Long-life P-type co-doped polyaniline cathodes for ultrahigh-energy-density aqueous zinc-ion batteries

Conductive polyaniline (PANI) is considered as a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to its reversible redox properties. In this study, we prepared a binder-free PANI (βPG-PANI-6) cathode co-doped with β-naphthalene sulfonic acid (β-NSA), HClO4, and graphitic acid (GA) via a layer-by-layer self-assembled electro-polymerization method. As a soft template, β-NSA micelles can be doped with HClO4 into PANI nanoparticles to prevent the tight accumulation of PANI chains. Moreover, β-NSA and GA adsorbed on the surface of PANI nanoparticles through layer-by-layer self-assembly contain abundant weak acid groups, which can act as internal proton reservoirs to offer protons to guarantee high redox activity. During the electro-polymerization process, the flexible GA matrix which forms NO bond closely with PANI can alleviate the volume expansion effect of PANI. As a result, the βPG-PANI-6 cathode can obtain superior discharge specific capacity (560.5 mAh/g, 0.2 A/g), excellent rate performance (251.3 mAh/g, 10 A/g). It is commendable that the AZIBs assembled by βPG-PANI-6 cathode deliver ultra-high energy density and power density (535.31 Wh/kg @ 187.16 W/kg, 184.45 Wh/kg @ 7378.01 W/kg). This study expands the doping chemistry of PANI and advances the development of conducting polymer for AZIBs to a new level.