Three-dimensional coral-like Ni2P-ACC nanostructure as binder-free electrode for greatly improved supercapacitor

The function and performance of supercapacitors are determined by materials. However, their rational design is of paramount importance as well. In this paper, we report on a three-dimensional coral-like Ni2P-ACC nanostructure as binder-free electrode for greatly improved supercapacitor. This strategy is aimed first at forming a unique structure for lager redox-active sites and better spatial utilization, and second at producing greater conductivity and a hydrophilic high-polarized surface, which enhances the migration rate of ions between the electrolyte and the exposed surface. When Ni2P-ACC is employed as a positive electrode, it exhibits high areal capacity (2438 mF cm−2 or 3352 F g−1), and super-long cycle life (99% and 97.7% charge retentions after 5000 and 10,000 cycles, respectively). In addition, the ASC device with Ni2P-ACC and activated carbon electrodes also shows high areal capacity and long-term stability (88.8% retention of specific capacitance for 10,000 cycles). These results indicate that coral-like Ni2P-ACC nanostructure can be expected to become the candidate for supercapacitor electrodes in energy conversion.