Direct formation of porous MnO2/Ni composite foam applied for high-performance supercapacitors at mild conditions

Abstract Here, a novel three dimensional Ni foam-supported porous MnO 2 film (porous MnO 2 /Ni composite foam) was successfully synthesized by the simple hydrothermal method using Ni foam as substrate. The porous MnO 2 film had closely coated on the backbones of the Ni foam without assistant of surfactant at mild conditions. At the same time, the pore size of porous MnO 2 /Ni composite foam was easily controlled by the reaction temperature. Furthermore, it was found that the capacitive properties of porous MnO 2 /Ni composite foam were related to the pore size of MnO 2 film. It showed smaller pore size, and it exhibited better capacitive behavior for the electrode, in which the porous MnO 2 /Ni composite foam with pore size of ca.50.0∼150.0 nm showed high rate capability of 1086.0 F/g at 10.0 A/g and good cycle stability with capacitance retention of 98.0% after 500 cycles. The high capacitive properties was due to the active materials MnO 2 grown on the the backbone of the Ni foam and porous structure of MnO 2 materials, resulting in the reduce of resistance and enhancement of active surface area. Our work not only demonstrates the controlled synthesis of high-quality porous MnO 2 /Ni composite foam at mild conditions on a large scale, but also provides a universal route for the rational design of supercapacitors with high performance.