Partially sacrificial hybrid diluent regulated electrolytes boosting wide-temperature Li metal batteries

Abstract

Designing electrolytes with superior interface compatibility for high-voltage and wide-temperature Li metal batteries (LMBs) is still challenging. Herein, a partially sacrificial hybrid diluent consisting of minor active diluent 1,3,5-trifluorobenzene (TFB) and main inert diluent fluorobenzene (FB) is proposed to regulate tetramethylene sulfone (TMS)-based localized high-concentration electrolyte (LHCE-FB-TFB) to tune the chemical activity at the electrolyte/electrode interfaces. The prior sacrificial decomposition of TFB with high LiF yielding activity cooperates with bis(fluorosulfonyl)imide (FSI⁻) anions to construct thin and durable LiF-rich solid-electrolyte interphases (SEIs) and cathode electrolyte interphases (CEIs), dramatically enhancing interface stability of Li metal anodes and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes in a wide temperature range. Relatively inert low-viscosity FB exhibits powerful dilution effect, and endows the electrolyte with low viscosity and high ionic kinetics at low temperature, wide liquid range (−75∼60 °C), and favorable wettability. Li metal anodes with LHCE-FB-TFB achieve extremely stable and high-efficiency (99.3 %) cycles. LHCE-FB-TFB enables NCM811||Li cells with superior cycle performance under harsh conditions, including high voltage (4.5 V), wide temperature range from −20 °C to 60 °C, high areal capacity (3.6 mAh cm⁻²) and thin Li metal anode (50 μm). This work provides a promising strategy for the design of high-efficiency electrolytes for wide-temperature batteries.