A coating, its preparation method, an electrochemical device, and an electronic device.

Abstract

This invention relates to a coating, its preparation method, an electrochemical device, and an electronic device. The coating comprises a carrier and gallium-containing liquid metal dispersed in the carrier. The coating has surface pores and internal pores communicating with the surface pores, forming a hierarchical pore structure. In this invention, after the coating is applied to a metal negative electrode, the unique hierarchical pore structure and cross-linking structure ensure that metal deposition occurs beneath the film. When upward-growing dendrites come into contact with the gallium-containing liquid metal inside the coating, they trigger a dendrite tip embrittlement reaction, providing chemical protection to the coating and thus improving the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a coating, its preparation method, an electrochemical device, and an electronic device. Background Technology

[0002] In recent years, with the rapid development of electric vehicles and mobile electronic devices, higher demands have been placed on the energy density of energy storage systems such as lithium-ion rechargeable batteries. Among these, lithium metal and sodium metal, with their ultra-high theoretical capacity (Li: 3860 mAh / g, Na: 1166 mAh / g) and suitable electrode potentials, have become research hotspots for metal rechargeable batteries. However, during the electrochemical precipitation process of metal ions reaching the metal anode surface through the SEI film (solid electrolyte interphase), uneven precipitation morphology forms on the anode surface. With cycling, this gradually forms dendrites, causing a decrease in coulombic efficiency and leading to safety issues such as battery short circuits, thus hindering the commercialization of metal rechargeable batteries.

[0003] To address the aforementioned technical challenges, researchers have attempted to control the interfacial behavior of metal anodes by coating their surfaces with protective coatings. However, these coatings only provide physical barriers; the highly active surface and unlimited volume expansion of the metal electrode itself make it virtually impossible to completely suppress dendrite deposition during long-term cycling. Gallium and gallium-based alloys, which are liquid at room temperature, exhibit weak interatomic bonding and flow properties, as well as self-healing capabilities, representing a new class of materials possessing both fluid and metallic characteristics. When in contact with ductile metals (Li, Na, K, Zn, Al, etc.), gallium atoms can diffuse along the metal grain boundaries, inducing embrittlement in the contact area. Based on this embrittlement phenomenon, it is hoped that gallium-containing metals can provide chemical barriers, thereby controlling the dendrite behavior at the metal anode interface.

[0004] For example, to address the dendrite problem in metal anodes, CN114649502A applies a gallium-based alloy layer with a thickness <500nm to the anode current collector. This coating influences the nucleation morphology of lithium metal on the current collector, making it more ordered and promoting denser, more uniform lithium metal growth at the anode. This reduces the contact area between the lithium metal anode and the electrolyte, thereby reducing the amount of irreversible side reactions at the interface, minimizing reversible lithium resource loss during each charge-discharge cycle, improving battery cycle stability, and increasing energy density. However, gallium-based alloys are prone to aggregation under stress during electrochemical processes, leading to coating failure and poor battery cycle stability. CN109390585B utilizes the strong adhesion between liquid gallium and organic viscoelastics to create a composite film, effectively solving the aggregation problem. However, the lithium metal battery assembled from the resulting electrode has a lower energy density, and the hindered diffusion kinetics result in a shorter cycle life. Summary of the Invention

[0005] One objective of this invention is to provide a coating to improve the cycle stability of an electrochemical device assembled from negative electrode sheets; a second objective is to provide a method for preparing the coating as described above; a third objective is to provide an electrochemical device; and a fourth objective is to provide an electronic device.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In some embodiments, the present invention provides a coating comprising a carrier and gallium-containing liquid metal dispersed in the carrier, wherein surface pores and internal pores communicating with the surface pores are distributed on the surface and inside of the coating, and the surface pores and internal pores form a hierarchical pore structure.

[0008] In some embodiments, the pore size of the surface holes is 5-1000 nm, preferably 10-100 nm, and more preferably 10-60 nm.

[0009] In some embodiments, the proportion of pores with a diameter ≤250nm in the surface holes is ≥50%, and preferably, the proportion of pores with a diameter ≤60nm is ≥90%.

[0010] In some embodiments, the carrier comprises polysiloxane, silicone resin, or a mixture thereof.

[0011] In some embodiments, the gallium-containing metal includes gallium or a gallium-based alloy.

[0012] In some embodiments, the gallium content in the gallium-based alloy is 60wt%-90wt%, preferably 65wt%-90wt%.

[0013] In some embodiments, the mass percentage of the carrier to the gallium-containing metal is 90wt%-20wt%:10wt%-80wt%, preferably 70wt%-30wt%:30wt%-70wt%.

[0014] In some embodiments, the present invention also provides a method for preparing the coating as described above, the method comprising the following steps:

[0015] S1. Add gallium-containing liquid metal to the carrier, mix evenly to obtain a mixture;

[0016] S2. The mixture is coated onto a metal substrate, dried, etched, cleaned, soaked, and dried again.

[0017] In some embodiments, the mixing time in step S1 is 0.5-2 hours.

[0018] In some embodiments, in step S2, the coating thickness is ≤50μm, preferably ≤10μm, and more preferably ≤5μm.

[0019] In some embodiments, during step S2, the concentration of the soaking solution used in the soaking process is 0.01-3 mol, preferably 0.1-3 mol / L.

[0020] In some embodiments, the present invention also provides an electrochemical device comprising an electrode, the electrode comprising a metal current collector and a coating as described above or a coating prepared according to the preparation method described above on the metal current collector.

[0021] In some embodiments, the present invention also provides an electronic device comprising the electrochemical device as described above.

[0022] The beneficial effects of this invention are:

[0023] In this invention, the surface pores are connected to the internal pores, forming a cross-linked structure. This restricts the flow and aggregation of liquid metal inside the coating, improving the stability of the coating and thus enhancing the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating. The surface pores promote electrolyte wetting and increase the ion diffusion rate without affecting the kinetic performance of the electrochemical device. After the coating is applied to the metal negative electrode, the unique hierarchical pore structure and cross-linked structure ensure that metal deposition occurs below the film. When the upward-growing dendrites come into contact with the gallium-containing liquid metal inside the coating, they trigger the embrittlement reaction at the dendrite tips, exerting the chemical protection effect of the coating and thus improving the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the coating preparation process in Example 1;

[0025] Figure 2 This is a schematic diagram of the structure of the coating obtained in Example 1;

[0026] Figure 3 The images show the surface nanopore morphology and pore size distribution of the coatings prepared in Example 1 and Comparative Example 7. a is a morphology image of the pores on the surface of the coating prepared in Example 1, b is a pore size distribution image of the surface of the coating prepared in Example 1, and c is a morphology image of the pores on the surface of the coating prepared in Comparative Example 7.

[0027] Figure 4 The internal cross-linking pore morphology of the coating in Example 1;

[0028] Figure 5 This is a schematic diagram of the assembly of a symmetrical battery.

[0029] Figure 6 This is an electron microscope scan of the surface of the coating prepared in Comparative Example 6;

[0030] Figure 7 To achieve a current density of 2 mA / cm² 2 Deposition amount 1mAh / cm 2 Under the electrochemical parameters, after 50 cycles, electron microscope scan images (4 μm) of the surface of the negative electrode sheet of Example 1 and Comparative Example 1 are obtained. Among them, a is the electron microscope scan image of the surface of the negative electrode sheet of Example 1, and b is the electron microscope scan image of the surface of the negative electrode sheet of Comparative Example 1.

[0031] Figure 8 To achieve a current density of 2 mA / cm² 2 Deposition amount 1mAh / cm 2 Under the electrochemical parameters, after 50 cycles, electron microscope scan images (10 μm) of the side of the negative electrode of Example 1 and Comparative Example 1 are obtained. Among them, a is the electron microscope scan image of the side of the negative electrode of Example 1, and b is the electron microscope scan image of the side of the negative electrode of Comparative Example 1.

[0032] Figure 9 The voltage curves are for the symmetrical cells of Example 1 and Comparative Example 1. Detailed Implementation

[0033] The present invention will be further illustrated below through specific examples, but it should be noted that the embodiments of the present invention are...

[0034] The specific material ratios, process conditions, and results described herein are for illustrative purposes only and should not be construed as limiting the scope of protection of this invention. All equivalent changes or modifications made in accordance with the spirit and essence of this invention should be included within the scope of protection of this invention. It should be noted that, unless otherwise specified, "wt%" as used herein refers to "mass fraction".

[0035] In some embodiments, the present invention provides a coating comprising a carrier and gallium-containing liquid metal dispersed in the carrier, wherein surface pores and internal pores communicating with the surface pores are distributed on the surface and inside of the coating, and the surface pores and internal pores form a hierarchical pore structure.

[0036] In this invention, the surface pores are connected to the internal pores, forming a cross-linked structure. This restricts the flow and aggregation of liquid metal inside the coating, improving the stability of the coating and thus enhancing the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating. The surface pores promote electrolyte wetting and increase the ion diffusion rate without affecting the kinetic performance of the electrochemical device. After the coating is applied to the metal negative electrode, the unique hierarchical pore structure and cross-linked structure ensure that metal deposition occurs below the film. When the upward-growing dendrites come into contact with the gallium-containing liquid metal inside the coating, they trigger the embrittlement reaction at the dendrite tips, exerting the chemical protection effect of the coating and thus improving the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating.

[0037] In some embodiments, the pore size of the surface holes is 5-1000 nm;

[0038] In this invention, the surface pores with a diameter of 5-1000 nm can promote electrolyte wetting and increase the ion diffusion rate without affecting the kinetic performance of the electrochemical device assembled from the negative electrode formed by the coating. At the same time, the nanoscale size can further prevent gallium-containing metal from flowing out, thereby improving the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating.

[0039] In this invention, if the pore size of the surface pores is <5nm, it will severely hinder ion transport and affect the electrochemical performance of the electrochemical device assembled from the negative electrode formed by the coating; if the pore size of the surface pores is >1000nm, the gallium-containing metal inside the coating is easily exposed and falls off, reducing the chemical barrier effect of the coating on dendrites, and thus reducing the cycle stability of the electrochemical device assembled from the negative electrode formed by the coating.

[0040] It should be understood that, in this invention, surface holes and internal holes refer to holes distributed on the surface of the coating and inside the coating, respectively.

[0041] In some embodiments, the proportion of pores with a diameter ≤250nm in the surface pores is ≥50%.

[0042] It should be noted that the percentage of pores with a diameter ≤250nm refers to the percentage of the number of pores with a diameter ≤250nm to the total number of surface pores.

[0043] In some embodiments, the mass percentage of the carrier to the gallium-containing metal is 90wt%-20wt%:10wt%-80wt%, the carrier includes polysiloxane, silicone resin, or a mixture thereof, and the gallium-containing liquid metal includes gallium or a gallium-based alloy, the gallium-based alloy including at least one of gallium-indium alloy, gallium-tin alloy, and gallium-indium-tin alloy, wherein the gallium content in the gallium-based alloy is 60wt%-90wt%.

[0044] In this invention, the gallium content in the gallium-based alloy is 60wt%-90wt%, which ensures the fluidity of the gallium-based alloy and thus ensures that the coating can chemically block the dendrites that appear, thereby ensuring the cycle stability of the electrochemical device assembled from the negative electrode sheet formed by the coating.

[0045] In this invention, gallium-containing liquid metal refers to a metallic substance containing gallium and which is liquid at room temperature.

[0046] In some embodiments, the present invention also provides a method for preparing the coating as described above, the method comprising the following steps:

[0047] S1. Add gallium-containing liquid metal to the carrier and mix thoroughly to obtain a mixture;

[0048] S2. Apply the mixture to a metal substrate, dry it, then etch, clean, soak, and dry it again.

[0049] like Figure 1 As shown, during the stirring process, a large number of bubbles can be introduced into the system formed by the carrier 12 (i.e., the carrier compound) and the gallium-containing liquid metal 11 to form a mixture 13 (i.e., a liquid mixture), which facilitates the formation of a cross-linked porous structure after the mixture is cured at high temperature. Subsequently, the mixture 13 is coated on the metal substrate to form a film, and after drying, a composite coating 14 with a dense surface and porous interior can be obtained. By performing a displacement treatment on the bottom metal substrate and immersing and etching the coating, a large number of nanopores (i.e., surface pores) can be generated on the surface, and a large number of pores communicating with the surface pores (i.e., internal pores) can be generated inside, forming a self-supporting, ultra-thin coating 15 (i.e., a porous coating) with a hierarchical pore structure.

[0050] The structure of the resulting coating is as follows Figure 2 As shown, the mixture has a high viscosity, and a large number of air bubbles are introduced during the long mixing process, resulting in a cross-linked porous structure inside the cured coating. After immersion etching, a large number of nanopores are formed on the surface of the coating, and a large number of internal pores are formed inside the coating that communicate with the surface pores. The surface pores and internal pores form a hierarchical pore structure, providing a large number of channels for ion transport, which allows metal deposition to occur below the coating. The physical confinement of the coating itself can provide a partial buffer to suppress dendrite growth. When dendrite formation is severe, the upward-growing dendrites will penetrate into the coating and come into contact with the gallium-containing liquid metal inside, inducing an embrittlement reaction with the dendrite tips, relieving the stress of upward growth, and achieving ultra-long stable cycling of the electrochemical device formed by the coating.

[0051] In some embodiments, the metal substrate includes at least one of copper foil, aluminum foil, zinc foil, and tin foil.

[0052] In some embodiments, in step S2, the coating thickness is ≤50μm.

[0053] In this invention, the coating thickness is ≤50μm, which can avoid the adverse effect of excessive thickness on the energy density of the electrochemical device assembled from the negative electrode sheet formed by the coating.

[0054] In some embodiments, the mixing time is 0.5-2 hours.

[0055] In this invention, by controlling the mixing time of the carrier and gallium-containing metal to 0.5-2 h, the cycle stability of the electrochemical device formed by the coating can be further improved.

[0056] In some embodiments, during step S2, the etching solution used in the etching process includes at least one of ferric chloride solution, mercuric nitrate solution, silver nitrate solution, platinum sulfate solution, and mixed acid. The mixed acid includes hydrogen peroxide and solution A, and solution A includes at least one of hydrochloric acid, sulfuric acid, hydrofluoric acid, and nitric acid.

[0057] It should be noted that the volume content of hydrogen peroxide in the mixed acid is 60-90%.

[0058] In some embodiments, in step S2, the concentration of the etching solution used during the etching process is 0.1-4 mol / L.

[0059] In some embodiments, the etching time in step S2 is 0.1-5 hours.

[0060] It should be noted that, in this invention, the soaking solution used in the soaking process includes inorganic acid or inorganic base. Inorganic acid can be, for example, at least one of hydrochloric acid, sulfuric acid, and hydrofluoric acid, and inorganic base can be, for example, at least one of sodium hydroxide and potassium hydroxide. The concentration of the soaking solution is 0.01-3 mol / L, and the soaking time is 0.1-1.5 h.

[0061] In this invention, the selection of the type of immersion solution, the concentration range, and the etching time play a decisive role in the pore size, number, and distribution of the surface pores of the coating, as well as the number of cross-linked pore channels, thereby ensuring the ion transport of the coating.

[0062] It should be noted that in this invention, the drying temperature is 60-200℃, preferably 80-200℃; the drying time is 0.5-48h, preferably 0.5-20h.

[0063] It should be noted that in this invention, the drying temperature is 60-200℃, preferably 80-200℃; the drying time is 0.5-48h, preferably 0.5-20h.

[0064] In some embodiments, the present invention also provides an electrochemical device comprising an electrode comprising a metal current collector and a coating as described above or a coating prepared according to the preparation method described above on the metal current collector.

[0065] In some embodiments, the negative electrode includes at least one of lithium, sodium, potassium, zinc, and aluminum.

[0066] It should be noted that, in this invention, the electrode assembly of the electrochemical device includes a positive electrode, a negative electrode, and a diaphragm (if necessary) disposed between the positive electrode and the negative electrode. The electrochemical device is obtained by arranging the positive electrode and the negative electrode relative to each other through the diaphragm (if necessary) and adding an electrolyte.

[0067] Regarding the positive electrode, the positive electrode may include a positive current collector and a layer of positive active material located on the positive current collector.

[0068] As for the positive electrode current collector, it can be made of aluminum, copper, nickel, titanium, etc., in the form of foil, open-cell foil, or strip material formed by mesh. It can also be a porous material, such as porous metal (e.g., foamed metal).

[0069] Regarding the positive electrode active material layer, it may be coated only on a portion of the positive electrode current collector. The positive electrode active material layer may include the positive electrode active material, a conductive agent, and a binder.

[0070] Regarding conductive agents, the conductive agents for the positive electrode sheet can include at least one of conductive carbon black, sheet graphite, graphene, and carbon nanotubes.

[0071] Regarding binders, the binders in the positive electrode sheet can include at least one of the following: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, a copolymer of styrene and acrylate, a copolymer of styrene and butadiene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0072] Regarding positive electrode active materials, examples include at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium iron phosphate, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese oxide. These positive electrode active materials can be positive electrode active materials that have undergone doping or coating treatment.

[0073] Regarding the diaphragm, examples include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, and aramid.

[0074] In some embodiments, a porous layer may also be provided on the surface of the diaphragm, the porous layer being disposed on at least one surface of the substrate of the diaphragm, and the porous layer may include inorganic particles and a binder.

[0075] Regarding inorganic particles, examples of inorganic particles in porous layers include at least one of the following: aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0076] Regarding the binder, the binder in the porous layer can be listed as at least one of the following: polyvinylidene fluoride, copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0077] It should be understood that, in this invention, the diaphragm is not a necessary component of the electrochemical device. For example, in certain types of electrochemical devices (such as structures where the positive and negative electrodes do not directly contact each other), a diaphragm may not be necessary.

[0078] In some embodiments, the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly.

[0079] In some embodiments, the electrochemical device may further include an electrolyte. The electrolyte may be at least one of a gel electrolyte, a solid electrolyte, or an electrolyte solution.

[0080] Taking lithium-ion secondary batteries as an example, the electrolyte includes lithium salts and solvents. Examples of lithium salts include at least one from the following: LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0081] Regarding solvents, examples include at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0082] In the case of carbonate compounds, examples include at least one of chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, and other organic solvents.

[0083] Regarding chain carbonate compounds, examples include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC). Cyclic carbonate compounds include at least one of ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), and vinyl ethylene carbonate (VEC).

[0084] In the case of fluorocarbonate compounds, examples include at least one of the following: fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0085] As far as carboxylic acid ester compounds are concerned, carboxylic acid ester compounds may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonic acid lactone, caprolactone, and methyl formate.

[0086] In terms of ether compounds, examples include at least one of dibutyl ether, tetraethylene dimethyl ether, diethylene dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.

[0087] Other organic solvents include, for example, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0088] In some embodiments, taking a lithium-ion secondary battery as an example, the electrochemical device can be prepared by sequentially winding or stacking a positive electrode, a separator, and a negative electrode into an electrode assembly, then encapsulating it in an aluminum-plastic film, adding an electrolyte, forming, and encapsulating, thus assembling a lithium-ion secondary battery.

[0089] It should be noted that the electrochemical device in this invention is not particularly limited and can be made into paper-type batteries, button-type batteries, coin-type batteries, stacked batteries, cylindrical batteries, square batteries, etc.

[0090] It should be noted that, in this invention, the electrochemical device can also be a symmetrical battery.

[0091] In some embodiments, the present invention also provides an electronic device comprising the electrochemical device as described above.

[0092] It should be noted that the electronic device in this invention is not particularly limited and can be any electronic device known in the prior art.

[0093] In some embodiments, electronic devices may include, for example, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, capacitors, and other materials.

[0094] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0095] It should be understood that the following embodiments only list specific scenarios where lithium or sodium is used as the negative electrode current collector, copper foil is used as the metal substrate, ferric chloride solution, mercuric nitrate solution, silver nitrate solution, and platinum sulfate solution are used as etching solutions, gallium, gallium indium alloy, and gallium indium tin alloy are used as gallium-containing metals, and hydrochloric acid, hydrofluoric acid, and potassium hydroxide are used as immersion solutions. Those skilled in the art can also choose other negative electrode current collectors besides lithium and sodium, such as potassium, zinc, and aluminum; other metal substrates besides copper foil, such as aluminum foil, zinc foil, and tin foil; other etching solutions besides ferric chloride solution, mercuric nitrate solution, silver nitrate solution, and platinum sulfate solution, such as mixed acids; other gallium-containing metals besides gallium, gallium indium alloy, and gallium indium tin alloy, such as gallium tin alloy; and other immersion solutions besides hydrochloric acid, hydrofluoric acid, and potassium hydroxide, such as sulfuric acid and sodium hydroxide.

[0096] Example 1

[0097] (1) Weigh 8g of liquid gallium indium alloy with a gallium content of 68wt% and add 2g of polydimethylsiloxane (CAS No. 9016-00-6) into a mortar and grind and mix mechanically for 1h to obtain a uniform gray mixture;

[0098] (2) The uniform gray mixture was scraped onto the copper foil until the coating thickness was measured to be 5 μm by an automatic coating machine. Then it was dried at 100°C for 12 h to obtain a gallium-containing metal composite coating with a smooth and dense surface.

[0099] (3) The copper foil treated in step (2) is immersed in a 3 mol / L FeCl3 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0100] (4) After cleaning, the self-supporting coating is transferred to a hydrofluoric acid solution (the volume ratio of hydrogen fluoride to water is 5:100) and completely immersed for 15 minutes to form a large number of nanopores on the surface of the coating. After cleaning, it is dried at 100°C for 12 hours to obtain a coating with a thickness of 5 μm.

[0101] The coating was scanned using an electron microscope, and the results are as follows: Figure 3 As shown in figure a, the pore size distribution of the pores on the coating surface was statistically analyzed, and the results are as follows. Figure 3 As shown in b.

[0102] Depend on Figure 3 As can be seen from this embodiment, the surface of the coating has a number of pores (i.e., surface pores), and the pore size of the surface pores is at the nanometer level.

[0103] Depend on Figure 3 As shown in b, the pore size of the surface pores is mainly distributed in the range of 10-60 nm, and the proportion of pores with a diameter ≤30 nm is 92%.

[0104] A cross-sectional sample was prepared using focused ion beam (FIB) and the internal morphology of the coating was examined. The results are as follows: Figure 4 As shown.

[0105] Depend on Figure 4 It can be seen that the internal pores (i.e., internal pores) of the coating obtained in this embodiment are connected to the surface pores (i.e., surface pores), that is, the surface pores and internal pores form a cross-linked structure, and the pore diameters of the surface pores and internal pores are significantly different, that is, the surface pores and internal pores form a hierarchical pore structure.

[0106] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0107] (6) Figure 5 As shown, a negative electrode shell 51, modified lithium metal 52, separator 53, modified lithium metal 52 and positive electrode shell 54 are placed in sequence to assemble a symmetrical battery.

[0108] Example 2

[0109] (1) Weigh 5g of liquid gallium and 5g of polysiloxane (model I11413) and add them to a centrifuge tube. Add ball milling beads and ball mill the mixture for 1.5h to obtain a uniform gray mixture.

[0110] (2) A uniform gray mixture is scraped onto a copper foil until the coating thickness is measured to be 5 μm by an automatic coating machine. Then it is dried at 100°C for 12 h to obtain a gallium-containing metal composite coating with a smooth and dense surface.

[0111] (3) The copper foil treated in step (2) is immersed in 2 mol / L AgNO3 solution for 20 min to undergo a displacement reaction, etching the copper foil and leaving a self-supporting coating.

[0112] (4) After cleaning, the self-supporting coating was transferred to a hydrochloric acid solution (the volume ratio of hydrogen chloride to water was 20:100) and completely immersed for 30 minutes to form a large number of nanopores on the surface of the coating. After cleaning, it was dried at 100°C for 12 hours to obtain a coating with a thickness of 5 μm.

[0113] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0114] (6) Figure 5 As shown, a negative electrode shell 51, modified lithium metal 52, separator 53, modified lithium metal 52 and positive electrode shell 54 are placed in sequence to assemble a symmetrical battery.

[0115] Example 3

[0116] (1) Weigh 2g of liquid gallium indium tin alloy with a gallium content of 68wt% and add 8g of methyl silicone resin (model S26897) into a mortar and mechanically grind and mix for 0.5h to obtain a uniform gray mixture;

[0117] (2) The uniform gray mixture was scraped onto the copper foil until the coating thickness was measured to be 5 μm by an automatic coating machine. Then it was dried at 100°C for 12 h to obtain a gallium-containing metal composite coating with a smooth and dense surface.

[0118] (3) The copper foil treated in step (2) is immersed in a 1 mol / L PtSO4 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0119] (4) After cleaning, the self-supporting coating was transferred to a potassium hydroxide solution (the volume ratio of potassium hydroxide to water was 1:100) and completely immersed for 60 min to form a large number of nanopores on the surface of the coating. After cleaning, it was dried at 100℃ for 12 h to obtain a coating with a thickness of 5 μm.

[0120] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0121] (6) Figure 5 As shown, a negative electrode shell 51, modified lithium metal 52, separator 53, modified lithium metal 52 and positive electrode shell 54 are placed in sequence to assemble a symmetrical battery.

[0122] Example 4

[0123] The difference between this embodiment and Embodiment 1 is that:

[0124] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter sodium disc to form modified sodium metal.

[0125] (6) Place the negative electrode shell, modified sodium metal, separator, modified sodium metal and positive electrode shell in sequence to assemble a symmetrical battery.

[0126] Example 5

[0127] The difference between this embodiment and Embodiment 2 is that:

[0128] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter sodium disc to form modified sodium metal.

[0129] (6) Place the negative electrode shell, modified sodium metal, separator, modified sodium metal and positive electrode shell in sequence to assemble a symmetrical battery.

[0130] Example 6

[0131] The difference between this embodiment and Embodiment 3 is that:

[0132] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter sodium disc to form modified sodium metal.

[0133] (6) Place the negative electrode shell, modified sodium metal, separator, modified sodium metal and positive electrode shell in sequence to assemble a symmetrical battery.

[0134] Example 7

[0135] The difference between this embodiment and Embodiment 1 is that:

[0136] (2) The uniform gray mixture was scraped onto the copper foil until the coating thickness was 2 μm when tested by an automatic coating machine. Then it was dried at 100°C for 12 h to obtain a gallium-containing metal composite coating with a smooth and dense surface.

[0137] (3) The copper foil treated in step (2) is immersed in a 3 mol / L FeCl3 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0138] (4) After cleaning, the self-supporting coating was transferred to a hydrofluoric acid solution (the volume ratio of hydrogen fluoride to water was 5:100) and completely immersed for 15 minutes to form a large number of nanopores on the surface of the coating. After cleaning, it was dried at 100°C for 12 hours to obtain a coating with a thickness of 2 μm.

[0139] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0140] (6) Figure 5 As shown, a negative electrode shell 51, modified lithium metal 52, separator 53, modified lithium metal 52 and positive electrode shell 54 are placed in sequence to assemble a symmetrical battery.

[0141] Example 8

[0142] The difference between this comparative example and Example 1 is that:

[0143] Weigh 8g of liquid gallium and 2g of polydimethylsiloxane (CAS No. 9016-00-6) and add them to a mortar. Mechanically grind and mix for 1 hour to obtain a uniform gray mixture.

[0144] Example 9

[0145] The difference between this comparative example and Example 3 is that:

[0146] (1) Weigh 8g of liquid gallium indium tin alloy with a gallium content of 68wt% and add 2g of methyl silicone resin (model S26897) into a mortar and mechanically grind and mix for 0.5h to obtain a uniform gray mixture;

[0147] (3) The coating treated in step (2) is immersed in 0.1 mol / L PtSO4 solution for 5 h to undergo a displacement reaction, etch the copper foil, and leave a self-supporting coating.

[0148] (4) After cleaning, the self-supporting coating was transferred to a 0.01 mol / L potassium hydroxide solution and completely immersed for 1.5 h to form a large number of nanopores on the surface of the coating. After cleaning, it was dried at 100 °C for 12 h to obtain a coating with a thickness of 5 μm.

[0149] Comparative Example 1

[0150] The difference between this comparative example and Example 1 is that:

[0151] The negative electrode shell, lithium metal, separator, lithium metal and positive electrode shell are placed in sequence to assemble a symmetrical battery.

[0152] Comparative Example 2

[0153] The difference between this comparative example and Example 4 is that:

[0154] The negative electrode shell, sodium metal, separator, sodium metal, and positive electrode shell are placed in sequence to assemble a symmetrical battery.

[0155] Comparative Example 3

[0156] (1) Weigh 8g of liquid gallium indium alloy with a gallium content of 68wt% and add 2g of polydimethylsiloxane (CAS No. 9016-00-6) into a mortar and grind and mix mechanically for 10min to obtain a mixture;

[0157] (2) The mixture is scraped onto copper foil until the coating thickness is 5 μm when tested by an automatic coating machine. Then it is dried at 100°C for 12 h to obtain a smooth and dense gallium-containing metal composite coating.

[0158] (3) The copper foil treated in step (2) is immersed in a 3 mol / L FeCl3 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0159] (4) After cleaning, the self-supporting coating is dried at 100°C for 12 hours to obtain a coating with a thickness of 5μm.

[0160] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0161] (6) Place the negative electrode shell, modified lithium metal, separator, modified lithium metal and positive electrode shell in sequence to assemble a symmetrical battery.

[0162] Comparative Example 4

[0163] (1) Weigh 8g of liquid gallium indium alloy with a gallium content of 68wt% and add 2g of polydimethylsiloxane (CAS No. 9016-00-6) into a mortar and grind and mix mechanically for 10min to obtain a mixture;

[0164] (2) The mixture is scraped onto copper foil until the coating thickness is 5 μm when tested by an automatic coating machine. Then it is dried at 100°C for 12 h to obtain a smooth and dense gallium-containing metal composite coating.

[0165] (3) The copper foil treated in step (2) is immersed in a 3 mol / L FeCl3 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0166] (4) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter sodium disc to form modified sodium metal.

[0167] (5) Place the negative electrode shell, modified lithium metal, separator, modified lithium metal and positive electrode shell in sequence to assemble a symmetrical battery.

[0168] Comparative Example 5

[0169] The difference between this comparative example and Example 1 is as follows:

[0170] (1) Weigh 8g of liquid gallium indium alloy with a gallium content of 30wt% and add 2g of polydimethylsiloxane (CAS No. 9016-00-6) into a mortar and grind and mix mechanically for 1h to obtain a uniform gray mixture.

[0171] Comparative Example 6

[0172] The difference between this comparative example and Example 1 is as follows:

[0173] (1) Weigh 8g of liquid gallium-indium alloy with a gallium content of 68wt% and 2g of polyvinylidene fluoride (CAS No. 24937-79-9) and N-methylpyrrolidone to form a mixed adhesive solution (the polyvinylidene fluoride content in the mixed adhesive solution is 10wt%) and add it to a mortar. Mechanically grind and mix for 1h to obtain a mixture.

[0174] (2) The mixture is scraped onto copper foil until the coating thickness is 5 μm when tested by an automatic coating machine. Then it is dried at 100°C for 12 h to obtain a smooth and dense gallium-containing metal composite coating.

[0175] like Figure 6 As shown, after the mixed adhesive cures, it is difficult to completely encapsulate the gallium-containing metal. The exposed gallium-containing metal droplets can cause contact between the positive and negative electrode plates, resulting in a short circuit in the battery.

[0176] Comparative Example 7

[0177] The difference between this comparative example and Example 1 is as follows:

[0178] After cleaning the coating treated in step (3), it is transferred to a 4 mol / L hydrofluoric acid solution and completely immersed for 2 hours to prepare an over-etched coating.

[0179] The coating prepared in this comparative example was scanned using an electron microscope, and the results are as follows: Figure 3 As shown in c.

[0180] Depend on Figure 3 As can be seen from c, the pore size of the surface of the coating obtained in this comparative example is in the micrometer range.

[0181] Comparative Example 8

[0182] The difference between this comparative example and Example 1 is as follows:

[0183] (2) The uniform gray mixture is scraped onto the copper foil until the coating thickness is 100 μm when tested by an automatic coating machine. Then it is dried at 100°C for 12 h to obtain a gallium-containing metal composite coating with a smooth and dense surface.

[0184] (3) The copper foil treated in step (2) is immersed in a 3 mol / L FeCl3 solution for 20 min to undergo a displacement reaction, which etches the copper foil and leaves a self-supporting coating.

[0185] (4) After cleaning, the self-supporting coating is transferred to a hydrofluoric acid solution (the volume ratio of hydrogen fluoride to water is 5:100) and completely immersed for 15 minutes to form a large number of nanopores on the surface of the coating. After cleaning, it is dried at 100°C for 12 hours to obtain a coating with a thickness of 5 μm.

[0186] (5) The coating is cut into 14cm diameter discs using a slicer and transferred onto a 12cm diameter lithium sheet to form modified lithium metal.

[0187] (6) Figure 5 As shown, a negative electrode shell 51, modified lithium metal 52, separator 53, modified lithium metal 52 and positive electrode shell 44 are placed in sequence to assemble a symmetrical battery.

[0188] Performance testing

[0189] After standing for 24 hours, at a current density of 2 mA / cm² 2 Deposition amount 1mAh / cm 2 Under the specified electrochemical parameters, the battery underwent 50 cycles. After the cycles, the battery was disassembled in a glove box, and the electrodes were cleaned three times with dimethyl carbonate before electron microscopy scanning. The electron microscopy results of Example 1 and Comparative Example 1 are as follows: Figure 7 and Figure 8 As shown; simultaneously, under these electrochemical parameters, the cycle life of the symmetrical cells assembled in Examples 1-9 and Comparative Examples 1-8 was tested, and the results are shown in Table 1; when the metal electrode interface is uniformly deposited, the voltage curve of the symmetrical cell in the cycle life test is as follows. Figure 9 As shown.

[0190] Table 1 Test Results

[0191]

[0192]

[0193] As shown in Table 1, compared with Comparative Example 1 (without coating modification), the battery assembled from the negative electrode sheet formed by the coating of Example 1 (with coating modification) exhibits a significantly improved cycle life. This result demonstrates that the coating of the present invention can significantly improve the cycle stability of electrochemical devices assembled from the formed negative electrode sheet.

[0194] As shown in Table 1, compared with Comparative Example 3 (without etching), the battery assembled with the negative electrode sheet formed by the coating of Example 1 (with etching) exhibits a significantly improved cycle life. This result demonstrates that etching treatment can significantly improve the cycle stability of the electrochemical device assembled with the negative electrode sheet formed by the coating of the present invention.

[0195] As shown in Table 1, compared with Comparative Example 5 (where the gallium content in the liquid gallium-indium alloy is 30 wt%), the battery assembled from the negative electrode sheet formed by the coating in Example 1 (where the gallium content in the liquid gallium-indium alloy is in the range of 60 wt%-90 wt%) exhibits a significantly improved cycle life. This result indicates that controlling the gallium content within a specific range (60 wt%-90 wt%) in gallium-based alloys can further improve the cycle stability of electrochemical devices assembled from the negative electrode sheet formed by the coating.

[0196] As shown in Table 1, compared with Comparative Example 6 (a mixed solution formed by polyvinylidene fluoride (PVDF) and N-methylpyrrolidone at a mass ratio of 10:90), the battery assembled with the negative electrode sheet formed by the coating of Example 1 (polydimethylsiloxane as the carrier) exhibits a significantly improved cycle life. This result demonstrates that by selecting specific carrier types (polysiloxane, silicone resin, or a mixture of both), the present invention can further improve the cycle stability of electrochemical devices assembled with negative electrode sheets formed by coating.

[0197] As shown in Table 1, compared with Comparative Example 7 (immersion solution concentration of 4 mol / L), the battery assembled from the negative electrode sheet formed by the coating in Example 1 (immersion solution concentration in the range of 0.01-3 mol / L) exhibits a significantly improved cycle life. This result demonstrates that by selecting a specific concentration of immersion solution (0.01-3 mol / L), the present invention can further improve the cycle stability of the electrochemical device assembled from the formed negative electrode sheet.

[0198] As shown in Table 1, compared with Comparative Example 8 (coating thickness > 50 μm), the battery assembled from the negative electrode sheet formed by the coating in Example 1 (coating thickness < 10 μm) exhibits a significantly improved cycle life. This result demonstrates that by setting the coating thickness within a specific range, the present invention can further improve the cycle stability of the electrochemical device assembled from the formed negative electrode sheet.

[0199] Depend on Figure 9As can be seen from a, Example 1 exhibits a stable voltage curve, and the overpotential is below 50mV; Figure 9 As shown in b, when a large number of dendritic deposits are generated on the metal surface, the SEI film at the interface undergoes repeated rupture and reconstruction, leading to a continuous increase in the interfacial overpotential and ultimately, drastic fluctuations in the voltage curve. This result indicates that the coating of the present invention can significantly improve the cycle stability of the electrochemical device assembled from the formed negative electrode, reduce the interfacial impedance of the negative electrode, and thus reduce the overpotential of the electrochemical device assembled from the coated negative electrode.

[0200] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A coating for a metal negative electrode, characterized by, The metal negative electrode coating is located on the surface of a metal negative electrode, and comprises a carrier and a gallium-containing liquid metal dispersed in the carrier, the surface and interior of the metal negative electrode coating are respectively distributed with surface pores and internal pores communicating with the surface pores, and the surface pores and internal pores form a hierarchical pore structure. The carrier comprises polysiloxane, silicone resin, or a mixture of both. The gallium-containing liquid metal comprises gallium or a gallium-based alloy, and the content of gallium in the gallium-based alloy is 60wt%-90wt%. The pore diameter of the surface pores is 5-1000nm, and the proportion of pores with a pore diameter of ≤250nm in the surface pores is ≥50%.

2. The method for producing the coating for a metal negative electrode according to claim 1, characterized by, The preparation method comprises the following steps: S1. Adding a gallium-containing liquid metal to a carrier, mixing uniformly to obtain a mixture; S2. Coating the mixture on a metal substrate, drying, etching, cleaning, soaking, and drying.

3. The production method according to claim 2, wherein In step S1, the mixing time is 0.5-2h.

4. The production method according to claim 2, wherein In step S2, the coating thickness is ≤50μm.

5. The production method according to claim 2, wherein In step S2, the concentration of the soaking solution used in the soaking process is 0.01-3mol / L.

6. An electrochemical device, characterized by, The electrochemical device comprises an electrode sheet, and the electrode sheet comprises a metal negative electrode and a metal negative electrode coating as claimed in claim 1 or prepared by the preparation method of any one of claims 2-5 on the metal negative electrode.

7. An electronic device, comprising: The electronic device comprises the electrochemical device as claimed in claim 6.

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