Low-temperature and fast-charge lithium metal batteries enabled by a robust interphase via a dual-additive synergistic strategy

Abstract

Combining lithium iron phosphate (LFP) with lithium anodes is crucial to achieve high-safety batteries. However, the capacity degradation of batteries at low temperatures, generally caused by unexpected parasitic reactions at the interphase and slow kinetics during the transport process, need to be addressed. Herein, a dual-additive synergistic strategy was developed through the strategic incorporation of an appropriate amount of tris(trimethylsilyl) borate (TMSB) and LiPF₆ in a carbonate electrolyte, aiming to precisely engineer the interphase structure for enhanced electrochemical performance. Corrosion of the Al collector was mitigated by a cathode−electrolyte interphase (CEI) formed via the decomposition of LiPF₆, thereby enhancing the cyclability. This CEI effectively facilitated smooth Li⁺ migration by armor-like cathode electrolyte interphase with B–O, LiF, and Li₃PO₄-rich part. As a result, the Li‖LFP cell with dual additives shows exceptional cycle stability and improved rate capability at a low temperature (−20 °C) while maintaining 80% of its initial capacity after 800 cycles at 4C and room temperature. Our study offers a systematic guideline to design electrolytes with fast-charge properties by regulating solvation microstructures and interphases via targeted dual-additive formulation engineering.