An Enhanced Li3AlH6 Anode Prepared by a Solid-State Ion Exchange Method for Use in a Solid-State Lithium-Ion Battery

Li3AlH6 is an anode material with an enormous potential to enhance the energy density of secondary lithium-ion batteries that is limited by severe irreversibility and instability. In this study, a high-performance Li3AlH6 anode is synthesized via a solid-state ion exchange reaction between a LiBH4 electrolyte and Na3AlH6. This reaction not only forms a tight contact between Li3AlH6 and LiBH4 but also introduces a NaBH4/LiBH4 electrolyte layer with excellent Li+ conductivity around Li3AlH6. The as-synthesized Li3AlH6 anode exhibits a first discharge capacity of 1722 mAh.g(-1) and a capacity loss of only 15% in the first charge. After 150 cycles under a current density of 1 A.g(-1), the Li3AlH6 anode retains a capacity of 990 mAh.g(-1) with nearly 100% coulombic efficiency. An anomalous increase in the capacity during cycling is analyzed and attributed to effects from Al electrochemical milling on the active material.