Hierarchical One-Dimensional Ammonium Nickel Phosphate Microrods for High-Performance Pseudocapacitors

High-performance electrochemical capacitors will drive the next-generation portable, flexible and wearable electronics. Unlike the conventional all-carbon supercapacitors (electric double layer capacitors, EDLC) with high power but poor energy density, pseudocapacitors capitalize the high energy density inherent to reversible redox reactions and provide a facile means to enhancing the energy ratings of supercapacitors. The high length-to-diameter ratio and anisotropic character of 1-D architecture makes them suitable for use in energy storage. For the first time, we report 1-D microrod structures (similar to 36 nm width) of ammonium nickel phosphate hydrate (ANP(mr)) as a pseudocapacitor with high energy rating and power handling. To confirm the data, the ANP(mr)-based pseudocapacitor was subjected to various configurations (i.e., half-cell, symmetric, asymmetric, and flexible all-solid-state) and in each case it gave excellent values compared to any accessible literature to date. We clearly demonstrate that a flexible all-solid-state ANP(mr)-based pseudocapacitor achieved high areal capacitance of 66 mF cm(-2) with extra-ordinary energy (21.2 mWh cm(-2)) and power (12.7 mW cm(-2)) densities. This work opens doors for a facile, robust and scalable preparation strategy for low-cost, earth-abundant electrode materials for high-performance pseudocapacitors.