Enhancing the Interfacial Stability of High-Energy Si/Graphite | | LiNi0.88Co0.09Mn0.03O2 Batteries Employing a Dual-Anion Ionic Liquid-based Electrolyte

The poorly flammable room-temperature ionic liquid-based electrolyte composed of lithium bis(trifluoromethanesulfonyfiimide (LiTFSI) and N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr(14)FSI) with fluoroethylene carbonate (FEC) as an additive is investigated towards its compatibility with the LiNN0.88Co0.09Mn0.03O2 (NCM88) cathode and a high-capacity Si/graphite (SiG) anode, revealing a remarkably stable performance in lithium-ion cells. Interestingly, this dual-anion electrolyte with FEC additive forms a stable electrode-electrolyte interphase on both sides, which sup- presses the morphological degradation of the electrode materials and continuous electrolyte decomposition. Consequently, lithium-ion cells using such dual-anion ionic liquid-based electrolyte display significantly improved cycling stability compared to conventional carbonate ester-based electrolyte, achieving a high specific energy of 385 Wh kg(-1) (based on both cathode and anode active materials weight) with a capacity retention of 74% after 200 cycles at 0.2 C, demonstrating the possibility to realize safe and high energy density LIBs.

Automated summary

A dual-anion electrolyte based on a poorly flammable room-temperature ionic liquid has been found to exhibit stable performance in lithium-ion cells, suppressing electrode material degradation and electrolyte decomposition. This electrolyte shows significantly improved cycling stability and high energy density, demonstrating the potential for safe and high-energy lithium-ion batteries.