Compacting Electric Double Layer Enables Carbon Electrode with Ultrahigh Zn Ion Storage Capability

Carbon-based cathodes for aqueous zinc ion hybrid supercapacitors (ZHSCs) typically undergo low Zn ion storage capability due to their electric double layer capacitance (EDLC) energy storage mechanism that is restricted by specific surface area and thickness of electric double layer (EDL). Here, we report a universal surface charge modulation strategy to effectively enhance the capacitance of carbon materials by decreasing the thickness of EDL. Amino groups with lone pair electrons were chosen to increase the surface charge density and enhanced the interaction between carbon electrode and Zn ions, thus effectively compacting the EDL. Consequently, amino functionalized porous carbon based ZHSCs can deliver an ultrahigh capacity of 255.2 mAh g^-1 along with excellent cycling stability (95.5 % capacity retention after 50 000 cycles) in 1 M ZnCl₂ electrolyte. This study demonstrates the feasibility of EDL modified carbon as Zn²⁺ storage cathode and great prospect for constructing high performance ZHSCs.