Damage Mechanism to Silicon Anode Due to Dissolved Manganese Ions from Cathode in Lithium Ion Batteries

It is still unknown how dissolved manganese ions affect the silicon anode's electrochemical performance in the lithium-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 of silicon anode during cycling, the heat flux of SEI was analyzed by DSC. Experiments shows that 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-based electrode. The galvanostatic cycle current is 300 mA/g. The half cell's Coulomb efficiency exceeds 97%, whereas the whole cell's Coulomb efficiency is only 32% after 100 cycles. 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.