Bifunctional Interphase Promotes Li+ De-Solvation and Transportation Enabling Fast-Charging Graphite Anode at Low Temperature.

ABSTRACT

The most successful lithium-ion batteries (LIBs) based on ethylene carbonate electrolytes and graphite anodes still suffer from severe energy and power loss at temperatures below -20 °C, which is because of high viscosity or even solidification of electrolytes, sluggish de-solvation of Li+ at the electrode surface, and slow Li+ transportation in solid electrolyte interphase (SEI). Here, a coherent lithium phosphide (Li3P) coating firmly bonding to the graphite surface to effectively address these challenges is engineered. The dense, continuous, and robust Li3P interphase with high ionic conductivity enhances Li+ transportation across the SEI. Plus, it promotes Li+ de-solvation through an electron transfer mechanism, which simultaneously accelerates the charge transport kinetics and stands against the co-intercalation of low-melting-point solvent molecules, such as propylene carbonate (PC), 1,3-dioxolane, and 1,2-dimethoxyethane. Consequently, an unprecedented combination of high-capacity retention and fast-charging ability for LIBs at low temperatures is achieved. In full-cells encompassing the Li3P-coated graphite anode and PC electrolytes, an impressive 70% of their room-temperature capacity is attained at -20 °C with a 4 C charging rate and a 65% capacity retention is achieved at -40 °C with a 0.05 C charging rate. This research pioneers a transformative trajectory in fortifying LIB performance in cryogenic environments.