An Aqueous Battery–Pseudocapacitor Hybrid Capacitor Based on Conductive Core–Shell NiCoSe 2 @Co 9 Se 8 Hollow Nanospheres Hybridized with Nanoscale Ru 0.41 In 0.59 O y

It is always a huge challenge to explore advanced aqueous supercapacitors with both high energy and high power densities. Herein, conductive NiCoSe 2 @Co 9 Se 8 hollow nanospheres (HNSs) are solvothermally synthesized, where the Co 9 Se 8 nanosheets uniformly surround hollow NiCoSe 2 core. The resultant NiCoSe 2 @Co 9 Se 8 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 0.41 In 0.59 O y nanoparticles as the negative electrode. Due to synergetic contributions from the two involved electrodes, the assembled Ru 0.41 In 0.59 O y //NiCoSe 2 @Co 9 Se 8 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 .