Ammonium silicofluoride as bifunctional electrolyte additive to regulate the electrode interface in lithium-sulfur battery

The passivation and corrosion of active interface of cathode and lithium anode caused by the uncontrollable deposition of discharged product (Li 2 S 2 /Li 2 S) in lithium-sulfur (Li-S) batteries lead to deterioration cycling stability and increase voltage polarization. Herein, ammonium silicofluoride (NH 4 ) 2 SiF 6 is demonstrated as an effective soluble ammonium salt to enhance the solvation of Li 2 S, resulting from the inductive effect of NH 4 + cation. In particular, the addition of (NH 4 ) 2 SiF 6 stabilizes the lithium metal interface through the formation of LiF-rich robust SEI. Due to these advantages, excellent cyclic stability is shown in the Li-S cells with (NH 4 ) 2 SiF 6 -based electrolyte and the long cycle tests of 0.5 C and 2 C. The proposal of (NH 4 ) 2 SiF 6 provides a new avenue to solve the interface problem of Li-S cells and stimulates the research enthusiasm for developing soluble ammonium salt.