Fundamental Triangular Interaction of Electron Trajectory Deviation and P-N Junction to Promote Redox Reactions for the High-Energy-Density Electrode.

Highly efficient redox reaction of active electrode materials is the guarantee for achieving high energy density for energy storage devices. Here, we design a triangle of the electrode material involving the P-N junction between NiO (p-type) and MoO3 (n-type) and electron trajectory deviation between gold nanoparticles with NiO or MoO3. This optimized fundamental triangle structure could facilitate the redox reaction of a metal oxide, and thus the fabricated ternary nanocomposites exhibit excellent electrochemical performance. At a lower current density (0.5 A g-1), the mass specific capacitance of a single electrode can reach 943.3 F g-1, while the NiO/MoO3 tested under the same conditions only has a specific capacitance of 278.9 F g-1. The assembled asymmetric device with activated carbon shows a higher capacitance retention rate of 98.7% after long-term cycling under different current densities, and a maximum energy density of 28.9 W h kg-1 (power density of 400.1 W kg-1). The crucial prerequisite of this strategy is the lower work function of gold nanoparticles compared with active materials, which significantly reduce the activation energy of NiO/MoO3 and the formed P-N junction between p-type NiO with n-type MoO3 in their contact interfaces. This novel design of a triangle structure could be expected to be applied in other materials to develop a kind of energy storage device with excellent electrochemical performance.