UC Berkeley

Vehicle electrification is a critical application of lithium-ion batteries (LIBs), and it is essential to develop LIBs that can operate at sub-ambient temperatures with satisfying performance. Conventional LIBs have performance deficits at low temperatures which hinder their use in extreme environments. One approach to address this problem is to rationally engineer the electrode/electrolyte interface with electrolyte additives to improve the electrochemical kinetics at sub-ambient temperatures. In this work, silicic acid (SiAc) is incorporated into standard LIB electrolyte as an additive to enhance the capacity and energy density of LIBs at temperatures down to −20 °C. Full-cell impedance analysis and X-ray photoelectron spectroscopy of cycled electrodes point towards an additive-induced change in surface chemistry which alters the charge transfer process. It is proposed that the SiAc additive participated in the formation of solid electrolyte interphase (SEI) and lowered the activation energy of the interface impedance, assisting lithium ion transport across the interface at lower temperatures.