Facile Li⁺ Transport in NMC811||Graphite Lithium-Ion Batteries at Low Temperatures Enabled by Using Low-Polarity Solvents

Li-ion batteries (LIBs) using graphite anode and high voltage nickel-rich cathodes (LiNi_xCo_yMn_zO₂(x+y+z=1)) are the most promising energy storage technology in the foreseeable future. However, charging these LIBs at low temperatures (≤ -20 °C) remains challenging because the excessive resistances encountered by lithium-ion in and across the bulk electrolytes and the interphases induce lithium plating on graphite anodes and electrolytes decomposition on the cathodes, which accelerate the capacity decay of the batteries. In particular, the significant increase of the charge-transfer resistance is the most problematic one and has barely been studied and well-regulated. Herein, we introduce a strategy of using low-polarity-solvents electrolytes that can reduce the resistance and activation energy in the charge transfer process effectively, allowing facile lithium-ion transport at subzero temperatures. The exemplary electrolyte enables the LiNi_0.8Mn_0.1Co_0.1O₂ ||graphite (NMC811||Gr) LIBs to deliver 81% of its room-temperature capacity at 1/3C at -20 °C and keep 84% and 78% of its room-temperature capacity at -30 °C and -40 °C, respectively, while maintaining decent energy density, fast-charging capability, and stability at room temperature and high temperature of 50 °C. The effective electrolyte engineering approach demonstrated in this work together with molecular simulations provides new insight and a general guideline for designing practical low-temperature electrolytes for LIBs.