Secondary battery and battery module
By designing buffer components in lithium-ion batteries to alleviate the expansion stress of electrode components and realize the circulating flow of electrolyte, the problem of overflow and replenishment of electrolyte is solved, and the cycle life of lithium-ion batteries is extended.
Patent Information
- Application Number
- CN202420648946.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-29
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2034-03-29
AI Technical Summary
During the cycle, the expansion of the electrode assembly leads to the overflow of the electrolyte and the consumption of the electrolyte, which shortens the battery life. The expansion force increases after the battery volume increases, and the electrolyte is difficult to replenish, which affects the battery performance.
Design a secondary battery and battery module, including a housing, a buffer assembly and an electrode assembly, the buffer assembly includes a separator and a buffer body, which can relieve stress and temporarily store the electrolyte when the electrode assembly expands, ensuring that the electrolyte is in the electrode The components are circulated and flowing internally to solve the problems of overflow and difficulty in replenishing the electrolyte.
Effectively alleviate the expansion stress of the electrode assembly, improve the uniform stress on the inner electrode assembly, extend the cycle life of the lithium-ion battery, and ensure the electrolyte circulation and replenishment through the design of the buffer assembly, improving the service life of the battery.
Smart Images
Figure CN222146385U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a secondary battery and a battery module. Background Art
[0002] Lithium-ion batteries are widely used in digital, automotive, energy storage and other fields. As the application areas expand, the demand for their performance is also increasing.
[0003] During the cycle, as byproducts accumulate, lithium-ion batteries will gradually expand and electrolyte will overflow at the connection between the electrode assembly and the tab. Under greater stress, the shell may even deform and leak. In addition, during the cycle, the electrolyte will be gradually consumed. Due to the influence of gravity, it is difficult to effectively replenish the electrolyte at the top of the electrode assembly, causing lithium to precipitate at the top of the battery, shortening the battery life and even causing a "diving" situation. Therefore, electrolyte overflow and electrolyte consumption caused by battery expansion are important problems faced by lithium-ion batteries during use.
[0004] In order to reduce costs, the volume of existing lithium-ion batteries has gradually increased, but there are two problems: on the one hand, as the volume of lithium-ion batteries increases, the expansion force per unit area becomes greater and greater; on the other hand, as the height of the battery increases, it becomes more difficult to wet the top of the battery; therefore, the battery life problem is increasingly exposed. How to effectively solve the expansion of lithium-ion batteries and how to replenish electrolytes are imminent. Utility Model Content
[0005] In order to solve the defects of the prior art that electrolyte overflows due to the expansion of the electrode assembly, and lithium deposition occurs due to the difficulty in replenishing the electrolyte on the top of the electrode assembly, thereby shortening the battery life, a secondary battery and a battery module are provided. The product of the present application can relieve stress when the electrode assembly expands, and through the internal structure design of the secondary battery, the electrolyte can be temporarily stored, and when squeezed, it can be directed back to the inside of the electrode assembly; thereby effectively improving the cycle life of the lithium-ion battery.
[0006] The utility model mainly solves the above technical problems through the following technical solutions.
[0007] In a first aspect, the utility model provides a secondary battery, comprising a shell, and a buffer assembly and N electrode assemblies respectively disposed inside the shell, where N is a positive integer greater than or equal to 1;
[0008] A tab extends from the top of the electrode assembly;
[0009] The buffer assembly includes a liquid isolating member and a buffer body, wherein the liquid isolating member is attached to the side wall surface of the electrode assembly to form a cavity with an opening at one end, the interior of the cavity is filled with the buffer body, and the direction of the opening of the cavity is consistent with the extension direction of the electrode assembly toward the electrode ear;
[0010] The position of the buffer assembly satisfies at least one of the following conditions:
[0011] ① The buffer assembly is arranged inside the electrode assembly;
[0012] ②The buffer assembly is arranged between the electrode assembly and the shell.
[0013] In a second aspect, the utility model provides a battery module, which includes the secondary battery as described above.
[0014] The positive and progressive effects of the utility model are:
[0015] (1) The product of the present application can relieve stress when the electrode assembly expands and improve the uniform force on the electrode sheets inside the electrode assembly; it can also improve problems such as electrode assembly diving and uneven force on the electrode sheets caused by large expansion force.
[0016] (2) In the product of the present application, a buffer component having the function of absorbing and storing electrolyte is provided to temporarily store electrolyte when the electrode component is squeezed, and can be gradually released during the cycle to replenish the electrolyte consumed in the electrode component;
[0017] (3) The product of the present application can replenish the electrolyte on the top of the electrode assembly, solving the problem of poor electrolyte infiltration on the top, thereby effectively improving the cycle life of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 This is a schematic diagram of the internal structure of a secondary battery according to Embodiment 1 of the present utility model;
[0019] Figure 2 This is a schematic diagram of the flow direction of the electrolyte when the electrode assembly of the secondary battery of Example 1 of the utility model is squeezed;
[0020] Figure 3 This is a schematic diagram of the flow direction of electrolyte in the secondary battery of Example 1 of the utility model when the buffer assembly is squeezed;
[0021] Figure 4 It is a cross-sectional schematic diagram of a buffer assembly and an electrode assembly according to Embodiment 1 of the present utility model;
[0022] Figure 5 This is a schematic diagram of the structure of the buffer assembly of Example 1 of the utility model;
[0023] Figure 6 This is an assembly front view of the buffer assembly of Example 1 of the utility model;
[0024] Figure 7 This is a bottom schematic diagram of the buffer assembly of Example 1 of the utility model;
[0025] Figure 8 This is a front view of a secondary battery according to Embodiment 1 of the present utility model;
[0026] Fig. 9 Schematic diagram of the structure of the secondary battery of Comparative Example 1;
[0027] Fig.10 It is a comparison chart of the relationship between the cycle number and the capacity retention rate of the secondary batteries of Example 1 and Comparative Example 1.
[0028] Description of reference numerals:
[0029] Shell 1
[0030] Buffer component 2
[0031] Liquid barrier 201
[0032] Buffer body 202
[0033] One-way valve 203
[0034] Open end 204
[0035] Electrode assembly 3
[0036] Tab 4
[0037] Positive electrode tab 401
[0038] Negative electrode tab 402
[0039] Top cover 5
[0040] Pole 6
[0041] Positive pole 601
[0042] Negative electrode post 602. DETAILED DESCRIPTION
[0043] In the secondary battery of the present utility model:
[0044] In the utility model, when the electrode assembly is squeezed, the electrolyte will overflow from the connection between the electrode assembly and the electrode ear; by providing a buffer assembly, on the one hand, the expansion of the electrode assembly can be alleviated, and on the other hand, the overflowed electrolyte can be adsorbed and temporarily stored; and, after the electrode assembly is squeezed, the electrolyte temporarily stored in the buffer assembly can flow back from the open end of the buffer assembly through the top of the electrode assembly to the inside of the electrode assembly, so as to prevent the problem of difficulty in wetting on the top of the electrode assembly.
[0045] In the present invention, the “electrode assembly” may be understood as a conventional “battery cell” in the art.
[0046] In the present invention, the electrode assembly can be divided into a side wall surface, a bottom surface and a top surface connected to the electrode tab in terms of three-dimensional structure.
[0047] In some embodiments, the compressibility of the buffer component is ≥30%, where the compressibility refers to the volume shrinkage rate when subjected to a compressive force.
[0048] In a specific embodiment, the compressibility of the cushioning component is greater than 70%.
[0049] In some embodiments, the stress-strain modulus of the buffer component is 0.001-0.1 MPa / %, and 0.001-0.1 MPa / % means that the unit percentage stress is between 0.001 and 0.1 MPa; thereby, the buffer component has a certain elasticity and strength to ensure that the interface of the electrode assembly remains flat during the charge and discharge process, and prevent the buffer component from being collapsed when squeezed.
[0050] In some embodiments, when the number of the electrode assemblies is greater than or equal to 2, the buffer assembly is disposed between any two of the electrode assemblies.
[0051] In some embodiments, the material of the buffer body includes silicone rubber, wood cellulose fiber or foamed plastic polymer.
[0052] In a specific embodiment, the foamed plastic polymer is one or more of polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyurethane, polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, vinyl alcohol copolymer, polyaminobismaleamide, polytriazine, cross-linked polyimide, epoxy resin, polysulfone, polyethersulfone, polyphenylene sulfide, polyimide and polyetheretherketone; wherein the epoxy resin can be a conventional heat-resistant resin in the art.
[0053] In some embodiments, the buffer body has a porous structure.
[0054] In some embodiments, the porosity of the buffer body is ≥30%.
[0055] In the utility model, the buffer body can act as a liquid storage layer and / or a supporting layer; when the buffer body acts as a liquid storage layer, the buffer body is sponge-shaped and can be used to accommodate the electrolyte squeezed out from the electrode assembly, and can also be used to provide electrolyte to the top of the electrode assembly; when the buffer body acts as a supporting layer, the buffer body is a hollow structure and is filled with a plurality of sponges for absorbing electrolyte, which can be used to accommodate the electrolyte squeezed out from the electrode assembly, and can also be used to provide electrolyte to the top of the electrode assembly.
[0056] In some embodiments, a one-way valve is provided at the bottom of the buffer component, and the diameter of the one-way valve is ≤5 mm. The one-way valve is used to allow the electrolyte in the shell to flow into the buffer component in one direction and prevent the temporarily stored electrolyte from flowing out of the buffer component.
[0057] Wherein, in a non-fully charged state, the extrusion pressure of the electrode assembly is limited, and the electrolyte enters the buffer assembly through the one-way valve.
[0058] In a specific embodiment, the one-way valve is a conventional one-way valve in the art, which is truncated cone-shaped and includes a hard opening and a soft channel.
[0059] In some embodiments, the position of the open end of the cavity is flush with the position of the connection between the electrode assembly and the electrode ear; so that when the electrode assembly is squeezed, the electrolyte overflows from the connection between the electrode assembly and the electrode ear and is temporarily stored in the buffer assembly. When the buffer assembly is squeezed, the electrolyte can return from the buffer assembly through the connection to the interior of the electrode assembly.
[0060] In some embodiments, the material of the liquid separator may be a plastic polymer, including polypropylene (PP), polyethylene (PE) or polyethylene terephthalate (PET); the purpose of using a fully enclosed material for the liquid separator is to ensure that the electrolyte cannot flow out from the side and bottom of the buffer component and can only flow out from the open end.
[0061] In some embodiments, the secondary battery further includes a top cover and a pole, one side of the top cover is in contact with the pole tab, and the other side of the top cover is in contact with the pole.
[0062] In some embodiments, the shell is made of metal aluminum.
[0063] Example 1
[0064] This embodiment is a secondary battery. Figure 1 is a schematic diagram of the internal structure of the secondary battery of this embodiment; Figure 4 is a cross-sectional schematic diagram of the buffer assembly and the electrode assembly of this embodiment; Figure 5 is a schematic structural diagram of the buffer assembly of this embodiment; Figure 6 This is an assembly front view of the buffer assembly of this embodiment; Figure 8 It is a front view of the secondary battery of this embodiment.
[0065] The secondary battery comprises a shell 1, and a buffer assembly 2 and two electrode assemblies 3 respectively arranged inside the shell 1; a pole ear 4 extends from the top of the electrode assembly 3; the buffer assembly 2 comprises a liquid isolating member 201 and a buffer body 202, the liquid isolating member 201 is attached to the side wall of the electrode assembly 3, and forms a cavity with an open end, the interior of the cavity is filled with the buffer body 202, and the direction of the opening of the cavity is consistent with the extension direction of the electrode assembly 3 toward the pole ear 4; the buffer assembly 2 is arranged between the two electrode assemblies 3, and between the electrode assembly 3 and the shell 1.
[0066] The compressibility of the buffer component 2 is 80%, and the stress-strain modulus is 0.1 MPa / %. The material of the buffer body 202 is polypropylene, which is a foamed plastic polymer. The buffer body 202 acts as a liquid storage layer, and has a sponge-like porous structure with a porosity of 50%. It can be used to accommodate the electrolyte squeezed out from the electrode component 3, and can also be used to provide electrolyte to the top of the electrode component 3.
[0067] Figure 7 : is a schematic diagram of the bottom surface of the buffer assembly 2 of this embodiment. A one-way valve 203 is provided at the bottom of the buffer assembly 2. The diameter of the one-way valve 203 is ≤5mm. The one-way valve 203 is used to allow the electrolyte in the housing 1 to flow into the buffer assembly 2 in one direction and prevent the temporarily stored electrolyte from flowing out of the buffer assembly 2. The position of the opening end 204 of the cavity is flush with the position of the connection between the electrode assembly 3 and the pole ear 4; the material of the liquid separator 201 is polypropylene.
[0068] The secondary battery further includes a top cover 5 and a pole 6. One side of the top cover 5 is in contact with the pole lug 4, and the other side of the top cover 5 is in contact with the pole 6. The material of the housing 1 includes metal aluminum.
[0069] By adopting the structural design of the present application, when the electrode assembly is squeezed, the electrolyte will overflow from the connection between the electrode assembly and the electrode ear and be temporarily stored in the buffer assembly; when the buffer assembly is squeezed, the electrolyte will flow back from the buffer assembly to the electrode assembly, thereby achieving a circulating flow of the electrolyte. Figure 2 is a schematic diagram of the flow direction of the electrolyte of the secondary battery of this embodiment when the electrode assembly is squeezed; Figure 3 It is a schematic diagram of the flow direction of electrolyte when the buffer assembly of the secondary battery of this embodiment is squeezed.
[0070] Comparative Example 1
[0071] This comparative example is a secondary battery. Fig. 9Schematic diagram of the structure of the secondary battery of this comparative example. The secondary battery comprises a housing 1, and two electrode assemblies 3 arranged inside the housing 1 and attached to each other; the top of the electrode assembly 3 extends a positive electrode tab 401 and a negative electrode tab 402 respectively; the secondary battery also comprises a top cover 5 and a pole 6, one side of the top cover 5 is attached to the positive electrode tab 401 and the negative electrode tab 402, and the other side of the top cover 5 is correspondingly attached with a positive pole 601 and a negative pole 602. The material of the housing 1 comprises metal aluminum.
[0072] Effect Example 1
[0073] The conventional Cycle test method in the art was used to test the capacity retention rates of the secondary batteries of Example 1 and Comparative Example 1 at different cycle numbers. The test conditions were as follows: at 25°C, charging was performed at 1C and charging was performed at a constant voltage of 4.2V to 0.02C; discharging was performed at 1C and discharged to 2.8V. The capacity retention rate was calculated according to the conventional method in the art. This effect embodiment tested the relationship between each cycle number and the capacity retention rate.
[0074] Fig.10 It is a comparison chart of the relationship between the number of cycles and the capacity retention rate of the secondary batteries of Example 1 and Comparative Example 1. This effect embodiment tests the capacity retention rate under different numbers of cycles, and is presented in the form of a straight line due to the dense points; it can be seen from the figure that with the increase of the number of cycles, the capacity retention rate of the secondary battery generally shows a downward trend; however, with the increase of the number of cycles, the degree of decrease in the capacity retention rate of the secondary batteries of Example 1 and Comparative Example 1 is different. For example, when the number of cycles of the secondary battery of Comparative Example 1 is 871 and 1531, its capacity retention rate is reduced to 90.59% and 81.38%, respectively; when the number of cycles of the secondary battery of Example 1 is 1235 and 2145, its capacity retention rate is reduced to 90.28% and 81.77%, respectively. It can be seen that through structural design, the secondary battery of the present application can increase the number of cycles of the secondary battery when it is reduced to the same capacity retention rate, effectively improving the cycle life of the lithium-ion battery.
Claims
1. A secondary battery, characterized in that: It comprises a shell, and a buffer assembly and N electrode assemblies respectively arranged inside the shell, where N is a positive integer greater than or equal to 1; A tab extends from the top of each electrode assembly; The buffer assembly includes a liquid isolating member and a buffer body, wherein the liquid isolating member is attached to the side wall surface of the electrode assembly to form a cavity with an opening at one end, the interior of the cavity is filled with the buffer body, and the direction of the opening of the cavity is consistent with the extension direction of the electrode assembly toward the electrode ear; The position of the buffer assembly satisfies at least one of the following conditions: ① The buffer assembly is arranged inside the electrode assembly; ②The buffer assembly is arranged between the electrode assembly and the shell.
2. The secondary battery according to claim 1, wherein: The compressibility of the buffer component is ≥30%; The stress-strain modulus of the buffer component is 0.001-0.1 MPa / %.
3. The secondary battery according to claim 2, characterized in that: The compressibility of the buffer component is greater than 70%.
4. The secondary battery according to claim 1, wherein: When the number of the electrode assemblies is greater than or equal to 2, the buffer assembly is disposed between any two of the electrode assemblies.
5. The secondary battery according to claim 1, wherein: The material of the buffer body is silicone rubber, wood cellulose fiber or foamed plastic polymer.
6. The secondary battery according to claim 5, characterized in that: The foamed plastic polymer is one of polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyurethane, polyamide, polyoxymethylene, polycarbonate, modified polyphenylene ether, thermoplastic polyester, vinyl alcohol copolymer, polyaminobismaleamide, polytriazine, cross-linked polyimide, epoxy resin, polysulfone, polyethersulfone, polyphenylene sulfide, polyimide and polyetheretherketone.
7. The secondary battery according to claim 1, wherein: The buffer body has a porous structure; the porosity of the buffer body is ≥30%.
8. The secondary battery according to claim 1, wherein: A one-way valve is provided at the bottom of the buffer assembly, and the diameter of the one-way valve is ≤5mm.
9. The secondary battery according to claim 1, wherein: The position of the opening end of the cavity is flush with the position of the connection between the electrode assembly and the electrode tab; The material of the liquid isolating member is polypropylene, polyethylene or polyethylene terephthalate.
10. A battery module, characterized in that: It comprises the secondary battery as claimed in any one of claims 1 to 9.