Copper tetrathiovanadate (Cu₃VS₄): a newly emerging electrode for rechargeable aqueous aluminum-ion batteries

We report the electrochemistry of Al³⁺ ion storage in copper tetrathiovanadate (Cu₃VS₄) in an aqueous electrolyte for the first time. It is found that Cu₃VS₄ could deliver an initial discharge capacity of 111 mA h g^-1 at a current rate of 0.5 A g^-1 and 77 mA h g^-1 up to the 300^th cycle at 2 A g^-1 along with an excellent rate capability. The better electrochemical performance may be attributed to the high theoretical capacity of sulfur and the superior conductivity of copper which allows facile Al³⁺ ion diffusion in Cu₃VS₄. The electrochemical mechanism of Al³⁺ ion storage is also illustrated.