Lithium carbonate as an electrolyte additive for enhancing the high-temperature performance of lithium manganese oxide spinel cathode

• The addition of Li2CO3 to the electrolyte can suppress the contents of HF in the electrolyte.
• The low self-discharge rate of the LiMn2O4 cells with Li2CO3 is lower than that of no additive.
• The LiMn2O4 cells with Li2CO3 exhibit better rate capability and excellent cycle stability than that without Li2CO3.
• A stable film can be formed on the LiMn2O4 cathode using containing-Li2CO3 electrolyte.

The effect of lithium carbonate (Li2CO3) as an additive on the stability of the electrolyte and cycling performance of lithium manganese oxide spinel (LiMn2O4) batteries at elevated temperature was studied. The addition of Li2CO3 to the electrolyte can suppress the capacity fading of LiMn2O4 batteries. The linear sweep voltammetry (LSV) and the cyclic voltammetry (CV) indicate that Li2CO3 has a lower oxidation potential in the mixed solvents of ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), participating in the formation process of the stable cathode electrolyte interface (CEI) film. In addition, the results of electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrate that the stable CEI film of the cells with Li2CO3 can be formed, which can effectively reduce the dissolution of Mn2+ from LiMn2O4 into the electrolyte at elevated temperature. It is concluded that the addition of Li2CO3 to a solution of 1 M LiPF6–EC/EMC/DEC = 1/1/1 (weight ratio) may decrease solvent decomposition and change the structure of the passivation film on the LiMn2O4 cathode.