Highly uniform Ni(HCO3)2 spheres: the morphology evolution and electrochemical performance

Abstract

Nickel bicarbonate Ni(HCO₃)₂ has recently been demonstrated to be a highly attractive electrode material for lithium-ion batteries (LIBs) and supercapacitors (SCs), and its electrochemical performance could be further enhanced through rationally tuning the morphology. Herein, Ni(HCO₃)₂ spheres are successfully prepared via a facile, one-step hydrothermal route. The effects of the hydrothermal duration on the phase and morphology are investigated. XRD patterns indicate a phase conversion from NiCO₃ into Ni(HCO₃)₂ that has never been previously reported. SEM images reveal that the reaction temperature and time play a key role in determining the phase and morphology of the resulting sample. The whole process includes, successively, nucleation, growth, self-assembly, dissolution, and recrystallization. As electrodes, the Ni(HCO₃)₂ spheres reacted for 15 h, delivering 602.4 mA h g⁻¹ after 300 cycles at 0.2 A g⁻¹ in LIBs and a specific capacitance of 450 F g⁻¹ after 5000 cycles at 5 A g⁻¹ in SCs. These results show strong potential applications in energy storage devices.