Negative electrode sheet, preparation method therefor, battery and electrical device

Abstract

A negative electrode sheet, the negative electrode sheet comprising a negative current collector and lithium metal layers. The negative current collector has a first surface and an opposite second surface, the first surface and the second surface of the negative current collector being loaded with the lithium metal layers. In the technical solution, loading the surfaces of the negative current collector with lithium metal to serve as the negative electrode sheet can greatly ameliorate the problem that, when independently serving as a negative electrode sheet, the lithium metal is prone to pulverization and collapse in cyclic processes, improving the cycle performance of batteries.

Description

Negative electrode sheet and preparation method thereof, battery, and electrical equipment

[0001] Cross-references

[0002] This application claims priority to the Chinese invention patent application with application number 202410282219.9 filed on March 12, 2024, entitled “Negative electrode sheet and preparation method thereof, battery, and electrical equipment,” the contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to a negative electrode plate and a preparation method thereof, a battery, and an electrical device. Background Art

[0004] In recent years, with the development of lithium-ion secondary battery technology, lithium-ion secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion secondary batteries have achieved great development, higher requirements have been placed on their cycle performance.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a negative electrode plate and a preparation method thereof, a battery, and an electrical device.

[0007] The embodiment of the present application is implemented as follows:

[0008] In a first aspect, an embodiment of the present application provides a negative electrode plate, the negative electrode plate comprising:

[0009] a negative electrode current collector having a first surface and an opposing second surface; and

[0010] Lithium metal layer; the lithium metal layer is supported on the first surface and the second surface of the negative electrode current collector.

[0011] In the above technical solution, lithium metal is loaded on the surface of the negative electrode current collector as the negative electrode plate. The negative electrode current collector plays a structural supporting role for the lithium metal layer, which is beneficial to the cycle performance of the battery.

[0012] In some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sa is 0.5-50.

[0013] The above technical solution, by setting the roughness of the lithium metal layer surface to include: Sa is 0.5μm to 50μm; it is conducive to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0014] In some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sz is 10-90.

[0015] The above technical solution, by setting the roughness of the lithium metal layer surface to include: Sz is 10μm to 90μm; it is further beneficial to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0016] In some optional embodiments, the thickness of the lithium metal layer is 5 μm to 50 μm.

[0017] In the above technical solution, setting the thickness of the lithium metal layer to 5 μm to 50 μm is beneficial to improving the cycle performance of the battery.

[0018] In some optional embodiments, the thickness of the negative electrode current collector is 5 μm to 15 μm.

[0019] In the above technical solution, setting the thickness of the negative electrode current collector to 5 μm to 15 μm is beneficial to improving the cycle performance of the battery.

[0020] In some optional embodiments, the roughness of the negative electrode current collector includes: Ra is 0.2 μm to 3 μm.

[0021] In the above technical solution, by setting the roughness of the negative electrode current collector to include: Ra is 0.2μm to 3μm; it is beneficial for the lithium metal layer to be loaded on the negative electrode current collector, improving the bonding force and bonding uniformity; thereby improving the cycle performance of the battery.

[0022] In some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sa is 25 μm to 28 μm.

[0023] In the above technical solution, by setting the roughness of the surface of the lithium metal layer to include: Sa is 25μm to 28μm, it is further beneficial to improve the cycle performance of the battery.

[0024] In some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sz is 60 μm to 70 μm.

[0025] In the above technical solution, by setting the roughness of the surface of the lithium metal layer to include: Sz is 60μm to 70μm, it is further beneficial to improve the cycle performance of the battery.

[0026] In some optional embodiments, the negative electrode sheet further includes: a transition layer;

[0027] The transition layer is located between the negative electrode current collector and the lithium metal layer;

[0028] The transition layer includes at least one of a transition metal, a carbide or a nitride.

[0029] In the above technical solution, by providing a transition layer between the negative electrode current collector and the lithium metal layer, the strength of the bond with the lithium metal can be enhanced and the uniformity of the bond strength distribution can be improved. This can help improve the stability of the negative electrode structure and, in turn, the battery's cycling performance. Furthermore, in the above technical solution, at least one of a transition metal, carbide, or nitride is selected as the transition layer. The composition and morphology of these transition layers can help improve the strength of the bond with the lithium metal and the uniformity of the bond strength distribution. This can help improve the stability of the negative electrode structure and, in turn, the battery's cycling performance.

[0030] In some optional embodiments, the thickness of the transition layer is 500 nm to 2 μm.

[0031] In the above technical solution, by setting the thickness of the transition layer to 500 nm to 2 μm, it is beneficial to improve the structural stability of the negative electrode during the battery cycle, thereby improving the cycle performance of the battery.

[0032] In some optional embodiments, the transition metal comprises at least one of magnesium, bismuth, tin, zinc, cobalt, aluminum, palladium, silver, or gold; and / or

[0033] The carbide comprises at least one of carbon nanotubes, graphene, Ketjen black or carbon black; and / or

[0034] The nitride includes at least one of carbon trinitride tetranitride, aluminum nitride or boron nitride.

[0035] In a second aspect, an embodiment of the present application provides a method for preparing a negative electrode sheet, comprising: rolling lithium metal onto a first surface and a second surface of a negative electrode current collector to form a lithium metal layer.

[0036] The above technical solution, which rolls lithium metal onto the first and second surfaces of the negative electrode current collector, can greatly improve the problem of lithium dendrites easily occurring during the cycle when lithium metal is used as the negative electrode plate, thereby improving the cycle performance of the battery.

[0037] In some optional embodiments, a second rolling is performed on the surface of the formed lithium metal layer.

[0038] In the above technical solution, the consistency of the surface state of the lithium metal layer can be improved by performing a second rolling on the surface of the formed lithium metal layer. It is also beneficial to reduce the roughness of the lithium metal surface by rolling it to a suitable range. The surface state of lithium metal, that is, the size of the roughness, affects the nucleation and growth of lithium ions. Too large a roughness will lead to dendrite growth; on the contrary, a smooth surface will make initial nucleation difficult and polarization severe. The above technical solution is beneficial to reduce the roughness of the surface of the lithium metal layer by rolling it to Sa of 0.5μm to 50μm and / or Sz of 10μm to 90μm; within this roughness range, the roughness is appropriate, which is conducive to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0039] In some optional embodiments, rolling the lithium metal onto the first surface and the second surface of the negative electrode current collector comprises:

[0040] Lithium metal is rolled onto the first surface and the second surface of the negative electrode current collector at 200° C. to 220° C.

[0041] In the above technical solution, lithium metal is rolled onto the first and second surfaces of the negative electrode current collector at 200°C to 220°C; compared with rolling at room temperature, hot pressing is less likely to produce large differences in indentations on the lithium metal surface; within the above temperature range, lithium is in a flowing state and can be tightly combined with the negative electrode current collector, which can further reduce the indentation difference on the lithium metal surface, which is beneficial to improving the consistency of the surface state of the lithium metal layer; and thus is beneficial to the cycle performance of the battery.

[0042] In some optional embodiments, a second rolling is performed on the surface of the formed lithium metal layer, comprising:

[0043] The surface of the formed lithium metal layer is rolled for the second time using a roller having protrusions on its circumferential surface.

[0044] In the above technical solution, by using a roller with protrusions on the circumference to perform a second rolling on the surface of the formed lithium metal layer, the surface roughness of the lithium metal can be improved, which is beneficial to the cycle performance of the battery.

[0045] In some optional embodiments, the protrusion satisfies at least one of the following characteristics:

[0046] (1) The cross-sectional shape of the protrusion is circular;

[0047] (2) The height of the protrusion is 0.5 mm to 1.5 mm;

[0048] (3) The diameter of the protrusion is 1 mm to 2 mm.

[0049] In some optional embodiments, the first surface and the second surface of the negative electrode current collector include a transition layer;

[0050] Rolling lithium metal onto the first surface and the second surface of the negative electrode current collector to form a lithium metal layer includes: rolling lithium metal onto a transition layer to form a lithium metal layer.

[0051] In the above technical solution, a transition layer is deposited on the surface of the negative electrode current collector. After the transition layer is deposited, the morphology of the negative electrode current collector further changes with the deposited material. The coating with higher roughness can improve the adhesion with lithium metal; and is conducive to the uniformity of the distribution of the strength of the adhesion; thereby, it is beneficial to improve the stability of the negative electrode structure, and thus is beneficial to the cycle performance of the battery.

[0052] In some optional embodiments, before forming the transition layer, the method further includes:

[0053] The negative electrode current collector is roughened, and then the transition layer is deposited.

[0054] The above technical solution roughens the negative electrode current collector to achieve a roughness of Ra of 0.2μm to 3μm and / or Rz of 2.5μm to 6μm. The clean and further roughened surface of the negative electrode current collector facilitates enhanced adhesion to the transition layer. After deposition of the transition layer, the negative electrode current collector morphology further changes with the deposited material. The rougher coating enhances adhesion to lithium metal, thereby improving battery cycling performance.

[0055] In some optional embodiments, roughening comprises:

[0056] The negative electrode current collector is roughened by plasma etching, laser cleaning or hydrochloric acid immersion.

[0057] In the above technical solution, the negative electrode current collector is roughened by plasma etching, laser cleaning or hydrochloric acid immersion; the surface of the negative electrode current collector can be cleaned and roughened to obtain a roughened surface morphology, which is beneficial to improving the adhesion between the transition layer and the negative electrode current collector; after the transition layer is deposited, the morphology of the negative electrode current collector further changes with the deposited material, and the coating with higher roughness can improve the adhesion with lithium metal, which is beneficial to improving the battery cycle performance.

[0058] In some optional embodiments, forming a transition layer includes:

[0059] The transition metal, carbide or nitride is deposited as the transition layer by means of electrodeposition, magnetron sputtering or doctor blade coating.

[0060] In a third aspect, an embodiment of the present application provides a battery, which includes the negative electrode plate provided in the first aspect or the second aspect.

[0061] In the above technical solution, the battery is provided with the negative electrode plate provided by the first aspect or the second aspect, which is beneficial to improving the cycle performance of the battery.

[0062] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes the battery provided in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0064] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0065] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0066] FIG3 is an exploded view of the battery cell shown in FIG2 ;

[0067] FIG4 is a schematic diagram of a partial structure of an electrode assembly provided in some embodiments of the present application;

[0068] FIG5 is a schematic diagram of a partial structure of a positive electrode sheet provided in some embodiments of the present application;

[0069] FIG6 is a graph showing the relationship between the surface roughness of lithium metal and the nucleation potential;

[0070] Figure 7 a shows the surface of the original rolled lithium copper foil of Example 1-1; Figure b shows the surface of the lithium copper foil after the second rolling;

[0071] Figure 8 (a) is a micrograph of the original copper foil of Example 2-1; Figure (b) is a micrograph of the surface of the roughened copper foil;

[0072] Figure 9 a is the SEM image of the original copper foil of Example 2-1 (the small picture in the upper right corner of Figure a is a photo); Figure b is the SEM image of the copper foil surface after depositing the transition layer (the small picture in the upper right corner of Figure b is a photo).

[0073] Icons: Vehicle 1000; Battery 100; Controller 200; Motor 300; Housing 10; First portion 11; Second portion 12; Accommodation space 13; Battery cell 20; Housing 21; Electrode assembly 22; Electrode terminal 23; Pressure relief structure 24; Case 211; Cover 212; Positive electrode sheet 221; Negative electrode sheet 222; Separator 223; Positive current collector 2211; Positive active material layer 2212; Negative current collector 2221; Lithium metal layer 2222. DETAILED DESCRIPTION

[0074] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0076] 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 number, specific order or primary and secondary relationship of the indicated technical features.

[0077] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0078] In the description of the embodiments of this application, unless otherwise specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on specific circumstances.

[0079] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0080] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the heights, lengths, widths, and other dimensions of the various components in the embodiments of this application, as well as the overall heights, lengths, widths, and other dimensions of the integrated device shown in the drawings are merely illustrative and do not constitute any limitation on this application.

[0081] Compared with graphite materials, lithium metal as the negative electrode of lithium-ion batteries can improve the energy density of lithium-ion batteries; however, lithium metal as the negative electrode is prone to problems such as lithium metal pulverization and collapse during the cycle process.

[0082] The present invention provides a negative electrode plate, which includes:

[0083] a negative electrode current collector having a first surface and an opposing second surface; and

[0084] Lithium metal layer; the lithium metal layer is supported on the first surface and the second surface of the negative electrode current collector.

[0085] In the above technical solution, lithium metal is loaded on the surface of the negative electrode current collector as the negative electrode plate. The negative electrode current collector plays a structural supporting role for the lithium metal layer, which is beneficial to the cycle performance of the battery.

[0086] The present application provides a battery, comprising the aforementioned negative electrode plate.

[0087] The battery is provided with the negative electrode plate provided in the aforementioned embodiment, which is beneficial to improving the cycle performance of the battery.

[0088] The present application provides an electrical device including the aforementioned battery.

[0089] The electrical equipment has improved comprehensive performance by being provided with the battery provided in the aforementioned embodiment.

[0090] Refer to Figure 1, which is a structural schematic diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0091] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0092] In this application, battery 100 refers to a single physical module that includes one or more battery cells 20 to provide voltage and capacity. Battery 100 generally includes a housing 10 for enclosing one or more battery cells 20. Housing 10 prevents liquids or other foreign matter from affecting the charging or discharging of battery cells 20.

[0093] Referring to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application, the battery 100 may include a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to house the battery cell 20 and may have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other and together define a storage space 13 for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one end open, and the first portion 11 may be a plate-like structure, which overlaps the open side of the second portion 12 to form the housing 10 with the storage space 13. Alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12 to form the housing 10 with the storage space 13. Of course, the first portion 11 and the second portion 12 may have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0094] In the battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection. Mixed connection means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the case 10. Alternatively, multiple battery cells 20 can be first connected in series, in parallel, or in a mixed connection to form a module, and the multiple modules are then connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the case 10. The battery 100 can also include other structures. For example, the multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of the multiple battery cells 20.

[0095] Referring to Figure 3 , which is an exploded view of the battery cell 20 shown in Figure 2 , the battery cell 20 is the smallest unit that makes up the battery 100. The battery cell 20 may include a housing 21 , an electrode assembly 22 , and an electrolyte, with both the electrode assembly 22 and the electrolyte being housed within the housing 21 .

[0096] The outer shell 21 may include a shell 211 and a cover 212. The shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space of the battery cell 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, electrolyte and other components. The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211. Functional components such as electrode terminals 23 and pressure relief structures 24 can also be provided on the cover 212. A sealing ring can be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.

[0097] The shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell 211 and the cover 212 can be various, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance. A coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0098] Referring to Figure 4 , the electrode assembly 22 may be composed of a positive electrode sheet 221, a negative electrode sheet 222, and a separator 223. The separator 223 is located between the positive electrode sheet 221 and the negative electrode sheet 222 to provide isolation. The electrode assembly 22 may be a wound or laminated structure, but the present invention is not limited thereto.

[0099] Continuing with FIG5 , the positive electrode sheet 221 includes a positive electrode current collector 2211 and a positive electrode active material layer 2212 . Taking a lithium-ion battery cell as an example, the material of the positive electrode current collector 2211 may be aluminum. The positive electrode active material layer 2212 includes a positive electrode active material. Furthermore, in some embodiments of the present application, the positive electrode active material includes a positive electrode material capable of absorbing and releasing lithium; illustratively, the positive electrode active material includes lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate, and a lithium-rich manganese-based material.

[0100] Please refer to FIG5 . Further, in some embodiments of the present application, the negative electrode sheet 222 includes a negative electrode current collector 2221 having a first surface and an opposite second surface; and

[0101] Lithium metal layer 2222 ; the lithium metal layer 2222 is supported on the first surface and the second surface of the negative electrode current collector 2221 .

[0102] In the above technical solution, lithium metal is loaded on the surface of the negative electrode current collector as the negative electrode plate. The negative electrode current collector plays a structural supporting role for the lithium metal layer, which is beneficial to the cycle performance of the battery.

[0103] Furthermore, in some embodiments of the present application, the roughness of the surface of the lithium metal layer includes: Sa is 0.5 μm to 50 μm.

[0104] The roughness of the lithium metal surface affects the nucleation and growth of lithium ions. Excessive roughness leads to dendrite growth, while too little roughness makes it difficult for lithium ions to nucleate on the lithium metal surface, resulting in excessive impedance and large polarization during battery cycling. The diffusion barrier of lithium ions on the lithium metal surface is large, so the thermodynamically low growth direction of lithium ions on the lithium metal surface is longitudinal growth. The lithium metal with a smooth surface has a large impedance, which causes a sharp increase in the battery overpotential in the early stages of nucleation. On the contrary, a lithium metal surface with large roughness is conducive to protrusion nucleation; however, it further increases the resistance to lateral diffusion and worsens diameter growth. Appropriate roughness achieves a balance between nucleation and diffusion. As shown in Figure 6, the roughness of the lithium metal surface is strongly correlated with the nucleation overpotential. Appropriate roughness is conducive to nucleation, and the subsequent charging overpotential is also relatively small. Appropriate nucleation overpotential is also beneficial to cycle performance.

[0105] The above technical solution, by setting the roughness of the lithium metal layer surface to include: Sa is 0.5μm to 50μm; it is conducive to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0106] Furthermore, in the above technical solution, the Sa value is a physical quantity that describes surface roughness. It represents the average deviation of surface height. It can be used to measure the degree of surface irregularity; that is, the surface's undulations and concavities. The smaller the Sa value, the smoother the surface.

[0107] The roughness parameter Sa (arithmetic mean height roughness) can be calculated according to ISO 25178 standard.

[0108] For example, in some embodiments of the present application, the roughness parameter (Sa) can be tested according to the following method:

[0109] A surface profile measuring instrument, such as a laser interferometer or white light interferometer, is used to scan and measure the surface of an object. The surface profile data obtained from the scan is used to generate a surface profile deviation curve. Based on the deviation curve, the absolute value of the average deviation of the surface profile, or Sa, is calculated.

[0110] Further optionally, exemplarily, in some embodiments of the present application, the above-mentioned Sa is 0.5μm, 1μm, 2μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm or a range between any two of the above-mentioned values.

[0111] Further optionally, in some embodiments of the present application, the above-mentioned Sa is 0.5μm~5μm, 5μm~10μm, 10μm~15μm, 15μm~20μm, 20μm~25μm, 25μm~30μm, 30μm~35μm, 35μm~40μm, 40μm~45μm or 45μm~50μm.

[0112] Furthermore, in some embodiments of the present application, the roughness of the surface of the lithium metal layer includes: Sz is 10 μm to 90 μm.

[0113] The above technical solution, by setting the roughness of the lithium metal layer surface to include: Sz is 10μm to 90μm; it is further beneficial to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0114] In the above technical solution, the roughness parameter Sz is a physical quantity that describes surface roughness. It represents the sum of the maximum peak height and the maximum valley depth in a region, i.e., the maximum height; it can quantify the degree of surface roughness.

[0115] The above-mentioned roughness parameter Sz (maximum height roughness) can be calculated according to the ISO 2517 standard.

[0116] For example, in some embodiments of the present application, the roughness parameter (Sz) can be measured by scanning the surface of an object using a surface profile measuring instrument, such as a laser interferometer or a white light interferometer. The surface profile data obtained by scanning can be read to obtain the value of each measurement point. Then, the roughness parameter (Sz) formula is used to calculate Sz:

[0117] Sz=Sp+Sv

[0118] Where Sp is the maximum peak height roughness value; Sv is the maximum valley depth roughness value; Sp and Sv are read from the surface profile data.

[0119] Further optionally, exemplarily, in some embodiments of the present application, the above-mentioned Sz is 10μm, 12μm, 15μm, 18μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 85μm, 88μm, 90μm or a range between any two of the foregoing values.

[0120] Further optionally, in some embodiments of the present application, the above-mentioned Sz is 10μm~20μm, 20μm~30μm, 30μm~40μm, 40μm~50μm, 50μm~60μm, 60μm~70μm, 70μm~80μm, 80μm~90μm.

[0121] Furthermore, in some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sa is 25 μm to 28 μm.

[0122] In the above technical solution, by setting the roughness of the surface of the lithium metal layer to include: Sa is 25μm to 28μm, it is further beneficial to improve the cycle performance of the battery.

[0123] Illustratively, the roughness of the surface of the lithium metal layer includes: Sa is 25 μm, 26 μm, 27 μm, 28 μm, or a range between any two of the foregoing values.

[0124] In some optional embodiments, the roughness of the surface of the lithium metal layer includes: Sz is 60 μm to 70 μm.

[0125] In the above technical solution, by setting the roughness of the surface of the lithium metal layer to include: Sz is 60μm to 70μm, it is further beneficial to improve the cycle performance of the battery.

[0126] Illustratively, the roughness of the surface of the lithium metal layer includes: Sz is 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range between any two of the foregoing values.

[0127] Furthermore, in some embodiments of the present application, the thickness of the lithium metal layer is 5 μm to 50 μm.

[0128] Illustratively, in some embodiments of the present application, the thickness of the lithium metal layer is 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 48 μm, 50 μm or a range between any two of the foregoing values.

[0129] In the above technical solution, setting the thickness of the lithium metal layer to 5 μm to 50 μm is beneficial to improving the cycle performance of the battery.

[0130] Further optionally, in some embodiments of the present application, the thickness of the above-mentioned lithium metal layer is 5μm~10μm, 10μm~15μm, 15μm~20μm, 20μm~25μm, 25μm~30μm, 30μm~35μm, 35μm~40μm, 40μm~45μm or 45μm~50μm.

[0131] Furthermore, in some embodiments of the present application, the thickness of the negative electrode current collector is 5 μm to 15 μm.

[0132] Illustratively, in some embodiments of the present application, the thickness of the negative electrode current collector is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range between any two of the foregoing values.

[0133] In the above technical solution, setting the thickness of the negative electrode current collector to 5 μm to 15 μm is beneficial to improving the cycle performance of the battery.

[0134] Furthermore, in some embodiments of the present application, the negative electrode current collector may be made of copper foil, copper alloy, etc.

[0135] Furthermore, in some embodiments of the present application, the negative electrode plate further includes: a transition layer;

[0136] The transition layer is located between the negative electrode current collector and the lithium metal layer;

[0137] The transition layer includes at least one of a transition metal, a carbide or a nitride.

[0138] Poor adhesion between lithium metal and the negative electrode current collector (e.g., copper foil) can cause active material shedding and power outages, impacting the stability of the negative electrode structure. In the above technical solution, by providing a transition layer between the negative electrode current collector and the lithium metal layer, the strength of the adhesion to the lithium metal can be enhanced and the distribution of the adhesion strength can be evenly distributed. This, in turn, improves the stability of the negative electrode structure and, in turn, the battery's cycling performance.

[0139] Furthermore, in the above technical solution, at least one of transition metals, carbides or nitrides is selected as the transition layer. The composition and morphology of these transition layers are conducive to improving the strength of the bonding force with lithium metal, and are conducive to the uniformity of the distribution of the strength of the bonding force; thereby, it is conducive to improving the stability of the negative electrode structure, and further conducive to the cycle performance of the battery.

[0140] Furthermore, lithium metal is highly corrosive, and the contact area between the lithium metal and the negative electrode current collector is subject to catalytic corrosion. If the negative electrode current collector catalytically breaks during battery cycling, it can damage the negative electrode structure. In the above technical solution, by providing a transition layer between the negative electrode current collector and the lithium metal layer, and selecting at least one of a transition metal, carbide, or nitride as the transition layer, it can significantly protect the negative electrode current collector and improve the adhesion between the current collector and the lithium metal as well as the stability of the interface structure. This can significantly improve the structural stability of the negative electrode during battery cycling, thereby improving the battery's cycling performance.

[0141] Furthermore, in some embodiments of the present application, the transition layer includes: any one of transition metals, carbides or nitrides, for example, the transition layer is set as one layer, and the composition of the cover layer is any one of transition metals, carbides or nitrides; in other optional embodiments of the present application, when the transition layer includes: two or more of transition metals, carbides or nitrides, it can be that multiple transition layers are set, for example, two transition layers are set, the lower layer is transition metal, and the upper layer is carbide; further optionally, in other optional embodiments of the present application, when the transition layer includes: two or more of transition metals, carbides or nitrides, different components can be set in different regions within a layer, for example, the transition layer is one layer, part of the region is transition metal, part of the region is carbide, and part of the region is nitride.

[0142] Furthermore, in some embodiments of the present application, the thickness of the transition layer is 500 nm to 2 μm.

[0143] In the above technical solution, by setting the thickness of the transition layer to 500 nm to 2 μm, it is beneficial to improve the structural stability of the negative electrode during the battery cycle, thereby improving the cycle performance of the battery.

[0144] Illustratively, in some embodiments of the present application, the thickness of the transition layer is 500nm, 600nm, 800nm, 900nm, 1μm, 1.1μm, 1.2μm, 1.5μm, 1.6μm, 1.8μm, 2μm or a range between any two of the aforementioned values.

[0145] Further optionally, in some embodiments of the present application, the thickness of the above-mentioned transition layer is 500nm~600nm, 600nm~700nm, 700nm~800nm, 800nm~900nm, 900nm~1μm, 1μm~1.1μm, 1.1μm~1.2μm, 1.2μm~1.3μm, 1.3μm~1.4μm, 1.4μm~1.5μm, 1.5μm~1.6μm, 1.6μm~1.7μm, 1.7μm~1.8μm, 1.8μm~1.9μm or 1.9μm~2.0μm.

[0146] Furthermore, in some embodiments of the present application, the transition metal includes at least one of magnesium, bismuth, tin, zinc, cobalt, aluminum, palladium, silver or gold.

[0147] It should be noted that the above-mentioned transition metals can be pure metals or alloys, such as any one of pure magnesium, pure bismuth, pure tin, pure zinc, pure cobalt, pure aluminum, pure palladium, pure silver, or pure gold. In other optional embodiments, when the transition metal includes two or more of magnesium, bismuth, tin, zinc, cobalt, aluminum, palladium, silver, or gold, two or more pure metals or alloys of multiple metals can be selected. For example, two transition metals are selected, namely pure magnesium and pure bismuth, or two transition metals are selected, which are alloys of magnesium and bismuth.

[0148] Furthermore, in some embodiments of the present application, the carbide includes at least one of carbon nanotubes, graphene, Ketjen black, or carbon black.

[0149] Illustratively, in some embodiments of the present application, the carbide includes: any one of carbon nanotubes, graphene, Ketjen black or carbon black; or in some embodiments of the present application, the above-mentioned carbide includes: a mixture of carbon nanotubes and graphene, and the two can be mixed in any proportion; or in some embodiments of the present application, the above-mentioned carbide includes: a mixture of carbon nanotubes, graphene, Ketjen black and carbon black, and the four can be mixed in any proportion.

[0150] Furthermore, in some embodiments of the present application, the nitride includes at least one of carbon trinitride tetranitride, aluminum nitride or boron nitride.

[0151] Illustratively, in some embodiments of the present application, the above-mentioned nitride includes: any one of carbon trinitride tetranitride, aluminum nitride or boron nitride; or in some embodiments of the present application, the above-mentioned nitride includes: a mixture of carbon trinitride tetranitride and aluminum nitride; the two can be mixed in any proportion; or in some embodiments of the present application, the above-mentioned nitride includes: a mixture of carbon trinitride tetranitride, aluminum nitride and boron nitride; the three can be mixed in any proportion.

[0152] Furthermore, in some embodiments of the present application, the method for preparing the negative electrode sheet includes:

[0153] Lithium metal is rolled onto the first surface and the second surface of the negative electrode current collector to form a lithium metal layer.

[0154] The above technical solution, which rolls lithium metal onto the first and second surfaces of the negative electrode current collector, can greatly improve the problem of pulverization and collapse that easily occurs during the cycle when lithium metal is used as the negative electrode plate, thereby improving the cycle performance of the battery.

[0155] Further optionally, in some embodiments of the present application, the rolling of the lithium metal onto the first surface and the second surface of the negative electrode current collector may be performed at 200° C. to 220° C. using a smooth roller.

[0156] In the above technical solution, the lithium metal is rolled onto the first and second surfaces of the negative electrode current collector at 200°C to 220°C. Compared with rolling at room temperature, hot pressing is less likely to produce large differences in indentations on the lithium metal surface. Within the above temperature range, the lithium is in a fluid state and can be tightly bonded to the negative electrode current collector, which can further reduce the difference in indentations on the lithium metal surface, which is beneficial to improving the surface consistency of the lithium metal layer; thus, it is beneficial to the cycle performance of the battery. Further optionally, in some embodiments of the present application, rolling the lithium metal onto the first and second surfaces of the negative electrode current collector includes:

[0157] At 200°C, 202°C, 205°C, 208°C, 210°C, 212°C, 215°C, 218°C, 220°C or in the range between any two of the foregoing values; rolling the lithium metal onto the first surface and the second surface of the negative electrode collector.

[0158] Furthermore, in some embodiments of the present application, a second rolling is performed on the surface of the formed lithium metal layer.

[0159] Rolling the negative electrode current collector and the lithium metal layer together in one step may result in large differences in the indentations on the lithium metal surface and poor consistency. In the above technical solution, by performing a second rolling on the surface of the formed lithium metal layer, the consistency of the surface state of the lithium metal layer can be improved. It is also beneficial to reduce the roughness of the lithium metal surface by rolling it to a suitable range. The surface state of lithium metal, that is, the size of the roughness, affects the nucleation and growth of lithium ions. Excessive roughness will lead to dendrite growth; on the contrary, a smooth surface will make initial nucleation difficult and polarization severe.

[0160] The above technical solution is conducive to reducing the roughness of the lithium metal layer surface by rolling it to Sa of 0.5μm~50μm and / or Sz of 10μm~90μm; within this roughness range, the roughness is appropriate, which is conducive to the initial nucleation of lithium metal; it can effectively reduce the overpotential, reduce the battery impedance, and improve the cycle performance.

[0161] Furthermore, in some embodiments of the present application, the second rolling on the surface of the formed lithium metal layer comprises:

[0162] A second rolling is performed on the surface of the formed lithium metal layer.

[0163] Furthermore, in some embodiments of the present application, a second rolling is performed on the surface of the formed lithium metal layer, comprising:

[0164] At room temperature, a second rolling is performed on the surface of the formed lithium metal layer using a roller having protrusions on the circumference.

[0165] In the above technical solution, a second rolling is performed on the surface of the formed lithium metal layer by using a roller with protrusions; the roller with protrusions on the surface can effectively change the surface roughness of the lithium metal, which is beneficial to the cycle performance of the battery.

[0166] Furthermore, in some embodiments of the present application, the protrusion satisfies at least one of the following characteristics:

[0167] (1) The cross-sectional shape of the protrusion is circular;

[0168] (2) The height of the protrusion is 0.5 mm to 1.5 mm;

[0169] (3) The diameter of the protrusion is 1 mm to 2 mm.

[0170] Further optionally, in some embodiments of the present application, the height of the protrusion is 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm or a range between any two of the foregoing values.

[0171] Further optionally, in some embodiments of the present application, the diameter of the protrusion is 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, 2 mm or a range between any two of the foregoing values.

[0172] It should be further explained that the cross-sectional shape of the protrusion may not be a circle in a strict sense, for example, a shape approximately circular is also acceptable.

[0173] Furthermore, in some embodiments of the present application, the first surface and the second surface of the negative electrode current collector include a transition layer;

[0174] Rolling lithium metal onto the first surface and the second surface of the negative electrode current collector to form a lithium metal layer includes: rolling the lithium metal onto the transition layer to form the lithium metal layer.

[0175] In the above technical solution, by depositing a transition layer, the morphology of the negative electrode current collector further changes with the deposited material, and the coating with higher roughness can improve the adhesion with lithium metal; and is conducive to the uniformity of the distribution of the strength of the adhesion; thereby, it is beneficial to improve the stability of the negative electrode structure, and further beneficial to the cycle performance of the battery.

[0176] Furthermore, in some embodiments of the present application, before forming the transition layer, the method further includes:

[0177] The negative electrode current collector is roughened and then a transition layer is deposited.

[0178] The above technical solution roughens the negative electrode current collector, and can make the roughness of the negative electrode current collector include: Ra of 0.2μm to 3μm; and / or Rz of 2.5μm to 6μm.

[0179] Further optionally, illustratively, in some embodiments of the present application,

[0180] The negative electrode current collector is roughened, so that the roughness of the negative electrode current collector includes: Ra is 0.2μm, 0.3μm, 0.5μm, 0.8μm, 1μm, 1.5μm, 1.8μm, 2μm, 2.5μm, 2.8μm, 3μm or the range between any two of the foregoing values; Rz is 2.5μm, 2.8μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 5.8μm, 6μm or the range between any two of the foregoing values.

[0181] In the above technical solution, cleaning the negative electrode current collector removes oxides, dirt, or impurities from its surface, exposing a fresh surface (e.g., a fresh copper foil surface), thereby achieving a coarsened surface morphology within the aforementioned roughness range. A clean and further coarsened negative electrode current collector surface facilitates increased adhesion to the transition layer. After deposition of the transition layer, the negative electrode current collector morphology further changes with the deposited material, and a rougher coating layer enhances adhesion to lithium metal, thereby improving battery cycling performance.

[0182] Furthermore, in some embodiments of the present application, roughening includes:

[0183] The negative electrode current collector is roughened by plasma etching, laser cleaning or hydrochloric acid immersion.

[0184] In the above technical solution, the negative electrode current collector is roughened by plasma etching, laser cleaning or hydrochloric acid immersion; the surface of the negative electrode current collector can be cleaned and roughened to obtain a roughened surface morphology, which is beneficial to improving the adhesion between the transition layer and the negative electrode current collector; after the transition layer is deposited, the morphology of the negative electrode current collector further changes with the deposited material, and the coating with higher roughness can improve the adhesion with lithium metal, which is beneficial to improving the battery cycle performance.

[0185] Furthermore, illustratively, in some embodiments of the present application, laser cleaning can be performed in a high-purity argon atmosphere with a power of 150W to 200W and a time of 50S to 60S.

[0186] Furthermore, in some embodiments of the present application, forming a transition layer includes:

[0187] The transition metal, carbide or nitride is deposited as the transition layer by means of electrodeposition, magnetron sputtering or doctor blade coating.

[0188] In the above technical solution, transition metals, carbides or nitrides can be deposited on the negative electrode current collector by electrodeposition, magnetron sputtering or doctor blade coating as a transition layer to improve the adhesion between the negative electrode current collector and lithium metal.

[0189]

[0190] Some specific embodiments are listed below to better illustrate the present application.

[0191] Example 1-1

[0192] A negative electrode sheet is provided, which is prepared according to the following method:

[0193] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0194] Using a smooth roller at 200°C, lithium metal was rolled onto the first and second surfaces of the negative electrode current collector. The thickness of the lithium metal layer on both surfaces was 20 μm (the lithium metal surface had not been roughened, as shown in Figure 7a of the accompanying drawings). The lithium metal layer was then rolled a second time using a room-temperature roller with raised surfaces (raised 1 mm in height, 1 mm in diameter, and 0.5 mm in spacing) to change the surface roughness of the lithium metal layer; the roughness of the lithium metal layer was: Sa: 2 μm; Sz: 12 μm (as shown in Figure 7b of the accompanying drawings).

[0195] Example 1-2 to Example 1-14

[0196] A negative electrode plate is provided, and the preparation method is the same as that of Example 1; the difference lies in the parameters of the negative electrode plate, see Table 1 for details.

[0197] Examples 1-15

[0198] A negative electrode plate is provided, and a copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0199] Lithium metal was rolled onto the first and second surfaces of the negative electrode current collector using a smooth roller at 200°C. The thickness of the lithium metal layer on both surfaces was 20 μm (the lithium metal surface had not been roughened, as shown in Figure 7a of the accompanying drawings).

[0200] Example 2-1

[0201] A negative electrode sheet is provided, which is prepared according to the following method:

[0202] A copper foil with a thickness of 8 μm was used as the negative electrode current collector (see the micrograph in Figure a of the accompanying drawings 8 and the SEM image in Figure a of Figure 9 ).

[0203] The copper foil surface was cleaned and etched using hydrochloric acid to achieve cleanliness and roughening (see the micrograph in Figure 8b of the accompanying drawings). Then, the transition metal Mg was deposited on the first and second surfaces of the copper foil by electroplating to a thickness of 1 μm, forming a transition layer (see the SEM image in Figure 9b of the accompanying drawings).

[0204] Then, a smooth roller at 200°C was used to roll lithium metal onto both surfaces of the transition layer. The thickness of the lithium metal layer on both surfaces was 20 μm.

[0205] Example 2-2 to Example 2-5

[0206] A negative electrode plate is provided, which is prepared in the same manner as in Example 2-1, except for the composition of the transition layer, as detailed in Table 2.

[0207] Examples 2-6

[0208] A negative electrode sheet is provided, which is prepared according to the following method:

[0209] An 8μm thick copper foil was used as the negative electrode current collector. The copper foil surface was cleaned and roughened using hydrochloric acid cleaning and etching. Carbon nanotubes were then spray-coated onto both the first and second surfaces of the copper foil to a thickness of 1μm, forming a transition layer.

[0210] Then, a smooth roller at 200°C was used to roll lithium metal onto both surfaces of the transition layer. The thickness of the lithium metal layer on both surfaces was 20 μm.

[0211] Example 2-7 to Example 2-10

[0212] A negative electrode plate is provided, which is prepared in the same manner as in Example 2-6, except for the negative electrode plate parameters, as detailed in Table 2.

[0213] Example 2-11

[0214] A negative electrode sheet is provided, which is prepared according to the following method:

[0215] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0216] The copper foil surface is treated by cleaning and etching with hydrochloric acid to achieve cleaning and roughening.

[0217] Then, lithium metal was rolled onto both surfaces of the treated copper foil using a smooth roller at 200°C. The thickness of the lithium metal layer on both surfaces was 20 μm.

[0218] Example 3-1

[0219] A negative electrode sheet is provided, which is prepared according to the following method:

[0220] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0221] The copper foil surface was cleaned and roughened by cleaning and etching with hydrochloric acid. Then, transition metal silver was deposited on the first and second surfaces of the copper foil by electroplating with a thickness of 1 μm to form a transition layer.

[0222] Then, a smooth roller at 200°C was used to roll lithium metal onto both surfaces of the transition layer. The thickness of the lithium metal layer on both surfaces was 20 μm.

[0223] Then, a roller at room temperature with protrusions on the surface (protrusion height 1 mm, diameter 1 mm, protrusion spacing 0.5 mm) is used to perform a second rolling on the lithium metal layer to change the surface roughness of the lithium metal layer; the roughness of the lithium metal layer is: Sa: 2 μm; Sz: 12 μm.

[0224] Example 3-2 to Example 3-5

[0225] A negative electrode plate is provided, which is prepared in the same manner as in Example 3-1, except for the negative electrode plate parameters, as detailed in Table 3.

[0226]

Battery preparation

[0227] S1. Preparation of positive electrode sheet

[0228] The ternary cathode material NCM811 (LiNi 0.8 Co 0.1 Mn 0.1Mix the following materials: O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) in a weight ratio of 96:2.5:1.5. Add an appropriate amount of solvent, N-methylpyrrolidone (NMP), and stir evenly to obtain a positive electrode slurry. Apply the positive electrode slurry onto aluminum foil and dry it after coating to obtain a positive electrode sheet.

[0229] S2. Preparation of electrolyte

[0230] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 is dissolved in a mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte.

[0231] S3, isolation film

[0232] A polypropylene film with a thickness of 12 μm was selected.

[0233] S4. Prepare battery

[0234] The negative electrode sheets, separators and positive electrode sheets prepared in the above embodiments are placed in order, with the separators placed between the positive and negative electrode sheets to play a role of isolation, and then the electrolyte is injected and the electrodes are processed and formed.

[0235]

Performance test

[0236] The performance test of each battery is as follows:

[0237] 1. Cyclic performance test method

[0238] The batteries prepared in each embodiment were used as test objects. At 25°C, the battery was charged at a constant current of 0.1C to a voltage of 5V, then charged at a constant voltage of 5V to a current of 0.02C. After standing for 5 minutes, the battery was discharged at a constant current of 0.1C to a voltage of 3.0V. This is a charge and discharge cycle process, and the first charge and discharge capacity in grams is obtained (which can be directly read on a blue-electric test device). Then, a cyclic charge and discharge test was performed according to the above method until the discharge specific capacity decayed to 80% of the first discharge specific capacity. The number of cycles of the batteries corresponding to each embodiment or comparative example was recorded to obtain the cycle performance in Tables 1 to 3.

[0239] 2. Lithium metal nucleation overpotential test of negative electrode

[0240] S1. Disassemble the negative electrode sheets of each embodiment, soak the disassembled negative electrode sheets in DMC, and then dry them. After the negative electrode sheets are dried, assemble them with lithium metal to form a single half-cell. During the assembly process, ensure that the size of the negative electrode sheet is greater than or equal to the lithium sheet;

[0241] S2, inject 2mL of electrolyte into the assembled single-chip half-cell, let it stand overnight, put it on the clamp, and perform charge and discharge test. The specific steps are: make the half-cell 2 The battery was discharged at a current density of 100 nm for 3 hours, and then charged to 1 V at the same current density. The charge and discharge voltage curve of the first cycle was drawn. The absolute value of the minimum voltage (deposition overpotential) on the discharge voltage curve minus the stable voltage (diffusion overpotential) on the charge curve was the lithium metal nucleation overpotential of the negative electrode.

[0242] The battery performance test results are shown in Tables 1 to 3.

[0243] Table 1

[0244] Table 2

[0245] Table 3

[0246] From the above table data we can see that:

[0247] In each group of embodiments of the present application, the nucleation overpotential of the battery is relatively appropriate (between 3.1V and 3.95V), and the cycle performance is good.

[0248] Furthermore, it can be seen from Table 1 that when Sa is 25-28 and Sz is 60-70, the nucleation overpotential of the battery is appropriate (between 3.4V and 3.5V) and the cycle performance is better.

[0249] Furthermore, by comparing Table 3 with Table 1 and Table 2, it can be seen that by setting a transition layer and roughening the surface of lithium metal, the two can achieve synergistic efficiency, which is further beneficial to improving the battery cycle performance.

[0250] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate comprises: a negative electrode current collector having a first surface and an opposing second surface; and A lithium metal layer; the lithium metal layer is supported on the first surface and the second surface of the negative electrode current collector.

2. The negative electrode sheet according to claim 1, characterized in that: The roughness of the surface of the lithium metal layer includes: Sa is 0.5 μm to 50 μm.

3. The negative electrode sheet according to claim 1 or 2, characterized in that: The roughness of the surface of the lithium metal layer includes: Sz is 10 μm to 90 μm.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The roughness of the surface of the lithium metal layer includes: Sa is 25 μm to 28 μm.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The roughness of the surface of the lithium metal layer includes: Sz is 60 μm to 70 μm.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The thickness of the lithium metal layer is 5 μm to 50 μm.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The thickness of the negative electrode current collector is 5 μm to 15 μm.

8. The negative electrode sheet according to any one of claims 1 to 7, characterized in that: The negative electrode plate further includes: a transition layer; The transition layer is located between the negative electrode current collector and the lithium metal layer; The transition layer includes at least one of a transition metal, a carbide or a nitride.

9. The negative electrode sheet according to claim 8, characterized in that: The thickness of the transition layer is 500 nm to 2 μm.

10. The negative electrode sheet according to claim 8 or 9, characterized in that: The transition metal comprises at least one of magnesium, bismuth, tin, zinc, cobalt, aluminum, palladium, silver or gold; and / or The carbide comprises: at least one of carbon nanotubes, graphene, Ketjen black or carbon black; and / or The nitride includes at least one of carbon trinitride, aluminum nitride or boron nitride.

11. The method for preparing a negative electrode sheet according to any one of claims 1 to 10, characterized in that: include: Lithium metal is rolled onto the first surface and the second surface of the negative electrode current collector to form the lithium metal layer.

12. The method for preparing a negative electrode sheet according to claim 11, wherein: The method comprises: A second rolling is performed on the surface of the formed lithium metal layer.

13. The method for preparing a negative electrode sheet according to any one of claims 11 to 12, characterized in that: The step of rolling the lithium metal onto the first surface and the second surface of the negative electrode current collector comprises: The lithium metal is rolled on the first surface and the second surface of the negative electrode current collector at 200° C. to 220° C.

14. The method for preparing a negative electrode sheet according to any one of claims 11 to 13, characterized in that: The second rolling is performed on the surface of the formed lithium metal layer, comprising: A roller with protrusions on its circumference is used to perform a second rolling on the surface of the formed lithium metal layer.

15. The method for preparing a negative electrode sheet according to claim 14, characterized in that: The protrusion satisfies at least one of the following characteristics: (1) The cross-sectional shape of the protrusion is circular; (2) The height of the protrusion is 0.5 mm to 1.5 mm; (3) The diameter of the protrusion is 1 mm to 2 mm.

16. The method for preparing a negative electrode sheet according to any one of claims 11 to 15, characterized in that: include: The first surface and the second surface of the negative electrode current collector include a transition layer; The step of rolling the lithium metal onto the first surface and the second surface of the negative electrode current collector to form the lithium metal layer comprises: The lithium metal is rolled onto the transition layer to form the lithium metal layer.

17. The method for preparing a negative electrode sheet according to claim 16, wherein: Before forming the transition layer, the method further includes: The negative electrode current collector is roughened, and then the transition layer is deposited.

18. The method for preparing a negative electrode sheet according to claim 17, wherein: The roughening includes: The negative electrode current collector is roughened by plasma etching, laser cleaning or hydrochloric acid immersion.

19. The method for preparing a negative electrode sheet according to any one of claims 16 to 18, characterized in that: Forming the transition layer includes: The transition layer is formed by depositing transition metal, carbide or nitride by means of electrodeposition, magnetron sputtering or doctor blade coating.

20. A battery, characterized in that: The battery comprises the negative electrode sheet according to any one of claims 1 to 19.

21. An electrical device, characterized in that: The electric device comprises the battery according to claim 20.

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