Preparation method and application of organic-inorganic gradient fluorinated composite interface for lithium metal protection

Abstract

The invention provides a preparation method of a gradient fluorinated organic-inorganic composite interface for lithium metal protection, and relates to the field of lithium metal negative electrodes of lithium ion batteries. The gradient fluorinated organic-inorganic composite interface is obtained through a molecular layer deposition method, in the molecular layer deposition process, tetrafluorohydroquinone and trimethylaluminum are used as precursors, a fluorinated Aucone protective layer is deposited on the surface of lithium metal at a certain temperature, the fluorinated Aucone layer can spontaneously chemically react with the lithium metal, and the surface of the lithium metal is coated with the fluorinated Aucone protective layer, so that the surface of the lithium metal is coated with the fluorinated Aucone protective layer, and the surface of the lithium metal is coated with the fluorinated Aucone protective layer. And a gradient fluorinated inorganic-organic composite interface is formed. Wherein the side close to the lithium metal is rich in lithium fluoride components, the side far away from the lithium metal is rich in organic fluoride components, and chemical components of an interface change in a gradient manner. The gradient fluorinated composite boundary layer has good mechanical stability and electrochemical-chemical stability, the preparation method is simple, and the repeatability is good. The composite interface can greatly improve the electrochemical stability of the lithium metal negative electrode, inhibit the growth of lithium dendrites, relieve the side reaction between a liquid electrolyte and lithium metal and enhance the compatibility between the lithium metal negative electrode and the electrolyte, so that the lithium metal negative electrode protected by the interface shows excellent electrochemical cycle stability.

Description

Technical Field

[0001] This invention belongs to the technical field, and in particular relates to a preparation technology of an organic-inorganic gradient fluorinated composite interface for lithium metal protection. Background Technology

[0002] With the rapid development of large-scale energy storage, electric vehicles, and consumer electronics, commercial lithium-ion batteries based on graphite and lithium cobalt oxide are struggling to meet energy density demands. Regarding the anode, the theoretical specific capacity of existing graphite anodes is only 372 mAh / g, which is insufficient for daily production and living needs, making the development of anodes with high specific capacity an urgent priority. Lithium metal anodes, with their lowest potential (-3.04V) and extremely high specific capacity (3860 mAh / g), are ideal anode materials for high-energy-density batteries. However, the electrochemical stability of lithium metal anode materials faces serious challenges, primarily due to the poor interfacial stability between lithium metal and the liquid electrolyte. An unstable solid-liquid interface can lead to severe side reactions, inducing lithium dendrite growth, causing serious safety issues, and ultimately resulting in battery failure.

[0003] Studies have shown that constructing a suitable artificial interface can effectively improve the interfacial stability of lithium metal anodes, thereby extending the lifespan of lithium metal. The electrochemical-chemical and mechanical stability of the artificial interface are key factors affecting the electrochemical properties of lithium metal. Among numerous artificial interface studies, organic-inorganic hybrid interfaces have received widespread attention due to their integration of the chemical properties of inorganic and organic components, achieving good electrochemical-mechanical stability. Furthermore, fluorinated interfaces are considered to effectively block interfacial electronic pathways and inhibit electrochemical decomposition reactions of the electrolyte. Additionally, research indicates that organic-inorganic gradient composites can achieve excellent mechanical stability. Therefore, the precise and controllable construction of an organic-inorganic gradient composite fluorinated interface holds promise for significantly improving the electrochemical stability of lithium metal anodes. Summary of the Invention

[0004] This invention overcomes the technical barriers of constructing gradient fluorinated organic-inorganic composite interfaces, providing a controllable preparation technology for composite interfaces based on molecular layer deposition. The purpose of this invention is to solve the stability problem of lithium metal anode interfaces and improve the mechanical and electrochemical stability of lithium metal interfaces to achieve ultra-long cycle life.

[0005] The technical content of this invention is as follows:

[0006] (1) A method for preparing an organic-inorganic gradient fluorinated composite interface for lithium metal anode protection, comprising the following steps:

[0007] S1. Using tetrafluorohydroquinone and trimethylaluminum as precursors for molecular layer deposition and lithium metal as the deposition substrate material, a fluorinated Alucone interface is controllably constructed, which is then further transformed in situ into a gradient fluorinated organic-inorganic composite interface.

[0008] S2. During molecular layer deposition, the deposition chamber temperature is maintained at 50–120°C. Inert gas is used as the carrier gas, with a flow rate set at 80–250 sccm. The preheating temperature of the precursor tetrafluorohydroquinone is set at 90–110°C, with a pulse duration of 0.2–2.0 s and a purge time of 20–50 s. The preheating temperature of the precursor trimethylaluminum is set at 25–45°C, with a pulse duration of 0.2–2.0 s and a purge time of 0.2–5 s. The cycle time for molecular layer deposition is set to M.

[0009] S3. The deposited lithium metal anode is transferred to a vacuum oven for heat treatment, and then the lithium metal anode with interface protection is used to assemble the battery. The assembled battery uses electrolytes of different systems.

[0010] 2. Preferably, the lithium metal anode is subjected to plasma cleaning before molecular layer deposition;

[0011] 3. Preferably, the cycle period M is between 5 and 500 revolutions;

[0012] 4. Preferably, the inert gas is argon or nitrogen;

[0013] 5. Preferably, the heat treatment temperature of the lithium metal anode in the vacuum oven is between 50 and 80°C;

[0014] 6. Preferably, the heat treatment time of the lithium metal anode in the vacuum oven is between 0.2 and 5 hours;

[0015] 7. Preferably, the electrolyte is one of an ester electrolyte or an ether electrolyte; Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the lithium metal anode structure with organic-inorganic gradient composite interface protection constructed in Embodiment 1 of the present invention. The bottom layer is a lithium metal layer, the middle layer is an inorganic fluoride-rich layer, and the top layer is an organic fluoride-rich layer, with a gradient change in composition between the inorganic fluoride-rich layer and the organic fluoride-rich layer.

[0017] Figure 2 Figure a shows the cycle performance of the lithium metal symmetric battery in Embodiment 1 of the present invention. Figure a shows the cycle performance of the symmetric battery with a lithium metal anode without interface protection, and Figure b shows the cycle performance of the symmetric battery with a lithium metal anode with interface protection.

[0018] Figure 3Figure a shows the cycle performance of the lithium metal symmetric battery in Embodiment 2 of the present invention. Figure a shows the cycle performance of the symmetric battery with a lithium metal anode without interface protection, and Figure b shows the cycle performance of the symmetric battery with a lithium metal anode with interface protection.

[0019] This invention primarily investigates the improvement of the electrochemical performance of lithium metal anodes by organic-inorganic gradient fluorination interfaces, focusing on solving the interface stability problem. The challenge lies in the controllable construction of the organic-inorganic gradient fluorination composite interface. The innovation of this invention lies in the successful construction of an organic-inorganic gradient fluorination composite interface on the lithium metal anode using molecular layer deposition (MLD) technology. The coating thickness can be precisely controlled by the number of MLD cycles, thereby achieving regulation of electrochemical performance. The prepared gradient fluorination composite interface exhibits good electrochemical and mechanical stability, effectively suppressing lithium dendrite growth and preventing side reactions between the electrolyte and lithium metal, thus achieving reversible deposition and stripping of the lithium metal anode. The preparation method of this invention is simple, precise, controllable, and highly reproducible, significantly improving the cycle stability and rate performance of the modified lithium metal anode. Detailed Implementation

[0020] The present invention will now be described through specific embodiments. Unless otherwise specified, all technical means used in this invention are methods well known to those skilled in the art. Furthermore, the embodiments should be understood as illustrative, not limiting the scope of the invention; the essence and scope of the invention are defined only by the claims. For those skilled in the art, various changes or modifications to the material composition and dosage in these embodiments without departing from the essence and scope of the invention are also within the scope of protection of this invention. All raw materials and reagents used in this invention are commercially available.

[0021] Example 1

[0022] The preparation method of the gradient fluorinated organic-inorganic composite interface modified lithium metal anode in this embodiment is as follows:

[0023] S1. Place the lithium metal foil into the molecular layer deposition chamber and perform argon plasma cleaning for 5 minutes. The plasma cleaning power is 2.5 kW.

[0024] S2. Subsequently, the molecular layer deposition chamber was heated to 70°C. Argon was set as the carrier gas with a flow rate of 100 sccm. The preheating temperature of the precursor tetrafluorohydroquinone was set to 90°C, with a pulse duration of 2 s and a purge time of 30 s. The preheating temperature of the precursor trimethylaluminum was set to 25°C, with a pulse duration of 0.5 s and a purge time of 30 s. The atomic layer deposition cycle was set to 50 times.

[0025] S3. The deposited lithium metal electrode was heat-treated in a vacuum chamber at 80°C for 3 hours. A symmetrical battery was assembled using a carbonate electrolyte. The electrolyte components included LiPF6, diethyl carbonate (DEC), and ethylene carbonate (EC). The control sample was a lithium metal anode without interface protection.

[0026] Electrochemical performance testing: The lithium metal anode with composite interface protection obtained in this example was tested for electrochemical performance in a coin cell. It can be clearly observed that the lithium metal symmetric cell without interface protection exhibits significantly lower performance at 1.0 mA / cm². 2 At current densities of only 1.0 mA / cm², the cycle life is only 90 hours. In contrast, lithium metal anodes with organic-inorganic gradient composite interface protection achieve a cycle life of only 90 hours. 2 The cycle life at current density reaches 7500 hours. A schematic diagram of the composite interface construction and structure is shown below. Figure 1 As shown. The cycle performance of the lithium metal symmetric battery is as follows. Figure 2 As shown.

[0027] Example 2

[0028] The preparation method of the gradient fluorinated organic-inorganic composite interface modified lithium metal anode in this embodiment is as follows:

[0029] S1. Place the lithium metal foil into the molecular layer deposition chamber and perform argon plasma cleaning for 5 minutes. The plasma cleaning power is 3.0 kW.

[0030] S2. Subsequently, the molecular layer deposition chamber was heated to 80°C. Argon was used as the carrier gas with a flow rate of 150 sccm. The preheating temperature of the precursor tetrafluorohydroquinone was set to 85°C, with a pulse duration of 2 s and a purge time of 30 s. The preheating temperature of the precursor trimethylaluminum was set to 25°C, with a pulse duration of 0.5 s and a purge time of 30 s. The atomic layer deposition cycle was set to 50 times.

[0031] S3. The deposited lithium metal electrode was heat-treated in a vacuum chamber at 70°C for 2 hours. A symmetrical battery was then assembled using an ether-based electrolyte, consisting of LiFSI, 1,3-dioxolane (DOL), and dimethyl ethylene glycol ether (DME). The control sample was a lithium metal anode without interface protection.

[0032] Electrochemical performance testing: The lithium metal anode with composite interface protection obtained in this example was tested for electrochemical performance in a coin cell. It can be clearly observed that the lithium metal symmetric cell without interface protection exhibits lower performance at 3.0 mA / cm². 2 The cycle life at that current density is only 40 hours. In contrast, the lithium metal anode with organic-inorganic gradient composite interface protection achieves a cycle life of only 40 hours at 3.0 mA / cm².2 The cycle life at current density is up to 1600 hours, such as Figure 3 As shown.

[0033] After the detailed description of the preferred embodiments, those skilled in the art will clearly understand that various changes and modifications can be made without departing from the scope and spirit of the above-mentioned claims. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this invention fall within the scope of this invention. Furthermore, this invention is not limited to the exemplary embodiments described in the specification.

Claims

1. A method for preparing a gradient fluorinated organic-inorganic composite interface for lithium metal protection, characterized in that, Includes the following steps: S1. Using tetrafluorohydroquinone and tetramethylaluminum as precursors for molecular layer deposition and lithium metal as the deposition substrate material, a fluorinated Alucone interface is constructed. This interface can be transformed in situ into a gradient fluorinated organic-inorganic composite interface. S2. During molecular layer deposition, the deposition chamber temperature is maintained at 50–120°C. Inert gas is used as the carrier gas, with a flow rate set at 80–250 sccm. The preheating temperature of the precursor tetrafluorohydroquinone is set at 90–110°C, with a pulse duration of 0.2–2.0 s and a purge time of 20–50 s. The preheating temperature of the precursor trimethylaluminum is set at 25–45°C, with a pulse duration of 0.2–2.0 s and a purge time of 0.2–5.0 s. The cycle time for molecular layer deposition is set to M. S3. The deposited lithium metal anode is transferred to a vacuum oven for heat treatment, and then the lithium metal anode with interface protection is used to assemble the battery. The assembled battery uses electrolytes of different systems.

2. The preparation method according to claim 1, characterized in that, The lithium metal anode used must be plasma cleaned before molecular layer deposition.

3. The preparation method according to claim 1, characterized in that, The set cycle period M is between 5 and 500 revolutions.

4. The preparation method according to claim 1, characterized in that, The inert gas used is argon or nitrogen.

5. The preparation method according to claim 1, characterized in that, The heat treatment temperature of lithium metal anodes in a vacuum oven is between 50 and 80°C.

6. The preparation method according to claim 1, characterized in that, The heat treatment time of lithium metal anode in vacuum oven is between 0.2 and 5 hours.

7. The preparation method according to claim 1, characterized in that, The electrolyte used is either an ester-based electrolyte or an ether-based electrolyte.

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