Graphene wrapped TiO2@MoSe2 nano-microspheres with sandwich structure for high-performance sodium-ion hybrid capacitor

Sodium-ion hybrid capacitors (SIHCs) have received extensive attention and research due to their combined advantages of high power performance and high energy density. However, the lack of high-performance anode materials has been a challenge for sodium storage devices. Herein, a heteroatom co-doped hollow spherical TiO2@MoSe2/reduced graphene oxide (RGO) with pea pods structure is designed and synthesized. This unique composite is made of TiO2 as the stable framework, MoSe2 sheet as the main active materials, and RGO conductive network as the protective cover. The sandwich structure provides stable and ordered transport channels for electrons and Na+, and greatly increases the number of active sites. As a result, TiO2@MoSe2/RGO exhibits satisfactory electrochemical performance. At a high current density of 2 A g-1, TiO2@MoSe2/RGO still maintains a capacity of 106 mAh g-1 after 1000 cycles. The hybrid device possesses an energy density of 135 Wh kg−1 at power density of 1667 W kg−1, demonstrating the design concept of heterogeneous composite provides a new route for the development of electrode materials in sodium-ion storage devices.