A pole piece and a battery

Abstract

The utility model relates to the technical field of battery discloses a kind of pole piece and battery, including current collector, current collector is equipped with single-face area and double-face area connected in turn, the opposite face of current collector is connected with active material layer and conductive compensation layer to form double-face area, conductive compensation layer is located between active material layer and current collector, current collector is connected with active material layer and thickness compensation layer to form single-face area, and active material layer and conductive compensation layer are respectively and current collector electrically connected.The pole piece and battery of the utility model make up the thickness loss of single-face area, eliminate the underpressure caused by the thickness reduction of pole piece in the process of being rolled from double-face area to single-face area, and improve the compaction ratio of single-face area.

Description

Technical Field

[0001] This utility model relates to the technical field of batteries, and in particular to an electrode and a battery. Background Technology

[0002] Currently, with the continued rise in demand for high-capacity batteries in the 3C market, the extreme characteristics of high coating weight (CW) products pose greater challenges to the manufacturing process. During electrode manufacturing, the thickness difference between single-sided and double-sided regions leads to a significantly lower compaction density in the single-sided negative electrode area compared to the double-sided area during the rolling process. This difference not only weakens the contact interface between active particles and between particles and the conductive agent but also causes problems such as decreased electronic conductivity, increased ohmic impedance, and intensified electrochemical polarization. Especially under high-rate charging conditions, the single-sided area is more prone to lithium plating due to the lower lithium plating potential threshold.

[0003] Currently, the industry has introduced a "Fast Response" mechanism through equipment optimization to improve the undervoltage problem in the single-sided area. However, due to the complex geometric characteristics of the single- and double-sided transition areas (narrow transition zone, small area ratio), the trigger position and control accuracy of the fast response system still face engineering implementation challenges. Utility Model Content

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. It provides an electrode and a battery that compensate for thickness loss in the single-sided area, eliminates underpressure caused by the reduction in electrode thickness during the rolling process from the double-sided area to the single-sided area, and improves the compaction ratio of the single-sided area.

[0005] To achieve the above objectives, this utility model provides an electrode sheet, including a current collector. The current collector has a single-sided region and a double-sided region connected in sequence. Each opposite side of the current collector is connected to an active material layer and a conductive compensation layer to form the double-sided region. The conductive compensation layer is located between the active material layer and the current collector. The current collector is connected to the active material layer and a thickness compensation layer to form the single-sided region. The active material layer and the conductive compensation layer are respectively conductively connected to the current collector.

[0006] As a preferred embodiment, the thickness of the conductive compensation layer is A μm, the thickness of the active material layer is B μm, and the thickness of the thickness compensation layer is C μm, wherein 0.6*(2A+B)≤C≤1*(2A+B).

[0007] As a preferred option, 57μm≤C≤95μm.

[0008] As a preferred embodiment, the thickness compensation layer is a conductive layer, located between the active material layer and the current collector, and is bonded to and electrically connected to the current collector. One end of the thickness compensation layer is connected to both the active material layer and the conductive compensation layer in the double-sided region.

[0009] As a preferred embodiment, the thickness compensation layer is an insulating layer, the thickness compensation layer is connected to one side of the current collector, the active material layer is connected to the other side of the current collector, the thickness compensation layer and the active material layer are arranged opposite to each other, and one end of the thickness compensation layer is connected to the active material layer and the conductive compensation layer of the double-sided region, respectively.

[0010] As a preferred embodiment, the conductive compensation layer extends to the single-sided area, the conductive compensation layer is located between the current collector and the active material layer, and the active material layer is connected to the current collector through the conductive compensation layer.

[0011] As a preferred embodiment, the length of the single-sided area is c mm, and the length of the double-sided area is d mm, where c < d.

[0012] As a preferred embodiment, the two opposite sides of the conductive compensation layer are bonded to the current collector and the active material layer, respectively.

[0013] As a preferred embodiment, the electrode is a negative electrode.

[0014] A battery includes a core, the core comprising an anode sheet and a separator, wherein the anode sheet, the separator, the electrode sheet and the separator are sequentially stacked and wound to form the core.

[0015] Compared with existing technologies, the electrode and battery of this utility model embodiment have the following advantages: In the double-sided region, an active material layer and a conductive compensation layer are coated on the current collector. The conductive compensation layer can form a basic conductive network, ensuring effective electron transfer between the current collector and the active material layer. In the single-sided region, an active material layer and a thickness compensation layer are coated on the current collector. Increasing the thickness of the thickness compensation layer in the single-sided region compensates for the thinness of the active material layer, makes up for the thickness loss in the single-sided region, eliminates the undervoltage caused by the reduction in electrode thickness during the rolling process from the double-sided region to the single-sided region, and improves the compaction ratio of the single-sided region. At the same time, the conductive compensation layer and the thickness compensation layer achieve the thickness filling of the electrode. Since an excessively thick active material layer will prolong the lithium-ion diffusion path, leading to increased local polarization and affecting fast charging performance and cycle life, this embodiment avoids the lithium-ion diffusion limitation caused by an excessively thick active material layer, and does not require changing any key parameters of the original cell design, thus reducing improvement costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the thickness compensation layer being a conductive layer in an embodiment of this utility model.

[0017] Figure 2 This is a schematic diagram of the structure of the thickness compensation layer being an insulating layer in an embodiment of this utility model.

[0018] In the picture:

[0019] 10. Current collector; 11. Single-sided area; 12. Double-sided area; 13. Active material layer; 14. Conductive compensation layer; 15. Thickness compensation layer. Detailed Implementation

[0020] The specific embodiments of this utility model will be described in further 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 its scope.

[0021] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" used to indicate the orientation or positional relationship 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.

[0022] In the description of this utility model, it should be understood that the terms "connected," "linked," and "fixed," etc., used in this utility model should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or a welded connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly defined. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0023] like Figures 1 to 2 As shown, a preferred embodiment of the present invention includes a current collector 10. The current collector 10 has a single-sided region 11 and a double-sided region 12 connected in sequence. The opposite sides of the current collector 10 are connected to an active material layer 13 and a conductive compensation layer 14 to form a double-sided region 12. The conductive compensation layer 14 is located between the active material layer 13 and the current collector 10. The current collector 10 is connected to an active material layer 13 and a thickness compensation layer 15 to form a single-sided region 11. The active material layer 13 and the conductive compensation layer 14 are electrically connected to the current collector 10.

[0024] In this invention, the electrode and battery have the following characteristics: In the double-sided region 12, the current collector 10 is coated with an active material layer 13 and a conductive compensation layer 14. The conductive compensation layer 14 forms a basic conductive network, ensuring effective electron transfer between the current collector 10 and the active material layer 13. In the single-sided region 11, the current collector 10 is coated with an active material layer 13 and a thickness compensation layer 15. Increasing the thickness of the thickness compensation layer 15 in the single-sided region 11 compensates for the thinness of the active material layer 13, reduces the thickness loss in the single-sided region 11, eliminates underpressure caused by the reduced electrode thickness during the rolling process from the double-sided region 12 to the single-sided region 11, and improves the compaction ratio of the single-sided region 11. Meanwhile, the electrode thickness is filled by the conductive compensation layer 14 and the thickness compensation layer 15. Since the active material layer 13 is too thick, it will prolong the diffusion path of lithium ions, resulting in increased local polarization, which will affect fast charging performance and cycle life. This can avoid the lithium ion diffusion limitation caused by the excessive thickness of the active material layer 13, and does not require any changes to the original cell design, thus reducing the improvement cost.

[0025] In one embodiment, the thickness of the single-sided region 11 is a μm, and the thickness of the double-sided region 12 is b μm, where a ≥ b. The current collector 10 is coated with an active material layer 13 and a thickness compensation layer 15. The thickness of the thickness compensation layer 15 is increased in the single-sided region 11 to compensate for the thinness of the active material layer 13 in the single-sided region 11, to make up for the thickness loss of the single-sided region 11, to eliminate the underpressure caused by the reduction in electrode thickness during the rolling process from the double-sided region 12 to the single-sided region 11, and to improve the compaction ratio of the single-sided region 11.

[0026] Furthermore, such as Figures 1 to 2 As shown, the thickness of the conductive compensation layer 14 is A μm, the thickness of the active material layer 13 is B μm, and the thickness of the thickness compensation layer 15 is C μm, where 0.6*(2A+B)≤C≤1*(2A+B). By increasing the thickness of the single-sided region 11 through the thickness compensation layer 15, the change in electrode thickness is reduced when the roller press switches from the double-sided region 12 to the single-sided region 11, thus reducing the stress change on the electrode in the single-sided region 11 and the single-sided compaction change. This reduces the risk of undervoltage in the single-sided region 11 and the risk of lithium plating in the single-sided region 11 of the cell.

[0027] Controlling 0.6*(2A+B)≤C≤1.0*(2A+B), if the thickness of the thickness compensation layer 15 is less than 0.6*(2A+B), the thickness compensation effect is not obvious and cannot effectively improve the compaction density of the single-sided area 11. If the thickness of the thickness compensation layer 15 is greater than 1.0*(2A+B), it will cause the single-sided area 11 to be too thick, resulting in overpressure.

[0028] Furthermore, such as Figures 1 to 2As shown, 57μm≤C≤95μm. Setting the thickness of the thickness compensation layer 15 within this range can ensure the compaction density of the single-sided area 11, while avoiding over-compression caused by excessive thickness of the single-sided area 11.

[0029] Furthermore, such as Figure 1 As shown, the thickness compensation layer 15 is a conductive layer located between the active material layer 13 and the current collector 10. The thickness compensation layer 15 is bonded to and conductively connected to the current collector 10. One end of the thickness compensation layer 15 is connected to both the active material layer 13 and the conductive compensation layer 14 of the double-sided region 12. The active material layer 13 of the single-sided region 11 is conductively connected to the current collector 10 through the thickness compensation layer 15. By increasing the thickness of the thickness compensation layer 15, the problem of the relatively thin active material layer 13 in the single-sided region 11 is compensated, making the total thickness of the single and double-sided regions 12 consistent. Simultaneously, the high conductive agent content of the thickness compensation layer 15 compensates for the extended electron transport path caused by the increased thickness of the thickness compensation layer 15, ensuring that the overall conductivity of the single-sided region 11 is comparable to that of the double-sided region 12, and reducing the interfacial contact resistance of the single-sided region 11. The high binder content enhances the mechanical strength of the thickness compensation layer 15, preventing coating cracking or deformation due to localized stress concentration during rolling.

[0030] In one embodiment, the coating slurry of the thickness compensation layer 15 includes a conductive material, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (N-Methylpyrrolidone). The mass ratio of the conductive material, PVDF, and N-Methylpyrrolidone is (2-3):(1-2):(100-200) to ensure adhesion and conductivity.

[0031] In one embodiment, the coating slurry of the conductive compensation layer 14 includes a conductive material, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (N-Methylpyrrolidone). The mass ratio of the conductive material, PVDF, and N-Methylpyrrolidone is (1-2):(0.5-1):(100-200). A small amount of conductive agent is sufficient to form a basic conductive network, ensuring effective electron transport between the current collector 10 and the active material layer 13. An appropriate amount of binder maintains the adhesion between the active material layer 13 and the current collector 10, preventing coating detachment during rolling or cycling. Furthermore, when the active material layer 13 is coated on both sides of the 12, the conductive compensation layer 14, as the underlying support, needs to form a good interface with the upper active material layer 13 to avoid delamination due to insufficient adhesion.

[0032] In one embodiment, the conductive material is graphite or carbon black.

[0033] Furthermore, such as Figure 2As shown, the thickness compensation layer 15 is an insulating layer, connected to one side of the current collector 10, and the active material layer 13 is connected to the other side of the current collector 10. The thickness compensation layer 15 and the active material layer 13 are arranged opposite to each other, and one end of the thickness compensation layer 15 is connected to the active material layer 13 and the conductive compensation layer 14 of the double-sided region 12, respectively. By using insulating material to perform thickness compensation in the non-material area of ​​the single-sided region 11, the thickness compensation is more balanced, effectively preventing the active material layer 13 from falling off due to excessive thickness in the single-sided region 11 on the same side after compensation. At the same time, insulating material is used as a base coat at the thickness compensation area in the non-material area to prevent short circuits caused by tearing of the aluminum foil, thus improving safety performance. The thickness compensation layer 15 does not participate in the electrochemical reaction and does not prolong the lithium-ion diffusion path, thereby reducing polarization. The thickness compensation layer 15 improves the rigidity of the electrode sheet and reduces the risk of deformation during the rolling process.

[0034] It should be noted that the non-material area refers to the area on one side of the current collector 10 that is not coated with active material.

[0035] As one embodiment, the insulating material can be an insulating ceramic or a polymer.

[0036] Furthermore, such as Figure 2 As shown, the conductive compensation layer 14 extends to the single-sided region 11. The conductive compensation layer 14 is located between the current collector 10 and the active material layer 13, and the active material layer 13 is connected to the current collector 10 through the conductive compensation layer 14. The conductive compensation layer 14 extends to the single-sided region 11, ensuring effective electron transfer between the current collector 10 and the active material layer 13, thus improving the overall conductivity of the electrode. The thickness compensation layer 15 is an insulating layer. The base coating of the insulating material can suppress the side reactions of the electrolyte, while simultaneously achieving thickness compensation and performance optimization.

[0037] As one embodiment, such as Figure 1 As shown, the two sides of the thickness compensation layer 15 are bonded to the conductive compensation layer 14 and the active material layer 13, respectively, increasing the thickness of the single-sided area 11. When the roller press is switched from the double-sided area 12 to the single-sided area 11, the change in electrode thickness is reduced, the change in force on the electrode in the single-sided area 11 is reduced, and the change in compaction of the single-sided area 11 is reduced, thereby reducing the risk of undervoltage in the single-sided area 11 and reducing the risk of lithium plating in the single-sided area 11 of the cell.

[0038] Furthermore, such as Figures 1 to 2As shown, the length of the single-sided region 11 is c mm, and the length of the double-sided region 12 is d mm, where c < d. In a wound battery, the single-sided region 11 is located at the edge of the electrode (such as at the tab connection). The shorter c value makes the edge easier to bend and less prone to cracking due to stress concentration, while the double-sided region 12 serves as the main body to provide stable energy storage. When the length d of the double-sided region 12 is longer, the lithium-ion transport path is more uniform, reducing concentration polarization; the single-sided region 11 serves as a transition region, alleviating the problem of excessively high edge current density and improving charge and discharge efficiency.

[0039] Furthermore, such as Figures 1 to 2 As shown, the two opposite sides of the conductive compensation layer 14 are bonded to the current collector 10 and the active material layer 13, respectively. An appropriate amount of adhesive is applied to the conductive compensation layer 14 to maintain the adhesion between the active material layer 13 and the current collector 10, preventing the coating from peeling off during rolling or cycling. Furthermore, when the active material layer 13 is coated on both sides of the area 12, the conductive compensation layer 14, acting as a bottom support, needs to form a good interface with the active material layer 13 to avoid delamination due to insufficient adhesion.

[0040] Furthermore, such as Figures 1 to 2 As shown, the electrode is a negative electrode. Traditional coating equipment requires extremely high precision in slurry transfer in areas with alternating thicknesses (single-sided area 11 and double-sided area 12), making adjustment difficult. This invention adds a thickness compensation layer 15 and a conductive compensation layer 14, which are applied separately through printing, deposition, and other processes, reducing process complexity. Existing technologies mention increasing the areal density of the negative electrode in the single-sided area 11 and decreasing the areal density of the corresponding positive electrode in the single-sided area 11 (variable coating section), thereby increasing the CB value and improving the lithium plating problem in the single-sided area 11 after long cycling. However, areas with excessively high CB values ​​may generate higher polarization voltages due to hindered lithium ion insertion / extraction, leading to increased internal resistance; local CB value imbalances can cause differences in expansion / contraction amplitudes in different areas, generating mechanical stress and causing problems such as electrode cracking and coating peeling. Since there is no need to adjust existing coating parameters, the adverse effects of changing the CB value are avoided. In existing technologies, coating uniformity is difficult to control; an excessively thick active material layer 13 leads to uneven slurry flow during coating, easily causing cracks or warping after drying. The thickness compensation layer 15 and the conductive compensation layer 14 can be set independently (e.g., controlled by die gap or deposition time) to avoid fluctuations in the coating thickness of the active material layer 13. The thickness compensation layer 15 and the conductive compensation layer 14 fill the micropores on the surface of the current collector 10, improve the adhesion between the active material layer 13 and the current collector 10, and reduce the contact resistance.

[0041] It should be noted that CB stands for Cell Balance, which refers to the margin by which the negative electrode capacity exceeds the positive electrode capacity within the same stage and under the same conditions.

[0042] It should be noted that the active material layer 13 is the active material material of the electrode in the prior art.

[0043] A battery includes a core, which includes an anode sheet and a separator. The anode sheet, separator, negative electrode sheet and separator are stacked in sequence and wound to form the core.

[0044] This application prepares a negative electrode sheet, wherein when the thickness compensation layer 15 is a conductive layer, the thickness of the conductive compensation layer 14 is A μm, the thickness of the active material layer 13 is B μm, and the thickness of the thickness compensation layer 15 is C μm, wherein (2A+B) is 95 μm. According to 0.6*(2A+B)≤C≤1*(2A+B), the value of C is respectively Example 1 (0.6*(2A+B))=57μm, Example 2 (0.8*(2A+B))=76μm and Example 3 (1.0*(2A+B))=95μm;

[0045] Example 4 shows that the thickness compensation layer 15 is an insulating layer, and the value of C is 76μm (0.8*(2A+B)).

[0046] The C value of Comparative Example 1 was set at 38 μm = (0.4 * (2A + B)) and the C value of Comparative Example 2 was set at 114 μm = (1.2 * (2A + B)).

[0047] This invention was tested on Examples 1-4 and Comparative Examples 1-2 using the following test methods: The negative electrode sheet after rolling was taken out, and the thickness of the single-sided area 11 and double-sided area 12 was measured using a micrometer. The compaction ratio of the single-sided area 11 was calculated using the formula: Single-sided area compaction ratio = Single-sided area 11 compaction density / Double-sided area 12 compaction density = [(Double-sided area 12 thickness - foil thickness) / 2] / (Single-sided area 11 thickness - foil thickness). After the cell was prepared, it was charged to 4.48V at 25℃ using a 1C constant voltage and constant current method, and then discharged at a 1C constant current method for 500 cycles. The battery was then disassembled to observe whether lithium plating occurred in the single-sided area 11.

[0048]

[0049]

[0050] As can be seen from the above Examples 1-4 and Comparative Examples 1-2, the value of C / (2A+B) is in the range of 0.6-1.0, the compaction ratio of the single-sided area 11 is controlled in a good range of 92%-101%, the appearance of the negative electrode sheet is good, there is no shedding of the single-sided area 11, and no lithium plating is generated after the cell is cycled.

[0051] In summary, this utility model embodiment provides an electrode and a battery. In the double-sided region 12, the current collector 10 is coated with an active material layer 13 and a conductive compensation layer 14. The conductive compensation layer 14 can form a basic conductive network, ensuring effective electron transfer between the current collector 10 and the active material layer 13. In the single-sided region 11, the current collector 10 is coated with an active material layer 13 and a thickness compensation layer 15. Increasing the thickness of the thickness compensation layer 15 in the single-sided region 11 compensates for the thinness of the active material layer 13, makes up for the thickness loss in the single-sided region 11, eliminates the underpressure caused by the reduction in electrode thickness during the rolling process from the double-sided region 12 to the single-sided region 11, and improves the compaction ratio of the single-sided region 11. Meanwhile, the electrode thickness is filled by the conductive compensation layer 14 and the thickness compensation layer 15. Since the active material layer 13 is too thick, it will prolong the diffusion path of lithium ions, resulting in increased local polarization, which will affect fast charging performance and cycle life. This can avoid the lithium ion diffusion limitation caused by the excessive thickness of the active material layer 13, and does not require any changes to the original cell design, thus reducing the improvement cost.

[0052] The above are merely preferred embodiments of this 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 this utility model, and these improvements and substitutions should also be considered within the protection scope of this utility model.

Claims

1. An electrode sheet, characterized in that: The device includes a current collector, which has a single-sided area and a double-sided area connected in sequence. The opposite sides of the current collector are connected to an active material layer and a conductive compensation layer to form the double-sided area. The conductive compensation layer is located between the active material layer and the current collector. The current collector is connected to the active material layer and a thickness compensation layer to form the single-sided area. The active material layer and the conductive compensation layer are electrically connected to the current collector.

2. The electrode sheet according to claim 1, characterized in that: The thickness of the conductive compensation layer is A μm, the thickness of the active material layer is B μm, and the thickness of the thickness compensation layer is C μm, wherein 0.6*(2A+B)≤C≤1*(2A+B).

3. The electrode sheet according to claim 2, characterized in that: 57μm≤C≤95μm.

4. The electrode sheet according to claim 1, characterized in that: The thickness compensation layer is a conductive layer, located between the active material layer and the current collector. The thickness compensation layer is bonded to and electrically connected to the current collector. One end of the thickness compensation layer is connected to both the active material layer and the conductive compensation layer in the double-sided region.

5. The electrode sheet according to claim 1, characterized in that: The thickness compensation layer is an insulating layer. The thickness compensation layer is connected to one side of the current collector, and the active material layer is connected to the other side of the current collector. The thickness compensation layer and the active material layer are arranged opposite to each other. One end of the thickness compensation layer is connected to the active material layer and the conductive compensation layer of the double-sided region, respectively.

6. The electrode sheet according to claim 5, characterized in that: The conductive compensation layer extends to the single-sided area and is located between the current collector and the active material layer. The active material layer is connected to the current collector through the conductive compensation layer.

7. The electrode sheet according to claim 1, characterized in that: The length of the single-sided area is c mm, and the length of the double-sided area is d mm, where c < d.

8. The electrode sheet according to claim 1, characterized in that: The two opposite sides of the conductive compensation layer are respectively bonded to the current collector and the active material layer.

9. The electrode sheet according to any one of claims 1-8, characterized in that: The electrode is a negative electrode.

10. A battery, characterized in that: The device includes a core body, which includes an anode sheet and a diaphragm. The anode sheet, the diaphragm, the electrode sheet as described in claim 9, and the diaphragm are sequentially stacked and wound to form the core body.

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