Li3AlH6 is an anode material with an enormous potential to enhance the energy density of secondarylithium-ion batteries that is limited by severe irreversibility and instability. In this study, a highperformance Li3AlH6 anode is synthesized via a solid-state ion exchange reaction between a LiBH4electrolyte and Na3AlH6. This reaction not only forms a tight contact between Li3AlH6 and LiBH4 butalso introduces a NaBH4/LiBH4 electrolyte layer with excellent Li+conductivity around Li3AlH6. Theas-synthesized Li3AlH6 anode exhibits a first discharge capacity of 1722 mAh·g-1and a capacity loss ofonly 15% in the first charge. After 150 cycles under a current density of 1 A·g-1, the Li3AlH6 anoderetains a capacity of 990 mAh·g-1 with nearly 100% coulombic efficiency. An anomalous increase in thecapacity during cycling is analyzed and attributed to effects from Al electrochemical milling on theactive material..
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