Multi-Scale Simulation Revealing the Decomposition Mechanism of Electrolyte on Lithium Metal Electrode

Authors

Yan-Yan Zhang, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Yue Liu, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Yi-Ming Lu, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Pei-Ping Yu, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Wen-Xuan Du, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Bing-Yun Ma, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Miao Xie, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Hao Yang, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;
Tao Cheng, Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123, Jiangsu, China;Follow

Corresponding Author

Tao Cheng(tcheng@suda.edu.cn)

Abstract

Lithium metal is considered as an ideal anode material for next-generation high energy density batteries with its high specific capacity and low electrode potential. However, the high activity of lithium metal can lead to a series of safety issues. For example, lithium metal will continuously react chemically with the electrolyte, forming unstable the solid electrolyte (SEI) films. In addition, lithium dendrites can be formed during cycling, which can puncture the SEI film and cause short circuits in the battery. These drawbacks greatly hinder the commercial application of lithium metal. To solve the above problems, it is important to understand the structure of SEI and the underlying mechanism of its formation as a guide for rational design. Quantum mechanics (QM) has been demonstrated as an effective tool to investigate the chemical reactions and microscopic atomic structures of SEI. However, QM is computationally too expensive to be used for large-scale and long-term theoretical simulations. Instead, the molecular mechanics (MM) method has much orders higher computational efficiency than QM, and can be used for large-scale and long-time theoretical simulations. However, the accuracy of MM is usually not guaranteed, especially for complex SEI. Therefore, a practical solution is to combine the advantages of both. In this work, we use the hybrid ab initio and reactive molecule dynamics (HAIRs) approach to describe chemical reactions with the accuracy of quantum chemistry and improve the computational efficiency by more than 10 times with mixing QM and MM. Using this method, we have investigated the interfacial reaction mechanism of two electrolyte solutions, 1 mol·L^-1 LiTFSI-DME (dimethoxyethane) and 1 mol·L^-1 LiTFSI-EC (ethylene carbonate) with the lithium metal anode. The simulation results show that TFSI anion prefers to be decomposed, while DME does not, thus, TFSI plays the vital role of protecting DME. However, in the LiTFSI-EC system, both TFSI anion and EC are decomposed, indicating that EC is less stable and not suitable to the formation of stable SEI. Thanks to the computational efficiency of the HAIRs method, we have completed the 1 ns simulation in a few days. Using the hardware, the above calculation would take at least one to two months if only the QM method was employed. Meanwhile the long HAIRs calculation shows that for the simulation of chemical reactions in SEI, at least 1 ns is essential. Instead, previous molecular dynamics (MD) simulations with a few ps, or tens of ps, are insufficient to fully capture the critical chemical reactions. The above simulation results provide reliable experience for the computational simulation study of SEI formation, and lay the theoretical foundation for the rational design of electrolytes and the development of high-performance electrolyte solution systems.

Graphical Abstract

Keywords

lithium metal battery, solid electrolyte interface, multi-scale theoretical simulation, electrochemical reaction, electrolyte design

DOI Link

https://doi.org/10.13208/j.electrochem.210518

Publication Date

2022-04-28

Online Available Date

2022-04-28

Revised Date

2021-08-04

Received Date

2021-05-18

Recommended Citation

Yan-Yan Zhang, Yue Liu, Yi-Ming Lu, Pei-Ping Yu, Wen-Xuan Du, Bing-Yun Ma, Miao Xie, Hao Yang, Tao Cheng. Multi-Scale Simulation Revealing the Decomposition Mechanism of Electrolyte on Lithium Metal Electrode[J]. Journal of Electrochemistry, 2022 , 28(4): 2105181.
DOI: 10.13208/j.electrochem.210518
Available at: https://jelectrochem.xmu.edu.cn/journal/vol28/iss4/6