Effect of Mn(Ⅱ) from cathode on silicon anode in lithium-ion batteries (LIBs)

Abstract

It is still unknown how dissolved manganese ions affect the silicon anode's electrochemical performance in thelithium-ion batteries (LIBs). In this study, the damage mechanism of Mn²⁺ to silicon electrode in LIBs was studied by adding Mn²⁺ into electrolyte system to simulate the electrochemical environment. Through the comparison between full cell and half cell, the mechanism of the capacity fading of silicon electrode is revealed. In order to compare the amount of SEI growth on silicon anode during the cycling, the heat flux of SEi was analyzed by DSC. Experiments show that the Mn²⁺ could make SEI more fragile, more easily break, and then accelerate the SEI thickening. So Mn²⁺ could reduce the coulomb efficiency and electrochemical capacity of the silicon anode. Electrochemical capacity of negative electrode in full cell decays much faster than that in half-cell environment, whose coulomb efficiency of full cell is only 32%, while that of the half cell is higher than 97%. In addition to the damage of the Mn²⁺ to silicon anode, the depletion of active lithium ion source in full cell is also an important reason for the rapid decline of electrochemical capacity.