Three-dimensional lithium negative electrode, preparation method thereof and lithium battery

Abstract

The present application relates to the technical field of lithium battery, especially to a method for preparing three-dimensional lithium negative electrode by pulse liquid drop jet deposition, three-dimensional lithium negative electrode and lithium secondary battery. The method for preparing three-dimensional lithium negative electrode comprises: providing conductive material as a substrate; and performing pulse liquid drop jet deposition on the surface of the substrate to form a three-dimensional structure lithium metal thin layer on the surface of the substrate, thereby forming the three-dimensional lithium negative electrode. The present application has the following advantages: (1) preparing ultra-thin lithium metal foil layer with thickness <20 microns; (2) quickly constructing three-dimensional structure lithium metal negative electrode; (3) stable coating of lithium metal surface lithium-conducting polymer-based artificial SEI; (4) high stability and high performance of three-dimensional lithium metal negative electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery, in particular to a method for preparing a three-dimensional lithium anode by pulse liquid droplet jet deposition, a three-dimensional lithium anode and a lithium secondary battery. BACKGROUND

[0002] In view of the pursuit of higher energy density, lithium ion batteries have entered the development trend of transition from traditional graphite anodes to lithium metal anodes. The use of lithium metal anode can provide higher specific capacity and lower potential than the currently commercially dominant graphite anode or gradually commercialized silicon-carbon anode. Although the lithium metal anode has incomparable energy density advantages, it still faces many great challenges such as poor cycle performance, potential safety risks, etc. in practical application.

[0003] The uneven nucleation and growth of lithium dendrites on the surface of the copper current collector are easy to pierce the separator to cause internal short circuit and thermal runaway, and the extremely high reactivity of metal lithium to liquid electrolyte and solid electrolyte is easy to cause the consumption of surface active lithium and the formation of dead lithium, which can easily increase the internal resistance of the battery and reduce the coulomb efficiency, ultimately shorten the cycle life of the battery and cause safety problems, which all become obstacles to the high-performance application of lithium metal anode.

[0004] The current lithium metal anode is still mainly used for small-scale trial production to meet laboratory basic research purposes, usually adopts calendering process, and has not been widely commercialized. The mainstream products are limited to pure lithium foil, lithium (magnesium, aluminum) alloy foil, etc., and the thickness is more than 20 μm. At the same time, it also faces problems such as low production efficiency, high cost, etc. In terms of technology, it lacks key links such as three-dimensional morphology, thickness control, surface treatment and interface modification, which is difficult to meet the high-performance large-scale application.

[0005] Patent CN108807851A discloses a method for preparing a lithium metal battery anode, a protective layer of the lithium metal electrode and a composite electrolyte. The protective layer of the lithium metal electrode has uniform current density and mechanical properties when lithium is deposited. The protective layer of the lithium metal electrode includes a plurality of composite particles: a particle core and a coating layer of at least one ion-conducting material selected from an ion-conducting oligomer containing an ion-conducting unit and an ion-conducting polymer containing an ion-conducting unit disposed on at least a portion of the particle core. However, the ion-conducting material poly(ethylene glycol) diacrylate (PEGDA) needs to be self-polymerized, which is complicated and difficult to realize industrial production.

[0006] Patent CN112216811A discloses a preparation method of an ultrathin lithium metal negative electrode. This method uses electrostatic action to spin a layer of electrochemically stable hybrid lithiumophilic fiber on the surface of copper to achieve stable and uniform lithium deposition, firm lithium negative electrode, and inhibit lithium metal dendrite growth. However, this preparation method is complex, time-consuming (dispersion liquid stirring for 14 h, spinning for 14 h, drying for 12 h, and electroplating for 1 h), and cannot realize industrialized production. SUMMARY

[0007] The purpose of the present application is to overcome the above technical problems and provide a preparation method and surface coating technology of a high-stability and high-performance three-dimensional lithium metal negative electrode.

[0008] To achieve the above purpose, the technical solutions adopted by the present application are as follows.

[0009] In a first aspect, the present application provides a preparation method of a three-dimensional lithium negative electrode.

[0010] A preparation method of a three-dimensional lithium negative electrode, the method comprising:

[0011] providing a conductive material as a substrate; and

[0012] carrying out pulse droplet jet deposition on the surface of the substrate to form a thin layer of lithium metal with a three-dimensional structure on the surface of the substrate, thereby forming the three-dimensional lithium negative electrode.

[0013] Further, the pulse droplet jet deposition is that the molten lithium is sprayed out through a nozzle array with multiple pores to form filaments and / or droplets on the surface of the substrate through a high-frequency pulse controller.

[0014] Further, the substrate is a metal foil.

[0015] Further, the lithium is metal lithium or lithium alloy;

[0016] The lithium alloy includes but is not limited to lithium-silicon, lithium-tin, lithium-aluminum, lithium-indium, lithium-magnesium, and lithium-zinc alloy.

[0017] Further, the substrate is a copper foil current collector.

[0018] The thickness of the thin layer of lithium metal is <20 μm.

[0019] In a second aspect, the present application provides a three-dimensional lithium negative electrode.

[0020] The three-dimensional lithium negative electrode is prepared according to the preparation method of the three-dimensional lithium negative electrode of the first aspect of the present application.

[0021] In a third aspect, the present application provides a lithium secondary battery.

[0022] A lithium secondary battery, said battery comprising the three-dimensional lithium anode according to the second aspect of the present application.

[0023] In a fourth aspect, the present application provides a surface coating method of a three-dimensional lithium anode.

[0024] A surface coating method of a three-dimensional lithium anode, said method comprising coating a PAALi solution on the surface of the three-dimensional lithium anode by spraying or spin-coating or blade-coating, and heating to remove the solvent to obtain a PAALi-coated three-dimensional lithium anode.

[0025] In a specific embodiment, the method further comprises combining the PAALi coating layer with a lithiumophilic inorganic filler to construct an organic-inorganic composite artificial lithium-conducting SEI layer coating structure.

[0026] The lithiumophilic inorganic filler includes but is not limited to Cu2S, Cu7S4, CuF2, Cu3P, SnS2, Cu3N, AlN, CuF2, SnSe, Cu2Se, CuSe, CuSe2, SnF2, SbF3, LiF, MgF2 and Li3N.

[0027] In a fifth aspect, the present application provides a PAALi-coated three-dimensional lithium anode.

[0028] The PAALi-coated three-dimensional lithium anode prepared according to the surface coating method of a three-dimensional lithium anode according to the fourth aspect of the present application.

[0029] In a sixth aspect, the present application provides another lithium secondary battery.

[0030] A lithium secondary battery, said battery comprising the PAALi-coated three-dimensional lithium anode according to the fifth aspect of the present application.

[0031] The three-dimensional lithium anode provided by the present application realizes the construction of a lithium metal three-dimensional microstructure by adopting a pulse liquid droplet jet deposition method, so as to reduce the local current density, inhibit the dendritic growth of lithium, and buffer the volume change of lithium metal in the cycle process. Meanwhile, the preparation method of jet deposition is conducive to the fine control of the deposition amount of the lithium layer, and realizes the preparation of an ultrathin lithium metal layer.

[0032] The three-dimensional lithium anode, the preparation method thereof and the lithium battery provided by the present application can realize the fine control of the thickness of the lithium metal layer and prepare an ultrathin lithium metal layer (thickness < 20 μm) by adjusting the process parameters of the pulse liquid droplet jet deposition.

[0033] By adopting the pulse liquid droplet jet deposition process, discrete island-shaped distributed lithium nanoparticles can be obtained on a substrate (such as a copper current collector) at the same time. The lithium metal layer with a three-dimensional porous structure can reduce the local current density, buffer the volume change of lithium metal in the cycle process, and inhibit the dendritic growth of lithium.

[0034] The application provides a surface coating method of a three-dimensional lithium negative electrode, which coats PAALi solution on the surface of the three-dimensional lithium metal by spraying, spin coating or blade coating, and removes the solvent by heating and drying to obtain a three-dimensional lithium metal thin layer coated with PAALi. The PAALi coating layer can also be combined with a lithiumophilic inorganic filler to construct an organic-inorganic composite artificial lithium-conducting SEI layer coating structure; the lithiumophilic inorganic filler includes but is not limited to Cu2S, Cu7S4, CuF2, Cu3P, SnS2, Cu3N, AlN, CuF2, SnSe, Cu2Se, CuSe, CuSe2, SnF2, SbF3, LiF, MgF2 and Li3N.

[0035] The PAALi polymer layer can block electrons from passing through, inhibit the disordered reduction deposition of lithium ions on the surface of the polymer by obtaining electrons, and further physically isolate the lithium metal from direct contact with the liquid electrolyte or the solid-state electrolyte, thereby preventing the consumption of active lithium and the formation of dead lithium caused by the frequent generation and rupture of the original SEI layer, so as to stop the growth of lithium dendrites and improve the coulombic efficiency, and finally realize the stabilization of the lithium metal interface.

[0036] The method for preparing a three-dimensional lithium negative electrode by pulse droplet jet deposition, the three-dimensional lithium negative electrode and the lithium secondary battery provided by the application provide a new path for the rapid preparation of a three-dimensional lithium metal negative electrode with high interface stability, and help the high-performance application of the lithium metal negative electrode.

[0037] Compared with the prior art, the three-dimensional lithium negative electrode, the preparation method thereof and the lithium battery provided by the application have the following advantages:

[0038] (1) The ultra-thin lithium metal foil layer with a thickness of less than 20 microns is prepared.

[0039] (2) The three-dimensional structure lithium metal negative electrode is quickly constructed.

[0040] (3) The lithium metal surface is stably coated with a lithium-conducting polymer-based artificial SEI.

[0041] (4) The three-dimensional lithium metal negative electrode has high stability and high performance. DETAILED DESCRIPTION

[0042] The above and other aspects, features and advantages of the embodiments of the application will become more apparent by the following description in conjunction with the accompanying drawings, in which:

[0043] Figure 1 The surface morphology of the three-dimensional porous lithium layer prepared by the pulse droplet jet deposition process in Example 1 provided by the application;

[0044] Figure 2Example 2 surface PAALi artificial lithium-ion conducting SEI layer coated three-dimensional porous lithium negative electrode surface morphology provided by the present application;

[0045] Figure 3 Surface morphology of commercial lithium sheet without surface coating in the comparative example provided by the present application;

[0046] Figure 4 Comparison of cycle performance of lithium symmetric battery morphology provided by the present application. DETAILED DESCRIPTION

[0047] In order for those skilled in the art to better understand the technical solutions of the present application, the following examples further describe the present application in detail, and the following examples are only used to illustrate the present application, but not to limit the scope of the present application.

[0048] In a first aspect, the present application provides a preparation method of a three-dimensional lithium negative electrode.

[0049] A preparation method of a three-dimensional lithium negative electrode, the method comprising:

[0050] providing a conductive material as a substrate; and

[0051] performing pulse droplet jet deposition on the surface of the substrate to form a thin layer of lithium metal with a three-dimensional structure on the surface of the substrate, thereby forming the three-dimensional lithium negative electrode.

[0052] Further, the pulse droplet jet deposition is that the molten lithium is sprayed out through a nozzle array with multiple pores to form filaments and / or droplets on the substrate surface by a high-frequency pulse controller.

[0053] Further, the substrate is a metal foil.

[0054] Further, the lithium is metal lithium or lithium alloy;

[0055] The lithium alloy includes but is not limited to lithium-silicon, lithium-tin, lithium-aluminum, lithium-indium, lithium-magnesium, lithium-zinc alloy.

[0056] Further, the substrate is a copper foil current collector.

[0057] The thickness of the thin layer of lithium metal is <20 μm.

[0058] In a second aspect, the present application provides a three-dimensional lithium negative electrode.

[0059] The three-dimensional lithium negative electrode is prepared according to the preparation method of the three-dimensional lithium negative electrode of the first aspect of the present application.

[0060] In a third aspect, the present application provides a lithium secondary battery.

[0061] A lithium secondary battery, said battery comprising the three-dimensional lithium anode according to the second aspect of the present application.

[0062] In a fourth aspect, the present application provides a method for coating the surface of a three-dimensional lithium anode.

[0063] A method for coating the surface of a three-dimensional lithium anode, said method comprising coating the surface of a three-dimensional lithium anode with a PAALi solution by spraying or spin-coating or blade-coating, and heating to remove the solvent to obtain a PAALi-coated three-dimensional lithium anode.

[0064] In a specific embodiment, the method further comprises combining the PAALi coating layer with a lithiumophilic inorganic filler to construct an organic-inorganic composite artificial lithium-conducting SEI layer coating structure.

[0065] The lithiumophilic inorganic filler includes, but is not limited to, Cu2S, Cu7S4, CuF2, Cu3P, SnS2, Cu3N, AlN, CuF2, SnSe, Cu2Se, CuSe, CuSe2, SnF2, SbF3, LiF, MgF2 and Li3N.

[0066] In a fifth aspect, the present application provides a PAALi-coated three-dimensional lithium anode.

[0067] A PAALi-coated three-dimensional lithium anode prepared according to the method for coating the surface of a three-dimensional lithium anode according to the fourth aspect of the present application.

[0068] In a sixth aspect, the present application provides another lithium secondary battery.

[0069] A lithium secondary battery, said battery comprising the PAALi-coated three-dimensional lithium anode according to the fifth aspect of the present application.

[0070] Example 1

[0071] In combination Figure 1 As shown, the molten lithium heated to above 182°C is sprayed through a nozzle array with multiple pores to form fine filaments or droplets, which are then dropped on the copper foil current collector to form a thin layer of lithium metal with a three-dimensional structure.

[0072] The copper foil current collector has a width of 9 μm and a width of 200 mm, and the running speed is 10 cm / min, and the nozzle diameter is 0.5 mm. The injection rate of the molten lithium in the high-frequency pulse controller is 0.3 mL / min, the temperature is maintained at about 190°C, the nozzle distance from the copper foil current collector is about 50 cm, and the droplet pulse frequency is 1500 times / min. Under this experimental condition, the size of the lithium metal particles deposited on the copper current collector is about 3-5 μm, and the overall thickness is about 15 μm.

[0073] Example 2

[0074] In combination Figure 2 As shown, the coating method is spin coating (2000 rpm), the PAALi solution concentration is 0.5 mol / L, the drying temperature is 80 degrees, and the drying time is 5 hours. Under this condition, the thickness of the organic coating layer is about 10 μm. Increasing the spin coating speed or reducing the PAALi solution concentration can slightly reduce the thickness of the coating layer, and vice versa.

[0075] Example 3

[0076] In combination Figure 3 As shown, the comparative example is a ready-made commercially available conventional lithium metal round sheet with a thickness of 500 μm and a diameter of 15 mm.

[0077] Example 4

[0078] In combination Figure 4 As shown, the comparison of the cycle performance of the three-dimensional porous lithium negative electrode without surface coating in Example 1, the three-dimensional porous lithium negative electrode with surface PAALi lithium-conducting artificial SEI organic layer coating in Example 2, and the untreated commercial lithium sheet in the comparative example in the lithium-lithium symmetric battery form.

[0079] The results show that the polarization voltage of Example 2 is significantly smaller, and the cycle life is significantly improved, showing good electrochemical performance.

[0080] The above describes the preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments. Within the technical concept of the present application, the technical solutions of the present application can be variously modified, and these simple modifications all belong to the protection scope of the present application.

[0081] In addition, it should be noted that each specific technical feature and step described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations.

[0082] In addition, various different embodiments of the present application can also be combined in any manner, as long as they do not deviate from the idea of the present application, and they should also be considered as disclosed by the present application.

Claims

1. A method for preparing a three-dimensional lithium anode, characterized in that, The preparation method includes: Provides a conductive material as a substrate; and A pulsed droplet jet deposition process is performed on the substrate surface to form a three-dimensional porous lithium metal and / or lithium alloy thin layer on the substrate surface, thereby forming the three-dimensional lithium anode; the thickness of the lithium metal and / or lithium alloy thin layer is <20μm. The pulsed droplet jet deposition method involves using a high-frequency pulse controller to spray molten lithium metal and / or lithium alloy through a porous nozzle array to form fine filaments and / or droplets, which then fall onto a substrate.

2. The method for preparing a three-dimensional lithium anode according to claim 1, characterized in that: The substrate is a metal foil.

3. The method for preparing a three-dimensional lithium anode according to claim 1, characterized in that: The lithium alloy includes at least one of lithium silicon, lithium tin, lithium aluminum, lithium indium, lithium magnesium, and lithium zinc alloy.

4. The method for preparing a three-dimensional lithium anode according to claim 1, characterized in that: The substrate is a copper foil current collector.

5. A three-dimensional lithium anode prepared by the preparation method according to any one of claims 1 to 4.

6. A lithium secondary battery, characterized in that: The lithium secondary battery comprises the three-dimensional lithium anode as described in claim 5.

7. A surface coating method for a three-dimensional lithium anode according to claim 5, characterized in that: The surface coating method includes coating the surface of a three-dimensional lithium anode with a PAALi solution by spraying, spin coating, or scraping, and then heating to remove the solvent to obtain a PAALi-coated three-dimensional lithium anode.

8. The surface coating method according to claim 7, characterized in that: The surface coating method also includes constructing an organic-inorganic composite artificial lithium-conducting SEI layer coating structure by combining a PAALi coating layer with a lithium-loving inorganic filler; The lithium-loving inorganic fillers include: Cu2S, Cu7S4, CuF2, Cu3P, SnS2, Cu3N, AlN, SnSe, Cu2Se, CuSe, CuSe2, SnF2, SbF3, LiF, MgF2 and Li3N.

9. A PAALi-coated three-dimensional lithium anode prepared by the surface coating method according to claim 7 or 8.

10. A lithium secondary battery, characterized in that: The lithium secondary battery comprises a three-dimensional lithium anode coated with PAALi as described in claim 9.

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