Understanding the low temperature electrochemistry of magnesium-lithium hybrid ion battery in all-phenyl-complex solutions

Abstract

Magnesium–lithium hybrid ion batteries have emerged as a new class of energy storage systems owing to dendrite free cycling of magnesium anode and possibility of practice of numerous conventional lithium cathodes. In present work, we used hybrid ion strategy to analyze the performance of lithium titanate based lithium cathode, magnesium metal anode, and all-phenyl complex (APC) electrolytes at different temperatures (25 °C, 10 °C, 0 °C, −10 °C, and −20 °C). The hybrid ion battery exhibited excellent rate performance (228 mAh g−1/20 mA g−1 and 163 mAh g−1/1000 mA g−1) with stable voltage plateaus at 0.90 and 0.75 V, which corresponds to specific energy of 178 Wh kg−1 at room temperature (25 °C). Experimental results revealed that APC-THF solutions have strong potential to suppress the freezing of electrolyte solutions owing to low boiling point of THF. The low temperature electrochemical testing revealed the reversible capacities of 213.4, 165.5, 143.8, 133.2 and 78.56 mAh g−1 at 25, 10, 0, −10, and −20 °C, respectively. Furthermore, ex-situ XRD, SEM, and EIS tests were carried out to understand the reaction kinetics of both Mg2+ and Li+ ions inside the lithium titanate cathode. We hope this work will shed light on low temperature prospective of electrochemical devices for use in cold environments.