Unveiling the influences of electrolyte additives on the fast-charging performance of lithium-ion batteries

Abstract

Enhancing the fast-charging capability of lithium-ion batteries is a promising way to extend the driving range of electric vehicles. One of the most effective and economic ways is to regulate the electrode-electrolyte interphase chemistry by employing electrolyte additives. This requires a comprehensive understanding of the intrinsic role and effectiveness of different electrolyte additives. In this work, five common electrolyte additives are comprehensively compared in graphite | LiNi_0.8Mn_0.1Co_0.1O₂ lithium-ion cells, including lithium difluorophosphate (PFO), lithium bis(oxalato)borate (LiBOB), lithium difluoro (oxalato)borate (DFOB), tris(trimethylsilyl) phosphite (TMSPi), and tris(trimethylsilyl) phosphate (TMSPA). Although all of them are found to improve fast-charging performance over the baseline electrolyte, comprehensive analyses show that DFOB and TMSPi are the most effective additives, which results from their capability of ameliorating the electrode-electrolyte interphases at both the cathode and anode. This is confirmed with X-ray photoelectron spectroscopy and comprehensive electrochemical characterizations. In contrast, LiBOB and PFO can stabilize the cathode well, but make the anode-electrolyte interphase more resistive. Overall, this research expands the understanding of the role of electrolyte additives in fast-charging lithium-ion batteries.