Mesoporous carbon-supported manganese tungstate nanostructures for the development of zinc–air battery powered long lifespan asymmetric supercapacitor†
Synthesis of cotton fabric-derived mesoporous carbon supported MnWO4 nanostructures for the fabrication of asymmetric supercapacitors with ultra-long lifespan and rechargeable zinc–air batteries (ZABs) is demonstrated. The asymmetric supercapacitor device is fabricated using a binder-free positive electrode made of MnWO4 nanostructures and mesoporous carbon cloth (MnWO4/CC) derived from cotton fabric. The asymmetric device delivers an areal capacitance of 281.33 mF cm−2 at a current density of 0.4 mA cm−2 and has an ultra-long cycling stability of >50 000 cycles with a 2% increase in the areal capacitance. The potential cycling-induced K+ intercalation, transformation of MnWO4 to KxW3O9 and the in situ generation of MnOOH boost the capacitive performance and afford ultra-long lifespan. A rechargeable ZAB with a cell voltage of 1.506 V, peak power density of 131.4 mW cm−2 at a current density of 232.4 mA cm−2 and very good cycling stability is fabricated using the air cathode made of mesoporous carbon supported MnWO4(MnWO4/C). The as-fabricated coin cell ZAB successfully powers the MnWO4/CC-based asymmetric supercapacitor without an external electrical input. The ZAB powered asymmetric supercapacitor lights up 29 red LEDs. Bifunctional energy conversion and storage performance of MnWO4 is demonstrated for the first time.