Investigation of the Reversible Intercalation/Deintercalation of Al into the Novel LiVO@C Microsphere Composite Cathode Material for Aluminum-Ion Batteries.

The LiVO@C microsphere composite was first reported as a novel cathode material for rechargeable aluminum-ion batteries (AIBs), which manifests the initial discharge capacity of 137 mAh g and and remains at 48 mAh g after 100 cycles with almost 100% Coulombic efficiency. The detailed intercalation mechanism of Al into the orthorhombic LiVO is investigated by ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of LiVO@C electrodes and the nuclear magnetic resonance aluminum spectroscopy (Al NMR) of ionic liquid electrolytes in different discharge/charge states. First-principle calculations are also carried out to investigate the structural change as Al inserts into the framework of LiVO. It is revealed that the Al/LiVO@C battery goes through electrochemical dissolution and deposition of metallic aluminum in the anode, as well as the insertion and deinsertion of Al cations in the cathode in the meantime. The rechargeable AIBs fabricated in this work are of low cost and high safety, which may make a step forward in the development of novel cathode materials based on the acidic ionic liquid electrolyte system.