Electrode assembly and battery
By introducing a buffer component into the electrode assembly and using buffer layers with different elastic moduli to improve interface contact, the problems of wrinkles and lithium plating at the corners of the electrode assembly are solved, thereby improving the performance and safety of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- REPT BATTERO ENERGY CO LTD
- Filing Date
- 2025-04-24
- Publication Date
- 2026-04-28
AI Technical Summary
In existing technologies, wrinkles and lithium plating at the corners of electrode components are severe, especially in lithium-ion batteries with silicon-containing anode systems, leading to battery capacity degradation and safety risks.
Design an electrode assembly including a positive electrode, a negative electrode, a first diaphragm, a second diaphragm, and a buffer assembly. The buffer assembly consists of a first buffer layer and a second buffer layer. The first buffer layer is attached to the inner wall of the cavity and has a small elastic modulus. The second buffer layer provides support to improve the interface contact performance and prevent excessive expansion and displacement.
It effectively reduces wrinkles at the corners of the electrode assembly, improves lithium plating, enhances battery cycle life and safety, and ensures the integrity and consistency of the electrode assembly during processing.
Smart Images
Figure CN224177344U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of battery manufacturing technology, and in particular to an electrode assembly and a battery. Background Technology
[0002] A secondary battery (rechargeable battery) primarily functions by the movement of active ions (such as lithium ions, sodium ions, or potassium ions) between the positive and negative electrodes. Taking a lithium-ion battery as an example, during charging and discharging, Li... + It intercalates and deintercalates back and forth between the two electrodes; during charging, Li... + Lithium is extracted from the positive electrode and inserted into the negative electrode via the electrolyte, leaving the negative electrode in a lithium-rich state; the process reverses during discharge. The negative electrode material expands in volume during lithium insertion and contracts during delithiation. During battery expansion, the positive and negative electrode sheets are subjected to non-uniform mechanical stress, making them prone to localized compression or stretching, leading to wrinkling. This wrinkling can cause lithium plating on the negative electrode during cycling, resulting in abnormal capacity decay and certain safety risks.
[0003] In addition, to achieve the goal of higher energy density rechargeable batteries, taking lithium-ion batteries as an example, silicon doping of the negative electrode has become a key research and development direction. However, the lithium intercalation expansion of the silicon negative electrode itself is much greater than that of the graphite negative electrode currently in large quantities. This electrode wrinkling phenomenon caused by battery expansion is more serious in lithium-ion battery cells with silicon-containing negative electrode systems.
[0004] In existing technologies, buffer pads are often placed on the large surface of the electrode assembly to support the electrode assembly and reduce electrode deformation. This can improve the wrinkling phenomenon of the electrode assembly caused by expansion, thereby alleviating the lithium plating problem of the electrode assembly during cycling. However, for electrode assemblies, the wrinkling and lithium plating problems at the corners (R-corners) are basically not improved, and the wrinkling and lithium plating phenomena at the corners are often more serious than those at the large surface. Utility Model Content
[0005] The purpose of this invention is to provide an electrode assembly and a battery that solves the problem of lithium plating easily occurring at the corners of the electrode assembly.
[0006] To achieve the above objectives, this utility model provides an electrode assembly, which includes a positive electrode plate, a negative electrode plate, a first diaphragm, a second diaphragm, and a buffer assembly;
[0007] The first diaphragm, the negative electrode, the second diaphragm, and the positive electrode are stacked and wound along the winding direction to form an electrode assembly body; the middle part of the electrode assembly body has a cavity formed by winding and enclosing.
[0008] The buffer assembly is disposed in the cavity, and the outer peripheral surface of the buffer assembly is in contact with the inner wall surface of the cavity;
[0009] The buffer assembly includes a first buffer layer and a second buffer layer. The first buffer layer is attached to the outer periphery of the second buffer layer and is attached to the inner wall of the cavity. The elastic modulus of the first buffer layer is less than that of the second buffer layer. The second buffer layer can also be used to provide support for the first buffer layer.
[0010] Furthermore, the first buffer layer covers the outer periphery of the second buffer layer.
[0011] Furthermore, the electrode assembly body is defined to have a large, flat surface area and arc-shaped areas located on both sides of the large surface area;
[0012] The inner wall surfaces of both the large surface area and the arc area are in contact with the first buffer layer.
[0013] Furthermore, a first direction is defined on the cross-section of the electrode assembly that is parallel to the length direction of the large surface area;
[0014] In the first direction, the size of the second buffer layer is less than or equal to the size of the large area.
[0015] Furthermore, under a preset pressure of 0.8 MPa, the compressibility of the first buffer layer is 50%-90%, and the compressibility of the second buffer layer is 5%-15%.
[0016] Furthermore, the thickness of the first buffer layer corresponding to the large area is defined as d1, and the volume of the second buffer layer corresponding to the large area is defined as d2;
[0017] Where 0.2*d2≤d1≤d2, and / or:
[0018] The thickness of the electrode assembly body is defined as D1, and the thickness of the buffer assembly is defined as D2;
[0019] Among them, 3% * D1 ≤ D2 ≤ 12% * D1.
[0020] Furthermore, the first buffer layer is made of polyethylene, polypropylene, polyurethane, or silicone rubber;
[0021] The second buffer layer is made of polymethyl methacrylate, polyethylene terephthalate or polytetrafluoroethylene.
[0022] Furthermore, at least a portion of the first buffer layer has through holes and / or blind holes formed therein; the through holes and / or blind holes are used to absorb electrolyte.
[0023] Furthermore, an adhesive layer is also provided on the outer periphery of the first buffer layer;
[0024] The first buffer layer is bonded and fixed to the inner wall of the cavity by the adhesive layer.
[0025] This utility model also provides a battery, including a housing and the above-mentioned electrode assembly;
[0026] The electrode assembly is placed inside the housing.
[0027] Compared with the prior art, the electrode assembly and battery provided by this utility model have the following advantages:
[0028] This invention provides an electrode assembly comprising a positive electrode, a negative electrode, a first diaphragm, a second diaphragm, and a buffer assembly. During operation, both the positive and negative electrodes in the electrode assembly body expand. Due to the low elastic modulus of the first buffer layer, which is in contact with the inner wall of the cavity, the first buffer layer is compressed under the expansion pressure of the positive and negative electrodes towards the cavity to accommodate the expansion of the electrode assembly body towards the cavity. Furthermore, the first buffer layer remains in contact with the inner wall of the cavity during expansion, improving the interfacial contact performance at the large surfaces and corners of the electrode assembly body, thereby reducing wrinkling and improving lithium plating. The second buffer layer provides support for the first buffer layer, preventing excessive expansion and displacement of the positive and negative electrodes towards the cavity, which could lead to damage. In addition, the second buffer layer is located inside the first buffer layer, which helps to suppress the thermal shrinkage of the first buffer layer during the baking stage, so as to ensure the integrity and consistency of the buffer assembly during the production and processing.
[0029] This utility model also provides a battery, which includes a housing and the aforementioned electrode assembly. The battery is assembled by placing the electrode assembly in the housing, which facilitates subsequent use. Attached Figure Description
[0030] Figure 1 This is a cross-sectional view of an electrode assembly according to an embodiment of the present utility model;
[0031] Figure 2 This is a cross-sectional view of a battery according to an embodiment of the present invention.
[0032] In the figure, 1000 is the battery; 100 is the electrode assembly; 200 is the housing; 1 is the electrode assembly body; 10 is the cavity; 101 is the large surface area; 102 is the arc area; 11 is the negative electrode plate; 12 is the positive electrode plate; 13 is the first separator; 14 is the second separator; 2 is the buffer assembly; 21 is the first buffer layer; and 22 is the second buffer layer. Detailed Implementation
[0033] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit the scope of this utility model.
[0034] In the description of this utility model, it should be understood that the terms "positive electrode sheet," "negative electrode sheet," "first separator," and "second separator" used in this utility model all belong to the prior art in the field of battery technology, and their specific structures and "winding along the winding direction" should also belong to the prior art. In this utility model, the term "volume" refers to the volume of the first buffer layer and the second buffer layer when not subjected to external force; the term "thickness" refers to the thickness of the buffer assembly when not subjected to external force.
[0035] like Figure 1 As shown, an electrode assembly 100 according to an embodiment of the present invention includes a positive electrode 12, a negative electrode 11, a first diaphragm 13, a second diaphragm 14, and a buffer assembly 2.
[0036] The first diaphragm 13, the negative electrode 11, the second diaphragm 14, and the positive electrode 12 are stacked and wound along the winding direction to form an electrode assembly body 1; the electrode assembly body 1 has a cavity 10 formed by winding and enclosing in the middle; the buffer assembly 2 is disposed in the cavity 10, and the outer peripheral surface of the buffer assembly 2 is in contact with the inner wall surface of the cavity 10; the buffer assembly 2 includes a first buffer layer 21 and a second buffer layer 22, the first buffer layer 21 is attached to the outer periphery of the second buffer layer 22 and is in contact with the inner wall surface of the cavity 10; the elastic modulus of the first buffer layer 21 is less than the elastic modulus of the second buffer layer 22; the second buffer layer 22 can also be used to provide support for the first buffer layer 21.
[0037] Based on the above technical solution, during the operation of the electrode assembly 100, both the positive electrode 12 and the negative electrode 11 in the electrode assembly body 1 expand. Since the first buffer layer 21, which is in contact with the inner wall of the cavity 10, has a relatively small elastic modulus, it will be compressed to accommodate the expansion of the electrode assembly body 1 towards the cavity 10 as the positive electrode 12 and negative electrode 11 expand towards the cavity 10. Furthermore, the first buffer layer 21 remains in contact with the inner wall of the cavity 10 during the expansion of the positive electrode 12 and negative electrode 11, thereby improving the interface contact performance at the large surfaces and corners of the electrode assembly body 1, reducing wrinkling, and thus improving the lithium plating problem of the electrode assembly body 1. The second buffer layer 22 provides support for the first buffer layer 21, preventing damage caused by excessive expansion and displacement of the positive electrode 12 and negative electrode 11 when expanding towards the cavity 10. In addition, the second buffer layer 22 is disposed inside the first buffer layer 21, which helps to suppress the thermal shrinkage of the first buffer layer 21 during the baking stage of the electrode assembly, so as to ensure the integrity and consistency of the buffer assembly 2 in the production and processing process.
[0038] Furthermore, such as Figure 1 As shown, the first buffer layer 21 covers the outer periphery of the second buffer layer 22, which enables the second buffer layer 22 to provide strong support for all parts of the first buffer layer 21.
[0039] Furthermore, such as Figure 1 As shown, the electrode assembly body 1 is defined to have a large, flat surface area 101 and arc-shaped areas 102 located on both sides of the large surface area 101; the inner wall surfaces of the large surface area 101 and the arc-shaped areas 102 are both in contact with the first buffer layer 21; so as to ensure that the first buffer layer 21 can improve the problems caused by the expansion of the large surface area 101 and the arc-shaped areas 102.
[0040] Furthermore, such as Figure 1 As shown, a first direction X is defined on the cross-section of the electrode assembly 100, parallel to the length direction of the large surface area 101; in the first direction X, the size of the second buffer layer 22 is less than or equal to the size of the large surface area 101; this arrangement facilitates that the portion of the first buffer layer 21 that is in contact with the inner wall surface of the arc area 102 has a larger thickness, so as to fully accommodate the displacement of the arc area 102 when it expands toward the cavity 10, thereby enhancing the improvement effect of the interface contact performance of the arc area 102 and further reducing the occurrence of wrinkles and lithium plating problems at the corner (R corner).
[0041] In this embodiment, the size of the second buffer layer 22 in the first direction X is equal to the size of the large area 101. In other embodiments, the size of the second buffer layer 22 is smaller than the size of the large area 101.
[0042] Furthermore, such as Figure 1 As shown, under a preset pressure of 0.8 MPa, the compressibility of the first buffer layer 21 is 50%-90%; this allows the first buffer layer 21 to adapt to the expansion of the positive electrode 12 and the negative electrode 11, and to contract under pressure, ensuring contact and fit with the electrode assembly body 1. The compressibility of the second buffer layer 22 is 5%-15%; it provides stable support for the first buffer layer 21 to limit the deformation of the positive electrode 12 and the negative electrode 11, thereby reducing the risk of wrinkling and damage; and preventing the positive electrode 12 and the negative electrode 11 from excessive expansion and displacement, which could lead to irreversible damage.
[0043] Preferably, such as Figure 1 As shown, to ensure that the second buffer layer 22 has sufficient supporting force, the compressibility of the second buffer layer 22 is preferably 5%-10%; similarly, to ensure that the first buffer layer 21 can fully adapt to the expansion of the positive electrode 12 and the negative electrode 11, the compressibility of the first buffer layer 21 is preferably 50%-90%. In this embodiment, under a preset pressure of 0.8 MPa, the compressibility of the first buffer layer 21 is set to 80%, and the compressibility of the second buffer layer 22 is set to 5%.
[0044] Furthermore, the thickness of the first buffer layer 21 corresponding to the large area is defined as d1, and the thickness of the second buffer layer 22 corresponding to the large area is defined as d2; wherein, 0.2d2≤d1≤d2.
[0045] It should be noted that, as Figure 1 As shown, the thickness of the first buffer layer 21 corresponding to the large area in this application refers to the thickness of the first buffer layer 21 in... Figure 1 The dimension in the Y direction; the thickness of the second buffer layer 22 corresponding to the large area in this application refers to the thickness of the second buffer layer 22 in the Y direction; Figure 1 The dimension in the Y direction.
[0046] It is understood that the second buffer layer 22 has a first buffer layer 21 on each side in the Y direction. Therefore, d1 referred to in this application is actually the sum of the thicknesses of the two first buffer layers 21.
[0047] The thickness of the first buffer layer 21 needs to be limited to a suitable range. If the thickness d1 of the first buffer layer 21 is less than 0.2d2, that is, the thickness of the first buffer layer 21 is relatively small, it cannot fully absorb the expansion pressure from the positive electrode 12 and the negative electrode 11, which can easily cause the first buffer layer 21 to separate from the electrode assembly body 1, thereby causing the positive electrode 12 and the negative electrode 11 to wrinkle, and then lithium plating. If the thickness d1 of the first buffer layer 21 is greater than the thickness of the second buffer layer 22, then the thickness of the first buffer layer 21 is large. Since the support capacity of the first buffer layer 21 is small, an excessively thick first buffer layer 21 can easily cause the positive electrode 12 and the negative electrode 11 to over-expand and displace toward the cavity 10 during operation, thereby causing irreversible damage to the positive electrode 12 and the negative electrode 11.
[0048] Furthermore, such as Figure 1 As shown, in order to ensure the energy density of the battery and prevent the buffer component 2 from occupying too much space while playing a role in improving lithium plating, the overall thickness of the electrode component body 1 is defined as D1, and the thickness of the buffer component 2 is defined as D2; wherein, 3%*D1≤D2≤12%*D1.
[0049] It is understandable that the overall thickness of the electrode assembly body 1 refers to the dimension of the electrode assembly body 1 in the Y direction, and the thickness of the buffer assembly 2 refers to the dimension of the buffer assembly 2 in the Y direction.
[0050] Preferably, such as Figure 1 As shown, to balance the improving effect of the buffer component 2 and the energy density of the battery, the preferred thickness is 7% * D1 ≤ D2 ≤ 12% * D1, to ensure that the buffer component 2 has sufficient thickness to improve lithium plating. In this embodiment, the thickness relationship between the electrode assembly body 1 and the buffer component 2 is set as: 7% * D1 = D2.
[0051] Furthermore, the first buffer layer 21 is made of polyethylene, polypropylene, polyurethane, or silicone rubber; polyethylene, polypropylene, polyurethane, and silicone rubber all have high flexibility and compressibility, which can fully absorb the stress of the electrode assembly body 1 during expansion or contraction, thereby reducing damage to the positive electrode 12 and the negative electrode 11; the second buffer layer 22 is made of polymethyl methacrylate, polyethylene terephthalate, or polytetrafluoroethylene; polymethyl methacrylate, polyethylene terephthalate, and polytetrafluoroethylene have high mechanical strength and stiffness, which can provide stable support for the first buffer layer 21 and prevent the positive electrode 12 and the negative electrode 11 from excessive expansion and displacement. In this embodiment, the first buffer layer 21 is made of silicone rubber, and the second buffer layer 22 is made of polymethyl methacrylate.
[0052] Furthermore, such as Figure 1 As shown, at least a portion of the first buffer layer 21 has through holes and / or blind holes; the through holes and / or blind holes are used to absorb electrolyte to serve as a temporary storage space for electrolyte in the electrode assembly 100; when the electrode assembly body 1 expands inward, the electrolyte in the through holes and / or blind holes is squeezed outward, thereby ensuring an abundance of electrolyte in the electrode assembly 100 and thus improving the cycle life of the battery.
[0053] Furthermore, such as Figure 1 As shown, an adhesive layer (not shown in the figure) is also provided on the outer periphery of the first buffer layer 21; the first buffer layer 21 is bonded and fixed to the inner wall of the cavity 10 through the adhesive layer; thus, the positive electrode 12, negative electrode 11, first diaphragm 13 and second diaphragm 14 in the electrode assembly body 1 can remain relatively fixed during expansion and contraction, and will not undergo significant displacement or sliding that would lead to damage to the electrode assembly body 1. The thickness of the adhesive layer is 0.5 to 3 μm to ensure sufficient bonding and fixation.
[0054] Preferably, the thickness of the adhesive layer is 0.5–1 μm to avoid excessive thickness, which could affect the heat dissipation of the positive electrode 12 and the negative electrode 11, and may prevent the expansion pressure of the positive electrode 12 and the negative electrode 11 from being fully transferred to the first buffer layer 21. In this embodiment, the adhesive layer melts during the hot pressing process and then bonds and fixes itself to the diaphragm located on the innermost side of the electrode assembly body 1, thus achieving positioning and fixation. In this embodiment, the thickness of the adhesive layer is set to 1 μm.
[0055] Furthermore, the adhesive layer is made of polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, acrylic acid copolymer, polyacrylonitrile, or aramid fiber to obtain good adhesive properties. In this embodiment, polyvinylidene fluoride is selected to make the adhesive layer.
[0056] Preferably, the first buffer layer 21 and the second buffer layer 22 are integrally molded, and the first buffer layer and the second buffer layer are integrally connected without an adhesive layer. By preparing adhesive solutions of different compositions, the adhesive solutions are sequentially applied to the substrate by coating, irradiated under ultraviolet light with a wavelength of 200-280 nm for 30-60 minutes, and then baked at 100-150°C for 3-15 minutes. After processes such as slitting and cutting, the integral first buffer layer and the second buffer layer are obtained.
[0057] like Figure 2 As shown, the present invention also provides a battery 1000, which includes a housing 200 and the aforementioned electrode assembly 100; the electrode assembly 100 is placed in the housing 200.
[0058] Based on the above technical solution, the battery 1000 is assembled by placing the electrode assembly 100 in the housing 200, which facilitates subsequent use.
[0059] Preferably, in this embodiment, the two electrode assemblies 100 are placed in the housing 200 to increase the total energy capacity of the battery 1000 and effectively utilize the internal space of the housing 200 to meet the requirements of high energy density.
[0060] The working process of this utility model is as follows: When the electrode assembly 100 in the battery 1000 is working, the positive electrode 12 and the negative electrode 11 expand, causing the electrode assembly body 1 to expand inward. The first buffer layer 21 is compressed under the pressure of the inward expansion, and the outer peripheral surface of the first buffer layer 21 always remains in contact with the inner wall surface of the cavity 10. The second buffer layer 22 located inside the first buffer layer 21 provides support for the first buffer layer 21, preventing the positive electrode 12 and the negative electrode 11 from excessively expanding and displacing.
[0061] In summary, this utility model embodiment provides an electrode assembly 100, which includes a positive electrode 12, a negative electrode 11, a first separator 13, a second separator 14, and a buffer assembly 2. During the operation of the electrode assembly 100, both the positive electrode 12 and the negative electrode 11 in the electrode assembly body 1 expand. Due to the small elastic modulus of the first buffer layer 21, which is in contact with the inner wall of the cavity 10, the first buffer layer 21 will be compressed to accommodate the expansion of the electrode assembly body 1 towards the cavity 10 under the expansion action of the positive electrode 12 and the negative electrode 11 towards the cavity 10. Furthermore, the first buffer layer 21 remains in contact with the inner wall of the cavity 10 when the positive electrode 12 and the negative electrode 11 expand, thereby improving the interface contact performance at the large surface and corners of the electrode assembly body 1, reducing the occurrence of wrinkles, and thus improving the lithium plating problem of the electrode assembly body 1. The second buffer layer 22 provides support for the first buffer layer 21, preventing damage caused by excessive expansion and displacement of the positive electrode 12 and negative electrode 11 when they expand toward the cavity 10. Furthermore, the second buffer layer 22 is located inside the first buffer layer 21, which helps to suppress thermal shrinkage of the first buffer layer 21 during the baking stage of the electrode assembly, thus ensuring the integrity and consistency of the buffer assembly 2 during the manufacturing process.
[0062] This utility model also provides a battery 1000, which includes a housing 200 and the aforementioned electrode assembly 100; by placing the electrode assembly 100 in the housing 200, the battery 1000 is assembled and formed, which facilitates subsequent use.
[0063] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.
Claims
1. An electrode assembly, characterized in that, It includes a positive electrode, a negative electrode, a first diaphragm, a second diaphragm, and a buffer assembly; The first diaphragm, the negative electrode, the second diaphragm, and the positive electrode are stacked and wound along the winding direction to form an electrode assembly body; the middle part of the electrode assembly body has a cavity formed by winding and enclosing. The buffer assembly is disposed in the cavity, and the outer peripheral surface of the buffer assembly is in contact with the inner wall surface of the cavity; The buffer assembly includes a first buffer layer and a second buffer layer. The first buffer layer is attached to the outer periphery of the second buffer layer and is attached to the inner wall of the cavity. The elastic modulus of the first buffer layer is less than that of the second buffer layer. The second buffer layer can also be used to provide support for the first buffer layer.
2. The electrode assembly as described in claim 1, characterized in that, The first buffer layer covers the outer periphery of the second buffer layer.
3. The electrode assembly as described in claim 2, characterized in that, The electrode assembly body is defined to have a large, flat surface area and arc-shaped areas located on both sides of the large surface area; The inner wall surfaces of both the large surface area and the arc area are in contact with the first buffer layer.
4. The electrode assembly as described in claim 3, characterized in that, Defined on the cross-section of the electrode assembly, having a first direction parallel to the length direction of the large surface area; In the first direction, the size of the second buffer layer is less than or equal to the size of the large area.
5. The electrode assembly as claimed in claim 1, characterized in that, Under a preset pressure of 0.8 MPa, the compressibility of the first buffer layer is 50%-90%, and the compressibility of the second buffer layer is 5%-15%.
6. The electrode assembly as described in claim 3, characterized in that, The thickness of the first buffer layer corresponding to the large area is defined as d1, and the volume of the second buffer layer corresponding to the large area is defined as d2. Where 0.2*d2≤d1≤d2, and / or: The thickness of the electrode assembly body is defined as D1, and the thickness of the buffer assembly is defined as D2; Among them, 3% * D1 ≤ D2 ≤ 12% * D1.
7. The electrode assembly as claimed in claim 1, characterized in that, The first buffer layer is made of polyethylene, polypropylene, polyurethane or silicone rubber; The second buffer layer is made of polymethyl methacrylate, polyethylene terephthalate or polytetrafluoroethylene.
8. The electrode assembly as claimed in claim 1, characterized in that, The first buffer layer has at least a portion of through holes and / or blind holes formed therein; the through holes and / or blind holes are used to absorb electrolyte.
9. The electrode assembly as claimed in claim 1, characterized in that, The outer periphery of the first buffer layer is also provided with an adhesive layer; The first buffer layer is bonded and fixed to the inner wall of the cavity by the adhesive layer.
10. A battery, characterized in that, Includes a housing and an electrode assembly as described in any one of claims 1 to 9; The electrode assembly is placed inside the housing.