Lithium metal battery, manufacturing method thereof and electric equipment

Abstract

The invention relates to the field of lithium metal batteries, and provides a lithium metal battery, a manufacturing method thereof and electric equipment, which are at least beneficial to improving the stability of a cathode-free lithium metal battery. The manufacturing method comprises the following steps: carrying out winding treatment or lamination treatment on a positive plate, a negative current collector and a diaphragm, and then putting into a shell to form a battery cell assembly; a first liquid injection process is carried out on the cell assembly, a first electrolyte is injected into the cell assembly, and the first electrolyte comprises the following components: lithium polysulfide, lithium nitrate, lithium salt and the balance of a non-aqueous organic solvent; performing a first formation process on the cell assembly; a second liquid injection process is carried out on the cell assembly, a second electrolyte is injected into the cell assembly, and the second electrolyte comprises fluoroethylene carbonate, a lithium salt, an electrostatic shielding additive, an anchoring filling additive and the balance of a non-aqueous organic solvent; and performing a second formation process on the cell assembly.

Description

Technical Field

[0001] This application relates to the field of lithium metal batteries, and particularly to a lithium metal battery, a manufacturing method thereof, and an electrical device. Background Art

[0002] With the rapid development of renewable energy, the energy density of energy storage batteries has become a key factor determining technological competitiveness. The energy density of traditional lithium-ion batteries has gradually increased from the initial 100 Wh / kg to 250 Wh / kg - 300 Wh / kg, but this progress has approached the theoretical limit, and further improvement faces huge challenges. Against this background, lithium metal batteries have emerged as an important technological path to break through the energy density bottleneck.

[0003] A lithium metal battery uses manganese dioxide as the positive electrode material, metallic lithium or alloy metal as the negative electrode material, and a non-aqueous electrolyte solution. The lithium metal negative electrode has significant advantages compared with the traditional graphite negative electrode. The theoretical specific capacity of the lithium metal negative electrode is as high as 3860 mAh / kg, which is 10 times that of the graphite negative electrode (372 mAh / kg), is conducive to increasing the battery voltage, and has a simple manufacturing process, which is conducive to reducing the complexity of the electrode structure. The non-aqueous lithium metal battery and the traditional lithium metal negative electrode battery are actually highly consistent in the basic working principle. Both are based on the reciprocating migration of lithium ions between the positive and negative electrodes. During charging, lithium ions are deintercalated from the positive electrode and deposited as metallic lithium on the surface of the negative electrode. During discharging, metallic lithium is oxidized and returns to the positive electrode. The difference is that in the non-aqueous lithium metal battery, the negative electrode sheet is composed of a current collector, which further simplifies the electrode design and enables the energy density to be increased to 350 Wh / kg - 400 Wh / kg.

[0004] However, the problem of interface instability faced by the negative electrode sheet of the non-aqueous lithium metal battery is still severe. Summary of the Invention

[0005] Embodiments of this application provide a lithium metal battery, a manufacturing method thereof, and an electrical device, which are at least conducive to improving the stability of the non-aqueous lithium metal battery.

[0006] According to some embodiments of the present application, on the one hand, an embodiment of the present application provides a manufacturing method of a lithium metal battery, including: providing a positive electrode sheet, a negative electrode current collector, and a separator, the positive electrode sheet including a positive electrode current collector and a positive electrode material layer; winding or laminating the positive electrode sheet, the negative electrode current collector, and the separator and then placing them into a housing to form an electrode core assembly, the separator being located between the positive electrode sheet and the negative electrode current collector; performing a first liquid injection process on the electrode core assembly to inject a first electrolyte into the electrode core assembly, the components of the first electrolyte including: 0.1 wt% - 5 wt% of lithium polysulfide, 0.1 wt% - 5 wt% of lithium nitrate, 5 wt% - 15 wt% of a lithium salt, and the balance being a non-aqueous organic solvent; performing a first formation process on the electrode core assembly; performing a second liquid injection process on the electrode core assembly to inject a second electrolyte into the electrode core assembly, the components of the second electrolyte including: 5 wt% - 35 wt% of fluoroethylene carbonate, 5 wt% - 15 wt% of a lithium salt, 0.05 wt% - 20 wt% of an electrostatic shielding additive, 0.05 wt% - 20 wt% of an anchoring filling additive, and the balance being a non-aqueous organic solvent; performing a second formation process on the electrode core assembly.

[0007] In some embodiments, the non-aqueous organic solvent in the first electrolyte includes an ether-based solvent, and the mass ratio of the ether-based solvent to the mass of the non-aqueous organic solvent is greater than 50 wt%.

[0008] In some embodiments, the non-aqueous organic solvent in the second electrolyte includes an ether-based solvent and a sulfone-based solvent, and the total mass ratio of the ether-based solvent and the sulfone-based solvent to the mass of the non-aqueous organic solvent is greater than 50 wt%.

[0009] In some embodiments, in the second electrolyte, the mass ratio of the ether-based solvent to the sulfone-based solvent is greater than or equal to 1.

[0010] In some embodiments, the first formation process includes: charging the electrode core assembly to a state of charge greater than or equal to 50% at a first charging rate and a first temperature; the second formation process includes: charging the electrode core assembly to a state of charge greater than 85% at a second charging rate and a second temperature; wherein, the first charging rate is less than the second charging rate, and the first temperature is less than the second temperature.

[0011] In some embodiments, the first charging rate is 0.01C - 0.2C; the second charging rate is 0.2C - 0.5C; the first temperature is 40°C - 50°C; the second temperature is 40°C - 50°C.

[0012] In some embodiments, the anchoring filling additive is selected from at least one of fullerene derivatives, organosilicon compounds, or carbon-based nanomaterials.

[0013] In some embodiments, the electrostatic shielding additive is selected from at least one of organic quaternary ammonium salts, metal halides, or organic ionic liquids.

[0014] In some embodiments, the negative current collector is selected from one of copper foil, nano-coated copper, copper foam, copper mesh, metal-carbon composite current collector, or lithium-inserting alloy-based current collector.

[0015] In some embodiments, the material of the positive electrode material layer includes at least one of layered oxide materials, spinel structure materials, polyanion materials, lithium-rich manganese-based materials, transition metal fluoride materials, or organic materials.

[0016] According to some embodiments of the present application, on the other hand, the present application embodiments also provide a lithium metal battery prepared by using the manufacturing method of the lithium metal battery in the above embodiments.

[0017] According to some embodiments of the present application, on another aspect, the present application embodiments also provide an electrical device. The electrical device includes the lithium metal battery and a load in the above embodiments; or, the electrical device includes an energy storage system and a load, and the energy storage system includes a plurality of lithium metal batteries in the above embodiments.

[0018] The technical solutions provided by the embodiments of the present application have at least the following advantages: In the manufacturing method of the lithium metal battery provided by the embodiments of the present application, the positive electrode sheet includes a positive current collector and a positive electrode material layer. Using the negative current collector as the negative electrode sheet to form a lithium metal battery without a negative electrode. After assembling the positive electrode sheet, the negative current collector, and the separator into a battery cell assembly, an inorganic-organic composite interface layer is constructed by injecting electrolyte in stages and the lithium deposition behavior is dynamically regulated. The first injection of electrolyte forms a rigid composite inorganic interface layer, and the second injection of electrolyte superimposes a flexible organic layer and introduces functional additives to systematically solve the problems of interface stability and lithium dendrite growth. Based on the interface dynamic requirements of the lithium metal battery without a negative electrode, the first injection of electrolyte focuses on constructing a highly stable composite inorganic interface layer to reduce the initial side reaction activity; the second injection of electrolyte continuously optimizes the deposition behavior and repairs interface defects through the flexible organic film and the dynamic regulation dual path. The collaborative design of the two-step process takes into account both the rigid support and dynamic adaptability of the interface, providing double guarantees for long cycle stability and high rate performance.

[0019] In the first electrolyte injection process, a first electrolyte including lithium polysulfide (Li2S8), lithium nitrate (LiNO3), a lithium salt, and a non-aqueous organic solvent is injected into the battery cell assembly, and then a first formation process is carried out to form a composite inorganic interface layer by utilizing the complementary characteristics of lithium polysulfide and lithium nitrate. The sulfide layer (Li2S) generated by Li2S8 has high mechanical brittleness and is prone to cracking due to stress concentration; although the nitride layer (Li3N) formed by LiNO3 has excellent chemical stability, it has poor adaptability to volume expansion. Through the synergistic effect of Li2S8 and LiNO3, a Li2S-Li3N cross-linked structure is formed by using a sulfur-nitrogen composite mechanism, which has both high ionic conductivity and mechanical toughness, can not only inhibit the decomposition of the electrolyte, but also provide a stable foundation for subsequent cycles. In the second electrolyte injection process, a second electrolyte including fluoroethylene carbonate (FEC), a lithium salt, an electrostatic shielding additive, an anchoring and filling additive, and a non-aqueous organic solvent is injected into the battery cell assembly, and then a second formation process is carried out. A flexible organic layer is generated by the decomposition of FEC and covers the surface of the composite inorganic interface layer to relieve the stress impact caused by volume change. Its dynamic repair characteristics can adapt to the stress change caused by the volume expansion / contraction of lithium metal and reduce the risk of interface film rupture. An electrostatic shielding additive and an anchoring and filling additive are also introduced in the second electrolyte injection process. The electrostatic shielding additive releases high-valent cations to neutralize the local electric field distortion in the lithium deposition convex region, balance the local electric field distribution, inhibit the excessive deposition tendency of lithium ions in the convex region, and block the dendrite nucleation path and thus block the growth of dendrite tips; the anchoring and filling additive preferentially guides lithium ions to form a dense lithium layer in the interface concave region through defect site adsorption and directional deposition guidance, promoting the uniformity of the deposition morphology. The electrostatic shielding additive is used to inhibit the tip effect, and the anchoring and filling additive repairs the interface defects. The electrostatic shielding additive and the anchoring and filling additive synergistically guide the directional deposition of lithium ions through physical confinement and chemical bonding to repair microscopic defects, not only realizing the uniformity of lithium deposition morphology, but also reducing the interface impedance and optimizing the ion transport kinetics. The synergistic effect of the electrostatic shielding additive and the anchoring and filling additive breaks through the limitation of a single type of additive that only regulates local deposition, reduces the interface impedance and optimizes the lithium ion transport kinetics through a complementary mechanism, thereby improving the cycle stability of the lithium metal battery at high rates. Brief Description of the Drawings

[0020] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation; in order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 The flowchart corresponding to the manufacturing method of the lithium metal battery provided by an embodiment of the present application. Detailed implementation manners

[0022] As can be seen from the background art, the negative electrode sheet of the non-anode lithium metal battery has the problem of unstable interface.

[0023] Facing the potential advantages of lithium metal batteries, researchers have explored various technical routes to solve their inherent defects. These solutions mainly include surface modification of current collectors, construction of artificial interface films, and three-dimensional current collector design, etc., attempting to improve lithium metal deposition behavior and interface stability from different perspectives. However, these solutions either require complex manufacturing processes or involve fundamental changes in the electrode structure, greatly increasing the difficulty and cost of technology implementation.

[0024] Among many technical routes, electrolyte optimization highlights unique technical advantages. Compared with other solutions, electrolyte optimization has significant characteristics such as simple process, low transformation cost, and easy large-scale industrial application. By adjusting the electrolyte components, it can directly act on the negative electrode interface of the lithium metal battery and regulate the lithium deposition behavior at the molecular scale, becoming the most commercially promising technical route.

[0025] Since the volume expansion rate of lithium metal is as high as about 300%, its deposition behavior is extremely uneven and it is extremely easy to form lithium dendrites. Under high-rate charge and discharge conditions, the uneven local current density makes it difficult to control the lithium deposition morphology, and the interface side reactions are serious, restricting the practical application of the battery.

[0026] The strategy of conventional single-injection electrolyte exposes obvious limitations. In the initial film-forming stage, the additives are prone to uneven reaction; in the long-term cycling stage, the interface film is difficult to adapt to volume changes. The film-forming potentials of different additives vary greatly, and the quality of the interface film cannot be precisely regulated, which makes the performance of lithium metal negative electrode batteries or non-anode lithium metal batteries fail to break through the key bottleneck all the time.

[0027] Therefore, there is an urgent need for an electrolyte solution that can be optimized in stages to simultaneously meet two key requirements: ensuring the uniform stability and mechanical strength of the initial film formation, and ensuring the flexibility of the interface film during long-term cycling. By precisely regulating the lithium deposition behavior and inhibiting the growth of lithium dendrites, it is expected to fundamentally solve the core technical problems restricting the development of lithium metal batteries.

[0028] An embodiment of the present application provides a lithium metal battery, its manufacturing method, and an electrical device. In the manufacturing method of the lithium metal battery, a positive electrode sheet, a negative electrode current collector, and a separator are assembled into a battery cell assembly. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer, and the negative electrode current collector is used as the negative electrode sheet to form a non-anode lithium metal battery.

[0029] By injecting electrolyte in stages to adapt to the interface requirements, the first injection and formation are used to construct a sulfur-nitrogen synergistic composite inorganic interface layer, which inhibits initial dendrite nucleation and side reactions and provides mechanical support; the second injection and formation introduce high-concentration vinylene carbonate fluoride to form a flexible organic layer, and introduce electrostatic shielding additives and anchoring filling additives to synergistically and dynamically regulate the deposition path of lithium ions, quickly realizing the homogenization of the interface morphology and optimizing the long-term cycling performance of the lithium metal battery.

[0030] The design of two-step injection avoids the conflicts of additive functions and the contradiction of film-forming potential in single injection, and at the same time takes into account the process feasibility and large-scale production cost control, providing a reliable technical path for the commercialization of the anode-free lithium metal battery.

[0031] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features.

[0032] In the description of the embodiments of the present application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0033] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0034] In the description of the embodiments of the present application, when a component "includes" another component, unless otherwise stated, other components are not excluded, and other components may further be included.

[0035] The terms used in the description of the various embodiments herein are only for describing specific embodiments and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, "component" is also intended to include the plural form, unless the context clearly indicates otherwise.

[0036] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are provided to help readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0037] Figure 1The flowchart corresponding to the manufacturing method of a lithium metal battery provided by an embodiment of the present application.

[0038] Refer to Figure 1 , the manufacturing method of the lithium metal battery provided by the embodiment of the present application is as follows.

[0039] S101. Provide a positive electrode sheet, a negative electrode current collector, and a separator. The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer.

[0040] S102. Wind or stack the positive electrode sheet, the negative electrode current collector, and the separator, and then place them in a housing to form an electrode core assembly. The separator is located between the positive electrode sheet and the negative electrode current collector.

[0041] S103. Perform a first liquid injection process on the electrode core assembly, and inject a first electrolyte into the electrode core assembly. The components of the first electrolyte include: 0.1 wt% - 5 wt% of lithium polysulfide, 0.1 wt% - 5 wt% of lithium nitrate, 5 wt% - 15 wt% of a lithium salt, and the balance of a non-aqueous organic solvent.

[0042] S104. Perform a first formation process on the electrode core assembly.

[0043] S105. Perform a second liquid injection process on the electrode core assembly, and inject a second electrolyte into the electrode core assembly. The components of the second electrolyte include: 5 wt% - 35 wt% of fluoroethylene carbonate, 5 wt% - 15 wt% of a lithium salt, 0.05 wt% - 20 wt% of an electrostatic shielding additive, 0.05 wt% - 20 wt% of an anchoring filling additive, and the balance of a non-aqueous organic solvent.

[0044] S106. Perform a second formation process on the electrode core assembly.

[0045] In the manufacturing method of the lithium metal battery provided by the embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer. The negative electrode current collector is used as the negative electrode sheet to form a lithium metal battery without a negative electrode. After assembling the positive electrode sheet, the negative electrode current collector, and the separator into an electrode core assembly, an inorganic-organic composite interface layer is constructed by injecting electrolytes in stages and the lithium deposition behavior is dynamically regulated. The first liquid injection forms a rigid composite inorganic interface layer, and the second liquid injection superimposes a flexible organic layer and introduces functional additives to systematically solve the problems of interface stability and lithium dendrite growth. Based on the interface dynamic requirements of the lithium metal battery without a negative electrode, the first liquid injection focuses on constructing a highly stable composite inorganic interface layer to reduce the initial side reaction activity; the second liquid injection continuously optimizes the deposition behavior and repairs interface defects through a flexible organic film and a dynamic regulation dual path. The collaborative design of the two-step process takes into account the rigid support and dynamic adaptability of the interface, providing double guarantees for long cycle stability and high rate performance.

[0046] In the first electrolyte injection process, a first electrolyte including lithium polysulfide (Li2S8), lithium nitrate (LiNO3), a lithium salt, and a non-aqueous organic solvent is injected into the cell assembly, and then a first formation process is carried out. The complementary characteristics of lithium polysulfide and lithium nitrate are utilized to form a composite inorganic interface layer. The sulfide layer (Li2S) generated by Li2S8 has high mechanical brittleness and is prone to cracking due to stress concentration; although the nitride layer (Li3N) formed by LiNO3 has excellent chemical stability, it has poor adaptability to volume expansion. Through the synergistic effect of Li2S8 and LiNO3, a Li2S-Li3N cross-linked structure is formed by the sulfur-nitrogen composite mechanism, which has both high ionic conductivity and mechanical toughness, can not only inhibit the decomposition of the electrolyte, but also provide a stable foundation for subsequent cycles. In the second electrolyte injection process, a second electrolyte including fluoroethylene carbonate (FEC), a lithium salt, an electrostatic shielding additive, an anchoring and filling additive, and a non-aqueous organic solvent is injected into the cell assembly, and then a second formation process is carried out. A flexible organic layer is generated by the decomposition of FEC and covers the surface of the composite inorganic interface layer to relieve the stress impact caused by volume change. Its dynamic repair characteristics can adapt to the stress change caused by the volume expansion / contraction of lithium metal and reduce the risk of interface film rupture. An electrostatic shielding additive and an anchoring and filling additive are also introduced in the second electrolyte injection process. The electrostatic shielding additive releases high-valence cations to neutralize the local electric field distortion in the lithium deposition convex region, balance the local electric field distribution, inhibit the excessive deposition tendency of lithium ions in the convex region, and block the dendrite nucleation path and thus block the growth of the dendrite tip; the anchoring and filling additive preferentially guides lithium ions to form a dense lithium layer in the interface concave region through defect site adsorption and directional deposition guidance, promoting the uniformity of the deposition morphology. The electrostatic shielding additive is used to inhibit the tip effect, and the anchoring and filling additive is used to repair interface defects. The electrostatic shielding additive and the anchoring and filling additive synergistically guide the directional deposition of lithium ions through physical confinement and chemical bonding to repair micro-defects, not only achieving the uniformity of lithium deposition morphology, but also reducing the interface impedance and optimizing the ion transport kinetics. The synergistic effect of the electrostatic shielding additive and the anchoring and filling additive breaks through the limitation of a single type of additive that only regulates local deposition, reduces the interface impedance and optimizes the lithium ion transport kinetics through a complementary mechanism, thereby improving the cycle stability of the lithium metal battery at high rates.

[0047] In step S101, the positive current collector is aluminum foil or other conductive substrates suitable for high-voltage systems. The material of the positive electrode material layer includes a positive electrode active material, a binder, and a conductive agent.

[0048] The positive electrode active material is selected from layered oxide positive electrode materials, spinel structure positive electrode materials, polyanion positive electrode materials, lithium-rich manganese-based positive electrode materials, transition metal fluoride positive electrode materials, and organic positive electrode materials.

[0049] Among them, the chemical formula of the layered oxide positive electrode material can be Li xMO₂ (where M is a combination of transition metal elements such as Ni, Co, Mn, Al, etc.); A typical representative of the spinel-structured cathode material is LiMn₂O₄, which has high safety and good rate performance; The general formula of the polyanion cathode material is Li x MPO₄ (where M is Fe, Mn, Co, V, etc.), among which LiFePO₄ has been widely used due to its excellent cycle stability and safety; The lithium-rich manganese-based cathode material (Li x M y Mn z O₂, where M is Ni, Co, etc.) has attracted attention due to its high specific capacity and high safety; The transition metal fluoride cathode materials (such as FeF₃, CoF₃) have a relatively high voltage platform and high energy density; The organic cathode materials (such as polymers containing carbonyl or quinone groups) have become potential candidates due to their environmental friendliness and structural designability.

[0050] The binder is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), or polyacrylic acid (PAA).

[0051] The conductive agent is selected from one or more of conductive carbon black, graphene, carbon nanotubes, or graphite.

[0052] The negative electrode current collector is selected from one of copper foil, nano-coated copper, copper foam, copper mesh, metal-carbon composite current collector, or lithium-inserted alloy-based current collector. Nano-coated copper can improve wettability and interface stability; The negative electrode current collectors with three-dimensional structures such as copper foam and copper mesh are beneficial to improving wettability and interface stability; The metal-carbon composite current collector can improve the conductivity and mechanical stability of the negative electrode.

[0053] The separator includes polypropylene (PP) separator, polyethylene (PE) separator, ceramic-coated separator, high-strength polymer separator, and composite separator. The PP and PE porous separators have good mechanical strength and chemical stability; The ceramic-coated separator is coated with a ceramic material on the basis of the PP or PE separator, improving the high-temperature resistance and safety of the separator; The high-strength polymer separator (such as aramid nanofiber separator) has excellent puncture resistance and high-temperature resistance characteristics; The composite separator (such as the coated separator containing a solid electrolyte) can further enhance the stability of lithium deposition, reduce the risk of dendrite growth, and improve the cycle life.

[0054] In step S102, according to the battery type, the housing can be divided into a cylindrical battery housing, a square battery housing, and a soft-pack battery housing. The cylindrical battery housing is usually made of steel or aluminum alloy; The square battery housing is usually made of aluminum or steel; The soft-pack battery housing is usually made of an aluminum-plastic composite film, and the aluminum-plastic composite film includes an outer layer (nylon / PET), an intermediate layer (aluminum foil), and an inner layer (PP heat-sealing layer).

[0055] In step S103, the mass fraction of lithium polysulfide in the first electrolyte can specifically be 0.1 wt%, 0.5 wt%, 1 wt%, 1.4 wt%, 2 wt%, 2.6 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.3 wt%, 4.5 wt%, 4.9 wt% or 5 wt%. The mass fraction of lithium polysulfide refers to the proportion of the mass of lithium polysulfide in the total mass of the first electrolyte.

[0056] The mass fraction of lithium nitrate in the first electrolyte can specifically be 0.1 wt%, 0.5 wt%, 1 wt%, 1.4 wt%, 2 wt%, 2.6 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.3 wt%, 4.5 wt%, 4.9 wt% or 5 wt%. The mass fraction of lithium nitrate refers to the proportion of the mass of lithium nitrate in the total mass of the first electrolyte.

[0057] The lithium salt in the first electrolyte can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), preferably one or more of LiPF6, LiBF4, LiBOB, LiDFOB, LiTFSI, and LiFSI.

[0058] The mass fraction of the lithium salt in the first electrolyte can specifically be 5 wt%, 8 wt%, 10 wt%, 12 wt%, 13 wt% or 15 wt%. The mass fraction of the lithium salt refers to the proportion of the mass of the lithium salt in the total mass of the first electrolyte.

[0059] The first electrolyte may further include a film-forming additive, and the film-forming additive can be selected from at least one of cyclic carbonates containing unsaturated bonds, fluorinated cyclic carbonates, cyclic sulfonates, cyclic sulfates, nitrile compounds, cyclic quaternary ammonium sulfonates, silane borates, silane phosphates, or anisole. These additives can optimize the composition and structure of the interface film, enhance its mechanical properties, improve lithium deposition behavior and uniformity, thereby improving the safety and cycle stability of the lithium metal battery.

[0060] The mass fraction of the film-forming additive in the first electrolyte can specifically be 0.1 wt%, 0.5 wt%, 1 wt%, 1.4 wt%, 2 wt%, 2.6 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.3 wt%, 4.5 wt%, 4.9 wt% or 5 wt%. The mass fraction of the film-forming additive refers to the proportion of the mass of the film-forming additive in the total mass of the first electrolyte.

[0061] The non-aqueous organic solvent in the first electrolyte may include an ether-based solvent, and the mass ratio of the ether-based solvent to the non-aqueous organic solvent is greater than 50 wt%, for example, it can specifically be 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt% or 100 wt%. The ether-based solvent has the characteristics of excellent compatibility with lithium metal, high conductivity, low viscosity and low cost. Using the ether-based solvent as the main component is more conducive to improving the stability of the composite inorganic interface film, providing a stable chemical environment for the initial operation of the lithium metal battery, and providing a stable foundation for the subsequent formation of the flexible organic film.

[0062] The ether-based solvents are divided into two categories: chain ethers and cyclic ethers. Chain ethers include, but are not limited to: dimethyl ether (DME), diethyl ether (DEE), 1,2-methoxypropane (MOP), diethylene glycol dimethyl ether (DEDM), triethylene glycol dimethyl ether (TRIEDM), tetraethylene glycol dimethyl ether (TETREDM), ethyl propyl ether (EPE) and some fluorinated chain ethers; cyclic ethers include, but are not limited to: tetrahydrofuran (THF), 2-methylfuran (2-MF), 1,3-dioxolane (DOL), 4,5-diethyl-1,3-dioxolane, 4,5-dimethyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, 2-methyl-1,3-dioxolane and 1,4-dioxolane and their fluorinated compounds.

[0063] The non-aqueous organic solvent in the first electrolyte may also include one or more of carbonate organic solvents, phosphate organic solvents, fluorinated solvents, sulfone-based solvents, nitrile solvents, dioxolane solvents and ionic liquid organic solvents.

[0064] Among them, carbonate organic solvents include but are not limited to: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), trifluoroethyl methyl carbonate (TFMEC), ethyl propyl carbonate (EPC), and methyl propyl carbonate (MPC); phosphate organic solvents include but are not limited to: trimethyl phosphate (TMP), triethyl phosphate (TEP), and dimethyl ethylphosphonate; fluorinated solvents include but are not limited to: fluoroethylene carbonate (FEC), trifluoroethyl methyl carbonate (TFMEC), and other fluorine-modified carbonates, and these solvents have attracted attention due to their excellent electrochemical stability and ability to form a high-quality SEI (solid electrolyte interphase) film; sulfone compounds mainly include: dimethyl sulfone (DMSO) and diethyl sulfone (DES), and these solvents can improve the interfacial stability and ion transport performance in some high-temperature systems; nitrile compounds include but are not limited to: acetonitrile (AN), propionitrile (ACN), and adiponitrile (ADN), and they are used to enhance ion conductivity due to their high dielectric constant and low viscosity; dioxolane compounds mainly include: γ-butyrolactone (GBL) and δ-valerolactone (NVL), and these solvents have good chemical stability and moderate polarity and can improve the solvent-electrolyte compatibility in some electrolyte systems; the cations in ionic liquid organic solvents can be selected from quaternary ammonium type, quaternary phosphonium type, imidazole type, or pyridine type, and the anions can be selected from fluorine-containing inorganic anions (such as BF4 - , PF6 - , FSI - ), or fluorine-containing organic anions (such as TFSI - ). Specific examples include but are not limited to: 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), 1-butyl-3-methylimidazolium methanesulfonate (BMIM MeSO3), 1-butyl-3-methylimidazolium trifluoroacetate (BMIM TFA), and 1-octyl-3-methylimidazolium hexafluorophosphate (OMIM PF6).

[0065] After step S103 and before step S104, a first standing treatment can also be included, in which the cell assembly is left standing at 40°C to 45°C for 36h to 72h to ensure that the first electrolyte fully infiltrates the positive electrode sheet, negative current collector, and separator in the cell assembly.

[0066] In step S104, the first formation process includes: charging the cell assembly to a state of charge (SOC) greater than or equal to 50%, such as specifically 50%, 55%, 60%, 65%, 70%, 75% or 80% at a first charging rate and a first temperature. The first charging rate is 0.01C to 0.2C, such as specifically 0.01C, 0.05C, 0.08C, 0.1C, 0.13C, 0.16C, 0.18C or 0.2C. The first temperature is 40°C to 50°C, such as specifically 40°C, 43°C, 45°C, 46°C, 48°C or 50°C.

[0067] In step S105, the mass fraction of vinylene carbonate in the second electrolyte can specifically be 5wt%, 8wt%, 10wt%, 13wt%, 18wt%, 20wt%, 24wt%, 26wt%, 28wt%, 30wt%, 33wt% or 35wt%.

[0068] The lithium salt in the second electrolyte can be selected from one or more of LiPF6, LiBF4, LiClO4, LiAsF6, LiFSI, LiTFSI, LiTFS, LiDFOB, LiBOB, LiPO2F2, LiDFOP and LiTFOP, preferably one or more of LiPF6, LiBF4, LiBOB, LiDFOB, LiTFSI and LiFSI.

[0069] The mass fraction of the lithium salt in the second electrolyte can specifically be 5wt%, 8wt%, 10wt%, 12wt%, 13wt% or 15wt%. The mass fraction of the lithium salt refers to the proportion of the mass of the lithium salt in the total mass of the second electrolyte.

[0070] The mass fraction of the electrostatic shielding additive in the second electrolyte can specifically be 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 10wt%, 13wt%, 15wt%, 18wt% or 20wt%.

[0071] The electrostatic shielding additive is selected from at least one of organic quaternary ammonium salts, metal halides or organic ionic liquids. The electrostatic shielding additive suppresses the excessive deposition tendency of lithium ions in the convex region by balancing the local electric field distribution and blocks the dendrite nucleation path.

[0072] The organic quaternary ammonium salts include tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrabutylammonium bromide (TBAB), cetyltrimethylammonium bromide (CTAB), and benzalkonium bromide; the metal halides include aluminum chloride (AlCl3), zinc chloride (ZnCl2), magnesium chloride (MgCl2), calcium chloride (CaCl2), and lithium chloride (LiCl); the organic ionic liquids include 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM(PF6)), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), 1-butyl-3-methylimidazolium methanesulfonate (BMIM MeSO3), and 1-butyl-3-methylimidazolium trifluoroacetate (BMIM TFA).

[0073] The mass fraction of the anchoring filling additive in the second electrolyte can specifically be 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 10 wt%, 13 wt%, 15 wt%, 18 wt%, or 20 wt%.

[0074] The anchoring filling additive is selected from at least one of fullerene derivatives, organosilicon compounds, or carbon-based nanomaterials. This anchoring filling additive can chemically or physically interact with lithium ions on the lithium metal surface, fill interface defects, and "anchor" the deposition of lithium ions, improving the mechanical flexibility and overall stability of the SEI film, thereby further enhancing the cycle life and safety of the lithium metal battery without a negative electrode.

[0075] Fullerene derivatives include hexanitro

[60] -fullerene (C 60 (NO2)6), carboxylated fullerene (C 60 (COOH) x ), and fluorinated fullerenes; organosilicon compounds include γ-aminopropyltriethoxysilane (APTES), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), and 3-mercaptopropyltrimethoxysilane (MPTMS); carbon-based nanomaterials include nitrogen-doped graphene, multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT), and graphene oxide (GO).

[0076] The non-aqueous organic solvents in the second electrolyte can include ether-based solvents and sulfone-based solvents, and the total mass ratio of the ether-based solvents and sulfone-based solvents to the mass of the non-aqueous organic solvents is greater than 50 wt%. Since the sulfur atom in the sulfone-based solvent is already in the highest oxidation state (S 6+), and the S=O bond has an extremely high bond energy, endowing it with excellent antioxidant stability and thermal stability. Therefore, it is regarded as a highly potential electrolyte solvent for high voltage and high temperature. Introducing sulfone-based solvents into the second electrolyte is beneficial to improving the high temperature stability of lithium metal batteries.

[0077] In some embodiments, in the second electrolyte, the mass ratio of the ether-based solvent to the sulfone-based solvent is greater than or equal to 1. That is to say, the ether-based solvent still serves as the main body of the solvent, and the sulfone-based solvent serves as the auxiliary solvent. Due to the poor compatibility between the sulfone-based solvent and lithium metal, and the problems of high melting point, high viscosity, and low wettability commonly existing in sulfone-based solvents, the practical application of sulfone-based solvents is hindered. Taking the ether-based solvent as the main body and the sulfone-based solvent as the auxiliary not only retains the characteristics of excellent compatibility with lithium metal, high conductivity, low viscosity, and low cost of the ether-based solvent, but also adds the characteristics of excellent antioxidant stability and thermal stability of the sulfone-based solvent. The combination of the two is more conducive to the long-term stable cycling of lithium metal batteries.

[0078] The non-aqueous organic solvent in the second electrolyte may also include one or more of carbonate-based organic solvents, phosphate-based organic solvents, fluorinated solvents, nitrile solvents, dioxolane solvents, and ionic liquid-based organic solvents.

[0079] After step S105 and before step S106, a second standing treatment may also be included, where the cell assembly is left standing at 40°C to 45°C for 36h to 72h to ensure that the second electrolyte is fully mixed with the first electrolyte and improve the overall uniformity of the electrolyte.

[0080] In step S106, the second formation process includes: charging the cell assembly to a charge state greater than 85% at a second charging rate and a second temperature, for example, specifically 85%, 88%, 90%, 93%, 95%, or 100%. The second charging rate is 0.2C to 0.5C, for example, specifically 0.2C, 0.25C, 0.3C, 0.35C, 0.4C, 0.45C, or 0.5C. The second temperature is 40°C to 50°C, for example, specifically 43°C, 46°C, 48°C, or 50°C.

[0081] The first charging rate in the first formation process is less than the second charging rate in the second formation process, and the first temperature in the first formation process is less than the second temperature in the second formation process, which is more conducive to the stable formation of the SEI film. In the first formation process, the rate is lower and the temperature is lower, allowing lithium ions to migrate slowly and evenly, reducing the risk of dendrites, and being conducive to the stable formation of the composite inorganic interface film. Moreover, the relatively low temperature can inhibit the side reactions of the electrolyte, promote the formation of a dense and stable solid composite inorganic interface film, improve the first Coulombic efficiency. The relatively low temperature environment is also conducive to reducing the violent reaction between lithium metal and the electrolyte, avoiding excessive growth of the composite inorganic interface film, reducing the loss of active lithium, and prolonging the cycle life. In the second formation process, the rate is higher and the temperature is higher, which can promote the penetration of the electrolyte and ion conduction, repair the defects of the inorganic interface film that may occur in the first formation, form a more uniform flexible organic interface layer, and the relatively high temperature can accelerate the activation of the electrode material, shortening the aging time. The relatively high rate can activate the deep active substances of the electrode, improving the capacity utilization.

[0082] In some embodiments, the mass of the first electrolyte accounts for 65wt% - 90wt% of the total mass of the electrolyte. For example, specifically, it can be 65wt%, 70wt%, 75wt%, 80wt%, 85wt% or 90wt%. If the injection volume of the first electrolyte is insufficient, the cell assembly may not be fully infiltrated, and lithium deposition is likely to occur after formation. If the injection volume of the first electrolyte is too large, it may lead to too high a concentration of additives in the second electrolyte, resulting in uneven distribution of additives inside the cell assembly. Preferably, the mass of the first electrolyte accounts for the total mass of the electrolyte in the range of 70wt% - 90wt%.

[0083] According to some embodiments of the present application, on the other hand, the present application also provides a lithium metal battery prepared by using the manufacturing method of the lithium metal battery in the above embodiments.

[0084] According to some embodiments of the present application, on another aspect, the present application also provides an electrical device. The electrical device includes the lithium metal battery and a load in the above embodiments; or, the electrical device includes an energy storage system and a load, and the energy storage system includes multiple lithium metal batteries in the above embodiments.

[0085] The lithium metal battery, its manufacturing method, and the electrical device provided by the embodiments of the present application construct an inorganic-organic composite interface layer by injecting electrolyte in stages and dynamically regulate lithium deposition behavior during the manufacturing method. The first injection forms a rigid composite inorganic interface layer, and the second injection superimposes a flexible organic layer and introduces functional additives, systematically solving the problems of interface stability and lithium dendrite growth. Based on the interface dynamic requirements of the anode-free lithium metal battery, the first injection focuses on constructing a highly stable composite inorganic interface layer to reduce the initial side reaction activity; the second injection continuously optimizes the deposition behavior and repairs interface defects through a flexible organic film and a dynamic regulation dual path. The collaborative design of the two-step process takes into account both the rigid support and dynamic adaptability of the interface, providing double guarantees for long cycle stability and high rate performance.

[0086] In the first electrolyte injection process, a first electrolyte including lithium polysulfide (Li2S8), lithium nitrate (LiNO3), a lithium salt, and a non-aqueous organic solvent is injected into the battery cell assembly, and then a first formation process is carried out. The complementary characteristics of lithium polysulfide and lithium nitrate are utilized to form a composite inorganic interface layer. The sulfide layer (Li2S) generated by Li2S8 has high mechanical brittleness and is prone to cracking due to stress concentration; although the nitride layer (Li3N) formed by LiNO3 has excellent chemical stability, it has poor adaptability to volume expansion. Through the synergistic effect of Li2S8 and LiNO3, a Li2S-Li3N cross-linked structure is formed by means of a sulfur-nitrogen composite mechanism, which has both high ionic conductivity and mechanical toughness, can not only inhibit the decomposition of the electrolyte, but also provide a stable foundation for subsequent cycles. In the second electrolyte injection process, a second electrolyte including fluoroethylene carbonate (FEC), a lithium salt, an electrostatic shielding additive, an anchoring filling additive, and a non-aqueous organic solvent is injected into the battery cell assembly, and then a second formation process is carried out. A flexible organic layer is generated by the decomposition of FEC and covers the surface of the composite inorganic interface layer to relieve the stress impact caused by volume changes. Its dynamic repair characteristics can adapt to the stress changes caused by the volume expansion / contraction of lithium metal and reduce the risk of interface film rupture. An electrostatic shielding additive and an anchoring filling additive are also introduced in the second electrolyte injection process. The electrostatic shielding additive releases high-valent cations to neutralize the local electric field distortion in the convex region of lithium deposition, balance the local electric field distribution, inhibit the excessive deposition tendency of lithium ions in the convex region, and block the dendrite nucleation path and thus block the growth of the dendrite tip; the anchoring filling additive preferentially guides lithium ions to form a dense lithium layer in the interface concave region through defect site adsorption and directional deposition guidance, promoting the uniformity of the deposition morphology. The electrostatic shielding additive is used to inhibit the tip effect, and the anchoring filling additive is used to repair interface defects. The electrostatic shielding additive and the anchoring filling additive synergistically guide the directional deposition of lithium ions through physical confinement and chemical bonding to repair micro-defects, not only achieving the uniformity of lithium deposition morphology, but also reducing the interface impedance and optimizing the ion transport kinetics. The synergistic effect of the electrostatic shielding additive and the anchoring filling additive breaks through the limitation of a single type of additive that only regulates local deposition, reduces the interface impedance and optimizes the lithium ion transport kinetics through a complementary mechanism, thereby improving the cycle stability of the lithium metal battery at high rates.

[0087] The following are specific embodiments of the present application.

[0088] Table 1 shows the formulations of the first electrolyte and the second electrolyte corresponding to various embodiments provided in the embodiments of the present application. Among them, N-1 corresponds to the formulation of the first electrolyte, and N corresponds to the embodiment number; M-2 corresponds to the formulation of the second electrolyte, and M corresponds to the embodiment number.

[0089] Table 1

[0090] Continued Table 1

[0091] DOL is 1,3 - dioxolane (a non - aqueous organic solvent); DME is dimethoxyethane (a non - aqueous organic solvent); EMS is ethyl methanesulfonate (a non - aqueous organic solvent); LiPF6 is lithium hexafluorophosphate (a lithium salt); LiTFSI is lithium bis(trifluoromethanesulfonyl)imide (a lithium salt); Li2S8 is lithium octasulfide (a polysulfide); LiNO3 is lithium nitrate; FEC is fluoroethylene carbonate; CsPF6 is cesium hexafluorophosphate (an electrostatic shielding additive); AlCl3 is aluminum chloride (an electrostatic shielding additive); C 60 (NO2)6 is hexanitro

[60] fullerene (an anchoring and filling additive).

[0092] In Table 1, the solvents are shown as the percentage of the total mass of the solvents, and the remaining lithium salts and additives are in terms of the mass percentage of the overall formulation. For example, in Example 17, taking the mass of the first electrolyte as 100 g, the mass calculation method for each component in the first electrolyte is as follows: the mass of LiPF6 is 8%×100 g = 8 g, the mass of LiTFSI is 5%×100 g = 5 g, the mass of Li2S8 is 2%×100 g = 2 g, the mass of LiNO3 is 2%×100 g = 2 g, the total mass of the solvents is (100 g - mass of additives - mass of lithium salts)=(100 g - 8 g - 5 g - 2 g - 2 g)=83 g, then the mass of DOL in the first electrolyte is 83 g×50% = 41.5 g, and the mass of DME in the first electrolyte is 83 g×50% = 41.5 g; taking the mass of the second electrolyte as 100 g, the calculation method for each component in the second electrolyte is as follows: the mass of LiPF6 is 8%×100 g = 8 g, the mass of LiTFSI is 5%×100 g = 5 g, the mass of FEC is 33.3%×100 g = 33.3 g, the mass of AlCl3 is 33.3%×100 g = 33.3 g, C 60 (NO2)6's mass is 0.3%×100 g = 0.3 g, the total mass of the solvents is (100 g - mass of additives - mass of lithium salts)=(100 g - 8 g - 5 g - 33.3 g - 33.3 g - 0.3 g)=20.1 g, then the mass of DOL in the second electrolyte is 20.1 g×50% = 10.05 g, and the mass of DME in the second electrolyte is 20.1 g×50% = 10.05 g. The calculation methods for the first electrolyte or the second electrolyte in other examples are the same and will not be elaborated one by one.

[0093] In Examples 1 to 18, the injection ratio of the first electrolyte and the second electrolyte used is 85:15.

[0094] The lithium metal batteries corresponding to Examples 1 to 18 were prepared by the following method.

[0095] S201. Provide a positive electrode sheet, a negative electrode current collector, and a separator. The positive electrode sheet includes an aluminum foil and a positive electrode material layer covering the aluminum foil. The positive electrode material layer is composed of lithium iron phosphate, conductive agent SuperP, carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) with a mass ratio of 95.8:1:0.7:2.5; the negative electrode current collector is a copper foil; the separator is a PP separator.

[0096] S202. After winding the positive electrode sheet, the negative electrode current collector, and the separator, place them into an aluminum-plastic film housing of the shell, and bake to remove moisture to form a battery cell assembly.

[0097] S203. Perform a first electrolyte injection process on the battery cell assembly, and inject a first electrolyte into the battery cell assembly. The components of the first electrolyte refer to Table 1.

[0098] S204. After standing the battery cell assembly at 45 °C for 36 h, perform a first formation process on the battery cell assembly. Charge the battery cell assembly at a rate of 0.05C until the state of charge (SOC) reaches 50%, then discharge it, with an upper limit voltage of 3.65V and a temperature of 40 °C.

[0099] S205. Perform a second electrolyte injection process on the battery cell assembly, and inject a second electrolyte into the battery cell assembly. The components of the second electrolyte refer to Table 1.

[0100] S206. After standing the battery cell assembly at 45 °C for 36 h, perform a second formation process on the battery cell assembly. Charge the battery cell assembly at a rate of 0.3C until the state of charge (SOC) reaches 85%, then discharge it, with an upper limit voltage of 3.65V and a temperature of 45 °C.

[0101] The lithium metal batteries of each example were tested for the cycle capacity retention rate at 25 °C and the cycle capacity retention rate at 45 °C. The test results are shown in Table 2.

[0102] Table 2

[0103] (1) 25 °C cycle capacity retention rate test: At 25 °C, charge the lithium metal battery at a constant current of 0.5C / 1.5C to the upper limit voltage, then charge at a constant voltage until the current is 0.05C, and then discharge at a constant current of 0.5C / 1.5C to the lower limit voltage. Perform 200 cycles of charge and discharge tests. Record the first-week efficiency, the cycle capacity retention rate at the 100th cycle, and the cycle capacity retention rate at the 200th cycle. The capacity retention rate at the nth cycle = (the discharge capacity at the nth cycle / the first discharge capacity) × 100%, and the first-week efficiency (%) = (the discharge capacity of the first cycle / the charge capacity of the first cycle) × 100%.

[0104] (2)45°C Cycling Capacity Retention Test: At 45°C, charge the lithium metal battery to the upper limit voltage at a constant current of 0.5C / 1.5C respectively, then charge at a constant voltage until the current is 0.05C, and then discharge at a constant current of 0.5C / 1.5C to the lower limit voltage respectively. Conduct 200 cycles of charge and discharge tests. Record the first-week efficiency, the cycling capacity retention rate at the 100th cycle, and the cycling capacity retention rate at the 200th cycle. The capacity retention rate at the nth cycle = (discharge capacity at the nth cycle / first discharge capacity) × 100%, and the first-week efficiency (%) = (discharge capacity of the first cycle / charge capacity of the first cycle) × 100%.

[0105] Through key indicators such as the normal-temperature cycling capacity retention rate, high-temperature cycling capacity retention rate, and first-week efficiency at different rates of 0.5C and 1.5C, the effects of electrolyte formulation and liquid injection method on battery performance can be deeply explored.

[0106] In the normal-temperature cycling and high-temperature cycling tests at 0.5C and 1.5C, the comparison results of Example 1 and Example 2 show that the addition of additives significantly improves the capacity retention rate and first-week efficiency under normal-temperature and high-temperature conditions. After LiNO3 is reduced on the lithium metal surface, a nitrogen-containing inorganic passivation layer (such as Li3N and LiN x O y ) is formed, enhancing the mechanical strength and chemical stability of the interface, and reducing the side reaction rate between the electrolyte and metallic lithium. Li2S8 decomposes at the interface to form sulfides (such as Li2S), constructing an inorganic protective layer with low solubility and high lithium conductivity, improving the interfacial ion transport performance and suppressing side reactions. At the same time, FEC decomposes on the lithium surface to form fluorine-rich compounds (such as LiF), and its high mechanical toughness and chemical stability can effectively block electron transport and prevent the continuous decomposition of the electrolyte. The three work together to form a composite SEI film of Li3N / LiN x O y 、Li2S and LiF, guiding uniform lithium deposition, inhibiting dendrite growth, reducing interfacial impedance, and significantly improving the Coulomb efficiency and cycle life.

[0107] Overall data shows that the capacity retention rate of the lithium metal battery without a negative electrode is better under high-temperature cycling than under normal-temperature conditions, while the increase in rate leads to a decrease in the capacity retention rate. This is because high temperature reduces the viscosity of the electrolyte, increases the ion diffusion rate, and promotes the formation of a more uniform and stable SEI film, thus improving the cycling performance. At high rates, due to insufficient local lithium ion supply and too fast deposition rate, it is easy to cause uneven lithium deposition and dendrite growth, thus reducing the cycling stability.

[0108] Comparing Example 2 to Example 8, the secondary injection method is superior to the primary injection method in terms of various performance indicators, but the usage order and combination of different additives affect the final performance. The formulation of Example 6 (Li2S8 and LiNO3 in the first electrolyte, and FEC in the second electrolyte) exhibits the best cycle capacity retention rate and first-week efficiency at different temperatures and rates.

[0109] Inorganic film-forming additives Li2S8 and LiNO3 construct an initial stable inorganic SEI layer through a sulfur-nitrogen composite passivation mechanism during the first charge and discharge stages. Li2S8 reacts with lithium metal in the electrolyte to generate sulfides such as Li2S and Li2S2, which are embedded in the SEI film, enhancing its mechanical toughness and chemical stability. LiNO3 is preferentially reduced on the lithium surface to form an inorganic passivation layer mainly composed of Li3N and LiN x O y with high ionic conductivity, which can promote the uniform deposition of lithium ions, reduce the local current density, and inhibit dendrite growth. In addition, the dynamic sulfur compensation effect of Li2S8 can repair SEI cracks, while the oxidation products of LiNO3 (such as LiNO2) can inhibit the generation of "dead lithium", improve the first Coulomb efficiency, and ensure the initial interface stability of the battery.

[0110] During long cycling, the introduction of the organic film-forming additive FEC, whose decomposed flexible polymer layer enhances the anti-swelling ability of the SEI, prevents the rupture of the interfacial film, and reduces side reactions. In addition, FEC regulates the solvation sheath structure, increases the anion coordination number, reduces the lithium-ion desolvation energy barrier, and improves the uniformity and reversibility of lithium deposition. Through the inorganic-organic staged film-forming strategy, the SEI structure is stably constructed in the initial stage and dynamically repaired during long cycling, significantly improving the interfacial stability, Coulomb efficiency, and cycle life of the battery.

[0111] The comparative data of Example 6, Example 9, Example 10, Example 11, and Example 12 show that the electrostatic shielding additives CsPF6 and AlCl3 significantly improve the battery performance, and their addition effect in the second electrolyte is better than that in the first electrolyte. This may be because the electrolytes of secondary injection mainly exist in the free state, and the introduction of electrostatic shielding additives at this time can more effectively regulate the local electric field distribution and ion transport environment. These additives form a positive charge shielding layer in the lithium deposition protrusion area, inhibiting the excessive deposition of local lithium ions and subsequent dendrite growth.

[0112] The comparison between Example 12 and Example 13 shows that the use of two electrostatic shielding additives with similar mechanisms (such as CsPF6 and AlCl3) has little difference in the final effect compared to using only one of them. When one additive has reached the regulation saturation state, further adding another additive with a similar action mechanism will not significantly enhance the overall effect. This indicates that there is a "saturation point" for the electrostatic shielding effect, and additional addition beyond this concentration will not bring additional performance improvement. Therefore, in battery design, the type and dosage of electrostatic shielding additives can be appropriately selected according to specific performance requirements and system characteristics, without pursuing diversification of additive types or over-addition.

[0113] The comparative data of Example 6, Example 14, and Example 15 show that the addition of the anchoring filling additive C 60 (NO2)6 also significantly improves battery performance, and its use effect in the second electrolyte is better than that in the first electrolyte.

[0114] C 60 The action mechanism of C(NO2)6 stems from the spatial confinement effect of its rigid fullerene skeleton and the dynamic chemical adaptation characteristics of the surface nitro groups. Its spherical skeleton preferentially adsorbs on the microscopic concave regions of the electrode surface through van der Waals forces, forming a physical barrier at the nanoscale, promoting the deposition of lithium ions in the low-curvature regions, thereby inhibiting dendrite growth. At the same time, its nitro groups (-NO2) form directional chemical bonds with the unpaired electrons on the lithium metal surface, anchoring at active sites such as grain boundary defects or dislocations, inhibiting local lithium ion aggregation. During the cycling process, the nitro groups undergo a reduction reaction (-NO2 → -NHO → -NH2), accompanied by electron release, in-situ repairing the SEI film, and at the same time, the generated amino groups (-NH2) enhance the lithium ion affinity of the interface layer, promoting uniform lithium deposition.

[0115] Under the secondary injection strategy, a high-modulus substrate has been formed by the inorganic SEI skeleton (the synergistic effect of Li2S8 / LiNO3) during the first film-forming stage. At this time, C(NO2)6 in the second electrolyte can migrate to the interface dynamic defects (such as the deposition front or stress cracks) through the concentration gradient, and through the synergistic effect of physical filling and chemical bonding, achieve "defect recognition - in-situ repair - structure strengthening" during the SEI maturation stage, thereby optimizing the interface stability. 60 (NO2)6 can migrate to the interface dynamic defects (such as the deposition front or stress cracks) through the concentration gradient, and through the synergistic effect of physical filling and chemical bonding, achieve "defect recognition - in-situ repair - structure strengthening" during the SEI maturation stage, thereby optimizing the interface stability.

[0116] The data of Example 16 and Example 17 show that the combined use of electrostatic shielding additives and anchoring filling additives in the second electrolyte can achieve the best performance, especially under high-rate conditions, the cycle attenuation is significantly slowed down.

[0117] The synergistic optimization of the two types of additives is based on cross-scale dynamic interface regulation. The electrostatic shielding additive forms a dynamic potential buffering effect through high-valent cations, weakening the local electric field distortion at the electrode / electrolyte interface at the mesoscopic scale, inhibiting the non-uniform distribution of lithium-ion flux at high rates, and reducing the kinetic driving force for dendrite nucleation. The anchoring and filling additive, by virtue of the rigid confinement effect of fullerene derivatives and the dynamic response characteristics of functional groups, optimizes the lithium deposition path and repairs SEI film damage at the microscopic scale. The synergy between the two is reflected in "time-space two-dimensional regulation": during instantaneous current impact, the electrostatic shielding additive guides lithium ions to diffuse to low-energy sites; during continuous deposition, the anchoring and filling additive dynamically repairs interface cracks and promotes uniform deposition. This synergistic mechanism optimizes the uniformity of lithium deposition morphology and the stability of the interface structure, significantly reducing the capacity decay rate caused by local lithium depletion under high-rate conditions.

[0118] The data of Example 18 show that after introducing an appropriate amount of sulfone-based solvent into the second electrolyte, the high-temperature cycling performance of the lithium metal battery is improved.

[0119] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present application, and in actual applications, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should be determined by the scope defined in the claims.

Claims

1. A manufacturing method of a lithium metal battery, characterized in that, Comprising: Providing a positive electrode sheet, a negative electrode current collector, and a separator, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer; After winding or laminating the positive electrode sheet, the negative electrode current collector, and the separator, placing them into a housing to form an electrode core assembly, with the separator located between the positive electrode sheet and the negative electrode current collector; Performing a first electrolyte injection process on the electrode core assembly, injecting a first electrolyte into the electrode core assembly, and the components of the first electrolyte include: 0.1 wt% - 5 wt% of lithium polysulfide, 0.1 wt% - 5 wt% of lithium nitrate, 5 wt% - 15 wt% of a lithium salt, and the balance of a non-aqueous organic solvent; Performing a first formation process on the electrode core assembly; Performing a second electrolyte injection process on the electrode core assembly, injecting a second electrolyte into the electrode core assembly, and the components of the second electrolyte include: 5 wt% - 35 wt% of fluoroethylene carbonate, 5 wt% - 15 wt% of a lithium salt, 0.05 wt% - 20 wt% of an electrostatic shielding additive, 0.05 wt% - 20 wt% of an anchoring filling additive, and the balance of a non-aqueous organic solvent; Performing a second formation process on the electrode core assembly.

2. The manufacturing method of the lithium metal battery according to claim 1, wherein, The non-aqueous organic solvent in the first electrolyte includes an ether-based solvent, and the mass ratio of the ether-based solvent to the non-aqueous organic solvent is greater than 50 wt%.

3. The manufacturing method of the lithium metal battery according to claim 1 or 2, characterized in that, The non-aqueous organic solvent in the second electrolyte includes an ether-based solvent and a sulfone-based solvent, and the total mass ratio of the ether-based solvent and the sulfone-based solvent to the non-aqueous organic solvent is greater than 50 wt%.

4. The manufacturing method of the lithium metal battery according to claim 3, characterized in that, In the second electrolyte, the mass ratio of the ether-based solvent to the sulfone-based solvent is greater than or equal to 1.

5. The manufacturing method of a lithium metal battery according to claim 1, wherein The first formation process includes: charging the electrode core assembly to a state of charge greater than or equal to 50% at a first charging rate and a first temperature; The second formation process includes: charging the electrode core assembly to a state of charge greater than 85% at a second charging rate and a second temperature; Wherein, the first charging rate is less than the second charging rate, and the first temperature is less than the second temperature.

6. The manufacturing method of the lithium metal battery according to claim 5, characterized in that, The first charging rate is 0.01C - 0.2C; the second charging rate is 0.2C - 0.5C; the first temperature is 40°C - 50°C; the second temperature is 40°C - 50°C.

7. The manufacturing method of the lithium metal battery according to claim 1, characterized in that, The anchoring filling additive is selected from at least one of fullerene derivatives, organosilicon compounds, or carbon-based nanomaterials.

8. The manufacturing method of a lithium metal battery according to claim 1, characterized in that, The electrostatic shielding additive is selected from at least one of organic quaternary ammonium salts, metal halides, or organic ionic liquids.

9. The manufacturing method of the lithium metal battery according to claim 1, wherein The negative electrode current collector is selected from one of copper foil, nano-coated copper, copper foam, copper mesh, metal-carbon composite current collector, or lithium-inserted alloy-based current collector.

10. The manufacturing method of the lithium metal battery according to claim 1, characterized in that, The material of the positive electrode material layer includes at least one of layered oxide materials, spinel structure materials, polyanion materials, lithium-rich manganese-based materials, transition metal fluoride materials, or organic materials.

11. A lithium metal battery, characterized in that, Prepared by using the manufacturing method of a lithium metal battery according to any one of claims 1 - 10.

12. An electrical device, characterized in that, The electrical device includes the lithium metal battery as described in claim 11 and a load; or, the electrical device includes an energy storage system and a load, and the energy storage system includes a plurality of lithium metal batteries as described in claim 11.

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