Nonflammable F/N synergistic electrolyte boosting high-voltage Li metal batteries in wide temperature range

Abstract

High-voltage Li metal batteries are promising energy storage technologies owing to their high energy densities (>400 Wh kg⁻¹). However, high-voltage Li metal batteries with conventional electrolytes suffer from poor interface stability, inferior cycle performance and low security. Herein, we develop a rational design of nonflammable fluorinated amide electrolyte via the synergetic combination of F/N donating solvents to construct robust and highly conductive solid electrolyte interphases (SEIs) and cathode-electrolyte interphases (CEIs) with high LiF and Li₃N content, which effectively enhance the interfacial stability and ionic conductivity of Li metal anodes and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes. More anions are brought into the primary solvation shell of Li⁺ to participate in the formation of SEIs/CEIs by tuning the intermolecular interactions. As a result, extremely stable and high-efficiency cycle of Li metal anodes in Li||Li cells and Li||Cu cells is achieved. The performance of Li||NCM811 cells is markedly boosted under high voltage (4.7 V) and in wide temperature range (−20 °C to 60 °C), which display stable cycling over 650 cycles and excellent rate capability up to 20 C. This work sheds new lights on F/N synergetic effect and intermolecular interactions of electrolytes for Li metal batteries.