A lithium metal negative electrode solid electrolyte interface layer and a plasma in-situ construction method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and relates to a solid-state electrolyte interface layer for a lithium metal negative electrode and an in-situ plasma construction method and application thereof. The core of the method is to use an organic-inorganic-alloy component precursor as a plasma reaction source, to control the mixing ratio and reaction conditions to perform plasma reaction on the surface of lithium metal, and to in-situ construct a unique gradient layered structure of an organic-inorganic-alloy composite artificial solid-state electrolyte interface layer. 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. Meanwhile, the preparation method provided by the application is simple, rapid, efficient, environmentally friendly, mild in conditions and easy to control, significantly improves the cycle stability and coulombic efficiency of the lithium metal negative electrode, and is helpful to promote the development of high-energy-density lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery anode interface modification technology, specifically to a method for solid electrolyte interface layer of lithium metal anode and its in-situ plasma construction, and its application in the field of lithium metal batteries. Background Technology

[0002] For electric transportation and aerospace equipment, the device-level energy density is ≥400 Wh kg. -1 The rigid demand for long-range applications means that current lithium-ion battery systems using graphite as the anode are nearing their theoretical limit, making it difficult to meet the range anxiety of long-endurance drones, high-altitude pseudosatellites, and next-generation electric vehicles requiring a range of >500 km. In contrast, lithium metal anodes, with a capacity of 3860 mAh g, offer a more robust solution. -1 Its ultra-high theoretical specific capacity (10 times that of graphite), lowest electrochemical potential (–3.04 V vs. SHE), and the elimination of the extra mass / volume redundancy from carbon / silicon hosts enable an effective capacity at the anode level of >3000 mAh g⁻¹. -1 Theoretically, this could increase the energy density of the entire battery to >500 Wh kg. -1 Lithium metal anodes are considered the "ultimate anode" for breaking through the energy density bottleneck of existing energy storage systems. However, the practical application of lithium metal anodes faces several major challenges: ① High activity leads to uncontrollable dendrite formation; ② High volume expansion (≈80%) induces interface pulverization; ③ High interfacial side reactions continuously consume active lithium, ultimately resulting in low coulombic efficiency (<99%) and short cycle life. Therefore, it is urgent to optimize and upgrade lithium metal anodes from the atomic-level interfacial chemistry or macroscopic three-dimensional structure to achieve a stringent balance between energy density and cycle life.

[0003] Currently, methods for modifying lithium metal mainly include: artificial solid-state electrolyte interface engineering and three-dimensional current collector / host structure construction strategies. Among these, artificial solid-state electrolyte interface engineering primarily involves pre-constructing a multifunctional interface on the lithium metal surface that is "fast for ions, slow for electrons, mechanically tough, and chemically inert," which can both provide lithium with a high-performance electrolyte and a high-performance host structure. +The three-dimensional current collector / host structure construction strategy mainly achieves uniform lithium deposition and stripping by adjusting lithium-ion nucleation sites and reducing local current density, thereby inhibiting lithium dendrite growth. However, the three-dimensional current collector / host construction strategy has been slow to move out of the laboratory due to problems such as high process threshold, low yield, high equipment and material costs, and reduced actual energy density caused by the introduction of inactive substances. In contrast, artificial solid electrolyte engineering directly reconstructs the interface at the atomic-molecular scale, which can provide a high Young's modulus (>6 GPa) to inhibit lithium dendrite growth and a faster lithium-ion transport channel (10 nm) with an ultrathin artificial solid electrolyte layer of <100 nm. -4 S cm -1 Achieving uniform lithium-ion deposition without introducing additional host mass ensures the high energy density advantage of lithium metal batteries. However, current strategies for constructing artificial solid-state electrolyte interfaces suffer from drawbacks such as complex preparation processes, long processing times, high costs, and significant environmental impact, as well as poor stability, preventing lithium metal anodes from achieving ideal performance indicators and achieving large-scale application. For example, methods such as solution coating and vapor deposition have insufficient control over the uniformity of nanoscale film thickness; excessive thickness significantly increases interfacial impedance and reduces energy density, while insufficient thickness results in insufficient mechanical strength, leading to localized cracking in the later stages of cycling. Alternating current deposition (ALD) requires high vacuum, high temperature, or special precursors, resulting in large equipment investments; while wet processes such as spin coating and dipping are simple, their thickness and composition vary greatly between batches due to the influence of substrate wettability and solvent evaporation rate.

[0004] Based on this, this invention proposes a mild and efficient method for modifying the interface of lithium metal anodes, utilizing advanced low-temperature plasma technology to construct an artificial solid-state electrolyte interface in situ on the lithium metal surface. This method can directionally construct the composition, structure, and physicochemical properties of the artificial solid-state electrolyte interface according to target requirements, exhibiting universality and scalability. Furthermore, this method involves a low preparation temperature for constructing the artificial solid-state electrolyte interface, typically below 100°C, and a short reaction time, usually less than one minute, significantly improving preparation efficiency. Since the entire process requires no high-temperature sintering and leaves no solvent residue, it provides a highly scalable new paradigm for interface engineering in the large-scale and green manufacturing of lithium metal anodes. Summary of the Invention

[0005] The purpose of this invention is to address the problems of complex, unstable, costly, and time-consuming surface modification processes for lithium metal anodes in existing technologies. It provides a method and application for the in-situ plasma-assisted fabrication of a solid-state electrolyte interface layer for lithium metal anodes. By controlling parameters such as the proportion of reaction source components, reaction time, reaction temperature, radio frequency power, and vacuum level, the composition and structure of the solid electrolyte can be directionally controlled, thereby constructing an ideal high-performance artificial solid-state electrolyte interface layer for lithium metal anodes. The plasma-assisted fabrication process provided by this invention can rapidly optimize the interface of lithium metal anodes at relatively low temperatures, resulting in optimized lithium metal anodes exhibiting higher coulombic efficiency, good cycle stability, and excellent rate performance, effectively promoting the commercialization of high-energy-density lithium batteries.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] This invention provides a plasma in-situ construction method for a solid electrolyte interface layer for lithium metal anodes. The method uses air-sensitive lithium metal as the reaction substrate and an organic-inorganic-alloy component precursor as the reaction source. It combines low-pressure, low-temperature plasma technology to construct an artificial solid electrolyte interface layer with an organic-inorganic-alloy gradient layer on the lithium metal surface in situ. The organic-inorganic-alloy component precursor of the reaction source is selected from at least one of benzene, trifluorotoluene, perfluorohexane, anhydrous tin tetrachloride, anhydrous titanium tetrachloride, anhydrous silicon tetrachloride, anhydrous molybdenum chloride, and anhydrous vanadium chloride.

[0008] By employing the aforementioned technical solution: This invention utilizes advanced low-temperature plasma technology to select specific reaction sources for surface modification of air-sensitive lithium metal, thereby obtaining a unique, high-performance artificial solid-state electrolyte interface layer. Furthermore, depending on the selected reaction source, different interface layers can be obtained, such as organic, organic-inorganic composite, and inorganic-alloy composite layers. Even more remarkably, through composite reaction sources, a previously unreported organic-inorganic-alloy gradient layered composite artificial solid-state electrolyte interface layer with superior performance can be obtained. This solid-state electrolyte interface layer consists of a flexible organic phase on the outer layer, a rigid inorganic fast-ion conductor in the middle layer, and a lithiophilic alloy phase on the inner layer, which synergistically inhibits lithium dendrite growth and significantly improves the interfacial stability of the lithium metal anode. By further controlling the component ratio of the reaction source, reaction temperature, cavity vacuum, and RF discharge power and time, the desired artificial solid-state electrolyte interface layer can be flexibly prepared. This method offers a wide range of reaction source selection, simple process, high efficiency, and environmental friendliness, and can be extended to the surface modification of other air-sensitive materials. Simultaneously, by selecting the reaction source and optimizing process parameters, it is possible to synergistically enhance ion transport kinetics at the modified interface, increase Young's modulus, and lower the ion nucleation barrier, thereby achieving uniform lithium ion nucleation and horizontal growth, suppressing lithium dendrite formation, and extending the cycle life of lithium metal batteries. This invention contributes to promoting the practical application of high-energy-density lithium metal batteries.

[0009] Preferably, the air-sensitive lithium metal used is a commercial lithium metal sheet, but it can be further extended to other air-sensitive / air-stable materials, such as sodium, potassium, aluminum, magnesium, zinc, iron, copper, tin foil, carbon cloth, carbon nanotubes, graphene, graphene sponge, polyimide film, polyacrylonitrile film, and various MOF materials.

[0010] Preferably, the reaction source can be a single compound, or two or more compounds in any proportion; more preferably, the organic-inorganic-alloy component precursor of the reaction source includes an organic source and an inorganic metal compound source, wherein the organic source is selected from at least one of benzene, trifluorotoluene, and perfluorohexane; and 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.

[0011] Preferably, the low-pressure vacuum intensity in the low-pressure low-temperature plasma technology is 10 Pa to 50 Pa. The reaction source selected in this invention is easily vaporized or volatilized under these low vacuum conditions, thus easily entering the reaction chamber in vapor form for reaction. More preferably, the vacuum degree of this invention is 20 Pa.

[0012] Preferably, the low temperature in the low-pressure low-temperature plasma technology is 20℃-100℃, more preferably room temperature. The reaction source selected in this invention can enter the reaction chamber to carry out the reaction under low temperature or even room temperature conditions, without the need for heating; however, heating at low temperatures can better facilitate the reaction. A balance can be struck between energy and reaction efficiency based on actual conditions.

[0013] Preferably, the plasma radio frequency power in the low-pressure low-temperature plasma technology is 30-500W, and the reaction time after glow discharge is 30-300s. More preferably, the radio frequency power is 100W, and the reaction time is 60s.

[0014] Preferably, the method specifically includes the following steps:

[0015] (1) Under the protection of an inert atmosphere, the air-sensitive lithium metal is transferred to the plasma reaction chamber and sealed, and the reaction source is added to the reaction source bottle and sealed.

[0016] (2) Connect the reaction source bottle, plasma reaction chamber and vacuum system in sequence, start the vacuum system and the feed valve of the reaction source bottle, and dynamically stabilize the background vacuum in the chamber to the vacuum intensity of the process vacuum window required for the reaction to occur through the closed-loop vacuum system, so as to achieve dynamic balance between feeding and discharging.

[0017] (3) Turn on the radio frequency power supply and heat the plasma reaction chamber to a suitable temperature. Adjust the plasma radio frequency power and discharge time to obtain an artificial solid electrolyte interface with organic-inorganic-alloy gradient layering on the lithium metal surface.

[0018] Preferably, in step (1), the inert atmosphere is at least one of argon, nitrogen, helium, argon-hydrogen mixture, nitrogen-hydrogen mixture, and helium-hydrogen mixture.

[0019] Based on the above, the present invention also provides a solid electrolyte interface layer for lithium metal anodes obtained by any of the above-mentioned plasma in-situ construction methods.

[0020] Based on the above, the present invention also provides an application of the above-mentioned solid electrolyte interface layer for lithium metal anode in lithium metal batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention employs low-temperature plasma technology to construct an artificial solid electrolyte interface layer with tunable composition structure on the surface of lithium metal in situ, which 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, a vacuum system is used to pump the mixed vapor of trifluorotoluene and anhydrous tin tetrachloride into the reaction chamber, and then the mixture is dissociated into a large number of active groups by a radio frequency power supply. Under the action of electric field force, active groups and ions with different masses and energies bombard the surface of lithium metal. Due to the different intrinsic energies of different ions or active groups, the penetration depth on the lithium sheet surface is different, thus forming an artificial solid electrolyte layer with an organic-inorganic-metal composite gradient layered structure. The outer layer of this 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 lithiophilic alloy phase, which can synergistically inhibit the growth of lithium dendrites and significantly improve the interface stability of the lithium metal anode. This gradient structure is determined by the unique properties of plasma surface treatment combined with a special reaction source. The outermost flexible organic component of the constructed artificial solid electrolyte layer helps alleviate volume expansion and release interfacial stress during lithium deposition and stripping, preventing solid electrolyte layer cracking caused by electrode volume changes. The inorganic-rich component in the middle layer acts as a rigid framework, enhancing the mechanical strength of the artificial solid electrolyte interface. Simultaneously, numerous grain boundaries provide rapid lithium-ion transport channels and uniform lithium flux. The innermost alloy layer acts as lithiophilic sites, lowering the lithium-ion nucleation barrier, regulating lithium-ion nucleation and growth behavior, and suppressing uncontrolled lithium dendrite growth. The synergistic effect of these multiple components contributes to improving the cycle life and coulombic efficiency of the lithium metal anode, thus promoting the practical application of high-energy-density lithium metal batteries.

[0023] (2) This invention patent proposes a method for constructing artificial solid electrolyte interfaces using a low-temperature plasma-assisted method. This method is a low-temperature transient reaction method for constructing artificial solid electrolyte interfaces in a controllable manner. By pre-designing the chemical composition of the precursor, the functional group sequence and the reaction path, an organic-inorganic-alloy hybrid SEI with a preset stoichiometric ratio, layered / gradient / three-dimensional topological structure and target physicochemical parameters can be directionally grown on the surface of a lithium metal anode under mild conditions of ≤100 ℃ and ≤300 s. This method has directionality, universality and scalability, and is a new technology with value for further development and exploration.

[0024] (3) This invention is based on plasma-induced in-situ construction of artificial solid electrolyte interfaces, which can achieve film formation in seconds at room temperature or low temperature. Moreover, the entire preparation process requires no solvent or post-processing, and the experimental procedure is extremely simple and efficient. Therefore, this plasma-assisted preparation technology for artificial solid electrolyte interfaces shows 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 this invention is simple, fast, efficient, environmentally friendly, and has mild and easily controllable conditions, which significantly improves the cycle stability and coulombic efficiency of lithium metal anodes and helps to promote the development of high-energy-density lithium metal batteries. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the plasma reaction device in this invention;

[0026] Figure 2 The images show a comparison of the scanning electron microscope (SEM) morphologies of pure lithium wafers, Example 8, Comparative Example 1, and Example 6.

[0027] Figure 3 Here are high-resolution transmission electron microscope images and corresponding EDS elemental distribution maps for Example 6;

[0028] Figure 4 XPS images of Example 6 before and after etching for 300 seconds;

[0029] Figure 5 The time-of-flight secondary ion mass spectrum of Example 6;

[0030] Figure 6 Pure lithium sheets, Comparative Example 1 and Example 6 were prepared at 1 mA cm⁻¹ -2 At current density, the deposition stripping capacity is 1 mAhcm⁻¹. -2 Comparison of long-cycle stability of symmetrical cells under certain conditions. Detailed Implementation

[0031] To facilitate understanding, the technical solutions and implementation methods of the present invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of the present invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining the present invention and do not limit the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the experimental methods and conditions used in the following embodiments are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and are commercially available. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, only some embodiments are listed below to further illustrate the advantages of the technical solution of the present invention.

[0033] Example 1

[0034] Combination Figure 1 Freshly purchased commercial lithium wafers were sealed in an argon-protected glove box within a plasma reaction chamber, and then mounted on the radio frequency power supply required for plasma generation. Subsequently, trifluorotoluene and SnCl4 were mixed in a 5:1 molar ratio within the same argon-protected glove box and stirred until the two solutions were uniformly dispersed. This mixture was then placed into the reaction source container for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure within the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off. This yielded a composite lithium metal anode with an enhanced organic-inorganic-alloy hybrid artificial solid electrolyte interface at room temperature.

[0035] Example 2-26

[0036] Based on Example 1, the types and proportions of reaction sources, reaction temperature, plasma reaction radio frequency power, reaction vacuum degree, and reaction time were changed. The reaction conditions are shown in Table 1 below:

[0037]

[0038] Comparative Example 1

[0039] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio 1:3) for 60 seconds and then removed. The residual solvent on the surface was then blotted dry with filter paper. This yielded control sample 1.

[0040] Comparative Example 2

[0041] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio 3:1) for 120 s, and then removed. The residual solvent on the surface was then blotted dry with filter paper. This yielded control sample 2.

[0042] Comparative Example 3

[0043] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in a mixed solution of trifluorotoluene and anhydrous tin tetrachloride (molar ratio 3:1) for 300 s, and then removed. The residual solvent on the surface was then blotted dry with filter paper. This yielded control sample 3.

[0044] Comparative Example 4

[0045] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in anhydrous tin tetrachloride solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, trifluorotoluene was placed into the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off to obtain control sample 4.

[0046] Comparative Example 5

[0047] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in trifluorotoluene solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, anhydrous tin tetrachloride was placed into the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off to obtain control sample 5.

[0048] Comparative Example 6

[0049] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in a mixed solution of trifluorotoluene and anhydrous silicon tetrachloride (molar ratio 3:1) for 60 seconds and then removed. The residual solvent on the surface was then blotted dry with filter paper. This yielded control sample 6.

[0050] Comparative Example 7

[0051] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in anhydrous silicon tetrachloride solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, trifluorotoluene was placed into the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off to obtain control sample 7.

[0052] Comparative Example 8

[0053] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in trifluorotoluene solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, anhydrous silicon tetrachloride was placed into the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off to obtain control sample 8.

[0054] Comparative Example 9

[0055] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in a mixed solution of perfluorohexane and anhydrous tin tetrachloride (molar ratio 1:3) for 60 seconds and then removed. The residual solvent on the surface was then blotted dry with filter paper. This yielded control sample 9.

[0056] Comparative Example 10

[0057] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in anhydrous tin tetrachloride solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, perfluorohexane was added to the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off, yielding control sample 10.

[0058] Comparative Example 11

[0059] In a glove box filled with argon protective gas, fresh lithium sheets were immersed in perfluorohexane solution for 60 seconds and then removed. Residual solvent on the surface was then blotted dry with filter paper. Subsequently, anhydrous tin tetrachloride was placed into the reaction source container in the same argon-protected glove box for subsequent reaction source supply. Further, the reaction source, reaction chamber, and vacuum servo system were connected sequentially, and the positive and negative terminals of the radio frequency power supply were connected to both ends of the reaction chamber. The vacuum system and reaction source bottle valves were then opened, the pressure inside the reaction chamber was adjusted to 20 Pa, the radio frequency power supply was turned on, the discharge power was adjusted to 100 W, glow discharge was initiated, and after 60 seconds, the radio frequency power supply was turned off to obtain control sample 11.

[0060] Performance testing

[0061] The composite electrode materials prepared in Examples 1-26 and Comparative Examples 1-11 were assembled into coin half-cells for electrochemical testing. The electrolyte was 1 mol / L lithium bis(trifluoromethanesulfonyl)imide dissolved in 1,3-dioxolane (DOL) and dimethyl ethylene glycol (DME) (mixed in a 1:1 volume ratio), with 1% lithium nitrate added as an additive. Celgard 2400 type batteries were used. The lithium-lithium symmetric batteries were assembled in the following order: positive electrode shell, composite electrode material, electrolyte, separator, composite electrode material again, and negative electrode shell, and then sealed using a fully automated packaging machine.

[0062] After the battery was left to stand for 24 hours, electrochemical tests were performed using a Newway electrochemical workstation. All electrochemical tests were conducted at 25°C, including constant current charge-discharge testing and electrochemical impedance analysis. The current density was 1 mA / cm². 2 Capacity 1mAh / cm 2 Under these conditions, the long-cycle performance of the battery was tested (test results are as follows). Figure 6 (as shown)

[0063] The performance test results are shown in Table 2 below:

[0064]

[0065]

[0066] The performance test results of the various embodiments and comparative examples in Table 2 show that the lithium metal anode modified with an organic-inorganic-alloy hybrid artificial solid electrolyte interface obtained in Example 6, which is a mixture of SnCl4 and trifluorotoluene in a molar ratio of 3:1, with a pressure of 20 Pa in the reaction chamber, a discharge power of 100 W, and a discharge time of 60 s, exhibits the smallest equilibrium overpotential and the smallest impedance under various current densities.

[0067] Figure 1This is a schematic diagram of the plasma reaction device for the organic-inorganic-alloy hybrid artificial solid electrolyte interface of the present invention; the device consists of a radio frequency plasma excitation device, a copper ring, a quartz tube, a flange, a ball valve and other accessories.

[0068] Figure 2 The images show the SEM morphology of pure lithium wafers (a), Example 8 (b), Comparative Example 1 (c), and Example 6 (d). The SEM images of the pure lithium wafer sample show a rough and uneven surface, indicating the presence of an unevenly distributed natural oxide layer. The SEM image of Comparative Example 1 shows obvious pores and a loose structure, which is not conducive to uniform and dense lithium deposition. The SEM image of Example 8 also shows a loose structure compared to Example 6. This demonstrates that suboptimal modification processes can lead to significant differences in appearance, but can still improve electrochemical performance to some extent. The SEM image of Example 6, however, shows a uniform and compact deposition layer, indicating that its preparation process conditions significantly improved lithium deposition behavior and significantly enhanced battery performance.

[0069] Figure 3 The high-resolution TEM image and elemental plane distribution diagram of the sample in Example 6 are shown. The (111) and (200) crystal planes of LiF can be clearly observed from the HR-TEM, confirming the large distribution of LiF components in the SEI. Furthermore, the elemental plane distribution of the EDS energy spectrum shows that F, Sn, Cl, and C elements are uniformly distributed in the SEI.

[0070] Figure 4 The image shows a comparison of the XPS etching results of the sample in Example 6 before and after 300 s. Based on the intensity changes of the XPS peaks, it can be found that the carbon layer is distributed on the outermost layer of the SEI; the LiCl content does not change significantly with the increase of etching depth; however, the LiF content increases significantly with the increase of etching depth. The change trend of the Li-Sn alloy composition is similar to that of LiF, indicating that the constructed SEI exhibits a gradient distribution structure.

[0071] Figure 5 The image shows the time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the sample from Example 6. The distribution of sputtering time and signal intensity indicates the construction of a layered SEI structure. The three-dimensional image of the ion fragments more clearly shows this structure, namely an organic carbon layer / LiCl / LiF / Li-Sn alloy from the outside to the inside.

[0072] Figure 6 Using pure lithium sheets, the Li / Li symmetric cells assembled in Comparative Example 1 and Example 6 respectively achieved a deposition current and deposition capacity of 1 mA / cm². 2 and 1 mAh / cm 2The long-cycle performance of Example 6 is significantly better than that of unmodified pure lithium wafers and Comparative Example 1, which is modified by conventional technology. Example 6 can operate stably for up to 1600 hours, which is significantly better than that of pure lithium wafers without interface modification and Comparative Example 1.

[0073] This invention utilizes low-temperature plasma-induced in-situ construction of an artificial solid-state electrolyte interface on a lithium sheet as a lithium metal anode material, exhibiting higher ion diffusion rates and stronger mechanical properties. Therefore, the lithium metal anode prepared from this material possesses a lower equilibrium potential and lower impedance. Consequently, this plasma-assisted artificial solid-state electrolyte interface technology demonstrates broad application prospects in high-end applications such as energy storage batteries, flexible electronics, electric vehicles, distributed energy, and deep space exploration.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for in-situ plasma construction of a solid electrolyte interface layer for lithium metal anodes, characterized in that, The method uses lithium metal as the reaction matrix and an organic-inorganic-alloy component precursor as the reaction source. It combines low-pressure, low-temperature plasma technology to construct an artificial solid electrolyte interface layer with an organic-inorganic-alloy gradient on the lithium metal surface in situ. The reaction source is a mixture of 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 molybdenum chloride, and anhydrous vanadium chloride. The molar ratio of the organic source to the inorganic metal compound source is 1:1 to 10. The low-pressure, low-temperature plasma technology uses a vacuum strength of 10 Pa to 50 Pa, a low temperature of 20°C to 100°C, a plasma radio frequency power of 30 to 500 W, and a post-glow glow discharge reaction time of 30 to 300 s.

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

3. The plasma in-situ construction method for the solid electrolyte interface layer of lithium metal anode according to claim 1, characterized in that, The low-pressure, low-temperature plasma technology features a vacuum intensity of 10Pa-20Pa, a low temperature of 25℃-100℃, a plasma radio frequency power of 30-500W, and a post-glow reaction time of 60s.

4. The plasma in-situ construction method for the solid electrolyte interface layer of lithium metal anode according to claim 3, characterized in that, The reaction source is a mixture of trichlorotoluene and anhydrous tin tetrachloride in a molar ratio of 1:3~5. The low-pressure vacuum intensity in the low-pressure low-temperature plasma technology is 20 Pa, the low temperature is room temperature, the plasma radio frequency power is 100 W, and the reaction time after glow discharge is 60 s.

5. The plasma in-situ construction method for a solid electrolyte interface layer of lithium metal anode according to claim 1, characterized in that, The method specifically includes the following steps: (1) Under the protection of an inert atmosphere, the air-sensitive lithium metal is transferred to the plasma reaction chamber and sealed, and the reaction source is transferred to the reaction source bottle and sealed. (2) Connect the reaction source bottle, plasma reaction chamber and vacuum system in sequence, start the vacuum system and the feed valve of the reaction source bottle, and adjust the background vacuum in the chamber to dynamically stabilize to the process vacuum window required for the reaction to achieve dynamic balance between feed and discharge. (3) Turn on the radio frequency power supply and heat the plasma reaction chamber to a suitable temperature. Adjust the plasma radio frequency power and discharge time to obtain an artificial solid electrolyte interface with organic-inorganic-alloy gradient layering on the lithium metal surface.

6. A solid electrolyte interface layer for lithium metal anodes prepared by the plasma in-situ construction method according to any one of claims 1-5.

7. The application of the solid electrolyte interface layer for lithium metal anode as described in claim 6 in lithium metal batteries.

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