Effect of electrolyte composition on thermal stability and electrochemical performance of LiMn2O4-ySy cathodes for Li-ion batteries

Electrolytes are indispensable for the proper operation of every battery technology. Hence, in this paper, our major focus concerns identification of the most appropriate electrolyte composition in order to minimise the reactions on the electrode surface as well as enhance the electrochemical performance of Li-ion batteries containing as a cathode LiMn2O4-ySy (LMOS) spinel materials. For this purpose, thermal stability of LiPF6 and LiClO4 salts in a mixture of EC: DEC, TMS: EMC solvents towards LMOS cathode materials was investigated. All the electrolyte solutions were also tested in Li/Li+/LMOS cells. The electrochemical behaviour of electrolyte-cathode material systems was further examined by the electrochemical impedance spectroscopy. As demonstrated, LiMn2O3.99 S-0.01 (LMOS1) electrode exhibits remarkable thermal and electrochemical stability in LiPF6 solution of alkyl carbonates (EC:DEC). The satisfactory cycling performance is due to the development of highly stable passivating surface film on the LMOS1 cathode in aforementioned electrolyte that protects the active material from unfavourable reactions.