An Aqueous Battery–Pseudocapacitor Hybrid Capacitor Based on Conductive Core–Shell NiCoSe₂@Co₉Se₈ Hollow Nanospheres Hybridized with Nanoscale Ru_0.41In_0.59O_y

It is always a huge challenge to explore advanced aqueous supercapacitors with both high energy and high power densities. Herein, conductive NiCoSe₂@Co₉Se₈ hollow nanospheres (HNSs) are solvothermally synthesized, where the Co₉Se₈ nanosheets uniformly surround hollow NiCoSe₂ core. The resultant NiCoSe₂@Co₉Se₈ HNSs are further exploited as a positive electrode for designing a aqueous battery–pseudocapacitor hybrid device by combining it with the high ionic/electronic conductive Ru_0.41In_0.59O_y nanoparticles as the negative electrode. Due to synergetic contributions from the two involved electrodes, the assembled Ru_0.41In_0.59O_y//NiCoSe₂@Co₉Se₈ hybrid capacitor is endowed with a wide-voltage window from 0.0 to 1.5 V, and exhibits a large specific capacitance of ≈206 F g⁻¹ at 0.5 A g⁻¹ and excellent cyclic durability with ≈10% capacitance decay after 5000 consecutive cycles, together with a high energy density of ≈50 Wh kg⁻¹ at a specific power of 3750 W kg⁻¹.