Functional additives assisted ester-carbonate electrolyte enables wide temperature operation of a high-voltage (5 V-Class) Li-ion battery

Nowadays, wide temperature range and high-energy Li-ion batteries are increasingly required. However, it is difficult to get a compromise between subzero temperature performance and high temperature performance. Herein, methyl acetate co-solvent with a freezing point of -98.1 degrees C (50% by volume) is blended with carbonates to obtain a high-conductivity LiPF6-based electrolyte, which contains tris(trimethylsilyl) phosphite and 1,3-propanediolcyclic sulfate binary functional additives to significantly enhance cycling performance of a challenging high-voltage (5 V-class) battery system using a LiNi0.5Mn1.5O4 cathode and a graphitic mesocarbon microbead anode, unprecedentedly ranging from -60 degrees C to 50 degrees C. High reactivity between methyl acetate co-solvent and graphitic mesocarbon microbead anode is innovatively proposed to be associated with graphitic mesocarbon microbead anode catalytic formation of methoxy free radical. More importantly, high reactivity between methyl acetate co-solvent and graphitic mesocarbon microbead anode can be greatly suppressed by species derived from functional additives. This paper highlights the crucial rule of both high Li+ conductivity and favorable graphite anode interface layer for achieving high performance wide temperature range Li-ion batteries.