Composite current collector, secondary battery, and electric device

Abstract

The utility model provides a composite current collector, a secondary battery and an electric device. The composite current collector comprises a base material, the base material is provided with an upper surface and a lower surface along the thickness direction, the upper surface is provided with a plurality of first grooves arranged at intervals, and the lower surface is provided with a plurality of second grooves arranged at intervals; wherein the first grooves and the second grooves are alternately arranged and extend along a first direction, and the first direction is the width direction of the base material; and the lithium supplementing layer is filled in the first groove and / or the second groove.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to composite current collectors, secondary batteries, and electrical devices. Background Art

[0002] In recent years, with the increasingly wide application range of secondary batteries, lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, and aerospace.

[0003] However, during the first charge and discharge process of a secondary battery, the active ions will decrease due to the formation of a solid electrolyte membrane, and the active ions will also be lost during subsequent cycling and storage processes. This is usually the main reason for the capacity decay of secondary batteries. How to further improve the electrochemical performance of secondary batteries remains a major problem in the industry. Summary of the Invention

[0004] In order to achieve the above object, the present application provides a composite current collector, a secondary battery, and an electrical device. The composite current collector of the present application can maintain its electron conduction function and load-bearing function, and can also provide a lithium supplement function, thereby improving the first Coulomb efficiency, mass energy density, and cycle performance of the battery.

[0005] The present application is achieved through the following technical solutions.

[0006] The first aspect of the present application provides a composite current collector, including:

[0007] a substrate, wherein the substrate has an upper surface and a lower surface along its thickness direction, and a plurality of first grooves arranged at intervals are provided on the upper surface, and a plurality of second grooves arranged at intervals are provided on the lower surface; the first grooves and the second grooves are alternately arranged and extend along a first direction, and the first direction is the width direction of the substrate; and

[0008] a lithium supplement layer, and the lithium supplement layer is filled in the first grooves and the second grooves. Thus, by alternately arranging grooves on the upper and lower surfaces of the substrate, the composite current collector of the present application can maintain the conductivity and tensile strength of the substrate itself, and effectively play the conductive role and load-bearing role; at the same time, by filling the lithium supplement layer in the first groove and / or the second groove, the composite current collector can also provide a good lithium supplement function, thereby improving the first Coulomb efficiency, mass energy density, and cycle performance of the battery.

[0009] In some embodiments, the spacing width between adjacent first grooves of the composite current collector of the present application is S1, and the width of the second groove is W2, where S1≥W2.

[0010] With this design, the influence of the first groove and the second groove on the substrate thickness alternates or intermittently, and thus the influence on the substrate strength alternates or intermittently, which is beneficial to maintaining the tensile strength of the substrate.

[0011] In some embodiments, the lithium supplement layer of the composite current collector of the present application is filled flush with the upper surface and / or the lower surface of the substrate. With this design, the obtained composite current collector has a flat surface, which is beneficial to the subsequent setting of other functional layers thereon.

[0012] In some embodiments, a functional layer is further provided on the upper surface and / or the lower surface of the composite current collector of the present application. With this design, the functions of the composite current collector of the present application are further enriched.

[0013] In some embodiments, the lithium supplement layer and the functional layer of the composite current collector of the present application have the same composition, including: 40 wt% to 60 wt% of a lithium supplement agent relative to the total weight of the composition. With this design, it is beneficial to further improve the lithium supplement ability of the composite current collector of the present application, and setting the lithium supplement layer and the functional layer with the same composition is also further beneficial to the processing of the composite current collector of the present application.

[0014] In some embodiments, the thickness of the functional layer of the composite current collector of the present application is 2 μm to 10 μm. With this design, while further improving the lithium supplement ability of the composite current collector of the present application, it will not overly occupy the volume of the battery cell.

[0015] In some embodiments, the interval width S1 between adjacent first grooves of the composite current collector of the present application is 2 mm to 4 mm. By setting this interval width, it is beneficial to the processing of the groove and beneficial to maintaining the tensile strength of the substrate.

[0016] In some embodiments, the depths of the first groove and the second groove of the composite current collector of the present application are the same or different. The depths of the first groove and the second groove can be set to be the same or different as needed, so as to enrich its applications and be applicable to a variety of different scenarios.

[0017] In some embodiments, the depths of the first groove and the second groove of the composite current collector of the present application are 1 μm to 2 μm. By setting the depths of the first groove and the second groove within this range, while achieving the lithium supplement effect, the influence on the mechanical properties of the substrate is minimized.

[0018] In some embodiments, the width W1 of the first groove and the width W2 of the second groove of the composite current collector of the present application are the same or different. The widths of the first groove and the second groove can be set to be the same or different as needed, so as to enrich its applications and be applicable to a variety of different scenarios.

[0019] In some embodiments, the width W1 of the first groove and the width W2 of the second groove of the composite current collector of the present application are 1 mm to 2 mm. By setting the depths of the first groove and the second groove within this range, it is beneficial to facilitate processing using laser scribing.

[0020] The second aspect of the present application provides a secondary battery, including the composite current collector of the first aspect of the present application. The battery of the present application includes the composite current collector provided by the present application, and thus has at least the same advantages as the composite current collector.

[0021] The third aspect of the present application provides an electrical device, including the secondary battery of the second aspect of the present application. The electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery. Description of the Drawings

[0022] Figure 1A is a perspective view of a composite current collector according to an embodiment of the present application.

[0023] Figure 1B is a perspective view of a substrate according to an embodiment of the present application.

[0024] Figure 2 is a cross-sectional schematic view of a composite current collector according to another embodiment of the present application.

[0025] Figure 3 is a schematic view of a battery cell according to an embodiment of the present application.

[0026] Figure 4 is Figure 3 an exploded view of the battery cell shown in a specific embodiment of the present application.

[0027] Figure 5 is a schematic view of a battery module according to an embodiment of the present application.

[0028] Figure 6 is a schematic view of a battery pack according to an embodiment of the present application.

[0029] Figure 7 is Figure 6 an exploded view of the battery pack shown in a specific embodiment of the present application.

[0030] Figure 8 is a schematic view of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0031] Description of Reference Numerals:

[0032] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Shell; 52 Electrode assembly; 53 Top cover assembly; 6 Base material; 7 First groove; 8 Second groove; W1 Width of the first groove; W2 Width of the second groove; D1 Depth of the first groove; D2 Depth of the second groove; S1 Spacing width between adjacent first grooves; S2 Spacing width between adjacent second grooves; 9 Lithium supplement layer; 10 Functional layer. Detailed implementation manners

[0033] Hereinafter, embodiments of the composite current collector, secondary battery, and electrical device of the present application will be specifically disclosed in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0034] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present application.

[0037] If there is no special indication, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] If there is no special indication, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0039] If there is no special indication, all steps of the present application can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0040] If there is no special indication, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art.

[0041] If there is no special indication, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in the present application.

[0042] Lithium supplementation is also called "pre-lithiation" or "pre-lithium insertion", which is to add lithium into the battery to supplement lithium ions before the lithium-ion battery works. By pre-lithiating the electrode material to supplement lithium, the irreversible lithium loss is offset to improve the total capacity and energy density of the battery. At present, a variety of processes have been developed to supplement lithium to lithium-ion batteries. Among them, current collector lithium supplementation is an optional lithium supplementation method, but incorporating the lithium supplementing agent will bring problems in terms of adhesion, reliability, etc. of the current collector. Therefore, further improvement of current collector lithium supplementation is still needed.

[0043] Based on this, the present application proposes a composite current collector, a secondary battery and an electrical device.

[0044] Composite current collector

[0045] The first aspect of the present application provides a composite current collector, comprising:

[0046] A substrate, wherein the substrate has an upper surface and a lower surface along a thickness direction thereof, wherein a plurality of first grooves arranged at intervals are provided on the upper surface, and a plurality of second grooves arranged at intervals are provided on the lower surface; wherein the first grooves and the second grooves are alternately arranged and extend along a first direction, and the first direction is a width direction of the substrate; and

[0047] A lithium replenishing layer is filled in the first groove and / or the second groove.

[0048] In the present application, on the one hand, by alternately arranging grooves on the upper and lower surfaces of the substrate, that is, the grooves on the upper and lower surfaces are arranged completely staggered, so that the present application can maintain the original electronic function of the substrate while maintaining the mechanical properties of the original substrate, such as tensile strength, so that the electronic operation and bearing function can be effectively played; on the other hand, by arranging a lithium replenishing layer in the groove, the composite current collector provides a lithium replenishing function without occupying additional space, thereby improving the first coulomb efficiency, mass energy density and cycle performance of the battery. In addition, after playing the role of lithium replenishing, it is also beneficial for the electrolyte to flow into the groove, thereby improving the diffusion performance and wettability of the electrolyte.

[0049] Figure 1A is a perspective view of a composite current collector according to an embodiment of the present application. Figure 1A As shown, the composite current collector includes a substrate 6 and a lithium replenishing layer 9, wherein the substrate 6 has an upper surface and a lower surface along its thickness direction, a plurality of first grooves 7 arranged at intervals are provided on the upper surface, and a plurality of second grooves 8 arranged at intervals are provided on the lower surface. The first grooves 7 and the second grooves 8 are arranged alternately and extend along a first direction, wherein the first direction is the width direction of the substrate 6. The lithium replenishing layer 9 is filled in the first grooves 7 and / or the second grooves 8.

[0050] like Figure 1A and Figure 1BAs shown, the first grooves 7 are arranged at uniform intervals S1. Optionally, the interval S1 is from 2 mm to 4 mm, such as 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm or 4 mm. By setting this interval width, it is beneficial to the machining of the grooves and beneficial to maintaining the strength of the substrate. It should be understood that the plurality of first grooves 7 may also be arranged at non-uniform intervals.

[0051] In this embodiment, the second grooves 8 are arranged at uniform intervals S2. Optionally, the interval S2 is from 2 mm to 4 mm, such as 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm or 4 mm. It should be understood that the plurality of second grooves 8 may also be arranged at non-uniform intervals.

[0052] In addition, it should also be understood that the interval S1 and the interval S2 may be the same or different.

[0053] In this embodiment, the width W1 of the first groove 7 is the same as the width W2 of the second groove 8. Optionally, the width W1 and the width W2 are from 1 mm to 2 mm, such as 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2 mm. It should be understood that the width W1 of the first groove 7 and the width W2 of the second groove 8 may also be different.

[0054] Thus, in this application, the first groove 7 is located in the interval S2 between adjacent second grooves 8, or its width is exactly equal to the interval S2 between adjacent second grooves 8. Similarly, the first groove 7 is located in the interval between adjacent second grooves 8, or its width is exactly equal to the interval S1 between adjacent first grooves 7. The influence of the first groove and the second groove on the mechanical properties of the substrate is alternated or intermittent, so as to ensure the strength of the substrate itself and then maintain the strength of the composite current collector.

[0055] In this embodiment, the depth D1 of the first groove 7 is the same as the depth D2 of the second groove 8. Optionally, the depth D1 and the depth D2 are 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2 μm. It should be understood that the depth of the first groove 7 and the depth of the second groove 8 may also be different.

[0056] By setting the depths of the first groove 7 and the second groove 8 within this range, while achieving the effect of lithium compensation, the influence on the mechanical properties of the substrate is minimized.

[0057] In this embodiment, as Figure 1A shown, the lithium compensation layer 9 is filled flush with the surface of the corresponding thickness side of the substrate 6. That is, the thickness of the lithium compensation layer 9 is equal to the depth of the first groove 7 or the second groove 8, so that the lithium compensation layer 9 exactly fills the groove, facilitating the rolling of the lithium compensation layer 9 and the substrate 6 into a whole, so that the subsequent electrode active material layer will not fall off from the surface of the composite current collector, stabilizing the battery capacity. It should be understood that the lithium compensation layer may not completely fill the groove, thus providing a channel for the subsequent infiltration of the electrolyte.

[0058] In this embodiment, the width of the lithium compensation layer 9 is equal to the width W1 of the first groove 7 or the width W2 of the second groove 8.

[0059] In this embodiment, the lithium compensation layer 9 includes: a lithium compensating agent accounting for 40 wt% to 60 wt% of the total weight of the lithium compensation layer. There is no specific limitation on the lithium compensating agent as long as it can achieve the effect of lithium compensation in the battery system. For example, the lithium compensating agents that can be mentioned include binary lithium-rich additives such as Li3N, Li2O, Li2O2, Li2S, LiF, etc., or one or several of ternary lithium-rich additives such as Li2CO3, Li2C4O4 and Li5FeO4, Li6CoO4, Li2NiO2, Li2MoO3, Li2CuO2, Li6CoO4, etc.

[0060] In addition, the lithium compensation layer 9 further includes: a conductive agent accounting for 15 wt% to 30 wt% of the total weight of the lithium compensation layer. There is no specific limitation on the conductive agent as long as it can achieve the conductive effect in the battery system. For example, the conductive agents that can be mentioned include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, preferably one or two of conductive agents such as conductive carbon black, carbon nanotubes, graphene, conductive graphite, etc., and more preferably pure conductive carbon black is selected for use, making the process simple and the cost low.

[0061] The lithium supplement layer 9 further includes: 5 wt% to 20 wt% of a binder relative to the total weight of the lithium supplement layer. There is no specific limitation on the binder, as long as it can exert a binding effect in the battery system. For example, the binders that can be mentioned include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS), preferably polyvinylidene fluoride.

[0062] Figure 2 FIG. shows a cross-sectional schematic view of a composite current collector according to another embodiment of the present application. As Figure 2 shown, the composite current collector includes a substrate 6, a lithium supplement layer 9, and a functional layer 10. The substrate 6 has an upper surface and a lower surface along its thickness direction. A plurality of first grooves 7 are arranged at intervals on the upper surface, and a plurality of second grooves 8 are arranged at intervals on the lower surface. The first grooves 7 and the second grooves 8 are alternately arranged on the upper and lower surfaces and extend along a first direction, where the first direction is the width direction of the substrate 6. The lithium supplement layer 9 is filled in the first grooves 7 and the second grooves 8.

[0063] As Figure 2 shown, the first grooves 7 are arranged at a uniform interval S1. Optionally, the interval S1 is 2 mm to 4 mm, such as 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, or 4 mm. By setting this interval width, it is beneficial to the processing of the grooves and beneficial to maintaining the strength of the substrate. It should be understood that the plurality of first grooves 7 can also be arranged at non-uniform intervals.

[0064] In this embodiment, the second grooves 8 are arranged at a uniform interval S2. Optionally, the interval S2 is 2 mm to 4 mm, such as 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, or 4 mm. It should be understood that the plurality of second grooves 8 can also be arranged at non-uniform intervals.

[0065] In addition, it should also be understood that the intervals S1 and S2 may be the same or different.

[0066] In this embodiment, the width W1 of the first groove 7 is the same as the width W2 of the second groove 8. Optionally, the width W1 and the width W2 are from 1 mm to 2 mm, such as 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2 mm. It should be understood that the width W1 of the first groove 7 and the width W2 of the second groove 8 may also be different.

[0067] In this embodiment, the depth D1 of the first groove 7 is the same as the depth D2 of the second groove 8. Optionally, the depth D1 and the depth D2 are from 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2 μm. It should be understood that the depth of the first groove 7 and the depth of the second groove 8 may also be different.

[0068] By setting the depths of the first groove 7 and the second groove 8 within this range, while achieving the effect of lithium compensation, the influence on the mechanical properties of the substrate is minimized.

[0069] In this embodiment, as Figure 2 shown, the lithium compensation layer 9 is filled flush with the surface of the corresponding thickness side of the substrate 6. In this embodiment, the width of the lithium compensation layer 9 is equal to the width W2 of the first groove 7 or the second groove 8.

[0070] In this embodiment, the lithium supplement layer 9 includes: a lithium supplement agent accounting for 40 wt% to 60 wt% of the total weight of the lithium supplement layer. There is no specific limitation on the lithium supplement agent as long as it can exert a lithium supplement effect in the battery system. For example, the lithium supplement agents that can be mentioned include binary lithium-rich additives such as Li3N, Li2O, Li2O2, Li2S, LiF, etc., or one or several of ternary lithium-rich additives such as Li2CO3, Li2C4O4, Li5FeO4, Li6CoO4, Li2NiO2, Li2MoO3, Li2CuO2, Li6CoO4, etc. In addition, the lithium supplement layer 9 further includes: a conductive agent accounting for 15 wt% to 30 wt% of the total weight of the lithium supplement layer. There is no specific limitation on the conductive agent as long as it can exert a conductive effect in the battery system. For example, the conductive agents that can be mentioned include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, preferably one or two of conductive agents such as conductive carbon black, carbon nanotubes, graphene, conductive graphite, etc., and more preferably pure conductive carbon black is selected for use to make the process simple and the cost low. The lithium supplement layer 9 further includes: a binder accounting for 5 wt% to 20 wt% of the total weight of the lithium supplement layer. There is no specific limitation on the binder as long as it can exert a binding effect in the battery system. For example, the binders that can be mentioned include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS), and preferably polyvinylidene fluoride.

[0071] In this embodiment, as Figure 2 shown, a functional layer 10 is provided above the lithium supplement layer 9. The composition of the functional layer 10 is the same as that of the lithium supplement layer 9.

[0072] The setting of the functional layer 10 can further provide an excellent lithium supplement effect.

[0073] In some embodiments, the thickness of the functional layer of the composite current collector of the present application is 2 μm to 10 μm. Optionally, the thickness of the functional layer is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Through this design, while further improving the lithium supplement ability of the composite current collector of the present application, it will not occupy too much volume of the battery cell, and the functional layer and the substrate can be roll-pressed into an integral body, which is beneficial to improving the reliability of the composite current collector.

[0074] The cross-sectional shape of the groove in the present application along the width direction of the substrate may be other shapes suitable for processing, including but not limited to rectangular, U-shaped, V-shaped, etc.

[0075] In some embodiments, the substrate 6 may be a metal part, such as aluminum foil or aluminized part, copper foil, etc. Of course, the substrate 6 may also be other metal parts, such as stainless steel foil.

[0076] In some embodiments, considering its own stability and the impact on energy density, the thickness of the substrate 6, such as aluminum foil, is advantageously 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, and 10 μm. Using aluminum foil within this thickness range will be more beneficial to energy improvement.

[0077] Secondary battery

[0078] An embodiment of the present application also provides a secondary battery, including the composite current collector of the first aspect of the present application.

[0079] The term "secondary battery" mentioned herein refers to a battery cell, a battery module, or a battery pack. Explanations are given separately below.

[0080] Generally, a secondary battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0081] In some embodiments, the battery cell includes one of the above-mentioned composite current collectors, for example, the composite current collector of the present application is included in the positive electrode sheet. In some embodiments, the composite current collector of the present application is included in the negative electrode sheet. In some embodiments, the composite current collectors of the present application are included in both the positive electrode sheet and the negative electrode sheet.

[0082] Positive electrode sheet

[0083] The positive electrode sheet includes a positive current collector and a positive electrode film layer provided on at least one surface of the positive current collector. The positive current collector can adopt the composite current collector of the first aspect of the present application. It should be noted that, alternatively, when the negative current collector adopts the composite current collector of the present application, the corresponding positive current collector can also adopt a metal foil or other current collectors. For example, as the metal foil, aluminum foil can be used. Other current collectors can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. Other current collectors can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0084] Among them, the positive electrode film layer is provided on either one or both of the two opposite surfaces of the composite current collector.

[0085] In some embodiments, the positive electrode active material can adopt the positive electrode active materials known in the art for lithium-ion batteries. As an example, the positive electrode active material can include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM811 )), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2), and at least one of its modified compounds, etc. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0086] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0087] In some embodiments, the positive electrode film layer may also optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode sheet can be prepared by the following method: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0089] Negative electrode sheet

[0090] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0091] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0092] In some embodiments, the negative electrode current collector may be the composite current collector of the present application, or a metal foil or other current collector may be used. For example, as the metal foil, copper foil may be used. Other current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Other current collectors may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). It should be understood that in the present application, at least one of the positive electrode current collector and the negative electrode current collector is the composite current collector of the present application.

[0093] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries well-known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone, or two or more of them may be used in combination.

[0094] In some embodiments, the negative electrode film layer may also optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0095] In some embodiments, the negative electrode film layer may also optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0096] In some embodiments, the negative electrode film layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0097] In some embodiments, the negative electrode plate may be prepared in the following manner: the components for preparing the negative electrode plate described above, such as the negative electrode active material, conductive agent, binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0098] Electrolyte

[0099] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0100] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0101] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0102] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0103] In some embodiments, the electrolytic solution may also optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0104] Separator

[0105] In some embodiments, the battery cell further includes a separator. There is no particular limitation on the type of separator in this application, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0106] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0107] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0108] In some embodiments, a battery cell may include an outer package. The outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0109] In some embodiments, the outer package of the battery cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the battery cell may also be a soft package, such as a pouch soft package. The material of the soft package may be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. may be cited.

[0110] This application does not particularly limit the shape of the battery cell, and it may be cylindrical, square, or any other arbitrary shape. For example, Figure 3 is a battery cell 5 with a square structure as an example.

[0111] In some embodiments, referring to Figure 4 , the outer package may include a housing 51 and a top cover assembly 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art can select according to specific actual needs.

[0112] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0113] Figure 5 is a battery module 4 as an example. Referring to Figure 5 , in the battery module 4, a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0114] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0115] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0116] Figure 6 and Figure 7This is the battery pack 1 as an example. Refer to Figure 6 and Figure 7 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0117] The battery of the present application includes the composite current collector provided by the present application, and thus has at least the same advantages as the composite current collector.

[0118] Power-consuming device

[0119] In addition, the present application also provides a power-consuming device, and the power-consuming device includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the power-consuming device or as the energy storage unit of the power-consuming device. The power-consuming device may include mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0120] As the power-consuming device, battery cells, battery modules or battery packs can be selected according to its usage requirements.

[0121] Figure 8 This is the power-consuming device as an example. The power-consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the power-consuming device for high power and high energy density of the secondary battery, a battery pack or a battery module can be adopted.

[0122] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinning, and battery cells can be used as the power source.

[0123] The power-consuming device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery.

[0124] Embodiment

[0125] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those not specified in the embodiments regarding specific technologies or conditions, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchases.

[0126] Embodiment 1

[0127] (1) Preparation of composite current collector

[0128] Step 1: Take an aluminum foil with a thickness of 10 μm, and etch the first grooves 7 (width 2 mm, depth 1.5 μm) with a spacing of 3 mm and the second grooves 8 (width 2 mm, depth 1.5 μm) with a spacing of 3 mm on the upper and lower surfaces by means of laser grooving.

[0129] Step 2: Prepare the lithium supplement slurry: Mix Li3N (lithium supplement agent), conductive carbon black (conductive agent) and polyvinylidene fluoride (binder) in a mass ratio of 60:25:15, and add N-methylpyrrolidone solvent and stir to form a lithium supplement slurry with a solid content of 55%.

[0130] Step 3: Filling of the lithium supplement layer slurry: Fill the lithium supplement layer slurry onto the first and second grooves obtained in Step 1, and then perform cold pressing. After multiple fillings and cold pressings, finally make the upper and lower surfaces of the lithium supplement layer flush with the substrate to obtain a composite current collector (as Figure 1A shown).

[0131] (2) Preparation of secondary battery

[0132] 1) Positive electrode plate

[0133] According to the mass ratio of LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent super-P, carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) being 96.5:1.5:0.5:1.5, fully stir and mix evenly in N-methylpyrrolidone (NMP), then prepare the positive electrode slurry, and then coat the positive electrode slurry on the composite current collector. After vacuum drying at 120 °C, cold pressing, cutting and slitting, the positive electrode plate is obtained.

[0134] 2) Negative electrode plate

[0135] Mix the active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 95:2:2:1, fully stir and mix evenly in a deionized water solvent system, and then coat it on the Cu foil, dry and cold press to obtain the negative electrode plate.

[0136] 3) Electrolyte

[0137] Mix ethylene carbonate and diethyl carbonate in a mass ratio of 3:7, add lithium hexafluorophosphate (LiPF6), and fully dissolve to prepare 1 mol / L LiPF6 as the electrolyte.

[0138] 4) Separator

[0139] Use a polypropylene separator with a thickness of 12 μm as the separator film.

[0140] 5) Preparation of secondary battery

[0141] Place the prepared positive electrode sheet and negative electrode sheet in order, with the separator film in the middle of the positive electrode sheet and the negative electrode sheet to play a separating role, and then wind them to obtain an electrode assembly; place the electrode assembly in the outer package, inject the electrolyte after drying, and obtain the secondary battery through processes such as vacuum packaging, standing, formation, and aging.

[0142] Example 2

[0143] Example 2 is carried out in the same method as Example 1, except that: after step 3, a lithium supplement slurry is further coated on the surface of the obtained composite current collector to obtain a functional layer 10 with a thickness of 4 μm (as Figure 2 shown).

[0144] Comparative Example 1

[0145] Comparative Example 1 is carried out in the same method as Example 1, except that grooves are provided only on one side of the substrate 6.

[0146] Comparative Example 2

[0147] Comparative Example 2 is carried out in the same method as Example 1, except that an aluminum foil with a thickness of 10 μm is taken, and first grooves 7 (2 mm wide and 1.5 μm deep) with a spacing of 3 mm and second grooves 8 (2 mm wide and 1.5 μm deep) with a spacing of 3 mm are etched on the upper and lower surfaces by laser grooving, but the first grooves 7 on the upper surface of the substrate and the second grooves 8 on the lower surface of the substrate are arranged with a cross of 0.5 mm.

[0148] Mechanical property test of composite current collector

[0149] Test method:

[0150] Use a sampling die to cut the composite current collectors of Examples 1-2 and Comparative Examples 1-2 to obtain test samples with a length of 200 mm and a width of 15 mm respectively. Clamp the test samples on the tensile machine fixture, control the distance between the upper and lower fixtures to be 100 mm, start the tensile machine, and start the test until the aluminum foil is broken;

[0151] Among them, the tensile strength = maximum tensile force / (sample width * aluminum foil thickness), and the unit is MPa. The results are shown in Table 1 below.

[0152] Performance test of positive electrode sheet

[0153] Peel strength test

[0154] Refer to the national standard GB-T 2790-1995 "Test Method for 180° Peel Strength of Adhesives". Use a blade to cut a specimen with a width of 30 mm and a length of 100 - 160 mm. Stick the special double-sided tape on the steel plate, with the tape width of 20 mm and length of 90 - 150 mm. Stick the positive film side of the previously cut electrode specimen on the double-sided tape, and then roll it three times in the same direction with a 2 kg roller. Fix a paper tape with the same width as the electrode and a length of 250 mm on the electrode current collector, and fix it with crepe glue. Turn on the power of the Sansi tensile machine (sensitivity is 1 N), the indicator light is on, adjust the limit block to the appropriate position, and fix the end of the steel plate without the electrode with the lower clamp. Fold the paper tape upwards and fix it with the upper clamp, and adjust the position of the upper clamp using the "up" and "down" buttons on the manual controller attached to the tensile machine. Then conduct the test and read the value, with the unit of N / m. The results are shown in Table 1 below.

[0155] Diaphragm Resistance Test

[0156] Under a test pressure of 5 Mpa, use a diaphragm resistivity tester to measure the diaphragm resistance of Examples 1 - 2 and Comparative Examples 1 - 2, with the unit of Ω*cm. The results are shown in Table 1 below.

[0157] Secondary Battery Performance Test

[0158] Initial Efficiency Test

[0159] At 45℃, the secondary battery prepared in Example 1 is formed. It is charged at a constant current of 0.02C for 10 h (record the charging capacity C0 at this time). At 25℃, the secondary battery is discharged at a constant current of 0.2C to 2.0V, and record the discharge capacity D0 at this time. Then it is charged at a constant current of 0.33C to 3.8V, and then charged at a constant voltage until the current is 0.05C, and record the charging capacity as C1 at this time. It is discharged at a constant current of 0.33C to 2.5V, left standing for 5 min, then discharged at a constant current of 0.33C to 2.0V, and then discharged at a constant current of 0.1C to 2.0V, and record the discharge capacity as D1 at this time.

[0160] The initial Coulomb efficiency (%) of the secondary battery = D1 / (C0 - D0 + C1).

[0161] Energy Density Calculation

[0162] At 25℃, the battery is fully charged at a rate of 0.33C and fully discharged at a rate of 0.33C. After three charge-discharge cycles, record the discharge energy D0.

[0163] At 25℃, use an electronic balance to weigh the battery to obtain the mass M of the battery.

[0164] Take the ratio of D0 to M as the mass energy density of the battery.

[0165] Cycling performance

[0166] The first charge and discharge were carried out in an environment of 25 °C. Constant current charging was carried out at a charging current of 1C until the upper limit voltage was reached and then changed to constant voltage charging. Then, constant current discharging was carried out at a discharging current of 1C until the discharging cut-off voltage, and the discharging capacity of the first cycle was recorded. Then, 800 charge and discharge cycles were carried out, and the discharging capacity of the 800th cycle was recorded.

[0167] Cycling capacity retention rate (%) = (Discharging capacity of the 800th cycle / Discharging capacity of the first cycle) × 100%.

[0168] Table 1. Test results of Examples 1 to 2 and Comparative Examples 1 to 2

[0169]

[0170] Thus, by providing grooves on the original substrate, the composite current collector of the present application can effectively maintain the electron conduction function of the current collector substrate itself. By providing grooves that are staggered up and down, the mechanical strength of the current collector can be effectively maintained. At the same time, by filling the grooves with a lithium supplement layer, the first Coulomb efficiency, mass energy density, and cycling performance of the battery are effectively improved under the above conditions.

[0171] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector, characterized in that, Comprising: a base material, wherein the base material has an upper surface and a lower surface along its thickness direction, and a plurality of first grooves arranged at intervals are provided on the upper surface, and a plurality of second grooves arranged at intervals are provided on the lower surface; wherein the first grooves and the second grooves are arranged alternately and extend along a first direction, and the first direction is the width direction of the base material; and a lithium compensation layer, and the lithium compensation layer is filled in the first grooves and / or the second grooves.

2. The composite current collector according to claim 1, wherein The spacing width S1 between adjacent first grooves is S1, and the width of the second groove is W2, wherein S1≥W2.

3. The composite current collector according to claim 1 or 2, characterized in that, The lithium compensation layer is filled flush with the upper surface and / or the lower surface of the base material.

4. The composite current collector according to claim 3, wherein On the upper surface and / or the lower surface, a functional layer is further provided.

5. The composite current collector according to claim 4, wherein The lithium compensation layer and the functional layer have the same composition, including: 40 wt% to 60 wt% of a lithium compensation agent relative to the total weight of the composition.

6. The composite current collector according to claim 4 or 5, characterized in that, The thickness of the functional layer is 2 μm to 10 μm.

7. The composite current collector according to any one of claims 1 to 6, characterized in that The spacing width S1 between adjacent first grooves is 2 mm to 4 mm.

8. The composite current collector according to any one of claims 1 to 7, characterized in that, The depth D1 of the first groove and the depth D2 of the second groove are the same or different.

9. The composite current collector according to any one of claims 1 to 8, characterized in that The depth D1 of the first groove and the depth D2 of the second groove are 1 μm to 2 μm.

10. The composite current collector according to any one of claims 1 to 9, characterized in that, The width W1 of the first groove and the width W2 of the second groove are the same or different.

11. The composite current collector according to any one of claims 1 to 10, characterized in that, The width W1 of the first groove and the width W2 of the second groove are 1 mm to 2 mm.

12. A secondary battery, comprising the composite current collector according to any one of claims 1 to 11.

13. An electrical device, comprising the secondary battery according to claim 12.

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