High-rate performance zinc-ion hybrid capacitors constructed by multi-layered carbon nanosheet cathode

Zn has attracted widely attention in energy storage systems due to its characteristics of being highly safe, low-price, and environmentally friendly. Besides, the high ionic conductivity of aqueous electrolytes is beneficial for achieving high power output. Herein, the aqueous zinc-ion hybrid capacitors (ZHCs) are constructed by the multi-layered carbon nanosheets (MLCNs), Zn foil, and 1 M ZnSO4 solution as cathode, anode, and electrolyte, respectively. Of which, MLCN is prepared for the first time from a chemical by-product by a confined-tailored strategy of potassium bicarbonate. The MLCN displays well-developed mesoporous structures with high surface area of 1947.2 m(2) g(-1) and abundant cavities, which play a decisive role in enhancing charge storage and ion diffusion kinetics. As cathode for ZHC, the MLCN displays appealing Zn storage capability, such as high specific capacity of 128.7 mAh g(-1) at 0.1 A g(-1), excellent rate performance of 88.1 mA h g(-1) at 20 A g(-1), large energy/power density of 102.1 Wh kg(-1)/16.9 kW kg(-1), and outstanding cycle stability with 1.3% loss after 10,000 cycles. This work will inspire the synthesis of new carbon cathode materials from chemical by-products for Zn ion storage.