Synchronous embedded growth of Mo 2 C nanodisk arrays immobilized on porous carbon nanosheets for ultra-stable sodium storage.

Sodium ion capacitors (SICs) that combine the merits of both rechargeable batteries and supercapacitors have gained widespread recognition for their high energy density and extended cycle life as new energy storage devices. However, the purposeful design of advanced battery-type anodes has become an urgent need to remedy the dynamics mismatch with the capacitive cathode. Herein, we propose a simple but efficient bottom-up approach to build three-dimensional Mo 2 C/C hybrid architectures in situ as anodes for SICs. By finely regulating the ratio of carbon and molybdenum sources, the optimized Mo 2 C/C, where even thinner subunit assembled Mo 2 C nanodisk (∼47.1 nm in thickness) arrays are immobilized on carbon nanosheet substrate via the synchronous embedded growth, rapid electron and ion diffusion/transport expressways, abundant active sites and robust structural stability were achieved for efficient sodium storage. Benefiting from the synergistic contributions of the components, the optimum Mo 2 C/C anode displays an outstanding rate and long-cycle properties as a competitive anode. Moreover, the constructed Mo 2 C/C-based SICs exhibited an energy density of ∼16.7 W h kg -1 at 10 kW h kg -1 , along with ∼22.5% capacitance degradation over 4000 cycles at 1 A g -1 . This contribution will guide the precise synthesis of other versatile Mo 2 C-based hybrids towards energy-related applications and beyond.