A current collector, a pole piece, a battery, a battery pack, and an electric device

Abstract

The application provides a current collector, a pole piece, a battery, a battery pack and a power utilization device. The current collector comprises a current collector base and a conductive layer. The conductive layer is arranged on at least one surface of the current collector base in the thickness direction. The conductive layer has a concave-convex structure away from the first surface of the current collector base. The current collector can reduce the impedance of the battery and effectively improve the cycle performance of the battery by arranging the concave-convex structure on the conductive layer.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a current collector, electrode, battery, battery pack, and electrical device. Background Technology

[0002] Secondary batteries are widely used in new energy vehicles and portable electronic devices due to their advantages such as high energy density and wide temperature range adaptability. Currently, the electrodes of secondary batteries are mainly composed of current collectors and active layers. However, due to the poor interfacial compatibility between the current collector and the active layer, the contact resistance between the two is high, resulting in a large overall impedance of the battery.

[0003] Currently, to reduce the interfacial contact resistance between the current collector and the active layer, a common strategy is to apply a carbon coating to the surface of the current collector. This carbon coating enhances the interfacial compatibility between the current collector and the active layer, thereby effectively reducing the battery impedance. However, the application of the carbon coating leads to a decrease in the battery's cycle performance, making it difficult to meet the increasingly demanding requirements for battery cycle performance. Summary of the Invention

[0004] This application provides a current collector with a special structure that can reduce battery impedance and effectively improve battery cycle performance.

[0005] This application also provides a method for preparing a current collector, used to achieve the preparation of the above-mentioned current collector.

[0006] This application also provides an electrode comprising the aforementioned current collector, which helps to reduce the impedance of the battery and improve the cycle performance of the battery.

[0007] This application also provides a battery that includes the aforementioned electrodes, thus exhibiting excellent cycle performance.

[0008] This application also provides a battery pack comprising at least two of the aforementioned batteries, thus exhibiting excellent cycle performance.

[0009] This application also provides an electrical device that includes the aforementioned battery or battery pack, thus having a longer standby time.

[0010] This application provides a current collector, including a current collector substrate and a conductive layer, wherein the conductive layer is disposed on at least one surface of the current collector substrate along the thickness direction, and the first surface of the conductive layer away from the current collector substrate has an uneven structure.

[0011] As described above, the first surface is provided with a raised structure that protrudes from the first surface in the thickness direction; and / or, the first surface is provided with a recessed structure that is lower than the first surface in the thickness direction.

[0012] As described above, the first surface is provided with N protruding structures, and the N protruding structures are arranged in an array along the extension direction of the first surface, where N≥2; and / or, the first surface is provided with M recessed structures, and the M recessed structures are arranged in an array along the extension direction of the first surface, where M≥2.

[0013] As described above, the current collector has a raised structure that is a strip structure, with N raised structures extending along a first direction and arranged in an array along a second direction, the first and second directions intersecting each other and both parallel to the first surface; and / or, the recessed structure has a strip structure, with M recessed structures extending along a first direction and arranged in an array along a second direction, the first and second directions intersecting each other and both parallel to the first surface.

[0014] As described above, the current collector has the recessed structure and the raised structure arranged alternately at intervals.

[0015] As described above, in the direction parallel to the first surface, the distance between the highest points of two adjacent protruding structures is 1-5µm; and / or, in the direction parallel to the first surface, the distance between the lowest points of two adjacent recessed structures is 1-5µm.

[0016] As described above, in the current collector, the height of the protrusion in the protrusion structure is 1-3 μm; and / or, the depth of the depression in the depression structure is 1-3 μm.

[0017] As described above, in the current collector, the outer wall surface of the protrusion in the protrusion structure is an arc surface; and / or, the inner wall surface of the recess in the recess structure is an arc surface.

[0018] As described above, in the current collector, the outer wall surface of the protrusion in the protrusion structure is a plane, and the angle between the extending direction of the side wall surface of the protrusion and the length direction of the current collector matrix is ​​2-85°; and / or, in the recessed structure, the inner wall surface of the recess is a plane, and the angle between the extending direction of the side wall surface of the recess and the length direction of the current collector matrix is ​​2-85°.

[0019] As described above, the current collector has a conductive layer thickness of 1-30 μm; and / or, the conductive layer comprises a conductive agent and a binder, wherein the conductive agent accounts for 20-99% of the mass of the conductive layer.

[0020] The method for preparing the current collector as described above includes the following steps:

[0021] The current collector is obtained by scraping and vibrating a conductive agent slurry located on at least one surface of the current collector substrate.

[0022] This application also provides an electrode, comprising a current collector as described in any of the above claims or a current collector obtained by the above preparation method and an active layer; the active layer is disposed on a first surface of the conductive layer, and the surface of the active layer facing the first surface has a mating structure adapted to the concave-convex structure.

[0023] This application also provides a battery including the aforementioned electrode.

[0024] This application also provides a battery pack comprising at least two of the aforementioned batteries.

[0025] This application also provides an electrical device, including the battery or battery pack described above.

[0026] The current collector provided in this application, by setting a current collector substrate and a conductive layer, can reduce the contact resistance between the current collector and the active layer, thereby reducing the battery impedance. Moreover, by setting an uneven structure on the surface of the conductive layer away from the current collector substrate, the adhesion strength between the current collector and the positive electrode active layer can be increased, thereby increasing the peel strength of the electrode and effectively improving the cycle performance of the battery. Attached Figure Description

[0027] Figure 1 This is a side view of a current collector substrate provided in an embodiment of this application;

[0028] Figure 2 A side view of a current collector structure provided in an embodiment of this application. Figure 1 ;

[0029] Figure 3 A side view of a current collector structure provided in an embodiment of this application. Figure 2 ;

[0030] Figure 4 A side view of a current collector structure provided in an embodiment of this application. Figure 3 ;

[0031] Figure 5 A side view of a current collector structure provided in an embodiment of this application. Figure 4 ;

[0032] Figure 6 A side view of a current collector structure provided in an embodiment of this application. Figure 5 ;

[0033] Figure 7 A top view of a current collector structure provided in an embodiment of this application. Figure 1 ;

[0034] Figure 8 A top view of a current collector structure provided in an embodiment of this application. Figure 2 ;

[0035] Figure 9 A top view of a current collector structure provided in an embodiment of this application. Figure 3 ;

[0036] Figure 10 A top view of a current collector structure provided in an embodiment of this application. Figure 4 ;

[0037] Figure 11 A top view of a current collector structure provided in an embodiment of this application. Figure 5 ;

[0038] Figure 12 A side view of a current collector structure provided in an embodiment of this application. Figure 6 ;

[0039] Figure 13 A side view of a current collector structure provided in an embodiment of this application. Figure 7 ;

[0040] Figure 14 A side view of a current collector structure provided in an embodiment of this application. Figure 8 ;

[0041] Figure 15 A side view of a current collector structure provided in an embodiment of this application. Figure 9 ;

[0042] Figure 16 A side view of a current collector structure provided in an embodiment of this application. Figure 10 ;

[0043] Figure 17 A side view of a current collector structure provided in an embodiment of this application. Figure 10 one;

[0044] Figure 18 A side view of an electrode structure provided in an embodiment of this application;

[0045] Figure 19 A side view of a current collector structure provided in an embodiment of this application. Figure 10 two;

[0046] Figure 20 A top view of a current collector structure provided in an embodiment of this application. Figure 6 ;

[0047] Figure 21 A side view of a current collector structure provided in an embodiment of this application. Figure 10 three. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] By setting a conductive layer on the surface of the current collector, the contact resistance between the current collector and the active layer can be reduced, thereby reducing the battery impedance. However, during long-term cycling, the battery capacity retention is low, and the impedance increases again. The inventors analyzed this phenomenon and found that the weakest peeling surface of the electrode is located between the conductive layer and the active layer. During battery cycling, the conductive layer and the active layer are prone to peeling, which further increases the battery impedance and limits the battery's cycle performance.

[0050] Based on this, this application provides a current collector, including a current collector substrate and a conductive layer, wherein the conductive layer is disposed on at least one surface of the current collector substrate along the thickness direction, and the first surface of the conductive layer away from the current collector substrate has an uneven structure.

[0051] It is worth mentioning that the current collector in this application can be a positive current collector, in which case the current collector substrate can be at least one of aluminum foil and nickel foil. The current collector in this application can also be a negative current collector, in which case the current collector substrate can be at least one of copper foil, nickel foam and copper foam.

[0052] The conductive layer of this application is a structure that can conduct electrons. This application does not limit the specific composition of the conductive layer. It can be a combination of conductive agents and binders commonly used in the art. For example, the conductive agent can be at least one of carbon black, graphene and carbon nanotubes, and the binder can be at least one of PVP, CMC and PAA. The mass ratio of conductive agent to binder can be 60:0.5~110.

[0053] The current collector substrate of this application has two surfaces in the thickness direction, such as Figure 1 As shown, the current collector substrate 1 has a surface 1a and a surface 1b along the thickness direction A. A conductive layer can be disposed on one surface of the current collector substrate 1 along the thickness direction A, such as... Figure 2 As shown, the conductive layer 2 is disposed on surface 1a of the current collector substrate 1. The conductive layer can also be disposed on both surfaces of the current collector substrate 1 along the thickness direction A, such as... Figure 3 As shown, the conductive layer 2 is disposed on the surfaces 1a and 1b of the current collector substrate.

[0054] like Figure 2 and Figure 3As shown, the conductive layer 2 has an uneven structure on its first surface 2a away from the current collector substrate 1. The uneven structure in this application refers to the fact that the first surface 2a is not smooth, having depressions and protrusions.

[0055] The first surface 2a of the current collector in this application has an uneven structure. The presence of this uneven structure can increase the contact area between the conductive layer 2 and the active layer, and make the conductive layer 2 and the active layer tightly bonded through the interlocking structure, thereby enhancing the peel strength of the electrode and making the active layer less likely to peel off during battery cycling, thereby improving the battery's resistance stability and cycle performance.

[0056] like Figure 4 As shown, in one specific embodiment, a protruding structure 3 is provided on the first surface 2a, and the protruding structure 3 protrudes from the first surface 2a in the thickness direction A. At this time, a recess 3a is formed between two adjacent protruding structures 3, and the protruding structure 3 and the recess 3a together form a convex-concave structure.

[0057] like Figure 5 As shown, in one specific embodiment, the first surface 2a is provided with a recessed structure 4. In the thickness direction A, the lowest point of the recessed structure 4 is lower than the first surface 2a. At this time, a protrusion 4a is formed between two adjacent recessed structures 4, and the recessed structure 4 and the protrusion 4a together form a concave-convex structure.

[0058] like Figure 6 As shown, in one specific embodiment, the first surface 2a is provided with a recessed structure 4 and a raised structure 3. In the thickness direction A, the lowest point of the recessed structure 4 is lower than the first surface 2a, and the raised structure 3 protrudes from the first surface 2a. The recessed structure 4 and the raised structure 3 together form a concave-convex structure.

[0059] like Figure 7 As shown, in one specific embodiment, the first surface 2a is provided with N protrusions 3, which are arranged in an array along the extension direction of the first surface 2a, where N ≥ 2. This application does not limit the shape of the protrusions 3; 3A, 3B, 3C, and 3D represent protrusions 3 of different shapes, which are arranged in an array along the extension direction of the first surface 2a.

[0060] like Figure 8 As shown, in one specific embodiment, the first surface 2a is provided with M recessed structures 4, which are arranged in an array along the extension direction of the first surface 2a, where M ≥ 2. This application does not limit the shape of the recessed structures; 4A, 4B, 4C, and 4D represent recessed structures 4 of different shapes, which are arranged in an array along the extension direction of the first surface 2a.

[0061] like Figure 9As shown, in one specific embodiment, the protrusion structure 3 is a strip structure, and N protrusion structures 3 extend along the first direction B and are arranged in an array along the second direction C. The first direction B and the second direction C intersect each other and are all parallel to the first surface 2a.

[0062] This application does not limit the specific directions of the first direction B and the second direction C. Figure 9 In the figure, the first direction B is the length direction of the current collector substrate 1, and the second direction C is the width direction of the current collector substrate 1.

[0063] exist Figure 10 In the figure, the first direction B and the second direction C form certain angles with the length direction and the width direction of the current collector substrate 1, respectively. Among them, N protrusion structures 3 extend along the first direction B and are arranged in an array along the second direction C.

[0064] Furthermore, this application does not limit the dimensions of the strip structures in the extension direction, and they can extend arbitrarily in the first direction. Simultaneously, the dimensions of the N strip structures in the extension direction can be the same or different from each other. For example... Figure 9 As shown, the five strip structures are identical in size along their extension direction; as Figure 10 As shown, the seven strip structures have different dimensions in the direction of extension.

[0065] like Figure 11 As shown, in one specific embodiment, the recessed structure 4 is a strip structure, and M recessed structures 4 extend along the first direction B and are arranged in an array along the second direction C. The first direction and the second direction intersect each other and are all parallel to the first surface 2a.

[0066] This application does not limit the specific directions of the first direction B and the second direction C. Figure 11 In the figure, the first direction B is the length direction of the current collector substrate 1, and the second direction C is the width direction of the current collector substrate 1.

[0067] As mentioned above, the first direction B and the second direction C can also form certain angles with the length direction and width direction of the current collector substrate 1, respectively. Among them, the M recessed structures 4 extend along the first direction B and are arranged in an array along the second direction C.

[0068] Furthermore, this application does not limit the dimensions of the strip structures in the extension direction, and they can extend arbitrarily in the first direction. Simultaneously, the dimensions of the M strip structures in the extension direction can be the same or different from each other. For example... Figure 11 As shown, the five strip structures have the same dimensions in the extension direction; as mentioned earlier, the dimensions of the strip structures in the extension direction can also be different.

[0069] like Figure 6As shown, in one specific embodiment, recessed structures and raised structures are alternately arranged, with recessed structures 4 and raised structures 3 arranged alternately on the first surface 2a. That is, the first surface 2a is simultaneously provided with recessed structures 4 and raised structures 3, and in the arrangement direction of the recessed structures 4 and raised structures 3, the recessed structures 4 and raised structures 3 are alternately arranged.

[0070] In a specific embodiment of this application, the distance between the highest points of two adjacent protrusions 3 in a direction parallel to the first surface 2a is 1-5 μm.

[0071] It should be noted that the spacing refers to the minimum distance between the highest points of two adjacent protrusions 3. For example... Figure 4 As shown, when the heights of the N protrusions 3 are the same, the distance between the highest points of two adjacent protrusions 3 in the direction parallel to the first surface 2a is L1; Figure 12 As shown, when the heights of the N protrusions 3 are different, L1 in the direction parallel to the first surface 2a is the distance between the highest points of two adjacent protrusions 3. The distance L1 between the adjacent highest points of the N protrusions 3 in this application can be the same or different. When different, all N protrusions 3 can be located within this range.

[0072] In detail, when the spacing L1 between the highest points of the protrusion structure 3 is controlled within the above range, a more effective interlocking structure can be formed between the active layer and the conductive layer 2, further improving the peel strength of the electrode.

[0073] In a specific embodiment of this application, the distance between the lowest points of two adjacent recessed structures 4 in a direction parallel to the first surface 2a is 1-5 μm.

[0074] It should be noted that the spacing refers to the minimum distance between the lowest points of two adjacent recessed structures 4. For example... Figure 5 As shown, when the depths of the M recessed structures 4 are the same, the distance between the lowest points of two adjacent recessed structures 4 in the direction parallel to the first surface 2a is L2; Figure 13 As shown, when the depths of the M recessed structures 4 are different, L2 in the direction parallel to the first surface 2a is the distance between the lowest points of two adjacent recessed structures 4. As mentioned above, the distance L2 between the adjacent lowest points of the M recessed structures 4 in this application can be the same or different. When they are different, all M recessed structures 4 can be located within this range.

[0075] In detail, when the spacing L2 between the lowest points of the recessed structure 4 is within the above range, a more effective interlocking structure can be formed between the active layer and the conductive layer 2, and the peel strength of the electrode can be further improved.

[0076] In a specific embodiment of this application, the height of the protrusion in the protrusion structure 3 is 1-3 μm.

[0077] In detail, such as Figure 4 As shown, the height of the protrusion refers to the distance between the highest point of the protrusion structure 3 and the first surface 2a in the thickness direction A, which is H1. When the height H1 of the protrusion is within the above-mentioned range, the interlocking structure between the active layer and the conductive layer 2 is more compact, and the specific capacity performance of the battery can be further improved. As mentioned above, the height H1 of the N protrusion structures 3 in this application can be the same or different. When they are different, all N protrusion structures 3 can be located within this range.

[0078] In a specific embodiment of this application, the depth of the recess in the recess structure 4 is 1-3 μm.

[0079] In detail, such as Figure 5 As shown, the depth of the recess refers to the distance between the lowest point of the recessed structure 4 and the first surface 2a in the thickness direction A, which is H2. When the depth H2 of the recess is within the above range, the interlocking structure between the active layer and the conductive layer 2 is tighter, and the adhesion between the conductive layer 2 and the current collector substrate can be further improved. As mentioned above, the depths of the recesses in the M recessed structures 4 of this application can be the same or different. When they are different, all M recessed structures 4 can be located within this range.

[0080] like Figure 14 As shown, in one specific embodiment, the outer wall surface 3x of the protrusion in the protrusion structure 3 is an arc surface.

[0081] Specifically, the geometric characteristics of the raised arc surface can disperse the stress concentration at the interface between the conductive layer 2 and the active layer, further reducing the risk of local peeling of the electrode.

[0082] like Figure 15 As shown, in one specific embodiment, the inner wall surface 4x of the recessed structure 4 is an arc surface.

[0083] Specifically, the geometric characteristics of the concave arc surface can disperse the stress concentration at the interface between the conductive layer 2 and the active layer, further reducing the risk of local peeling of the electrode.

[0084] like Figure 16 As shown, in one specific embodiment, the outer wall surface 3x of the protrusion in the protrusion structure 3 is a plane, and the angle β1 between the extension direction of the side wall of the protrusion and the length direction of the current collector substrate 1 is 2-85°.

[0085] In detail, when the included angle β1 is within the above range, a more stable interlocking structure can be formed between the active layer and the conductive layer 2, further improving the peel strength of the electrode.

[0086] like Figure 17 As shown, in one specific embodiment, the inner wall surface 4x of the recessed structure 4 is a plane, and the angle β2 between the extension direction of the side wall surface of the recess and the length direction of the current collector substrate 1 is 2-85°.

[0087] In detail, when the included angle β2 is within the above range, a more stable intercalation structure can be formed between the active layer and the conductive layer 2, further improving the peel strength of the electrode.

[0088] In a specific embodiment of this application, the thickness of the conductive layer 2 is 1-30 μm.

[0089] Specifically, such as Figure 5 As shown, the thickness H3 of the conductive layer 2 refers to the distance between the highest point of the conductive layer 2 and the current collector surface 1a. When the thickness of the conductive layer 2 is controlled within the above range, the electrode can maintain better stability during battery cycling, thereby further improving the safety performance of the battery.

[0090] In a specific embodiment of this application, the conductive layer 2 includes a conductive agent and a binder, wherein the conductive agent accounts for 20-99% of the mass of the conductive layer 2. For example, the conductive layer 2 may be composed of carbon black, PVP and CMC in a mass ratio of 12:1:1.

[0091] Specifically, when the mass ratio of the conductive agent in the conductive layer 2 is controlled within the above range, the conductivity and adhesion of the conductive layer 2 can be more compatible, and the cycle performance of the battery can be better.

[0092] This application also improves a method for preparing the aforementioned current collector, comprising the following steps:

[0093] A current collector is obtained by scraping and vibrating a conductive agent slurry located on at least one surface of the current collector substrate.

[0094] In detail, the oscillation treatment involves adjusting the amplitude and wavelength of the squeegee. The amplitude represents the range of the squeegee's up-and-down movement, and the wavelength represents the speed of the squeegee's horizontal movement. Through the oscillation treatment, the first slurry can be coated with a textured structure on the conductive layer due to the vibration of the squeegee.

[0095] This application does not limit the composition of the conductive agent slurry. In one specific embodiment, the conductive agent slurry includes a conductive agent, a binder, and water. The specific selection of the conductive agent and binder can be the same as materials commonly used in the art.

[0096] This application also provides an electrode, including the aforementioned current collector or the current collector obtained by the aforementioned preparation method and an active layer; the active layer is disposed on the first surface of the conductive layer 2, and the surface of the active layer facing the first surface 2a has a mating structure adapted to the concave-convex structure.

[0097] like Figure 18 As shown, the current collector substrate 1 and the conductive layer 2 with an uneven structure constitute the current collector, and the active layer 5 has a mating structure adapted to the uneven structure. The mating structure in this application refers to a structure that can engage and match the uneven structure of the current collector; that is, corresponding to the protruding structure 3 of the current collector, the active layer 5 has a recessed structure at the corresponding position that completely engages and matches the protruding structure 3, and corresponding to the recessed structure 4 of the current collector, the active layer 5 has a protruding structure at the corresponding position that completely engages and matches the recessed structure 4. This electrode has advantages corresponding to the aforementioned current collector, which will not be elaborated here.

[0098] The electrode in this application can be a positive electrode or a negative electrode, specifically including the aforementioned current collector and an active layer 5 formed of active material disposed on the surface of the current collector.

[0099] In the specific preparation of the positive electrode sheet, for example, the positive electrode active material, conductive agent, and binder can be dispersed in an appropriate amount of N-methylpyrrolidone (NMP) solvent and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, rolling, and slitting, the positive electrode sheet is obtained. In one specific embodiment, the positive electrode active layer comprises, by mass percentage, 70-99 wt% positive electrode active material, 0.5-15 wt% conductive agent, and 0.5-15 wt% binder; more specifically, it comprises 80-98 wt% positive electrode active material, 1-10 wt% conductive agent, and 1-10 wt% binder.

[0100] This application does not strictly limit the positive electrode active material in the positive electrode sheet, and can be any positive electrode active material commonly used in lithium-ion batteries, such as at least one composite oxide of lithium with cobalt, manganese, nickel, or combinations thereof. More specifically, it can be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0101] The conductive agent may be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber; the binder may be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, and polyurethane.

[0102] In the specific preparation of the negative electrode sheet, the negative electrode active material, conductive agent, and binder can be dispersed in an appropriate amount of deionized water and thoroughly stirred to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector, and after drying, rolling, and slitting, the negative electrode sheet is obtained. In one specific embodiment, the negative electrode active layer comprises, by mass percentage, 70-99 wt% of negative electrode active material, 0.5-15 wt% of conductive agent, and 0.5-15 wt% of binder; more specifically, it comprises 80-98 wt% of negative electrode active material, 1-10 wt% of conductive agent, and 1-10 wt% of binder.

[0103] This application does not strictly limit the negative electrode active material in the negative electrode sheet. It can be at least one of the negative electrode active materials commonly used in lithium-ion batteries, such as graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon suboxide and silicon-carbon negative electrode), and tin-based negative electrode materials (mainly including tin and tin alloy).

[0104] The conductive agent may be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and graphene; the binder may be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0105] This application also provides a battery including the aforementioned electrode. The battery provided by this application has advantages corresponding to the aforementioned current collector, which will not be elaborated here.

[0106] It is conceivable that, in addition to the aforementioned electrodes, the battery of this application also includes an electrolyte and a separator. The battery of this application may have the aforementioned electrodes as the positive electrode, or the aforementioned electrodes as the negative electrode, or both the positive and negative electrodes may be the aforementioned electrodes.

[0107] This application does not strictly limit the choice of electrolyte, which may include one or more solvents commonly used in lithium-ion battery electrolytes, as well as lithium salts commonly used in lithium-ion electrolytes. For example, the solvent may be ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, methyl ethyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the lithium salt may be one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0108] This application does not strictly limit the choice of separator material. It can be one of the separator materials commonly used in lithium-ion batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, and separator with ceramic coating.

[0109] In the preparation of lithium-ion batteries, the positive electrode, separator, and negative electrode are wound or stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After the packaged battery is dried at 85°C, the electrolyte is injected into the dried battery. The battery undergoes resting, formation, and secondary sealing to complete the preparation of the lithium-ion battery.

[0110] This application also provides a battery pack comprising at least two of the aforementioned batteries, which has advantages corresponding to the aforementioned current collectors, and will not be elaborated here.

[0111] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0112] This application also provides an electrical device including the aforementioned battery or the aforementioned battery pack, which has advantages corresponding to the aforementioned current collector, and will not be elaborated here.

[0113] The electrical equipment used in this application can be conventional electrical equipment in the field, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without any particular limitation.

[0114] The current collector provided in this application will be described in detail below through specific embodiments.

[0115] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0116] Example 1

[0117] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20As shown, the extension direction of the concave structure 4 and the convex structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The method for preparing the electrode containing the current collector includes the following steps:

[0118] 1) Mix PVP, CMC, PAA and water and stir for 2 hours. Add carbon black and stir again for 30 minutes to obtain the first slurry. The mass ratio of PVP, CMC, PAA, water and carbon black is 1:1:24:20:12. Coat the first slurry on both sides of aluminum foil using a doctor blade with an arc-shaped outer contour. The coating thickness is 3μm. After drying, a current collector is obtained. The distance between the highest point of two adjacent protrusions in the conductive layer of the current collector is 3μm, the distance between the lowest point of two adjacent depressions is 3μm, the height of the protrusion in the protrusion is 2μm, and the depth of the depression in the depression is 2μm.

[0119] 2) Stir NMP and PVDF for 2 hours, then add carbon black and continue stirring for 30 minutes. Then add LiFePO4 and continue stirring for 2 hours to obtain the second slurry. The mass ratio of NMP, PVDF, carbon black and LiFePO4 is 100:3:1:100. Coat the slurry on the conductive layer and dry it to obtain the electrode sheet.

[0120] Example 2

[0121] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the concave structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that the coating thickness in step 1) is 2μm.

[0122] Example 3

[0123] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the concave structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that the coating thickness in step 1) is 4μm.

[0124] Example 4

[0125] In this embodiment, the current collector is as follows: Figure 19As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the distance between the highest point of two adjacent protruding structures of the conductive layer of the current collector is 1 μm, and the distance between the lowest point of two adjacent recessed structures is 1 μm.

[0126] Example 5

[0127] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the distance between the highest point of two adjacent protruding structures of the conductive layer of the current collector is 5 μm, and the distance between the lowest point of two adjacent recessed structures is 5 μm.

[0128] Example 6

[0129] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the height of the protrusion in the conductive layer protrusion structure of the current collector is 1 μm, and the depth of the recess in the recessed structure is 1 μm.

[0130] Example 7

[0131] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the height of the protrusion in the conductive layer protrusion structure of the current collector is 3μm, and the depth of the recess in the recessed structure is 3μm.

[0132] Example 8

[0133] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that the coating thickness in step 1) is 1.5 μm, the height of the protrusion in the conductive layer of the current collector is 1 μm, and the depth of the recess in the recessed structure is 1 μm.

[0134] Example 9

[0135] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the concave structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that the coating thickness in step 1) is 4.5 μm.

[0136] Example 10

[0137] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the distance between the highest point of two adjacent protruding structures of the conductive layer of the current collector is 0.5 μm, and the distance between the lowest point of two adjacent recessed structures is 0.5 μm.

[0138] Example 11

[0139] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the distance between the highest point of two adjacent protruding structures of the conductive layer of the current collector is 5.5 μm, and the distance between the lowest point of two adjacent recessed structures is 5.5 μm.

[0140] Example 12

[0141] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), the height of the protrusion in the conductive layer protrusion structure of the current collector is 0.5 μm, and the depth of the recess in the recessed structure is 0.5 μm.

[0142] Example 13

[0143] In this embodiment, the current collector is as follows: Figure 19 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the recessed structure 4 and the protruding structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that the coating thickness in step 1) is 4 μm, the height of the protrusion in the conductive layer of the current collector is 3.5 μm, and the depth of the recess in the recessed structure is 3.5 μm.

[0144] Example 14

[0145] In this embodiment, the current collector is as follows: Figure 21 As shown, the first surface 2a of the conductive layer 2 has multiple recessed structures 4 and multiple protruding structures 3, which are alternately arranged, such as... Figure 20 As shown, the extension direction of the concave structure 4 and the convex structure 3 is the width direction of the current collector substrate 1, and the array arrangement direction is the length direction of the current collector substrate 1. The angle β1 between the extension direction of the convex sidewall of the convex structure 3 and the length direction of the current collector substrate 1 is 75°, and the angle β2 between the extension direction of the concave sidewall of the concave structure 4 and the length direction of the current collector substrate 1 is 75°. The preparation method of the electrode containing the current collector is basically the same as that in Example 1, except that in step 1), a scraper with a planar outer contour is used instead of a scraper with an arc-shaped outer contour.

[0146] Comparative Example 1

[0147] In this embodiment, the conductive layer of the current collector is planar, and the preparation method of the electrode containing the current collector is basically the same as that in Embodiment 1, except that the surface of the conductive layer does not have an uneven structure.

[0148] Experimental Example 1

[0149] The following parameters were measured for all embodiments and comparative examples: the distance (L1) between the highest points of two adjacent protruding structures, the distance (L2) between the lowest points of two adjacent recessed structures, the height (H1) of the protrusion in the protruding structure, the depth (H2) of the recess in the recessed structure, the shape of the outer wall surface (3x) of the protrusion in the protruding structure, the shape of the inner wall surface (4x) of the recess in the recessed structure, the angle (β1) between the extension direction of the side wall surface of the protrusion in the planar protruding structure and the length direction of the current collector substrate, the angle (β2) between the extension direction of the side wall surface of the recess in the planar recessed structure and the length direction of the current collector substrate, and the thickness (H3) of the conductive layer. The measurement results are shown in Table 1.

[0150] The distance (L1) between the highest points of two adjacent protrusions: measured by SEM;

[0151] The distance (L2) between the lowest points of two adjacent depressions: measured by SEM;

[0152] Height of the protrusion (H1) in the protruding structure: measured by SEM;

[0153] Depth (H2) of the depression in the depression structure: measured by SEM;

[0154] Shape of the outer wall (3x) of the protrusion in the protruding structure: measured by SEM;

[0155] Shape of the inner wall (4x) of the recess in the concave structure: measured by SEM;

[0156] The angle (β1) between the extension direction of the sidewall of the protrusion in the planar protrusion structure and the length direction of the current collector matrix: measured by SEM;

[0157] The angle (β2) between the extension direction of the recessed sidewall and the length direction of the current collector matrix in the planar recessed structure: measured by SEM.

[0158] Table 1

[0159]

[0160] Experimental Example 2

[0161] In all the examples and comparative examples, the current collectors are used to prepare positive electrode sheets with the positive electrode active layer. Then, the positive electrode sheets are combined with a negative electrode sheet, an electrolyte, and a separator to form a battery, including the following steps:

[0162] 1) Mix lithium iron phosphate, carbon black, and PVDF in a mass ratio of 100:1:3, add NMP, stir evenly, and prepare a positive electrode slurry; coat the positive electrode slurry on both sides of the current collector, and after drying and rolling, form a positive electrode coating on both sides of the aluminum foil to obtain a positive electrode sheet.

[0163] 2) Mix graphite, carbon black, SBR and CMC in a mass ratio of 100:1:2:2, add deionized water to prepare a negative electrode slurry, and coat it on both sides of the copper foil to obtain a negative electrode sheet.

[0164] 3) Mix EC, EMC, DMC and LiPF6 and stir at 25℃ for 2 hours to obtain electrolyte; wherein the mass ratio of EC, EMC and DMC is 1:1:1.5 and the mass percentage of LiPF6 in the electrolyte is 15%.

[0165] 4) The above-mentioned positive electrode, negative electrode, electrolyte, and polyethylene / polypropylene composite membrane are used as separators to assemble CR2016 button cells.

[0166] The peel strength, mixed specific capacity, cycle performance, and DCIR of the above-mentioned positive electrode sheets were measured, and the results are shown in Table 2.

[0167] Peel strength: Apply adhesive tape to the surface of the positive electrode, ensuring there are no air bubbles between the tape and the electrode, and that the electrode is flat; cut the sample with the tape applied to a size of 4×10 cm. 2 Peel off the current collector and apply tape. Roll the cut sample twice using a roller glue machine. Attach the sample to the test fixture with double-sided tape and perform a 180° peel test using a tensile testing machine.

[0168] Cycling performance: The battery was charged to 3.8V at 0.5C constant current at 45℃ and left to rest for 10 minutes to obtain capacity C1; then discharged to 2.0V at 0.5C constant current and left to rest for 10 minutes, and cycled 1000 times to obtain capacity C1000; the battery's cycle performance was characterized by capacity retention rate = (C1000 / C1) × 100%.

[0169] Mixed material specific capacity: The mass of the mixed material is obtained by subtracting the mass of the current collector from the mass of the positive electrode sheet. Mixed material specific capacity = battery capacity C1 / mixed material mass.

[0170] Impedance (DCIR): After the battery is discharged to 2.0V at 1 / 3C, it is charged to 50%SOC at 1 / 3C and then left to stand at 25℃ for 2 hours. The voltage value V1 is recorded. The battery is discharged at 1.5C for 30s and the voltage value V2 is recorded. After standing for 1 hour, it is charged at 0.1C for 450s and then left to stand for 1 hour. DCIR = (V1-V2) / 1.5C.

[0171] Table 2

[0172]

[0173] Combining Table 1 and Table 2, we can see that:

[0174] 1) The current collector in this application can effectively improve the peel strength of the electrode;

[0175] 2) The current collector of this application can reduce the resistance of the battery and improve the cycle performance of the battery.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A current collector, characterized in that, It includes a current collector substrate and a conductive layer, wherein the conductive layer is disposed on at least one surface of the current collector substrate along the thickness direction, and the first surface of the conductive layer away from the current collector substrate has an uneven structure.

2. The current collector according to claim 1, characterized in that, The first surface is provided with a raised structure, which protrudes from the first surface in the thickness direction; and / or, The first surface is provided with a recessed structure, and in the thickness direction, the lowest point of the recessed structure is lower than the first surface.

3. The current collector according to claim 1 or 2, characterized in that, The first surface is provided with N protrusions, and the N protrusions are arranged in an array along the extension direction of the first surface, where N ≥ 2; and / or, The first surface is provided with M recessed structures, and the M recessed structures are arranged in an array along the extension direction of the first surface, where M ≥ 2.

4. The current collector according to claim 3, characterized in that, The protruding structure is a strip-shaped structure, and N protruding structures extend along a first direction and are arranged in an array along a second direction. The first and second directions intersect each other and are both parallel to the first surface; and / or, The recessed structure is a strip-shaped structure. M of the recessed structures extend along a first direction and are arranged in an array along a second direction. The first direction and the second direction intersect each other and are both parallel to the first surface.

5. The current collector according to any one of claims 2-4, characterized in that, The recessed structure and the raised structure are alternately arranged.

6. The current collector according to any one of claims 2-5, characterized in that, In a direction parallel to the first surface, the distance between the highest points of two adjacent protrusions is 1-5 µm; and / or, In a direction parallel to the first surface, the distance between the lowest points of two adjacent recessed structures is 1-5µm.

7. The current collector according to any one of claims 2-6, characterized in that, The height of the protrusion in the protrusion structure is 1-3µm; and / or, The depth of the depression in the depression structure is 1-3µm.

8. The current collector according to any one of claims 2-7, characterized in that, The outer wall surface of the protrusion in the protrusion structure is an arc surface; and / or... The inner wall surface of the recessed structure is an arc surface.

9. The current collector according to any one of claims 2-8, characterized in that, The outer wall of the protrusion in the protrusion structure is a plane, and the angle between the extending direction of the side wall of the protrusion and the length direction of the current collector substrate is 2-85°; and / or, The inner wall of the recessed structure is a plane, and the angle between the extension direction of the side wall of the recess and the length direction of the current collector matrix is ​​2-85°.

10. The current collector according to any one of claims 1-9, characterized in that, The thickness of the conductive layer is 1-30 μm; and / or, The conductive layer includes a conductive agent and a binder, wherein the conductive agent accounts for 20-99% of the mass of the conductive layer.

11. A method for preparing a current collector according to any one of claims 1-10, characterized in that, Includes the following steps: The current collector is obtained by scraping and vibrating a conductive agent slurry located on at least one surface of the current collector substrate.

12. An electrode sheet, characterized in that, The current collector includes the current collector according to any one of claims 1-10 or the current collector obtained by the preparation method according to claim 11 and an active layer; the active layer is disposed on the first surface of the conductive layer, and the surface of the active layer facing the first surface has a mating structure adapted to the uneven structure.

13. A battery, characterized in that, Includes the electrode sheet as described in claim 12.

14. A battery pack, characterized in that, It includes at least two batteries as described in claim 13.

15. An electrical appliance, characterized in that, This includes the battery as described in claim 13, or the battery pack as described in claim 14.

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