Abstract
Lithium-ion batteries are the leading rechargeable battery technology. 1 M lithium hexafluorophosphate (LiPF(6)) dissolved in carbonate solvents is commonly used as the electrolyte; however, LiPF(6) is hygroscopic and forms toxic HF in the presence of water. This work presents the synthesis of lithium bis(perfluorinated pinacolato)borate salts Li[B(pp)(2)]·xDME (x = 0 or 1, pp = perfluorinated pinacolato, O(2)C(2)(CF(3))(4)), which exhibit superior air tolerance and have higher thermal stability than LiPF(6). Lithium-ion cycling using 1 M Li[B(pp)(2)]·DME and 0.2 M Li[B(pp)(2)] electrolyte salts was performed, where 0.2 M Li[B(pp)(2)] cycled with higher capacity than 1 M Li[B(pp)(2)]·DME. X-ray photoelectron spectroscopy on the post-cycled NMC cathode found a thicker cathode electrolyte interphase with less LiF when using Li[B(pp)(2)]·DME than for LiPF(6) based electrolyte.