Crystallization of Multi-Phase Ni, Co-Hydroxide with Improved Supercapacitor Performance

摘要

In this study, crystallization of Ni, Co-hydroxide HT-Ni_(0.6)Co_(0.4)(OH)_2 with multiple crystal phase compositions was realized on the basis of crystal phase evolution from α-Ni(OH)_2 to β-Ni(OH)_2. A mixed-phase hydrothermal precursor Ni_(0.6)Co_(0.4)(OH)_2 containing α-Ni(OH)_2 and α-Co(OH)_2 components was first prepared by a facile chemical precipitation method, and was hydrothermally treated at 170℃ for 15 h. During the hydrothermal processing, the α-Ni(OH)_2 component gradually evolved into β-Ni(OH)_2 that the newly formed β-Ni(OH)_2, the untransformed α-Ni(OH)_2, in connection with the original α-Co(OH)_2 composed a novel multi-phase hydroxide. The electrochemical measurements manifested the hydrothermally derived multi-phase HT-Ni_(0.6)Co_(0.4)(OH)_2 electrode material displayed better capacitive performance than the employed Ni_(0.6)Co_(0.4)(OH)_2 precursor, which can deliver high supercapacitance (～558 Fg~(-1)) at large charge/discharge current (～40 Ag~(-1)) and exhibited improved rate performance (62% capacitance retention from 15 to 40 Ag~(-1)). An asymmetric HT-Ni_(0.6)Co_(0.4)(OH)_2/AC aqueous supercapacitor was designed, high power density (～1.6 kW kg~(-1)) and high energy density (～22 Wh kg~(-1)) were attained by this prototype device.