WO2019210673A1 - 一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途 - Google Patents

一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途 Download PDF

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WO2019210673A1
WO2019210673A1 PCT/CN2018/114646 CN2018114646W WO2019210673A1 WO 2019210673 A1 WO2019210673 A1 WO 2019210673A1 CN 2018114646 W CN2018114646 W CN 2018114646W WO 2019210673 A1 WO2019210673 A1 WO 2019210673A1
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Prior art keywords
current collector
copper sheet
lithium
micro
pattern
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English (en)
French (fr)
Inventor
程鑫
卢周广
李志强
张腾飞
黄兴隆
张雨
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Southern University of Science and Technology
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Southern University of Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/78—Shapes other than plane or cylindrical, e.g. helical
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to the field of battery technology, for example, to a current collector that effectively inhibits the uncontrolled growth of dendrites of a lithium metal battery, a method of preparing the same, and uses thereof.
  • lithium metal is a very promising high energy density anode material in lithium batteries because of its theoretical capacity of up to 3860 mA ⁇ h/g and a very low redox potential (relative to standard hydrogen electrodes).
  • -3.04V redox potential
  • lithium metal plays a key role in meeting the demand for high energy density batteries for electric vehicles and advanced electronic equipment for new and growing applications.
  • the formation of lithium dendrites with low coulombic efficiency hinders the practical application of lithium metal anodes for rechargeable lithium batteries.
  • the generation of lithium dendrites and the dead lithium it produces may cause safety problems such as thermal runaway or even burning, or explosion.
  • the biomimetic method can be improved by using a 3D collector to bond the polymer electrolyte.
  • the uncontrollable lithium dendrite problem is an urgent problem to be solved in the development of rechargeable lithium batteries based on lithium metal anodes.
  • the present disclosure provides a current collector that effectively inhibits the uncontrolled growth of dendrites of a lithium metal battery, a method of preparing the same, and uses thereof.
  • a current collector that effectively inhibits the uncontrolled growth of dendrites of a lithium metal battery, a method of preparing the same, and uses thereof.
  • the present disclosure provides a current collector that is a copper sheet having a concave structure.
  • the recessed structure includes a pit structure and/or a groove structure.
  • the "pit and/or groove” means that it may be a pit structure, a groove structure, or a combination of a pit structure and a groove structure.
  • the recessed structure of the present disclosure includes, but is not limited to, a pit structure and/or a groove structure, and other regular or irregular recess structures are also suitable for the solution of the present disclosure, and the groove may be a straight groove or a curved shape.
  • a groove which may be a pit having a square cross section (referred to as a square pit for short), a pit having a circular cross section (referred to as a circular pit for short), or a pit having an elliptical horizontal cross section (abbreviated as Oval pits, etc.
  • the pit structure and/or the groove structure is a micro/nano structure pattern.
  • micro/nano structure as used in the present disclosure means that the structure is on a two-dimensional plane perpendicular to the depth of the pit and/or the groove, and the dimension of at least one dimension is on the order of micrometers or nanometers, the micrometer level or nanometer.
  • the level may be, for example, 50 nm to 900 ⁇ m, for example, 50 nm, 60 nm, 80 nm, 100 nm, 150 nm, 200 nm, 300 nm, 350 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m. 70 ⁇ m, 150 ⁇ m, 200 ⁇ m, 300 ⁇ m, 400 ⁇ m, 500 ⁇ m, 600 ⁇ m, 700 ⁇ m, 800 ⁇ m or 900 ⁇ m, and the like.
  • the "at least one dimension" may be one dimension of a two-dimensional plane or two dimensions of a two-dimensional plane.
  • micro/nano structure pattern refers to a pattern formed by a plurality of micro/nano structures in a two-dimensional plane perpendicular to the depth of the pits and/or grooves, the plurality of which may be, for example, two per square centimeter.
  • 10 3 to 10 8 in the dimensional plane, for example, 10 3 , 3 ⁇ 10 3 , 5 ⁇ 10 3 , 8 ⁇ 10 3 , 10 4 , 2 ⁇ 10 4 , 5 ⁇ 10 4 , 7.5 ⁇ 10 4 , 10 5 , 1.5 ⁇ 10 5 , 3 ⁇ 10 5 , 6.5 ⁇ 10 5 , 8 ⁇ 10 5 , 10 6 , 2 ⁇ 10 6 , 4 ⁇ 10 6 , 6 ⁇ 10 6 , 8 ⁇ 10 6 , 10 7 , 2.5 ⁇ 10 7 , 3.5 ⁇ 10 7 , 6.5 ⁇ 10 7 , 8.5 ⁇ 10 7 or 10 8 , etc.
  • the micro-nano structure pattern is a regular periodic pattern.
  • the copper sheet has a thickness of 10 ⁇ m to 100 ⁇ m, such as 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, or 100 ⁇ m.
  • the pits and/or grooves have a depth of 5 ⁇ m to 50 ⁇ m, such as 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 25 ⁇ m, 28 ⁇ m, 30 ⁇ m, 33 ⁇ m, 36 ⁇ m, 40 ⁇ m, 45 ⁇ m or 50 ⁇ m. Wait.
  • the depth of the pits and/or grooves is from 10 ⁇ m to 15 ⁇ m, and within this range of 10 ⁇ m to 15 ⁇ m, the deposited lithium has a suitable capacity and a good deposition effect.
  • the depth of the pits and/or grooves is 1/10 to 1 times the minimum line width, for example, 1/10, 1/9, 1/8, 1/7.5, 1/7, 1/6, 1/5, 1/4, 1/3, 1/2 or 1 etc. Within this range, pit and/or groove structures are less difficult to manufacture, and lithium is more easily deposited in a tightly packed form. .
  • the "minimum line width" as used in the present disclosure refers to the minimum distance between two points passing through the center of the plane on the plane perpendicular to the depth of the pits and/or grooves.
  • the minimum line width refers to the distance in the width direction of the strip; for a rectangular pit, the minimum line width refers to the distance of the wide side; for a square pit, the minimum line width refers to The distance of the side length; for an elliptical pit, the minimum line width refers to the distance of the short side of the ellipse.
  • the present disclosure allows lithium to be deposited mostly within the recess pattern by adjusting the distribution of current density, and the deposited lithium changes from dendritic to globular. This greatly inhibits the growth of lithium dendrites.
  • lithium is preferentially deposited in depressions, such as pits and/or grooves, especially in micro-nano structure pits and/or grooves, which provides space for the growth of lithium dendrites, thereby effectively
  • the growth of lithium dendrites in the lithium metal battery is suppressed, the phenomenon of piercing the battery separator is avoided, and the performance of the lithium battery is improved.
  • the present disclosure provides a method for preparing the current collector, the method comprising:
  • a polymer layer is formed on the copper sheet, and the polymer layer has a recessed structure, and then the copper sheet is placed in a copper etching solution for etching, and finally the polymer layer is removed to obtain a copper sheet having a concave structure, that is, a set. fluid.
  • the copper sheet is a clean copper sheet.
  • the polymer layer is a resist layer
  • the resist layer may be, for example, a photoresist layer or a nanoimprint layer.
  • the method of forming a polymer layer on a copper sheet is a spin coating method, and the uniformity of the polymer layer can be improved by spin coating.
  • the copper etchant has a main component of FeCl3 and HCl.
  • concentration of each component in the copper etching solution is not specifically limited in the present disclosure, and those skilled in the art can select as needed, as long as the purpose of etching can be achieved.
  • the etching time is from 1 min to 10 min, such as 1 min, 3 min, 4 min, 5 min, 6 min, 7 min, 9 min or 10 min.
  • the recessed structure comprises a pit structure and/or a groove structure.
  • the pit structure and/or the groove structure is a micro/nano structure pattern.
  • the method uses a photolithographic method to form a resist layer having a recessed structure of micro-nano patterns on a copper sheet.
  • the method includes the steps of: applying a resist (such as a photoresist) on a copper sheet, then performing exposure using a pattern on the mask, and finally developing a micro/nano pattern, thereby A concave structure is formed on the copper sheet.
  • a resist such as a photoresist
  • the method uses a nanoimprint lithography technique to fabricate a resist layer (such as a nanoimprint adhesive layer) having a micro/nano structure on a copper sheet.
  • a resist layer such as a nanoimprint adhesive layer
  • the method includes the steps of: coating a nano-imprinted adhesive on a copper sheet, and then replicating the micro-nano structure on the flexible template to the nano-imprinted adhesive on the copper sheet by roll-to-roll nanoimprinting. on.
  • the present disclosure provides a method for preparing the current collector, the method comprising:
  • the copper sheet is hot-embossed with a patterned alumina sheet as a template, and the pattern is transferred onto the copper sheet to obtain a copper sheet having a concave structure, that is, a current collector.
  • the copper sheet is formed into a recessed structure by using an alumina sheet having a convex structure in the step (2).
  • the hot stamping of the step (3) of the present disclosure may be a high temperature hot stamping of 700 ° C to 800 ° C.
  • the alumina sheet of step (1) is a clean alumina sheet.
  • the polymer layer in the step (1) is a photoresist.
  • the method of forming the polymer layer in the step (1) is a spin coating method, and the uniformity of the polymer layer can be improved by the spin coating method.
  • the present disclosure does not limit the convex shape of the step (2), and is designed according to the desired concave shape, which is a conventional technique in the art, and will not be described herein.
  • the recessed structure includes, but is not limited to, a pit structure and/or a groove structure, and other regular or irregular recessed structures are also suitable for the solution of the present disclosure, and the groove may be a straight groove or a curved shape.
  • a groove which may be a pit having a square cross section (referred to as a square pit), a pit having a horizontal cross section (referred to as a circular pit) or a pit having an elliptical horizontal cross section (abbreviation It is an oval pit) and so on.
  • the step (1) is: coating a photoresist on the alumina sheet, then performing exposure using a pattern on the mask, and finally developing a micro/nano pattern.
  • the etching in step (2) is inductively coupled plasma etching (ICP) or reactive ion etching (RIE).
  • ICP inductively coupled plasma etching
  • RIE reactive ion etching
  • the present disclosure provides a negative electrode including the current collector and a lithium layer deposited on the current collector, the lithium layer having a thickness less than or equal to a depth of the recess.
  • the formed negative electrode when the thickness of the deposited lithium layer is less than the thickness of the polymer layer, the formed negative electrode still has a depressed structure; when the thickness of the deposited lithium layer is equal to the thickness of the polymer layer, the lithium formed in the depressed portion is just When the recess is filled, the formed negative electrode no longer has a recessed structure, and the structure which just fills the recess is more advantageous for avoiding dendrite growth and improving the performance of the lithium battery.
  • the thickness of the lithium layer is 1/2 to 1 times the depth of the recess.
  • the thickness of the lithium layer is equal to the depth of the recess.
  • the present disclosure provides a lithium metal battery comprising the negative electrode.
  • the present disclosure provides a lithium metal battery
  • the negative electrode of the lithium metal battery is the negative electrode
  • the lithium metal battery further includes a positive electrode, a separator, an electrolyte, and a battery case.
  • the embodiments of the present disclosure provide a novel current collector, which is a copper sheet having a concave structure (such as a structure having pits or grooves), by depositing less than or equal to the polymer on the current collector.
  • a lithium layer of a layer thickness is obtained to obtain a negative electrode, which can effectively control the problem of free growth of dendrites of a lithium metal battery.
  • the present disclosure can be mass-produced for a copper current collector with a micro-nano structure of surface-free dendritic lithium, which is easy to commercialize. If we use our optimized wet etching copper plate with micro-nano structure as the current collector, then deposit the appropriate lithium as the battery negative electrode, LiFePO 4 (LFP) material as the battery positive electrode, and the capacity retention rate after the battery is cycled for 150 cycles. More than 90%, and ordinary copper sheets for current collectors have a capacity retention rate of less than 70%. This highlights the advantage of copper as a current collector with a micro/nano structure that inhibits lithium dendrite growth during cell cycling.
  • LFP LiFePO 4
  • micro-nano processing technology adopted in an embodiment of the present disclosure is mature and stable, and can realize precise control of the graphic size, and can be produced from nanometer to micrometer-level patterns.
  • FIG. 1 is a process flow diagram of preparing a current collector having micro-nano structure pits according to an embodiment of the present disclosure.
  • FIG. 2 is a schematic view of the finished product of a current collector having micro-nano structure pits according to an embodiment of the present disclosure.
  • FIG. 3 is a process flow diagram of preparing a current collector having micro-nano structure pits according to an embodiment of the present disclosure.
  • FIG. 5 is an SEM image obtained by depositing lithium on a copper sheet obtained by wet etching and degumming according to an embodiment of the present disclosure.
  • 6a-6d are SEM results of a conventional smooth copper electrodeposited lithium metal (lithium having a capacity of 2 mA ⁇ h/cm 2 at a current density of 0.5 mA/cm 2 ) according to an embodiment of the present disclosure, wherein 6a-Fig. 6d are scanning electron micrographs taken at 40 times, 400 times, 3,000 times and 25 thousand times, respectively, and Fig. 6b is an enlarged view of the block diagram area in Fig. 6a, and Fig. 6c is an enlarged view of the block diagram area in Fig. 6b Figure 6d is an enlarged view of the area of the block diagram of Figure 6c.
  • 6e and 6f are SEM results of a conventional smooth copper electrodeposited lithium metal (deposited lithium with a capacity of 4 mA ⁇ h/cm 2 at a current density of 0.5 mA/cm 2 ) according to an embodiment of the present disclosure, wherein 6e and FIG. 6f are scanning electron micrographs taken at 2 thousand times and 10 thousand times, respectively.
  • FIGS. 7a-7d are SEM results of a wet-etched copper sheet electrodeposited lithium metal (a lithium having a capacity of 2 mA ⁇ h/cm 2 at a current density of 0.5 mA/cm 2 ) according to an embodiment of the present disclosure.
  • FIG. 8a and 8b are a half-battery formed by using a common copper sheet according to an embodiment of the present disclosure and a wet-etched copper sheet provided by an embodiment of the present disclosure, and forming a half-cell with a metal lithium sheet, and charging and discharging.
  • the discharge voltage distribution map wherein FIG. 8a corresponds to a common copper sheet, and FIG. 8b corresponds to a wet-etched copper sheet.
  • FIG. 9 is a coulombic efficiency comparison diagram of a battery made of a conventional copper piece and a wet-etched copper piece provided as a current collector according to an embodiment of the present disclosure.
  • the embodiment provides a method for preparing a current collector having micro-nano structure pits, comprising: first forming a micro-nano pattern pit on a copper sheet with a photoresist, then etching the copper sheet, and finally removing the photoresist. , more specifically, including (see Figure 1 for the process flow):
  • a layer of photoresist is spin-coated on a clean copper sheet, and then the pattern on the mask is exposed by a lithography machine, and finally the micro-nano pattern is developed;
  • the copper piece is placed in a copper etching solution for etching for 3 to 5 minutes, and finally the photoresist is removed to obtain a copper piece having a micro-nano structure pit, that is, a current collector (see FIG. 2 for the effect of the current collector product).
  • the thickness of the copper sheet is 100 ⁇ m
  • the depth of the micro-nano structure pit is 8 ⁇ m
  • the pits of the micro-nano structure are square pits
  • the side length of the square is 30 ⁇ m
  • the pits of the micro-nano structure are uniformly and uniformly distributed on the copper sheet.
  • FIG. 4 is an SEM image of a copper sheet obtained by wet etching and degumming in the present embodiment. It can be seen from the figure that the etched copper sheet forms uniform pits before etching.
  • lithium is deposited on the copper sheet obtained by wet etching and degumming, and after SEM is performed, the SEM image is shown in Fig. 5. It can be seen from the figure that lithium is uniformly engraved in the form of small balls. The surface of the copper sheet is deposited.
  • the ordinary smooth copper piece and the wet-etched copper piece of the embodiment 1 are respectively assembled into a button type battery with the lithium piece, wherein the battery case is 2025 type, the stainless steel pad is added on both sides, the lithium piece thickness is 500 ⁇ m, the diameter is 16 mm, and the electrolysis is performed.
  • the solution was 1M LiPF 6 dissolved in EC/DMC (1:1) and purchased from New Zebang Technology Co., Ltd.
  • the assembled battery was left for 12 hours, and then a lithium having a capacity of 2 mA ⁇ h/cm 2 was deposited at a current density of 0.5 mA/cm 2 (deposition time was 4 h), and charging and discharging were performed at 0.5 mA/cm 2 (the charging and discharging time was 2h) Test, cycle 30 cycles, and finally the lithium deposition onto the copper sheet has a capacity of about 2 mA ⁇ h/cm 2 . Then, the battery was disassembled into a glove box, and the copper current collector was taken out and rinsed with dimethyl carbonate, and then dried, and characterized by a scanning electron microscope.
  • FIGS. 6a-6d are SEM results of a conventional smooth copper electrodeposited lithium metal (deposited with a capacity of 2 mA ⁇ h/cm 2 at a current density of 0.5 mA/cm 2 ), wherein FIGS. 6 a to 6 d are respectively Scanning electron micrographs taken at 40 times, 400 times, 3,000 times, and 25 thousand times, and Fig. 6b is an enlarged view of the block diagram area of Fig. 6a, Fig. 6c is an enlarged view of the block diagram area of Fig. 6b, and Fig. 6d is Fig. 6c An enlarged view of the block diagram area, as shown in the figure, Figure 6a shows the unstable uniformity of deposition of lithium metal on the copper surface. Figure 6c can clearly observe the local presence of lithium dendrites. Figure 6d can clearly observe the size and size of dendrites. .
  • the present disclosure also investigates the variation of lithium dendrites as the deposition time is extended, the specific operations are:
  • Fig. 6e and Fig. 6f are SEM results of a conventional smooth copper electrodeposited lithium metal (deposited lithium having a capacity of 4 mA ⁇ h/cm 2 at a current density of 0.5 mA/cm 2 ), wherein Fig. 6e and Fig. 6f are respectively 2 Scanning electron micrographs taken at thousand times and 10 thousand times, the surface is almost all dendrites can be observed from Fig. 6e and Fig. 6f.
  • Fig. 6a - Fig. 6d it can be known that as the deposition time increases, the lithium branches The crystal change is more obvious.
  • FIG. 7a-7c are SEM results of the wet-etched copper sheet electrodeposited metallic lithium of Example 1 (deposited lithium at a current density of 0.5 mA/cm 2 at a current density of 2 mA ⁇ h/cm 2 ), wherein, FIG. 7a- Fig. 7c is a scanning electron micrograph taken at 140 times, 1000 times and 10000 times, respectively. From Fig. 7a and Fig. 7b, we can observe that lithium is preferentially deposited on the slope of the small pit and is small in size, and there is no Produces distinct lithium dendrites. It can be seen from Fig. 7c that a part of the lithium sphere is also generated at the bottom of the small pit, and the radius of the lithium sphere is about 100 nm.
  • the present disclosure also investigates the deposition of lithium dendrites at different current densities:
  • the present disclosure also investigates whether lithium dendrites are generated when the cycle is rotated at a higher number of turns of 100 cycles.
  • the specific operation is as follows:
  • the assembled battery was left for 12 hours, and then a lithium having a capacity of 2 mA ⁇ h/cm 2 was deposited at a current density of 0.5 mA/cm 2 (deposition time was 4 h), and charging and discharging were performed at 0.5 mA/cm 2 (the charging and discharging time was 2h) Test, cycle 100 cycles and then perform the same operation as in Example 2 above.
  • Fig. 7d is a scan result obtained after 100 cycles of charge and discharge (charge and discharge time of 2 h) at 0.5 mA/cm 2 after deposition of lithium. It can be seen that after 100 cycles, no lithium was observed.
  • the dendritic phenomenon indicates that the copper plate current collector with micro-nano structure pits prepared by wet etching can significantly inhibit the generation of lithium dendrites within a limited range of lithium deposition and circulation.
  • the present disclosure also investigates the effect of a conventional copper sheet and the wet-etched copper sheet of Example 1 on the performance of the battery.
  • the specific operation is as follows:
  • a common copper piece and the wet-etched copper piece of Example 1 were respectively deposited with lithium of 2 mA ⁇ h/cm 2 and then formed into a half-cell with a lithium metal plate, and a corresponding polarization curve was obtained by charging and discharging, specifically at 0.5 mA/cm. charge and discharge current density of 2 cycle (charge and discharge times are 2H), above loop coil 200, the charge and discharge voltage profile shown in Figure 8a and 8b, wherein Figure 8a corresponding to ordinary copper, 8b corresponding to FIG Example 1 wet embodiment Etched copper sheet. It can be seen from Fig. 8a that there is no obvious increase in the over-potential in the first 200 hours.
  • the coulombic efficiency exhibited by the conventional copper sheet and the wet etched copper sheet of Example 1 as a current collector in the battery Specifically, lithium metal of 1 mA ⁇ h/cm 2 is deposited on the current collector, and then assembled into a Cu-Li symmetric battery with a lithium sheet for charge and discharge cycles, and the charge and discharge current density is 0.5 mA/cm 2 (the charge and discharge time are both 2h), the coulombic efficiency diagram of the battery is shown in Figure 9. It can be seen from the figure that the battery assembled by the ordinary copper current collector shows that the coulombic efficiency is continuously lowered as the charge and discharge progress, indicating that some of the lithium has become dead lithium and is lost. The wet etched copper current collector assembled battery showed good coulombic efficiency, especially after circulating more than 150 cycles, and the coulombic efficiency was 99%.
  • This embodiment provides a method for preparing a current collector having micro-nano structure pits, including (see FIG. 3 for process flow):
  • a layer of photoresist is spin-coated on a clean copper sheet, and then the pattern on the mask is exposed by a lithography machine, and finally the micro-nano pattern is developed;
  • the micro-nano pattern is etched on the alumina sheet by inductively coupled plasma etching (ICP). Finally, the patterned aluminum oxide sheet is used as a template to hot-imprint the copper sheet, and the pattern is transferred to the copper sheet to obtain a micro-pattern.
  • the thickness of the copper sheet was 100 ⁇ m, and the depth of the micro-nano structure pit was 12 ⁇ m.
  • the present embodiment provides a negative electrode comprising the current collector of Embodiment 1, and a lithium layer formed on the current collector, the lithium layer having a thickness of 6 ⁇ m.
  • the present embodiment provides a negative electrode comprising the current collector of Embodiment 2, and a lithium layer formed on the current collector, the lithium layer having a thickness of 8 ⁇ m.
  • the present embodiment provides a negative electrode comprising the current collector of Embodiment 3, and a lithium layer formed on the current collector, the lithium layer having a thickness of 12 ⁇ m.
  • the embodiments provided by the present disclosure are prepared by using a current collector of a specific structure to obtain a negative electrode having a concave structure, which can effectively control the free growth problem of dendrites of a lithium metal battery.
  • lithium is preferentially deposited in the recess of the negative electrode, such as pits (such as micro-nano structure pits) and/or grooves, which provides space for the growth of lithium dendrites, thereby effectively inhibiting lithium
  • pits such as micro-nano structure pits
  • grooves which provides space for the growth of lithium dendrites, thereby effectively inhibiting lithium
  • the growth of lithium dendrites in metal batteries avoids the phenomenon of piercing the battery separator and improves the performance of the lithium battery.

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Abstract

本公开提供了一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途。该集流体为具有凹陷结构的铜片，通过采用该特定结构的集流体制备负极，可以有效抑制锂金属电池枝晶不可控生长，避免了刺穿电池隔膜的现象，提高了锂电池的性能。

Description

一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途 技术领域
本公开涉及电池技术领域，例如涉及一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途。
背景技术
相关技术中，提高锂离子电池能量密度是商业化锂电池行业长期发展的一个重要追求方向，然而，由于商业化的石墨负极它的理论容量只有372mA·h/g，限制了电池的应用，还有许多负极材料如硅、锡、过度金属氧化物等都可以用于取代目前商业化的石墨负极。
除了上述这些材料外，锂金属是基于锂电池中一个非常有前途的高能量密度负极材料，因为它的理论容量高达3860mA·h/g，而且有一个很低的氧化还原电位(相对标准氢电极为-3.04V)，因此，锂金属在满足针对日益增长新型应用的电动汽车和先进的电子设备对高能量密度电池的需求中起着关键作用。然而，锂金属电池在充放电循环过程中，锂枝晶的形成伴随着低的库伦效率阻碍了锂金属负极用于可充放电锂电池的实际应用。尤其是，锂枝晶的产生和它产生的死锂可能会导致出现诸如热失控甚至燃烧、或爆炸等安全问题。
相关技术中，通过在锂金属上面涂一层LiF，或者在电解液中加聚硫化物、LiNO 3、Cs +、离子液体等，使用3D收集器结合高分子电解液，生物仿生的方法可以改善锂金属表面的SEI(solid electrolyte interphase)膜等。
以上技术，对不可控锂枝晶生长的改善程度是很有限的，它们不能大规模的应用于高通量的工业化生产。
总之，不可控的锂枝晶问题是发展基于锂金属负极的可充电锂电池急需解决的问题。
发明内容
本公开提供一种有效抑制锂金属电池枝晶不可控生长的集流体、其制备方法及用途。通过采用本公开所述的集流体并在其表面形成合适厚度的锂形成负极，能够有效抑制锂金属电池枝晶不可控生长。
本公开在一实施例中提供一种集流体，所述集流体为具有凹陷结构的铜片。
在一示例性实施例中，所述凹陷结构包括凹坑结构和/或凹槽结构。所述“凹坑和/或凹槽”指：可以是凹坑结构，也可以是凹槽结构，还可以是凹坑结构和 凹槽结构的组合。
本公开的凹陷结构包括但不限于凹坑结构和/或凹槽结构，其他规则的或不规则的凹陷结构也适用于本公开的方案，所述凹槽可以是直槽也可以是弯曲状的槽，所述凹坑可以是水平截面为方形的凹坑(简称方形凹坑)、水平截面为圆形的凹坑(简称为圆形凹坑)或水平截面为椭圆形的凹坑(简称为椭圆形凹坑)等。
在一实施例中，所述凹坑结构和/或凹槽结构为微纳结构图形。
本公开所述“微纳结构”指：该结构在与凹坑和/或凹槽的深度垂直方向所在二维平面上，至少一个维度的尺寸为微米级别或纳米级别，所述微米级别或纳米级别例如可以是50nm～900μm，例如50nm、60nm、80nm、100nm、150nm、200nm、300nm、350nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、10μm、20μm、30μm、40μm、50μm、60μm、70μm、150μm、200μm、300μm、400μm、500μm、600μm、700μm、800μm或900μm等。所述“至少一个维度”可以是二维平面的一个维度，也可以是二维平面的两个维度。
本公开所述“微纳结构图形”指：多个微纳结构在与凹坑和/或凹槽的深度垂直方向所在二维平面内形成的图形，所述多个例如可以是每平方厘米二维平面内有10 3～10 8个，例如10 3个、3×10 3个、5×10 3个、8×10 3个、10 4个、2×10 4个、5×10 4个、7.5×10 4个、10 5个、1.5×10 5个、3×10 5个、6.5×10 5个、8×10 5个、10 6个、2×10 6个、4×10 6个、6×10 6个、8×10 6个、10 7个、2.5×10 7个、3.5×10 7个、6.5×10 7个、8.5×10 7个或10 8个等。
在一实施例中，所述微纳结构图形为规则的周期性图形。
在一实施例中，所述铜片的厚度为10μm～100μm，例如10μm、20μm、30μm、40μm、50μm、60μm、70μm、80μm、90μm或100μm等。
在一实施例中，所述凹坑和/或凹槽的深度为5μm～50μm，例如5μm、8μm、10μm、15μm、18μm、20μm、25μm、28μm、30μm、33μm、36μm、40μm、45μm或50μm等。
在一实施例中，所述凹坑和/或凹槽的深度为10μm～15μm，在此范围10μm～15μm内，所沉积的锂容量合适，且沉积效果较好。
在一实施例中，所述凹坑和/或凹槽的深度为最小线宽的1/10～1倍，例如1/10、1/9、1/8、1/7.5、1/7、1/6、1/5、1/4、1/3、1/2或1等，在此范围内，凹 坑和/或凹槽结构制造难度更低，锂更容易以紧密堆积的形式沉积。
本公开所述“最小线宽”指：与凹坑和/或凹槽的深度垂直方向所在平面上，穿过平面中心的两点的最小距离。例如，对于一个长条形的凹槽，最小线宽指长条的宽度方向的距离；对于一个长方形的凹坑，最小线宽指宽边的距离；对于一个正方形的凹坑，最小线宽指边长的距离；对于一个椭圆形的凹坑，最小线宽指椭圆短边的距离。
在一实施例中，本公开通过调节电流密度的分布，可以使得锂大多沉积在凹陷图案里面，并且沉积的锂由枝晶状变成了小球状。这极大抑制了锂枝晶的生长。
在电池充放电过程中，锂优先沉积在凹陷处，比如凹坑和/或凹槽，尤其是微纳结构凹坑和/或凹槽处，这为锂枝晶的生长提供了空间，从而有效抑制了锂金属电池中锂枝晶的生长、避免了刺穿电池隔膜的现象，提高了锂电池的性能。
本公开在一实施例中提供所述的集流体的制备方法，所述方法包括：
首先在铜片上形成高分子层，并使高分子层具有凹陷结构，然后再把铜片放入铜刻蚀液中进行刻蚀，最后去掉高分子层，得到具有凹陷结构的铜片，即集流体。
在一实施例中，所述铜片为洁净的铜片。
在一实施例中，所述高分子层为抗蚀剂层，所述抗蚀剂层例如可以是光刻胶层或纳米压印层等。
在一实施例中，在铜片上形成高分子层的方法为旋涂的方法，采用旋涂的方法可以提高高分子层的均匀性。
在一实施例中，所述铜刻蚀液的主要成分为FeCl3和HCl。本公开对铜刻蚀液中各组分的浓度不作具体限定，本领域技术人员可根据需要进行选择，只要能达到刻蚀的目的即可。
在一实施例中，所述刻蚀的时间为1min～10min，例如1min、3min、4min、5min、6min、7min、9min或10min等。
在一实施例中，所述凹陷结构包括凹坑结构和/或凹槽结构。
在一实施例中，所述凹坑结构和/或凹槽结构为微纳结构图形。
在一实施例中，所述方法采用光刻的方法在铜片上形成具有微纳图案的凹 陷结构的抗蚀剂层。
在一示例性实施例中，所述方法包括如下步骤：在铜片上涂覆抗蚀剂(比如光刻胶)，然后利用掩膜板上的图形进行曝光，最后显影出微纳图案，从而在铜片上做出凹陷结构。
在一实施例中，所述方法使用纳米压印光刻技术在铜片上制作具有微纳结构的抗蚀剂层(比如纳米压印胶层)。
在一示例性实施例中，所述方法包括如下步骤：在铜片上涂覆纳米压印胶，然后利用卷对卷纳米压印将柔性模板上的微纳结构复制到铜片上的纳米压印胶上。
本公开在一实施例中提供所述的集流体的制备方法，所述方法包括：
(1)在氧化铝片上形成高分子层，并使高分子层具有凸起结构；
(2)刻蚀，从而得到具有凸起结构的氧化铝片，也即得到了图形化的氧化铝片；
(3)以图形化的氧化铝片作模板热压印铜片，将图形转移到铜片上，从而得到具有凹陷结构的铜片，即集流体。
本公开中，采用步骤(2)具有凸起结构的氧化铝片压印铜片后使铜片形成凹陷结构。
在一实施例中，本公开步骤(3)所述热压印可以是700℃～800℃的高温热压印。
在一实施例中，步骤(1)所述氧化铝片为洁净的氧化铝片。
在一实施例中，步骤(1)所述高分子层为光刻胶。
在一实施例中，步骤(1)形成高分子层的方法为旋涂的方法，采用旋涂的方法可以提高高分子层的均匀性。
本公开对步骤(2)的凸起形状不作限定，其是根据所需要得到的凹陷形状进行设计的，其是本领域的常规技术，此处不再赘述。
本公开中，凹陷结构包括但不限于凹坑结构和/或凹槽结构，其他规则的或不规则的凹陷结构也适用于本公开的方案，所述凹槽可以是直槽也可以是弯曲状的槽，所述凹坑可以是水平截面为方形的凹坑(简称方形凹坑)、水平截面为圆形的凹坑(简称为圆形凹坑)或水平截面为椭圆形的凹坑(简称为椭圆形 凹坑)等。
在一实施例中，步骤(1)为：在氧化铝片上涂覆光刻胶，然后利用掩膜板上的图形进行曝光，最后显影出微纳图案。
在一实施例中，步骤(2)所述刻蚀为电感耦合等离子体刻蚀(ICP)或反应离子刻蚀(RIE)。
本公开在一实施例中提供一种负极，所述负极包括所述的集流体，及沉积于所述集流体上的锂层，所述锂层的厚度小于等于凹陷的深度。
本公开中，当沉积得到的锂层的厚度小于高分子层厚度时，形成的负极仍然具有凹陷结构；当沉积得到的锂层的厚度等于高分子层厚度时，形成于凹陷处的锂刚好将凹陷填满，形成的负极不再具有凹陷结构，这种恰好填满凹陷的结构更有利于避免枝晶生长，提高锂电池的性能。
在一实施例中，所述锂层的厚度为凹陷深度的1/2～1倍。
在一实施例中，所述锂层的厚度等于凹陷的深度。
本公开在一实施例中提供一种锂金属电池，所述锂金属电池包含所述的负极。
本公开在一实施例中提供了一种锂金属电池，所述锂金属电池的负极为所述的负极，所述锂金属电池还包括正极、隔膜、电解液和电池壳等部件。
与相关技术相比，本公开实施例提供了一种新型的集流体，其为具有凹陷结构(比如具有凹坑或凹槽等结构)的铜片，通过在该集流体上沉积小于等于高分子层厚度的锂层而得到负极，可以有效控制锂金属电池枝晶的自由生长问题。
本公开可以针对表面无枝晶锂的带有微纳结构的铜集流体进行批量生产，容易商业化。如使用我们优化的湿法刻蚀的带有微纳结构的铜片作集流体，再沉积合适的锂作电池负极，LiFePO 4(LFP)材料作电池正极，电池循环150圈以后容量保留率达到了90％以上，而普通的铜片作集流体只有不到70％的容量保留率。这凸显了带有微纳结构的铜作集流体在电池循环过程中抑制锂枝晶生长的优势。
本公开在一实施例中采用的微纳加工技术，工艺成熟稳定，可实现图形尺寸的精确控制，从纳米级到微米级别的图案均可制作。
附图说明
附图用来提供对本公开技术方案的进一步理解，并且构成说明书的一部分，与本申请的实施例一起用于解释本公开的技术方案，并不构成对本公开技术方案的限制。
图1是本公开一实施例提供的制备具有微纳结构凹坑的集流体的工艺流程图。
图2是本公开一实施例提供的具有微纳结构凹坑的集流体的成品效果图。
图3是本公开一实施例提供的制备具有微纳结构凹坑的集流体的工艺流程图。
图4是本公开一实施例提供的湿法刻蚀并去胶后得到的铜片的SEM图。
图5是本公开一实施例提供的湿法刻蚀并去胶后得到的铜片上沉积锂后得到的SEM图。
图6a-图6d是本公开一实施例提供的普通的光滑铜片电沉积锂金属(0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂)后的SEM结果，其中，图6a-图6d分别依次是40倍、400倍、3千倍和25千倍下拍摄的扫描电镜图，且图6b是图6a中框图区域的放大图，图6c是图6b中框图区域的放大图，图6d是图6c框图区域的放大图。
图6e和图6f是本公开一实施例提供的普通的光滑铜片电沉积锂金属(0.5mA/cm 2电流密度下沉积4mA·h/cm 2容量的锂)后的SEM结果，其中，图6e和图6f分别是2千倍和10千倍下拍摄的扫描电镜图。
图7a-图7d是本公开一实施例提供的湿法刻蚀的铜片电沉积锂金属(0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂)后的SEM结果。
图8a和图8b是采用本公开一实施例提供的普通铜片和本公开一实施例提供的湿法刻蚀的铜片分别沉积锂后与金属锂片组成半电池，充放电后得到的充 放电电压分布图，其中，图8a对应普通铜片，图8b对应湿法刻蚀的铜片。
图9为采用本公开一实施例提供的普通铜片和本公开一实施例提供的湿法刻蚀的铜片作为集流体制成的电池的库伦效率对比图。
具体实施例
实施例1
本实施例提供一种具有微纳结构凹坑的集流体的制备方法，包括：首先在铜片上用光刻胶做出微纳图案凹坑，然后对铜片进行刻蚀，最后去掉光刻胶，更具体地，包括(工艺流程参见图1)：
首先在洁净的铜片上旋涂一层光刻胶，然后通过光刻机将掩膜板上的图形进行曝光，最后显影出微纳图案；
然后在把铜片放入铜刻蚀液中刻蚀3～5min，最后去掉光刻胶，得到具有微纳结构凹坑的铜片，即集流体(集流体成品效果图参见图2)。
集流体中，铜片的厚度为100μm，微纳结构凹坑的深度为8μm，微纳结构凹坑为方形凹坑，方形的边长为30μm，微纳结构凹坑均匀整齐分布在铜片上。
图4为本实施例湿法刻蚀并去胶后得到的铜片的SEM图，由图可以看出，相比刻蚀前，刻蚀后的铜片形成了均匀的凹坑。
在本实施例湿法刻蚀并去胶后得到的铜片上沉积锂，沉积完成后进行SEM表征，得到的SEM图见图5，由图可以看出，锂以小球的形式均匀地在刻蚀铜片表面沉积。
实施例2
首先我们把普通铜片和实施例1湿法刻蚀的铜片分别用乙醇、丙酮、0.1M盐酸超声清洗0.5h，剪成1cm 2的小方块烘干放入手套箱备用。
采用普通的光滑铜片和实施例1湿法刻蚀的铜片，分别与锂片组装成扣式电池，其中电池壳为2025型，两边加不锈钢垫片，锂片厚度500μm，直径16mm，电解液为1M LiPF 6溶于EC/DMC(1∶1)，购自新宙邦科技公司。装好的电池放置12小时，然后在0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂(沉积时间为4h)，0.5mA/cm 2下进行充放电(充放时间都为2h)测试，循环30圈，最终使得锂沉积到铜片上容量约为2mA·h/cm 2。然后转入手套箱拆卸电池，取出铜集流体用碳酸二甲酯润洗再放干，用扫描电镜表征。
结果分析：
图6a-图6d是普通的光滑铜片电沉积锂金属(0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂)后的SEM结果，其中，图6a-图6d分别依次是40倍、400倍、3千倍和25千倍下拍摄的扫描电镜图，且图6b是图6a中框图区域的放大图，图6c是图6b中框图区域的放大图，图6d是图6c框图区域的放大图，由图可知，图6a显示锂金属在铜表面沉积的不稳定均一，图6c能明显地观察到局部有锂枝晶，图6d能清晰地观察到枝晶的大小及尺寸。
本公开还研究了随着沉积时间延长，锂枝晶的变化，具体操作为：
装好的电池放置12小时后，在0.5mA/cm 2电流密度下沉积4mA·h/cm 2容量的锂(沉积时间为8h)，然后再进行上述实施例2相同的操作。
图6e和图6f是普通的光滑铜片电沉积锂金属(0.5mA/cm 2电流密度下沉积4mA·h/cm 2容量的锂)后的SEM结果，其中，图6e和图6f分别是2千倍和10千倍下拍摄的扫描电镜图，由图6e和图6f可观察到表面几乎都是枝晶，通过与图6a-图6d的对比，可以知道，随着沉积时间的增长，锂枝晶变的更加明显。
图7a-图7c是实施例1湿法刻蚀的铜片电沉积金属锂(0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂)后的SEM结果，其中，图7a-图7c分别依次是140倍、1000倍和10000倍下拍摄的扫描电镜图，由图7a和图7b我们可以观察到，锂优先在小凹坑的斜坡上沉积，而且呈小颗粒状，并没有产生明显的锂枝晶。由图7c可知，小凹坑底部也有部分锂球产生，锂球半径大概100nm。
本公开还研究了不同电流密度下沉积，锂枝晶的变化：
我们做了不同电流密度下的沉积作对比，发现随着电流密度从0.1mA/cm 2到4mA/cm 2的增大，锂球半径越小，就如图7d所示，但当电流密度大于4mA/cm 2时，会造成局部沉积不均匀导致了锂沉积来不及成核。在集流体表面沉积的锂球，抑制了枝晶的生长，大大提高了锂金属电池的性能，尤其是阻止了由于枝晶刺破隔膜造成电池短路的问题。
本公开还研究了循环更高的圈数100圈时是否会有锂枝晶产生，具体操作为：
装好的电池放置12小时，然后在0.5mA/cm 2电流密度下沉积2mA·h/cm 2容量的锂(沉积时间为4h)，0.5mA/cm 2下进行充放电(充放时间都为2h)测试，循环100圈然后再进行上述实施例2相同的操作。
图7d是沉积锂后，在0.5mA/cm 2下进行充放电(充放时间都为2h)循环100圈后得到的扫描结果，有图可以看出，循环100圈后，依然没有观察到锂枝晶现象，说明在有限的锂沉积和循环范围内，用湿法刻蚀制备得到的具有微纳结构凹坑的铜片集流体可以明显的抑制锂枝晶的产生。
本公开还研究了普通铜片和实施例1湿法刻蚀的铜片对电池性能的影响， 具体操作为：
将普通铜片和实施例1湿法刻蚀的铜片分别沉积2mA·h/cm 2的锂后与金属锂片组成半电池，充放电获得相应的极化曲线，具体是在0.5mA/cm 2电流密度下充放电循环(充放时间都是2h)，循环200圈以上，其充放电电压分布图见图8a和图8b，其中，图8a对应普通铜片，图8b对应实施例1湿法刻蚀的铜片。由图8a可知，前200个小时过电位并没有很明显的增大，由于循环前期锂是足够供应的，而且产生的枝晶有限，当从第50圈开始电压曲线的极化增大，过电位明显增大，而且变得越来越大，直到最后短路，这是由于产生了死锂损耗和枝晶问题。而图8b使用刻蚀铜作集流体的充放电电压分布曲线表明，最初几个循环过电势很高，可能由于内部没有形成稳定的SEI膜导致，随着充放电继续进行，过电势变得越来越小而且稳定。这说明刻蚀铜作集流体明显地提高了电池的性能，改善和避免了了由于锂枝晶产生导致的过电位不稳定和短路。我们还做了其他不同电流密度下的充放电极化曲线，发现几乎不同的电流密度情况下，刻蚀铜相比铜集流体都表现了优越的电池性能。
为了提高电池中锂的利用率，我们还做了普通铜片和实施例1湿法刻蚀铜片作集流体在电池中所表现的库仑效率。具体地，在集流体上沉积1mA·h/cm2的锂金属，然后与锂片组装成Cu-Li对称电池进行充放电循环，充放电电流密度为0.5mA/cm 2，(充放时间都是2h)，电池的库伦效率图见图9。由图可以看出，普通铜集流体组装的电池表现出随着充放电的进行，库仑效率不断地降低，说明有部分锂变成了死锂而损失掉了。而湿法刻蚀铜片集流体做组装的电池却表现出了良好的库仑效率，尤其是在循环了150圈以上，库仑效率还有99％。
实施例3
本实施例提供一种具有微纳结构凹坑的集流体的制备方法，包括(工艺流程参见图3)：
首先在洁净的铜片上旋涂一层光刻胶，然后通过光刻机将掩膜板上的图形进行曝光，最后显影出微纳图案；
然后通过电感耦合等离子体刻蚀(ICP)的方法在氧化铝片上刻蚀出微纳图案，最后以图形化的氧化铝片作模板热压印铜片，将图形转移到铜片上，得到具有微纳结构凹坑的铜片，即集流体。
集流体中，铜片的厚度为100μm，微纳结构凹坑的深度为12μm。
实施例4
本实施例提供一种负极，所述负极包括实施例1的集流体，及形成于所述集流体上的锂层，锂层的厚度为6μm。
实施例5
本实施例提供一种负极，所述负极包括实施例2的集流体，及形成于所述集流体上的锂层，锂层的厚度为8μm。
实施例6
本实施例提供一种负极，所述负极包括实施例3的集流体，及形成于所述集流体上的锂层，锂层的厚度为12μm。
本公开提供的实施例采用特定结构的集流体制备得到具有凹陷结构的负极，可以有效控制锂金属电池枝晶的自由生长问题。
在电池充放电过程中，锂优先沉积在负极的凹陷处，比如凹坑(比如微纳结构凹坑)和/或凹槽处，这为锂枝晶的生长提供了空间，从而有效抑制了锂金 属电池中锂枝晶的生长、避免了刺穿电池隔膜的现象，提高了锂电池的性能。
申请人声明，本公开通过上述实施例来说明本申请的详细方法，但本公开并不局限于上述详细方法，即不意味着本公开必须依赖上述详细方法才能实施。所属技术领域的技术人员应该明了，对本公开的任何改进，对本公开产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本公开的保护范围和公开范围之内。

Claims (31)

  1. 一种集流体，所述集流体为具有凹陷结构的铜片。
  2. 根据权利要求1所述的集流体，其中，所述凹陷结构包括凹坑结构和/或凹槽结构。
  3. 根据权利要求2所述的集流体，其中，所述凹坑结构和/或凹槽结构为微纳结构图形。
  4. 根据权利要求3所述的集流体，其中，所述微纳结构图形为规则的周期性图形。
  5. 根据权利要求1-4任一项所述的集流体，其中，所述铜片的厚度为10μm～100μm。
  6. 根据权利要求2-5任一项所述的集流体，其中，所述凹坑和/或凹槽的深度为5μm～50μm。
  7. 根据权利要求6所述的集流体，其中，所述凹坑和/或凹槽的深度为10μm～15μm。
  8. 根据权利要求2-7任一项所述的集流体，其中，所述凹坑和/或凹槽的深度为最小线宽的1/10～1倍。
  9. 如权利要求1-8任一项所述的集流体的制备方法，所述方法包括：
    首先在铜片上形成高分子层，并使高分子层具有凹陷结构，然后再把铜片放入铜刻蚀液中进行刻蚀，最后去掉高分子层，得到具有凹陷结构的铜片，即集流体。
  10. 根据权利要求9所述的方法，其中，所述铜片为洁净的铜片。
  11. 根据权利要求9或10所述的方法，其中，所述高分子层为抗蚀剂层。
  12. 根据权利要求11所述的方法，其中，所述高分子层为光刻胶层或纳米 压印胶层。
  13. 根据权利要求9-12任一项所述的方法，其中，在铜片上形成高分子层的方法为旋涂的方法。
  14. 根据权利要求9-13任一项所述的方法，其中，所述铜刻蚀液的主要成分为FeCl 3和HCl。
  15. 根据权利要求9-14任一项所述的方法，其中，所述刻蚀的时间为1min～10min。
  16. 根据权利要求9-15任一项所述的方法，其中，所述凹陷结构包括凹坑结构和/或凹槽结构。
  17. 根据权利要求16所述的方法，其中，所述凹坑结构和/或凹槽结构为微纳结构图形。
  18. 根据权利要求9-17任一项所述的方法，所述方法中，采用光刻的方法在铜片上形成具有微纳图案的凹陷结构的抗蚀剂层。
  19. 根据权利要求18所述的方法，所述方法包括如下步骤：在铜片上涂覆光刻胶，然后利用掩膜板上的图形进行曝光，最后显影出微纳图案，从而在铜片上做出微纳图案的凹陷结构。
  20. 根据权利要求9-17任一项所述的方法，所述方法中，使用纳米压印光刻技术在铜片上制作具有微纳结构的抗蚀剂层。
  21. 根据权利要求20所述的方法，所述方法包括如下步骤：在铜片上涂覆纳米压印胶，然后利用卷对卷纳米压印将柔性模板上的微纳结构复制到铜片上的纳米压印胶上。
  22. 如权利要求1-8任一项所述的集流体的制备方法，所述方法包括：
    (1)在氧化铝片上制作高分子层，并使高分子层具有凸起结构；
    (2)刻蚀，从而得到具有凸起结构的氧化铝片，也即得到了图形化的氧化铝片；
    (3)以图形化的氧化铝片作模板热压印铜片，将图形转移到铜片上，从而得到具有凹陷结构的铜片，即集流体。
  23. 根据权利要求22所述的方法，其中，步骤(1)所述氧化铝片为洁净的氧化铝片。
  24. 根据权利要求22或23所述的方法，其中，步骤(1)所述高分子层为光刻胶。
  25. 根据权利要求22-24任一项所述的方法，其中，步骤(1)形成高分子层的方法为旋涂的方法。
  26. 根据权利要求22-25任一项所述的方法，其中，步骤(1)为：在氧化铝片上涂覆光刻胶，然后利用掩膜板上的图形进行曝光，最后显影出微纳图案。
  27. 根据权利要求22-26任一项所述的方法，其中，步骤(2)所述刻蚀为电感耦合等离子体刻蚀或反应离子刻蚀。
  28. 一种负极，所述负极包括权利要求1-8任一项所述的集流体，及沉积于所述集流体上的锂层，所述锂层的厚度小于等于凹陷的深度。
  29. 根据权利要求28所述的负极，其中，所述锂层的厚度为凹陷深度的1/2～1倍。
  30. 根据权利要求29所述的负极，其中，所述锂层的厚度等于凹陷的深度。
  31. 一种锂金属电池，所述锂金属电池包含权利要求28-30任一项所述的负极。
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