Construction of hierarchical cobalt-molybdenum selenide hollow nanospheres architectures for high performance battery-supercapacitor hybrid devices.

Transition metal selenides have aroused widespread attention as a class of emerging electrode materials for high-performance supercapacitors attributed to their featured with high theoretical capacitance and low electronegativity. Nevertheless, their practical applications are seriously restricted by the large volume expansion during high-rate charge/discharge. It is imperative to reasonably construct tunable composition and attractive architectures for electrode materials at nanoscale to mitigate the issues. Herein, hierarchical cobalt-molybdenum selenide (denoted as CoSe/MoSe-3-1) hollow nanospheres architectures are purposefully prepared via an efficient gas bubble-templated method combined with post-annealing process. Benefiting from the rationally hierarchical hollow structures and maximized utilization ratio of active materials, the novel bimetallic selenides acquire superior electrochemical performance with high specific capacity (211.97 mA h g at 1 A g) and remarkable cycling stability (94.2% capacity retention over 2000 cycles at 3 A g). Significantly, the assembled CoSe/MoSe-3-1//activated carbon (AC) battery-supercapacitor hybrid (BSH) device renders a high energy density up to 51.84 W h kg at a power density of 799.2 W kg and preeminent cycling stability with 93.4% retention over 10,000 cycles. The present work provides an effective and rational design route to engineer advanced bimetallic selenides with hierarchical hollow structures for electrochemical energy storage and conversion.