A study of methyl phenyl carbonate and diphenyl carbonate as electrolyte additives for high voltage LiNi0.8Mn0.1Co0.1O2/graphite pouch cells

• Diphenyl carbonate is an effective additive in LiNi0.8Mn0.1Co0.1O2/graphite cells.
• Diphenyl or methylphenyl carbonate outperforms vinylene carbonate.
• Diphenyl carbonate is very inexpensive and is widely available.

The effectiveness of methyl phenyl carbonate and diphenyl carbonate as electrolyte additives either singly or in combination with methylene methyl disulfonate and tris(-trimethyl-silyl)-phosphite has been systematically investigated in LiNi0.8Mn0.1Co0.1O2/graphite pouch cells. Experiments conducted included ultrahigh precision coulometry, electrochemical impedance spectroscopy, automated storage, gas evolution measurements as well as long-term cycling. The results showed that adding methyl phenyl or diphenyl carbonate increases the coulombic efficiency, reduces charge end-point capacity slippage rate, decreases the self-discharge rate during storage and improves the capacity retention during long-term cycling compared to cells with control electrolyte [1 M LiPF6 ethylene carbonate:ethyl methyl carbonate 3:7] or control electrolyte with 2% vinylene carbonate. 1% diphenyl carbonate appears to be the best among the systems studied. Based on these experiments, diphenyl carbonate seems to be a very beneficial additive for improving the performance of high voltage LiNi0.8Mn0.1Co0.1O2/graphite pouch cells.