Usefulness of uselessness: Teamwork of wide temperature electrolyte enables LFP/Li cells from -40 °C to 140 °C

Abstract

Lithium secondary battery with a wide working temperature range is crucial to boost its increasing applications in harsh circumstances. Suppressing excessive electrolyte decomposition at high temperatures while maintaining reasonable electrochemical kinetics at low temperatures is critical for wide-temperature electrochemical performance. Construction of high temperature stable electrode-electrolyte interface layer by electrolyte formulation is an effective strategy to prevent electrolyte from uncontrollable decomposition. On the contrary to conventional thinking, propylene carbonate (PC) bearing poor filming ability to suppress electrolyte decomposition is used in this work to promote decomposition of the single lithium difluoro(oxalate)borate (LiODFB) salt in the electrolyte, producing inorganic-rich interface layer with good structure stability over a wide temperature range. Glutaronitrile (GLN) is further utilized to minimize the decomposition of PC by expelling PC out of the solvation sheath of lithium-ion. The teamwork of LiODFB, PC, and GLN makes a synergistic contribution to building a high-temperature stable electrode-electrolyte interface layer at both LFP and MCMB electrodes. Based on the approach developed in this work, the temperature window is successfully expanded to the range of from -40 °C to 140 °C. Excellent electrochemical performance is exhibited by both LFP/Li and MCMB/Li cells from -20 °C to 100 °C in terms of reversible capacity and cyclic stability.