Moderately concentrated electrolyte enabling high-performance lithium metal batteries with a wide working temperature range

The electrolyte integrated with lithium metal anodes is subjected to the issues of interfacial compatibility and stability, which strongly influence the performances of high-energy lithium metal batteries. Here, we report a new electrolyte recipe viz. a moderately concentrated electrolyte comprising of 2.4 M lithium bis (fluorosulfonyl)imide (LiFSI) in a cosolvent mixture of fluorinated ethylene carbonate (FEC) and dimethyl carbonate (DMC) with relatively high ion conductivity. Owing to the preferential decomposition of LiFSI and FEC, an inorganic-rich interphase with abundant Li2O and LiF nanocrystals is formed on lithium metal with improved robustness and ion transfer kinetics, enabling lithium plating/stripping with an extremely low overpotential of ti 8 mV and the average CE of 97%. When tested in Li||LiFePO4 cell, this electrolyte provides long-term cycling with a capacity retention of 98.3% after 1000 cycles at 1 C and an excellent rate performance of 20 C, as well as an areal capacity of 1.35 mA h cm-2 at the cathode areal loading of 9 mg cm-2. Moreover, the Li||LiFePO4 cell exhibits excellent wide-temperature performances (-40 ti 60 t), including long-term cycling stability over 2600 cycles without visible capacity fading at 0 t, as well as extremely high average CEs of 99.6% and 99.8% over 400 cycles under-20 t and 45 t. (c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

In this study, a new electrolyte recipe comprising a moderately concentrated electrolyte with 2.4 M lithium bis(fluorosulfonyl)imide (LiFSI) in a cosolvent mixture of fluorinated ethylene carbonate (FEC) and dimethyl carbonate (DMC) was developed for lithium metal batteries. The electrolyte enabled the formation of an inorganic-rich interphase on the lithium metal anode, improving stability and ion transfer kinetics. The electrolyte exhibited low overpotential for lithium plating/stripping and high cycling efficiency, and showed excellent long-term cycling performance and high rate capability in Li||LiFePO4 cells.