Effect of Different Electrolytes on MnO2 Anodes in Lithium-Ion Batteries

In this study, three most commonly used commercial electrolyte compositions were selected to investigate the effect of different electrolyte solvents on lithium-ion batteries (LIBs) with MnO2 anodes, including 1 M LiPF6 in EC/DEC = 1:1 (vol %), 1 M LiPF6 in EC/EMC = 1:1 (vol %), and 1 M LiPF6 in EC/DMC/DEC = 1:1:1 (vol %), where EC, DEC, EMC, and DMC represent ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate, respectively. It was found that EC/DEC exhibits the best performance with the different electrolyte solvents. Furthermore, adding 10 wt % of fluoroethylene carbonate (FEC) additive into 1 M LiPF6 in EC/DEC = 1:1 could improve reversible capacity, i.e., the increase of 2nd cycle discharge capacity from 813 mAh/g to 962 mAh/g. In addition, the FEC additive could form a polymer buffer to reduce the volume expansion of MnO2, improve the transport of Li-ion, and decrease the thickening of the SEI layer during cycling. However, it was found that the improvement of overall cycling performance from the FEC additive became less effective at longer cycling, which could be due to the rapid decomposition of FEC on the highly reactive MnO2 surface. This study provides a reference for the development of new electrolytes for MnO2 anodes and facilitates the commercialization of transition metal oxide (TMO) anodes for LIBs.