3D graphene-like oxygen and sulfur-doped porous carbon nanosheets with multilevel ion channels for high-performance aqueous Zn-ion storage

Zinc-ion hybrid capacitors (ZIHC) demonstrate impressive charge-storage performance and intrinsic safety due to the inherited superiorities of aqueous rechargeable batteries and supercapacitors. However, the promotion of electrochemical performance is usually hindered by the cathode materials that fail to hold high energy density and rate capability of ZIHC. The optimization of porous carbon cathodes into a hierarchical structure is an efficient strategy to break the bottlenecks of ZIHC. Herein, a metal oxide space-confined strategy is proposed to build 3D graphene-like porous carbon nanosheets (3DPC) with doping of O and S heteroatoms by using low-cost aromatic hydrocarbons as precursors. It is found that the obtained 3DPC consists of micro-, mseo- and macropores and further delivers a high specific surface area of 2813 m2 g−1 with a total pore volume of 1.82 cm3 g−1. Specifically, such a well-defined hierarchical porosity of 3DPC coupled with rich O and S heteroatoms enables sufficient multilevel ion transport channels and large accessible surface sites to capture the Zn2+ ions. As a proof of concept demonstration, the assembled aqueous ZIHC by employing the 3DPC cathode exhibits a desirable capacity of 194 mAh g−1 at 0.5 A g−1 with a superior rate capability of 53% at 30 A g−1 and excellent cycling stability of over 88% after 15000 cycles. Moreover, the remarkable electrochemical performance of the 3DPC cathode can be well-preserved in the case of a quasi-solid-state ZIHC device under various harsh bent states, highlighting the promising application in flexible and wearable energy storage.