Atomistic insights into dynamic evolution of solid electrolyte interface

YL Chen and YX Fan and YQ Gong and CL Gao and YH Huang and W Luo and MH Yang, JOURNAL OF ENERGY CHEMISTRY, 111, 401-411 (2025).

DOI: 10.1016/j.jechem.2025.07.058

Lithium-ion batteries are at the forefront of modern energy storage technology. However, the accumulation of by-products such as ethylene and carbon dioxide during charging and discharging cycles reduces battery effective capacity and threatens large-scale safe performance. With significant advantages over ethylene carbonate (EC) electrolytes, fluorinated electrolytes can more effectively suppress internal gas evolution, thereby improving battery safety and cycling stability. To reveal the mechanism behind gas formation in lithium-ion batteries, our study investigated the transport behavior and interfacial products of fluorinated electrolytes under various operation conditions, including electrode material and electrolyte composition. Innovatively, we applied the reaction network integrator ReacNetGenerator to the analysis of the solid electrolyte interface (SEI) in lithium batteries, providing more molecular fingerprint information from the perspective of specific products. Using reactive molecular dynamics (MD) simulations with the ReaxFF force field and EChemDID, complemented by density functional theory (DFT) calculations, our results demonstrate that fluorinated electrolytes can effectively suppress the decomposition of LiPF6 to produce toxic gases PF5 and PF3. DFT analysis further reveals that highly fluorinated solvents (e.g., FEMC) enhance the anti-reduction stability of PF6- through synergistic regulation of molecular orbital energy levels, thermodynamic electron affinity, charge transfer, and electrostatic potential distribution, thereby mitigating LiPF6 decomposition. Additionally, fluorinated electrolytes generate significantly more LiF components than non-fluorinated ones to promote the formation of a stable and durable solid electrolyte interface (SEI). Experimental validations via XPS and GC-MS confirm reduced CO2 generation and LiF-enriched SEI formation, aligning with simulation and DFT data. The findings provide valuable insights for the design of advanced electrolytes aimed at ensuring large-scale, safe energy storage solutions. (c) 2025 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published byElsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AItraining, and similar technologies.

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