A Mg-containing 1-x Li x PEO composite solid electrolyte membrane with F2 filler, its preparation method and application

Abstract

This invention discloses a Mg-containing 1‑x Li x This paper describes a PEO composite solid electrolyte membrane with F2 filler, its preparation method, and its application, belonging to the field of solid electrolyte technology for lithium metal batteries. The composite solid electrolyte comprises a PEO polymer matrix, LiTFSI lithium salt, and Mg. 1‑x Li x F2 inorganic filler. The Mg 1‑x Li x F2 filler is obtained by treating MgF2 with a mixed solution of acetonitrile, LiTFSI, and dimethyl sulfoxide. The Mg on the surface of MgF2 contains... 2+ The empty space was occupied by Li + Filling forms a large amount of Li Mg Defects. The Mg 1‑x Li x The F2 filler and PEO form an interfacial interaction region at the interface that is conducive to lithium-ion transport, thereby improving lithium-ion migration performance. Simultaneously, a LiF-rich interfacial layer is formed at the lithium metal interface to suppress lithium dendrite growth. This composite solid-state electrolyte can be applied to Li||Li, Li||LFP, and Li||NCM811 all-solid-state lithium metal battery systems, exhibiting excellent near-room temperature and low-temperature electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery and solid electrolyte technology, specifically relating to a Mg-containing electrolyte. 1-x Li x PEO composite solid electrolyte membrane with F2 filler, its preparation method and its application in all-solid-state lithium metal batteries. Background Technology

[0002] All-solid-state lithium metal batteries combine high energy density and high safety, and are considered an important development direction for next-generation energy storage devices. However, polymer-based solid electrolytes generally suffer from low ionic conductivity, low lithium-ion transference number, and unstable electrode / electrolyte interfaces at near-room temperature, especially at low temperatures, which severely limits their practical applications. Although polymer-inorganic composite solid electrolytes can improve mechanical properties and interfacial compatibility to some extent, existing research mostly focuses on reducing polymer crystallinity or introducing additional ion transport channels, and the regulation of the lithium-ion coordination environment and its desorption and migration processes at the filler / polymer interface remains insufficient.

[0003] In existing technologies, while conventional inert or active inorganic fillers can improve the overall performance of polymer electrolytes, they typically struggle to simultaneously achieve high ionic conductivity, high lithium-ion transport number, and a stable lithium metal interface at low temperatures. Therefore, developing a novel composite solid-state electrolyte capable of controlling lithium-ion coordination and transport behavior at the interface scale is of great significance for realizing all-solid-state lithium metal batteries with stable operation at low temperatures. Summary of the Invention

[0004] The purpose of this invention is to address the problems of low ionic conductivity, low lithium-ion transference number, and poor lithium metal interface stability in polymer-based solid electrolytes under near-room temperature and low-temperature conditions, and to provide a Mg-containing electrolyte. 1-x Li x PEO composite solid electrolyte membrane with F2 filler, its preparation method, and its application. The composite solid electrolyte membrane can improve lithium-ion transport performance and lithium metal interface stability while maintaining polymer flexibility, thus making it suitable for low-temperature operating all-solid-state lithium metal batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a Mg-containing... 1-x Li x F2-filled PEO composite solid electrolyte membrane, its preparation method and application, wherein the composite solid electrolyte membrane comprises a polyethylene oxide polymer matrix, a lithium salt and Mg dispersed in the polyethylene oxide polymer matrix. 1-x Li x F2 inorganic filler; wherein, the Mg 1-x Li xF2 inorganic filler is formed by treating MgF2 in a system containing acetonitrile and dimethyl sulfoxide, and the surface of the inorganic filler has Li Mg It can eliminate defects and form an interface structure with polyethylene oxide segments in the interface region that is conducive to lithium-ion transport, thereby reducing the degree of lithium-ion binding at the interface and promoting lithium-ion migration.

[0006] The present invention also provides a method for preparing the above-mentioned composite solid electrolyte, comprising the following steps: 1) Add MgF2 powder to acetonitrile, then add dimethyl sulfoxide, and treat under heating and stirring conditions at 60 °C to obtain a filler system containing Mg vacancy precursor characteristics; 2) Add polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) to the system, and continue heating and stirring to obtain a homogeneous electrolyte precursor solution; 3) The precursor solution was poured into a polytetrafluoroethylene mold and dried under vacuum to obtain PEO / LiTFSI-Mg. 1- x Li x F2 composite solid electrolyte membrane.

[0007] This invention provides a Mg-containing 1-x Li x The PEO composite solid electrolyte membrane with F2 filler, its preparation method, and its application have the following advantages compared with existing technologies: 1) The preparation method is simple and the conditions are mild. This invention uses MgF2, acetonitrile and a small amount of dimethyl sulfoxide to construct a precursor system, which is then directly composited with PEO and LiTFSI to form a film. The process route is simple, the preparation conditions are mild, and it is easy to scale up. 2) It can significantly improve the ion transport performance of the composite electrolyte. The composite solid electrolyte obtained in this invention can achieve approximately 0.158 mS / cm at 30℃. -1 The ionic conductivity and lithium-ion transference number of approximately 0.56 are significantly better than those of the PEO / LiTFSI control system without MgF2. 3) It can significantly improve the stability of the lithium metal interface and the low-temperature cycling stability. After the composite solid electrolyte of this invention comes into contact with lithium metal, it can form a LiF-rich interface layer, reduce the interface impedance and suppress lithium dendrite growth, enabling the Li||Li symmetric battery to achieve long-term stable cycling at room temperature and below. Attached Figure Description

[0008] Figure 1 PEO / LiTFSI-Mg in Example 1 1-x Li x Arrhenius curves of F2 composite solid electrolyte at different temperatures; Figure 2PEO / LiTFSI-Mg in Example 1 1-x Li x DC polarization curve of F2 composite solid electrolyte at 30 °C; Figure 3 The PEO / LiTFSI-Mg in Example 1 of this invention 1-x Li x The long-cycle performance of Li||Li symmetric cells assembled with F2 composite solid electrolyte as electrolyte at 0 °C; Figure 4 The PEO / LiTFSI-Mg in Example 1 of this invention 1-x Li x Long-cycle performance of Li||LFP full cells assembled with F2 composite solid electrolyte at 0 °C; Figure 5 The PEO / LiTFSI-Mg in Example 1 of this invention 1-x Li x The long-cycle performance of Li||NCM811 full cells assembled with F2 composite solid electrolyte as electrolyte at 30 °C. Detailed Implementation

[0009] The present invention will now be described with reference to the following specific embodiments, but the technical solution of the present invention is not limited to the specific embodiments listed below.

[0010] Example 1 This embodiment prepares PEO / LiTFSI-Mg according to the following steps. 1-x Li x F2 composite solid electrolyte membrane: 1) Add 10 mg of MgF2 powder to 10 mL of acetonitrile, then add 30 μL of dimethyl sulfoxide, and stir for 12 h in a water bath at 60 °C to obtain a filler precursor system treated with dimethyl sulfoxide; 2) Add 0.375 g polyethylene oxide (PEO, Mw≈600000) and 0.12 g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to the system obtained in step (1), and continue stirring in a water bath at 60 ℃ for 12 h to obtain a homogeneous electrolyte precursor solution; 3) Pour the above precursor liquid into a polytetrafluoroethylene mold and dry it under vacuum at 60 °C for 24 h to obtain the target PEO / LiTFSI-Mg. 1-x Li x F2 composite solid electrolyte membrane.

[0011] Tests showed that the composite solid electrolyte membrane could achieve a flux density of approximately 0.158 mS / cm at 30 °C. -1 ionic conductivity ( Figure 1 ) and a lithium-ion transference number of approximately 0.56 ( Figure 2 This indicates that the composite electrolyte membrane obtained by the preparation method has excellent ion transport performance.

[0012] Comparative Example 1

[0013] This comparative example is basically the same as Example 1, except that MgF2 is not added in step (1), while the other steps remain the same. The final control electrolyte membrane is obtained, denoted as PEO / LiTFSI. The PEO / LiTFSI electrolyte obtained in this comparative example is compared with the PEO / LiTFSI-Mg electrolyte obtained in Example 1. 1-x Li x Compared with the F2 composite solid electrolyte, it can be seen that the composite solid electrolyte of Example 1 has a lower ionic conductivity ( Figure 1 It is superior to the control system in terms of lithium-ion transference number and low-temperature cycling stability.

[0014] Application Example 1

[0015] Application in Li||Li symmetric cells: PEO / LiTFSI-Mg prepared in Example 1 1-x Li x A Li||Li symmetric battery was assembled using an F2 composite solid electrolyte membrane. Test results show that this electrolyte can form a LiF-rich interface layer at the lithium metal interface, effectively reducing interface impedance and suppressing lithium dendrite growth. At 0 °C, the assembled Li||Li symmetric battery achieved stable cycling for over 2650 h. Figure 3 In contrast, the PEO / LiTFSI solid electrolyte membrane prepared using Comparative Example 1 struggled to maintain stable operation at low temperatures.

[0016] Application Example 2

[0017] Application in Li||LFP full cells: PEO / LiTFSI-Mg prepared in Example 1 1-x Li x A Li||LFP full cell was assembled using an F2 composite solid electrolyte membrane. Test results showed that the full cell retained approximately 85% of its capacity after 300 cycles at 30 °C and approximately 98% of its capacity after 300 cycles at 0 °C. Figure 4 The above results indicate that the composite solid electrolyte membrane of the present invention is suitable for low-temperature all-solid-state lithium metal batteries.

[0018] Application Example 3:

[0019] Application in Li||NCM811 full cells: PEO / LiTFSI-Mg prepared in Example 1 1-x Li xA Li||NCM811 full cell was assembled using an F2 composite solid electrolyte membrane. Test results showed that the full cell retained approximately 72% of its capacity after 500 cycles at 30 °C. Figure 5 This indicates that the composite solid electrolyte membrane of the present invention is not only suitable for low-temperature systems, but can also meet the usage requirements of high-voltage positive electrode systems.

Claims

1. A Mg-containing 1-x Li x The method for preparing a PEO composite solid electrolyte membrane with F2 filler is characterized by, Includes the following steps: 1) Add MgF2 powder to acetonitrile, then add dimethyl sulfoxide, and stir at 60 °C. 2) Add polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) to the system obtained in step 1), and continue stirring at 60 °C to obtain a homogeneous precursor solution; 3) The precursor solution was poured into a polytetrafluoroethylene mold and dried under vacuum to obtain PEO / LiTFSI-Mg. 1- x Li x F2 composite solid electrolyte membrane.

2. The PEO / LiTFSI-Mg according to claim 1 1-x Li x The method for preparing F2 composite solid electrolyte membrane is characterized by, In step 1), the amount of MgF2 powder added is 5-20 mg, the amount of acetonitrile added is 5-15 mL, the amount of dimethyl sulfoxide added is 40-50 μL, and the stirring time is 6-12 h.

3. The PEO / LiTFSI-Mg according to claim 1 1-x Li x The method for preparing F2 composite solid electrolyte membrane is characterized by, In step 2), the amount of polyethylene oxide added is 0.3-0.5 g, the amount of lithium bis(trifluoromethanesulfonylimide) added is 0.05-0.20 g, and the stirring time is continued for 6-12 h.

4. A PEO / LiTFSI-Mg prepared by the method according to claim 1 1-x Li x F2 composite solid electrolyte membrane, characterized in that, The composite solid electrolyte membrane comprises a polyethylene oxide polymer matrix, lithium bis(trifluoromethanesulfonyl)imide, and Mg dispersed in the polyethylene oxide polymer matrix. 1-x Li x F2 inorganic packing.

5. The PEO / LiTFSI-Mg according to claim 4 1-x Li x F2 composite solid electrolyte membrane, characterized in that, The composite solid electrolyte membrane forms a LiF-rich interface layer at the interface after it comes into contact with lithium metal.

6. A lithium metal battery, characterized in that, Including the PEO / LiTFSI-Mg as described in claim 4 1-x Li x F2 composite solid electrolyte membrane.

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