Electrochemical Properties of Lithium Based Liquid Metal Battery with Tin-Bismuth Cathode Materials

Reliance on diesel fuel in military operations is a weak point due to the challenge of transporting fuel through hostile regions. To reduce fuel consumption and emissions, military microgrids are now considered as a solution to address its needs for improved energy security and reliability of military bases. Particularly, in military microgrids, stationary energy storage system plays a critical role in guaranteeing the microgrids stability and reliability. Recently, research into liquid metal battery has been ramped up for applications in smart grid energy storage system due to the inherent advantages of long cycle life, simple fabrication process, and low cost of materials. D. J. Bradwell et al. have initially proposed magnesium-antimony (Mg‖Sb) liquid metal battery which exhibits 97%, 71%, and 69% of Coulombic, voltage, and energy efficiencies, respectively. However, Mg‖Sb chemistry is not consistent enough for practical use in smart grid energy storage system due to the high operating temperature of 700°C and low discharge voltage of ca. 0.21 V. To overcome such problems efficiently, lithium metal has recently attracted attention as alternative anode material because of its low melting point (181°C), low electronegativity, and the lowest solubility in molten salts. X. Ning et al. have reported lithium-bismuth (Li‖Bi) liquid metal battery operating at a temperature of 550°C. K. Wang et al. have reported lithium-antimony-lead (Li‖Sb-Pb) operating at a temperature of 450°C. However, lead can leave behind serious environmental and human health problems. In this study, we adopted eutectic tin-bismuth (Sn-Bi) alloy as cathode material because it is widely used for lead-free solder material in electronics due to its low melting point of 139°C. We have investigated the electrochemical properties (Coulombic, voltage, and energy efficiencies) of pure tin and bismuth as well as eutectic tin-bismuth alloy to evaluate the effect of adding bismuth into tin. After charging and discharging of lithium-tin-bismuth (Li‖Sn-Bi) liquid metal battery, microstructural analysis using scanning electron microscope and X-ray computational tomography was also carried out to investigate alloying/de-alloying reactions of lithium into tin and bismuth.