Solid electrolyte interface layer for lithium metal negative electrode and plasma in-situ construction method and application of solid electrolyte interface layer

Abstract

The invention belongs to the technical field of lithium ion batteries, and relates to a solid electrolyte interface layer for a lithium metal negative electrode and a plasma in-situ construction method and application of the solid electrolyte interface layer. The core of the method is that an organic-inorganic-alloy component precursor is adopted as a plasma reaction source, a plasma reaction is carried out on the surface of lithium metal by regulating and controlling the mixing ratio and reaction conditions, and an organic-inorganic-alloy composite artificial solid electrolyte interface layer with a unique gradient layered structure can be constructed in situ. The outer layer of the solid electrolyte interface layer is a flexible organic phase, the middle layer is a rigid inorganic fast ion conductor, and the inner layer is a lithium-loving alloy phase, so that the growth of lithium dendrites can be synergistically inhibited, and the interface stability of a lithium metal negative electrode is remarkably improved. Meanwhile, the preparation method provided by the invention is simple, rapid, efficient, environment-friendly, mild in condition and easy to control, the cycling stability and coulombic efficiency of the lithium metal negative electrode are remarkably improved, and the development of a high-energy-density lithium metal battery is favorably promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium metal battery negative electrode interface modification, and in particular to a solid-state electrolyte interface layer for a lithium metal negative electrode and a method for constructing the same in situ by plasma, and application of the same in the field of lithium metal batteries. BACKGROUND

[0002] In view of the rigid demand of device-level energy density ≥ 400 Wh kg -1 for electric transportation and aerospace equipment, the current lithium ion battery system with graphite as the negative electrode has approached the theoretical ceiling and is difficult to meet the mileage anxiety of > 500 km for long-endurance unmanned aerial vehicles, high-altitude pseudo-satellites and the next generation of electric vehicles. In comparison, the lithium metal negative electrode, with an ultra-high theoretical specific capacity of 3860 mAh g -1 (10 times that of graphite), the lowest electrochemical potential (–3.04 V vs. SHE), and the additional mass / volume redundancy of the omitted carbon / silicon host, can effectively increase the negative electrode level capacity to > 3000 mAh g -1 , and theoretically make the full battery energy density jump to > 500 Wh kg -1 , and is considered as the “ultimate negative electrode” to break through the energy density bottleneck of the existing energy storage system. However, the lithium metal negative electrode faces several great challenges in its practical application: ① high activity leading to uncontrollable dendrites; ② high volume expansion (≈80 %) inducing interface pulverization; ③ high interface side reactions continuously consuming active lithium; ultimately leading to low coulombic efficiency (<99 %) and short cycle life. Therefore, it is urgent to optimize and upgrade the lithium metal negative electrode from the atomic level interface chemistry or macroscopic three-dimensional structure to achieve the harsh balance of energy density and cycle life of the lithium metal negative electrode.

[0003] Currently, the modification methods for lithium metal mainly include: artificial solid-state electrolyte interface engineering, three-dimensional current collector / host structure construction strategy, etc. Among them, the artificial solid-state electrolyte interface engineering is mainly to pre-construct a layer of “ion fast, electron slow, mechanically tough, chemically inert” multifunctional interface on the surface of lithium metal, which can not only provide a stable and smooth ion transport channel for Li +The low-barrier transmission channel is provided, the flux is homogenized, the high Young's modulus physically blocks the dendrite penetration, the wide-bandgap inorganic layer cuts off the electron tunneling, the decomposition of the electrolyte is inhibited, and the interface integrity is maintained. The three-dimensional current collector / host structure construction strategy realizes the uniform deposition and stripping of lithium by adjusting the lithium ion nucleation site and reducing the local current density, thereby inhibiting the growth of lithium dendrites. However, the three-dimensional current collector / host construction strategy has high process threshold, low yield, high cost of equipment and materials, and actual energy density reduction caused by the introduction of non-active substances, and other problems, and it is difficult to leave the laboratory. Compared with the three-dimensional current collector / host construction strategy, the artificial solid electrolyte engineering directly reconstructs the interface at the atomic-molecular scale, and can provide a high Young's modulus (> 6 GPa) to inhibit the growth of lithium dendrites, a faster lithium ion transmission channel (10 -4 S cm -1 ) to realize the uniform deposition of lithium ions, and does not introduce additional host mass, thereby ensuring the high energy density advantage of the lithium metal battery. However, the existing strategies for constructing the artificial solid electrolyte interface have the disadvantages of complex preparation process, long time consumption, high cost, great environmental pressure, and poor stability, which leads to the lithium metal negative electrode not reaching the ideal performance index and moving towards large-scale application. For example, the solution coating, vapor deposition and other methods cannot control the uniformity of the nanoscale film thickness, and too thick will significantly increase the interface impedance and reduce the energy density, and too thin will result in insufficient mechanical strength, leading to local rupture at the later stage of the cycle. ALD requires high vacuum, high temperature or special precursors, and the equipment investment is large; the spin coating, immersion and other wet processes are simple, but are affected by the wettability of the substrate, the evaporation rate of the solvent, and the thickness and composition fluctuate greatly between batches.

[0004] Therefore, the present application provides a mild and efficient interface modification method for a lithium metal negative electrode, which uses advanced low-temperature plasma technology to construct an artificial solid electrolyte interface on the surface of the lithium metal in situ. This technology can construct the composition, structure, and physical and chemical properties of the artificial solid electrolyte interface according to the target requirements, and has universality and expandability. At the same time, the preparation temperature of the artificial solid electrolyte interface constructed by this method is relatively low, usually less than 100 DEG C, and the reaction time is short, usually less than one minute, which greatly improves the preparation efficiency. Since the whole process does not require high-temperature sintering and does not leave solvent residues, it provides a new paradigm for interface engineering with great expandability for the large-scale and green manufacturing of lithium metal negative electrodes. SUMMARY

[0005] The application aims at the problems of high complexity, poor stability, high cost and long time in the prior art surface modification process of lithium metal negative electrode, and provides a solid-state electrolyte interface layer for lithium metal negative electrode and a plasma in-situ construction method and application thereof.

[0006] The technical scheme adopted by the application to solve the technical problems is: The application provides a plasma in-situ construction method for a solid-state electrolyte interface layer of a lithium metal negative electrode, which is constructed in-situ on the surface of an air-sensitive lithium metal by using an organic-inorganic-alloy component precursor as a reaction source and combining a low-pressure and low-temperature plasma technology, so as to construct an artificial solid-state electrolyte interface layer with an organic-inorganic-alloy gradient layer.

[0007] By adopting the technical scheme: the application adopts advanced low-temperature plasma technology, selects a specific reaction source for surface modification of air-sensitive lithium metal, thereby obtaining a unique high-performance artificial solid-state electrolyte interface layer, and according to the selection of the reaction source, different interface layers such as organic, organic-inorganic composite, inorganic-alloy composite and the like can be obtained, and even through a composite reaction source, an organic-inorganic-alloy gradient layered composite artificial solid-state electrolyte interface layer with better performance and no related reports can be obtained. The outer layer of the solid-state electrolyte interface layer is a flexible organic phase, the middle layer is a rigid inorganic fast ion conductor, and the inner layer is a lithiumophilic alloy phase, which can synergistically inhibit lithium dendrite growth and significantly improve the interface stability of the lithium metal negative electrode. And by further adjusting the component ratio of the reaction source, the reaction temperature, the vacuum degree of the cavity, the radio frequency discharge power and the time and the like, the artificial solid-state electrolyte interface layer required can be flexibly prepared, the method has a wide selection range of the reaction source, is simple, efficient and environmentally friendly, and can be extended to surface modification of other air-sensitive materials. At the same time, through the selection of the reaction source and the optimization of the process parameters, the modification interface ion transmission kinetics can be synergistically enhanced, the Young's modulus can be improved, and the ion nucleation potential barrier can be reduced, so that the lithium ion can be uniformly nucleated and horizontally grown, thereby inhibiting the formation of lithium dendrites and prolonging the cycle life of the lithium metal battery. The application is helpful for promoting the practical process of high-energy-density lithium metal batteries.

[0008] Preferably, the air-sensitive lithium metal used is a commercial lithium metal sheet, and can be further extended to other air-sensitive / air-stable materials, such as sodium, potassium, aluminum, magnesium, zinc, iron, copper, tin foil and the like, as well as carbon cloth, carbon nanotubes, graphene, graphene sponge, polyimide film, polyacrylonitrile film, various MOF materials and the like.

[0009] Preferably, the reaction source can be selected as a single compound or two or more compounds in any ratio; more preferably, the reaction source organic-inorganic-alloy component precursor includes an organic source and an inorganic metal compound source, the organic source is selected from at least one of benzene, trifluorotoluene and perfluorohexane; the inorganic metal compound source is selected from at least one of anhydrous tin tetrachloride, anhydrous titanium tetrachloride, anhydrous silicon tetrachloride, anhydrous molybdenum chloride and anhydrous vanadium chloride. More preferably, the molar ratio of the organic source to the inorganic metal compound source is 1:0.5-10, more preferably 1:1-5. More preferably, the reaction source is a mixed solution of trichlorotoluene and anhydrous tin tetrachloride with a molar ratio of 1:3-5.

[0010] Preferably, the low pressure in the low-pressure low-temperature plasma technology is 10 Pa-50 Pa. The reaction source used in the application is easy to vaporize or volatilize under the low vacuum condition, so as to easily enter the reaction cavity in the form of steam for reaction. More preferably, the vacuum degree of the application is 20 Pa.

[0011] Preferably, the low temperature in the low pressure low temperature plasma technology is 20-100℃, more preferably room temperature. The selected reaction source in the present application can enter the reaction cavity for reaction at low temperature or even room temperature, without heating; but the low temperature condition with heating can be more conducive to the reaction. The balance between energy and reaction efficiency can be made according to the actual situation.

[0012] Preferably, the plasma radio frequency power in the low pressure low temperature plasma technology is 30-500W, and the after-glow reaction time is 30-300s. More preferably, the radio frequency power is 100W, and the reaction time is 60s.

[0013] Preferably, the method specifically comprises the following steps: (1) Under the protection of inert atmosphere, air-sensitive lithium metal is transferred to the plasma reaction cavity and sealed, and the reaction source is added to the reaction source bottle and sealed; (2) The reaction source bottle, plasma reaction cavity and vacuum system are connected in turn, the vacuum system and the feeding valve of the reaction source bottle are started, the background vacuum degree in the cavity is dynamically stabilized to the vacuum intensity of the process vacuum window required for reaction by closed loop vacuum system, and the dynamic balance of feeding and discharging is realized; (3) The radio frequency power supply is turned on, and the plasma reaction cavity can be heated to an appropriate temperature, the plasma radio frequency power and discharge time are adjusted, and an artificial solid-state electrolyte interface with organic-inorganic-alloy gradient layered structure is obtained on the surface of lithium metal.

[0014] Preferably, in step (1), the inert atmosphere is at least one of argon, nitrogen, helium, argon-hydrogen mixed gas, nitrogen-hydrogen mixed gas and helium-hydrogen mixed gas.

[0015] Based on the above, the present application also provides a lithium metal negative electrode solid-state electrolyte interface layer obtained by the above-mentioned any one plasma in-situ construction method.

[0016] Based on the above, the present application also provides an application of the above-mentioned lithium metal negative electrode solid-state electrolyte interface layer in lithium metal battery.

[0017] Compared with the prior art, the present application has the following beneficial effects: (1) The application adopts low-temperature plasma technology to construct a layer of artificial solid electrolyte interface with adjustable component structure on the surface of lithium metal in situ, and can be effectively applied in lithium metal batteries. Taking a mixed solution of trifluorotoluene and anhydrous tin tetrachloride as a liquid reaction source as an example, the mixed steam of trifluorotoluene and anhydrous tin tetrachloride is extracted into the reaction cavity by a vacuum system, and then the mixed steam is dissociated into a large number of active groups by a radio frequency power supply. The active groups and ions with different masses and energies bombard the surface of lithium metal under the action of electric field force. Since the internal energy of different ions or active groups is different, the immersion depth in the lithium sheet surface is different, thereby forming an artificial solid electrolyte layer with an organic-inorganic-metal composite gradient layered structure. The outer layer of the solid electrolyte interface layer is a flexible organic phase, the middle layer is a rigid inorganic fast ion conductor, and the inner layer is a lithiumophilic alloy phase, which can synergistically inhibit lithium dendrite growth and significantly improve the interface stability of the lithium metal negative electrode. The gradient structure is determined by the surface treatment of the plasma technology and the unique properties of the special reaction source. The flexible organic component of the outermost layer of the constructed artificial solid electrolyte layer helps to relieve the volume expansion generated during the lithium deposition stripping process, release the interfacial stress, and prevent the rupture of the solid electrolyte layer caused by the volume change of the electrode. The inorganic-rich component in the middle layer acts as a rigid skeleton, enhancing the mechanical strength of the artificial solid electrolyte interface. At the same time, a large number of grain boundaries provide a fast transmission channel for lithium ions, and uniform lithium flux. The innermost alloy layer acts as a lithiumophilic site, reducing the nucleation barrier of lithium ions, regulating the nucleation and growth behavior of lithium ions, and inhibiting the uncontrollable growth of lithium dendrites. Under the synergistic action of multiple components, it is beneficial to improve the cycle life of the lithium metal negative electrode and increase the coulombic efficiency, and it is helpful to promote the practical development of high-energy-density lithium metal batteries.

[0018] (2) The application proposes a method for constructing an artificial solid electrolyte interface by low-temperature plasma assisted method. This method is a controllable method for constructing an artificial solid electrolyte interface. Through the pre-design of precursor chemical composition, functional group sequence and reaction path, an organic-inorganic-alloy hybrid SEI with preset stoichiometric ratio, layered / gradient / three-dimensional topological structure and target physical and chemical parameters can be grown on the surface of lithium metal negative electrode under mild conditions of ≤100 ℃ and ≤300 s. The method has directionality, universality and expandability, and is a new technology with continued development and exploration value.

[0019] (3) The application is based on plasma-induced in-situ construction of artificial solid-state electrolyte interface, which can realize second-level film formation at room temperature or low temperature, and does not require solvent and post-processing in the whole preparation process, and the experimental process is extremely simple and efficient. Therefore, the plasma-assisted preparation of artificial solid-state electrolyte interface technology has broad application prospects in high-end application scenarios such as energy storage batteries, flexible electronics, electric vehicles, distributed energy and deep space exploration. At the same time, the preparation method provided by the application is simple, rapid, efficient and environmentally friendly, and the conditions are mild and easy to control, which significantly improves the cycle stability and coulombic efficiency of the lithium metal anode, and helps to promote the development of high-energy density lithium metal batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a schematic diagram of the plasma reaction device in the application; Figure 2 It is a scanning electron microscope morphology comparison diagram of pure lithium sheet, example 8, comparative example 1 and example 6; Figure 3 It is a high-resolution transmission electron microscope photo and corresponding EDS element distribution diagram of example 6; Figure 4 It is an XPS diagram of example 6 before and after etching for 300s; Figure 5 It is a time-of-flight secondary ion mass spectrum diagram of example 6; Figure 6 It is a long cycle stability comparison diagram of pure lithium sheet, comparative example 1 and example 6 under the condition of 1 mA cm -2 Current density, the deposition stripping capacity is 1 mAh cm -2 Symmetrical battery. DETAILED DESCRIPTION

[0021] For the convenience of understanding, the technical solutions and embodiments of the application will be further clearly, completely and specifically described and explained below by means of specific embodiments and in combination with the drawings. It should be known that the embodiments described in the application are implemented on the premise of the technical solutions of the application, and detailed embodiments and specific operation processes are given, but only part of the embodiments of the application, not all the embodiments. The specific embodiments described are limited to explaining and interpreting the application, and do not limit the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0022] The experimental methods and conditions used in the following examples are conventional methods and conventional conditions unless otherwise specified. The materials, reagents or apparatuses and equipment used in the examples are conventional materials or equipment known to those skilled in the art and can be obtained commercially unless otherwise specified. The reaction conditions embodied in the summary of the application can achieve the reaction and obtain the expected product. Due to the limitation of the length, only some examples are listed below to further illustrate the advantages of the technical solutions of the application.

[0023] Example 1

[0024] Combination Figure 1 The purchased fresh commercial lithium sheet was packaged in a plasma reaction chamber in an argon-protected glove box, and then mounted on the radio frequency power supply required for plasma generation. Subsequently, trifluorotoluene and SnCl4 were mixed in a molar ratio of 5:1 in an argon-protected glove box, stirred until the two solutions were uniformly dispersed, and loaded into the tank of the reaction source for subsequent reaction source supply. Further, the reaction source, reaction chamber and vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off. At room temperature, an organic-inorganic-alloy hybrid artificial solid-state electrolyte interface reinforced composite lithium metal anode was obtained.

[0025] Examples 2-26

[0026] On the basis of Example 1, the reaction source type and ratio, reaction temperature, plasma reaction radio frequency power, reaction vacuum degree, reaction time and other conditions were changed. The reaction conditions are shown in Table 1 below:

[0027] Comparative Example 1

[0028] In an argon-protected glove box, the fresh lithium sheet was immersed in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio of solution 1:3) for 60 s, then removed. Then the surface residual solvent was absorbed with filter paper. Comparative Sample 1 was obtained.

[0029] Comparative Example 2

[0030] In an argon-protected glove box, the fresh lithium sheet was immersed in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio of solution 3:1) for 120 s, then removed. Then the surface residual solvent was absorbed with filter paper. Comparative Sample 2 was obtained.

[0031] Comparative Example 3

[0032] In the glove box filled with argon protection gas, fresh lithium pieces were soaked in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio of the solution was 3:1) for 300 s and then taken out. Then the surface residual solvent was absorbed with filter paper. Comparative Sample 3 was obtained.

[0033] Comparative Sample 4

[0034] In the glove box filled with argon protection gas, fresh lithium pieces were soaked in a solution of anhydrous tin tetrachloride for 60 s and then taken out. Then the surface residual solvent was absorbed with filter paper. Subsequently, trifluorotoluene was filled into the tank of the reaction source in the glove box filled with argon protection gas for subsequent reaction source supply. Further, the reaction source, the reaction chamber and the vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off. Comparative Sample 4 was obtained.

[0035] Comparative Sample 5

[0036] In the glove box filled with argon protection gas, fresh lithium pieces were soaked in a solution of trifluorotoluene for 60 s and then taken out. Then the surface residual solvent was absorbed with filter paper. Subsequently, anhydrous tin tetrachloride was filled into the tank of the reaction source in the glove box filled with argon protection gas for subsequent reaction source supply. Further, the reaction source, the reaction chamber and the vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off. Comparative Sample 5 was obtained.

[0037] Comparative Sample 6

[0038] In the glove box filled with argon protection gas, fresh lithium pieces were soaked in a mixed solution of trifluorotoluene and anhydrous silicon tetrachloride (molar ratio of the solution was 3:1) for 60 s and then taken out. Then the surface residual solvent was absorbed with filter paper. Comparative Sample 6 was obtained.

[0039] Comparative Sample 7

[0040] In the glove box filled with argon protection gas, fresh lithium pieces were taken out after being soaked in anhydrous silicon tetrachloride solution for 60 s. Then the surface residual solvent was absorbed with filter paper. Subsequently, trifluoromethylbenzene was filled into the tank of the reaction source in the glove box filled with argon protection gas for subsequent reaction source supply. Further, the reaction source, the reaction chamber and the vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off to obtain Comparative Sample 7.

[0041] Comparative Sample 8

[0042] In the glove box filled with argon protection gas, fresh lithium pieces were taken out after being soaked in trifluoromethylbenzene solution for 60 s. Then the surface residual solvent was absorbed with filter paper. Subsequently, anhydrous silicon tetrachloride was filled into the tank of the reaction source in the glove box filled with argon protection gas for subsequent reaction source supply. Further, the reaction source, the reaction chamber and the vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off to obtain Comparative Sample 8.

[0043] Comparative Sample 9

[0044] In the glove box filled with argon protection gas, fresh lithium pieces were taken out after being soaked in a mixed solution of perfluorohexane and anhydrous tin tetrachloride (molar ratio of the solution was 1:3) for 60 s. Then the surface residual solvent was absorbed with filter paper. Comparative Sample 9 was obtained.

[0045] Comparative Sample 10

[0046] In the glove box filled with argon protection gas, fresh lithium pieces were taken out after being soaked in anhydrous tin tetrachloride solution for 60 s. Then the surface residual solvent was absorbed with filter paper. Subsequently, perfluorohexane was filled into the tank of the reaction source in the glove box filled with argon protection gas for subsequent reaction source supply. Further, the reaction source, the reaction chamber and the vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber, then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off to obtain Comparative Sample 10.

[0047] Comparative Sample 11

[0048] In the glove box filled with argon protection gas, fresh lithium sheet was taken out after soaking in perfluorohexane solution for 60 s. Then the surface residual solvent was absorbed with filter paper. Subsequently, anhydrous tin tetrachloride was loaded into the tank of the reaction source for subsequent reaction source supply, also in the argon protection glove box. Further, the reaction source, reaction chamber and vacuum servo system were connected in turn, and the positive and negative electrodes of the radio frequency power supply were connected at both ends of the reaction chamber. Then the vacuum system and the reaction source bottle valve were opened, the pressure in the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, the glow discharge was started, and after 60 s, the radio frequency power supply was turned off to obtain the comparative sample 11.

[0049] Performance test

[0050] The composite electrode materials prepared in the above examples 1-26 and comparative examples 1-11 were assembled into button-type half batteries for electrochemical testing. The electrolyte was 1 mol / L lithium bis (trifluoromethanesulfonyl) imide solution in 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME) mixed at a volume ratio of 1:1, and 1% lithium nitrate was added as an additive to the electrolyte. Celgard2400 type. The lithium-lithium symmetric battery was assembled in the order of positive electrode shell, composite electrode material, electrolyte, separator, composite electrode material and negative electrode shell, and was tightly sealed with a full-automatic packaging machine.

[0051] After the battery was left for 24 hours, electrochemical testing was performed using a new Wei and electrochemical workstation. The electrochemical testing was carried out at 25°C, including constant current charge and discharge test and electrochemical impedance analysis. At a current density of 1 mA / cm 2 , a capacity of 1 mAh / cm 2 , the long cycle performance of the battery was tested (the test results are shown in Figure 6 . The performance test results are shown in Table 2 below:

[0052]

[0053] From the performance test results of each example and comparative example in Table 2, it can be found that the organic-inorganic-alloy hybrid artificial solid-state electrolyte interface modified lithium metal negative electrode obtained by mixing SnCl4 and trifluorotoluene at a molar ratio of 3:1, a pressure of 20 Pa in the reaction chamber, a discharge power of 100 W and a discharge time of 60 s in example 6 exhibits the smallest equilibrium overpotential and the smallest impedance under various current densities.

[0054] Figure 1It is a schematic diagram of the plasma reaction device for the organic-inorganic-alloy hybrid artificial solid-state electrolyte interface of the application; the device is composed of a radio frequency plasma excitation device, a copper ring, a quartz tube, a flange, a ball valve and other accessories.

[0055] Figure 2 It is the SEM morphology diagram of pure lithium sheet (a), Example 8 (b), Comparative Example 1 (c) and Example 6 (d). The SEM diagram of the pure lithium sheet sample can be seen that the surface is rough and uneven, and the irregular morphology means that there is a layer of unevenly distributed natural oxide layer; the SEM diagram of Comparative Sample 1 sample can be seen that there are obvious pores and loose structure, which is not conducive to the uniform and dense deposition of lithium, and the SEM diagram of Example 8 sample also has problems such as loose structure compared with Example 6, it can be seen that the modification process under non-optimal conditions can lead to apparent large differences, but still can improve the electrochemical performance to some extent; the SEM diagram of Example 6 sample presents a uniform and compact deposition layer, which indicates that the preparation process conditions significantly improve the lithium deposition behavior and significantly improve the battery performance.

[0056] Figure 3 It is the high-resolution TEM diagram and element area distribution diagram of Example 6 sample. From the HR-TEM, the (111) and (200) crystal planes of LiF can be clearly observed, which confirms the large distribution of LiF component in the SEI, and through the EDS energy spectrum element area distribution, it can be seen that the F, Sn, Cl and C elements are uniformly distributed in the SEI.

[0057] Figure 4 It is the result comparison diagram of Example 6 sample before and after XPS etching for 300s. According to the intensity change of XPS peak, it can be found that the carbon layer is distributed in the outermost layer of SEI; LiCl does not change significantly with the increase of etching depth; the content of LiF increases significantly with the increase of etching depth, and the change trend of Li-Sn alloy component is similar to that of LiF, which indicates that the constructed SEI presents a gradient distribution structure.

[0058] Figure 5 It is the time-of-flight secondary ion mass spectrometry (TOF-SIMS) of Example 6 sample. The distribution of sputtering time and signal intensity indicates the construction of layered structure SEI. The three-dimensional image of ion fragments more intuitively shows this structure, i.e. organic carbon layer / LiCl / LiF / Li-Sn alloy from outside to inside.

[0059] Figure 6 It is the Li / Li symmetric battery assembled by pure lithium sheet, Comparative Example 1 and Example 6 respectively, under the conditions of deposition current and deposition capacity of 1 mA / cm 2 and 1 mAh / cm 2Example 6 can be stably operated for up to 1600 hours, significantly better than the pure lithium sheet without interface modification and the comparative example 1 modified by conventional technology.

[0060] The application is based on the low-temperature plasma to induce the construction of artificial solid-state electrolyte interface on lithium sheet in situ as a lithium metal negative electrode material, which has higher ion diffusion speed and more solid mechanical performance. Therefore, the lithium metal negative electrode prepared by the material has lower equilibrium potential and smaller impedance. Therefore, the application of plasma-assisted preparation of artificial solid-state electrolyte interface technology in high-end application scenarios such as energy storage batteries, flexible electronics, electric vehicles, distributed energy and deep space exploration shows broad application prospects.

[0061] The above-mentioned examples are only the preferred schemes of the application, and do not limit the application in any form. There are other variants and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A plasma in-situ construction method for lithium metal negative electrode solid-state electrolyte interface layer, characterized in that, The method is to construct an artificial solid-state electrolyte interface layer with organic-inorganic-alloy gradient layers on the surface of lithium metal in situ by using lithium metal as a reaction matrix and an organic-inorganic-alloy component precursor as a reaction source in combination with low-pressure and low-temperature plasma technology; the reaction source is at least one selected from benzene, trifluorotoluene, perfluorohexane, anhydrous tin tetrachloride, anhydrous titanium tetrachloride, anhydrous silicon tetrachloride, anhydrous molybdenum chloride and anhydrous vanadium chloride.

2. The plasma in-situ construction method for a lithium metal negative electrode solid-state electrolyte interface layer according to claim 1, characterized in that, The lithium metal can be further replaced by or combined with other materials selected from at least one of sodium, potassium, aluminum, magnesium, zinc, iron, copper, tin foil, carbon cloth, carbon nanotubes, graphene, graphene sponge, polyimide film, polyacrylonitrile film and various MOF materials.

3. The method of claim 1, wherein the method is in-situ plasma construction of a solid electrolyte interphase layer for lithium metal anodes. The reaction source includes an organic source and an inorganic metal compound source, the organic source is at least one selected from benzene, trifluorotoluene and perfluorohexane, and the inorganic metal compound source is at least one selected from anhydrous tin tetrachloride, anhydrous titanium tetrachloride, anhydrous silicon tetrachloride, anhydrous molybdenum chloride and anhydrous vanadium chloride.

4. The method of claim 3, wherein the method is characterized by: The molar ratio of the organic source to the inorganic metal compound source is 1:0.5-10.

5. The plasma in-situ construction method for a solid electrolyte interface layer of lithium metal anode according to claim 4, characterized in that, The molar ratio of the organic source to the inorganic metal compound source is 1:1-5.

6. The method of claim 1, wherein the method is in-situ plasma construction of a solid electrolyte interphase layer for lithium metal anodes. In the low-pressure and low-temperature plasma technology, the vacuum intensity of the low pressure is 10 Pa-50 Pa, the low temperature is 20°C-100°C, the plasma radio frequency power is 30-500 W, and the post-glow reaction time is 30-300 s.

7. The method of claim 6, wherein the method is a plasma in-situ construction method for a lithium metal negative electrode solid electrolyte interface layer. The reaction source is a mixture of trichlorotoluene and anhydrous tin tetrachloride with a molar ratio of 1:3-5, the vacuum intensity of the low pressure in the low-pressure and low-temperature plasma technology is 20 Pa, the low temperature is room temperature, the plasma radio frequency power is 100 W, and the post-glow reaction time is 60 s.

8. The method of claim 1, wherein the method is in-situ plasma construction of a solid electrolyte interphase layer for lithium metal anodes. The method specifically includes the following steps: (1) Under the protection of an inert atmosphere, air-sensitive lithium metal is transferred into a plasma reaction cavity and sealed, and a reaction source is transferred into a reaction source bottle and sealed; (2) The reaction source bottle, the plasma reaction cavity and a vacuum system are sequentially connected, a feed valve of the vacuum system and the reaction source bottle is started, the background vacuum degree in the cavity is dynamically stabilized to a process vacuum window required for reaction, and feed and discharge dynamic balance is achieved; (3) A radio frequency power supply is connected, the plasma reaction cavity is heated to a suitable temperature, the plasma radio frequency power and the discharge time are adjusted, and an artificial solid-state electrolyte interface with organic-inorganic-alloy gradient layers is obtained on the surface of the lithium metal.

9. A solid-state electrolyte interface layer for a lithium metal negative electrode prepared by the plasma in-situ construction method according to any one of claims 1-8.

10. Application of the solid-state electrolyte interface layer for a lithium metal negative electrode according to claim 9 in a lithium metal battery.

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