A bi-functional lithium difluoro(oxalato)borate additive for lithium cobalt oxide/lithium nickel manganese cobalt oxide cathodes and silicon/graphite anodes in lithium-ion batteries at elevated temperatures

Abstract Lithium difluoro(oxalato)borate (LiFOB) is investigated as an additive for enhancing the electrochemical performance of high-voltage lithium cobalt oxide (LiCoO 2 , LCO)/lithium nickel manganese cobalt oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 , NMC) cathodes and high-capacity silicon/graphite (Si-C) anodes. LCO-NMC/Si-C full cells with a LiFOB additive have been found to exhibit improved high temperature electrochemical performance. To confirm the effects of LiFOB on the cathode and the anode, the surface chemistry of the anodes and cathodes cycled in electrolytes with and without the LiFOB additive are examined using ex-situ X-ray photoelectron spectroscopy (XPS). The LiFOB additive produces a LiF-based solid electrolyte interphase (SEI) on the Si-C anode and a carboxylate-based SEI on the LCO-NMC cathode.