circular arc area, and the punching part is more adjacent to the pole lug, which can facilitate the faster penetration of electrolyte, faster transmission of lithium ions, meet the demand of current density near the pole lug position, greatly improve the lithium precipitation problem of the circular arc area, and further improve the battery deformation caused by lithium precipitation and reduce the battery cycle expansion.

[0039] 3. By providing the wire slot part on the pole piece body, the wire slot part is formed by locally thinning the pole piece body along the thickness direction of the pole piece body, so that the wire slot part can store electrolyte and make ions transmit faster, improve dynamics, and store more electrolyte in the wire slot part without increasing the liquid storage amount, avoiding poor electrolyte infiltration. By providing the wire slot part, the cycle capacity retention rate of the battery can be significantly improved, but only providing the wire slot part on the pole piece body can cause high cycle expansion and cannot solve the lithium precipitation problem of the circular arc area. Further, the embodiment provides the punching part on the position corresponding to the circular arc area of the pole piece body, and the punching part is preferably a through hole, which can penetrate the two sides of the pole piece body, make lithium ions transmit faster, and make electrolyte penetrate faster, thereby improving or solving the lithium precipitation problem of the circular arc area. In addition, the punching part can increase the electrolyte backflow channel, make electrolyte flow back quickly, improve the rate performance, reduce the cycle expansion, and significantly improve the lithium precipitation problem of the circular arc area. The embodiment combines the wire slot part and the punching part on the pole piece body, which can compensate for each other's deficiencies, improve the cycle capacity retention rate of the battery, improve the rate performance, reduce the cycle expansion, and significantly improve the lithium precipitation problem of the circular arc area. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the specific embodiments of the utility model or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description, and obviously, the drawings in the following description are some embodiments of the utility model, and those skilled in the art can obtain other drawings according to these drawings without creating labor.

[0041] Figure 1 It is the front view of the winding battery of the utility model;

[0042] Figure 2 It is the bottom view of the winding battery of the utility model;

[0043] Figure 3 It is the schematic of the pole piece when the pole piece is in the unfolded state, and the wire slot area is arranged in the whole region of the pole piece Figure 1 ;

[0044] Figure 4 Schematic view of the whole area of the pole piece being provided with the wire slot area in the unfolded state of the pole piece of the utility model Figure 2 ;

[0045] Figure 5 Schematic view of the whole area of the pole piece being provided with the wire slot area in the unfolded state of the pole piece of the utility model Figure 3 ;

[0046] Figure 6 Schematic view of the wire slot area and the punching area of the pole piece being arranged at intervals in the unfolded state of the pole piece of the utility model Figure 1 ;

[0047] Figure 7 Schematic view of the wire slot area and the punching area of the pole piece being arranged at intervals in the unfolded state of the pole piece of the utility model Figure 2 ;

[0048] Figure 8 Schematic view of the wire slot area and the punching area of the pole piece being arranged at intervals in the unfolded state of the pole piece of the utility model Figure 3 ;

[0049] Figure 9 Schematic view of the punching area exceeding the arc area in the unfolded state of the pole piece of the utility model

[0050] Figure 10 Cross-sectional view of the winding battery of the utility model.

[0051] Explanation of reference signs:

[0052] 1, pole piece; 11, pole piece body; 12, pole tab; 13, first groove;

[0053] 101, flat area; 102, arc area;

[0054] 21, punching part; 22, wire slot part;

[0055] 301, punching area; 302, wire slot area;

[0056] 91, diaphragm; 92, positive pole piece; 93, negative pole piece. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely below in combination with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without creative labor fall within the protection scope of the utility model.

[0058] In the description of the utility model, it needs to explain, the term "center", "upper", "lower", "left", "right", "vertical", "horizontal", "internal", "external" and so on indicate the orientation or position relation is based on the orientation or position relation shown in the drawing, only for the convenience of describing the utility model and simplifying the description, and not indicate or imply that the device or element must have a particular orientation, with a particular orientation structure and operation, therefore cannot be understood as a limitation on the utility model. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0059] In the description of the utility model, it needs to explain, unless otherwise explicitly provided and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected, can be mechanical connection, can also be electrical connection, can be directly connected, can also be indirectly connected through intermediate medium, can be the communication between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0060] In addition, the technical features involved in different embodiments of the utility model described below can be combined with each other as long as there is no conflict.

[0061] In the field of batteries, although graphite negative electrode is still the mainstream, its energy density has approached the limit. In order to solve the problem of endurance and energy supplement, the application of silicon-based negative electrode is gradually increasing. The lithium storage mechanism of silicon negative electrode material is different from that of graphite negative electrode material, which mainly forms Li12Si7, Li13Si4, Li7Si3, Li22Si5 and other alloy phases with lithium, among which the alloy phase with the highest lithium content is Li22Si5, silicon and lithium complete alloying reaction, one silicon atom can alloy with 4.4 lithium, and its theoretical specific capacity is as high as 4200mAh / g, which is about 10 times that of graphite negative electrode, and it is a kind of lithium ion battery negative electrode material with very high specific capacity.

[0062] However, while silicon-based anodes possess superior energy density, the severe volume effect of silicon during lithiation is currently the main factor restricting the widespread application of silicon-based materials. Silicon expands by over 300% in volume during complete lithiation. For wound batteries, especially those with silicon-doped anodes, the wetting in the central region of the winding is poor, and the wetting effect worsens under high compaction. If the electrolyte, acting as a channel for lithium ion conduction, is insufficient or fails to adequately wet the electrode, the migration path of lithium ions between the positive and negative electrodes will be obstructed, easily leading to lithium plating. Although related technologies employ wire bonding to improve electrolyte storage capacity, with increasing cycle counts, cyclic expansion further encroaches on the space originally intended for electrolyte storage, still resulting in problems such as lithium plating in the arc-shaped regions.

[0063] The wound battery provided by the embodiments of this utility model can improve the wetting and storage of electrolyte on the electrode, improve kinetics, etc. By making the two sides of the electrode open, it is beneficial for the electrolyte to be contained between the electrode, so that the electrolyte can penetrate faster and lithium ions can be transported faster, thereby improving or solving the problem of lithium deposition in the arc area, ensuring the overall stability of the cell, alleviating the degree of battery deformation, and achieving the purpose of reducing battery impedance, increasing rate, and improving battery life.

[0064] For ease of description and understanding of the present invention, it should be noted that the first direction and the second direction refer to those shown in the appendix. Figure 1 The directions shown are such that the first direction can be the length direction of the wound battery, and the second direction can be the width direction of the wound battery. Since the electrode 1 of the wound battery is formed by winding, it is further combined with... Figure 3 When the electrode body 11 is in the unfolded state, the first direction can be the length direction of the electrode 1, and the second direction can be the width direction of the electrode 1. The thickness direction of the electrode 1 can be a direction that is perpendicular to both the first and second directions.

[0065] The following is combined Figures 1 to 10 The following describes embodiments of the present invention.

[0066] According to an embodiment of the present invention, in one aspect, a wound battery is provided, which is formed by stacking and winding a positive electrode 92, a separator 91 and a negative electrode 93. The negative electrode 93 includes a flat region 101 and an arc region 102 located on both sides of the flat region 101 along a first direction.

[0067] The negative electrode 93 includes an electrode body 11, a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, and the negative electrode active layer has a groove portion 22 at least at the position corresponding to the flat region 101.

[0068] The electrode body 11 has a perforated portion 21 at the position corresponding to the arc area 102.

[0069] The negative electrode active layer has a groove portion 22 at least at the position corresponding to the flat region 101. The groove portion 22 is formed by locally thinning the negative electrode active layer along its own thickness direction.

[0070] It should be noted that the negative electrode active layer and the electrode body 11 have at least a partial overlap, but the electrode body 11 may still have some areas without the negative electrode active layer. Since the electrode body 11 contains the negative electrode active layer, the negative electrode active layer defined here has a groove 22 at least at the position corresponding to the flat region 101. More broadly, the electrode body 11 may also have a groove 22 at least at the position corresponding to the flat region 101.

[0071] First, combine Figure 1 , Figure 2 As shown, after the wound battery is wound, an arc surface is formed at the bending position of the electrode 1. When the arc surfaces of each layer of electrode are accumulated at the bending position, a wound cell with arc-shaped sides and a straight middle is finally formed. That is, the arc-shaped areas 102 located on both sides of the first direction, and the straight area 101 located between the arc-shaped areas 102 on both sides of the first direction. The wound battery is divided into arc-shaped areas 102 and straight areas 101 according to its external shape. The arc-shaped areas 102 are constructed as arc surfaces and are distributed on both sides of the wound battery along the first direction; the straight area 101 is constructed as a straight shape and is located between the arc-shaped areas 102 on both sides of the first direction. Further, the negative electrode 93 includes a straight area 101 and arc-shaped areas 102 located on both sides of the straight area 101 along the first direction; as Figure 10 As shown, the flat area located in the middle of the wound battery is the flat area 101, and the arc-shaped areas located on both sides of the wound battery along the first direction are the arc-shaped areas 102.

[0072] In this embodiment, the negative electrode active layer has a groove 22 at least at the position corresponding to the flat region 101. The groove 22 is formed by locally thinning the negative electrode active layer along its own thickness direction. Alternatively, the groove 22 can be provided in the entire area of ​​the negative electrode active layer, and is not limited to the flat region 101. The arrangement of the groove 22 will be described in detail below.

[0073] By creating grooves 22 in the negative electrode active layer, which are formed by locally thinning the negative electrode active layer along its own thickness direction, electrolyte can be stored within the grooves 22. This allows for faster ion transport and improves kinetics. Without increasing the electrolyte retention capacity, more electrolyte is stored within the grooves 22, avoiding poor electrolyte wetting. While the grooves 22 significantly improve the battery's cycle capacity retention, simply creating grooves 22 on the negative electrode active layer leads to higher cycle expansion and does not solve the lithium plating problem in the arc region 102.

[0074] Further, the embodiment can solve the problem of lithium precipitation in the circular arc area 102 by opening the punching part 21 on the position corresponding to the circular arc area 102 of the pole piece body 11. The punching part 21 is preferably a through hole, which can pass through the pole piece body 11 on both sides, so that lithium ions can be transmitted faster and electrolyte can penetrate faster, thereby improving or solving the problem of lithium precipitation in the circular arc area 102. Moreover, by opening the punching part 21, the electrolyte reflux channel can be increased, the electrolyte can quickly reflux, the rate capability is better, the cycle expansion can be reduced, and the lithium precipitation in the circular arc area can be significantly improved.

[0075] The embodiment can solve the problem of lithium precipitation in the circular arc area 102 by opening the punching part 21 on the position corresponding to the circular arc area 102 of the pole piece body 11. The punching part 21 is preferably a through hole, which can pass through the pole piece body 11 on both sides, so that lithium ions can be transmitted faster and electrolyte can penetrate faster, thereby improving or solving the problem of lithium precipitation in the circular arc area 102. Moreover, by opening the punching part 21, the electrolyte reflux channel can be increased, the electrolyte can quickly reflux, the rate capability is better, the cycle expansion can be reduced, and the lithium precipitation in the circular arc area can be significantly improved.

[0076] The cycle capacity retention rate refers to the ability of the battery to maintain a certain level of capacity retention after a certain number of charge and discharge cycles. It is one of the important indicators for measuring the performance of the battery. The higher the cycle capacity retention rate, the better the durability and stability of the battery, and the higher the energy output can be maintained for a long time.

[0077] The cycle capacity retention rate refers to the ability of the battery to maintain a certain level of capacity retention after a certain number of charge and discharge cycles. It is one of the important indicators for measuring the performance of the battery. The higher the cycle capacity retention rate, the better the durability and stability of the battery, and the higher the energy output can be maintained for a long time.

[0078] The battery rate capability refers to the performance of the battery at different charge and discharge rates. It describes the ability of the battery to complete charge and discharge within a certain time. Specifically, the battery rate is expressed in multiples of the rated capacity to represent the discharge rate, i.e. the current value required by the battery to discharge the rated capacity within a specified time. For example, 1C means that the battery can be completely discharged within 1 hour, and 2C means that the battery can complete the discharge process within half an hour.

[0079] In some embodiments, the negative pole piece 93 includes a tab 12 connected to the pole piece body 11, and the negative active layer includes a first groove 13, and the tab 12 is located in the first groove 13 and electrically connected to the negative current collector.

[0080] The number of punching parts 21 is at least one, and multiple punching parts 21 adjacent to the same circular arc area 102 form a punching area 301, and the width of the punching area 301 along the first direction is W1, which satisfies: 0 < W1 ≤ 2d, wherein d is the distance between the center position of the circular arc area 102 close to the tab 12 along the first direction and the first groove 13.

[0081] The pole piece 1 includes a pole piece body 11 and a tab 12, and the tab 12 can be integrally formed with the pole piece body 11 or formed by welding.

[0082] Optionally, in the embodiment, the pole piece body 11 is provided with a punching part 21 at a position corresponding to the circular arc area 102 and adjacent to the tab 12 in the first direction.

[0083] Generally, the current density near the tab 12 position is large, the ion transmission amount is more, the circular arc area 102 adjacent to the tab 12 in the first direction has poor infiltration effect under high compaction, which leads to more serious lithium precipitation in the circular arc area.

[0084] The winding battery provided by the embodiment of the utility model, the pole piece body 11 is provided with a punching part 21 at a position corresponding to the circular arc area 102 and adjacent to the tab 12 in the first direction, so that after the winding of the pole piece body 11 is completed, the punching part 21 is in the circular arc area 102, and the punching part 21 is more adjacent to the tab 12 at the position, electrolyte can be quickly penetrated, lithium ions can be quickly transmitted, the demand of the current density near the tab 12 position is met, the problem of lithium precipitation in the circular arc area is greatly improved, and then the battery deformation caused by lithium precipitation is improved, and the battery cycle expansion is reduced.

[0085] The pole piece body 11 is provided with a punching part 21 at a position corresponding to the circular arc area 102 and adjacent to the tab 12 in the first direction, additionally, the pole piece body 11 can also be provided with a punching part 21 at a position corresponding to all the circular arc areas 102, and is not limited to the position adjacent to the tab 12 in the first direction, so that the liquid passing capacity of the entire pole piece body 11 in the circular arc area 102 after winding is completed is improved.

[0086] Since the pole piece body 11 generally includes a current collector and an active material layer located on at least one side of the current collector, in order to facilitate welding of the tab 12 on the pole piece body 11, the mounting position of the pole piece body 11 corresponding to the tab 12 needs to be cleaned to expose the copper foil, so as to facilitate welding of the tab 12, and the cleaning area is the first groove 13.

[0087] In combination Figure 3 As shown, the area formed by the plurality of punching parts 21 adjacent to the same circular arc area 102 is the punching area 301, and it needs to be noted that the punching area 301 is not any position in the area forming the punching part 21, but means that a plurality of punching parts 21 exist densely in the area, and the area is called the punching area 301 for the convenience of describing the area. The punching area 301 can be specifically the edge line of the punching part 21 on the two side edges in the first direction, and the connecting line of the edge lines of the two side edges of the plurality of punching parts 21 adjacent to the same circular arc area 102 in the second direction.

[0088] By limiting the lower limit of the width W1 of the punching area 301 in the first direction, the circular arc area 102 can be ensured to form the punching part 21, so as to facilitate faster penetration of electrolyte.

[0089] By limiting the upper limit of the width W1 of the punching region 301 along the first direction, the punching region 301 can be prevented from occupying the position of the first groove 13.

[0090] In some embodiments, in combination with Figure 9 As shown, the width of the circular arc region 102 corresponding to the punching region 301 along the first direction in the unfolded state of the pole piece body 11 is F, and W1≥F is satisfied.

[0091] By making the width W1 of the punching region 301 along the first direction greater than the width F of the circular arc region 102 corresponding to the punching region 301 along the first direction, the punching region 301 can completely cover the circular arc region 102 along the first direction, or even extend beyond the circular arc region 102 along the first direction, so that the punching region 301 is closer to the tab 12, the area of the electrolyte rapid infiltration region is increased, lithium ions are transmitted faster, the demand for current density near the tab 12 is met, the problem of lithium precipitation in the circular arc region is greatly improved, and the battery deformation caused by lithium precipitation is improved, and the battery cycle expansion is reduced.

[0092] In some embodiments, in combination with Figure 9 As shown, in the unfolded state of the pole piece body 11, the projection of the punching region 301 on the pole piece body 11 at least partially overlaps the circular arc region 102, and at least partially overlaps at least part of the flat region 101 located on both sides of the circular arc region 102 along the first direction;

[0093] In combination with Figure 3 As shown, in the unfolded state of the pole piece body 11, the width of the pole piece body 11 along the second direction is W, wherein the second direction is perpendicular to the first direction;

[0094] The width of the part of the projection of the punching region 301 on the pole piece body 11 overlapping the flat region 101 along the first direction is G, and 500 μm≤G≤W / 2 is satisfied.

[0095] By limiting the lower limit of G, the punching region 301 can completely cover the circular arc region 102 along the first direction, and partially overlap the flat region 101, so that the punching region 301 is closer to the tab 12, the area of the electrolyte rapid infiltration region is increased, lithium ions are transmitted faster, the demand for current density near the tab 12 is met, the problem of lithium precipitation in the circular arc region is greatly improved, and the battery deformation caused by lithium precipitation is improved, and the battery cycle expansion is reduced.

[0096] The width W of the pole piece body 11 along the second direction satisfies 40 mm≤W≤150 mm.

[0097] Exemplarily, the value of W can be 40 mm or 50 mm or 70 mm or 85 mm or 90 mm or 100 mm or 120 mm or 140 mm or 150 mm, etc., or an interval range formed by any two of the above values.

[0098] In some embodiments, in combination with Figure 9 As shown, the distance between the punching area 301 and the edge of the pole piece body 11 in the second direction in the unfolded state is J, which satisfies: 0.5 mm≤J≤5 mm.

[0099] By providing the distance J between the punching area 301 and the edge of the pole piece body 11 in the second direction, it can be ensured that the edge of the pole piece body 11 in the second direction is in a flush state, avoiding burrs on the edge.

[0100] Exemplarily, the value of J can be 0.5 mm or 0.8 mm or 1 mm or 1.2 mm or 1.5 mm or 2 mm or 2.5 mm or 3 mm or 4 mm or 5 mm, etc., or an interval range formed by any two of the above values.

[0101] In some embodiments, in combination with Figure 3 As shown, the number of punching portions 21 is multiple, and the center distance between adjacent two punching portions 21 is D1, which satisfies: 100 μm≤D1≤2000 μm.

[0102] Preferably, in the present embodiment, the center distance D1 between adjacent two punching portions 21 can also satisfy: 200 μm≤D1≤1000 μm.

[0103] Exemplarily, the value of D1 can be 100 μm or 200 μm or 300 μm or 400 μm or 800 μm or 1000 μm or 1200 μm or 1500 μm or 1800 μm or 2000 μm, etc., or an interval range formed by any two of the above values.

[0104] In some embodiments, in combination with Figure 3 As shown, the aperture of the punching portion 21 is D4, which satisfies: 30 μm≤D4≤200 μm.

[0105] Preferably, in the present embodiment, the aperture D4 of the punching portion 21 can also satisfy: 50 μm≤D4≤100 μm.

[0106] Exemplarily, the value of D4 can be 30 μm or 40 μm or 50 μm or 67 μm or 82 μm or 100 μm or 120 μm or 131 μm or 140 μm or 150 μm or 180 μm or 200 μm, etc., or an interval range formed by any two of the above values.

[0107] In some embodiments, the punching part 21 comprises a through hole and / or a non-through hole, wherein the depth of the through hole is the same as the thickness of the pole piece body 11, and the depth of the non-through hole is less than the thickness of the pole piece body 11.

[0108] In this embodiment, the punching part 21 preferably adopts a through hole to ensure that the electrolyte can directly pass through the punching part 21 to pass through both sides of the pole piece body 11 along the thickness direction, thereby facilitating faster penetration of the electrolyte and faster transmission of lithium ions.

[0109] As a variation, the punching part 21 can also adopt a non-through hole, when it adopts a non-through hole, the electrolyte can be stored in the non-through hole, and when the liquid storage amount is not increased, the electrolyte is stored more in the non-through hole, avoiding poor electrolyte infiltration.

[0110] As a further variation, a through hole and a non-through hole can be combined on the same pole piece body 11.

[0111] In some embodiments, in combination with Figure 6 As shown, the number of punching parts 21 is at least one, and the plurality of punching parts 21 adjacent to the same circular arc region 102 form a punching region 301;

[0112] The number of wire slot parts 22 is at least one, and the plurality of wire slot parts 22 adjacent to each other form a wire slot region 302;

[0113] In the unfolded state of the pole piece body 11, the wire slot region 302 and the punching region 301 are arranged in the first direction.

[0114] The minimum distance between the wire slot part 22 and the adjacent punching part 21 in the first direction is D3, which satisfies: 200 μm < D3 ≤ 1000 μm.

[0115] For example, the value of D3 can be 100 μm or 200 μm or 300 μm or 400 μm or 800 μm or 1000 μm, etc., or an interval range formed by any two of the above values.

[0116] In this embodiment, in the unfolded state of the pole piece body 11, the wire slot region 302 and the punching region 301 are arranged in the first direction, that is, the wire slot region 302 and the punching region 301 do not overlap.

[0117] In addition, the width of the non-punching region 204 is W2, and when the non-punching region 204 is arranged in complete correspondence with the wire slot region 302, that is, the width of the wire slot region 302 is W2.

[0118] In combination with Figure 7 , Figure 8As shown, the extension direction of the wire slot portion 22 is parallel to the first direction, or the extension direction of the wire slot portion 22 is perpendicular to the first direction, or the extension direction of the wire slot portion 22 is at an angle to the first direction, or the wire slot portion 22 can also be arranged in a horizontal and vertical intersecting manner.

[0119] In some embodiments, the wire slot portion 22 is arranged in a horizontal and vertical intersecting manner. Figure 3 As shown, the number of wire slot portions 22 is at least one, and a plurality of wire slot portions 22 close to each other together form a wire slot area 302; the wire slot area 302 covers the entire surface of the negative active layer.

[0120] By covering the entire surface of the pole piece body 11 with the wire slot area 302, the electrolyte storage capacity of the wire slot portion 22 is maximized, and more electrolyte is stored in the wire slot portion 22 without increasing the liquid retention amount, avoiding poor electrolyte infiltration.

[0121] In some embodiments, the wire slot portion 22 is arranged in a horizontal and vertical intersecting manner. Figure 4 、 Figure 5 As shown, the extension direction of the wire slot portion 22 is parallel to the first direction, or the extension direction of the wire slot portion 22 is perpendicular to the first direction, or the extension direction of the wire slot portion 22 is at an angle to the first direction, or the wire slot portion 22 can also be arranged in a horizontal and vertical intersecting manner.

[0122] In some embodiments, the number of wire slot portions 22 is at least one, and a plurality of wire slot portions 22 close to each other together form a wire slot area 302.

[0123] At least one punched portion 21 is located in the wire slot area 302.

[0124] Further, the projection of the punched portion 21 on the pole piece body 11 is located in the wire slot portion 22, and / or the projection of the punched portion 21 on the pole piece body 11 is located between adjacent wire slot portions 22.

[0125] By locating at least one punched portion 21 in the wire slot area 302, the wire slot area 302 and the punched area 301 overlap, in the overlapping area, not only can more electrolyte be stored in the wire slot portion 22 to avoid poor electrolyte infiltration, but also can pass through both sides of the pole piece body 11, making lithium ions transmit faster and electrolyte penetrate faster, thereby improving or solving the lithium precipitation problem in the good arc area 102.

[0126] In some embodiments, the wire slot portion 22 is arranged in a horizontal and vertical intersecting manner. Figure 3 As shown, the number of wire slot portions 22 is a plurality, and the spacing between adjacent wire slot portions 22 perpendicular to the extension direction of the wire slot portion 22 is D2, satisfying: 500μm≤D2≤3000μm.

[0127] Preferably, in the embodiment, the interval D2 between the adjacent linear groove portions 22 can also satisfy 500 μm≤D2≤1500 μm.

[0128] For example, the value of D2 can be 500 μm, or 600 μm, or 700 μm, or 750 μm, or 800 μm, or 1000 μm, or 1200 μm, or 1500 μm, or 1800 μm, or 2000 μm, or 2200 μm, or 2400 μm, or 2800 μm, or 3000 μm, etc., or an interval range formed by any two of the above values.

[0129] In some embodiments, the pole piece body 11 includes a current collector, and an active material layer located on at least one side of the current collector.

[0130] In the thickness direction perpendicular to the pole piece body 11, the ratio between the depth of the linear groove portion 22 and the thickness of the active material layer on the side of the linear groove portion 22 is in the range of 0.1 to 0.5.

[0131] For example, the ratio between the depth of the linear groove portion 22 and the thickness of the active material layer on the side of the linear groove portion 22 can be 0.1, or 0.2, or 0.3, or 0.4, or 0.5, etc., or an interval range formed by any two of the above values.

[0132] By limiting the ratio between the depth of the linear groove portion 22 and the thickness of the active material layer on the side of the linear groove portion 22, the depth of the linear groove portion 22 can be ensured to be more accurate, while meeting the liquid storage requirement of the linear groove portion 22, avoiding damaging the integrity of the active material layer, and further avoiding the linear groove portion 22 from penetrating to the current collector.

[0133] In some embodiments, in the thickness direction perpendicular to the pole piece body 11, the depth of the linear groove portion 22 is in the range of 5 μm to 30 μm.

[0134] Preferably, in the embodiment, the depth of the linear groove portion 22 can also satisfy 10 μm to 20 μm.

[0135] For example, the depth of the linear groove portion 22 can be 5 μm, or 6 μm, or 7 μm, or 7.5 μm, or 8 μm, or 10 μm, or 12 μm, or 15 μm, or 18 μm, or 20 μm, or 22 μm, or 24 μm, or 28 μm, or 30 μm, etc., or an interval range formed by any two of the above values.

[0136] In some embodiments, the pole piece 1 comprises a negative pole piece, the negative pole piece comprises a negative active material, the negative active material comprises a silicon-based material, and the silicon content in the negative active material is 5% to 50%. Within this preferred range, the combination of the two methods of opening the linear groove part 22 and the punched hole part 21 on the pole piece body 11 can make the electrolyte store more in the linear groove part 22, avoid the poor electrolyte infiltration, and at the same time, make the pole piece body 11 penetrate through both sides, so that the lithium ions are transmitted faster and the electrolyte is penetrated faster, thereby improving or solving the lithium precipitation problem in the circular arc area 102, thereby ensuring the stability of the whole battery and relieving the battery deformation.

[0137] Of course, the silicon content of the negative pole piece can also be in the range of 0% to 100% in a broader sense, and only the parameters of the linear groove part 22 and the punched hole part 21 need to be adaptively adjusted. Although there may still be a lithium precipitation problem in the circular arc area 102, the opening of the linear groove part 22 and the punched hole part 21 can improve the infiltration and penetration of the electrolyte and play a role in relieving the battery deformation.

[0138] In some embodiments, the positive pole piece 92 and the negative pole piece 93 are both provided with punched hole parts 21 at positions corresponding to the circular arc area 102.

[0139] The punched hole part 21 of the positive pole piece 92 and the punched hole part 21 of the negative pole piece 93 coincide and / or are staggered.

[0140] Preferably, in the present embodiment, the negative pole piece is provided with a punched hole part 21 at a position corresponding to the circular arc area 102.

[0141] By providing the positive pole piece and the negative pole piece with punched hole parts 21 at positions corresponding to the circular arc area 102, the penetration rate of the electrolyte can be further improved, and by making the punched hole part 21 of the positive pole piece coincide with the punched hole part 21 of the negative pole piece, the electrolyte flow is smoother, the electrolyte flows back quickly, and even when the volume of the wound battery expands due to the complete lithiation of silicon, the space originally storing the electrolyte is further occupied, but the coinciding punched hole part 21 can still ensure smooth electrolyte flow, thereby preventing lithium precipitation in the circular arc area.

[0142] As a variation, the punched hole part 21 of the positive pole piece and the punched hole part 21 of the negative pole piece can also be staggered.

[0143] Optionally, the hole diameter of the punched hole part 21 of the negative pole piece can be greater than the hole diameter of the punched hole part 21 of the positive pole piece, or the hole diameter of the punched hole part 21 of the negative pole piece can be equal to the hole diameter of the punched hole part 21 of the positive pole piece, or the hole diameter of the punched hole part 21 of the negative pole piece can be less than the hole diameter of the punched hole part 21 of the positive pole piece.

[0144] In some embodiments, the ratio between the length of the wound battery along the first direction and the width of the wound battery along the second direction is 0.3-1.5 in the wound state.

[0145] In addition, the ratio between the width W1 of the punched area 301 along the first direction and the width of the wound battery along the second direction, i.e., the aspect ratio, can also be defined. When the aspect ratio is smaller, the area ratio of the punched area 301 is smaller, and the powder falling caused by the arc-shaped punching of the pole piece is less, thereby reducing the risk of short circuit of the battery.

[0146] In this embodiment, the pole piece 1 includes positive pole pieces and negative pole pieces. The preparation process of the positive pole pieces and the negative pole pieces and the preparation process of the wound battery are described below.

[0147] Positive electrode preparation: lithium cobaltate, conductive agent (mixture of conductive carbon black and carbon nanotube), and polyvinylidene fluoride (PVDF) were placed in N-methyl-2-pyrrolidone (NMP) at a mass ratio of 98.20:1:0.8, stirred uniformly, and a positive electrode slurry was prepared; the positive electrode slurry was uniformly coated on both sides of the aluminum foil, and then dried, rolled, and cut to obtain the positive electrode sheet.

[0148] Negative electrode preparation: artificial graphite (21% silicon-carbon mixed in graphite), conductive carbon black, butadiene rubber, and sodium carboxymethyl cellulose were placed in deionized water at a mass ratio of 96.1:0.4:1.4:2.1, stirred uniformly, and a negative electrode slurry was prepared; the negative electrode slurry was uniformly coated on the negative electrode current collector, and then dried, rolled, and cut to obtain the negative electrode sheet, which was then wire-bonded.

[0149] Battery preparation: the separator used in this application is a 7.5 μm thick base material + ceramic + rubber-coated separator. The electrolyte includes lithium salt LiPF6 and solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), and the molar ratio of the three is DEC:EC:EMC=1:1:1. The above cut and sheeted positive electrode sheet, negative electrode sheet, and separator were wound into a wound battery structure, and the battery was subjected to heat pressing, packaging, liquid injection, formation, and two-sealing processes to obtain a lithium ion wound battery.

[0150] The performances of the wound battery provided in this embodiment after the punched part 21 is set are tested, and a plurality of embodiments and comparative examples are described in combination with Table 1.

[0151] Table 1

[0152]

[0153]

[0154] Among them, 400T means 400 times of charge and discharge cycles.

[0155] The negative electrode sheet was used for the test in the present batch of tests.

[0156] In Comparative Example 1, only the negative electrode sheet was subjected to wire punching to form the wire groove portion 22.

[0157] In Comparative Example 2, the negative electrode sheet was not subjected to wire punching, that is, the negative electrode sheet was not provided with the wire groove portion 22, and only the punching portion 21 was provided in the arc region 102, the center distance D1 between the adjacent two punching portions was 0.5 mm, the width W1 of the punching region 301 in the first direction was 8 mm, and the remaining parameter features were the same as those of Comparative Example 1.

[0158] In Example 1, the negative electrode sheet was subjected to wire punching on the whole surface, that is, the wire groove region 302 covered the whole surface of the electrode body 11, and then the punching portion 21 was provided in the arc region 102 of the negative electrode sheet, the center distance D1 between the adjacent two punching portions was 1 mm, the width W1 of the punching region 301 in the first direction was 8 mm, and the remaining parameter features were the same as those of Comparative Example 1.

[0159] In Example 2, the negative electrode sheet was subjected to wire punching on the whole surface, that is, the wire groove region 302 covered the whole surface of the electrode body 11, and then the punching portion 21 was provided in the arc region 102 of the negative electrode sheet, the center distance D1 between the adjacent two punching portions was 0.5 mm, the width W1 of the punching region 301 in the first direction was 8 mm, and the remaining parameter features were the same as those of Comparative Example 1.

[0160] In Example 3, only the flat region 101 of the negative electrode sheet was subjected to wire punching, that is, the arc region 102 of the negative electrode sheet was not provided with the wire groove portion 22, and only the punching portion 21 was provided in the arc region 102, the center distance D1 between the adjacent two punching portions was 0.5 mm, the width W1 of the punching region 301 in the first direction was 8 mm, and the remaining parameter features were the same as those of Comparative Example 1.

[0161] The capacity, internal resistance, cycle capacity retention rate, swelling rate and edge lithium precipitation of the batteries obtained in Examples 1-3 and Comparative Examples 1 and 2 were compared, as shown in Table 1.

[0162] The batteries containing the above electrode sheets were tested, and the following results were obtained:

[0163] Comparative Example 2 was compared with Comparative Example 1, and the arc region lithium precipitation was not improved, the internal resistance was reduced, the swelling rate was reduced, but the cycle capacity retention rate was slightly reduced.

[0164] Example 1 was compared with Comparative Example 1, and the cycle lithium precipitation was improved to a certain extent, the internal resistance was reduced, the swelling rate was reduced, but the cycle capacity retention rate was slightly reduced.

[0165] Compared with the comparative example 1, the lithium precipitation is obviously improved, the internal resistance is reduced, the expansion rate is reduced, and the cycle capacity retention is improved.

[0166] Compared with the comparative example 1, the lithium precipitation is obviously improved, the internal resistance is reduced, the expansion rate is reduced, and the cycle capacity retention is improved.

[0167] It is shown that, after the punching part 21 is arranged at the position corresponding to the circular arc area 102 of the pole piece body 11, the winding battery provided by the embodiment can increase the electrolyte infiltration effect and penetration speed, increase the liquid storage capacity, and improve the lithium precipitation and the cycle capacity retention and cycle expansion of the battery.

[0168] In addition, after the punching part 21 is arranged at the position corresponding to the circular arc area 102 of the pole piece body 11, the pole piece body 11 has a pore structure, which can reduce the pore tortuosity of the electrode, can be used as a channel for the rapid diffusion of Li+ in the pole piece, is beneficial to the rapid diffusion of Li+ in the electrode, and reduces the impedance.

[0169] According to the embodiment of the utility model, on the other hand, a kind of lithium ion secondary battery is also provided, and it include: as above-mentioned winding battery.

[0170] Obviously, the above embodiment is only for clearly illustrating the example, and not the limitation of the embodiment. Although the embodiment of the utility model is described in conjunction with the drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the utility model, and such modifications and variations all fall within the scope defined by the utility model.

Claims

1. A wound battery, characterized by, The winding battery is formed by winding the positive electrode sheet (92), the separator (91) and the negative electrode sheet (93) in layers, the negative electrode sheet (93) comprising a flat area (101) and a circular arc area (102) located on both sides of the flat area (101) in a first direction; The negative electrode sheet (93) comprises a sheet body (11), the negative electrode sheet (93) comprising a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer being provided with a wire slot portion (22) at least at a position corresponding to the flat area (101); The sheet body (11) is provided with a punching portion (21) at a position corresponding to the circular arc area (102).

2. The wound battery of claim 1, wherein, The negative electrode sheet (93) comprises a tab (12) connected to the sheet body (11); The negative electrode active layer comprises a first groove (13), and the tab (12) is located in the first groove (13) and electrically connected to the negative electrode current collector; The number of the punching portions (21) is at least one, and a plurality of the punching portions (21) adjacent to the same circular arc area (102) form a punching area (301), the width of the punching area (301) in the first direction is W1, and 0 < W1 ≤ 2d is satisfied, wherein d is the distance between the center position of the circular arc area (102) close to the tab (12) in the first direction and the first groove (13).

3. The wound battery of claim 2, wherein, The width of the circular arc area (102) corresponding to the punching area (301) in the first direction is F, and W1 ≥ F is satisfied.

4. The wound battery of claim 3, wherein, The projection of the punching area (301) on the sheet body (11) at least partially overlaps the circular arc area (102) and at least partially overlaps at least part of the flat area (101) located on both sides of the circular arc area (102) in the first direction; The width of the sheet body (11) in a second direction is W, wherein the second direction is perpendicular to the first direction; The width of the part of the projection of the punching area (301) on the sheet body (11) overlapping the flat area (101) in the first direction is G, and 500 μm ≤ G ≤ W / 2 is satisfied.

5. The wound battery of claim 2, wherein, The distance between the edge of the sheet body (11) in the second direction and the punching area (301) is J, and 0.5 mm ≤ J ≤ 5 mm is satisfied.

6. The wound battery of claim 1, wherein, The center distance between two adjacent punching portions (21) is D1, and 100 μm ≤ D1 ≤ 2000 μm is satisfied; and / or the diameter of the punching portion (21) is D4, and 30 μm ≤ D4 ≤ 200 μm is satisfied.

7. The wound battery of claim 1, wherein, The punching portion (21) comprises a through hole and / or a non-through hole; wherein the depth of the through hole is the same as the thickness of the sheet body (11), and the depth of the non-through hole is less than the thickness of the sheet body (11).

8. The wound battery of claim 1, wherein, The number of the punching portions (21) is at least one, and a plurality of the punching portions (21) adjacent to the same circular arc area (102) form a punching area (301); The number of the wire slot portions (22) is at least one, and a plurality of the wire slot portions (22) adjacent to each other form a wire slot area (302); The line groove region (302) is spaced apart from the punching region (301) along the first direction; The minimum distance between the line groove portion (22) and the adjacent punching portion (21) along the first direction is D3, which satisfies: 200 μm < D3 ≤ 1000 μm.

9. The wound battery of claim 1, wherein, The number of the line groove portions (22) is at least one, and a plurality of the line groove portions (22) close to each other jointly form a line groove region (302); the line groove region (302) covers the entire surface of the negative active layer.

10. The wound battery of claim 1, wherein, The number of the line groove portions (22) is at least one, and a plurality of the line groove portions (22) close to each other jointly form a line groove region (302). At least one of the punching portions (21) is located in the line groove region (302).

11. The wound battery of any one of claims 8 to 10, wherein, The extension direction of the line groove portion (22) is parallel to the first direction, or the extension direction of the line groove portion (22) is perpendicular to the first direction, or the extension direction of the line groove portion (22) is arranged at an angle to the first direction.

12. The wound battery of any one of claims 8 to 10, wherein, The number of the line groove portions (22) is a plurality, and the distance between adjacent line groove portions (22) in the direction perpendicular to the extension direction of the line groove portion (22) is D2, which satisfies: 500 μm ≤ D2 ≤ 3000 μm.

13. The wound battery of any one of claims 1 to 10, wherein, In the direction perpendicular to the thickness direction of the pole piece body (11), the ratio between the depth of the line groove portion (22) and the thickness of the active material layer on one side of the line groove portion (22) is in the range of 0.1-0.

5.

14. The wound battery of any one of claims 1 to 10, wherein, In the direction perpendicular to the thickness direction of the pole piece body (11), the depth of the line groove portion (22) is in the range of 5 μm-30 μm.

15. The wound battery of any one of claims 1 to 10, wherein, The negative pole piece (93) comprises a negative active material, and the negative active material comprises a silicon-based material.

16. The wound battery of any one of claims 1 to 10, wherein, The positive pole piece (92) and the negative pole piece (93) are both provided with the punching portion (21) at the position corresponding to the circular arc region (102). The punching portion (21) of the positive pole piece and the punching portion (21) of the negative pole piece are coincident and / or staggered.

17. The wound battery of any one of claims 1 to 10, wherein, The ratio between the length of the winding battery along the first direction and the width along the second direction is 0.3-1.

5.

18. A lithium-ion secondary battery, characterized by comprising: The winding battery comprises the winding battery of any one of claims 1-17.

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