3D hierarchical Ni(PO3)2 nanosheet arrays with superior electrochemical capacitance behavior

Abstract

A novel electrode material, three-dimensional (3D) hierarchical Ni(PO₃)₂ nanosheet arrays, is explored via a rational topotactic strategy combining hydrothermal growth with subsequent phosphorylation treatment. The as-synthesized Ni(PO₃)₂ nanosheet arrays self-supported on activated carbon cloth (Ni(PO₃)₂@ACC) exhibit superior electrochemical capacitive behaviors to a Ni(OH)₂ analogue with similar structural characteristics. The areal and mass specific capacitances of the arrays are as high as 4.43 F cm⁻² at a current density of 2 mA cm⁻² and 2237 F g⁻¹ at ∼1 A g⁻¹, respectively, which is comparable to the best reported results for Ni-based and Me-PO_x battery-type electrodes. Furthermore, even at a high rate of 10 mA cm⁻², the arrays maintain ∼90% charge retention after 2000 cycles, suggesting their robust stability and their very promising applications for energy storage.