Polyaniline nanopillars on surface cracked carbon fibers as an ultrahigh-performance cathode for a flexible rechargeable aqueous Zn-ion battery

Aqueous Zn-ion batteries, high safety and low costs, suffer from an inferior energy density due to a low operating voltage of aqueous electrolytes. Here we report an ultrahigh-energy cathode of polyaniline (PANI) nanopillars grown on surface cracked carbon fibers. The PANI cathode has an ultrahigh specific capacity of 412.7 mA h/g at 0.5 A/g, and a superior cyclic stability with 93.2% capacity retention over 1500 cycles at 4 A/g. The energy density, 464.1 Wh/kg @ 0.56 kW/kg, is close to that of popular lithium-ion batteries with organic electrolytes, whereas the power density, 16.6 kW/kg @ 223.5 Wh/kg, is comparable to that of supercapacitors with aqueous electrolytes. Both doping/dedoping and oxidation/reduction mechanisms are involved for ultrahigh energy storage of the PANI cathode. In addition, the Zn-ion battery can tolerate severe mechanical bending with superior capacity retention, which is promising to power wearable electronics and flexible displays.