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

An efficient and scalable method to improve the capacitive properties of MnO2 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/MnOx (rGO/MnOx) composite without oxygen vacancies-induced phase transformation is formed. RGO/MnOx 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 10A g(-1)). The performance improvement of rGO/MnOx 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/MnOx//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/MnOx sample offers a promising approach to broaden MnO2 -based electrode materials for a new-generation energy storage device.