The effects of deposition time and current density on the electrochemical performance of flexible and high-performance MnO(2)@PFG composite electrodes

A novel composite electrode has been fabricated by the direct deposition of MnO(2) onto graphene networks surrounding a paper fiber (PFG). The paper fiber between graphene sheets could be used as a flexible substrate for MnO(2) nanoparticles, and the microscopic morphologies and electrochemical performances of the MnO(2)@PFG electrodes were tuned via regulating the deposition current densities and deposition times. 3D graphene on PFG served as a highly conductive backbone with a high surface area for the deposition of the MnO(2) nanoparticles, which provided high accessibility to electrolyte ions for shortening the diffusion paths. The MnO(2)-10-600 s@PFG composite electrode achieved a maximum specific capacitance of 878.6 mF cm(−2) with an MnO(2) loading mass of 3.62 mg cm(−2) (specific capacitance of 187.7 F g(−1)) at a current density of 0.5 mA cm(−2) in a 1 M NaSO(4) aqueous solution. Additionally, the MnO(2)-10-600 s@PFG composite material with the most favorable composite ratio exhibited the highest energy density of 61.01 mW h cm(−2), maximum power density of 1249.78 mW cm(−2), excellent capacitance retention with no more than 7% capacitance loss after 10 000 cycles and good mechanical flexibility (about 91.06% of its original capacitance after 500 bending times). By combining the electric double layer capacitance of graphene networks with the pseudocapacitance of the MnO(2) nanostructures, the flexible electrode showed much enhanced electrochemical capacitance behaviors with robust tolerance to mechanical deformation; thus, it is promising for being woven into textiles for wearable electronics.