A sodium metal negative electrode material based on a one-step method of constructing a hybrid solid-state electrolyte interface layer by gas-liquid mixed plasma, a preparation method and application thereof

Abstract

The application relates to the technical field of sodium metal electrode material preparation, and discloses a sodium metal negative electrode material based on a gas-liquid mixed plasma one-step method for constructing a hybrid solid-state electrolyte interface layer and a preparation method and application thereof. The method is that sodium metal is taken as a matrix, sulfur hexafluoride gas and fluoroethylene carbonate liquid are taken as plasma sources, a hybrid solid-state electrolyte interface layer is constructed through plasma reaction in one step, and a composite sodium metal electrode is obtained. The negative electrode material preparation method has the characteristics of simplicity, rapidness, high efficiency and easy control, and is helpful to the development of an artificial solid-state electrolyte interface layer in a sodium metal battery. The hybrid solid-state electrolyte interface layer can directly isolate the side reaction between the metal sodium and the electrolyte as a physical barrier, and the excellent mechanical property of the hybrid solid-state electrolyte interface layer effectively inhibits the growth of sodium dendrites. Therefore, the composite negative electrode has good cycle stability, rate performance and high coulomb efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium metal electrode materials, in particular to the technical field of solid electrolyte interface (SEI) layers in sodium metal batteries, and specifically to a sodium metal negative electrode material having a hybrid solid electrolyte interface layer constructed by a one-step method based on gas-liquid mixed plasma, as well as a preparation method and application thereof. Background Art

[0002] With the proposed goals of achieving carbon peak and carbon neutrality, clean energy has rapidly developed. Sodium-ion batteries, due to their safety, high energy density, and long cycle life, have gradually become an important energy storage device. However, hard carbon, the currently widely used anode material for sodium-ion batteries, has a low theoretical capacity and is unable to meet the growing demand for energy storage. Therefore, researchers have begun actively exploring alternative materials to hard carbon.

[0003] Sodium metal is an ideal anode for sodium-ion batteries due to its extremely high theoretical capacity (1166 mAh / g) and extremely low redox potential (−2.71 V). However, major challenges facing sodium metal batteries include volume expansion of the sodium metal during charge and discharge, dendrite growth, and SEI instability. The SEI layer plays a crucial role during battery cycling, minimizing direct contact between the sodium metal and the electrolyte and preventing side reactions. However, naturally occurring SEI layers typically consist of inorganic layers (such as Na2O, NaOH, and Na2CO3) and organic layers (such as ROCO2Na, RONa, and RCOO2Na). While they optimize the interface between the sodium metal and the electrolyte, their structure is heterogeneous and prone to rupture, leading to battery performance degradation and failure. While inorganic SEI layers offer advantages in improving ionic conductivity and interfacial stability, their high rigidity makes them less able to cope with the volume expansion of the sodium metal and can easily lead to rupture and failure during long-term cycling. While organic components are more flexible and can adapt to volume changes, they are less stable than inorganic SEI layers. Therefore, constructing a composite SEI layer with organic and inorganic components has become a research focus.

[0004] Currently, researchers are attempting to prepare hybrid SEI layers using various methods, such as forming a layered structure through atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques, or preparing a bilayer SEI through immersion. However, these methods are often complex, time-consuming, and difficult to precisely control the thickness and uniformity of the interfacial layer, limiting their commercial application. Furthermore, the high reactivity of sodium sheets, which readily reacts with oxygen, water, and other substances, further limits the interfacial modification of sodium-ion batteries.

[0005] Based on this, the present invention proposes a method for rapidly constructing a hybrid solid electrolyte interface layer in one step using gas-liquid mixed plasma-enhanced chemical vapor deposition. Under mild reaction conditions, this method can rapidly construct an SEI layer with excellent mechanical properties and ionic conductivity, and regulate its chemical composition to effectively inhibit the growth of sodium dendrites and improve the cycling stability of the sodium metal electrode, providing an effective solution for the next generation of high-energy-density sodium metal batteries. Summary of the Invention

[0006] This invention aims to address various issues associated with the SEI layer in sodium metal battery systems. It proposes a method for preparing a composite sodium metal electrode using a one-step process to construct a hybrid SEI layer using a gas-liquid mixed plasma. By adjusting process parameters such as reaction time and radio frequency power, the resulting SEI layer can mitigate volume expansion during sodium metal deposition and inhibit the growth of sodium dendrites. A suitable SEI layer can accelerate the transport rate of sodium ions, thereby improving the battery's charge and discharge performance. It can also effectively block direct contact between sodium metal and the electrolyte, preventing excessive electrolyte decomposition and electrode corrosion.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] The present invention provides a method for preparing a sodium metal anode material by constructing a hybrid SEI layer using a one-step gas-liquid mixed plasma process. This method uses a sodium sheet as a substrate, utilizes a sulfur hexafluoride gas source and a fluoroethylene carbonate liquid source as plasma sources, and constructs the hybrid SEI layer in a single step through a vacuum plasma reaction, ultimately producing a composite sodium metal electrode. By utilizing vacuum plasma technology, the present invention effectively achieves SEI construction on the sodium sheet.

[0009] Preferably, the preparation method specifically comprises the following steps:

[0010] (1) Under a protective atmosphere, fluoroethylene carbonate (FEC) is sealed in a liquid source device, and a sodium sheet is sealed in a plasma device under a protective atmosphere;

[0011] (2) Connect the plasma device and the liquid source device, and connect them to the plasma generator, start the vacuum system to evacuate the vacuum, and pass the gas source sulfur hexafluoride SF6 into the plasma device through the liquid source device, and maintain the system at a certain vacuum degree;

[0012] (3) Regulate the RF power to excite the plasma. After ignition, sulfur hexafluoride (SF6) and fluoroethylene carbonate (FEC) plasma react on the surface of the sodium sheet. After a certain reaction time, turn off the RF power to form a composite sodium metal negative electrode (PFC@Na) with a hybrid SEI layer.

[0013] The following is a more preferred technical solution of the present invention:

[0014] Preferably, in step (1), the fluoroethylene carbonate is battery-grade fluoroethylene carbonate (FEC), and more preferably, the amount is 1-10 mL.

[0015] Preferably, in step (1), the gas source is sulfur hexafluoride.

[0016] Preferably, the sodium flakes can be conventional commercial sodium flakes, and the size of the sodium flakes is preferably 15 mm in diameter.

[0017] Preferably, in step (1), the plasma device consists of a quartz tube, a flange, and a copper ring.

[0018] Preferably, in step (2), the plasma device is evacuated to a vacuum degree of 10-20 Pa. More preferably, in step (2), after the gas source and the liquid source are introduced into the plasma device, the system maintains a vacuum degree of 15-20 Pa, more preferably 20 Pa.

[0019] Preferably, in step (2), the flow rate of sulfur hexafluoride gas is 5-30 scc / min, more preferably 20 scc / min.

[0020] Preferably, in step (2), the sulfur hexafluoride gas source is introduced into the liquid source, and the gas source and the liquid source are simultaneously introduced into the plasma device by bubbling.

[0021] Preferably, in step (3), the radio frequency power is 50-100 W, more preferably, the radio frequency power is 80-100 W, and more preferably, the radio frequency power is 90 W.

[0022] Preferably, in step (3), the plasma reaction time is 30-90 s, and more preferably, the plasma reaction time is 60 s. Too short a time or too low a power will result in SF6 and FEC not having enough time to react with the sodium metal. Conversely, the sodium metal will be damaged because it cannot withstand the violent reaction.

[0023] Preferably, the main components of the artificial hybrid solid electrolyte layer are NaF, Na2O, Na2CO3 and an organic fluorocarbon network.

[0024] Preferably, the protective atmosphere includes at least one of argon and helium.

[0025] The present invention also provides a composite sodium metal electrode prepared by any of the above preparation methods and having a hybrid SEI layer constructed in one step using gas-liquid mixed plasma.

[0026] The present invention also provides an application of a composite sodium metal electrode prepared by any of the above preparation methods in the field of sodium ion batteries in which a hybrid SEI layer is constructed in one step using a gas-liquid mixed plasma.

[0027] The present invention uses a one-step method of gas-liquid mixed plasma to quickly construct a hybrid SEI layer on the surface of sodium metal. To date, there have been no relevant reports on the application of gas-liquid mixed plasma on metallic sodium negative electrodes. The present invention evacuates the system to a certain vacuum condition and adopts vacuum plasma technology to effectively solve the problem of reaction with water, oxygen, etc. caused by the high reaction activity of sodium sheets, thereby being able to effectively react with gas sources and liquid sources to generate target SEI. The SEI layer constructed by the present invention can firmly adhere to the surface of Na foil through the Na-F bond formed by the plasma reaction, establish a dense barrier, and effectively prevent the penetration of air and moisture. In addition, the NaF inorganic SEI layer can not only guide the uniform deposition of sodium ions, but its high Young's modulus can also prevent the SEI layer from breaking or falling off during the battery cycle, reduce the side reactions of metallic sodium and the electrolyte, and the organic fluorocarbon network outer layer can enhance the flexibility and mechanical stability of the SEI layer.

[0028] The effective combination of the inorganic inner layer of sodium fluoride and the outer layer of the organic fluorocarbon network can effectively alleviate the volume change during the sodium metal deposition process, ensuring that Na + The uniformity of the flow is improved, thereby significantly suppressing the formation of sodium dendrites. After this one-step modification of the sodium metal by gas-liquid mixed plasma, it exhibits superior electrochemical performance and higher safety, laying a solid foundation for the commercial application of sodium metal batteries.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides a composite sodium metal electrode with a hybrid SEI layer constructed by a one-step gas-liquid plasma method, as well as a preparation method and application thereof. The plasma-enhanced chemical vapor deposition method is used to construct a hybrid SEI layer sodium metal negative electrode, which is completed by a single reaction between gas and liquid source plasma and the surface of metallic sodium. In this process, the organic functional groups of the organic SEI layer spontaneously form an organic fluorocarbon network, thereby enhancing the flexibility and mechanical stability of the SEI layer; the inorganic SEI layer is mainly composed of NaF, Na2O, and Na2CO3, which can evenly distribute Na at the interface. + flow.

[0031] The present invention's method for preparing PFC@Na anode materials is simple, rapid, efficient, and easily controllable, contributing to the development of artificial SEI layers in sodium metal batteries. In applications, the hybrid SEI layer acts as a physical barrier, directly isolating side reactions between sodium metal and the electrolyte. Its excellent mechanical properties also effectively inhibit the growth of sodium dendrites. Consequently, the composite anode prepared using this method exhibits excellent cycle stability, rate capability, and high coulombic efficiency. This method addresses existing issues such as solid-liquid interface instability, large volume changes, and sodium dendrite growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Attachment Figure 1 Schematic diagram of the one-step modification of sodium sheets by gas-liquid mixed plasma in Example 5;

[0033] Attachment Figure 2 is the XPS result in Example 5, Figure 2 (a)-(d) are high-resolution XPS spectra of C 1s, F 1s, Na 1s and O 1s of Example 3, respectively;

[0034] Attachment Figure 3 The cycle performance diagram of the button-type symmetrical battery assembled in Example 5 and Comparative Example 1 (3 mA / cm 2 Current density, 3 mAh / cm 2 capacity);

[0035] Attachment Figure 4 The rate performance diagram of the button-type symmetrical battery assembled in Example 5 and Comparative Example 1 (0.5, 1, 2, 3, 4, 0.5 mA / cm 2 Current density, 1 mAh / cm 2 capacity);

[0036] Attachment Figure 5 Coulombic efficiency diagram (1 mA / cm2) of the button half-cell assembled in Example 5 and Comparative Example 1 2 Current density, 1 mAh / cm 2 capacity, 50 laps);

[0037] Attachment Figure 6 The scanning electron microscope images of bare sodium and Example 5 before and after 50 cycles are shown. Figure 6 (a) and (b) are scanning electron micrographs of bare sodium and Example 5 before cycling, respectively. Figure 6 (c) and (d) are scanning electron micrographs of bare sodium and Example 5 after cycling, respectively. DETAILED DESCRIPTION

[0038] In order to better clarify and understand the purpose, process scheme and advantages of the present invention, the technical scheme and implementation method of the present invention are further clearly, completely and in detail described below through specific examples and in combination with the accompanying drawings. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical scheme of the present invention, and detailed implementation methods and specific operating processes are given, but they are only part of the embodiments of the present invention, not all of the 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 in the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] The experimental methods and conditions used in the embodiments of the present invention are conventional methods and conventional conditions unless otherwise specified. The materials, reagents, instruments, devices, etc. used in the embodiments are conventional substances or equipment known to those skilled in the art and can be obtained from commercial channels or prepared by conventional methods unless otherwise specified. The reaction conditions embodied in the summary of the invention of the present invention are all capable of achieving the described reactions and obtaining products with the desired effects. Due to space limitations, some examples are listed below to further illustrate the advantages of the technical solutions of the present invention.

[0040] Example 1

[0041] Fluoroethylene carbonate (FEC) was placed in a liquid source device in an argon-filled glove box. At the same time, a 15 mm commercial sodium sheet was sealed in a plasma device in an argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were connected to both ends of the plasma device and connected to the generator of the radio frequency power supply with wires. The plasma device was then evacuated to 20 Pa and SF6 was introduced to bring in FEC vapor. The flow rate had little effect and the gas flow rate was generally selected to be 20 sccm / min; you can refer to Figure 1 As shown in the figure, after SF6 is introduced to introduce FEC vapor, the system maintains a vacuum of 20 Pa. The RF power switch is turned on, and the RF power is adjusted to 100 W. The vacuum level within the device is also controlled at 20 Pa. After ignition, the plasma reacts with Na. After 30 seconds, a hybrid solid electrolyte interface (SEI) is formed. The RF power is then turned off, resulting in the PFC@Na anode.

[0042] Example 2

[0043] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 100 W. The vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0044] Example 3

[0045] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 100 W. The vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 90 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0046] Example 4

[0047] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 90 W, while maintaining a vacuum level of 20 Pa within the device. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 30 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0048] Example 5

[0049] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 90 W, while maintaining a vacuum level of 20 Pa within the device. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0050] Example 6

[0051] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 90 W, while maintaining a vacuum level of 20 Pa within the device. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 90 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0052] Example 7

[0053] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 80 W, while maintaining a vacuum level of 20 Pa within the device. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 30 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0054] Example 8

[0055] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 80 W, while the vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0056] Example 9

[0057] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 80 W. The vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 90 s of reaction, the RF power was turned off, resulting in the PFC@Na anode.

[0058] Comparative Example 1

[0059] A commercial sodium sheet with a diameter of 15 mm was used as the sodium metal anode. A sodium-sodium symmetric cell was assembled in an argon atmosphere glove box for electrochemical testing. The cell preparation steps described in the performance test section were used for cell preparation.

[0060] Comparative Example 2

[0061] In an argon-filled glove box, a 15 mm commercial sodium sheet was sealed inside a plasma apparatus. The plasma apparatus was then transferred outside the glove box. Copper rings were attached to both ends of the plasma apparatus and connected to the RF power generator via wires. The plasma apparatus was then evacuated to 20 Pa and SF6 was introduced. The RF power was turned on and the RF power was adjusted to 90 W, while the vacuum level within the apparatus was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form an inorganic solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PF@Na anode.

[0062] Comparative Example 3

[0063] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa and FEC vapor was introduced. The RF power was turned on and the RF power was adjusted to 90 W, while maintaining a vacuum of 20 Pa within the device. After ignition, the plasma reacted with the Na to form an organic hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PC@Na anode.

[0064] Comparative Example 4

[0065] In an argon-filled glove box, dimethyl ether (DME) was placed in a liquid source device. Simultaneously, a 15 mm commercial sodium sheet was sealed in a plasma device within the argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and SF6 was introduced to introduce DME vapor. The RF power was turned on, and the RF power was adjusted to 90 W. The vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PFE@Na anode.

[0066] Comparative Example 5

[0067] Fluoroethylene carbonate (FEC) was placed in a liquid source device within an argon-filled glove box. Simultaneously, a 15 mm commercial sodium sheet was sealed within a plasma device within the same argon-filled glove box. The plasma device was then transferred outside the glove box. Copper rings were attached to both ends of the plasma device and connected to the RF power generator via wires. The plasma device was then evacuated to 20 Pa, and nitrogen was introduced to introduce FEC vapor. The RF power was turned on, and the RF power was adjusted to 90 W, while the vacuum level within the device was maintained at 20 Pa. After ignition, the plasma reacted with the Na to form a hybrid solid electrolyte interface (SEI). After 60 s of reaction, the RF power was turned off, resulting in the PNC@Na anode.

[0068] Performance Testing

[0069] After the battery was rested for 24 h, the batteries of Examples 1-9 and Comparative Examples 1-5 were electrochemically tested using a Xinwei electrochemical workstation. Battery preparation: The electrolyte was 1 mol / L NaPF6 / DME (1:1 volume ratio, DME: ethylene glycol dimethyl ether), and the diaphragm was Celgard 2500. The battery was assembled in the order of positive electrode shell, sodium metal negative electrode material, electrolyte, diaphragm, sodium metal negative electrode material, and negative electrode shell, and sealed with a fully automatic packaging machine. The electrochemical tests were all carried out at 30°C, mainly including constant current charge and discharge tests and coulomb efficiency tests. At a current density of 3 mA / cm 2 , with a capacity of 3 mAh / cm 2 The long cycle performance of the battery was tested under the conditions of 0.5, 1, 2, 3, 4, 0.5 mA / cm 2 Current density, 1 mAh / cm 2 The rate performance of the battery was tested at a fixed capacity. The negative electrode materials of Examples 1-9 and Comparative Examples 1-5 were selected and paired with the copper positive electrode to make a sodium copper battery. 2 , with a capacity of 1 mAh / cm 2 After 100 cycles under the conditions of , the Coulomb efficiency was tested.

[0070] Table 1 Summary of battery performance of Examples 1-9 and Comparative Examples 1-5

[0071]

[0072] The present invention rapidly constructs an inorganic-organic hybrid solid electrolyte layer on the surface of sodium metal through a plasma one-step method and a gas-liquid mixed plasma one-step method.

[0073] The inorganic sodium fluoride layer of the SEI layer can improve the thermodynamic stability of the sodium metal negative electrode and inhibit the growth of sodium dendrites. The stability of the SEI layer on the sodium negative electrode is related to the electrochemical performance of the sodium negative electrode. Rich inorganic SEI can make the electrochemical performance of the sodium negative electrode better and make the SEI volume change smaller. The NaF surface is sodium-philic and guides the Na electrodeposition through the Na-NaF interaction; NaF reduces the Na in the electrolyte. + Solvent interaction produces a weak solvation environment; NaF promotes Na + transport and promote the reversible electrochemical reactions in the full cell.

[0074] pass Figure 2 (a)-(d) are respectively the high-resolution XPS spectra of C 1s, F 1s, Na 1s and O 1s of Example 5. It can be seen from the analysis of the organic fluorocarbon network layer of the SEI layer that the organic fluorocarbon network layer forms covalent bonds (CF x) firmly adhere to the sodium metal surface and connect to the SEI layer through chemical bonds and physical entanglement. This achieves a good connection between the two different materials, sodium metal and SEI layer. In addition to chemical bonds, the physical entanglement effect of the SEI layer also contributes to good adhesion. In short, FEC molecules bridge the two materials through chemical bonds and physical entanglement, enhancing the adhesion of the SEI layer to the sodium metal substrate. The flexibility and elasticity of the organic SEI layer enable it to withstand the stress applied during the sodium plating / stripping process, thereby avoiding a series of problems caused by sodium dendrites that cause the SEI layer to rupture.

[0075] pass Figure 6 , Figure 6 (a) is the scanning electron microscope image of the sodium sheet before recycling. It can be seen that the original sodium sheet has a more irregular planar structure. Figure 6 (b) The plasma-modified sodium sheet is denser and smoother. Figure 6 (c) and Figure 6 (d) in the figure are scanning electron microscope images of bare sodium and Example 5 after 50 cycles. From the SEM images of bare sodium and Example 5 before and after the cycle, it can be seen that the sodium dendrites formed in Example 5 after the cycle are smoother and less than those after the bare sodium cycle, indicating that PFC@Na can better resist the formation of sodium dendrites. Figure 3 It can be seen from the cycle performance graphs of the button-type symmetrical batteries of Example 5 and Comparative Example 1 that the hybrid SEI layer is constructed by a one-step gas-liquid mixed plasma method, and the surface mechanical properties are more excellent, which significantly inhibits the growth of sodium dendrites, thereby achieving a lower overpotential in a long cycle and Figure 4 The rate performance graph of the button-type symmetrical battery of Example 5 and Comparative Example 1 shows that Example 5 also exhibits a lower overpotential under high rate conditions. Figure 5 From the coulombic efficiency diagrams of the button half-cells assembled in Example 5 and Comparative Example 1, it can be seen that Example 5, in which the hybrid SEI layer is constructed by a one-step gas-liquid mixed plasma method, also exhibits a more excellent coulombic efficiency.

[0076] Through the analysis of the above table, it can be seen that when the RF power is outside 90 W, such as 100 W in Examples 1-3 and 80 W in Examples 7-9, although SEI@Na can be formed, its electrochemical performance, such as cycle stability, overpotential or coulombic efficiency, is slightly inferior to that of Examples 4-6. At the same time, it can be seen from the comparison of Examples 1-9 that when the reaction time is outside 60 s, such as 30 s in Examples 1, 4, and 7 and 90 s in Examples 3, 6, and 9, although SEI@Na can be formed, its electrochemical performance, such as cycle stability, overpotential or coulombic efficiency, is slightly inferior to that of Examples 2, 5, and 8, indicating that the RF power is maintained at 90 W and the ignition reaction time is 60 s as the optimal conditions, indicating that the SEI@Na formed within this range has good cycle stability and can inhibit the growth of sodium dendrites. The experimental data of Comparative Examples 1-5 show that the PFC@Na formed within the same time range has better electrochemical performance, thereby illustrating the superiority of the hybrid SEI layer constructed by the one-step method of the gas-liquid mixed plasma of the present invention.

[0077] The present invention uses a one-step gas-liquid mixed plasma method to quickly construct a hybrid SEI layer on the surface of sodium metal in situ. The effective combination of the inorganic inner layer and the organic outer layer can alleviate the volume change during the deposition of metallic sodium and improve the Na at the uniform interface. + The plasma-modified sodium sheets exhibit superior electrochemical performance and safety, potentially paving the way for the commercialization of sodium metal batteries. Electrochemical tests demonstrate that the sodium metal anode material modified by the gas-liquid hybrid plasma one-step method exhibits excellent cycling stability.

[0078] The SEI layer, formed by a one-step gas-liquid mixed plasma process, exhibits excellent mechanical strength and electrochemical stability, and can inhibit the growth of sodium dendrites. It has broad application prospects in small mobile electronic devices, electric vehicles, solar power generation, and aerospace.

[0079] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

Claims

1. A method for preparing a sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step gas-liquid mixed plasma method, characterized in that: The method uses a sodium sheet as a matrix, utilizes a sulfur hexafluoride gas source and a fluoroethylene carbonate liquid source as plasma sources, and constructs a hybrid solid electrolyte interface layer in one step through a plasma reaction to obtain a composite sodium metal electrode. The radio frequency power of the reaction is 50-100 W, the vacuum degree is 15-20 Pa, and the reaction time is 30-90 seconds. The steps include: (1) Sealing the liquid source into the liquid source device under a protective atmosphere, and sealing the sodium sheet in the plasma device; (2) connecting the plasma device and the liquid source device to the plasma generator, then evacuating the plasma device, introducing the gas source, and bringing the liquid source into the plasma device; (3) adjusting the radio frequency power and reacting for a period of time after ignition to form a composite sodium metal electrode with a hybrid solid electrolyte interface layer; In step (2), the gas flow rate is 5-30 scc / min.

2. The method for preparing a sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step method based on a gas-liquid mixed plasma according to claim 1, characterized in that: The fluoroethylene carbonate is fluoroethylene carbonate of battery-grade concentration.

3. The method for preparing a sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step gas-liquid mixed plasma method according to claim 1, characterized in that: The radio frequency power is 80-100 W, the vacuum degree is 20 Pa, and the reaction time is 30-60 seconds.

4. The method for preparing a sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step method based on a gas-liquid mixed plasma according to claim 3, characterized in that: The radio frequency power was 90 W, the vacuum degree was 20 Pa, and the reaction time was 60 s.

5. The method for preparing a sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step method based on a gas-liquid mixed plasma according to claim 1, characterized in that: In step (2), the vacuum degree of the plasma device is 15-20 Pa.

6. A sodium metal negative electrode material prepared by the preparation method according to any one of claims 1 to 5, wherein a hybrid solid electrolyte interface layer is constructed by a one-step method based on gas-liquid mixed plasma.

7. Application of the sodium metal negative electrode material with a hybrid solid electrolyte interface layer constructed by a one-step method based on gas-liquid mixed plasma according to claim 6 in the field of batteries.

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