Sulfur doped NiCo2O4 nanosheets as advanced cathode for flexible alkaline Zn batteries

The widespread application of nickel/cobalt-based materials for aqueous alkaline Zn batteries is hindered by the low actual discharge capacity and inferior cycling durability arising from the limited conductivity and electrochemical reaction kinetics. Herein, an effective approach is demonstrated to achieve high-efficiency and flexible cathode of alkaline Ni//Zn batteries by doping sulfur hydrothermally into NiCo2O4 (S–NCO). Compared to bare NiCo2O4, the S–NCO sample exhibits higher electric conductivity and faster kinetics. Consequently, the alkaline S–NCO//Zn battery presents a higher areal capacity (0.721 mAh cm−2 at the current density of 1 mA cm−2), long-term lifespan without capacity attenuation after 4000 cycles and satisfactory coulombic efficiency of ∼100%. Moreover, an excellent flexibility of S–NCO has been proved by the stable electrochemical performance in the charge-discharge measurements under various bending conditions.