Mesoporous carbon-supported manganese tungstate nanostructures for the development of zinc–air battery powered long lifespan asymmetric supercapacitor

Abstract

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 K_xW₃O₉ 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.