Fig. 3.

a CV curves at different scan rates, b GCD curves at different current densities, and c Ragone plots of the aqueous ZHC. Energy densities of other aqueous ZHCs and Zn-ion batteries reported in literatures are provided for comparison. d Schematic of the 3D porous structure of kelp-carbon and the ion sieving effect for carbon nanosheets in electrochemical process. e Cycling performance of the device at 2 A g⁻¹