Battery cell and battery pack

Abstract

The application discloses an electric core and a battery pack, and belongs to the technical field of batteries. The electric core comprises an electrode group, a phase change layer, a buffer layer and a shell. The electrode group is accommodated in the shell. The phase change layer is arranged between the shell and the electrode group. The buffer layer is arranged between the phase change layer and the electrode group. The phase change layer has high thermal conductivity, can quickly spread and conduct the heat generated by the electrode group to the outside of the shell, and has phase change latent heat which can absorb a large amount of heat when the temperature reaches a phase change point, thereby improving the heat transfer and charging performance of a high-rate fast-charging battery. The buffer layer can effectively absorb and buffer the volume change of the electrode group in the charging and discharging cycle, thereby helping to maintain the structural stability and prolong the cycle life.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell and battery pack. Background Technology

[0002] As a core component of new energy electric vehicles, lithium-ion power batteries directly affect the vehicle's range and fast-charging capabilities. With the market's increasing demands for charging speed, high-rate fast-charging technology has become an important development direction for the industry.

[0003] The bottom cooling solution used in mainstream battery cells is difficult to effectively dissipate the large amount of heat generated instantaneously inside the electrode assembly during fast charging. This not only reduces charging efficiency but also limits the duration of high-rate fast charging. Utility Model Content

[0004] This application provides a battery cell and battery pack to solve the problem of insufficient heat dissipation capacity of the battery cell.

[0005] To achieve the above objectives, according to a first aspect of this application, a battery cell is provided, the battery cell comprising an electrode assembly, a phase change layer, a buffer layer, and a housing; The electrode assembly is housed within the housing; The phase change layer is disposed between the housing and the electrode assembly; The buffer layer is disposed between the phase change layer and the electrode assembly.

[0006] Optionally, the phase change layer is attached to at least a portion of the inner wall of the housing; the buffer layer is in contact with the surface of the phase change layer and the surface of the electrode assembly, respectively.

[0007] Optionally, the phase change layer includes a first part and a second part; the buffer layer is disposed between the first part and the electrode group, and the second part is in contact with the surface of the electrode group.

[0008] Optionally, the area of ​​the first part is larger than the area of ​​the second part.

[0009] Optionally, the thickness of the first part is less than or equal to the thickness of the second part.

[0010] Optionally, the thickness of the phase change layer is 0.3 mm to 2.0 mm.

[0011] Optionally, the thickness of the buffer layer is 0.5 mm to 2 mm.

[0012] Optionally, the phase change layer includes a functional body and an encapsulation layer; the functional body comprises a graphene-paraffin composite phase change material; the encapsulation layer covers the functional body and includes a polyolefin layer.

[0013] Optionally, the buffer layer has an elastic porous structure, and the material of the buffer layer includes at least one of fluororubber, hydrogenated nitrile rubber, perfluoroether rubber, and fluorosilicone rubber.

[0014] Optionally, the battery cell further includes an electrolyte that is immersed in the buffer layer and flows out of the buffer layer when the buffer layer is compressed.

[0015] According to a second aspect of this application, a battery pack is provided, the battery pack including at least one cell as described in the first aspect of this application.

[0016] The battery cell provided in the first aspect of this application has a phase change layer with high thermal conductivity, which can quickly diffuse and conduct the heat generated by the electrode assembly to the outside of the casing. At the same time, its latent heat of phase change can absorb a large amount of heat when the temperature reaches the phase change point, improving the heat transfer and charging performance of the high-rate fast charging battery. The buffer layer can effectively absorb and buffer the volume change of the electrode assembly during charge and discharge cycles, which helps to maintain structural stability and extend cycle life.

[0017] The battery pack provided in the first aspect of this application includes the aforementioned battery cells, and therefore the battery pack necessarily inherits all the beneficial effects of the battery cells, which will not be elaborated here.

[0018] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0021] Figure 1 This is a schematic diagram of the overall structure of the battery cell provided in an exemplary embodiment of this disclosure; Figure 2 This is a partial structural diagram of a battery cell provided in an exemplary embodiment of this disclosure; Figure 3 This is a front view of a battery cell provided in an exemplary embodiment of this disclosure; Figure 4 yes Figure 3 The cross-sectional view at point A in the figure shows an arrangement of a phase change layer and a buffer layer. Figure 5yes Figure 3 Another cross-sectional view at point A shows another arrangement of the phase change layer and buffer layer.

[0022] Explanation of reference numerals in the attached figures: 1. Electrode assembly; 2. Phase change layer; 21. First part; 22. Second part; 3. Buffer layer; 4. Shell; 5. Cover. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0024] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0027] As a core component of new energy electric vehicles, lithium-ion power batteries directly affect the vehicle's range and fast-charging capabilities. With the market's increasing demands for charging speed, high-rate fast-charging technology has become an important development direction for the industry.

[0028] To achieve fast charging, the battery needs to withstand extremely high current for a short period of time, which leads to a surge in heat generation. The bottom cooling solution used in mainstream battery cells is difficult to effectively dissipate the large amount of heat generated instantaneously inside the electrode assembly during fast charging. This not only reduces charging efficiency but also limits the duration of high-rate fast charging.

[0029] During the charging and discharging process of lithium-ion batteries, the electrode active materials undergo periodic volume changes due to the insertion and extraction of lithium ions; this reversible expansion / contraction is known as the "breathing effect." Furthermore, under conditions such as overcharging and high temperatures, internal side reactions can generate gas, leading to irreversible gas formation and bulging. Common battery modules lack effective stress buffering and release mechanisms, severely limiting the cycle life and safety of the cells.

[0030] Firstly, this application provides a battery cell, please refer to [link to relevant documentation]. Figures 1 to 3 ,in, Figure 2 This illustrates one combination of electrode assembly 1, phase change layer 2, and buffer layer 3.

[0031] The battery cell includes an electrode assembly 1, a phase change layer 2, a buffer layer 3, and a housing 4. The electrode assembly 1 is housed within the housing 4. The phase change layer 2 is disposed between the housing 4 and the electrode assembly 1. The buffer layer 3 is disposed between the phase change layer 2 and the electrode assembly 1. The phase change layer 2 has high thermal conductivity, which can quickly diffuse and conduct the heat generated by the electrode assembly 1 to the outside of the housing 4. At the same time, its latent heat of phase change can absorb a large amount of heat when the temperature reaches the phase change point, improving the heat transfer and charging performance of the high-rate fast-charging battery. The buffer layer 3 can effectively absorb and buffer the volume change of the electrode assembly 1 during charge and discharge cycles, which helps to maintain structural stability and extend cycle life.

[0032] In some embodiments, the phase change layer 2 is attached to at least a portion of the inner wall of the housing 4; the buffer layer 3 is in contact with the surface of the phase change layer 2 and the surface of the electrode assembly 1, respectively. That is, the electrode assembly 1, the buffer layer 3, the phase change layer 2, and the housing 4 are sequentially attached. The heat generated by the electrode assembly 1 can be quickly transferred to the phase change layer 2 through the buffer layer 3, and further effectively dissipated through the housing 4, thereby improving the overall heat dissipation efficiency. At the same time, the direct contact between the buffer layer 3 and the surface of the electrode assembly 1 allows it to respond promptly to and absorb the volume expansion of the electrode assembly 1 during the charging and discharging process, effectively buffering internal stress.

[0033] In some examples, the phase change layer 2 completely covers the sidewall of the housing 4. This form of the sidewall completely covering the phase change layer 2 can form a complete and uniform heat dissipation path in the circumferential direction of the cell, which is conducive to promoting the rapid conduction and equalization of heat in the electrode assembly 1.

[0034] Please see Figure 4 Taking a square-shell battery cell as an example, the cross-section of the casing 4 of the square-shell battery cell is rectangular, and the phase change layer 2 is fully covered on the sidewalls. Specifically, the phase change layer 2 completely covers the sidewalls of the casing 4.

[0035] In other examples, the phase change layer 2 is attached to part of the sidewall of the housing 4. This form of partial coverage of the phase change layer 2 on the sidewall provides flexibility in arrangement, and optimizes material cost and space utilization while ensuring the core heat dissipation effect.

[0036] Please see Figure 5 Taking a square-shell battery cell as an example, the form of the phase change layer 2 covering the side wall can be expressed as the phase change layer 2 completely covering the long side wall of the shell 4, while the phase change layer 2 is not provided on the short side wall of the shell 4.

[0037] In some embodiments, the phase change layer 2 includes a first portion 21 and a second portion 22; a buffer layer 3 is disposed between the first portion 21 and the electrode assembly 1, and the second portion 22 is in contact with the surface of the electrode assembly 1. The second portion 22 is in direct contact with the surface of the electrode assembly 1, establishing a low thermal resistance heat transfer path, which is conducive to rapid heat dissipation; while the first portion 21 is indirectly in contact with the electrode assembly 1 through the buffer layer 3, which, while ensuring basic thermal conductivity, also takes into account the buffering effect of expansion in this area.

[0038] Optionally, the area of ​​the first part 21 is larger than the area of ​​the second part 22. The larger area of ​​the first part 21 means that the buffer layer 3 can cover and protect a relatively wide area of ​​the electrode assembly 1, thereby more effectively dealing with the expansion stress generated by the electrode assembly 1 during charging and discharging.

[0039] In some examples, please refer to Figure 4When the phase change layer 2 completely covers the side wall of the housing 4, taking a square-shell battery cell as an example, the first part 21 completely covers the long side wall of the housing 4, and the buffer layer 3 is disposed between the first part 21 and the electrode group 1; the second part 22 completely covers the short side wall of the housing 4.

[0040] In other examples, please refer to Figure 5 When the phase change layer 2 is attached to part of the side wall of the housing 4, the first part 21 completely covers the long side wall of the housing 4, and the buffer layer 3 is disposed between the first part 21 and the electrode group 1. At this time, the second part 22 is not disposed, that is, the short side wall of the housing 4 is in contact with the electrode group 1.

[0041] In some other examples, when the phase change layer 2 is attached to part of the sidewall of the housing 4, the first part 21 and the second part 22 together cover the long sidewall of the housing 4, the buffer layer 3 is disposed between the first part 21 and the electrode group 1, and the short sidewall of the housing 4 is in contact with the electrode group 1.

[0042] It is understandable that Part 21 and Part 22 can also be expressed in other combinations, and are not limited to the three examples mentioned above.

[0043] Optionally, the thickness of the first part 21 is less than or equal to the thickness of the second part 22. This thickness setting keeps the first part 21, which overlaps with the buffer layer 3, relatively thin, effectively saving radial space; while the second part 22, which is in direct contact with the electrode assembly 1, adopts a relatively larger thickness, increasing the mass of the phase change material in this region, thereby improving the heat capacity and latent heat storage capacity.

[0044] In some embodiments, the phase change layer 2 includes a functional body and an encapsulation layer; the functional body comprises a graphene-paraffin composite phase change material; the encapsulation layer covers the functional body. Graphene enhances the thermal conductivity of the paraffin phase change material, enabling it to conduct heat rapidly. Furthermore, graphene exerts a strong capillary binding force on the paraffin phase change material, further preventing leakage. Paraffin absorbs and stores a large amount of heat energy through the phase change process, jointly improving the overall efficiency of heat transfer and temperature limiting. The encapsulation layer, by completely encapsulating the functional body, effectively prevents leakage and deformation of the phase change material, ensuring the reliability of the material for long-term use.

[0045] In some examples, the encapsulation layer is made of polyolefin materials, such as modified polypropylene and cast polypropylene, which effectively prevent leakage of the internal phase change material. Simultaneously, the polyolefin material exhibits good chemical compatibility with the electrolyte, ensuring its long-term stability in the electrolyte environment. Furthermore, the material possesses moderate elastic deformation capability, with a compressibility of approximately 20%, allowing it to adapt to changes in internal cell volume and assembly tolerances to a certain extent.

[0046] The phase change layer 2 can be fixedly connected to the inner wall of the housing 4 using an electrolyte-resistant adhesive. The adhesive can be selected from one of the following: pressure-sensitive adhesive, thermosetting adhesive, or UV-curing adhesive.

[0047] The functional body can be obtained using known phase change material preparation methods, as long as the composite of graphene and paraffin materials can be achieved. In one specific embodiment, the preparation method of the functional body includes: mixing molten paraffin with a graphene dispersion, emulsifying it under high-speed shear to form an emulsion, and then obtaining shaped phase change microspheres with a particle size of 10 μm to 100 μm through in-situ encapsulation, curing, and post-processing. In another embodiment, graphene nanosheets can also be used as a framework, and paraffin phase change material can be loaded onto the graphene nanosheets by melt impregnation to form a composite structure. In all embodiments, the functional body is encapsulated and protected by an encapsulation layer to ensure its structural integrity.

[0048] The thickness of the phase change layer 2 is 0.3mm to 2.0mm. By setting the thickness of the phase change layer 2 to 0.3mm to 2.0mm, effective phase change heat storage capacity can be provided in a limited space, ensuring that it has sufficient heat capacity to absorb heat during the charging and discharging process, while maintaining low thermal resistance and ensuring the efficiency of heat conduction to the shell 4.

[0049] Specifically, the thickness of the phase change layer 2 is any one or any two of the following values: 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, and 2.0 mm.

[0050] In some examples, the thickness of the functional body is 0.25 mm to 1.99 mm.

[0051] In some embodiments, the buffer layer 3 has an elastic porous structure, and the material of the buffer layer 3 includes at least one of fluororubber, hydrogenated nitrile rubber, perfluoroether rubber, and fluorosilicone rubber. The elastic properties of the buffer layer 3 enable it to effectively absorb and release the mechanical stress generated by the volume change of the electrode assembly 1 during charging and discharging through its own deformation; its porous structure can adsorb and store electrolyte, establishing a temporary electrolyte reservoir inside the battery cell, and releasing or absorbing electrolyte as needed according to operating conditions, which helps to improve the uniformity of electrolyte wetting.

[0052] The battery cell also includes an electrolyte, which is embedded in a buffer layer 3 and flows out when the buffer layer 3 is compressed. When the battery cell expands during charging and discharging, the buffer layer 3, when compressed, can release the electrolyte stored inside to the interface of the electrode assembly 1, promptly replenishing the local electrolyte loss caused by volume changes and effectively improving the uniformity of electrode wetting. When the stress decreases, the buffer layer 3 can reabsorb the electrolyte, forming a dynamic equilibrium.

[0053] The thickness of the buffer layer 3 ranges from 0.5 mm to 2 mm. Setting the thickness of the buffer layer 3 to 0.5 mm to 2 mm provides sufficient elastic deformation space to fully absorb and buffer the cyclic expansion stress of the electrode assembly 1.

[0054] Specifically, the thickness of the buffer layer 3 is any one or any two of the following: 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, and 2.0mm.

[0055] In some embodiments, please refer to Figure 3 The battery cell also includes a cover 5, which works with the housing 4 to form a relatively enclosed space.

[0056] The housing 4 is an aluminum alloy box with an opening at the top; the cover 5 is placed over the opening of the housing 4.

[0057] In some embodiments, electrode assembly 1 includes a winding core.

[0058] Secondly, embodiments of this application also provide a battery pack, which includes at least one battery cell provided in the first aspect of this application. Since it includes a battery cell with the synergistic effect of the phase change layer 2 and the buffer layer 3, this battery pack necessarily inherits all the beneficial effects of the battery cell provided in the first aspect of this application in terms of thermal management, expansion buffering, and extended cycle life, which will not be elaborated further here.

[0059] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0060] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0061] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0062] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly (1), a phase change layer (2), a buffer layer (3), and a housing (4). The electrode assembly (1) is housed within the housing (4); The phase change layer (2) is disposed between the housing (4) and the electrode group (1); The buffer layer (3) is disposed between the phase change layer (2) and the electrode group (1).

2. The battery cell according to claim 1, characterized in that, The phase change layer (2) is attached to at least part of the inner wall of the housing (4); the buffer layer (3) is in contact with the surface of the phase change layer (2) and the surface of the electrode assembly (1).

3. The battery cell according to claim 1, characterized in that, The phase change layer (2) includes a first part (21) and a second part (22); the buffer layer (3) is disposed between the first part (21) and the electrode group (1), and the second part (22) is in contact with the surface of the electrode group (1).

4. The battery cell according to claim 3, characterized in that, The area of ​​the first part (21) is greater than the area of ​​the second part (22).

5. The battery cell according to claim 3, characterized in that, The thickness of the first part (21) is less than or equal to the thickness of the second part (22).

6. The battery cell according to claim 1, characterized in that, The thickness of the phase change layer (2) is 0.3 mm to 2.0 mm; and / or, The thickness of the buffer layer (3) is 0.5 mm to 2 mm.

7. The battery cell according to claim 1, characterized in that, The phase change layer (2) includes a functional body and an encapsulation layer; the functional body contains a graphene-paraffin composite phase change material; the encapsulation layer covers the functional body and includes a polyolefin layer.

8. The battery cell according to claim 1, characterized in that, The buffer layer (3) has an elastic porous structure, and the material of the buffer layer (3) includes at least one of fluororubber, hydrogenated nitrile rubber, perfluoroether rubber, and fluorosilicone rubber.

9. The battery cell according to claim 1, characterized in that, The battery cell also includes an electrolyte that is immersed in the buffer layer (3) and flows out of the buffer layer (3) when the buffer layer (3) is squeezed.

10. A battery pack, characterized in that, The battery pack includes at least one cell as described in any one of claims 1 to 9.

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