Boosting Zn-Ion Energy Storage Capability of Hierarchically Porous Carbon by Promoting Chemical Adsorption.

The construction of advanced Zn-ion hybrid supercapacitors (ZHSCs) with high energy density is promising but still challenging, especially at high current densities. In this work, a high-energy and ultrastable aqueous ZHSC is demonstrated by introducing N dopants into a hierarchically porous carbon cathode for the purpose of enhancing its chemical adsorption of Zn ions. Experimental results and theoretical simulations reveal that N doping not only significantly facilitates the chemical adsorption process of Zn ions, but also greatly increases its conductivity, surface wettability, and active sites. Consequently, the as-fabricated aqueous ZHSC based on this N-doped porous carbon cathode displays an exceptionally high energy density of 107.3 Wh kg-1 at a high current density of 4.2 A g-1 , a superb power density of 24.9 kW kg-1 , and an ultralong-term lifespan (99.7% retention after 20 000 cycles), substantially superior to state-of-the-art ZHSCs. Particularly, such a cathode also leads to a quasi-solid-state device with satisfactory energy storage performance, delivering a remarkable energy density of 91.8 Wh kg-1 . The boosted energy storage strategy by tuning the chemical adsorption capability is also applicable to other carbon materials.