A LiF-Rich Solid Electrolyte Interphase in a Routine Carbonate Electrolyte by Tuning the Interfacial Chemistry Behavior of LiPF₆ for Stable Li Metal Anodes

Lithium (Li) dendrite growth in a routine carbonate electrolyte (RCE) is the main culprit hindering the practical application of Li metal anodes. Herein, we realize the regulation of the LiPF6 decomposition pathway in RCE containing 1.0 M LiPF6 by introducing a “self-polymerizing” additive, ethyl isothiocyanate (EITC), resulting in a robust LiF-rich solid electrolyte interphase (SEI). The effect of 1 vol % EITC on the electrode/electrolyte interfacial chemistry slows the formation of the byproduct LixPOFy. Such a LiF-rich SEI with EITC polymer winding exhibits a high Young’s modulus and a uniform Li-ion flux, which suppresses dendrite growth and interface fluctuation. The EITC-based Li metal cell using a Li4Ti5O12 cathode delivers a capacity retention of 81.4% over 1000 cycles at 10 C, outperforming its counterpart. The cycling stability of 1 Ah pouch cells was further evaluated under EITC. We believe that this work provides a new method for tuning the interfacial chemistry of Li metal through electrolyte additives.