Winding battery cell, battery and power utilization device

Abstract

The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a winding battery cell which comprises a positive plate, an isolating membrane and a negative plate which are sequentially stacked and wound, and the winding battery cell comprises a flat part and corner parts arranged at the two ends of the flat part, the positive plate comprises a first current collector and first material layers coated on two surfaces of the first current collector, at least one surface of the first material layer located at the corner part is provided with a thinning area, and the thinning area is provided with a swelling layer. The swelling layer in the lithium ion battery can absorb swelling of electrolyte, plays a buffering role, reduces mutual extrusion between the pole pieces, and avoids loss of the electrolyte located at the corner in the later cycle process, so that the lithium precipitation phenomenon at the corner of the battery cell is effectively improved. In addition, the utility model also discloses a battery and an electric device.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery production and manufacturing, and specifically relates to a wound battery core, a battery and an electrical device. Background Art

[0002] Nowadays, with the development of modern society and the enhancement of people's environmental awareness, more and more devices choose lithium-ion batteries as power sources, such as mobile phones, laptops, power tools and electric vehicles, which provides a broad space for the application and development of lithium-ion batteries.

[0003] Among them, the winding structure is one of the commonly used structures of the battery. The battery with the winding structure will form a corner position. The length of the positive electrode sheet in the area where the positive electrode sheet covers the negative electrode sheet on the side of the corner position is greater than the length of the negative electrode sheet, resulting in the negative electrode excess coefficient in this area being lower than that in the normal area. In addition, during the cycle, the negative electrode sheet will gradually expand due to the embedding of lithium ions, but due to the mutual restraint between the electrodes at the corners of the battery cell, the expanded negative electrode sheet will continuously squeeze the adjacent diaphragm and positive electrode sheet, causing stress concentration in the local area at the corner of the battery cell, resulting in the electrolyte in this area being gradually squeezed away, the reduction of the negative electrode excess coefficient and the gradual loss of electrolyte during the cycle, resulting in the electrode interface beginning to deteriorate and lithium precipitation, which ultimately affects the battery's cycle performance. To this end, it is urgent to propose a new technical solution to solve the above problems. Utility Model Content

[0004] One of the purposes of the utility model is to provide a wound battery cell in view of the deficiencies of the prior art, which improves the lithium deposition phenomenon at the corners of the wound battery cell by providing a thinning area and a swelling layer in the thinning area.

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

[0006] A wound battery cell comprises a positive electrode sheet, a separator and a negative electrode sheet stacked and wound in sequence, the wound battery cell comprises a flat portion and corner portions arranged at both ends of the flat portion, the positive electrode sheet comprises a first current collector and a first material layer coated on both sides of the first current collector, at least one surface of the first material layer located at the corner portion is provided with a thinning area, and the thinning area is provided with a swelling layer.

[0007] In the utility model, the material of the swelling layer is PVDF, PVDF-HFP, PMMA or one of other polymers with good compatibility with the electrolyte. In practical applications, the swelling layer expands after absorbing the electrolyte, has a buffering effect, can reduce the force exerted on the electrode due to the extrusion between the electrode pieces, and at the same time, can store the electrolyte and improve the lithium deposition problem at the corner.

[0008] As an improvement of the positive electrode plate described in the utility model, the thinning area is configured as a groove structure sunken into the first material layer, the swelling layer covers and fills the thinning area, and the swelling layer fills the thinning area, which can buffer the force to the greatest extent possible.

[0009] As an improvement of the positive electrode plate described in the utility model, the thickness D1 of the thinned area and the thickness D2 of the swelling layer satisfy the relationship: D1=a×D2, a is an adjustment constant, 0.2≤a≤1.

[0010] As an improvement of the positive electrode plate described in the utility model, the thickness D1 of the thinned area and the thickness D3 of the first material layer satisfy the relationship: D1=b×D3, b is an adjustment constant, 0.85≤b≤0.95.

[0011] As an improvement of the positive electrode sheet of the utility model, the lengths of the thinned area and the swelling layer in the width direction of the positive electrode sheet are the same as the width of the positive electrode sheet.

[0012] As an improvement of the positive electrode sheet described in the utility model, the widths of the thinned area and the swelling layer in the length direction of the positive electrode sheet are both W, W=πR, and R is the radius of an arc formed by the thinned area after the positive electrode sheet is wound.

[0013] As an improvement of the positive electrode plate of the utility model, the swelling layer is embedded in the first material layer on a side facing the first material layer.

[0014] As an improvement of the positive electrode plate of the utility model, the swelling layer is located on a side of the corner portion facing the winding center and / or a side facing away from the winding center.

[0015] The second purpose of the present utility model is to provide a battery, comprising the wound battery cell as described above.

[0016] The third object of the present utility model is to provide an electrical device comprising the battery as described above.

[0017] The beneficial effect of the utility model is that the wound battery cell of the utility model comprises a positive electrode sheet, a separator and a negative electrode sheet which are stacked and wound in sequence, the wound battery cell comprises a flat portion and corner portions arranged at both ends of the flat portion, the positive electrode sheet comprises a first current collector and a first material layer coated on both sides of the first current collector, at least one surface of the first material layer located at the corner portion is provided with a thinning area, and the thinning area is provided with a swelling layer. The utility model is first provided with a thinning area. In practical applications, the provision of the thinning area allows gaps to be provided between the pole pieces, reduces the extrusion between the corner portions of the pole pieces, and improves the lithium precipitation phenomenon; in addition, the thinning area is provided with a swelling layer, and the swelling layer expands after absorbing the electrolyte, which can buffer the force caused by the extrusion between the pole pieces, and at the same time, can also serve as a storage function for the electrolyte, further improving the lithium precipitation phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0019] Figure 1 It is a structural schematic diagram of the utility model.

[0020] Figure 2 It is a structural schematic diagram of the positive electrode sheet in the utility model.

[0021] Figure 3 It is a cross-sectional schematic diagram of the positive electrode sheet in the utility model.

[0022] Figure 4 This is one of the structural schematic diagrams of the positive electrode sheet in the practical application of the utility model.

[0023] Figure 5 This is the second structural schematic diagram of the positive electrode sheet in the practical application of the utility model.

[0024] Figure 6 It is a cross-sectional schematic diagram of the negative electrode sheet in the utility model.

[0025] The reference numerals are described as follows:

[0026] 100-positive electrode sheet; 1-first current collector; 2-first material layer; 23-thinning area; 24-swelling layer; X-width direction; Y-length direction;

[0027] 200-isolation film;

[0028] 300 - negative electrode sheet; 301 - second current collector; 302 - second material layer;

[0029] 400-leveling part;

[0030] 500-Corner. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application 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. Reference to "embodiment" in this application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places 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.

[0033] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0034] The term "plurality" used in the present application refers to two or more (including two).

[0035] The battery cell includes a wound cell and an electrolyte. The wound cell is composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer. The positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode collector. The negative electrode collector not coated with the negative electrode active material layer protrudes from the negative electrode collector coated with the negative electrode active material layer. The negative electrode collector not coated with the negative electrode active material layer serves as the negative electrode tab. The negative electrode current collector may be made of copper, and the negative electrode active material may be carbon or silicon. In order to ensure that a large current can pass without melting, the positive electrode tabs are multiple and stacked together, and the negative electrode tabs are multiple and stacked together. The material of the separator may be polypropylene or polyethylene.

[0036] The development of battery technology must consider many design factors at the same time, such as performance parameters such as energy density, cycle life, discharge capacity, charge and discharge rate, and battery safety. In addition, the battery safety also needs to be considered. In a battery with a wound structure, the positive electrode, separator, and negative electrode are wound in sequence to form a corner. There will be a large squeezing force between the positive and negative electrode sheets at the corner, resulting in lithium precipitation. In view of this, this embodiment reduces the squeezing force between the electrode sheets and buffers the electrolyte by setting a thinning area and a swelling layer, thereby improving the lithium precipitation phenomenon.

[0037] The following is combined with Figures 1 to 6 The utility model is further described in detail with specific implementation modes, but is not intended to limit the utility model.

[0038] A wound battery cell comprises a positive electrode sheet 100, a separator 200 and a negative electrode sheet 300 which are stacked and wound in sequence, the wound battery cell comprising a flat portion 400 and corner portions 500 arranged at both ends of the flat portion 400; the positive electrode sheet 100 comprises a first current collector 1 and a first material layer 2 coated on both sides of the first current collector 1, at least one surface of the first material layer 2 located at the corner portion 500 is provided with a thinning area 23, and the thinning area 23 is provided with a swelling layer 24; the negative electrode sheet 300 comprises a second current collector 301 and a second material layer 302 coated on both sides of the second current collector 301.

[0039] In this embodiment, the thinning area 23 is provided so that in actual application, there is a gap between the positive electrode sheet 100 and the negative electrode sheet 300 wound therewith, which can reduce the extrusion between the electrode sheets and improve the lithium deposition phenomenon.

[0040] In this embodiment, the material of the swelling layer 24 is PVDF, PVDF-HFP, PMMA or one of other polymers with good compatibility with the electrolyte. In practical applications, the swelling layer 24 expands after absorbing the electrolyte, has a buffering effect, can reduce the force on the electrode due to the extrusion between the electrode sheets, and at the same time, can store the electrolyte to improve the lithium deposition problem at the corner 500; it can be understood that the expansion of the negative electrode sheet 300 is a hard expansion, which belongs to the expansion force between the lattices, while the swelling layer 24 and the swelling layer 24 after expansion are soft in texture, located between the positive and negative electrode sheets, and there will be no extrusion problem between the electrode sheets.

[0041] In addition, the thinning area 23 in the present embodiment is arranged on the positive electrode sheet 100, and the negative electrode sheet 300 is not provided with the thinning area 23. The reason is that the presence of the swelling layer 24 whose material is a polymer can reduce the migration rate of lithium ions. It is arranged on the positive electrode sheet 100, which can reduce the speed of lithium ions being transmitted from the positive electrode to the negative electrode during charging, which is beneficial for lithium insertion in the negative electrode. However, if it is arranged on the negative electrode sheet 300, the speed of lithium ion transmission at the positive electrode is not reduced, but the rate of lithium insertion at the negative electrode is reduced, which may cause the negative electrode kinetic performance to deteriorate, resulting in serious lithium precipitation.

[0042] Preferably, the thinning area 23 is configured as a groove structure sunken into the first material layer 2, and the swelling layer 24 covers and fills the thinning area 23, so that the swelling layer 24 can cover the thinning area 23, thereby maximally buffering the force between the pole pieces.

[0043] Preferably, the side of the swelling layer 24 facing the first material layer 2 is embedded in the first material layer 2 to effectively enhance the adhesion strength between the swelling layer 24 and the first material layer 2 .

[0044] Preferably, the swelling layer 24 is located on a side of the corner portion 500 facing the winding center and / or a side facing away from the winding center. The position of the swelling layer 24 can be adjusted as needed, thereby effectively improving the flexibility of the battery cell structure.

[0045] Preferably, the thickness D1 of the thinned area 23 and the thickness D2 of the swelling layer 24 satisfy the relationship: D1=a×D2, a is an adjustment constant, 0.2≤a≤0.3, 0.3≤a≤0.4, 0.4≤a≤0.5, 0.5≤a≤0.6, 0.6≤a≤0.7, 0.7≤a≤0.8, 0.8≤a≤0.9, 0.9≤a≤1.

[0046] Preferably, the thickness D1 of the thinned area 23 and the thickness D3 of the first material layer 2 satisfy the relationship: D1=b×D3, where b is an adjustment constant, 0.85≤b≤0.95.

[0047] Preferably, the lengths of the thinned region 23 and the swelling layer 24 in the width direction X of the positive electrode sheet 100 are the same as the width of the positive electrode sheet 100 .

[0048] Preferably, the widths of the thinned area 23 and the swelling layer 24 in the length direction Y of the positive electrode sheet 100 are both W, W=πR, and R is the radius of an arc formed by the thinned area 23 after the positive electrode sheet 100 is wound.

[0049] The above-mentioned size setting can alleviate the lithium decomposition problem of the positive electrode while ensuring the implementation of its basic electrical functions.

[0050] like Figure 4 As shown, the thinning area 23 is located on the inner side of the first material layer 2 relative to the winding center, and the thickness D1 of the thinning area 23 and the thickness D2 of the swelling layer 24 satisfy the relationship: D1 = D2; Figure 5 As shown, the thinning area 23 is located outside the first material layer 2 relative to the winding center, and the thickness D1 of the thinning area 23 and the thickness D2 of the swelling layer 24 satisfy the relationship: D1 = 0.5 × D2. In some other embodiments, the thinning area 23 can also be arranged on both sides of the first material layer 2 in the width direction X, or a plurality of thinning areas 23 can be arranged, which can be adjusted according to actual needs and will not be described in detail.

[0051] In order to better reflect the beneficial effects of this embodiment, the following examples and comparative examples are provided for illustration.

[0052] Example 1

[0053] In this embodiment, the positive electrode plate is provided with a thinning area 23, the thickness of the thinning area 23 is set to 3 μm, and a swelling layer 24 with a thickness of 3 μm is coated on the thinning area 23, and the material of the swelling layer 24 is set to PMMA.

[0054] Example 2

[0055] In this embodiment, the positive electrode plate is provided with a thinning area 23, the thickness of the thinning area 23 is set to 4 μm, and a swelling layer 24 with a thickness of 4 μm is coated on the thinning area 23, and the material of the swelling layer 24 is set to PVDF.

[0056] Example 3

[0057] In this embodiment, the positive electrode plate is provided with a thinning area 23, the thickness of the thinning area 23 is set to 5 μm, and a swelling layer 24 with a thickness of 5 μm is coated on the thinning area 23, and the material of the swelling layer 24 is set to PVDF-HFP.

[0058] Example 4

[0059] In this embodiment, the positive electrode plate is provided with a thinning area 23, the thickness of the thinning area 23 is set to 5 μm, and a swelling layer 24 with a thickness of 1 μm is coated on the thinning area 23, and the material of the swelling layer 24 is set to PVDF-HFP.

[0060] Example 5

[0061] In this embodiment, the positive electrode plate is provided with a thinning area 23, the thickness of the thinning area 23 is set to 4 μm, and a swelling layer 24 with a thickness of 2 μm is coated on the thinning area 23, and the material of the swelling layer 24 is set to PVDF-HFP.

[0062] Comparative Example 1

[0063] In this comparative example, the positive electrode sheet is not provided with a thinning area 23 .

[0064] Comparative Example 2

[0065] In this comparative example, the positive electrode sheet is provided with a thinned area 23, and the thickness of the thinned area 23 is 3 μm.

[0066] Comparative Example 3

[0067] In this comparative example, the positive electrode sheet is provided with a thinned area 23, and the thickness of the thinned area 23 is 5 μm.

[0068] The positive electrode sheet, separator and negative electrode sheet in the above embodiment and comparative example are respectively wound in sequence under the same conditions to prepare the same type of wound battery cells, wherein the single surface density of the positive electrode is 280 mg / 1540.25 mm 2 The current collector thickness is 10 μm, and the negative electrode single surface density is 148 mg / 1540.25 mm 2 , the current collector thickness is 5μm, the material area thickness of the positive electrode sheet 100 on each side is 43μm after rolling, the material area thickness of the negative electrode sheet 300 on each side is 58μm, the positive and negative electrode CB values ​​are 1.05, and the above-mentioned wound battery cells are subjected to 1C / 1C cycle charge and discharge, and the cycle attenuation and corner lithium plating after 500 cycles are compared to obtain the experimental results shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] It can be seen from the above table that the provision of the thinned area 23 and the swelling layer 24 can improve the lithium deposition phenomenon at the corner portion 500 .

[0073] Battery

[0074] A battery, comprising a wound battery cell as described above, and the battery may be a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, etc. In the present application, the battery may include a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery or a magnesium-ion battery, etc., and the embodiments of the present application do not limit this. The battery may be cylindrical, flat, rectangular or in other shapes, etc., and the embodiments of the present application do not limit this. Batteries are generally divided into three types according to the packaging method: cylindrical batteries, square batteries and soft-pack batteries, and the embodiments of the present application do not limit this.

[0075] Electrical devices

[0076] An electrical device, comprising a battery as described above. The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.; the spacecraft may include an airplane, a rocket, a space shuttle and a spacecraft, etc.; the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric airplane toy, etc.; the electric tool may include a metal cutting electric tool, a grinding electric tool, an assembly electric tool and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0077] 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 wound battery cell, comprising a positive electrode sheet (100), a separator (200) and a negative electrode sheet (300) stacked and wound in sequence, characterized in that: The wound battery cell comprises a flat portion (400) and corner portions (500) arranged at both ends of the flat portion (400); the positive electrode sheet (100) comprises a first current collector (1) and a first material layer (2) coated on both sides of the first current collector (1); at least one surface of the first material layer (2) located at the corner portion (500) is provided with a thinning area (23); and the thinning area (23) is provided with a swelling layer (24).

2. The wound battery cell according to claim 1, characterized in that: The thinned area (23) is configured as a groove structure sunken into the first material layer (2), and the swelling layer (24) covers and fills the thinned area (23).

3. The wound battery cell according to claim 1 or 2, characterized in that: The thickness D1 of the thinned area (23) and the thickness D2 of the swelling layer (24) satisfy the relationship: D1=a×D2, a is an adjustment constant, 0.2≤a≤1.

4. The wound battery cell according to claim 1 or 2, characterized in that: The thickness D1 of the thinned area (23) and the thickness D3 of the first material layer (2) satisfy the relationship: D1=b×D3, b is an adjustment constant, 0.85≤b≤0.

95.

5. The wound battery cell according to claim 1 or 2, characterized in that: The lengths of the thinned region (23) and the swelling layer (24) in the width direction (X) of the positive electrode sheet (100) are both the same as the width of the positive electrode sheet (100).

6. The wound battery cell according to claim 1 or 2, characterized in that: The widths of the thinned area (23) and the swelling layer (24) in the length direction (Y) of the positive electrode sheet (100) are both W, W=πR, and R is the radius of an arc formed by the thinned area (23) after the positive electrode sheet (100) is wound.

7. The wound battery cell according to claim 1 or 2, characterized in that: The swelling layer (24) is embedded in the first material layer (2) on a side facing the first material layer (2).

8. The wound battery cell according to claim 1 or 2, characterized in that: The swelling layer (24) is located on a side of the corner portion (500) facing the winding center and / or a side facing away from the winding center.

9. A battery, characterized in that: It comprises a wound battery cell as described in any one of claims 1 to 8.

10. An electrical device, characterized in that: Comprising the battery as claimed in claim 9.

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