Revealing the key role of non-solvating diluents for fast-charging and low temperature Li-ion batteries

Abstract

Fast-charging and low temperature operation are of vital importance for the further development of lithium-ion batteries (LIBs), which is hindered by the utilization of conventional carbonate-based electrolytes due to their slow kinetics, narrow operating temperature and voltage range. Herein, an acetonitrile (AN)-based localized high-concentration electrolyte (LHCE) is proposed to retain liquid state and high ionic conductivity at ultra-low temperatures while possessing high oxidation stability. We originally reveal the excellent thermal shielding effect of non-solvating diluent to prevent the aggregation of Li+ solvates as temperature drops, maintaining the merits of fast Li+ transport and facile desolvation as at room temperature, which bestows the graphite electrode with remarkable low temperature performance (264 mA h g−1 at −20 °C). Remarkably, an extremely high capacity retention of 97% is achieved for high-voltage high-energy graphite||NCM batteries after 250 cycles at −20 °C, and a high capacity of 110 mA h g−1 (71% of its room-temperature capacity) is retained at −30 °C. The study unveils the key role of the non-solvating diluents and provides instructive guidance in designing electrolytes towards fast-charging and low temperature LIBs.