Improved current collector structure
By setting up a swelling part in the battery ear area and extruding and breaking the circuit using the principle of melt expansion, the problem that the internal short circuit current of the battery cannot be protected by the external fuse components is solved, and the overcurrent protection of the battery is achieved.
Patent Information
- Application Number
- CN202411832705.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-03-18
AI Technical Summary
In the prior art, the short-circuit current flowing through the pole ear inside the battery cannot be protected by the external fuse components, resulting in battery damage and thermal runaway.
A swelling part is provided in the pole ear region, which is located inside the pole ear region, and is used for melt expansion during overcurrent and to squeeze and open circuit.
Through the melt expansion of the swelling part, the pole ear can be squeezed, and the circuit breaking is achieved, protecting the battery from overcurrent damage.
Smart Images
Figure CN119650715A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of current collectors, and in particular to an improved current collector structure. Background Art
[0002] In secondary batteries, a current collector is needed, which is the part that converges current and is generally made of aluminum foil or copper foil. In the prior art, for safety reasons, an improved current collector structure is proposed, which includes a polymer support layer and a metal layer arranged on both sides of the support layer, which can improve the safety of subsequent batteries. Compared with metal foil current collectors, this composite structure can also reduce the weight of the current collector and improve the energy density of lithium-ion batteries.
[0003] At present, when a lithium battery has an overcurrent (which may be as high as tens of amperes) due to an external short circuit, it is generally preferred to melt the external fusing component (fuse) to protect the battery and external equipment. Summary of the invention
[0004] At present, the external fuse components cannot work for the short-circuit current flowing through the tab inside the battery, which may cause battery damage and thermal runaway.
[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide an improved current collector structure to improve the overcurrent protection function of the tab area.
[0006] The technical solution of the present invention is as follows:
[0007] The present application discloses an improved current collector structure, comprising:
[0008] A coating area, used for subsequently coating the active material on the surface of the current collector;
[0009] The tab area is used for subsequent tab welding, and the tab area is electrically connected to the coating area;
[0010] Among them, a molten expansion part is arranged in the pole ear area, and the molten expansion part is arranged correspondingly on the inner side of the pole ear area, and the projection of the molten expansion part on the surface of the film covers the area of the pole ear welding area so that when the current is over, the molten expansion part will melt and expand, push up the pole ear, and squeeze it to break the circuit.
[0011] Based on the above technical solution, a melting expansion part is provided, and the temperature in the high current pole ear area can be increased to make the melting expansion part melt. The increased volume after melting expansion squeezes the pole ear, causing the pole ear to fall off and realize circuit breaking.
[0012] Furthermore, the molten expansion portion is sealed and arranged in the pole lug area; preferably, a space for the molten expansion portion is provided in the pole lug area, and a sealing layer is further provided around the space.
[0013] Based on the above technical solution, the degree to which the expansion part exerts its expansion effect can be ensured, so that the volume expansion caused by the expansion can be more easily released at the welding point of the pole ear, and can better exert its effectiveness.
[0014] Further, the space is configured as a pore structure in a groove or a tab region communicating with the outside.
[0015] Based on the above technical solution, it is convenient to fill the expanded portion in the lug area.
[0016] Furthermore, a metal foil is provided in the tab area.
[0017] Based on the above technical solution, it is convenient to weld the tabs
[0018] Furthermore, the tab region includes a support layer of porous metal material. Preferably, the support layer material can be set as a foam metal material, and the space is set as a hole in the foam metal.
[0019] Based on the technical solution, it is suitable for the composite current collector structure; and based on the support layer of porous metal materials, it can facilitate the welding of the pole ears while increasing the conductivity.
[0020] Furthermore, the tab region includes a polymer support layer, and the melting point of the expanded portion is not higher than the melting point of the support layer.
[0021] Furthermore, a conductive layer is formed on at least one surface layer of the tab region.
[0022] Based on the above technical solution, it is convenient to improve the conductivity of the supporting layer with poor conductivity in the current collector.
[0023] Furthermore, the expansion portion is configured to be a thermoplastic polymer material.
[0024] Based on the above technical solution, melting and volume expansion can be achieved at a relatively low temperature.
[0025] Furthermore, the molten expansion portion is configured as a conductive material. Preferably, a conductive filler is filled in the thermoplastic polymer material.
[0026] Based on the above technical solution, the molten expansion part can have a current-carrying capacity. Based on the thermal effect of the current, it can melt due to the electrothermal effect within the designed safe current threshold, and the molten expansion part is heated evenly as a whole, which can increase the response speed to a certain extent.
[0027] Furthermore, an extrusion layer is provided between the melting expansion portion and the tab region; preferably, the peeling force of the extrusion layer from the tab region is smaller than the adhesion force of the tab after welding, so that the extrusion layer can be separated from the supporting layer during expansion.
[0028] Based on the above technical solution, setting an extrusion layer can further act on the pole ear. Setting an extrusion layer can increase the effective area when melting and expansion occur, and the liquid after melting in the expansion part is not easy to leak, thereby ensuring the extrusion pressure on the pole ear and realizing extrusion circuit breaking.
[0029] Furthermore, the melting point of the material of the extruded layer is higher than that of the molten expansion portion, and has a glass transition temperature (Tg) not higher than the melting point of the molten expansion portion.
[0030] Based on the above technical solution, the extrusion layer can be preferably extruded after the expansion part is melted, so that the pole ear can be better extruded. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:
[0032] Figure 1 It is a schematic diagram of the cross-sectional structure of a current collector based on metal foil / porous metal material;
[0033] Figure 2 is a schematic diagram of the cross-sectional structure of a current collector based on a composite structure;
[0034] Figure 3 A schematic diagram of the cross-sectional structure for further setting up the extrusion layer.
[0035] The horizontal direction represents the lateral direction, and the vertical direction represents the thickness direction.
[0036] In the figure:
[0037] 1- coating area; 11- supporting layer; 12- conductive layer; 2- ear area; 21- ear welding area; 22- sealing layer; 23- extrusion layer; 3- expansion part; 31- space. DETAILED DESCRIPTION
[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0039] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.
[0040] In view of the fact that the current collector in the prior art can no longer short-circuit when overcurrent occurs, refer to Figure 1 , the present application discloses an improved current collector structure, comprising:
[0041] Coating zone 1, used for subsequently coating active materials on the surface of the current collector;
[0042] The tab area 2 is used for subsequent welding of the tab; correspondingly, as an extension of the coating area 1, the tab area 2 is electrically connected to the coating area 1 and is not coated with active materials;
[0043] In some embodiments, the coating area and the tab area are set to metal foil or porous conductive material. The metal foil can be aluminum foil, copper foil, etc., and the porous conductive material can be aluminum mesh, copper mesh, foam metal (aluminum, copper, nickel, etc.); the thickness is 4-100 μm;
[0044] Among them, a molten expansion portion 3 is arranged in the pole lug area 2, and the molten expansion portion 3 is correspondingly arranged on the inner side of the pole lug area, and the projection of the molten expansion portion 3 on the surface of the pole lug area 2 is adapted to the pole lug welding area 21, so that when the current is over, the molten expansion portion will melt and expand, and the pole lug will be lifted and squeezed to break the circuit.
[0045] By providing the molten expansion part, when overcurrent occurs, the temperature of the tab area rises, causing the molten expansion part to melt, and the volume increases after the molten expansion to squeeze the tab, causing the tab to fall off and achieve circuit breaking. The above-mentioned overcurrent can be either an external short-circuit current flowing from the outside of the battery to the battery, or an internal short-circuit current flowing from the inside of the battery through the tab area to the outside.
[0046] In some embodiments of the present application, the expansion portion is configured as a thermoplastic polymer material; it can achieve melting and volume expansion at a relatively low temperature, and is easy to process and fill into the lug area, and can also increase the mechanical properties of the lug area (such as elongation at break, etc.) to a certain extent.
[0047] In some other embodiments of the present application, the expansion part 3 is set to a conductive material. Preferably, a conductive filler, such as a metal filler, a carbon-based inorganic conductive filler (graphite, graphene, carbon nanotubes, etc.), is added to the thermoplastic polymer material to improve the thermal conductivity of the expansion part and the heat transfer rate during the melting process. The expansion part can also have a current-carrying capacity. Based on the thermal effect of the current, it can be melted due to the electrothermal effect within the designed safe current threshold, and the expansion part is heated evenly as a whole, which can increase the response speed to a certain extent. The amount of conductive filler added should not be too much, which will affect the film uniformity and mechanical properties. It is generally not more than 15% of the total mass of the expansion part, preferably 3%-10%, and the appropriate amount of addition can be controlled based on the design current of the fuse, thereby controlling the resistance of the fuse part to control the response time to a certain extent.
[0048] At the same time, based on the principle of volume expansion and extrusion, the melting expansion part 3 is preferably closed and arranged in the pole ear area 2, which can ensure the degree of melting expansion of the melting expansion part 3, so that the volume expansion generated by melting expansion is easier to be released at the pole ear welding point, and can play a better role; wherein, a space 31 for the melting expansion part 3 is provided in the pole ear area 2, and a sealing layer 22 is further provided around the space 31; the sealing layer can be a filling layer filled in the pole ear area, such as a filler filled in a porous material, or a sealing layer formed by the pole ear area itself. The depth of the space 31 can be adapted to the setting in combination with the welding tension and the degree of difficulty in processing, preferably not exceeding 60% of the overall thickness of the pole ear area; and the area of the space 31 is preferably more than 1.1 times the area of the welding area, and more preferably 1.2-1.5 times, while ensuring the effective area, the molten part material overflowing after melting can also play the role of isolating the pole ear from the pole ear area 2.
[0049] like Figure 1 , the tab area 2 is set as a metal foil; illustratively, the space 31 can be formed based on local grinding or etching. At this time, the expansion part is preferably set as a conductive material, and the tab can be bonded to the conductive expansion part through a conductive adhesive, and the extension part of the tab is spot welded around the expansion part, and the spacing is preferably not more than 1 cm. When the expansion part 3 melts, the material expands and overflows, and the extrusion effect separates the tab from the welding point of the tab welding area 21. After the expansion part 3 melts, the expansion part material can also play a role in isolating the tab from the collector tab area 2.
[0050] like Figure 2 , shows a current collector based on a composite structure, which includes a support layer 11, and the space 31 can be a groove structure or a pore inside the support layer; the exemplary support layer 11 can be set as a porous metal support layer, and the melting expansion part is set in the space 31 formed in the support layer 23, and at this time, the melting expansion part is preferably able to cover the pole ear welding area 21;
[0051] A conductive layer 12 can be further formed on the surface of the molten expansion part, which is particularly suitable for the support layer material of the polymer material that is not conductive. A space 31 is formed by hot pressing in the polymer support layer corresponding to the electrode ear welding area, and the material of the molten expansion part 3 is further filled into the space. The melting point of the molten expansion part 3 is not higher than the melting point of the support layer 11, and is preferably lower than the glass transition temperature of the support layer.
[0052] More preferably, the support layer material can be set to foam metal material, and the space 31 is the hole in the foam metal; and the support layer based on the porous metal material can facilitate the welding of the pole ear while increasing the electrical conductivity and thermal conductivity, which is conducive to the heat generation and melting of the expansion part 3 area when current flows.
[0053] During preparation, a sealing filling can be arranged around the forming space 31 of the molten expansion portion 3 to obtain a closed layer 22. The above-mentioned filling can be formed based on hot pressing and compounding of polymer films of different thicknesses. The polymer film is hot pressed and compounded at a temperature above the melting point (Tm) and cooled. The hot pressing pressure is exemplarily set to 0.5-1.5MPa; and the molten expansion portion 3 is further filled in the space formed by the thickness difference. The molten expansion portion can be filled by hot pressing or casting. The relevant polymer material is an existing conventional polymer material. Preferably, the polymer material can be selected from PP and PET. For the same polymer material, the melting point can be appropriately adjusted by the degree of polymerization / molecular weight. Of course, it is also possible to pre-hot press and compound to form the molten expansion portion, and then further fill it to obtain the closed layer 22.
[0054] Reference Figure 3 , an extrusion layer 23 is arranged between the melting expansion part 3 and the tab area 2; preferably, the peeling force of the extrusion layer 23 from the tab area is less than the adhesion force after the tab is welded, so that the extrusion layer can be separated from the support layer when expanding, for example, by controlling the thickness of the extrusion layer after filling, such as not exceeding 10% of the thickness of the current collector. The extrusion layer material is selected from a polymer material, which has a higher melting point than the melting expansion part 3 and a glass transition temperature (Tg) not higher than the melting point of the melting expansion part 3, so that when the melting expansion part 3 melts, the extrusion layer 23 can soften and easily protrude from the tab area due to the extrusion effect.
[0055] The extrusion layer is provided mainly because the tabs are generally spot-welded locally, so there will be a large gap at the connection interface between the tabs and the current collector, causing pressure release, and the extrusion force on the tab welding area 21 is insufficient.
[0056] The extrusion layer 23 can be formed by controlling the filling amount of the molten expansion part 3 so that it is cast and filled in the space 31 in a molten state, so as to retain certain pores on the surface layer, and further hot-pressed and filled to form the extrusion layer 23 on the surface layer of the molten expansion part 3. The extrusion layer can increase the effective area when the molten expansion occurs, and the liquid in the molten expansion part is not easy to leak, thereby ensuring the extrusion force on the tab.
[0057] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the drawings or conventionally expressed in the prior art, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.
[0058] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.
[0059] The term "multiple" as used in the present application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).
[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. An improved current collector structure, comprising: A coating area, used for subsequently coating the active material on the surface of the current collector; The tab area is used for subsequent tab welding, and the tab area is electrically connected to the coating area; The invention is characterized in that a molten expansion portion is arranged in the pole ear area, the molten expansion portion is arranged correspondingly on the inner side of the pole ear area, and the projection of the molten expansion portion on the surface of the film covers the area of the pole ear welding area so that when the current is over, the molten expansion portion will melt and expand, thereby lifting the pole ear and squeezing it to break the circuit.
2. The improved current collector structure according to claim 1, characterized in that: The expanded portion is closed and arranged in the lug area.
3. The improved current collector structure according to claim 2, characterized in that: The tab region is provided with a space for the expansion portion, and a sealing layer is provided around the space.
4. The improved current collector structure according to claim 3, characterized in that: The space is configured as a groove communicating with the outside or a pore structure in the tab region.
5. The improved current collector structure according to claim 1, characterized in that: The lug area meets one of the following conditions: The lug area is provided with metal foil; The tab region includes a support layer of porous metal material. The tab region includes a polymer support layer, and the melting point of the expanded portion is not higher than the melting point of the support layer.
6. The improved current collector structure according to claim 5, characterized in that: A conductive layer is formed on at least one surface layer of the tab region.
7. The improved current collector structure according to any one of claims 1 to 6, characterized in that: The expansion part is configured to be a thermoplastic polymer material.
8. The improved current collector structure according to claim 7, characterized in that: The expanded portion is configured to be a conductive material and is filled with a conductive filler.
9. The improved current collector structure according to claim 8, characterized in that: An extrusion layer is arranged between the melting expansion portion and the tab area. The peeling force of the extrusion layer from the tab area is smaller than the adhesion force after the tab is welded, so that the extrusion layer can be separated from the supporting layer during expansion.
10. The improved current collector structure according to claim 9, characterized in that: The melting point of the extruded layer material is higher than that of the molten expanded portion, and has a glass transition temperature (Tg) not higher than the melting point of the molten expanded portion.