Investigation of Electrolytes Utilized for High-voltage LiNi0.5Mn1.5O4 Batteries

The main challenge of high-voltage LiNi0.5Mn1.5O4 (LNMO), which is one of the most promising cathodes with the redox plateau of similar to 4.75V vs Li+ /Li, is the decomposition of electrolyte. In fact, our studies show that LNMO presents the good capacity retention ratio, higher than 80% after 300 cycles, in the electrolyte with the mixture of pure carbonate solvents. Even 92% of the initial capacity in the 300th cycle is remained in the optimal composition. Obviously, high-voltage LiNio sMni 504 can get excellent cycle performance without any special additives. In addition, we studied the electrochemical behavior of viny lene carbonate (VC) and ethylene sulfite (ES) in high potential. The results indicate that VC and ES can be electrochemically oxidized at 4.6 V and 4.05 V vs Li /Li, respectively. In the cells with the electrolytes containing VC and ES respectively, the discharge capacities are significantly diminished. Also, the thick and high-resistance sediment layers are formed on the surface of LNMO. We concluded that the SEI-forming additives widely used in commercial batteries may firstly decompose on cathode side. Therefore, the electrolyte systems should be redesigned for graphite-LNMO batteries.