Copper tetrathiovanadate (Cu 3 VS 4 ): a newly emerging electrode for rechargeable aqueous aluminum-ion batteries.

We report the electrochemistry of Al 3+ ion storage in copper tetrathiovanadate (Cu 3 VS 4 ) in an aqueous electrolyte for the first time. It is found that Cu 3 VS 4 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 Al 3+ ion diffusion in Cu 3 VS 4 . The electrochemical mechanism of Al 3+ ion storage is also illustrated.