Electrochemical properties of environment-friendly lithium-tin liquid metal battery

A Li/LiF-LiCl-LiBr/Sn battery cell is prepared for the first time to investigate the feasibility of pure tin metal as an environmentally friendly cathode material in the liquid metal battery. The Li-Sn cell can achieve the mean voltages of 0.820 and 0.607 V during charge and discharge at 100 mA cm⁻², respectively. Increasing the discharge current density from 100 to 700 mA cm⁻² results in 1.3% capacity loss, and the capacity loss is 12.4% when the charge current density increased from 100 to 1000 mA cm⁻². This high rate capability of the cell is due to ultrafast charge-transfer kinetics at the interface of liquid electrode and liquid electrolyte. The Li-Sn cell exhibits a capacity retention of 94.0% after 220 cycles. The capacity loss originates from the loss of active Sn by forming SnFe and CrSn₂ intermetallics in side reaction between the Sn and stainless steel case, and these intermetallics are inert to lithium within the voltage window of 0.5–1.2 V.