Solid-state composite alkali metal negative electrode, preparation method thereof and secondary battery

Abstract

The invention provides a solid-state composite alkali metal negative electrode, a preparation method thereof and a secondary battery. The solid-state composite alkali metal negative electrode comprises an alkali-metallized three-dimensional support conductive skeleton, and the alkali-metallized three-dimensional support conductive skeleton is coated with a solid-state polymer electrolyte. The three-dimensional support conductive skeleton is subjected to alkali metallization, so that the initial capacity loss can be directly compensated, the initial coulombic efficiency of the solid-state composite alkali metal electrode is improved, and the reversible capacity of the battery is improved; moreover, the solid polymer electrolyte is coated on the three-dimensional support conductive framework, so that alkali metal can be isolated from water in air to react, the safety performance is improved, side reaction of an electrode / electrolyte interface is effectively inhibited, and the adaptability to volume change caused by stripping or deposition of the alkali metal is improved; therefore, the dendritic crystal growth resistance is improved. The secondary battery prepared based on the solid-state composite alkali metal negative electrode has excellent cycle performance and safety performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a solid composite alkali metal negative electrode, a preparation method thereof, and a secondary battery. Background Art

[0002] With the rapid development of science and technology and the continuous growth of energy demand, batteries play a crucial role in the global economic and technological progress. Since the commercialization of lithium-ion batteries in the 1990s, due to their characteristics such as high energy density, long cycle life, and low self-discharge rate, they have been widely used in fields such as portable electronic devices, electric vehicles, and energy storage systems. Under the current development trend dominated by clean energy and low-carbon economy, our demand for high-energy-density and low-cost batteries has further surged. However, the theoretical specific capacity of the most widely used graphite negative electrode in common lithium-ion batteries is only 372 mAh·g -1 , which limits its further application. In order to achieve secondary batteries with higher energy density, alkali metal negative electrodes such as metallic lithium / sodium are considered to be excellent choices for the next generation of high-energy-density secondary batteries because of their high theoretical specific capacity and low redox potential. However, choosing alkali metals as negative electrodes also faces some challenges: (1) Different from the intercalation mechanism of lithium-ion batteries, the uneven deposition / stripping of metallic lithium / sodium electrodes during cycling will lead to an obvious dendrite growth trend. When the dendrites grow to a certain extent, they will pierce the separator, causing the battery to short-circuit and rapidly generate a large amount of heat, further increasing the risk of fire or explosion. (2) Metallic lithium / metallic sodium has extremely high reactivity and will spontaneously react with one or several of the electrolyte components, including salts, solvents, and additives, to form a non-uniform SEI (solid electrolyte interface layer) on the metal surface. The volume change during the deposition / stripping process of the metal will cause the rupture of the SEI, which will further lead to the re-contact and reaction of the active lithium / sodium with the electrolyte, resulting in their rapid consumption.

[0003] Due to the existence of the above problems, conventional metallic lithium / sodium directly used as the negative electrode cannot provide long-term stable cycling for lithium / sodium metal batteries. Therefore, researchers have proposed various solutions. For example, Patent CN108321432A discloses a quasi-solid electrolyte prepared by using a lightweight carbonitride polymer as an electrolyte filler, which can effectively inhibit the growth of lithium dendrites in lithium metal batteries. The hierarchical structure of the lightweight carbonitride polymer is beneficial to the absorption of the electrolyte, thus forming a muddy quasi-solid electrolyte for inhibiting the growth of lithium negative electrode dendrites in lithium metal batteries. Patent CN113745759A discloses a coated separator, a preparation method and a method for inhibiting lithium dendrites. During the cycling process, the piezoelectric polymer coating of the coated separator contacts the negative electrode. When a trace amount of lithium dendrites are formed, it will squeeze the piezoelectric polymer coating of the coated separator, forming a piezoelectric potential, thereby inhibiting the continuous deposition of lithium elements at this point and achieving the purpose of inhibiting the growth of lithium dendrites. However, these methods do not fundamentally solve the problem of the appearance of dendrites in lithium / sodium metal batteries with lithium / sodium metal as the negative electrode.

[0004] In addition, Patent CN116230871A discloses a three-dimensional metal lithium composite anode with an in-situ protective layer, its preparation method, and a metal lithium battery. This patent uses a reaction medium fluid composed of non-metallic elements to undergo an interfacial reaction with metallic lithium under high-temperature conditions, forming a lithium-non-metallic element compound protective layer (such as lithium nitride) on the surface of the lithium metal. This protective layer is an inorganic compound and may have the risk of cracking during long-term cycling, affecting its protective effect and the cycle stability of the battery. CN109786669A discloses a lithium-sulfur battery and its preparation method. The lithium-sulfur battery includes: a 3D lithium metal anode, a sulfide cathode, and an electrolyte membrane. The electrolyte membrane is disposed between the 3D lithium metal anode and the sulfide cathode. The core of the lithiophilic modification of the three-dimensional conductive framework pointed out in this patent lies in the additional formation of a lithiophilic metal layer (such as germanium (Ge), aluminum (Al), nickel (Ni), magnesium (Mg), silver (Ag), or metal oxides, etc.) between the conductive framework and metallic lithium. This patent not only has cumbersome equipment requirements and high costs but also has poor thermal stability and electrochemical stability of the battery. Patent CN114899351A discloses a composite lithium metal anode, a solid-state battery, and its preparation method. In this patent, the composite lithium metal anode includes a lithium layer, a metal-carbon composite layer, and a polymer inorganic compound protective layer arranged in sequence. This composite method may cause damage to the polymer framework during long-term cycling, with the risk of cracking, affecting its protective effect and the cycle stability of the battery, and affecting the overall performance of the battery. Patent CN111063863A discloses a metal lithium composite anode material, its preparation method, and application. The metal lithium composite anode material is composed of a substrate containing metallic lithium and a polymer electrolyte protective film coated thereon. The method provided by this patent is complex and cumbersome, and the safety and stability of this metal lithium composite anode material are poor.

[0005] Therefore, how to solve the safety problems caused by poor cycle performance, volume expansion, and dendrite growth when using metallic lithium / sodium as the anode is the focus of current research. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a solid-state composite alkali metal anode, its preparation method, and a secondary battery. The present invention alkali-metalizes the three-dimensional supporting conductive framework, which can directly compensate for the initial capacity loss, improve the initial Coulombic efficiency of the solid-state composite alkali metal electrode, and increase the reversible capacity of the battery. Moreover, coating a solid-state polymer-like electrolyte on the alkali-metalized three-dimensional supporting conductive framework can not only isolate the reaction of alkali metal with water in the air, improve the safety performance, and effectively inhibit side reactions at the electrode / electrolyte interface but also enhance the adaptability to volume changes caused by the stripping or deposition of alkali metal, thereby improving the ability to resist dendrite growth. The secondary battery prepared based on this solid-state composite alkali metal anode has excellent cycle performance and safety performance.

[0007] To achieve the object of the present invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a solid composite alkali metal negative electrode, and the solid composite alkali metal negative electrode includes an alkali metalized three-dimensional support conductive framework, and a solid polymer-like electrolyte is coated on the alkali metalized three-dimensional support conductive framework.

[0009] In the present invention, the three-dimensional support conductive framework is alkali metalized, which can directly compensate for the initial capacity loss, improve the initial Coulomb efficiency of the solid composite alkali metal electrode, and improve the reversible capacity of the battery; moreover, coating the solid polymer-like electrolyte on the alkali metalized three-dimensional support conductive framework can not only isolate the reaction of alkali metal with water in the air, improve the safety performance and effectively inhibit the side reactions at the electrode / electrolyte interface, but also improve the adaptability to the volume change caused by the stripping or deposition of alkali metal, thereby improving the ability to resist dendrite growth. The secondary battery prepared based on this solid composite alkali metal negative electrode has excellent cycle performance and safety performance.

[0010] In the present invention, the three-dimensional support conductive framework can provide excellent mechanical properties and electrical conductivity, and ensure more uniform dispersion of alkali metal.

[0011] In the present invention, the alkali metalized three-dimensional support conductive framework refers to that the three-dimensional support conductive framework carries alkali metal, and the solid polymer-like electrolyte is coated on the three-dimensional support conductive framework and covers the alkali metal.

[0012] Preferably, the alkali metalization includes lithiation or sodiation.

[0013] Preferably, the three-dimensional support conductive framework is a three-dimensional support carbon-based framework or a three-dimensional support metal-based framework.

[0014] Preferably, the three-dimensional support carbon-based framework includes any one or a combination of at least two of carbon fiber cloth, carbon fiber paper, carbon fiber felt or an electrospun organic polymer framework, and is preferably carbon fiber cloth.

[0015] Preferably, the three-dimensional support metal-based framework includes any one or a combination of at least two of aluminum mesh, copper mesh, nickel mesh, nickel foam, copper foam or stainless steel foam mesh.

[0016] Preferably, the solid polymer-like electrolyte includes a polymer and a metal salt.

[0017] Preferably, the polymer includes any one or a combination of at least two of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), polyvinylidene chloride (PVDC), or polyionic liquid, preferably polyionic liquid.

[0018] In the present invention, the polyionic liquid has good flexibility and can better adapt to the volume changes generated during the metal stripping / deposition process, thereby enhancing the ability of the electrode to inhibit dendrite growth. In addition, the polyionic liquid can effectively provide ion channels and further optimize the performance of the solid composite alkali metal electrode. Moreover, compared with traditional polymers, it has more excellent thermal stability and electrochemical stability.

[0019] Preferably, the solid polymer electrolyte further includes a plasticizer.

[0020] Preferably, the solid polymer electrolyte further includes an inorganic material.

[0021] Preferably, based on the mass of the solid composite lithium metal anode, the mass ratio of the solid polymer electrolyte is 70-90%, for example, it can be 70%, 80%, or 90%, etc.

[0022] In a second aspect, the present invention provides a method for preparing a solid composite alkali metal anode as described in the first aspect, and the preparation method includes the following steps:

[0023] Perform pre-alkali metalization treatment on the three-dimensional support conductive skeleton to be processed to obtain an alkali metalized three-dimensional support conductive skeleton.

[0024] Compound the precursor solution of the solid polymer electrolyte and the alkali metalized three-dimensional support conductive skeleton, and then carry out a polymerization reaction to obtain the solid composite alkali metal anode.

[0025] Preferably, when the three-dimensional support conductive skeleton to be processed is a three-dimensional support carbon-based skeleton to be processed, before the pre-alkali metalization treatment of the three-dimensional support carbon-based skeleton to be processed, surface treatment and heat treatment are first carried out.

[0026] The preparation method provided by the present invention is simple, low-cost and easy to operate, avoiding cumbersome equipment requirements and high costs, and providing the possibility for large-scale production of batteries.

[0027] In the present invention, the three-dimensional support conductive framework to be processed is pre-alkali metalized to obtain an alkali metalized three-dimensional support conductive framework. This method is simple and convenient to operate, and has high safety during the preparation process. At the same time, the pre-alkali metalization treatment provided by the present invention can precisely control the pre-alkali metalization process, thereby improving the consistency and performance stability of the solid composite alkali metal negative electrode.

[0028] Preferably, the surface treatment includes pickling and alkali washing.

[0029] Preferably, the pickling medium for pickling includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid, acetic acid, perchloric acid, hydrofluoric acid, potassium permanganate or hydrogen peroxide.

[0030] Preferably, the treatment temperature for pickling is 20 - 80 °C, for example, it can be 20 °C, 40 °C, 60 °C or 80 °C, etc., and preferably 30 °C.

[0031] Preferably, during the pickling process, ultrasonic waves are accompanied.

[0032] Preferably, the pickling time is 1 - 90 min, for example, it can be 1 min, 5 min, 10 min, 30 min, 50 min, 70 min or 90 min, etc., and preferably 15 - 30 min.

[0033] Preferably, the concentration of the pickling medium for pickling is 1 - 8 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L or 8 mol / L, etc., and preferably 5 - 6 mol / L.

[0034] Preferably, the alkali washing medium for alkali washing includes any one or a combination of at least two of aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous sodium carbonate solution or aqueous sodium bicarbonate solution.

[0035] Preferably, the concentration of the alkali washing medium for alkali washing is 1 - 4 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L, etc., and preferably 2 mol / L.

[0036] Preferably, in the atmosphere of the heat treatment, it includes any one or a combination of at least two of nitrogen, argon, hydrogen, carbon monoxide or carbon dioxide.

[0037] Preferably, the temperature of the heat treatment is 300 - 800 °C, for example, it can be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C or 800 °C, etc., and the holding time is 1 - 6 h, for example, it can be 1 h, 2 h, 3 h, 4 h, 5 h or 6 h, etc.

[0038] Preferably, the temperature of the heat treatment is 800 °C and the heat preservation time is 1 h.

[0039] Preferably, the heating rate of the heat treatment is 1-10 °C / min, for example, it can be 1 °C / min, 3 °C / min, 5 °C / min, 7 °C / min or 9 °C / min, etc., and preferably 4-6 °C / min.

[0040] Preferably, after the heat treatment, cleaning and drying are also carried out, and the cleaning agent used for cleaning includes water or alcohol.

[0041] Preferably, the method of pre-alkali metalization treatment includes chemical immersion method or mechanical pressing method.

[0042] Preferably, the specific steps of the chemical immersion method include:

[0043] Immerse the three-dimensional supported carbon-based framework to be treated in an alkali metal organic solution.

[0044] Preferably, the alkali metal organic solution includes an alkali metal, an additive and a solvent.

[0045] Preferably, the concentration of the alkali metal organic solution is 0.01-5 mol / L, for example, it can be 0.01 mol / L, 0.01 mol / L, 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, etc., and preferably 0.5-1 mol / L.

[0046] It should be noted that the above concentration refers to the concentration of the alkali metal in the alkali metal organic solution.

[0047] In the present invention, an alkali metal organic solution with an appropriate concentration can provide an appropriate amount of alkali metal for the three-dimensional supported carbon-based framework, make up for the irreversible capacity loss of the electrode in the first cycle, and improve the initial Coulomb efficiency and energy density of the battery.

[0048] Preferably, the additive includes any one or a combination of at least two of biphenyl, biphenylene, benzidine, 2-fluorobiphenyl, 2-chlorobiphenyl, p-terphenyl, o-terphenyl, m-terphenyl, p-pentaphenyl, p-hexaphenyl, 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, 3-ethylbiphenyl, 4-ethylbiphenyl, 4-benzylbiphenyl, 4-butyrylbiphenyl, 4-propionylbiphenyl, naphthalene, 1-ethylnaphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 2-ethylnaphthalene, 2-phenylnaphthalene, pyrene, 1-acetylpyrene, naphtho[2,3-a]pyrene, 3,4-benzopyrene, methoxypyrene, anthracene, dibenzoanthracene or ethylanthracene, and preferably biphenyl.

[0049] Preferably, the solvent includes any one or a combination of at least two of 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, isopropyl ether, methyl butyl ether, benzyl butyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, 1-butyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, trimethyltetrahydrofuran, 2,3-dichlorotetrahydrofuran, 3,4-epoxytetrahydrofuran, 2-ethoxytetrahydrofuran or 2-methoxytetrahydrofuran, preferably tetrahydrofuran.

[0050] Preferably, the alkali metal includes a metal lithium material or a metal sodium material.

[0051] Preferably, the metal lithium material includes any one or a combination of at least two of lithium flakes, lithium foils, lithium tapes or lithium alloys.

[0052] Preferably, the metal sodium material includes any one or a combination of at least two of sodium flakes, sodium foils, sodium tapes or sodium alloys.

[0053] Preferably, the time of the soaking treatment is 1 min to 3 h, for example, it can be 1 min, 3 min, 10 min, 20 min, 30 min, 1 h, 2 h or 3 h, etc., preferably 1 to 10 min.

[0054] Preferably, after the soaking treatment, a cleaning step is further performed, and the cleaning solvent used in the cleaning process includes any one or a combination of at least two of 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, isopropyl ether, methyl butyl ether, benzyl butyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, 1-butyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, trimethyltetrahydrofuran, 2,3-dichlorotetrahydrofuran, 3,4-epoxytetrahydrofuran, 2-ethoxytetrahydrofuran or 2-methoxytetrahydrofuran.

[0055] Preferably, the specific steps of the mechanical pressing method include:

[0056] Mechanically pressing the alkali metal foil and the three-dimensional support metal matrix framework.

[0057] Preferably, the precursor solution of the solid-state polymer electrolyte includes a polymer monomer, a metal salt and a solvent.

[0058] Preferably, the polymer monomer includes any one or a combination of at least two of ethylene oxide, acrylonitrile, vinylidene fluoride, methyl methacrylate, propylene oxide, vinylidene chloride or a polymerizable ionic liquid monomer, preferably the polymerizable ionic liquid monomer.

[0059] Preferably, the polymerizable ionic liquid monomer contains an unsaturated group. Exemplarily, for example, it can be a carbon-carbon double bond or the like.

[0060] Preferably, the cation of the polymerizable ionic liquid monomer includes any one or a combination of at least two of imidazolium cation, pyrrolidinium cation, pyridinium cation, piperidinium cation, quaternary ammonium cation, quaternary phosphonium cation, morpholinium cation or guanidinium cation.

[0061] Preferably, the anion of the polymerizable ionic liquid monomer includes Cl - , Br - , I - , OH - , SO 3 2- , CO 3 2- , COO - , HCO 3 - , PO 4 3- , BF 4 - , PF 6 - , FSI - , TFSI - , or NO 3 - or any one or a combination of at least two thereof.

[0062] Preferably, the metal salt is a lithium salt or a sodium salt.

[0063] Preferably, the lithium salt includes any one or a combination of at least two of LiTFSI, LiFSI, LiClO 4 , LiBOB, LiDFOB, LiPF 6 , or LiBF 4 or any one or a combination of at least two thereof.

[0064] Preferably, the sodium salt includes any one or a combination of at least two of NaTFSI, NaFSI, NaClO 4 , NaOTF, NaBOB, NaDFOB, NaPF 6 , or NaBF 4 or any one or a combination of at least two thereof.

[0065] Preferably, in the precursor solution of the solid-state polymer electrolyte, the addition amount of the metal salt accounts for 10% to 200% of the mass of the polymer monomer, for example, it can be 10%, 20%, 40%, 60%, 80%, 100%, 120%, 140%, 160%, 180% or 200%, etc., and preferably 60% to 120%.

[0066] Preferably, in the precursor solution of the solid-state polymer electrolyte, the solvent includes any one or a combination of at least two of acetone, N-methyl-2-pyrrolidone, 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, isopropyl ether, methyl butyl ether, benzyl butyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, 1-butyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, trimethyltetrahydrofuran, 2,3-dichlorotetrahydrofuran, 3,4-epoxytetrahydrofuran, 2-ethoxytetrahydrofuran, or 2-methoxytetrahydrofuran.

[0067] Preferably, a plasticizer is further included in the precursor solution of the solid-state polymer electrolyte.

[0068] The purpose of introducing the plasticizer in the present invention is to improve the performance of the solid-state polymer electrolyte.

[0069] Preferably, the plasticizer includes a small molecule organic solvent and / or a non-polymeric ionic liquid.

[0070] It should be noted that the non-polymeric ionic liquid refers to an ionic liquid without a polymerization site.

[0071] Preferably, the small molecule organic solvent includes any one or a combination of at least two of vinylidene fluoride carbonate (FEC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or vinylene carbonate (VC).

[0072] Preferably, the cation of the non-polymeric ionic liquid includes any one or a combination of at least two of imidazolium cation, pyrrolidinium cation, pyridinium cation, piperidinium cation, quaternary ammonium cation, quaternary phosphonium cation, morpholinium cation, or guanidinium cation.

[0073] Preferably, the anion of the non-polymeric ionic liquid includes Cl - , Br - , I - , OH - , SO 3 2- , CO 3 2- , COO - , HCO 3 - , PO 4 3- , BF 4 - , PF 6- , FSI - , TFSI - or NO 3 - or a combination of any one or at least two of them.

[0074] Preferably, the addition amount of the plasticizer accounts for 1-50% of the mass of the polymer monomer, and can be, for example, 1%, 5%, 10%, 20%, 30%, 40% or 50%, etc.

[0075] In the present invention, a plasticizer with an appropriate addition amount can reduce the crystallinity of the solid-state polymer electrolyte and promote the dissociation of metal salts, thereby enhancing the overall ionic conductivity of the electrolyte.

[0076] Preferably, the precursor solution of the solid-state polymer electrolyte further includes an inorganic material.

[0077] The purpose of introducing the inorganic material in the present invention is to improve the comprehensive performance of the solid-state polymer electrolyte.

[0078] Preferably, the inorganic material includes SiO 2 , TiO 2 , Al 2 O 3 , h-BN (hexagonal boron nitride), LLZO (lithium lanthanum zirconium oxide), LATP (lithium aluminum titanium phosphate), LGAP (lithium germanium aluminum phosphate), LLZTO (lithium lanthanum zirconium titanium oxide), GO (graphene oxide) or MOF (metal-organic framework), or a combination of any one or at least two of them.

[0079] Preferably, the particle size range of the inorganic material is 10 nm to 50 μm, and can be, for example, 10 nm, 100 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, etc., and preferably 10-500 nm.

[0080] Preferably, the addition amount of the inorganic material accounts for 1-50% of the mass of the polymer monomer, and can be, for example, 1%, 5%, 10%, 20%, 30%, 40% or 50%, etc.

[0081] In the present invention, an inorganic material with an appropriate addition amount has the following advantages: (1) weakening the interaction between the polymer and metal ions and promoting the dissociation of metal salts; (2) reducing the crystallinity of the polymer, improving the free movement ability of the chain segments, and thus enhancing the ion transport ability of the polymer; (3) the inorganic filler / polymer two-phase interface can provide an additional transport path for metal ions; (4) it can improve the mechanical properties such as the Young's modulus and tensile strength of the electrolyte.

[0082] Preferably, the compounding method includes in-situ melt perfusion method or dropwise addition method.

[0083] Preferably, the polymerization reaction method includes thermal initiation polymerization or photoinitiation polymerization.

[0084] Preferably, during the thermal initiation polymerization, the addition amount of the thermal initiator used accounts for 0.1-3% of the mass of the polymer monomer. For example, it can be 0.1%, 0.5%, 1%, 2% or 3%, etc., and preferably 0.5%.

[0085] Preferably, the thermal initiator includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, dialkyl peroxide, potassium persulfate, cumene hydroperoxide or tert-butyl hydroperoxide.

[0086] Preferably, the reaction temperature of the thermal initiation polymerization is -10-180 °C. For example, it can be -10 °C, 0 °C, 10 °C, 50 °C, 100 °C, 150 °C or 180 °C, etc., and preferably 80 °C.

[0087] Preferably, the reaction time of the thermal initiation polymerization is 12-24 h. For example, it can be 12 h, 16 h, 20 h or 24 h, etc., and preferably 12 h.

[0088] Preferably, during the photoinitiation polymerization, the addition amount of the photoinitiator used accounts for 0.1-3% of the mass of the polymer monomer. For example, it can be 0.1%, 0.5%, 1%, 2% or 3%, etc., and preferably 1%.

[0089] Preferably, the photoinitiator includes any one or a combination of at least two of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (photoinitiator 819), 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone or 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, and preferably bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (photoinitiator 819).

[0090] Preferably, the ultraviolet light wavelength of the photoinitiator is 200-400 nm. For example, it can be 300 nm, 300 nm, 350 nm, 365 nm or 400 nm, etc., and the photoinitiation polymerization time is 0.01-3 h. For example, it can be 0.01 h, 0.1 h, 1 h, 2 h or 3 h, etc.

[0091] Preferably, the ultraviolet light wavelength of the photoinitiator is 315-400 nm, and the photoinitiation polymerization time is 2-4 min. For example, it can be 2 min, 3 min or 4 min, etc.

[0092] Preferably, the preparation method includes the following steps:

[0093] (1) The three-dimensional supported carbon-based framework to be processed is successively subjected to surface treatment, heat treatment, cleaning, and drying to obtain a three-dimensional supported carbon-based framework with alkali-metal affinity; wherein, the surface treatment includes pickling and alkali washing carried out successively. The temperature of the pickling is 20-80 °C, ultrasonic waves are accompanied during the pickling process, the pickling time is 1-90 min, the concentration of the pickling medium for pickling is 1-8 mol / L, and the concentration of the alkali washing medium for alkali washing is 1-4 mol / L; the temperature of the heat treatment is 300-800 °C, the heat preservation time is 1-6 h, and the heating rate is 1-10 °C / min.

[0094] (2) The three-dimensional supported carbon-based framework with alkali-metal affinity is immersed in an alkali-metal organic solution for 1 min to 3 h, and then washed with a cleaning solvent and dried to obtain an alkali-metalized three-dimensional supported carbon-based framework; wherein, the alkali-metal organic solution includes an alkali metal, an additive, and a solvent, and the concentration of the alkali-metal organic solution is 0.01-5 mol / L.

[0095] (3) A polymer monomer, a metal salt, a solvent, and a plasticizer / inorganic material are mixed to obtain a precursor solution of a solid-state polymer electrolyte; wherein, in the precursor solution of the solid-state polymer electrolyte, the addition amount of the metal salt accounts for 10%-200% of the mass of the polymer monomer, and the addition amount of the plasticizer / inorganic material accounts for 1%-50% of the mass of the polymer monomer.

[0096] Using the in-situ melt perfusion method, the precursor solution of the solid-state polymer electrolyte and the alkali-metalized three-dimensional supported carbon-based framework are compounded. After the solvent is volatilized, a polymerization reaction is carried out to obtain a solid-state composite alkali-metal negative electrode; wherein, the polymerization reaction method includes thermal initiation polymerization or photoinitiation polymerization. During the thermal initiation polymerization process, the addition amount of the thermal initiator used accounts for 0.1%-3% of the mass of the polymer monomer, and the reaction temperature of the thermal initiation polymerization is -10-180 °C; during the photoinitiation polymerization process, the addition amount of the photoinitiator used accounts for 0.1%-3% of the mass of the polymer monomer, the ultraviolet light wavelength of the photoinitiator is 200-400 nm, and the photoinitiation polymerization time is 0.01-3 h.

[0097] In a third aspect, the present invention provides a secondary battery, which includes the solid-state composite alkali-metal negative electrode as described in the first aspect, or includes the solid-state composite alkali-metal negative electrode prepared by the preparation method as described in the second aspect.

[0098] It should be noted that in the secondary battery, a conventional liquid electrolyte or a solid electrolyte can be used in combination for assembly to obtain a solid-state battery or a liquid battery respectively.

[0099] The numerical ranges described in the present invention include not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said ranges.

[0100] Compared with the prior art, the present invention has the following beneficial effects:

[0101] (1) The present invention alkali-metalizes the three-dimensional supported conductive skeleton, which can directly compensate for the initial capacity loss, improve the initial Coulombic efficiency of the solid-state composite alkali-metal electrode, and increase the reversible capacity of the battery. Moreover, coating the alkali-metalized three-dimensional supported conductive skeleton with a solid-state polymer-like electrolyte can not only isolate the reaction of alkali metals with water in the air, improve the safety performance and effectively inhibit the side reactions at the electrode / electrolyte interface, but also enhance the adaptability to volume changes caused by the stripping or deposition of alkali metals, thereby improving the ability to resist dendrite growth. The secondary battery prepared based on this solid-state composite alkali-metal negative electrode has excellent cycle performance and safety performance.

[0102] (2) The preparation method provided by the present invention is simple, low-cost and easy to operate, avoiding cumbersome equipment requirements and high costs, and providing the possibility for large-scale production of batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] Figure 1 is a schematic structural diagram of the solid-state composite lithium-metal negative electrode provided in Example 1 of the present invention.

[0104] Figure 2 is an SEM image of the solid-state composite lithium-metal negative electrode provided in Example 1 of the present invention.

[0105] Wherein, 1 - three-dimensional supported conductive skeleton with metal lithiation; 2 - solid-state polymer-like electrolyte; 3 - metallic lithium. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0106] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the said embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0107] Example 1

[0108] This example provides a solid-state composite lithium-metal negative electrode, and its schematic structural diagram is as Figure 1As shown, the solid composite lithium metal anode includes a metal-lithiated three-dimensional supported carbon-based framework 1, and a solid polymer-like electrolyte 2 (the blue cuboid part and the blue line part) is coated on the metal-lithiated three-dimensional supported carbon-based framework 1; wherein, metal lithium 3 is uniformly dispersed in the three-dimensional supported carbon-based framework 1, and the solid polymer-like electrolyte 2 includes: poly-VEIMTFSI, LiTFSI, and LLZO (the particle part in the planar structure schematic diagram).

[0109] Among them, the three-dimensional supported carbon-based framework is a carbon fiber cloth.

[0110] This embodiment also provides a preparation method of the solid composite lithium metal anode as described above, including the following steps:

[0111] (1) Cut the commercially available carbon fiber cloth purchased into a size of 5×5 cm, and then soak it in a 6 mol / L HNO 3 solution and perform ultrasonic pickling 3 times, 30 minutes each time, the pickling temperature is 30 °C, and after pickling, dry it at 70 °C; then soak it in a 2 mol / L aqueous NaOH solution for alkali washing, and after completion, put it into a corundum boat, and in a tubular furnace under a nitrogen atmosphere, heat it to 800 °C at a heating rate of 5 °C / min, perform heat treatment for 1 h, then ultrasonically clean it with deionized water for 30 minutes, and dry the cleaned carbon fiber cloth in a vacuum oven at 70 °C for 24 h to obtain a three-dimensional supported carbon-based framework with lithiophilicity.

[0112] (2) Under a nitrogen atmosphere, immerse the three-dimensional supported carbon-based framework with lithiophilicity in a 0.5 mL 0.5 mol / L solution of lithium biphenyl in 2-methyltetrahydrofuran for 3 minutes, and after completion, wash it three times with 2-methyltetrahydrofuran and dry it to obtain a metal-lithiated three-dimensional supported carbon-based framework.

[0113] (3) Dissolve polyionic liquid monomer VEIMTFSI (1-vinyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethylsulfonyl)imide salt), LiTFSI, LLZO, and photoinitiator 819 in ethylene glycol dimethyl ether according to a mass ratio of 1:1:0.2:0.01 to obtain a precursor solution of the solid polymer-like electrolyte; uniformly coat the precursor solution of the solid polymer-like electrolyte on the metal-lithiated three-dimensional supported carbon-based framework, dry it in a vacuum oven at 80 °C for 6 h, and after the solvent volatilizes, irradiate it with ultraviolet light for 2 minutes for photoinitiated polymerization to obtain a solid composite lithium metal electrode with a solid electrolyte coating.

[0114] Among them, in the precursor solution of the solid-state polymer electrolyte, the mass ratio of LiTFSI to the polyionic liquid monomer is 1:1, the particle size of LLZO is 300 nm, and the addition amount of LLZO accounts for 20% of the mass of the polyionic liquid monomer; the addition amount of photoinitiator 819 accounts for 1% of the mass of the polyionic liquid monomer; the photoinitiator 819 initiates a polymerization reaction under irradiation with ultraviolet light at a wavelength of 365 nm.

[0115] Figure 2 The SEM image of the solid-state composite lithium metal anode provided in this example is shown. As can be seen from the figure, the solid-state polymer electrolyte is coated on the three-dimensional support conductive framework of metal lithiation. This can not only isolate the reaction of lithium with water in the air, improve the safety performance and effectively inhibit the side reactions at the electrode / electrolyte interface, but also improve the adaptability to the volume change caused by the stripping or deposition of lithium, thereby improving the ability to resist dendrite growth. The secondary battery prepared based on this solid-state composite alkali metal anode has excellent cycle performance and safety performance.

[0116] Example 2

[0117] This example provides a solid-state composite lithium metal anode, and the solid-state composite lithium metal anode includes a three-dimensional support carbon-based framework of metal lithiation, and the three-dimensional support carbon-based framework of metal lithiation is coated with a solid-state polymer electrolyte; among them, metal lithium is uniformly dispersed in the three-dimensional support carbon-based framework, and the solid-state polymer electrolyte includes: poly-VEIMTFSI, LiFSI, and FEC.

[0118] Among them, the three-dimensional support carbon-based framework is carbon fiber cloth.

[0119] This example also provides a preparation method of the solid-state composite lithium metal anode as described above, including the following steps:

[0120] (1) Cut the commercially available carbon fiber cloth purchased into a size of 5×5 cm, and then soak it in 1 mol / L HNO 3 solution and perform ultrasonic pickling 3 times, 30 minutes each time, the pickling temperature is 20 °C, and after pickling, dry it at 70 °C; then soak it in 4 mol / L KOH aqueous solution for alkali washing, and after completion, put it into a corundum boat and heat it to 500 °C at a heating rate of 4 °C / min in a tube furnace under a nitrogen atmosphere for 3 h of heat treatment, and then ultrasonically clean it with deionized water for 30 minutes. The cleaned carbon fiber cloth is dried in a vacuum oven at 70 °C for 24 h to obtain a three-dimensional support carbon-based framework with lithiophilicity.

[0121] (2) Under a nitrogen atmosphere, the lithiophilic three-dimensional supported carbon-based framework was placed in 0.5 mL of a 0.75 mol / L solution of lithium biphenyl in 2-methyltetrahydrofuran and soaked for 2 min. After that, it was washed three times with 2-methyltetrahydrofuran and dried to obtain a lithiated three-dimensional supported carbon-based framework.

[0122] (3) The ionic liquid monomer VEIMTFSI (1-vinyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethylsulfonyl)imide salt), LiFSI, FEC, and photoinitiator 819 were dissolved in ethylene glycol dimethyl ether according to a mass ratio of 1:0.5:0.2:0.01 to obtain a precursor solution of a solid-like polymer electrolyte. The precursor solution of the solid-like polymer electrolyte was uniformly coated on the lithiated three-dimensional supported carbon-based framework and dried in a vacuum oven at 80 °C for 6 h. After the solvent evaporated, it was irradiated with ultraviolet light for 3 min for photoinitiated polymerization to obtain a solid composite lithium metal electrode with a solid electrolyte coating.

[0123] Among them, in the precursor solution of the solid-like polymer electrolyte, the mass ratio of LiFSI to the polyionic liquid monomer is 0.5:1, the addition amount of FEC accounts for 20% of the mass of the polyionic liquid monomer; the addition amount of photoinitiator 819 accounts for 1% of the mass of the polyionic liquid monomer; photoinitiator 819 initiates a polymerization reaction under ultraviolet light irradiation with a wavelength of 365 nm.

[0124] Example 3

[0125] This example provides a solid composite lithium metal negative electrode, which includes a lithiated three-dimensional supported carbon-based framework, and a solid-like polymer electrolyte is coated on the lithiated three-dimensional supported carbon-based framework. Among them, metallic lithium is uniformly dispersed in the three-dimensional supported carbon-based framework, and the solid-like polymer electrolyte includes: poly-VEIMTFSI, LiClO 4 and SiO 2 .

[0126] Among them, the three-dimensional supported carbon-based framework is carbon fiber cloth.

[0127] This example also provides a preparation method of the solid composite lithium metal negative electrode as described above, including the following steps:

[0128] (1) The commercially available carbon fiber cloth purchased was cut into a size of 5×5 cm, and then it was soaked in 8 mol / L HNO 3Ultrasonic pickling was carried out 3 times in the solution, with each time lasting 10 min. The pickling temperature was 80 °C, and after pickling, it was dried at 70 °C. Subsequently, it was soaked in a 1 mol / L aqueous sodium bicarbonate solution for alkali washing. After completion, it was placed in a corundum boat and heated to 30 °C at a heating rate of 6 °C / min in a tubular furnace under a nitrogen atmosphere for 6 h of heat treatment. Then, it was ultrasonically cleaned with deionized water for 30 min, and the cleaned carbon fiber cloth was dried in a vacuum oven at 70 °C for 24 h to obtain a three-dimensional supported carbon-based framework with lithiophilicity.

[0129] (2) Under a nitrogen atmosphere, the three-dimensional supported carbon-based framework with lithiophilicity was placed in a 0.5 mL 2-methyltetrahydrofuran solution of 1 mol / L lithium biphenyl for soaking for 1 min. After completion, it was washed three times with 2-methyltetrahydrofuran and dried to obtain a metal-lithiated three-dimensional supported carbon-based framework.

[0130] (3) The ionic liquid monomer VEIMTFSI (1-vinyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethylsulfonyl)imide), LiClO 4 , SiO 2 and photoinitiator 819 were dissolved in ethylene glycol dimethyl ether according to a mass ratio of 1:2:0.05:0.01 to obtain a precursor solution of a solid-like polymer electrolyte. The precursor solution of the solid-like polymer electrolyte was uniformly coated on the metal-lithiated three-dimensional supported carbon-based framework and dried in a vacuum oven at 80 °C for 6 h. After the solvent evaporated, it was irradiated with ultraviolet light for 4 min for photoinitiated polymerization to obtain a solid composite lithium metal electrode with a solid electrolyte coating.

[0131] Among them, in the precursor solution of the solid-like polymer electrolyte, the mass ratio of LiClO 4 to the polyionic liquid monomer is 2:1, the particle size of SiO 2 is 100 nm, and the addition amount of SiO 2 accounts for 5% of the mass of the polyionic liquid monomer; the addition amount of photoinitiator 819 accounts for 1% of the mass of the polyionic liquid monomer; photoinitiator 819 initiates the polymerization reaction under ultraviolet light irradiation with a wavelength of 365 nm.

[0132] Example 4

[0133] The difference between this example and Example 1 is that the solid composite lithium metal electrode is replaced with a solid composite sodium metal electrode, that is, the 2-methyltetrahydrofuran solution of lithium biphenyl in step (2) is replaced with a 1,2-dimethoxyethane solution of sodium biphenyl, and after soaking, it is washed with 1,2-dimethoxyethane.

[0134] The remaining preparation methods and parameters are the same as those in Example 1.

[0135] Example 5

[0136] The difference between this example and Example 1 is that step (1) is not carried out, and step (2) is replaced by the following steps:

[0137] Stack the commercially available copper mesh and lithium foil purchased together, and directly use a roll press to press the two together to obtain a three-dimensional supported metal matrix framework with lithiated metal.

[0138] The remaining preparation methods and parameters are the same as those in Example 1.

[0139] Example 6

[0140] The difference between this example and Example 1 is that in step (3), photoinitiator 819 is replaced by thermal initiator azobisisobutyronitrile, and its addition amount is 1% of the mass of the polyionic liquid monomer. The conditions for thermal initiation polymerization are: drying in a vacuum oven at 80 °C for 12 h.

[0141] The remaining preparation methods and parameters are the same as those in Example 1.

[0142] Example 7

[0143] The difference between this example and Example 1 is that the soaking time described in step (2) is 1 min.

[0144] The remaining preparation methods and parameters are the same as those in Example 1.

[0145] Example 8

[0146] The difference between this example and Example 1 is that the coating amount of the precursor solution of the solid-state polymer electrolyte in step (3) is adjusted so that the mass ratio of the solid-state polymer electrolyte is 30% (based on the mass of the solid composite lithium metal anode).

[0147] The remaining preparation methods and parameters are the same as those in Example 1.

[0148] Example 9

[0149] The difference between this example and Example 1 is that the coating amount of the precursor solution of the solid-state polymer electrolyte in step (3) is adjusted so that the mass ratio of the solid-state polymer electrolyte is 98% (based on the mass of the solid composite lithium metal anode).

[0150] The remaining preparation methods and parameters are the same as those in Example 1.

[0151] Example 10

[0152] The difference between this example and Example 1 is that step (1) is not carried out.

[0153] The remaining preparation methods and parameters are the same as those in Example 1.

[0154] Example 11

[0155] The difference between this example and Example 1 is that the concentration of the solution of lithium biphenyl in 2-methyltetrahydrofuran described in step (2) is 0.01 mol / L.

[0156] The remaining preparation methods and parameters are the same as those in Example 1.

[0157] Example 12

[0158] The difference between this example and Example 1 is that the concentration of the solution of lithium biphenyl in 2-methyltetrahydrofuran described in step (2) is 5 mol / L.

[0159] The remaining preparation methods and parameters are the same as those in Example 1.

[0160] Example 13

[0161] The difference between this example and Example 1 is that LLZO is not added in step (3).

[0162] The remaining preparation methods and parameters are the same as those in Example 1.

[0163] Comparative Example 1

[0164] This comparative example provides a commercial lithium foil anode.

[0165] Comparative Example 2

[0166] The difference between this comparative example and Example 1 is that step (3) is not carried out, that is, a solid-state polymer electrolyte is not introduced.

[0167] The remaining preparation methods and parameters are the same as those in Example 1.

[0168] Comparative Example 3

[0169] The difference between this comparative example and Example 1 is that step (2) is not carried out, that is, the three-dimensional support carbon-based framework is not lithiated with metallic lithium.

[0170] The remaining preparation methods and parameters are the same as those in Example 1.

[0171] Performance Test

[0172] Based on the anodes provided by the above examples and comparative examples, secondary batteries are fabricated, and the specific steps include:

[0173] In a glove box filled with argon, a polypropylene membrane (PP) is used as the separator, the cathode is a lithium iron phosphate material loaded on an aluminum foil current collector, the anode is the anode provided by Examples 1-3, 5-13 and Comparative Examples 1-3, and 1 M LiPF is added 6An electrolyte with a volume ratio of ethylene carbonate to diethyl carbonate of 1:1 is used to assemble a lithium metal battery; alternatively, in a glove box filled with argon, a polypropylene film (PP) is used as the separator, the positive electrode is a sodium vanadium phosphate material loaded on an aluminum foil current collector, and the negative electrode is the negative electrode provided in Example 4 above (punched into a diameter of 12 mm), and 1M NaPF 6 An electrolyte with a volume ratio of ethylene carbonate to diethyl carbonate of 1:1 is used to assemble a sodium metal battery.

[0174] The cyclic performance of the above lithium metal battery and sodium metal battery is tested, and the test method includes:

[0175] The test voltage is 2-4V. First, constant current charge and discharge are carried out at a rate of 0.05C (calculated based on the theoretical specific capacity of the active material of the positive electrode, the theoretical specific capacity of lithium iron phosphate is 170 mAh / g). After five cycles of activation, long-term cyclic tests are carried out at room temperature of 25°C and a rate of 0.1C, and the discharge specific capacity, Coulomb efficiency of the first cycle of the battery and the capacity retention rate after 100 cycles are recorded.

[0176] The results are shown in Table 1.

[0177] Table 1

[0178]

[0179]

[0180] Analysis:

[0181] As can be seen from Example 1, the solid composite alkali metal electrode provided by the present invention is used in the lithium metal battery system, which improves the first-cycle Coulomb efficiency, cyclic performance and capacity retention rate after 100 cycles of the battery, indicating that constructing a polymer on the electrode surface can effectively inhibit the side reactions at the electrode / electrolyte interface. As can be seen from Example 4, the solid composite alkali metal electrode provided by the present invention is also applicable to the sodium metal battery system. As can be seen from Example 5, for the solid composite lithium metal electrode with physical lithiumation, the first-cycle capacity and first-cycle Coulomb efficiency are improved, but the capacity retention rate after 100 cycles is slightly lower than that of Example 1. As can be seen from Example 6, whether a photoinitiator or a thermal initiator is used, the obtained effects are similar, indicating that the initiation method has little influence on the whole system. As can be seen from Example 7, after reducing the soaking time of prelithiation, the first-cycle capacity, Coulomb efficiency and capacity retention rate after 100 cycles all decrease.

[0182] As can be seen from the comparison between Example 1 and Examples 8-9, if the mass ratio of the solid polymer electrolyte is too small, it is not conducive to alleviating the volume expansion of metallic lithium, and the flexibility is poor, resulting in a decrease in the capacity retention rate; if the mass ratio of the solid polymer electrolyte is too large, the electrode is too thick and the ion transport path is extended, which is not conducive to capacity performance.

[0183] It can be seen from the comparison between Example 1 and Example 10 that if step (1) is not carried out, that is, the three-dimensional supported carbon-based skeleton does not have lithiophilicity before metal lithiation, it is not conducive to the subsequent prelithiation process, resulting in incomplete initial capacity and decreased capacity retention rate and Coulomb efficiency.

[0184] It can be seen from the comparison between Example 1 and Examples 11-12 that if the concentration of the 2-methyltetrahydrofuran solution of lithium biphenyl described in step (2) is too low, sufficient metal lithium cannot be provided to support the cycle; if the concentration of the 2-methyltetrahydrofuran solution of lithium biphenyl described in step (2) is too high, the deposition of metal lithium is uneven, and after too much prelithiation, there is a risk of exposure and side reactions with the electrolyte, which is not conducive to capacity retention.

[0185] It can be seen from the comparison between Example 1 and Example 13 that if LLZO is not added in step (3), that is, inorganic materials are not introduced, the mechanical properties and ionic conductivity of the overall negative electrode will decrease, which is not conducive to capacity performance.

[0186] It can be seen from the comparison between Example 1 and Comparative Example 1 that in the traditional lithium metal negative electrode battery system, due to the side reactions at the electrode / electrolyte interface, the capacity retention rate after 100 cycles decreases compared with Example 1.

[0187] It can be seen from the comparison between Example 1 and Comparative Example 2 that if a solid polymer electrolyte is not introduced, the cyclic capacity retention rate after 100 cycles decreases, indicating that the side reactions at the electrode / electrolyte interface are relatively serious.

[0188] It can be seen from the comparison between Example 1 and Comparative Example 3 that if the three-dimensional supported carbon-based skeleton is not metal lithiated, the first-cycle discharge capacity, Coulomb efficiency, and cyclic capacity retention rate after 100 cycles all decrease significantly.

[0189] The applicant declares that the present invention uses the above examples to illustrate the process method of the present invention, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A solid composite alkali metal negative electrode, characterized in that: The solid composite alkali metal negative electrode comprises an alkali metallized three-dimensional supporting conductive skeleton, and the alkali metallized three-dimensional supporting conductive skeleton is coated with a solid polymer electrolyte.

2. The solid composite alkali metal negative electrode according to claim 1, characterized in that: The alkali metalation includes metal lithiation or metal sodiumation; Preferably, the three-dimensional supporting conductive skeleton is a three-dimensional supporting carbon-based skeleton or a three-dimensional supporting metal-based skeleton; Preferably, the three-dimensional supporting carbon-based skeleton comprises any one or a combination of at least two of carbon fiber cloth, carbon fiber paper, carbon fiber felt or an electrospun organic polymer skeleton, preferably carbon fiber cloth; Preferably, the three-dimensional supporting metal-based skeleton comprises any one of aluminum mesh, copper mesh, nickel mesh, foam nickel, foam copper or foam stainless steel mesh, or a combination of at least two thereof.

3. The solid composite alkali metal negative electrode according to claim 1 or 2, characterized in that: The solid polymer electrolyte comprises a polymer and a metal salt; Preferably, the polymer comprises any one or a combination of at least two of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polypropylene oxide, polyvinylidene chloride or a polyionic liquid, preferably a polyionic liquid; Preferably, the solid polymer electrolyte further comprises a plasticizer; Preferably, the solid polymer electrolyte further comprises an inorganic material; Preferably, based on the mass of the solid composite lithium metal negative electrode, the mass of the solid polymer electrolyte accounts for 70-90%.

4. A method for preparing a solid composite alkali metal negative electrode according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The three-dimensional supporting conductive skeleton to be treated is subjected to a pre-alkali metal treatment to obtain an alkali metal-treated three-dimensional supporting conductive skeleton; The precursor solution of the solid polymer electrolyte and the alkali metallized three-dimensional supporting conductive skeleton are compounded, and then a polymerization reaction is carried out to obtain the solid composite alkali metal negative electrode.

5. The preparation method according to claim 4, characterized in that: When the three-dimensional supporting conductive skeleton to be treated is a three-dimensional supporting carbon-based skeleton to be treated, the three-dimensional supporting carbon-based skeleton to be treated is first subjected to surface treatment and heat treatment before being subjected to pre-alkali metallization treatment; Preferably, the surface treatment includes acid washing and alkali washing; Preferably, the pickling medium of the pickling comprises any one of hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid, acetic acid, perchloric acid, hydrofluoric acid, potassium permanganate or hydrogen peroxide, or a combination of at least two thereof; Preferably, the concentration of the pickling medium for pickling is 1 to 8 mol / L, preferably 5 to 6 mol / L; Preferably, the alkaline washing medium of the alkaline washing comprises any one or a combination of at least two of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium carbonate solution or an aqueous sodium bicarbonate solution; Preferably, the concentration of the alkaline washing medium of the alkaline washing is 1 to 4 mol / L; Preferably, the atmosphere of the heat treatment includes any one of nitrogen, argon, hydrogen, carbon monoxide or carbon dioxide, or a combination of at least two thereof; Preferably, the heat treatment temperature is 300-800° C., and the insulation time is 1-6 hours.

6. The preparation method according to claim 4 or 5, characterized in that: The method of pre-alkali metallization treatment includes chemical immersion method or mechanical pressing method; Preferably, the specific steps of the chemical immersion method include: The three-dimensional supported carbon-based framework to be treated is immersed in an alkali metal organic solution; Preferably, the alkali metal organic solution comprises an alkali metal, an additive and a solvent; Preferably, the concentration of the alkali metal organic solution is 0.01 to 5 mol / L, preferably 0.5 to 1 mol / L; Preferably, the additive includes any one or a combination of at least two of biphenyl, biphenylene, benzidine, 2-fluorobiphenyl, 2-chlorobiphenyl, p-terphenyl, o-terphenyl, m-terphenyl, p-pentaphenyl, p-hexaphenyl, 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, 3-ethylbiphenyl, 4-ethylbiphenyl, 4-benzylbiphenyl, 4-butyrylbiphenyl, 4-propionylbiphenyl, naphthalene, 1-ethylnaphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 2-ethylnaphthalene, 2-phenylnaphthalene, pyrene, 1-acetylpyrene, naphtho[2,3-a]pyrene, 3,4-benzopyrene, methoxypyrene, anthracene, diphenylanthracene or ethylanthracene, preferably biphenyl; Preferably, the solvent includes any one of 1,3-dioxolane, 1,2-dimethoxypropane, dimethoxymethane, dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, isopropyl ether, methyl butyl ether, benzyl butyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, 1-butyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, trimethyltetrahydrofuran, 2,3-dichlorotetrahydrofuran, 3,4-epoxytetrahydrofuran, 2-ethoxytetrahydrofuran or 2-methoxytetrahydrofuran, or a combination of at least two thereof, preferably tetrahydrofuran; Preferably, the alkali metal comprises a metallic lithium material or a metallic sodium material; Preferably, the soaking treatment time is 1 min to 3 h, preferably 1 to 10 min; Preferably, the specific steps of the mechanical pressing method include: The base metal foil and the three-dimensional supporting metal matrix skeleton are mechanically pressed together.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The precursor solution of the solid polymer electrolyte includes polymer monomers, metal salts and solvents; Preferably, the polymer monomer comprises any one or a combination of at least two of ethylene oxide, acrylonitrile, vinylidene fluoride, methyl methacrylate, propylene oxide, vinylidene chloride or a polymerizable ionic liquid monomer, preferably a polymerizable ionic liquid monomer; Preferably, the cation of the polymerizable ionic liquid monomer includes any one or a combination of at least two of an imidazolium cation, a pyrrolidium cation, a pyridinium cation, a piperidinium cation, a quaternary ammonium cation, a quaternary phosphonium cation, a morpholinium cation or a guanidinium cation; Preferably, the anion of the polymerizable ionic liquid monomer comprises Cl - Br - ,I - OH - 、SO3 2- 、CO3 2- 、COO - 、HCO3 - PO4 3- 、BF4 - PF6 - 、FSI - TFSI - or NO3 - Any one or a combination of at least two of the following: Preferably, the metal salt is a lithium salt or a sodium salt; Preferably, in the precursor solution of the solid polymer electrolyte, the amount of the metal salt added accounts for 10% to 200% of the mass of the polymer monomer, preferably 60% to 120%; Preferably, the precursor solution of the solid polymer electrolyte further includes a plasticizer; Preferably, the plasticizer includes a small molecule organic solvent and / or a non-polymeric ionic liquid; Preferably, the small molecule organic solvent includes any one of fluoroethylene carbonate, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate or vinylene carbonate, or a combination of at least two thereof; Preferably, the amount of the plasticizer added is 1 to 50% of the mass of the polymer monomer; Preferably, the precursor solution of the solid polymer electrolyte further includes an inorganic material; Preferably, the inorganic material comprises any one of SiO2, TiO2, Al2O3, h-BN, LLZO, LATP, LGAP, LLZTO, GO or MOF, or a combination of at least two thereof; Preferably, the particle size of the inorganic material ranges from 10 nm to 50 μm, preferably from 10 to 500 nm; Preferably, the added amount of the inorganic material accounts for 1 to 50% of the mass of the polymer monomer.

8. The preparation method according to claim 7, characterized in that: The compounding method includes an in-situ melt infusion method or a dripping method; Preferably, the polymerization reaction comprises thermally initiated polymerization or photo-initiated polymerization; Preferably, during the thermal polymerization, the amount of thermal initiator used is 0.1 to 3% of the mass of the polymer monomer; Preferably, the reaction temperature of the thermally initiated polymerization is -10 to 180°C; Preferably, during the photoinitiated polymerization, the amount of the photoinitiator used is 0.1 to 3% of the mass of the polymer monomer.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The preparation method comprises the following steps: (1) The three-dimensional supported carbon-based skeleton to be treated is subjected to surface treatment, heat treatment, cleaning and drying in sequence to obtain a three-dimensional supported carbon-based skeleton having alkali metal affinity; wherein the surface treatment comprises acid washing and alkali washing in sequence, the acid washing temperature is 20 to 80° C., the acid washing process is accompanied by ultrasound, the acid washing time is 1 to 90 min, the concentration of the acid washing medium of the acid washing is 1 to 8 mol / L, and the concentration of the alkali washing medium of the alkali washing is 1 to 4 mol / L; the heat treatment temperature is 300 to 800° C., the heat preservation time is 1 to 6 h, and the heating rate is 1 to 10° C. / min; (2) placing the three-dimensional carbon-based support skeleton with alkali metal affinity in an alkali metal organic solution for 1 min to 3 h of immersion treatment, then washing with a cleaning solvent and drying to obtain an alkali metallized three-dimensional carbon-based support skeleton; wherein the alkali metal organic solution includes an alkali metal, an additive and a solvent, and the concentration of the alkali metal organic solution is 0.01 to 5 mol / L; (3) mixing polymer monomers, metal salts, solvents, and plasticizers / inorganic materials to obtain a precursor solution of a solid polymer electrolyte; wherein the amount of the metal salt added to the precursor solution of the solid polymer electrolyte is 10% to 200% of the mass of the polymer monomers, and the amount of the plasticizer / inorganic material added to the precursor solution is 1% to 50% of the mass of the polymer monomers; An in-situ melt infusion method is used to compound a precursor solution of a solid polymer electrolyte and an alkali metallized three-dimensional supporting carbon-based skeleton. After the solvent is volatilized, a polymerization reaction is carried out to obtain a solid composite alkali metal negative electrode. The polymerization reaction method includes thermal initiation polymerization or photoinitiation polymerization. During the thermal initiation polymerization, the amount of the thermal initiator used is 0.1-3% of the mass of the polymer monomer, and the reaction temperature of the thermal initiation polymerization is -10-180°C. During the photoinitiation polymerization, the amount of the photoinitiator used is 0.1-3% of the mass of the polymer monomer, the ultraviolet light wavelength of the photoinitiator is 200-400nm, and the time of the photoinitiation polymerization is 0.01-3h.

10. A secondary battery, characterized in that: The secondary battery comprises the solid composite alkali metal negative electrode as described in any one of claims 1 to 3, or comprises the solid composite alkali metal negative electrode prepared by the preparation method as described in any one of claims 4 to 9.

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