Single-crystal and hierarchical VSe2 as an aluminum-ion battery cathode

Aluminum-ion batteries (AIBs) with high safety, low cost and abundant resources have been regarded as a promising candidate for relieving the partial resource shortage of Li-ion batteries. However, the absence of an appropriate cathode material with a high capacity and good cycling properties makes it hard to apply them for electronic devices. In this work, a new aluminum-ion battery is assembled with a hierarchical vanadium diselenide (VSe2) cathode based on an ionic liquid electrolyte 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl)/AlCl3. Brick-like VSe2 can be successfully synthesized through a facile hydrothermal method. As the cathode of AIBs, VSe2 delivers two obvious discharge voltage plateaus of similar to 1.2 V and similar to 0.6 V vs. Al/AlCl4-. The initial specific discharge capacity is as high as 650 mA h g(-1) at a current density of 100 mA g(-1), and the reversible capacity is about 50 mA h g(-1) with a coulombic efficiency of about 94% after 100 cycles. Moreover, the energy storage mechanism of VSe2 in aluminum-ion batteries is confirmed.