A current collector, a cathode sheet, and a battery

Abstract

This invention provides a current collector, a cathode sheet, and a battery, comprising: a first foil layer, a second foil layer, and a third foil layer; the elongation coefficient of the second foil layer is greater than that of the first foil layer and the third foil layer; the second foil layer is wavy along a first direction, which is the length extension direction of the current collector; the second foil layer has a first wavy surface and a second wavy surface opposite to each other along a second direction, which is the thickness direction of the second foil layer; the first foil layer is fixedly disposed on the first wavy surface, and the third foil layer is disposed on the second wavy surface. The current collector of this invention can effectively prevent complete breakage of the current collector.

Description

Technical Field

[0001] This utility model relates to the field of new energy technology, and in particular to a current collector, a cathode sheet and a battery. Background Technology

[0002] Currently, with the increasing market demand for consumer batteries, battery active materials have shifted from traditional graphite to silicon. Silicon's high specific capacity can significantly increase cell capacity, but its expansion (>300%) places higher demands on the overall cell reliability. In the current collector, failure to withstand the large expansion of silicon can lead to breakage. After current collector breakage, an open circuit occurs, greatly reducing battery performance and even causing battery damage. Therefore, a new current collector is needed to effectively prevent complete breakage. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a current collector that can effectively prevent complete breakage of the current collector.

[0004] This utility model also proposes a cathode plate.

[0005] This utility model also proposes a battery.

[0006] According to a first aspect of the present invention, a current collector includes: a first foil layer, a second foil layer, and a third foil layer; the elongation coefficient of the second foil layer is greater than the elongation coefficients of the first foil layer and the third foil layer; the second foil layer is wavy along a first direction, the first direction being the length extension direction of the current collector; the second foil layer has a first wavy surface and a second wavy surface opposite to each other along a second direction, the second direction being the thickness direction of the second foil layer; the first foil layer is fixedly disposed on the first wavy surface, and the third foil layer is disposed on the second wavy surface.

[0007] The current collector according to the first aspect of this utility model has at least the following beneficial effects: During the charging and discharging process of the battery, expansion and contraction occur, resulting in a stretching effect on the current collector. Initially, the first and third foil layers are subjected to tensile force. After the first and third foil layers break due to the large tensile force, the corrugated second foil layer deforms and straightens. At this time, due to the deformation of the second foil layer, the tensile force on the second foil layer is greatly reduced. This effectively prevents the current collector from completely breaking.

[0008] According to some embodiments of the present invention, the tensile strength of the first foil layer and the third foil layer is greater than the tensile strength of the second foil layer.

[0009] According to some embodiments of the present invention, a third wavy surface is provided on the side of the first foil layer facing the second foil layer, and the third wavy surface is attached and fixed to the first wavy surface.

[0010] According to some embodiments of the present invention, the third foil layer has a fourth wavy surface on the side facing the second foil layer, and the fourth wavy surface is attached and fixed to the second wavy surface.

[0011] According to some embodiments of the present invention, the crest of the first wave surface is fixedly connected to the first foil layer, and the crest of the second wave surface is fixedly connected to the third foil layer.

[0012] According to some embodiments of the present invention, the crest of the first wave surface is provided with a first connecting plane, and the first connecting plane is fixedly connected to the first foil layer; and / or, the crest of the second wave surface is provided with a second connecting plane, and the second connecting plane is fixedly connected to the third foil layer.

[0013] According to some embodiments of the present invention, the thickness of the second foil layer is E, and the distance between the crest and trough of the first wave surface in the second direction is C, where 0.1E≤C≤0.2E.

[0014] According to some embodiments of the present invention, the width of the first connecting plane in the first direction is B, the interval between adjacent wave crests on the first wave surface is A, and the distance between the wave crest and wave trough of the first wave surface in the second direction is C, where C≤1 / 2A≤B.

[0015] According to some embodiments of the present invention, the thickness of the first foil layer and the third foil layer is D, the thickness of the second foil layer is E, and 1 / 4E≤D≤1 / 2E.

[0016] The cathode sheet according to a second aspect of the present invention includes the current collector as described in any of the above embodiments.

[0017] The battery according to a third aspect of the present invention includes the battery described in the above embodiments.

[0018] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the current collector structure of this utility model;

[0020] Figure 2This is a schematic diagram of the exploded structure of the current collector of this utility model;

[0021] Figure 3 This is a schematic diagram of the structure of the second foil layer of the current collector of this utility model.

[0022] Icon labels:

[0023] 1. First foil layer; 11. Third wavy surface; 2. Second foil layer; 21. First wavy surface; 22. Second wavy surface; 23. First connecting plane; 24. Second connecting plane; 3. Third foil layer; 31. Fourth wavy surface. Detailed Implementation

[0024] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0025] In the description of this utility model, it should be understood that the orientation descriptions, such as up and down, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model 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. Therefore, they should not be construed as limitations on this utility model.

[0026] In the description of this utility model, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features or their sequential relationship.

[0027] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0028] The high energy density of silicon-based battery cells is primarily attributed to the superior performance of silicon-based anode materials in electrochemical reactions. Specifically, when silicon alloys with lithium ions, its theoretical specific capacity reaches 4200 mAh / g, more than ten times that of traditional graphite anode materials. This significant capacity advantage gives silicon unparalleled potential in improving battery energy density. Furthermore, silicon has a low electrochemical lithium intercalation potential, approximately 0.4V vs. Li / Li+, which not only prevents lithium plating but also further enhances battery safety and stability. In addition, silicon resources are abundant in the Earth's crust and readily available, making it widely considered an ideal choice for next-generation high-energy-density lithium-ion battery anode materials.

[0029] However, while silicon-based battery cells exhibit high energy density, they also face the challenge of easy expansion. This problem stems from the significant volume changes silicon undergoes during charging and discharging. Specifically, when lithium ions are inserted into silicon, the silicon lattice expands; conversely, when lithium ions are extracted, the lattice contracts. This repeated volume change not only threatens the structural stability of the electrode material but also leads to overall cell expansion. More seriously, during lithium insertion, the outer amorphous LixSi layer expands, while the inner, uninserted portion remains unchanged. This uneven volume change generates significant stress within each silicon particle, ultimately causing cracking and pulverization. With continued charge-discharge cycles, this cracking and pulverization intensifies, new surfaces are continuously generated, and the solid electrolyte interphase (SEI) layer continues to form. This not only consumes a large amount of lithium ions, leading to continuous capacity decay, but also further exacerbates the cell expansion problem.

[0030] The fracture of the current collector in a battery cell can cause various adverse effects, such as decreased battery performance, increased risk of internal short circuits, reduced battery cycle life, and increased battery manufacturing costs. The current collector is a crucial component of the positive and negative electrodes in a lithium-ion battery cell. It carries the active material and collects current for output, converting chemical energy into electrical energy. When the current collector fractures, its ability to carry and transmit current is affected, leading to a decline in battery performance. This manifests as reduced battery capacity, increased internal resistance, and decreased charge / discharge efficiency. After the current collector fractures, burrs or sharp edges may form at the fracture site. These burrs or sharp edges may penetrate the separator between adjacent electrode layers, causing an internal short circuit. An internal short circuit not only reduces battery performance but may also trigger safety hazards such as overheating, expansion, or even explosion. The fracture of the current collector is often accompanied by the breakage and decomposition of active particles, which shortens the battery cycle life. The breakage of active particles blocks the internal conductive pathways, reducing electrochemical activity and accelerating battery degradation. Furthermore, the new surface created by the fracture may be exposed to the electrolyte, triggering electrolyte decomposition reactions and further leading to irreversible capacity loss. Current collector fracture can lead to a decrease in battery yield during manufacturing, thereby increasing manufacturing costs. Furthermore, repairing or replacing a fractured current collector requires additional repair and testing steps, which also increases production costs and time. In summary, current collector fracture in a battery cell negatively impacts battery performance, safety, cycle life, and manufacturing costs. Therefore, during battery design and manufacturing, the material and structural design of the current collector should be carefully considered to improve its strength and toughness and reduce the risk of fracture.

[0031] Reference Figure 1 , Figure 2 and Figure 3The current collector in the first embodiment of this utility model includes: a first foil layer 1, a second foil layer 2, and a third foil layer 3; the elongation coefficient of the second foil layer 2 is greater than that of the first foil layer 1 and the third foil layer 3; the second foil layer 2 is wavy along a first direction, which is the length extension direction of the current collector; the second foil layer 2 has a first wavy surface 21 and a second wavy surface 22 opposite to each other along a second direction, which is the thickness direction of the second foil layer 2; the first foil layer 1 is fixedly disposed on the first wavy surface 21, and the third foil layer 3 is disposed on the second wavy surface 22. To form the first wavy surface 21 and the second wavy surface 22, the second foil layer 2 is wavy, that is, the flat second foil layer 2 can be rolled into a wavy state by rolling. Specifically, a foil with a tensile strength of not less than 45 kgf / mm² can be used as the material of the second foil layer 2. The first foil layer 1 and the third foil layer 3 are made of foil with a tensile strength of not less than 34 kgf / mm² and an elongation of not less than 8%. When fixing the first foil layer 1 and the second foil layer 2, and when connecting the second foil layer 2 and the third foil layer 3, diffusion welding can be used. That is, in a vacuum or inert gas environment, pressure is applied in a second direction, that is, pressure is simultaneously applied to the side of the first foil layer 1 facing away from the second foil layer 2 and the side of the third foil layer 3 facing away from the second foil layer 2, while the temperature is controlled between 200-300°C and maintained for 10-60 minutes. This completes the fixing between the first foil layer 1 and the second foil layer 2, and between the second foil layer 2 and the third foil layer 3. When the battery expands, i.e., when the current collector is stretched, the first foil layer 1 and the third foil layer 3 are initially subjected to tensile force. After the first foil layer 1 and the third foil layer 3 break due to the large tensile force, the corrugated second foil layer 2 deforms and straightens. At this time, the deformation of the second foil layer 2 greatly reduces the tensile force on the current collector. This prevents the current collector from completely breaking and ensures sufficient electrical connection. At the same time, the arrangement of the first foil layer 1 and the second foil layer 2 also prevents the current collector from undergoing excessive deformation during normal battery operation.

[0032] According to some embodiments of this utility model, the tensile strength of the first foil layer 1 and the third foil layer 3 is greater than the tensile strength of the second foil layer 2. By setting the first foil layer 1 and the third foil layer 3 with greater tensile strength, the deformation of the current collector during normal battery operation is greatly reduced, thereby extending the battery's service life.

[0033] Excessive deformation of the current collector can lead to several problems, including: affecting battery performance and lifespan, causing safety issues, impacting battery cycle stability, and limiting fast-charging performance. As a crucial component of the battery, deformation of the current collector can reduce the contact area with the active material, increasing contact resistance and affecting the battery's conductivity. This not only reduces charge / discharge efficiency but may also accelerate the battery's aging process and shorten its lifespan. Deformation can also weaken the adhesion between the current collector and electrode materials, making the active material more prone to detachment. Loss of active material directly affects battery capacity and performance, leading to faster capacity decay. In extreme cases, excessive current collector deformation can trigger an internal short circuit. When the current collector comes into contact with other battery components (such as the separator), a short circuit can generate high temperatures, potentially leading to serious safety issues such as thermal runaway and explosion. Deformation of the current collector can alter the stress distribution within the battery, causing uneven expansion and contraction during charge and discharge. This uneven deformation exacerbates the damage to the battery's internal structure and reduces cycle stability. Deformation of the current collector can also affect the battery's fast-charging performance. Traditional current collectors are impermeable to the electrolyte, which easily hinders the movement of lithium ions. When the current collector deforms excessively, this hindering effect may be further aggravated, limiting the battery's performance during high-rate charge and discharge.

[0034] According to some embodiments of this utility model, a third wavy surface 11 is provided on the side of the first foil layer 1 facing the second foil layer 2, and the third wavy surface 11 is adhered and fixed on the first wavy surface 21. Through the cooperation of the first wavy surface 21 and the third wavy surface 11, the first foil layer 1 and the second foil layer 2 can be adhered more tightly, and the tensile strength of the current collector can also be effectively enhanced.

[0035] According to some embodiments of this utility model, a fourth corrugated surface 31 is provided on the side of the third foil layer 3 facing the second foil layer 2, and the fourth corrugated surface 31 is adhered and fixed on the second corrugated surface 22. Through the cooperation of the second corrugated surface 22 and the fourth corrugated surface 31, the third foil layer 3 and the second foil layer 2 can be adhered more tightly, and the tensile strength of the current collector can also be effectively enhanced.

[0036] According to some embodiments of this utility model, the crest of the first wavy surface 21 is fixedly connected to the first foil layer 1, and the crest of the second wavy surface 22 is fixedly connected to the third foil layer 3. The crests can be fixed using various methods such as welding. Welding only the crests allows for easier and faster fixing, and also gives the second foil layer 2 greater freedom of movement when bending or straightening, reducing the resistance of the second foil and allowing for better deformation and stretching.

[0037] According to some embodiments of this utility model, the crest of the first wavy surface 21 is provided with a first connecting plane 23, which is fixedly connected to the first foil layer 1; and / or, the crest of the second wavy surface 22 is provided with a second connecting plane 24, which is fixedly connected to the third foil layer 3. By providing the first plane, the connection area between the first foil layer 1 and the second foil layer 2 can be increased, thereby making the connection between the first foil layer 1 and the second foil layer 2 more robust. By providing the second plane, the connection area between the third foil layer 3 and the second foil layer 2 can be increased, thereby making the connection between the third foil layer 3 and the second foil layer 2 more robust.

[0038] According to some embodiments of this utility model, the thickness of the second foil layer 2 is E, and the distance between the crest and trough of the first wavy surface 21 in the second direction is C, where 0.1E ≤ C ≤ 0.2E. The proportional relationship between the thickness E of the second foil layer 2 and the distance C between the crest and trough of the first wavy surface 21 in the second direction has a crucial influence on the deformation of the second foil layer 2. Specifically, when the thickness E of the second foil layer 2 is too large relative to C, the second foil layer 2 is difficult to straighten and deform, thus failing to effectively eliminate the tensile force caused by battery expansion. When the thickness E of the second foil layer 2 is too small relative to C, it is prone to breakage.

[0039] According to some embodiments of this utility model, the width of the first connecting plane in the first direction is B, the interval between adjacent wave crests on the first wave surface 21 is A, and the distance between the crest and trough of the first wave surface 21 in the second direction is C, where C ≤ 1 / 2A ≤ B. When the distance A between wave crests is too small relative to the distance C between the crest and trough of the first wave surface 21 in the second direction, the thickness occupied by the second foil layer 2 will be large, thereby affecting the energy density of the battery and also affecting the tensile strength of the first foil layer 1 and the second foil layer 2. When the distance A between wave crests is large relative to the width B of the first plane in the first direction, the amount of expansion and contraction will be small. Therefore, the distance A between wave crests is limited.

[0040] According to some embodiments of this utility model, the thickness of the first foil layer 1 and the third foil layer 3 is D, and the thickness of the second foil layer 2 is E, where 1 / 4E ≤ D ≤ 1 / 2E. When the thickness D of the first foil layer 1 and the third foil layer 3 is too large, it will increase the thickness of the current collector, thereby reducing the energy density of the battery. When the thickness D of the first foil layer 1 and the third foil layer 3 is too small, it will reduce the tensile strength of the current collector. Therefore, the thickness D of the first foil layer 1 and the third foil layer 3 is limited.

[0041] The cathode sheet according to a second aspect of the present invention includes the current collector of any of the above embodiments.

[0042] The battery according to a third aspect of the present invention includes the battery described in the above embodiments.

[0043] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A current collector, characterized in that, include: First foil layer, second foil layer and third foil layer; The elongation coefficient of the second foil layer is greater than that of the first foil layer and the third foil layer; The second foil layer is wavy along a first direction, which is the length extension direction of the current collector. The second foil layer is provided with a first wavy surface and a second wavy surface opposite each other along a second direction, which is the thickness direction of the second foil layer. The first foil layer is fixedly disposed on the first wave surface, and the third foil layer is disposed on the second wave surface.

2. The current collector according to claim 1, characterized in that, The tensile strength of the first foil layer and the third foil layer is greater than the tensile strength of the second foil layer.

3. The current collector according to claim 1, characterized in that, The first foil layer has a third wavy surface on the side facing the second foil layer, and the third wavy surface is attached and fixed to the first wavy surface.

4. The current collector according to claim 1, characterized in that, The third foil layer has a fourth wavy surface on the side facing the second foil layer, and the fourth wavy surface is attached and fixed to the second wavy surface.

5. The current collector according to claim 1, characterized in that, The crest of the first wave surface is fixedly connected to the first foil layer, and the crest of the second wave surface is fixedly connected to the third foil layer.

6. The current collector according to claim 1, characterized in that, The crest of the first wave surface is provided with a first connecting plane, which is fixedly connected to the first foil layer; and / or, the crest of the second wave surface is provided with a second connecting plane, which is fixedly connected to the third foil layer.

7. The current collector according to claim 1, characterized in that, The thickness of the second foil layer is E, and the distance between the crest and trough of the first wave surface in the second direction is C, where 0.1E≤C≤0.2E.

8. The current collector according to claim 6, characterized in that, The width of the first connecting plane in the first direction is B, the interval between adjacent wave crests on the first wave surface is A, and the distance between the wave crest and wave trough of the first wave surface in the second direction is C, where C≤1 / 2A≤B.

9. The current collector according to claim 7, characterized in that, The thickness of the first foil layer and the third foil layer is D, and the thickness of the second foil layer is E, where 1 / 4E ≤ D ≤ 1 / 2E.

10. A cathode plate, characterized in that, The current collector includes any one of claims 1-9.

11. A battery, characterized in that, Includes the cathode sheet as described in claim 10.

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