Sulfolane-Based Electrolyte for High Voltage Li(Ni0.42Mn0.42Co0.16)O2 (NMC442)/Graphite Pouch Cells

Abstract

Ethylene carbonate (EC)-free electrolyte composed of sulfolane (SL), ethylmethyl carbonate (EMC) and vinylene carbonate (VC) was studied in Li(Ni0.42Mn0.42Co0.16)O2 (NMC442)/graphite pouch cells using in situ measurements of gas evolution, ultra high precision coulometry (UHPC), automated storage experiments, long-term cycling and electrochemical impedance spectroscopy (EIS). Although cells using 1 M LiPF6 in SL:EMC 3:7 (w:w) do not function at all, the addition of only 1% VC allows the cells to operate normally. In situ gas measurements show that NMC442/Graphite pouch cells containing SL:EMC:VC electrolyte produce less gas during formation than cells containing control (1 M LiPF6 EC:EMC 3:7 (w:w)) electrolyte or 2% VC in control electrolyte. Cycling and storage experiments show that cells containing SL:EMC:VC electrolytes can provide better performance than control electrolyte without additives and similar performance to state-of-the-art electrolyte with the ternary additive blend 2% prop-1-ene-1,3-sultone (PES) +1% methylene methanedisulfonate (MMDS) +1% tris(trimethylsilyl) phosphite (TTSPi) (“PES-211”) in EC:EMC 3:7 (w:w). The SL:EMC:VC system needs to be further explored with additional additives and from a safety perspective.