A composite current collector and a battery

Abstract

The present invention relates to the technical field of battery production, and specifically discloses a composite current collector and a battery. The composite current collector includes a current collector and a tab; the current collector includes a first side surface and a second side surface that are oppositely arranged along the width direction of the current collector, and the tab is connected to the first side surface; wherein, a plurality of conductive coatings are coated on the current collector, the plurality of conductive coatings are sequentially arranged along the width direction of the current collector, and the resistance of the plurality of conductive coatings gradually decreases in a direction away from the tab. The composite current collector and the battery provided by the present invention can effectively solve the problem of uneven current density in the existing current collector.

Description

Technical Field

[0001] The present invention relates to the technical field of battery production, and particularly to a composite current collector and a battery. Background Art

[0002] A tab is often connected to the current collector for leading out the current on the current collector to the outside.

[0003] Generally, the current density distribution in the current collector is uneven. Specifically, since all the current in the current collector is led out through the tab, the closer the position in the current collector is to the tab, the higher the current density, and the farther the position in the current collector is from the tab, the lower the current density. Furthermore, for the electrode sheet made of the above current collector, the faster the lithium deintercalation rate and the larger the deintercalation amount are required in the region with a larger current density, and the more serious the damage to the structure of the active material in the electrode sheet is, resulting in rapid capacity decay and lithium deposition on the negative electrode during cycling. Moreover, the greater the charge-discharge rate, the more uneven the current distribution, which will exacerbate this adverse reaction.

[0004] Some manufacturers coat an active coating with poor rate performance at a position far from the tab on the current collector, and coat an active coating with good rate performance at a position close to the tab on the current collector, so that the active coatings at different positions of the current collector can all have rate performance adapted to the current density.

[0005] Taking the position close to the tab on the current collector as an example, the current density at this position is large, the lithium deintercalation rate in the electrode sheet is faster, the deintercalation amount is larger, and the damage to the structure of the active material in the electrode sheet is more serious. Therefore, during repeated charge and discharge, the position of the electrode sheet close to the tab is more likely to be damaged. When an active coating with excellent rate performance is coated at this position, during charge and discharge, the lithium ion migration rate in the active coating at this position is faster, which will further increase the current density at this position and exacerbate the damage to the structure of the active material in the electrode sheet.

[0006] That is, the method of "coating an active coating with better rate performance at a position closer to the tab" to deal with the problem of uneven current density in the current collector does not essentially solve the problem of uneven current density distribution in the current collector. The root cause is mainly that the technical means of "coating an active coating with better rate performance at a position closer to the tab" will exacerbate the difference in lithium ion migration speed in the active coatings at different positions, which will lead to more uneven current density, that is, the current density at the position close to the tab is larger and the current density at the position far from the tab is lower, and it cannot make the current density at different positions on the current collector tend to be uniform.

[0007] Therefore, it is necessary to improve the existing current collector to solve the problem of uneven current density.

[0008] The above information disclosed in this background section is only included to enhance the understanding of the background of the present disclosure, and thus may include information that does not form the prior art already known to those of ordinary skill in the art at present. Summary of the Invention

[0009] An object of the present invention is to provide a composite current collector and a battery, which can effectively solve the problem of uneven current density in the existing current collector.

[0010] To achieve the above object, on the one hand, the present invention provides a composite current collector, including a current collector and a tab;

[0011] The current collector includes a first side surface and a second side surface oppositely arranged along the width direction of the current collector, and the tab is connected to the first side surface;

[0012] Wherein, a plurality of conductive coatings are coated on the current collector, the plurality of conductive coatings are arranged in sequence along the width direction of the current collector, and the resistance of the plurality of conductive coatings gradually decreases in the direction away from the tab.

[0013] Optionally, the number of the conductive coatings is n; the distance from the center point of the xth conductive coating to the first side surface is L x , the coating resistance of the xth conductive coating is R x , then it satisfies:

[0014] L x+1 / L x =R x / R x+1 ;

[0015] Wherein,

[0016] n is a natural number, and n≥2;

[0017] x is a natural number, and x < n.

[0018] Optionally, the current collector is a continuous and uncut whole.

[0019] Optionally, the current collector includes a plurality of straight regions and a plurality of corner regions, and the straight regions and the corner regions are alternately arranged along the winding direction of the current collector; the resistance of the part of each conductive coating located in the corner region is 25% - 65% larger than that of the part located in the straight region, preferably 40% - 50%.

[0020] Optionally, the current collector is a cut single piece.

[0021] Optionally, the plurality of conductive coatings extend in a linear shape along the length direction of the current collector on the current collector.

[0022] Optionally, the current collector is divided into a plurality of coating regions by a plurality of arcs centered at the center point of the tab and having different radii; the plurality of coating regions and the plurality of conductive coatings are arranged in one-to-one correspondence.

[0023] Optionally, the current collector and the tab are of a welded connection structure, or the current collector and the tab are of an integrally formed structure.

[0024] Optionally, the resistance of the conductive coating is changed by adjusting the thickness of the conductive coating, or the mass ratio of the conductive agent in the conductive coating, or the type of the conductive agent in the conductive coating.

[0025] On the other hand, a battery is provided, including a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is made of the above-mentioned composite current collector.

[0026] The beneficial effects of the present invention are as follows: a composite current collector and a battery are provided. A plurality of conductive coatings are arranged on the current collector. A conductive coating with a larger resistance is coated at a position closer to the tab in the current collector, thereby reducing the current density at this position; correspondingly, a conductive coating with a smaller resistance is coated at a position farther from the tab in the current collector, which can reduce the resistance at this position and is beneficial to the passage of current. Therefore, after the composite current collector is made into an electrode sheet, the current density in the area close to the tab can be dispersed to the area far from the tab, making the current density in different areas of the electrode sheet uniform, thereby improving the cycle life of the battery cell. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Schematic structural diagram of the composite current collector provided in Embodiment 1;

[0029] Figure 2 Schematic structural diagram of the composite current collector provided in Embodiment 1 when it has a corner region;

[0030] Figure 3 Schematic diagram of the composite current collector provided in Embodiment 1 when it is a full-tab structure;

[0031] Figure 4 Schematic diagram of the composite current collector provided in Embodiment 1 when used as a stacked battery;

[0032] Figure 5Schematic diagram of the reference current collector in the reference example provided for Example 1;

[0033] Figure 6 Schematic diagram of the first composite current collector in Comparative Example 1 provided for Example 1;

[0034] Figure 7 Schematic diagram of the second composite current collector in Comparative Example 2 provided for Example 1;

[0035] Figure 8 Flow chart of the coating method provided for Example 2.

[0036] In the figure:

[0037] 1. Current collector; 101. Straight region; 101a. Left straight region; 101b. Right straight region; 102. Corner region;

[0038] 2. Tab;

[0039] 3. Conductive coating; 3a. First coating; 3b. Second coating; 3c. Third coating; 3d. First straight region coating; 3e. Second straight region coating; 3f. Third straight region coating; 3g. First corner region coating; 3h. Second corner region coating; 3i. Third corner region coating. Detailed implementation manners

[0040] To make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] In the description of the present invention, it should be understood that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component.

[0042] In addition, terms such as "long", "short", "inner", "outer", etc. indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have this specific orientation or be constructed and operated in this specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0043] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included in the protection scope of the present invention.

[0044] Embodiment 1

[0045] This embodiment provides a composite current collector and a battery having the composite current collector. It should be noted that the battery described in this embodiment can be a wound battery or a laminated battery, etc.

[0046] Specifically, in this embodiment, the battery includes a housing and an electrode core located inside the housing. Among them, the electrode core includes a positive electrode sheet (including a positive current collector, a positive electrode tab connected to the positive current collector, and a positive electrode active material coated on the positive current collector), a negative electrode sheet (including a negative current collector, a negative electrode tab connected to the negative current collector, and a negative electrode active material coated on the negative current collector), and a separator located between the positive electrode sheet and the negative electrode sheet.

[0047] In this embodiment, the positive current collector and / or the negative current collector is made of a composite current collector. Specifically, referring to Figure 1 , the composite current collector includes a current collector 1 and a tab 2 connected to the current collector 1; the current collector 1 includes a first side surface and a second side surface oppositely arranged along the width direction of the current collector 1, and the tab 2 is connected to the first side surface; a plurality of conductive coatings 3 are coated on the current collector 1. Specifically, a plurality of conductive coatings 3 are provided on one surface or both surfaces of the current collector 1; the plurality of conductive coatings 3 are arranged in sequence along the width direction of the current collector 1, and the resistance of the plurality of conductive coatings 3 gradually decreases in the direction away from the tab 2 ( Figure 1 the size of the resistance is represented by the density of the filling line).

[0048] It should be noted that a conductive coating 3 with a larger resistance is coated at a position closer to the tab 2 in the current collector 1, thereby reducing the current density at this position; correspondingly, a conductive coating 3 with a smaller resistance is coated at a position farther from the tab 2 in the current collector 1, which can reduce the resistance at this position and is beneficial to the passage of current. Therefore, after the composite current collector is made into an electrode sheet, the current density in the area close to the tab can be dispersed to the area far from the tab, making the current density in different areas of the electrode sheet uniform, thereby improving the cycle life of the electrode core.

[0049] In this embodiment, the number of the conductive coatings 3 is n, numbered in the direction away from the tab 2, the distance from the center point of the xth conductive coating to the first side surface is L x , and the coating resistance of the xth conductive coating is R x , then the following relational expression is satisfied:

[0050] L x+1 / L x =R x / R x+1 (1);

[0051] Wherein,

[0052] n is a natural number and n≥2;

[0053] x is a natural number and x < n.

[0054] The above relationship (1) indicates the relationship between the resistance of different conductive coatings and the distance from the conductive coatings to the tab. Therefore, only by determining the relative positions between each conductive coating and the tab, the required resistance values of each conductive coating can be calculated through the above relationship (1).

[0055] In this embodiment, the current collector 1 and the tab 2 are of an integrally formed structure. Here, the length of the tab 2 can be the same as the length of the current collector 1, that is, a full tab, or the length of the tab 2 can be less than the length of the current collector 1. At this time, a plurality of tabs 2 are arranged at intervals along the length direction of the current collector 1. In some other embodiments, the current collector 1 and the tab 2 are of a welded connection structure. Optionally, the current collector 1 and / or the tab 2 is / are a metal foil or an organic and metal composite foil. Further, when the current collector is used as the positive electrode, aluminum foil is preferred; when the current collector is used as the negative electrode, copper foil is preferred.

[0056] In this embodiment, when the electrode sheet needs to be wound to form a wound type battery cell, the winding operation of the current collector will be involved. Refer to Figure 2 , at this time, the current collector 1 is a continuous and uncut whole, and the plurality of conductive coatings extend in a linear shape along the length direction of the current collector 1 on the current collector 1.

[0057] Further, the current collector 1 includes a plurality of flat areas 101 and a plurality of corner areas 102, and the flat areas 101 and the corner areas 102 are arranged alternately along the winding direction of the current collector 1.

[0058] Generally, the stress on the corner area 102 is more concentrated, and the problem of lithium plating is likely to occur. Therefore, in order to reduce the lithium plating at the corner, a conductive coating with a relatively high resistance can be coated at the corner to reduce the current density in the corner area 102. It can be understood that when the resistance of the corner area 102 is too small, the problem of lithium plating at the corner cannot be solved, and when the resistance of the corner area 102 is too large, the conductivity of the corner area 102 will be affected. After research, it is found that when the above relationship (1) is satisfied, when the resistance of the part of each conductive coating located in the corner area 102 is 25% - 65% larger than the resistance of the part located in the straight area 101, the problem of lithium plating at the corner can be effectively solved without excessively affecting the conductivity of the corner area 102. Among them, the specific value can be any one of 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% and 65%. Further, when the resistance of the part of each conductive coating located in the corner area 102 is 40% - 50% larger than the resistance of the part located in the straight area 101, the comprehensive effect is better, and the specific value can be any one of 41%, 43%, 46% and 49%.

[0059] In this embodiment, when the battery is a stacked battery, the current collector 1 is a cut single piece. At this time, optionally, the plurality of conductive coatings can still extend linearly along the length direction of the current collector 1 on the current collector 1. Of course, it can also be as Figure 4 shown, the current collector 1 is divided into a plurality of coating areas by a plurality of arcs with the center point of the tab 2 as the center and different radii; the plurality of coating areas and the plurality of conductive coatings are arranged in one-to-one correspondence. Whether it is linear or arc-shaped, as long as the resistance of the plurality of conductive coatings gradually decreases in the direction away from the tab 2, the uniformity of the current density on the current collector 1 can be improved.

[0060] Of course, according to the change of the shape and position of the tab, the conductive coating can also be of other shapes, and this embodiment does not limit this.

[0061] A battery according to this embodiment is characterized in that it includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is made of the above-mentioned composite current collector.

[0062] The beneficial effects of the composite current collector and the battery provided by the present invention are described below in combination with specific parameters:

[0063] (I) Material preparation

[0064] Reference example: Refer to Figure 5 , a cutting edge is reserved at the edge position of a 6um thick copper foil, and a 2um thick conductive coating 3 is uniformly coated on the remaining position. The resistance of the conductive coating 3 coated at different positions is the same;

[0065] Among them, the conductive paste is obtained by mixing conductive carbon black and polyacrylate in a mass ratio of 45%:55% and adding them to deionized water, and stirring evenly.

[0066] After coating the active material on the surface of the conductive coating 3, a plurality of tabs 2 are die-cut at the cut edge, and the remaining position is the electrode plate, thereby obtaining the reference electrode plate in the reference example.

[0067] Comparative Example 1: Refer to Figure 6 , a cut edge is reserved on the surface of a 6-μm-thick copper foil, and then different conductive coatings are coated on three regions outside the cut edge. Among them, in the direction away from the cut edge, the three conductive coatings are sequentially denoted as the first coating 3a, the second coating 3b, and the third coating 3c, each coating is 2 μm thick, and the width dimensions are equal;

[0068] The resistance of the third coating 3c is the same as that of the conductive coating 3 in the reference example; the resistances of the first coating 3a and the second coating 3b are obtained by calculating according to the above formula (1); further, by adjusting the content of conductive carbon black in the conductive paste of each conductive coating, the resistance of each conductive coating can be adjusted so that the resistances in the first coating and the second coating satisfy formula (1);

[0069] After coating the active material on the surface of the conductive coating, a plurality of tabs 2 are die-cut at the cut edge, and the remaining position is the electrode plate, thereby obtaining the first electrode plate in Comparative Example 1.

[0070] Comparative Example 2: Refer to Figure 7 , a cut edge is reserved on the surface of a 6-μm-thick copper foil, and then the position outside the cut edge is divided into three regions along the length direction of the copper foil, which are respectively denoted as the left flat region 101a, the corner region 102, and the right flat region 101b. Further, in the direction away from the cut edge:

[0071] The first flat region coating 3d, the second flat region coating 3e, and the third flat region coating 3f are sequentially coated on the left flat region 101a;

[0072] The first flat region coating 3d, the second flat region coating 3e, and the third flat region coating 3f are also sequentially coated on the right flat region 101b;

[0073] The first corner region coating 3g, the second corner region coating 3h, and the third corner region coating 3i are sequentially coated on the corner region 102;

[0074] Among them, the resistance of the third flat region coating 3f is the same as that of the conductive coating 3 in the reference example. The resistance relationship among the first flat region coating 3d, the second flat region coating 3e, and the third flat region coating 3f satisfies the above formula (1), and the resistance relationship among the first corner region coating 3g, the second corner region coating 3h, and the third corner region coating 3i also satisfies the above formula (1); further, the resistance of the first corner region coating 3g is 40% greater than that of the first flat region coating 3d, the resistance of the second corner region coating 3h is 40% greater than that of the second flat region coating 3e, and the resistance of the third corner region coating 3i is 40% greater than that of the third flat region coating 3f.

[0075] After applying the active material on the surface of each conductive coating, a plurality of tabs 2 are die-cut on the cut edge of the copper foil, and the remaining position is the electrode sheet, thereby obtaining the second electrode sheet in Comparative Example 2.

[0076] (II) Battery manufacturing

[0077] The reference electrode sheet, the first electrode sheet, and the second electrode sheet are respectively used as the negative electrode sheets. Among them, the negative active material is artificial graphite material (the mass ratio of graphite, conductive agent, and binder is 96:2:2);

[0078] The positive current collector is 13-μm aluminum foil, and the positive active material is an NCM ternary material of the 811 system (the mass ratio of NCM, conductive agent, and binder is 97:2:1); the separator is a 9-μm thick PE separator; the electrolyte is a mixture of 1 mol / L LiPF6 and EC / DMC / EMC (V / V = 1:1:1), and a square aluminum shell power battery with a designed capacity of 75 Ah is made by using a multi-tab winding structure.

[0079] (III) Battery testing

[0080] Capacity: After the battery is filled with electrolyte, it is left standing at 45 °C for 12 h, then charged at 0.02C to 3.40 V, charged at 0.1C to 3.75 V, charged at 0.5C constant current and constant voltage to 4.25 V after refilling and sealing, cut off at 0.05C, and then discharged at 0.5C to 2.8 V to obtain the discharge capacity;

[0081] IMP: The AC internal resistance of the battery is measured using an internal resistance meter;

[0082] DCR: At 25 °C, the battery is adjusted to 50% SOC, discharged at 2C for 30 s, and the DCR value is calculated by dividing the voltage difference between the open circuit voltage before discharge and the voltage at the 30th second of discharge by the discharge current;

[0083] Cycling: At 25 °C, charged at 2C constant current and constant voltage to 4.25 V, cut off at 0.05C, left standing for 30 min, discharged at 1C to 2.8 V, and left standing for 30 min. Repeat the above steps.

[0084] The test results are as follows:

[0085]

[0086] Compared with the reference example, the capacity difference between Comparative Example 1 and Comparative Example 2 is not significant. Due to the relatively large resistance of the conductive coating in the near-tab region, the IMP slightly increases. However, after the current density is homogenized, the polarization decreases, so the DCR decreases. In addition, the cycle has been significantly improved. After differentiating the resistance of the conductive coating at the corner in Comparative Example 2, the cycle is better than that in Comparative Example 1. It can be seen that the composite current collector and battery provided in this embodiment have a good current sharing effect, which is beneficial to improving the cycle performance of the battery.

[0087] In summary, compared with the prior art, the composite current collector and battery provided in this embodiment have the following beneficial effects:

[0088] ① By making the resistance of each of the conductive coatings gradually decrease in the direction away from the tab, the current density in different regions of the composite current collector is made uniform, thereby improving the cycle life of the battery cell;

[0089] ② Make the resistance of the conductive coating in the corner area greater than that in the straight area to solve the problem of lithium deposition at the corner.

[0090] Example 2

[0091] This embodiment provides a coating method for manufacturing the composite current collector in the above Example 1, which has the same beneficial effects.

[0092] See Figure 8 , the coating method includes the following steps:

[0093] S10: Provide a current collector substrate; wherein, the current collector substrate includes a coating area for manufacturing the current collector and a non-coating area for manufacturing the tab;

[0094] In this embodiment, the tab and the current collector are of an integral structure and are cut from the same current collector substrate. Therefore, when coating the current collector substrate, a non-coating area can be left at the edge position for subsequent cutting of the tab on the non-coating area.

[0095] S20: Coat a plurality of conductive coatings on the coating area such that the resistance of each of the conductive coatings gradually decreases in the direction away from the non-coating area;

[0096] It can be understood that the resistance of the conductive coating 3 can be changed by adjusting the thickness of the conductive coating 3, or the mass ratio of the conductive agent in the conductive coating 3, or the type of the conductive agent in the conductive coating 3. Considering the convenience of resistance adjustment, preferably, the resistance of the conductive coating 3 is adjusted by adjusting the mass ratio of the conductive agent in the conductive coating 3. It should be noted that the resistance of the conductive coating 3 can be measured by a film resistance meter.

[0097] In this embodiment, the resistance of each conductive coating is adjusted by controlling the content of the conductive agent in the conductive coating. Specifically, S20 includes:

[0098] S201a: Prepare a number of conductive pastes with different resistances; wherein, the content and / or type of the conductive agent in each of the conductive pastes are different;

[0099] S202a: Coat each of the conductive pastes at a preset position in the coating area, so that the resistance of each of the conductive pastes gradually decreases in a direction away from the tab;

[0100] S203a: Dry the conductive paste into a conductive coating.

[0101] In some other embodiments, the resistance of each conductive coating can also be adjusted by controlling the coating thickness of the conductive coating. Specifically, S20 includes:

[0102] S201b: Prepare a conductive paste;

[0103] S202b: Coat the conductive paste with different thicknesses at different positions in the coating area, so that the resistance of each of the conductive pastes gradually decreases in a direction away from the tab;

[0104] S203b: Dry the conductive paste into a conductive coating.

[0105] In this embodiment, the conductive paste contains 25% - 65% by mass of a conductive agent, 35% - 75% of a binder, and the remaining solvent; the ratio of the conductive agent to the binder can be adjusted according to the resistance of the conductive coating and the bonding effect in actual applications. The solid content of the conductive paste is 15% - 30%, and the viscosity of the conductive paste is 100 mPa·s - 300 mPa·s. The thickness of the conductive coating is 0.5 um - 5 um, and the specific value can be any one of 0.5 um, 0.8 um, 1 um, 1.5 um, 2 um, 2.6 um, 2.9 um, 3.4 um, 3.8 um, 4.6 um, and 5 um. Of course, the thickness of this conductive coating 3 still needs to be adjusted considering the resistance of the conductive coating 3 and the manufacturing process ability of the conductive coating 3.

[0106] Further, the conductive agent may be one or more of conductive carbon black, conductive graphite, carbon nanofiber conductive agent, carbon nanotubes, and graphene; the binder may be one or more of water-based binders such as polyvinyl alcohol, polyacrylic acid, polyacrylate, polystyrene sulfonate, and sodium carboxymethylate, or may be one or more of oil-based binders such as polyurethane, polyvinylidene fluoride, epoxy resin, and vinyl acetate; the solvent may be one or more of water, ethanol, methanol, dichloromethane, and N-methylpyrrolidone according to the type of binder.

[0107] S30: Die-cut the non-coated area to form tabs.

[0108] It should be noted that when the composite current collector is used as a full-tab battery, the non-coated area may not be die-cut, and the entire non-coated area is used as a tab.

[0109] The coating method provided in this embodiment can coat a conductive coating with a gradually decreasing resistance in a direction away from the tab on the current collector substrate, thereby obtaining a composite current collector with good current density uniformity.

[0110] It should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0111] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite current collector, characterized in that, It includes a current collector (1) and a tab (2); The current collector (1) includes a first side face and a second side face that are oppositely arranged along the width direction of the current collector (1), and the tab (2) is connected to the first side face; Wherein, a plurality of conductive coatings (3) are coated on the current collector (1), the plurality of conductive coatings (3) are sequentially arranged along the width direction of the current collector (1), and the resistance of the plurality of conductive coatings (3) gradually decreases in the direction away from the tab (2); The number of the conductive coatings (3) is n; the distance from the center point of the x-th conductive coating (3) to the first side face is L x , and the coating resistance of the x-th conductive coating (3) is R x , then the following is satisfied: L x+1 / L x =R x / R x+1 ; Wherein, n is a natural number, and n≥2; x is a natural number, and x < n.

2. The composite current collector according to claim 1, wherein, The current collector (1) is a continuous and uncut whole.

3. The composite current collector according to claim 2, wherein, The current collector (1) includes a plurality of straight regions (101) and a plurality of corner regions (102), and the straight regions (101) and the corner regions (102) are alternately arranged along the winding direction of the current collector (1); the resistance of the part of each conductive coating (3) located in the corner region (102) is 25% - 65% greater than that of the part located in the straight region (101).

4. The composite current collector according to claim 3, wherein The resistance of the part of each conductive coating (3) located in the corner region (102) is 40% - 50% greater than that of the part located in the straight region (101).

5. The composite current collector according to claim 1, wherein The current collector (1) is a cut single piece.

6. The composite current collector according to claim 2 or 5, wherein The plurality of conductive coatings (3) extend linearly along the length direction of the current collector (1) on the current collector (1).

7. The composite current collector according to claim 5, wherein, The current collector (1) is divided into a plurality of coating regions by a plurality of arcs with the center point of the tab (2) as the center and different radii; the plurality of coating regions and the plurality of conductive coatings (3) are arranged in one-to-one correspondence.

8. The composite current collector according to claim 1, wherein, The current collector (1) and the tab (2) are of a welded connection structure, or the current collector (1) and the tab (2) are of an integrally formed structure.

9. The composite current collector according to claim 1, wherein The resistance value of the conductive coating (3) is changed by adjusting the thickness of the conductive coating (3) or the mass ratio of the conductive agent in the conductive coating (3) or the type of the conductive agent in the conductive coating (3).

10. A battery, characterized in that, It includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet is made of the composite current collector according to any one of claims 1 - 9.

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