Molten Salt-Assisted Construction of Hollow Carbon Spheres with Outer-Order and Inner-Disorder Heterostructure for Ultra-Stable Potassium Ion Storage.

The central goal of high-performance potassium ion storage is to control the function of the anode material via rational structural design. Herein, N- and S-doped hollow carbon spheres with outer-short-range-order and inner-disorder structures are constructed to achieve highly efficient and ultra-stable potassium ion storage using a low-temperature molten salt system. The ultrathin carbon walls and uniform mesoporous as well as unique heterostructure synergistically realize significant potassium storage performance via facilitating rapid diffusion of potassium ions and alleviating substantial volume expansion. Furthermore, as the anode of a potassium ion battery, the as-prepared MSTC electrode demonstrates a state-of-the-art cycling capability of 221.3 mAh g at 1 A g after 20,000 cycles. The assembled potassium ion hybrid capacitor device demonstrates a high energy of 157 Wh kg at 956 W kg and excellent reversibility at a current density of 5.0 A g after 20,000 cycles with 82.7% capacity retention. Accordingly, our work provides new ideas for designing advanced carbon anode materials and understanding the charge storage mechanism in potassium ion battery, as well as constructing high energy-power density potassium-ion hybrid capacitors (PIHCs).