Oxygen vacancies modulation in graphene/MnOx composite for high performance supercapacitors

An efficient and scalable method to improve the capacitive properties of MnO 2 is reported by inducing graphene (rGO) and oxygen vacancies via a thermal treatment in air, in which graphene oxide (GO) is in situ reduced and graphene/MnO x (rGO/MnO x ) composite without oxygen vacancies-induced phase transformation is formed. RGO/MnO x composite exhibits a large specific capacitance (274 F g −1 at 0.5 A g −1 ), excellent cycling stability (98.8% after 5000 cycles at 1 A g −1 ) and rate performance (171 F g −1 at 10 A g −1 ). The performance improvement of rGO/MnO x sample is mainly attributed to the moderate concentration of oxygen vacancies, rGO and special 3D porous architecture, which facilitate the rapid ionic and electronic transport and promote a facile redox reaction and surface double-layer capacitance. The asymmetric supercapacitor composed of rGO/MnO x //Kochen Black (KB) also shows an outstanding cyclic stability (89% after 5000 cycles) in all-solid-state asymmetric supercapacitor. The design and synthesis method of rGO/MnO x sample offers a promising approach to broaden MnO 2 -based electrode materials for a new-generation energy storage device.