Mechanism of the carbonate-based-electrolyte degradation and its effects on the electrochemical performance of Li1+x(NiaCobMn1-a-b)1-xO2 cells

In lithium-ion batteries with carbonate electrolytes, the formation of lithium alkoxides at the anode impairs the electrochemical performance and the cycle life of the cells through destabilisation of the cathode-electrolyte interface. To fully understand the effect of electrolyte composition on the stability of the cathode-electrolyte interface, and therefore to minimise alkoxide formation and improve cycling stability, we study different carbonate solvents and mixtures thereof. Electrolytes that promote the formation of ethoxide are found to be more detrimental to the cell performance than those forming methoxide. The presence of cyclic carbonates in the electrolyte-solvent mixture alleviates the detrimental effects of ethoxide-forming solvents on the electrochemical performance of Li1.05(Ni0.33Co0.33Mn0.33)0.95O2 by reducing the solubility of the ethoxide.