Anode-free lithium metal battery, manufacturing method therefor and use thereof

Abstract

An anode-free lithium metal battery, a manufacturing method therefor and a use thereof. The anode-free lithium metal battery comprises: a cathode, the cathode comprising a cathode current collector and a cathode active material layer; an anode current collector, a lithium seed implantation layer being formed on the surface of the anode current collector corresponding to the cathode; an electrolyte; and a separator. By using the in-situ seed implantation technology, an ultra-thin lithium seed implantation layer is constructed in situ on an anode current collector before the first charging and discharging of a battery completing electrolyte injection and packaging, thereby solving the problem of non-uniform nucleation of metal lithium on the anode current collector, forming in situ, on the current collector after subsequent charging, a dense and uniform lithium deposition layer having strong bonding strength to the current collector, and significantly prolonging the cycle life while maintaining high energy density; and the use of a lithium supplementing additive and a fluorinated amide electrolyte realizes longer cycle life.

Description

A negative electrode-free lithium metal battery and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of negative electrode-free lithium metal batteries, and in particular relates to a negative electrode-free lithium metal battery with high energy density and long cycle life, and a preparation method and application thereof. Background Art

[0002] Electric vehicles and portable electronic devices have increasing requirements for lithium battery performance and cost, and there is an urgent need for batteries with higher energy density and lower cost. The energy density of traditional lithium-ion batteries based on lithium-ion intercalation chemistry is approaching its limit, making it difficult to meet the development needs of various emerging fields. Lithium metal batteries have the lowest electrode potential (-3.04V vs. SHE) and the highest theoretical specific capacity (3860mAh g -1 ), which can significantly improve the energy density of batteries and has therefore been widely studied.

[0003] However, currently commercial lithium foil is generally produced by mechanical rolling, with a thickness of 50-100 μm (10-20 mAh cm -2 ), the negative electrode / positive electrode capacity ratio (i.e., N / P ratio) of the lithium metal full battery constructed in this way is large, which not only affects the energy density of the battery, but also greatly increases the production cost due to the use of a large amount of chemically active metallic lithium, and causes serious safety hazards. Therefore, practical lithium metal batteries need to use ultra-thin metal lithium foil (≤20μm) to overcome the above problems. Unfortunately, due to the viscosity of metallic lithium and the unrestricted dislocation movement during extrusion deformation, the manufacture of metal lithium foil with a thickness of less than 20μm faces the challenges of poor mechanical strength and difficult production and processing. Recently, Yi Cui et al. used molten lithium to inject graphene oxide host to prepare 0.5-20μm ultra-thin metal lithium foil (Nat.Energy 2021,6,790-798), but this type of preparation process has the problems of difficulty in mass production, low efficiency and high cost. Similarly, the preparation of ultra-thin metal lithium foil by electrochemical deposition or vacuum evaporation also has the above problems. Therefore, the cheap and large-scale production of ultra-thin lithium foil is extremely challenging, which will seriously weaken the potential commercial advantages of lithium metal batteries.

[0004] Compared to lithium metal batteries, anode-free lithium metal batteries completely eliminate the active material on the anode side of their structure, retaining only the current collector. This minimizes battery weight and volume, maximizes battery energy density, and eliminates the need for handling active lithium metal during manufacturing, reducing production costs and safety risks. Consequently, they offer significant advantages in high specific energy and low cost. Previous studies have shown that for zero-excess-lithium anode-free lithium batteries, the electrodeposition / stripping behavior of the limited lithium source on the current collector is a key factor in determining the cycle life of anode-free lithium batteries. Due to its high conductivity, high stability, ease of processing, and low cost, copper foil (Cu) remains an attractive alternative to anode current collectors in large-scale lithium batteries. However, the inherent lithium-phobic nature of the Cu current collector leads to uneven nucleation and growth of lithium metal on the Cu current collector surface, resulting in irreversible consumption of active lithium. To improve the reversible and uniform deposition / stripping of lithium metal on the Cu current collector and extend the cycle life of anode-free lithium metal batteries, extensive research efforts have focused on current collector coating modification or current collector material replacement. Liumin Suo et al. designed a liquid metal coating modified Cu current collector and combined it with a high-concentration electrolyte (6MLiFSI / DME), which resulted in a 0.12Ah, 420Wh / kg negative electrode-free soft-pack lithium metal battery (Cu||NCM811) with a capacity retention rate of 84% after 50 cycles (Adv.Energy Mater.2021,2003709). In the study of current collector replacement, Hee-Tak Kim et al. reported a three-dimensional carbon current collector with a multi-vacancy defect structure, which resulted in a button-type negative electrode-free lithium metal battery (Cu||NCM811) with a capacity retention rate of 80% after 60 cycles (Nat.Commun.2021,12,5537). However, the manufacturing processes of these strategies are relatively complicated, which increases the manufacturing cost, and the inevitable introduction of inactive substances reduces the energy density of the system. There is also the problem of unstable modification effect, which is not conducive to large-scale industrial production.

[0005] It can be seen that under the premise of maintaining the high energy density and low cost advantages of negative electrode-free lithium metal batteries, how to inhibit the irreversible consumption caused by the deposition / stripping process of metallic lithium on the surface of the copper current collector, improve the density of the deposited lithium, and extend the cycle life of the negative electrode-free lithium metal battery is a key problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The present invention utilizes in-situ crystal planting technology to construct an ultra-thin lithium crystal layer in situ on the negative electrode current collector before the first charge and discharge (formation process) after the battery is filled and packaged, thereby solving the problem of uneven nucleation of metallic lithium on the negative electrode current collector. After subsequent charging, a dense and uniform lithium deposition layer with strong binding force to the current collector can be formed in situ on the current collector, significantly improving the cycle life while maintaining high energy density; combined with lithium supplement additives and fluorinated amide electrolytes, it has a longer cycle life.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] One aspect of the present invention provides a negative electrode-free lithium metal battery.

[0010] Another aspect of the present invention provides a method for preparing the negative electrode-free lithium metal battery.

[0011] Another aspect of the present invention provides use of the negative electrode-free lithium metal battery in electronic devices, smart grids or electric vehicles.

[0012] According to one aspect of the present invention, there is provided a negative electrode-free lithium metal battery comprising:

[0013] A positive electrode, comprising a positive electrode current collector and a positive electrode active material layer;

[0014] negative electrode current collector,

[0015] A lithium plant crystal layer is formed on the surface of the negative electrode current collector corresponding to the positive electrode, wherein the lithium plant crystal layer is composed of metallic lithium deposited in situ by electrochemical means;

[0016] electrolyte; and

[0017] diaphragm.

[0018] 1. Negative electrode current collector

[0019] In the present invention, the negative electrode current collector does not contain negative electrode active materials, so it is called no negative electrode.

[0020] The negative electrode current collector includes a metal current collector, such as one selected from copper, nickel, cobalt, titanium, and iron, or alloys of two or more thereof, preferably copper foil; a non-metallic current collector, such as one or more selected from carbon fiber cloth, carbon fiber paper, graphite paper, and conductive organic polymers, preferably graphite paper; and a metal-polymer composite current collector, such as a three-layer structure with a polymer film as the middle layer and metal plating as the upper and lower layers. The polymer can be one or more selected from polycarbonate, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polypropylene, polyethylene, polyvinylidene chloride, polybenzimidazole, ethylene-vinyl acetate copolymer, polyimide, polyimide-triphenyl phosphate copolymer, and polyurethane, preferably flame-retardant polyimide-triphenyl phosphate copolymer. The negative electrode current collector is preferably a composite current collector of copper and polyimide-triphenyl phosphate copolymer, such as a copper-plated composite current collector of polyimide-triphenyl phosphate. The thickness of the negative electrode current collector may be 1-100 μm, preferably 1-10 μm.

[0021] The present invention also includes a coating formed on at least one side of the negative electrode current collector. The position of the coating and the lithium plant crystal layer is not particularly limited. The coating can be located on the lithium plant crystal layer, or between the negative electrode current collector and the lithium plant crystal layer, or form a composite layer with the lithium plant crystal layer. The function of the coating is to promote the dense deposition and growth of lithium metal on its surface, and / or inhibit the corrosion of the deposited lithium metal. The coating can be a metal-containing indium, cobalt, germanium, aluminum, tin, gold, silver, zinc, magnesium, silicon, bismuth, palladium, platinum or an alloy of two or more thereof, or a non-metal-containing acetylene black, Ketjen black, carbon black, graphite, graphene, conductive polymer, artificial interface film (artificial SEI), or a mixture of the above metals and non-metals.

[0022] 2. Lithium Plant Crystal Layer

[0023] In the present invention, an ultra-thin lithium phytoplankton layer is formed on the negative electrode current collector corresponding to the positive electrode, wherein the thickness of the lithium phytoplankton layer is 5-2000 nm, preferably 20-1000 nm, and more preferably 50-500 nm.

[0024] The lithium crystal layer of the present invention is formed by electrochemical in-situ deposition (in-situ crystal deposition) of a negative electrode-free lithium metal battery, and the electrochemical in-situ deposition includes the following steps:

[0025] The negative electrode-free lithium metal battery is subjected to constant current charging and / or constant voltage charging after liquid injection and packaging and before formation. The nucleation overpotential of the metallic lithium (relative to the standard potential of metallic lithium) is controlled to be 0.1 to 2 V, preferably 0.6 to 1.5 V, and especially 1 V during the charging process.

[0026] In some embodiments, the constant current charging process is: charging at a constant charging rate C1 at a temperature T1 for a charging time of t1;

[0027] The constant voltage charging process is: charging at a constant charging voltage V1 at temperature T2, and the charging capacity is R1.

[0028] Among them, C1 is 0.3 to 10.0C, preferably 0.5 to 5C, more preferably 0.8 to 3C, and especially 1C.

[0029] t1 is 0.1 to 3600 s, preferably 1 to 100 s, more preferably 10 to 60 s, and particularly 36 s.

[0030] T1 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, and particularly 0°C.

[0031] V1 is 3.2 to 6 V, preferably 3.8 to 5 V, more preferably 3.8 to 4.2 V, and particularly 4.2 V.

[0032] R1 is 0.01~1mAh / cm 2 , preferably 0.02~0.5mAh / cm 2 , more preferably 0.02 to 0.2 mAh / cm 2 , especially 0.056mAh / cm 2 ,

[0033] T2 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, and particularly 25°C.

[0034] The negative electrode-free lithium metal battery is charged to electrochemically deposit metallic lithium in situ on the negative electrode current collector to form a lithium plant crystal layer. The parameters of constant current charging and / or constant voltage charging are selected to regulate the nucleation overpotential (P) of metallic lithium on the negative electrode current collector, wherein P is 0.1 to 2 V relative to the standard potential of metallic lithium to obtain a lithium plant crystal layer with high coverage. The present invention can deposit (charge) a capacity of 0.02 to 0.2 mAh / cm at a lower rate. 2 To achieve a high coverage rate, preferably the ratio (coverage rate) of metallic lithium (thinner lithium core) covering the surface of the negative electrode current collector is greater than 80%, further greater than 90%, or even close to 100%. The calculation formula for this ratio (coverage rate) is as follows:

[0035] The ratio of metal lithium covering the surface of the negative electrode current collector (%) = S1 / S×100%, where S is the area of ​​the negative electrode current collector and S1 is the projected area of ​​the metal lithium deposited within the area of ​​S on the negative electrode current collector.

[0036] The lithium vegetative layer formed by the in-situ vegetative method can achieve a close bond with the negative electrode current collector, improving the density of the metal lithium deposition during the subsequent charge and discharge process, and extending the cycle life of the negative electrode-free lithium metal battery. After the battery has been cycled for a long time, a lithium deposition layer is formed on the lithium vegetative layer, which has a strong bond with the current collector.

[0037] The in-situ crystal planting process described in the present invention is different from the conventional lithium-ion battery formation. Conventional formation regulates the electrolyte-electrode interface reaction by optimizing the charge and discharge parameters to obtain a high-quality solid electrolyte interface film (SEI / CEI) and discharge the gas products generated by the electrolyte-electrode interface reaction.

[0038] In practical applications, the in-situ crystal planting process can be combined with the formation step without any time interval, but the in-situ crystal planting process still takes precedence over the formation step.

[0039] 3. Positive electrode

[0040] In the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector.

[0041] There are no particular limitations on the positive electrode current collector and it can be a conventional positive electrode current collector for lithium batteries, including metal current collectors such as one selected from aluminum, titanium, nickel, and iron or their alloys, preferably aluminum foil; non-metallic current collectors such as one or more selected from carbon fiber cloth, carbon fiber paper, graphite paper, and conductive organic polymers, preferably carbon fiber paper; and metal-polymer composite current collectors, such as those having a three-layer structure with a polymer film as the middle layer and metal coatings as the upper and lower layers, wherein the polymer can be one or more selected from polycarbonate, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polypropylene, polyethylene, polyvinylidene chloride, polybenzimidazole, ethylene-vinyl acetate copolymer, polyimide, polyimide-triphenyl phosphate copolymer, and polyurethane, preferably flame-retardant polyimide-triphenyl phosphate copolymer. The positive electrode current collector is preferably a composite current collector of aluminum and polyimide-triphenyl phosphate copolymer, such as an aluminum-plated composite current collector of polyimide-triphenyl phosphate copolymer. The composite current collector can effectively enhance battery safety, reduce raw material costs, and increase battery energy density. The thickness of the positive electrode current collector can be 1-100 μm, preferably 1-20 μm.

[0042] The positive electrode active material layer of the present invention comprises a positive electrode active material and a lithium replenishing additive. Furthermore, the positive electrode active material layer may also comprise: a conductive material for enabling smooth electron movement in the positive electrode; a binder for increasing the bonding strength between the positive electrode active materials or between the positive electrode active materials and the positive electrode current collector; the positive electrode active material; and the lithium replenishing additive.

[0043] There is no particular limitation on the positive electrode active material, and it can be a positive electrode active material conventionally used in lithium batteries, including ternary nickel cobalt lithium manganese oxide positive electrode materials, such as Li[Ni 0.5 Mn 0.2 Co 0.3 ]O2(NCM523), Li[Ni 0.6 Mn 0.2 Co 0.2 ]O2(NCM622), Li[Ni 0.8 Mn 0.1 Co 0.1 ]O2(NCM811), Li[Ni 0.9 Mn 0.05 Co 0.05 ]O2 (NCM955), one or more of lithium-rich manganese-based positive electrode material (LMR), lithium nickel manganese oxide positive electrode material (LNMO), lithium iron phosphate positive electrode material (LiFePO4), lithium manganate positive electrode material (LiMn2O4), lithium manganese iron phosphate positive electrode material (LMFP), lithium cobalt oxide positive electrode material (LiCoO2), and lithium sulfide positive electrode material (Li2S), but not limited thereto. Preferably, the positive electrode adopts a ternary nickel cobalt manganese oxide positive electrode material (NCM523, NCM622, NCM811, NCM955) with different nickel contents, in particular NCM811.

[0044] Based on the total weight of the positive electrode active material layer, the positive electrode active material may be contained in an amount of 80% to 99% by weight. If the amount of the positive electrode active material is less than this range, the energy density of the battery will be reduced. If the amount of the positive electrode active material exceeds this range, the content of the lithium supplement additive is too low, resulting in a minimal improvement in the battery cycle life.

[0045] The lithium-supplementing additive is a lithium-containing compound with the ability to release lithium ions and an irreversible capacity greater than 50%, including binary lithium-containing compounds such as Li2O, Li2O2, Li3N, Li2S, Li2C2O4, etc., preferably Li2C2O4; lithium-rich compounds such as Li2Ni 1-x M x O2 (where 0≤x<1, and M is at least one selected from Mn, Fe, Co, Cu, Zn, Mg, Cd), Li5Fe 1-x N x O4 (wherein 0≤x<1, and N is at least one selected from Mn, Ni, Co, Cu, Zn, Mg, Cd), etc., preferably the lithium supplement additive is one or both of Li2NiO2 and Li5FeO4.

[0046] Based on the total weight of the positive electrode active material layer, the lithium supplement additive may be present in an amount of 0.5% to 20% by weight, preferably 2% to 10% by weight. Similarly, if the amount of the lithium supplement additive is less than the above range, the improvement in battery cycle life may be insignificant. If the amount of the lithium supplement additive exceeds the above range, not only will the energy density be compromised, but other battery properties, such as cycle life, power, and safety performance, may also deteriorate.

[0047] In addition, the conductive material can be a carbon material such as carbon black, acetylene black, Ketjen black, carbon nanotubes; or a conductive polymer such as polyaniline, polythiophene, polyacetylene, and polypyrrole. The conductive material can be contained in an amount of 0.1 wt% to 5 wt% based on the total weight of the positive electrode active material layer.

[0048] In addition, the binder can be polyvinyl acetate, polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, alkylated polyethylene oxide, cross-linked polyethylene oxide, polyvinyl ether, polymethyl methacrylate, polyvinylidene fluoride, polyhexafluoropropylene and a copolymer of polyvinylidene fluoride (product name: Kynar), polyethyl acrylate, polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinyl pyridine, polystyrene and derivatives, blends and copolymers thereof. Based on the total weight of the positive electrode active material layer, the binder can preferably be contained in an amount of 0.1 wt% to 5 wt%.

[0049] 4. Electrolyte

[0050] In the present invention, the electrolyte contains at least one lithium salt and an organic solvent. In addition, the electrolyte may further contain functional additives (i.e., electrolyte additives) and / or flame retardants or inert diluents as needed, thereby reducing the flammability or cost of the electrolyte.

[0051] There is no particular restriction on the choice of electrolyte, and conventional electrolytes for negative electrode-free lithium metal batteries can be selected, such as local high-concentration electrolytes, high-concentration electrolytes, weakly solvated electrolytes, etc.

[0052] In some embodiments, the electrolyte comprises at least one boron-containing lithium salt and a fluorinated amide compound. The electrolyte uses the boron-containing lithium salt as a main salt and the fluorinated amide compound as an organic solvent.

[0053] The boron-containing lithium salt can be one or more selected from lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium tetrafluoroborate (LiBF4), lithium fluoroalkoxyborate, lithium fluoroalkoxyfluoroborate, lithium fluoroalkoxybis(fluoroborate), and lithium fluoroalkoxytrifluoroborate, preferably lithium difluorooxalatoborate (LiDFOB).

[0054] The fluorinated amide compound can be one or more selected from N,N-dimethyltrifluoroacetamide, N-methoxy-N-methyltrifluoroacetamide, N-methyltrifluoroacetamide, N,N-diethyltrifluoroacetamide, N-(trifluoromethanesulfonyl)trifluoroacetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, N-methyl-N-(trimethylsilyl)trifluoroacetamide, bis(trimethylsilyl)trifluoroacetamide, N-methyltrimethylsilyltrifluoroacetamide, N-methylbis(trifluoroacetyl)amide, trifluoroacetamide, and bistrifluoroacetamide, preferably N,N-dimethyltrifluoroacetamide.

[0055] Based on the total weight of the electrolyte, the electrolyte may contain 5% to 50% by weight (e.g., 10% to 35% by weight) of a boron-containing lithium salt. If the content of the lithium salt is less than 5% by weight, the ionic conductivity of the electrolyte will be reduced, affecting the deposition of metallic lithium. If the content of the lithium salt exceeds 50% by weight, the cost and viscosity of the electrolyte will be increased, and the wettability to the electrode and diaphragm will be reduced.

[0056] In some embodiments, the electrolyte comprises lithium difluorooxalatoborate (LiDFOB) and N,N-dimethyltrifluoroacetamide, and the molar ratio of lithium difluorooxalatoborate (LiDFOB) to N,N-dimethyltrifluoroacetamide is 1:5.

[0057] The functional additives may be additives conventionally used in lithium battery electrolytes in the art, such as salts or organic solvents, such as tris(2,2,2-trifluoroethyl)phosphite (TTFEP), 1,3,6-hexanetrinitrile (HTCN), tris(trimethylsilyl)borate (TMSB), tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)phosphite (TMSPi), hexamethyldisilazane (HMDS), 1,3-propylene sultone (PRS), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), bis(2,2,2-trifluoroethyl)carbonate (TFEC), ), fluoroethyl methyl carbonate (FEMC), vinylene carbonate (VC), propylene sulfite (PS), trifluoromethyl ethylene carbonate (TFPC), vinyl sulfate (DTD), vinyl sulfite (ES), lithium difluorophosphate (LiDFP), lithium difluorobis(oxalatophosphate) (LiDODFP), lithium tetrafluorooxalatophosphate (LiTFOP), lithium nitrate (LiNO3), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiOTf), lithium bis(fluorosulfonyl imide) (LiFSI), lithium bis(trifluoromethylsulfonyl imide) (LiTFSI), one or more thereof.

[0058] The functional additives can be added and appropriately used in an amount determined by those skilled in the art according to the desired function. For example, the electrolyte can contain 0.1 wt% to 10 wt%, preferably 0.5 wt% to 5 wt%, of the functional additives based on the total weight of the electrolyte.

[0059] The flame retardant or inert diluent can be a flame retardant or inert diluent conventionally used in the field for lithium battery electrolytes, for example, can be selected from any one or more of halogenated ethers, halogenated esters, hydrocarbons, halogenated hydrocarbons, aromatic compounds, nitrogen-containing compound reagents and their derivatives, such as 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,2-bis(1,1,2,2-tetrafluoro

[0065] The present invention also includes, but is not limited to, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, 1,3-bis(1,1,2,2-tetrafluoroethoxy)benzene, 1-(1,1,2,2-tetrafluoroethoxy)propane, 2-methyl-1-(1,1,2,2-tetrafluoroethoxy)propane, 1,3-bis(1,1,2,2-tetrafluoroethoxy)propane, 2,2,3,3-tetrafluoro-1-methoxypropane, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tributyl phosphate, trifluoroethyl phosphate, hexafluorocyclotriphosphazene, pentafluoroethoxycyclotriphosphazene, trimethoxytrifluorocyclotriphosphazene, m-xylene, isopropylbenzene, mesitylene, chlorobenzene, o-fluorotoluene, m-fluorotoluene, p-fluorotoluene, fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, anisole, carbon tetrachloride, cyclohexane, nitroethane, and nitropropane. Preferably, the flame retardant or inert diluent is selected from 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, and m-fluorotoluene.

[0060] The flame retardant or inert diluent can be added and the appropriate amount can be determined by those skilled in the art according to the desired function. For example, based on the total amount of the electrolyte, the flame retardant or inert diluent can be contained in an amount of 5% to 90% by weight, preferably 20% to 50% by weight.

[0061] 5. Diaphragm

[0062] In the present invention, the diaphragm is a physical diaphragm having the function of physically separating the electrodes, and can be used without particular limitation, as long as it is used as a diaphragm in a conventional lithium secondary battery, and in particular, a diaphragm having low resistance to ion migration in the electrolyte and having excellent electrolyte impregnation ability is preferred. Specifically, the diaphragm can be a porous polymer film, for example, a porous polymer film made of one of a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer, or a composite porous polymer film made of two or more, which can be used alone or in the form of its laminate, or can be a porous non-woven fabric, for example, a non-woven fabric made of glass fiber with a high melting point, polyethylene terephthalate fiber, etc. The diaphragm can contain a surface functional coating material, such as a ceramic coating, a solid electrolyte coating or a composite coating of two or more, but is not limited thereto. The ceramics may include: aluminum oxide (Al2O3), magnesium oxide (MgO), titanium dioxide (TiO2), zirconium dioxide (ZrO2), silicon dioxide (SiO2), barium titanate (BaTiO3), etc.; the solid electrolyte may include: lithium phosphorus oxynitride (LiPON), lithium zinc germanium oxide (LISICON), lithium germanium phosphorus sulfur (LGPS), lithium phosphorus sulfur chloride (LPSCl), lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), halide solid electrolyte (Li x MCl6, M is a metal element), polyethylene oxide (PEO), polysiloxane (PS), polypropylene carbonate (PPC), polyacrylonitrile (PAN), polyacrylate (PBA), polymethyl methacrylate (PMMA) and polyvinylidene fluoride (PVDF), etc.

[0063] In addition to the positive electrode, negative electrode, separator and electrolyte described above, the battery of the present invention may also include other structures such as a chip, a capacitor, a casing and the like as needed.

[0064] The anode-free lithium metal battery according to the present invention is a high energy density, long cycle life anode-free lithium metal battery. Here, "high energy density, long cycle life" means that the anode-free lithium metal battery according to the present invention maintains or maintains the high energy density of conventional anode-free lithium metal batteries (>350Wh / kg, even >400Wh / kg, >450Wh / kg and >500Wh / kg), while further significantly improving its cycle life.

[0065] According to another aspect of the present invention, a method for preparing the negative electrode-free lithium metal battery is provided, comprising the following steps:

[0066] Assembling a cathode, an anode current collector, a separator and an electrolyte into an anode-free lithium metal battery;

[0067] The negative electrode-free lithium metal battery is subjected to constant current charging and / or constant voltage charging after liquid injection and packaging and before formation. During the charging process, the nucleation overpotential of the metallic lithium (relative to the standard potential of metallic lithium) is controlled to be 0.1 to 2V, preferably 0.6 to 1.5V, to obtain the negative electrode-free lithium metal battery including the negative electrode current collector forming the lithium phytoplankton layer;

[0068] In some embodiments, the constant current charging process is: charging at a constant charging rate C1 at a temperature T1 for a charging time of t1;

[0069] The constant voltage charging process is: charging at a constant charging voltage V1 at temperature T2, and the charging capacity is R1.

[0070] Among them, C1 is 0.3 to 10.0C, preferably 0.5 to 5C, more preferably 0.8 to 3C, and especially 1C.

[0071] t1 is 0.1 to 3600 s, preferably 1 to 100 s, more preferably 10 to 60 s, and particularly 36 s.

[0072] T1 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, and particularly 0°C.

[0073] V1 is 3.2 to 6 V, preferably 3.8 to 5 V, more preferably 3.8 to 4.2 V, and particularly 4.2 V.

[0074] R1 is 0.01~1mAh / cm 2 , preferably 0.02~0.5mAh / cm 2 , more preferably 0.02 to 0.2 mAh / cm 2 , especially 0.056mAh / cm 2 ,

[0075] T2 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, and particularly 25°C.

[0076] The positive electrode can be prepared according to a conventional method, and specifically, a positive electrode active material layer-forming composition prepared by mixing a positive electrode active material, a lithium supplement additive, a conductive material, and a binder in an organic solvent or water can be coated on a positive electrode current collector, followed by drying and optionally rolling. In this case, the organic solvent can evenly disperse the positive electrode active material, the lithium supplement additive, the binder, and the conductive material, and can be easily evaporated. Specifically, N-methylpyrrolidone, dimethylformamide, ethylene glycol dimethyl ether, acetonitrile, etc. can be used as the organic solvent.

[0077] According to another aspect of the present invention, there is provided use of the negative electrode-free lithium metal battery in electronic devices, smart grids or electric vehicles.

[0078] As used herein, the terms "comprises," "includes," "has," "contains" or any other similar terms are open conjunctions that are intended to cover non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or article. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "comprises," "includes," "has," and "contains" should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of."

[0079] Throughout this document, all features or conditions defined as numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges, particularly integer values. For example, a description of a range "1 to 8" should be considered to specifically disclose all possible subranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, and so forth, particularly those defined by all integer values, and should be considered to specifically disclose individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, and 8. Unless otherwise indicated, the foregoing interpretation applies to all of the present disclosure, regardless of whether the ranges are comprehensive or not.

[0080] If a quantity or other value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and any lower limit or preferred value of the range are specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0081] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0082] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the spirit and scope of protection of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the scope of protection of the present invention. Beneficial effects

[0083] (1) The present invention electrochemically forms a dense ultra-thin lithium phytocrystalline layer composed of metallic lithium in situ on the negative electrode current collector, thereby obtaining more physical contact surfaces with the current collector and inducing high-quality growth of the lithium deposition layer formed by subsequent conventional charging, thereby forming close contact with the substrate. Without affecting the energy density and cost, the present invention can significantly improve the cycle stability of negative electrode-free lithium metal batteries. Further combination with lithium supplementation additives and fluorinated amide electrolytes can make the effect more significant.

[0084] (2) The in-situ crystal planting method provided by the present invention does not reduce energy density or increase cost, is easy to operate, and is suitable for large-scale production applications; it has wide adaptability to various electrolytes; and it is sustainable. Even after the battery has been cycled many times, the lithium crystals formed by in-situ crystal planting can still remain on the surface of the current collector;

[0085] (3) The present invention combines an in-situ formed lithium plant layer, a lithium supplement additive, and a fluorinated amide electrolyte with a negative electrode-free lithium metal battery system. Under actual test conditions, the energy density is 533Wh kg -1 The (100% DoD) Cu||NCM811 anode-free soft-pack lithium metal battery has a cycle life of 232 times and an energy density of 426Wh kg -1 The cycle life of the Cu||NCM811 anode-free soft-pack lithium metal battery (80% DoD) reaches 725 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 shows the lithium||copper button-type batteries assembled in Comparative Example 1 and Example 1 after the lithium deposition layer on the Cu foil is bent after 10 cycles, where (a) is the bending condition of Comparative Example 1 and (b) is the bending condition of Example 1.

[0087] Figure 2 shows the SEM morphology of the lithium deposited layer close to the Cu foil side of the lithium||copper button cells assembled in Comparative Example 1 and Example 1 after 10 cycles (bottom view of the lithium deposited layer), wherein (a) is the SEM morphology of the lithium deposited layer close to the Cu foil side of Comparative Example 1, and (b) is the SEM morphology of the lithium deposited layer close to the Cu foil side of Example 1.

[0088] Figure 3 shows the image of the lithium crystal layer formed in situ on the current collector of the negative electrode-free soft-pack lithium metal battery assembled in Example 2 after undergoing in-situ crystal planting treatment and the image of the lithium crystal layer on the current collector after undergoing 10 cycles, where (a) is the image of the lithium crystal layer after the in-situ crystal planting treatment, and (b) is the image of the lithium crystal layer after 10 cycles.

[0089] FIG4 shows the time-voltage curves corresponding to the in-situ crystal planting process of the negative electrode-free soft-pack lithium metal batteries assembled in Example 2, Example 3, Example 4, Example 5 and Comparative Example 2.

[0090] FIG5 shows images of the lithium crystal layer on the current collector after in-situ crystal planting treatment of the negative electrode-free soft-pack lithium metal batteries assembled in Example 2, Example 3, Example 4 and Example 5. DETAILED DESCRIPTION

[0091] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0092] Preparation Example:

[0093] Preparation of lithium||copper (Li||Cu) button battery:

[0094] In an argon-filled glove box, the positive electrode shell, working electrode (copper foil), diaphragm, electrolyte, counter electrode (metal lithium sheet), gasket, shrapnel, and negative electrode shell are assembled in this order. Then, the button battery is placed with the negative electrode side facing up on the button battery sealing machine mold and pressed to complete the preparation of the lithium||copper button battery.

[0095] The counter electrode and reference electrode were 200 μm thick lithium metal sheets purchased from Zhongneng Lithium Industry;

[0096] The working electrode was 20 μm thick copper foil purchased from Shenzhen Kejing;

[0097] The separator was a 12 μm thick polyethylene (PE) separator purchased from Celgard.

[0098] Preparation of negative electrode-free soft-pack lithium metal battery:

[0099] The assembly is carried out in the order of lamination, tab welding, top and side sealing, liquid injection and packaging. The liquid injection and packaging are carried out in a glove box and a vacuum pre-sealing machine is used for packaging.

[0100] Preparation of positive electrode sheet: The positive electrode active material, lithium supplement additive, binder and conductive agent are made into slurry, coated on both sides of 4μm thick aluminum foil, and cut to size.

[0101] The negative electrode current collector was 4 μm thick copper foil purchased from Shenzhen Kejing;

[0102] The separator was a 12 μm thick polyethylene (PE) separator purchased from Celgard;

[0103] Aluminum tabs, nickel tabs and 113 μm thick aluminum-plastic film were purchased from Shenzhen Kejing.

[0104] Preparation of electrolyte:

[0105] The local high concentration electrolyte is made of lithium bis(fluorosulfonyl)imide (LiFSI): ethylene glycol dimethyl ether (DME): 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a molar ratio of 1.0:1.2:3.0. Specifically, 1.50g of lithium bis(fluorosulfonyl)imide (LiFSI) was dissolved in 1.0mL of ethylene glycol dimethyl ether (DME) solvent to obtain a high concentration electrolyte. Then, 1.0mL of the high concentration electrolyte was mixed with 1.93mL of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) solvent to obtain a local high concentration electrolyte, in which the mass proportion of lithium salt was 19.0wt%. This local high concentration electrolyte is the local high concentration electrolyte with the best performance reported so far.

[0106] The fluorinated amide electrolyte is prepared from lithium difluorooxalatoborate (LiDFOB) and N,N-dimethyltrifluoroacetamide in a molar ratio of 1:5. Specifically, 0.25 g of lithium difluorooxalatoborate (LiDFOB) is dissolved in 1.0 mL of N,N-dimethyltrifluoroacetamide solvent to obtain a fluorinated amide electrolyte, in which the mass proportion of lithium salt is 17.2 wt%.

[0107] Constant current charge and discharge test of non-anode soft-pack lithium metal battery: The test was conducted with the Xinwei battery test system at a constant current within the set voltage range, where 1C = 5.6 mA cm -2 The cycle life of the battery is defined as 80% capacity retention based on the initial discharge capacity at 0.2C.

[0108] Test method for the ratio (coverage) of metallic lithium covering the surface of the negative electrode current collector:

[0109] After the negative electrode current collector was photographed by scanning electron microscope after in-situ crystallization, 5 groups of 2×2 μm test areas were randomly selected and the total projected area of ​​all metal lithium on the current collector in the 5 groups of test areas was measured (A, μm 2 ), calculate the average value (average coverage) of the 5 groups of data according to the following formula.

[0110] Example 1: Lithium||Copper (Li||Cu) Button Cell

[0111] Metallic lithium was used as the counter electrode and reference electrode, copper foil was used as the working electrode, and polyethylene (PE) was used as the separator. 70 μL of local high-concentration electrolyte was injected into the button cell in an argon-filled glove box. In-situ crystallization was performed before the first charge-discharge cycle: at 0°C, 5 mA cm -2 The battery was discharged at a current density of 1000 nm for 36 s, and a lithium-planted crystal layer was formed on the copper foil current collector.

[0112] Comparative Example 1: Lithium||Copper (Li||Cu) Button Battery

[0113] The difference between the comparative example and Example 1 is that the in-situ crystal planting process before the first charge and discharge cycle is eliminated.

[0114] The batteries obtained in Comparative Example 1 and Example 1 were each subjected to the following operations:

[0115] First, 0.1 mA cm -2 The current density of the copper foil electrodeposition was 5 mAh cm -2 of metallic lithium, then at 0.5 mA cm -2 ,3mAh cm -2 After 10 stripping / deposition cycles under the conditions of , the 10th battery sample was collected and the morphology of the lithium deposition layer of the Cu foil was observed after disassembly.

[0116] Figures 1 (a) and (b) show the morphology of the lithium deposit layer on the Cu foil, observed using a scanning electron microscope (SEM), after disassembly of the batteries for Comparative Example 1 and Example 1 after 10 cycles. Bending the Cu foil revealed that the lithium deposit layer (50.3 μm thick) on the Cu foil without in-situ crystallization (Comparative Example 1) immediately cracked and fell off the current collector after just one small-angle bend. In contrast, the lithium deposit layer (32.7 μm thick) on the Cu foil with in-situ crystallization at 0°C (Example 1) remained intact even after multiple, higher-degree bends, maintaining a secure contact with the Cu foil.

[0117] The lithium deposit layer on the Cu foil was peeled off. For the lithium deposit layer of Comparative Example 1, since the contact with the current collector was very weak, the lithium deposit layer only needed to be bent at a small angle by the current collector to be peeled off. For Example 1, since the contact between the lithium deposit layer and the current collector was very close, it was necessary to use double-sided conductive copper tape to stick on the lithium deposit layer for peeling, and the above lithium deposit layer was pasted on the SEM sample stage for morphology observation.

[0118] Figure 2 (a) and (b) respectively show the SEM morphology of the lithium deposit layer near the Cu foil side after the lithium deposit layer of Comparative Example 1 and Example 1 is peeled off (bottom view of the lithium deposit layer). It can be seen from the figure that the bottom view of the lithium deposit layer without in-situ crystallization treatment (Comparative Example 1) shows more moss and dendritic lithium, while the bottom view of the lithium deposit layer with in-situ crystallization treatment at 0°C (Example 1) observes a significantly suppressed high aspect ratio lithium deposit morphology, and the densely stacked granular deposited lithium shows more mutual contact.

[0119] Example 2: Negative-electrode-free soft-pack lithium metal battery

[0120] The positive electrode is a 4μm thick aluminum foil coated on both sides with high nickel ternary positive electrode lithium nickel cobalt manganese oxide Li[Ni 0.8 Mn 0.1 Co 0.1 ]O2 (NCM811) positive electrode material layer, composed of 97.5wt.% active material, 1.0wt.% conductive agent, 1.5wt.% binder, single-sided coating density is 26.5mg / cm 2 The negative electrode is a 4μm-thick copper foil current collector with no active material. The separator is a 12μm-thick polyethylene (PE) membrane. Liquid injection and packaging are performed in a glove box using a vacuum pre-sealer. The electrolyte uses a localized high-concentration electrolyte, in which the mass proportion of lithium salt is 19.0wt%. The electrolyte injection rate for the soft-pack battery is 1.5g / Ah. The capacity of the negative-electrode-free soft-pack lithium metal battery is 2.7Ah, corresponding to an energy density of 549Wh / kg.

[0121] In-situ crystal planting treatment: After the battery is filled and packaged, the in-situ crystal planting treatment is carried out before formation: at a temperature of 0°C, at a constant charge rate of 1C = 5.6mA cm -2 Charging, the charging time is 36s, and a lithium phytoplankton layer is formed on the surface of the copper foil, as shown in Figure 3 (a). It can be seen that the lithium is evenly distributed with a size of ~100nm.

[0122] Electrochemical test method: Perform conventional charge and discharge cycles: at a temperature of 25°C, the voltage range is set at 2.8-4.4V (100% DoD), and after cycles at a charge and discharge rate of 0.1C, perform long-term charge and discharge cycles at a charge rate of 0.2C and a discharge rate of 0.5C.

[0123] Figure 3 (b) shows the image of the planted crystal layer that is still maintained on the surface of the current collector after 10 cycles. The morphology of the planted crystal layer has not changed significantly, indicating that it has sustainable characteristics.

[0124] Example 3:

[0125] The difference between the preparation method of the negative electrode-free soft-pack lithium metal battery and Example 2 is that the temperature of the in-situ crystal planting treatment is set to 20°C.

[0126] Example 4:

[0127] The difference between the preparation method of the negative electrode-free soft-pack lithium metal battery and Example 2 is that the temperature of the in-situ crystal planting treatment is set to 40°C.

[0128] Example 5:

[0129] The difference between the preparation method of the negative electrode-free soft-pack lithium metal battery and Example 2 is that the temperature of the in-situ crystal planting treatment is set to 60°C.

[0130] Example 6:

[0131] The difference between the preparation method of the negative electrode-free soft-pack lithium metal battery and Example 2 is that the electrolyte uses a fluorinated amide electrolyte with a molar ratio of 1:5.

[0132] Example 7:

[0133] The positive electrode is a 4μm thick aluminum foil coated on both sides with high nickel ternary positive electrode lithium nickel cobalt manganese oxide Li[Ni 0.8 Mn 0.1 Co 0.1 ]O2 (NCM811) positive electrode material layer, composed of 90.0wt.% NCM811, 7.5wt.% Li2NiO2 active material, 1.0wt.% conductive agent, 1.5wt.% binder, with a single-sided coating density of 26.5mg / cm 2 The negative electrode is a 4μm-thick copper foil current collector with no active material. The separator is a 12μm-thick polyethylene (PE) membrane. Liquid injection and packaging are performed in a glove box using a vacuum pre-sealer. The electrolyte uses a localized high-concentration electrolyte, and the electrolyte injection rate for the soft-pack battery is 1.5g / Ah. The capacity of this negative-electrode-free soft-pack lithium metal battery is 2.62Ah, corresponding to an energy density of 533Wh / kg.

[0134] In-situ crystal planting treatment: at a temperature of 0°C, with a constant charge rate of 1C = 5.6mAcm -2 Charging, charging time is 36s.

[0135] The electrochemical test method is the same as that in Example 2.

[0136] Example 8:

[0137] The preparation method of the negative electrode-free soft-pack lithium metal battery is different from that of Example 7 in that the electrolyte uses a fluorinated amide electrolyte with a molar ratio of 1:5.

[0138] The electrochemical test method is the same as that in Example 2.

[0139] Example 9:

[0140] The preparation method of the negative electrode-free soft-pack lithium metal battery is the same as that in Example 8.

[0141] The electrochemical test method is the same as that of Example 2, except that the voltage range is set at 3.6-4.3 V (80% DoD).

[0142] Comparative Example 2:

[0143] The preparation method of the negative electrode-free soft-pack lithium metal battery differs from that of Example 2 in that the in-situ crystal planting process is eliminated.

[0144] Comparative Example 3:

[0145] The preparation method of the negative electrode-free soft-pack lithium metal battery is different from that of Example 7 in that the in-situ crystal planting process is eliminated.

[0146] Comparative Example 4:

[0147] The preparation method of the negative electrode-free soft-pack lithium metal battery differs from that of Example 2 in that the electrolyte uses a fluorinated amide electrolyte with a molar ratio of 1:5 and the in-situ crystal planting process is eliminated.

[0148] Comparative Example 5:

[0149] The preparation method of the negative electrode-free soft-pack lithium metal battery differs from that of Example 7 in that the electrolyte uses a fluorinated amide electrolyte with a molar ratio of 1:5 and the in-situ crystal planting process is eliminated.

[0150] Table 1 summarizes the test results of Examples 2-9 and Comparative Examples 2-5.

[0151] Table 1

[0152] As can be seen from Table 1, in the negative electrode-free soft-pack lithium metal battery with a local high-concentration electrolyte, after the in-situ crystal planting treatment is implemented (Example 2), the cycle life can be increased by 65.8% compared with Comparative Example 2; in the negative electrode-free soft-pack lithium metal battery with a fluorinated amide electrolyte, after the in-situ crystal planting treatment is implemented (Example 6), the cycle life can be increased by 45.7% compared with Comparative Example 4, indicating that the in-situ crystal planting treatment can improve the cycle life of the battery in both of the above electrolytes.

[0153] When a lithium-supplementing additive was added to a negative-electrode-free soft-pack lithium metal battery with a locally high-concentration electrolyte and then combined with in-situ crystal planting (Example 7), the cycle life was increased by 97.4% compared to Comparative Example 2. When a lithium-supplementing additive was added to a negative-electrode-free soft-pack lithium metal battery with a fluorinated amide electrolyte and then combined with in-situ crystal planting (Example 8), the cycle life was increased by 186.5% compared to Comparative Example 4. Furthermore, when the depth of discharge was controlled to 80% (Example 9), the cycle life was increased by 9 times compared to Comparative Example 4. This result shows that the synergistic effect of in-situ crystal planting, fluorinated amide electrolyte, and lithium-supplementing additive can significantly extend the cycle life of negative-electrode-free soft-pack lithium metal batteries while maintaining the high energy density characteristics.

[0154] Figure 4 shows the time-voltage curve of the in-situ crystallization process of the negative electrode-free soft-pack lithium metal battery after the battery is filled and packaged but before formation. The rate of the in-situ crystallization process is 1C (1C = 5.6 mA cm -2 ), after 36s of fast charging, the capacity of the lithium metal plating during this process is very low (~0.056mAh cm -2 ), so it will not affect the energy density of the soft-pack battery.

[0155] Figure 5 shows the morphology of the crystal layer on the current collector of a negative electrode-free soft-pack lithium metal battery after in-situ crystallization treatment after battery filling and packaging but before formation. The in-situ crystallization temperature (0°C) in Example 2 resulted in an average coverage of 95% of the lithium metal on the current collector, essentially achieving uniform and dense coverage of the lithium metal on the current collector.

Claims

1. A negative electrode-free lithium metal battery, comprising: A positive electrode, the positive electrode comprising a positive electrode current collector and a positive electrode active material layer; Negative electrode current collector, A lithium crystal layer formed on the surface of the negative electrode current collector corresponding to the positive electrode, wherein the lithium crystal layer is composed of metallic lithium deposited in situ by electrochemical means; electrolyte; and Diaphragm.

2. The negative electrode-free lithium metal battery according to claim 1, wherein: The thickness of the lithium planting layer is 5-2000nm, preferably 20-1000nm, and more preferably 50-500nm.

3. The negative electrode-free lithium metal battery according to claim 1, wherein: The electrochemical in-situ deposition comprises the following steps: The negative electrode-free lithium metal battery is charged with constant current and / or constant voltage after liquid injection and packaging and before formation. During the charging process, the nucleation overpotential of the metal lithium is controlled to be 0.1-2V relative to the standard potential of the metal lithium, preferably 0.6-1.5V; Preferably, the constant current charging process is: charging at a constant charging rate C1 at a temperature T1, and the charging time is t1; The constant voltage charging process is: at temperature T2, charging with a constant charging voltage V1 and a charging capacity of R1; Among them, C1 is 0.3 to 10.0C, preferably 0.5 to 5C, more preferably 0.8 to 3C, t1 is 0.1 to 3600 s, preferably 1 to 100 s, more preferably 10 to 60 s, T1 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, V1 is 3.2 to 6 V, preferably 3.8 to 5 V, more preferably 3.8 to 4.2 V, R1 is 0.01~1mAh / cm 2 , preferably 0.02 to 0.5 mAh / cm 2 , more preferably 0.02 to 0.2 mAh / cm 2 , T2 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C; Preferably, the ratio of the metal lithium covering the surface of the negative electrode current collector is greater than 80%.

4. The negative electrode-free lithium metal battery according to claim 1, wherein: The negative electrode current collector is selected from a metal current collector, a non-metal current collector or a metal-polymer composite current collector; Preferably, the metal current collector is an alloy of one or more selected from copper, nickel, cobalt, titanium and iron, preferably copper foil; the non-metallic current collector is one or more selected from carbon fiber cloth, carbon fiber paper, graphite paper and conductive organic polymer, preferably graphite paper; the polymer in the metal-polymer composite current collector is one or more selected from polycarbonate, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polypropylene, polyethylene, polyvinylidene chloride, polybenzimidazole, ethylene-vinyl acetate copolymer, polyimide, polyimide-triphenyl phosphate copolymer and polyurethane, preferably a composite current collector of copper and polyimide-triphenyl phosphate copolymer; Preferably, the negative electrode-free lithium metal battery further comprises a coating formed on at least one side of the negative electrode current collector, wherein the coating is selected from a metal coating, a non-metal coating or a metal-non-metal mixed coating; Preferably, the metal is one selected from indium, cobalt, germanium, aluminum, tin, gold, silver, zinc, magnesium, silicon, bismuth, palladium and platinum, or an alloy of two or more of the foregoing, and the non-metal is one or more selected from acetylene black, ketjen black, carbon black, graphite, graphene, conductive polymers and artificial interface films.

5. The negative electrode-free lithium metal battery according to claim 1, wherein: The positive electrode current collector is selected from a metal current collector, a non-metal current collector or a metal-polymer composite current collector; Preferably, the metal current collector is an alloy of one or more selected from aluminum, titanium, nickel and iron, preferably aluminum foil; the non-metallic current collector is one or more selected from carbon fiber cloth, carbon fiber paper, graphite paper and conductive organic polymer, preferably carbon fiber paper; the polymer in the metal-polymer composite current collector is one or more selected from polycarbonate, polystyrene, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polypropylene, polyethylene, polyvinylidene chloride, polybenzimidazole, ethylene-vinyl acetate copolymer, polyimide, polyimide-triphenyl phosphate copolymer and polyurethane, preferably a composite current collector of aluminum and polyimide-triphenyl phosphate copolymer.

6. The negative electrode-free lithium metal battery according to claim 1, wherein: The positive electrode active material layer comprises a positive electrode active material and a lithium supplement additive; Preferably, the positive electrode active material is one or more selected from the group consisting of a ternary nickel cobalt lithium manganese oxide positive electrode material, a lithium-rich manganese-based positive electrode material, a lithium nickel manganese oxygen positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganese oxide positive electrode material, a lithium iron manganese phosphate positive electrode material, a lithium cobalt oxide positive electrode material and a lithium sulfide positive electrode material, preferably a ternary nickel cobalt lithium manganese oxide positive electrode material; Preferably, the lithium-supplementing additive is one or more selected from binary lithium-containing compounds and lithium-rich compounds; the binary lithium-containing compound is one or more selected from Li2O, Li2O2, Li3N, Li2S and Li2C2O4, preferably Li2C2O4; the lithium-rich compound is one or more selected from Li2Ni 1-x M x O2 or Li5Fe 1-x N x O4, wherein 0≤x<1, and M is at least one selected from Mn, Fe, Co, Cu, Zn, Mg, and Cd, and N is at least one selected from Mn, Ni, Co, Cu, Zn, Mg, and Cd. Preferably, the lithium supplement additive is one or both of Li2NiO2 and Li5FeO4.

7. The negative electrode-free lithium metal battery according to claim 1, wherein: The electrolyte comprises at least one lithium salt and an organic solvent, and preferably, the electrolyte further comprises a flame retardant or an inert diluent; Preferably, the electrolyte comprises at least one boron-containing lithium salt, and a fluorinated amide compound; The boron-containing lithium salt is one or more selected from lithium difluorooxalatoborate, lithium dioxalatoborate, lithium tetrafluoroborate, lithium fluoroalkoxyborate, lithium fluoroalkoxyfluoroborate, lithium fluoroalkoxybisfluoroborate and lithium fluoroalkoxytrifluoroborate, preferably lithium difluorooxalatoborate; and / or The fluorinated amide compound is one or more selected from N,N-dimethyltrifluoroacetamide, N-methoxy-N-methyltrifluoroacetamide, N-methyltrifluoroacetamide, N,N-diethyltrifluoroacetamide, N-(trifluoromethanesulfonyl)trifluoroacetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, N-methyl-N-(trimethylsilyl)trifluoroacetamide, bis(trimethylsilyl)trifluoroacetamide, N-methyltrimethylsilyltrifluoroacetamide, N-methylbis(trifluoroacetyl)amide, trifluoroacetamide and bistrifluoroacetamide, preferably N,N-dimethyltrifluoroacetamide; Preferably, the electrolyte comprises lithium difluorooxalatoborate and N,N-dimethyltrifluoroacetamide, and the molar ratio of lithium difluorooxalatoborate to N,N-dimethyltrifluoroacetamide is 1:

5.

8. The negative electrode-free lithium metal battery according to claim 1, wherein: The separator is selected from porous polyolefin polymer films or porous non-woven fabrics. Furthermore, at least one side of the diaphragm has a ceramic coating or a solid electrolyte coating.

9. The method for preparing a negative electrode-free lithium metal battery according to any one of claims 1 to 8, comprising the following steps: Assembling a positive electrode, a negative electrode current collector, a separator and an electrolyte into a negative electrode-free lithium metal battery; The negative electrode-free lithium metal battery is charged at a constant current and / or a constant voltage after liquid injection and packaging and before formation. During the charging process, the nucleation overpotential of the metal lithium is controlled to be 0.1 to 2 V relative to the standard potential of the metal lithium, thereby obtaining the negative electrode-free lithium metal battery including the negative electrode current collector for forming a lithium planting layer; Preferably, the constant current charging process is: charging at a constant charging rate C1 at a temperature T1, and the charging time is t1; The constant voltage charging process is: at temperature T2, charging with a constant charging voltage V1 and a charging capacity of R1; Among them, C1 is 0.3 to 10.0C, preferably 0.5 to 5C, more preferably 0.8 to 3C, t1 is 0.1 to 3600 s, preferably 1 to 100 s, more preferably 10 to 60 s, T1 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C, V1 is 3.2 to 6 V, preferably 3.8 to 5 V, more preferably 3.8 to 4.2 V, R1 is 0.01~1mAh / cm 2 , preferably 0.02 to 0.5 mAh / cm 2 , more preferably 0.02 to 0.2 mAh / cm 2 , T2 is -60 to 120°C, preferably -30 to 60°C, more preferably -30 to 30°C.

10. Use of the negative electrode-free lithium metal battery according to any one of claims 1 to 8 in electronic devices, smart grids or electric vehicles.

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