Laser-induced manganese oxide/graphene composite electrodes with commercial-level mass loading towards high-performance supercapacitors

Combining of graphene with pseudocapacitance metal oxide is effective to construct supercapacitor electrode with high energy storage capacity. However, balancing the contradiction between high load of metal oxide and high stability of electrode is still challenging. Herein, a novel supercapacitor electrode composed of 3D graphene and manganese oxide is in-situ fabricated by laser carbonization of polyimide (PI) foam loaded with manganese acetate precursor. Due to the rich porous structure and super hygroscopicity of PI foam, high content manganese acetate is uniformly loaded into the network of PI foam. Under laser irradiation, PI foam is carbonized to form 3D porous graphene, while the generation of MnO-Mn3O4 and its uniform loading on graphene is achieved synchronously. The obtained composite electrode exhibits a commercial-level mass loading up to 8 mg cm-2, with a 48.6% weight ratio of MnO-Mn3O4. As a result, an ultra-high specific capacitance of 1525 mF cm-2 can be obtained for the composite electrode at the optimal doping concentration of 0.3 mol L- 1. Notably, the composite electrode also exhibits excellent cycling stability of 94.75% retention rate after 6000 cycles. The maximum area specific capacitance of the micro supercapacitor with PVA/LiCl gel electrolyte is 410.19 mF cm-2, the maximum energy density and power density are 82.04 mu Wh cm-2 and 400 mu W cm-2, respectively.