A high-performance Cu–Al dual-ion battery realized by high-concentration Cl− electrolyte and CuS cathode

We propose a new Cu–Al dual-ion battery that aqueous solution composed of LiCl, CuCl and AlCl3 (LiCuAl) is used as the electrolyte, CuS is used as the cathode of aqueous aluminum ion battery for the first time and copper foil is used as the anode. The assembled Cu–Al dual-ion battery yields a reversible capacity of 538 mA h/g at 200 mA/g, and exhibits longterm cycling stability of over 200 cycles with 88.6% capacity retention at 1000 mA/g. Above excellent performance is inseparable from the three components of LiCuAl electrolyte and electrode materials. The Al-storage mechanism of CuS is proposed that the S–S bond in CuS lattice interacts with aluminum ions during the aluminum storage process. In addition, the charging and discharging process does not cause irreversible damage to the S–S bond, thus Cu–Al dual-ion battery with CuS as cathode shows great cycle stability.