Pole piece structure, winding battery cell and battery

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a pole piece structure, a winding battery cell and a battery. Wherein the pole piece structure comprises a pole piece head part, a pole piece middle end part and a pole piece tail part which are connected in sequence; when the pole piece structure is in a winding state, the projection of the pole piece tail towards the pole piece head covers the pole piece head; and the winding starting end of the pole piece head part and the winding ending end of the pole piece tail part are arranged in a staggered manner in the thickness direction. According to the utility model, the cutting positions of the wound pole piece structure are not overlapped, so that purple spot lithium precipitation caused by overlapping of the cutting positions can be relieved; and the use safety and stability are improved.

Description

Technical Field

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

[0002] Lithium-ion batteries have the important advantages of high voltage and high capacity, long cycle life and good safety performance, which makes them have broad application prospects in portable electronic devices (including mobile phone batteries, etc.), electric vehicles, space technology, defense industry and other fields, and have become a research hotspot that has attracted widespread attention in recent years. At present, lithium-ion batteries mainly adopt two structures: winding and stacking. Among them, the stacking structure has complex process, low efficiency and relatively more safety hazards, while the winding structure has simple process, high production efficiency, good safety and consistency.

[0003] However, some of the existing wound battery cells are cut to the end, and there will be overlap in the cutting positions when the odd folds are made, resulting in a significant thickness difference inside and outside the overlapping area. In addition, during formation, the thinner area is subjected to less force, resulting in a large thickness difference, which will cause purple spots and lithium precipitation, resulting in low stability and safety in use. Utility Model Content

[0004] The purpose of the utility model is to provide a pole piece structure to address the deficiencies of the prior art, which can solve the technical problem that the wound battery cell will overlap when an odd number of folds are performed, resulting in a large thickness difference and purple spot lithium precipitation.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A pole piece structure comprises a pole piece head, a pole piece middle end and a pole piece tail connected in sequence; when the pole piece structure is in a wound state, the projection of the pole piece tail toward the pole piece head covers the pole piece head; and the winding starting end of the pole piece head is staggered with the winding ending end of the pole piece tail in the thickness direction.

[0007] Preferably: a dislocation segment is provided on a side of the pole piece tail away from the pole piece middle end; the dislocation segment is dislocated with the pole piece head in the thickness direction.

[0008] Preferably, the length L of the offset section satisfies: 3mm<L<5mm.

[0009] Preferably: the end portion of the pole piece includes at least two corner bend sections and at least one straight section; the corner bend sections and the straight sections are arranged in a staggered manner in sequence; and one of the corner bend sections is connected to one end of the pole piece head; and the other corner bend section is connected to one end of the pole piece tail.

[0010] Preferably: on the same vertical plane in the thickness direction of the pole piece structure, the relationship between the thickness C of the corner bend section close to the pole piece head side and the thickness D of the corner bend section away from the pole piece head side satisfies: C<D.

[0011] The utility model also discloses a wound battery cell, comprising a first pole piece and a second pole piece with opposite polarities and an isolation membrane arranged between the first pole piece and the second pole piece; and the first pole piece, the isolation membrane and the second pole piece are arranged in a stacked and wound manner in sequence; the first pole piece and / or the second pole piece is the above-mentioned pole piece structure.

[0012] Preferably: the first pole piece is a positive pole piece; the second pole piece is a negative pole piece; both side ends of the positive pole piece are provided with a positive pole tail and a positive pole head; both side ends of the negative pole piece are provided with a negative pole head and a negative pole tail;

[0013] The difference between the length of the negative electrode head and the length of the positive electrode head is M1, and M1 satisfies: 8mm<M1<13mm.

[0014] Preferably, the difference between the length of the negative electrode tail and the length of the positive electrode tail is M2, and M2 satisfies: 12 mm<M1<30 mm.

[0015] Preferably: the difference between the length of the negative electrode head and the length of the positive electrode head is M1; the difference between the length of the negative electrode tail and the length of the positive electrode tail is M2;

[0016] Among them, the relationship between M1 and M2 satisfies: M1<M2.

[0017] The utility model also discloses a battery, comprising the above-mentioned wound battery core.

[0018] The beneficial effect of the utility model lies in that the technical scheme adopts a length of the pole piece tail that is greater than the length of the pole piece head, and the winding starting end of the pole piece head does not overlap with the winding ending end of the pole piece tail, thereby promoting the formation of a clear staggered setting between the pole piece tail and the pole piece head, thereby ensuring that the cutting positions of the pole piece structure after winding do not overlap, and the thickness difference is reduced during formation hot pressing. At the same time, the pressures on both sides of the winding core are similar, and the difference in the amount of electrolyte retained is as small as possible. Therefore, purple spot lithium precipitation caused by overlapping cutting positions can be alleviated, and the safety and stability of use can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following will refer to the attached Figures 1 to 4 To describe the features, advantages and technical effects of exemplary embodiments of the present utility model.

[0020] Figure 1 This is a schematic structural diagram of a pole piece structure of an embodiment of the utility model;

[0021] Figure 2 This is a schematic structural diagram of a pole piece structure of an embodiment of the utility model;

[0022] Figure 3 This is a schematic diagram of the structure of a wound battery cell according to an embodiment of the utility model;

[0023] Figure 4 The figure is a schematic structural diagram of a wound battery cell according to an embodiment of the present invention.

[0024] In the figure: 1-pole piece head; 11-winding starting end; 2-pole piece tail; 21-winding ending end; 3-pole piece middle end; 31-corner bending section; 32-straight section; 4-offset section; 100-first pole piece; 110-positive pole piece; 101-positive pole tail; 102-positive pole head; 200-second pole piece; 210-negative pole piece; 201-negative pole head; 202-negative pole tail; 300-isolating film; AB direction - thickness direction; thickness C; thickness D. DETAILED DESCRIPTION

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0026] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and multiple situations exist alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0029] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0030] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0031] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0032] The following is combined with Figure 1 to Figure 4 The utility model is further described in detail, but it is not intended to limit the utility model.

[0033] like Figure 1 As shown, in one embodiment of the utility model, the pole piece structure comprises a pole piece head 1, a pole piece middle end 3 and a pole piece tail 2 connected in sequence; when the pole piece structure is in a wound state, the projection of the pole piece tail 2 toward the pole piece head 1 covers the pole piece head 1; and the winding start end 11 of the pole piece head 1 is staggered with the winding end end 21 of the pole piece tail 2 in the thickness direction (i.e., non-overlapping). Figure 1 As shown, the thickness direction is the AB direction; the winding starting end of the pole piece head 1 is the side end of the pole piece head 1 away from the pole piece middle end 3; the winding ending end of the pole piece tail 2 is the side end of the pole piece tail 2 away from the pole piece middle end 3.

[0034] The technical solution of the utility model adopts a method in which the length of the pole piece tail 2 is greater than the length of the pole piece head 1, and the winding starting end of the pole piece head 1 does not overlap with the winding ending end of the pole piece tail 2, thereby promoting the formation of a significant offset setting between the pole piece tail 2 and the pole piece head 1, thereby ensuring that the cutting positions of the pole piece structure after winding do not overlap, and the thickness difference is reduced during formation hot pressing. At the same time, the pressures on both sides of the winding core are similar, and the difference in the amount of electrolyte retained is as small as possible. Therefore, purple spot lithium precipitation (purple spot lithium precipitation refers to the phenomenon of slight lithium precipitation) caused by overlapping cutting positions can be alleviated, thereby improving the safety and stability of use.

[0035] Specifically, in some embodiments, Figure 1 As shown, a dislocation section 4 is provided on the side of the pole piece tail 2 away from the pole piece middle end 3; the dislocation section 4 is dislocated with the pole piece head 1 in the thickness direction. Figure 1 and 2 As shown, the length L of the dislocation segment 4 satisfies: 3mm<L<5mm. That is to say, the pole piece head 1 of the pole piece structure is shortened and the pole piece tail 2 is lengthened to form a dislocation in the thickness direction, so that the thickness difference can be reduced during hot pressing. At the same time, the pressure on both sides of the winding core is similar, and the difference in the amount of electrolyte is as small as possible. Therefore, the purple spot lithium precipitation caused by the overlapping of the cutting position can be alleviated, and the safety and stability of use can be improved. Furthermore, when L≥5mm, the cutting position difference is too large, which will shorten the pole piece structure, thereby reducing the capacity provided by the pole piece structure; when L≤3mm, the cutting position difference is too close to the inner thickness of the cutting position, the pressure is large, and the electrolyte is squeezed out more, which leads to purple spot lithium precipitation.

[0036] Specifically, in some embodiments, Figure 1 As shown, the end portion 3 of the pole piece includes at least two corner bend sections 31 and at least one straight section 32; the corner bend sections 31 and the straight sections 32 are arranged in a staggered manner; and one corner bend section 31 is connected to one end of the pole piece head 1; and the other corner bend section 31 is connected to one end of the pole piece tail 2. Figure 2 As shown, on the same vertical plane in the thickness direction (AB direction) of the pole piece structure, the relationship between the thickness C of the corner bending section 31 close to the pole piece head 1 and the thickness D of the corner bending section 32 away from the pole piece head 1 satisfies: C<D. In other words, the outer R corner gap of the pole piece structure is larger than the inner side, so that the length of the pole piece tail 2 is lengthened, thereby improving the formation hot-pressing balance and reducing the range of the area with obvious thickness difference, which can effectively improve the purple spot lithium precipitation.

[0037] That is to say, when the electrode structure is wound, the length difference L of the electrode head 1 and the electrode tail 2 needs to reach the following range: 3mm<L<5mm, and the winding length tolerance of the electrode structure is 0.5~1mm, and the coating tolerance is 0~1mm, so that the thickness difference can be reduced during the formation hot pressing. At the same time, the pressure on both sides of the winding core is similar, and the difference in the electrolyte retention is as small as possible. Therefore, the purple spot lithium precipitation caused by the overlapping of the cutting position can be alleviated, and the safety and stability of use can be improved.

[0038] The utility model also provides a wound battery core, such as Figure 3 As shown, the wound cell includes a first pole piece 100 and a second pole piece 200 with opposite polarities and a separator 300 disposed between the first pole piece 100 and the second pole piece 200; and the first pole piece 100, the separator 300 and the second pole piece 200 are sequentially stacked and wound; the first pole piece 100 and / or the second pole piece 200 are a pole piece structure. The specific structure of the pole piece structure refers to the above embodiment. Since the wound cell adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0039] Specifically, in some embodiments, Figure 3 and 4 As shown, the first electrode sheet 100 is the positive electrode sheet 110; the second electrode sheet 200 is the negative electrode sheet 210; that is, during the winding process, since the positive electrode sheet 110 is in the outermost layer when the winding is completed; therefore, it is only necessary to control the length difference L of the head cut and the tail cut of the positive electrode sheet 110 (cathode sheet) to reach the following range: 3mm<L<5mm, so as to ensure that the thickness difference is reduced during the formation hot pressing, and at the same time, the pressure on both sides of the winding core is similar, and the difference in the electrolyte retention is as small as possible, so that the purple spot lithium precipitation caused by the overlapping of the cuts can be alleviated, and the safety and stability of use can be improved.

[0040] Specifically, in some embodiments, Figure 4As shown, the positive electrode tail 101 and the positive electrode head 102 are provided at both sides of the positive electrode sheet 110; the negative electrode head 201 and the negative electrode tail 202 are provided at both sides of the negative electrode sheet 210. Among them, the difference between the length of the negative electrode head 201 along the length direction of the wound battery cell and the length of the positive electrode head 102 along the length direction of the wound battery cell is M1, and M1 satisfies: 8mm<M1<13mm. Among them, the difference between the length of the negative electrode tail 202 along the length direction of the wound battery cell and the length of the positive electrode tail 101 along the length direction of the wound battery cell is M2, and M2 satisfies: 12mm<M1<30mm. This structure can effectively ensure the uniformity of the overall thickness of the wound battery cell through the relatively long dimensions of the two side ends of the negative electrode sheet 210, reduce the thickness difference, thereby ensuring the charge and discharge rate, and effectively reducing the occurrence of purple spot lithium precipitation (purple spot lithium precipitation refers to the phenomenon of slight lithium precipitation). Further, the relationship between M1 and M2 satisfies: M1<M2. The relatively long tail end of the negative electrode sheet 210 can make up for the flatness of the outer surface as much as possible, and the shorter but thicker starting end can make up for the internal blank area as much as possible.

[0041] The positive electrode sheet 110 includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector; the positive electrode current collector includes a positive electrode coating area and a positive electrode tab connected to the positive electrode coating area, the positive electrode coating area is coated with the positive electrode active material layer, and the positive electrode tab is not coated with the positive electrode active material layer. Furthermore, the material of the positive electrode current collector can be aluminum, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc.

[0042] The negative electrode sheet 210 includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode current collector; the negative electrode current collector includes a negative electrode coating area and a negative electrode tab connected to the negative electrode coating area, the negative electrode coating area is coated with the negative electrode active material layer, and the negative electrode tab is not coated with the negative electrode active material layer. Further, the material of the negative electrode current collector can be copper, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc.

[0043] The material of the isolation film 300 may be PP (polypropylene) or PE (polyethyl ene) or the like.

[0044] The utility model also proposes a battery, which includes a wound battery cell. The specific structure of the wound battery cell refers to the above embodiment. Since the battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0045] Among them, battery refers to a cup, trough or other container or part of a composite container that contains electrolyte solution and metal electrodes to generate current, and is a device that can convert chemical energy into electrical energy; the battery has positive and negative electrodes. With the advancement of science and technology, batteries generally refer to small devices that can generate electrical energy, such as solar cells. The performance parameters of batteries mainly include electromotive force, capacity, specific energy and resistance. Battery principle: In chemical batteries, the direct conversion of chemical energy into electrical energy is the result of spontaneous oxidation, reduction and other chemical reactions inside the battery, which are carried out on the two electrodes respectively. The negative electrode active material is composed of a reducing agent with a relatively negative potential and stable in the electrolyte, such as active metals such as zinc, cadmium, and lead, and hydrogen or hydrocarbons. The positive electrode active material is composed of an oxidizing agent with a relatively positive potential and stable in the electrolyte, such as metal oxides such as manganese dioxide, lead dioxide, and nickel oxide, oxygen or air, halogens and their salts, oxygen-containing acids and their salts, etc. The electrolyte is a material with good ionic conductivity, such as an aqueous solution of acid, alkali, or salt, an organic or inorganic non-aqueous solution, a molten salt, or a solid electrolyte.

[0046] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0047] According to the disclosure and teaching of the above description, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the above specific implementation, and any obvious improvement, replacement or modification made by the technicians in this field on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in this specification, these terms are only for the convenience of explanation and do not constitute any limitation to the utility model.

Claims

1. A pole piece structure, characterized in that: It includes a pole piece head, a pole piece middle end and a pole piece tail which are connected in sequence; when the pole piece structure is in a wound state, the projection of the pole piece tail toward the pole piece head covers the pole piece head; and the winding starting end of the pole piece head is offset with the winding ending end of the pole piece tail in the thickness direction.

2. The pole piece structure according to claim 1, characterized in that: A dislocation section is provided on one side of the pole piece tail away from the pole piece middle end; the dislocation section is dislocated with the pole piece head in the thickness direction.

3. The pole piece structure according to claim 2, characterized in that: The length L of the offset section satisfies: 3mm<L<5mm.

4. The pole piece structure according to any one of claims 1 to 3, characterized in that: The end portion of the pole piece includes at least two corner bend sections and at least one straight section; the corner bend sections and the straight sections are arranged in a staggered manner; and one of the corner bend sections is connected to one end of the pole piece head; and the other corner bend section is connected to one end of the pole piece tail.

5. The pole piece structure according to claim 4, characterized in that: On the same vertical plane in the thickness direction of the pole piece structure, the relationship between the thickness C of the corner bend section close to the pole piece head side and the thickness D of the corner bend section away from the pole piece head side satisfies: C<D.

6. A wound battery cell, characterized in that: It includes a first pole piece and a second pole piece with opposite polarities and an isolation membrane arranged between the first pole piece and the second pole piece; and the first pole piece, the isolation membrane and the second pole piece are arranged in a stacked and wound manner in sequence; the first pole piece and / or the second pole piece is the pole piece structure as described in any one of claims 1 to 5 above.

7. The wound battery cell according to claim 6, characterized in that: The first electrode sheet is a positive electrode sheet; the second electrode sheet is a negative electrode sheet; the two side ends of the positive electrode sheet are provided with a positive electrode tail and a positive electrode head; the two side ends of the negative electrode sheet are provided with a negative electrode head and a negative electrode tail; The difference between the length of the negative electrode head and the length of the positive electrode head is M1, and M1 satisfies: 8mm<M1<13mm.

8. The wound battery cell according to claim 7, characterized in that: The difference between the length of the negative electrode tail and the length of the positive electrode tail is M2, and M2 satisfies: 12mm<M1<30mm.

9. The wound battery cell according to claim 8, characterized in that: The difference between the length of the negative electrode head and the length of the positive electrode head is M1; the difference between the length of the negative electrode tail and the length of the positive electrode tail is M2; Among them, the relationship between M1 and M2 satisfies: M1<M2.

10. A battery, characterized in that: The invention comprises the wound battery cell as claimed in any one of claims 6 to 9.

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