Improved Cycling Performance of Intermetallic Anode by Minimized SEI Layer Formation

Abstract

Electrochemical properties of bismuth composite electrode are investigated as potential negative electrode for lithium ion batteries. The electrode shows severe capacity decay typically observed in the case of alloy-based materials, using a conventional carbonate-based electrolyte solution. The electrode maintained only 10% of the theoretical capacity after 25 cycles of lithiation/delithiation process. The electrode shows poor coulombic efficiency of < 90% during the initial 15 cycles. On the other hand, the bismuth composite electrode shows excellent cycling performance in the 2M LiBH4 in THF solution. The electrode maintained >98% of reversible capacity, even after 50 cycles. The bismuth electrode cycled in the LiBH4 electrolyte maintained relatively large bismuth particles compared with the electrode cycled in the carbonate-based electrolyte. In situ FTIR study proved the carbonate-based electrolyte forms passivation layer <0.7 V vs. Li, while the LiBH4 electrolyte does not passivate the electrode surface.