Battery cell, battery and electric device

Abstract

The utility model discloses a battery cell. The battery cell comprises a pole piece and a diaphragm, comprising a pole piece and a diaphragm, the diaphragm and the pole piece are stacked, the pole piece and the diaphragm are wound along the same direction and respectively comprise a corner area formed during winding, and an electrolyte expansion layer is arranged on the surface of at least one side of the corner area of the diaphragm, is supported between the corner area of the diaphragm and the corner area of the pole piece and is used for supporting a gap for electrolyte to flow. According to the technical scheme, the electrolyte expansion layer is arranged in the corner area of the diaphragm, so that the lithium precipitation phenomenon in the corner area of the battery cell can be effectively improved. The electrolyte expansion layer expands after being infiltrated by the electrolyte and can be supported between the diaphragm and the corner area of the pole piece, so that a gap for the electrolyte to flow is formed between the diaphragm and the corner area of the pole piece, and the gap can be used for buffering the volume change of the pole piece and can also prevent the electrolyte from being extruded out, thereby avoiding lithium precipitation at the corner of the battery cell and prolonging the service life of the battery cell. The cycle stability and the service life of the battery cell are improved. In addition, the utility model also discloses a battery and an electric device.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery cell, a battery and an electrical device. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices, energy storage, electric vehicles and other fields due to their advantages such as high energy density, high voltage, low self-discharge and light weight.

[0003] The structure of lithium-ion batteries mainly includes components such as positive electrode sheets, negative electrode sheets, separators and electrolytes. According to the different battery shells, lithium-ion batteries can be divided into square, cylindrical and soft-pack types. At present, square soft-pack lithium-ion batteries are mostly manufactured by winding, that is, the positive and negative electrode sheets and separators are stacked and wound, and then placed in a shell made of soft-pack materials, and finally the electrolyte is injected and sealed.

[0004] However, due to the existence of corner areas in such wound lithium-ion batteries, long-term charging and discharging of lithium-ion batteries will consume electrolyte, and the pole pieces will expand and squeeze the corners, squeezing the electrolyte out of the corner areas, resulting in a reduction in electrolyte in the corner areas. The reduction in electrolyte in the corner areas is very likely to cause lithium precipitation, which affects the life of the lithium-ion battery. Utility Model Content

[0005] The main purpose of the utility model is to provide a battery cell, aiming to solve the problem that lithium deposition is easy to occur in the corner area of ​​the wound battery cell.

[0006] In order to achieve the above object, the utility model provides a battery cell, which comprises:

[0007] It includes a pole piece and a diaphragm, the diaphragm and the pole piece are stacked, the pole piece and the diaphragm are wound in the same direction, the pole piece and the diaphragm both include a corner area formed during the winding, at least one side surface of the corner area of ​​the diaphragm is provided with an electrolyte expansion layer, the electrolyte expansion layer is supported between the diaphragm and the corner area of ​​the pole piece, and is used to support a gap for the electrolyte to flow.

[0008] In some embodiments, the electrode sheets include a positive electrode sheet and a negative electrode sheet stacked with the diaphragm, the positive electrode sheet, the negative electrode sheet and the diaphragm are wound several times in the same direction, the diaphragm includes several corner areas formed by winding several times, and the sides of the several corner areas are each provided with at least one electrolyte expansion layer.

[0009] In some embodiments, the electrolyte expansion layer is disposed on the side of each corner region, and a plurality of the electrolyte expansion layers are symmetrically distributed.

[0010] In some embodiments, the electrolyte expansion layer is disposed on the side of each corner region, and a plurality of the electrolyte expansion layers are staggeredly distributed.

[0011] In some embodiments, the lengths of the corner regions gradually increase as the number of turns of the separator is wound in the same direction, and a plurality of the electrolyte expansion layers are disposed on the side of at least one of the corner regions.

[0012] In some embodiments, a plurality of the electrolyte expansion layers are sequentially spaced apart along the length direction of the corner region.

[0013] In some embodiments, a plurality of the electrolyte expansion layers are sequentially spaced apart from each other along the width direction of the corner region.

[0014] In some embodiments, the electrolyte expansion layer is in a strip shape.

[0015] The utility model further provides a battery, comprising the above-mentioned battery cell.

[0016] The utility model further provides an electrical device, comprising the aforementioned battery.

[0017] In the technical solution of the utility model, by setting an electrolyte expansion layer in the corner area of ​​the diaphragm, the lithium deposition phenomenon in the corner area of ​​the battery cell can be effectively improved. The electrolyte expansion layer expands after being infiltrated by the electrolyte, and can be supported between the diaphragm and the corner area of ​​the pole piece, so that a gap for electrolyte flow is formed between the two. The gap can be used to buffer the volume change of the pole piece and prevent the electrolyte from being squeezed out, thereby avoiding lithium deposition in the corner of the battery cell, thereby increasing the cycle stability and service life of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the diaphragm in one embodiment of the utility model;

[0019] Figure 2 This is a schematic diagram of the structure of a battery cell in one embodiment of the utility model;

[0020] Figure 3 This is a schematic diagram of the structure of the diaphragm in one embodiment of the utility model;

[0021] Figure 4 This is a schematic diagram of the structure of a battery cell in one embodiment of the utility model;

[0022] Figure 5 This is a schematic diagram of the structure of a battery cell in another embodiment of the utility model;

[0023] Figure 6 This is a schematic diagram of the structure of a battery cell in yet another embodiment of the present utility model;

[0024] Figure 7This is a schematic diagram of the structure of the diaphragm in one embodiment of the utility model;

[0025] Figure 8 It is a schematic structural diagram of a battery cell in another embodiment of the utility model.

[0026] Description of Figure Numbers:

[0027] 100, diaphragm; 101, electrolyte expansion layer; 100a, corner area; 200, pole piece; 201, positive pole piece; 202, negative pole piece.

[0028] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the scheme in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0032] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0033] like Figure 1 and Figure 2 As shown, Figure 1This is a schematic diagram of the structure of the diaphragm in one embodiment of the utility model. Figure 2 It is a schematic diagram of the structure of a battery cell in one embodiment of the utility model.

[0034] In this embodiment, a pole piece 200 and a diaphragm 100 are included. The diaphragm 100 and the pole piece 200 are stacked and arranged. The pole piece 200 and the diaphragm 100 are wound in the same direction. The pole piece 200 and the diaphragm 100 both include a corner area formed during the winding. An electrolyte expansion layer 101 is provided on at least one side of the corner area 100a of the diaphragm. The electrolyte expansion layer 101 is supported between the corner area of ​​the diaphragm 100 and the pole piece 200, and is used to support a gap for the flow of electrolyte.

[0035] The battery cell in this embodiment is formed by winding the electrode sheet 200 and the separator 100 in the same direction, wherein the electrode sheet 200 includes a positive electrode sheet 201 and a negative electrode sheet 202, and the separator 100 is stacked with the positive electrode sheet 201 and the negative electrode sheet 202 and wound in the same direction.

[0036] It should be noted that the positive and negative electrode sheets are generally composed of a current collector, an active material layer, etc. Among them, the active material layer of the positive electrode sheet 201 is commonly made of lithium iron phosphate, lithium nickel cobalt manganate (NMC) and lithium nickel cobalt aluminate (NCA). These materials have the advantages of high voltage platform, good cycle stability and safety. The active material layer of the negative electrode sheet 202 can be made of graphite with stable chemical properties and good ion conductivity, or some composite materials to take into account high capacity and high stability.

[0037] In this embodiment, the separator 100 is used as a separator for carrying the electrolyte expansion layer 101 and separating the positive electrode sheet 201 and the negative electrode sheet 202 to prevent short circuit. A microporous polyolefin membrane can be used, which is the most commonly used material for the separator 100, mainly polypropylene or polyethylene, or a composite membrane thereof. The thickness of the separator 100 is generally 8 to 40 μm, the porosity is about 40%, and the pore size is less than 0.5 μm.

[0038] The electrolyte expansion layer 101 in this embodiment is an expansion layer supported between the diaphragm 100 and the electrode 200, which can absorb electrolyte and expand. There are many choices of materials for the electrolyte expansion layer 101, such as polystyrene and / or polystyrene derivatives.

[0039] In this embodiment, the electrolyte expansion layer 101 absorbs solvent in the electrolyte and expands, thereby increasing its thickness and volume; after the electrolyte expansion layer 101 expands, the diaphragm 100 and the electrode 200 can be stretched apart at the corner area 100a formed by the stacking and winding of the electrode 200 and the diaphragm 100, so that a certain gap is formed between the two, which is used to buffer the volume change of the electrode 200 and prevent the electrolyte from being squeezed out. In addition, the electrolyte expansion layer 101 that absorbs the electrolyte can form a layer of uniform electrolyte distribution on the surface in contact with the electrode 200, ensuring sufficient contact between the electrolyte and the surface of the electrode 200, thereby improving the electrochemical performance and safety of the battery cell.

[0040] In the technical solution of this embodiment, the electrolyte expansion layer 101 is provided in the corner area 100a of the diaphragm 100, which can effectively improve the lithium deposition phenomenon in the corner area of ​​the battery cell. The electrolyte expansion layer 101 expands after being infiltrated by the electrolyte, and can be supported between the diaphragm 100 and the corner area of ​​the pole piece 200, so that a gap for electrolyte flow is formed between the two. The gap can be used to buffer the volume change of the pole piece 200 and prevent the electrolyte from being squeezed out, thereby improving the safety and cycle life of the battery cell.

[0041] Continue reading Figure 2 In the present embodiment, the electrode sheet 200 includes a positive electrode sheet 201 and a negative electrode sheet 202 stacked with the diaphragm 100. The positive electrode sheet 201, the negative electrode sheet 202 and the diaphragm 100 are wound several times in the same direction. The diaphragm 100 includes several corner areas 100a. At least one electrolyte expansion layer 101 is provided on the side of the several corner areas 100a.

[0042] In this embodiment, after the electrode 200 and the diaphragm 100 are stacked and wound, N straight areas and corner areas 100a (i.e., the straight area, corner area 100a of the electrode 200 and the straight area, corner area 100a of the diaphragm 100) are formed. In this embodiment, at least one electrolyte expansion layer 101 is set in each corner area 100a of the diaphragm 100. The electrolyte expansion layer 101 can be located in the middle of the corner area 100a of the diaphragm 100, or at one or the other end of the corner area 100a of the diaphragm 100.

[0043] The diaphragm 100 and the pole piece 200 are stacked and wound N times to form a shape, and finally loaded into a shell, and the electrolyte is injected for packaging; according to the shell material of the package, it can be divided into a hard shell and a soft package, among which the hard shell generally adopts a steel shell or an aluminum shell as the shell, which has the advantages of high structural strength, good heat dissipation performance, mature technology, strong consistency, etc.; the soft package generally adopts an aluminum-plastic film as the shell, which has the advantages of low cost and light weight, etc.

[0044] After packaging is completed, the electrolyte expansion layer 101 absorbs the electrolyte and expands, supporting the corner area 100a of the electrode 200 and the diaphragm 100, so that a gap for electrolyte flow is formed between the two. The gap can be used to buffer the volume change of the electrode 200 and provide favorable conditions for the flow of electrolyte during the charge and discharge process.

[0045] See also Figure 3 , 4 , Figure 3 This is a schematic diagram of the structure of the diaphragm in one embodiment of the utility model. Figure 4 It is a schematic diagram of the structure of a battery cell in one embodiment of the utility model.

[0046] In some embodiments, the electrode sheet 200 includes a positive electrode sheet 201 and a negative electrode sheet 202 . The positive electrode sheet 201 , the negative electrode sheet 202 and the separator 100 are stacked and wound, and the electrolyte expansion layer 101 is arranged on the side of the corner area 100 a of the separator 100 facing away from the negative electrode sheet 202 .

[0047] In this embodiment, after the positive electrode sheet 201, the negative electrode sheet 202 and the separator 100 are stacked and wound for multiple turns, N stacked straight regions and corner regions 100a are formed respectively. Figure 3 As shown (positive electrode sheet 201, negative electrode sheet 202 and straight area and corner area 100a of diaphragm 100). The expansion rate of negative electrode sheet 202 is relatively large, because the negative electrode material will undergo a significant volume change when lithium ions are embedded, especially the silicon-based negative electrode, whose volume change can reach 300%. Therefore, in this embodiment, an electrolytic expansion layer is arranged on the side of diaphragm 100 facing away from the negative electrode sheet 202. When the negative electrode sheet 202 expands, the side of diaphragm 100 in contact with the negative electrode sheet 202 is a flat surface, which can avoid the extrusion force of the negative electrode sheet 202 from being concentrated on the surface of diaphragm 100; and the electrolyte expansion layer 101 on the back of diaphragm 100 can expand to a certain extent after absorbing the electrolyte, and has a certain elasticity. When squeezed by the negative electrode sheet 202, it can shrink to a certain extent to buffer the volume change of the negative electrode sheet 202.

[0048] Continue reading Figure 4 In this embodiment, an electrolyte expansion layer 101 is provided on the side of each corner region 100a, and the multiple electrolyte expansion layers 101 are symmetrically distributed. In this embodiment, at least one electrolyte expansion layer 101 is provided on the side of a plurality of corner regions 100a, and the electrolyte expansion layers 101 on each corner region 100a are symmetrically arranged along the same direction. In this way, a certain amount of expansion space is left between the corner region 100a of each pole piece 200 and the corner region 100a of a diaphragm 100, which is beneficial to improving the fluidity of the electrolyte and can buffer the volume change of the pole piece 200.

[0049] In addition to the symmetrical distribution of the multiple electrolyte expansion layers 101 in the above embodiment, in one embodiment, the multiple electrolyte expansion layers 101 may also be staggered. Figure 5 As shown, Figure 5 Schematic diagram of the structure of a battery cell in another embodiment of the utility model. In this embodiment, an electrolyte expansion layer 101 is provided on the side of each corner area 100a, and multiple electrolyte expansion layers 101 are staggered. Multiple staggered electrolyte expansion layers 101 can expand at different positions in the corner area, and staggered gaps can be formed. These staggered gaps are conducive to the electrolyte wetting various parts of the pole piece, thereby improving the performance and cycle life of the battery cell.

[0050] The pole piece 200 and the diaphragm 100 are stacked and wound for multiple turns. As the number of winding turns increases, the length of the corner area 100a gradually increases. The length of the corner area 100a of the outermost circle of the battery cell is longer than the corner area 100a of the inner circle. If an electrolyte expansion layer 101 is still set in the outer corner area 100a, the pole piece 200 may not be able to play a good supporting role during the expansion process. Therefore, multiple electrolyte expansion layers 101 can be arranged on the corner area 100a.

[0051] like Figure 6 As shown, Figure 6 It is a schematic structural diagram of a battery cell in another embodiment of the utility model. In this embodiment, the lengths of several corner areas 100a gradually increase with the number of turns of the diaphragm 100 wound in the same direction, and a plurality of electrolyte expansion layers 101 are provided on the side of at least one corner area 100a.

[0052] In this embodiment, the length of the corner area 100a of the diaphragm 100 gradually increases from the inner circle to the outer circle, and at the same time, the number of the electrolyte expansion layer 101 also increases accordingly, for example, the number is 1, 2, 3, etc. In this way, no matter the shorter inner part, longer middle part and outer part of the pole piece 200 expand, the corresponding number of electrolyte expansion layers 101 can provide good support and spacing for them, and buffer the volume change of the pole piece 200.

[0053] In this embodiment, a plurality of electrolyte expansion layers 101 are used to provide good support for the corner areas 100a of the diaphragm 100 and the corner areas 100a of the pole piece 200 of different lengths. At the same time, the plurality of electrolyte expansion layers 101 are arranged at intervals to reserve space for the electrolyte to flow. In this way, the corner areas 100a of the diaphragm 100 and the corner areas 100a of the pole piece 200 can be well supported, and the fluidity of the electrolyte can be guaranteed.

[0054] See also Figure 7 , Figure 71 is a schematic diagram of the structure of the diaphragm 100 in an embodiment of the present invention. In this embodiment, in order to further improve the supporting capacity of the electrolyte expansion layer 101, a plurality of electrolyte expansion layers 101 are sequentially spaced apart along the width direction of the corner area 100a.

[0055] In this embodiment, on the basis of the above embodiment, multiple electrolyte expansion layers 101 are sequentially spaced and distributed along the width direction of the corner area 100a of the separator 100, so as to avoid the concentration of extrusion force and mutual extrusion damage between the pole pieces 200. At the same time, sufficient passing gaps are reserved to ensure the permeability of the electrolyte.

[0056] See also Figure 8 , Figure 8 1 is a schematic diagram of the structure of a battery cell in another embodiment of the present utility model. In this embodiment, electrolyte expansion layers 101 are provided on both sides of the corner area 100 a facing away from each other.

[0057] In this embodiment, electrolyte expansion layers 101 are provided on both sides of the diaphragm 100. When the electrolyte expansion layers 101 on both sides expand simultaneously after absorbing the electrolyte, the adjacent electrode sheets 200 can be propped up to form a gap for the electrolyte to flow. Figure 7 As shown in , the electrolyte expansion layer 101 is effectively supported between the pole piece 200 and the diaphragm 100, which can prevent the pole piece 200 from expanding and squeezing the diaphragm 100, so that a gap is formed between the pole piece 200 and the diaphragm 100 to allow the electrolyte to flow.

[0058] As for how the electrolyte expansion layers 101 on both sides of the diaphragm 100 are distributed, in some embodiments, the electrolyte expansion layers 101 on both sides can be arranged relative to each other, that is, the electrolyte expansion layers 101 on both sides are arranged symmetrically. Of course, in other embodiments, the electrolyte expansion layers 101 on both sides can be arranged in a staggered manner, which is not particularly limited here.

[0059] In another embodiment, the electrolyte expansion layer 101 is arranged in a strip shape, and its length can increase as the length of the corner area 100a increases. For example, when the diaphragm 100 is wound, the initial length of the electrolyte expansion layer 101 located on the inner corner area 100a is 1 μm; as the number of winding turns of the diaphragm 100 increases, the length of the corner area 100a increases, and the length of the electrolyte expansion layer 101 also increases, for example, 1 μm, 1.5 μm, 2 μm, and so on. In this way, the length of the electrolyte expansion layer 101 increases as the number of winding turns of the corner area 100a of the diaphragm 100 increases, which can adapt to the change in the length of the corner area 100a of the diaphragm 100, and thus can better evenly distribute the extrusion force of the pole piece 200 after expansion.

[0060] The utility model further proposes a battery, including a battery cell of the aforementioned embodiment, the specific structure of which refers to the aforementioned embodiment, and since the battery adopts all the technical solutions of all the aforementioned embodiments, it at least has all the technical effects brought by the technical solutions of the aforementioned embodiments, which will not be described one by one here. Since the electrolyte expansion layer 101 expands after being infiltrated by the electrolyte, it is supported between the corner area 100a of the diaphragm 100 and the corner area 100a of the adjacent pole piece 200 to form a gap, which can avoid the situation in which the electrolyte is squeezed out of the gap due to the expansion of the pole piece 200 during the cycle process, and can effectively prevent lithium deposition at the corner of the battery cell, thereby making the battery cycle stability and service life better.

[0061] The present invention further proposes an electrical device that uses the battery in the above embodiment as a power source. The electrical device includes but is not limited to mobile phones, Bluetooth headsets, tablets, mobile power supplies, laptop computers, electric toys, electric tools, battery vehicles, electric vehicles, ships, spacecraft, etc.

[0062] The above description is only a partial or preferred embodiment of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A battery cell, characterized in that: It includes a pole piece and a diaphragm, the diaphragm and the pole piece are stacked, the pole piece and the diaphragm are wound in the same direction, the pole piece and the diaphragm both include a corner area formed during the winding, at least one side surface of the corner area of ​​the diaphragm is provided with an electrolyte expansion layer, the electrolyte expansion layer is supported between the diaphragm and the corner area of ​​the pole piece, and is used to support a gap for the electrolyte to flow.

2. The battery cell according to claim 1, characterized in that: The electrode sheets include a positive electrode sheet and a negative electrode sheet stacked with the diaphragm. The positive electrode sheet, the negative electrode sheet and the diaphragm are wound several times in the same direction. The diaphragm includes several corner areas formed by winding several times. The sides of the several corner areas are each provided with at least one electrolyte expansion layer.

3. The battery cell according to claim 2, characterized in that: The electrolyte expansion layer is provided on the side of each corner area, and the plurality of electrolyte expansion layers are symmetrically distributed.

4. The battery cell according to claim 2, characterized in that: The electrolyte expansion layer is provided on the side of each corner area, and a plurality of the electrolyte expansion layers are staggeredly distributed.

5. The battery cell according to claim 2, characterized in that: The lengths of the corner regions gradually increase as the number of turns of the diaphragm is wound in the same direction, and a plurality of electrolyte expansion layers are provided on the side of at least one of the corner regions.

6. The battery cell according to claim 5, characterized in that: The plurality of electrolyte expansion layers are sequentially spaced and distributed along the length direction of the corner area.

7. The battery cell according to claim 5 or 6, characterized in that: The plurality of electrolyte expansion layers are sequentially spaced apart and distributed along the width direction of the corner area.

8. The battery cell according to claim 2, characterized in that: The electrolyte expansion layer is in strip shape.

9. A battery, characterized in that: A battery cell comprising the battery cell described in any one of claims 1 to 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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