An electrolyte additive capable of scavenging HF and PF5 enables fast charging of lithium-ion batteries in LiPF6-based electrolytes

Abstract

Fast-charging lithium-ion batteries (LIBs) can be achieved using structurally optimized electrodes and electrolytes. Electrolytes largely affect the interfacial structures of electrodes that are critical to reducing charging time of LIBs without sacrificing battery durability. However, most widely used LiPF6-based electrolytes suffer from reactive species, such as HF and PF5, that seriously damage interfacial structures of electrodes on repeated cycling and form resistive species at the electrode surface that hamper the fast charging of LIBs. To resolve these detrimental effects of LiPF6-based electrolytes, we report an electrolyte additive, (trimethylsily)isothiocyanate (TMSNCS) based on aminosilane, with a high electron donating ability that can scavenge HF and PF5. TMSNCS effectively deactivates reactive species and attains long-term stability of interfacial layers formed on anodes and cathodes in LiPF6-based electrolytes. After 300 cycles at a 2C charge rate and a 1C discharge rate, the NCM622/graphite full cell with 0.1% TMSNCS delivers a superior discharge capacity of 144 mAh/g and exhibits an excellent capacity retention of 91.8%. Furthermore, the stabilization of PF5 by the TMSNCS additive drastically alleviates undesired decomposition reactions of fluoroethylene carbonate (FEC) and enhances high-temperature performances of the FEC-containing full cells.