Synergistic optimization of a compound electrolyte additive for the solid electrolyte interface in lithium metal batteries

Fluorosubstituted compounds are widely employed in lithium batteries as electrolyte additives to create stable interfaces. However, the composition of inorganic and organic components in the solid electrolyte interface (SEI) has received limited attention. This study introduces a composite additive consisting of fluoroethylene carbonate (FEC) and N, O-bis(trimethylsily)trifluoroamide (BSTFA). By balancing organic and inorganic constituents in the SEI, a high-performance lithium metal anode is achieved. Besides assessing the performance of lithium metal batteries using a composite additive at a high loading (∼6 mg cm −2 ) and voltage (4.3 V), their performance under more rigorous conditions such as increased loading (∼12 mg cm −2 ), elevated temperature (55 °C), and high voltages (4.6 V, 4.7 V, and 4.8 V), is also evaluated. Furthermore, this approach demonstrates applicability in high-loading lithium nickel manganese oxide (LNMO) battery systems. The synergistic effects of the composite additive are substantiated from various perspectives, offering essential insights and basic data for the commercial application of lithium metal batteries.