Comparison of the electrochemical properties of LiBOB and LiPF6 in electrolytes for LiMn2O4/Li cells

The electrochemical stability and conductivity of LiPF6 and lithium bis(oxalato)borate (LiBOB) in a ternary mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were compared. The discharge capacities of LiMn2O4/Li cells with the two electrolytes were measured at various current densities. At room temperature, LiMn2O4/Li cells with the electrolyte containing LiBOB cycled equally well with those using the electrolyte containing LiPF6 when the discharge current rate was under 1 C. At 60 °C, the LiBOB-based electrolyte cycled better than the LiPF6-based electrolyte even when the discharge current rate was above 1 C. Compared with the electrolyte containing LiPF6, in LiMn2O4/Li cells the electrolyte containing LiBOB exhibited better capacity utilization and capacity retention at both room temperature and 60 °C. The scanning electron microscopy (SEM) images and the a.c. impedance measurements demonstrated that the electrode in the electrolyte containing LiBOB was more stable. In summary, LiBOB offered obvious advantages in LiMn2O4/Li cells.