Tailoring pore and surface of carbonized melamine foam with graphene and RuO2 for efficient zinc-ion capacitor

Carbonized melamine foam (CMF) is a good candidate as the cathodic material for zinc-ion capacitor (ZIC) applications due to its robust mechanical property, porous structure, and high nitrogen content. However, the rich macropores and low surface area limit efficient storage of Zn2}. This work develops a mesopore-rich CMF based carbon material (CMF-G) by assembling CMF and graphene sheets. To further tailor the pore and surface of CMF-G, ZnCl2 chemical activation, air activation, and pseudocapacitive RuO2 modification are together applied to improve the energy density of CMF based ZICs. Thanks to the application of a combined strategy, the porous CMF-G@RuO2 assembled Zn//CMF-G@RuO2 ZIC devices without the binder and conductive additive deliver a high device capacitance of 170.4 F g-1 at 0.1 A g-1 and a high energy density of 60.6 Wh kg- 1, along with an exceptionally high power density of 15.2 kW kg- 1. This type ZICs also possess excellent anti-self-discharge performance with a self-discharge rate of only 8.0 mV h-1 and remarkable cycling stability with a capacitance retention of 96.7 % at 10 A g-1 after 10,000 cycles. This study demonstrates that CMF-G@RuO2 is a promising cathode material for ZICs.