Facile Synthesis of Ni(OH)₂/Carbon Nanofiber Composites for Improving NiZn Battery Cycling Life

Carbon nanofibers (CNFs) were successfully functionalized by the hydrothermal treatment of wet CNFs containing concentrated HNO₃. The method of synthesis was facile and eco-friendly. With the use of oxidized CNFs as substance, Ni­(OH)₂/oxidized CNFs hybrid materials were prepared by taking a two-step solution phase reaction. The XRD pattern and TEM image suggested a well crystalline Ni­(OH)₂ nanoplate with β-phase structure growth on the surface of CNFs. Electrochemistry test results displayed high specific capacitances and long cycle life of the composites. With the use of Ni­(OH)₂/CNFs as cathode and Zn foil as anode, assembled NiZn pouch cells could achieve ∼1.75 V discharge voltage plateau, with a specific capacity ranging from 184 mAh·g^–1 at a discharging current density of 5 mA·cm^–2 to 91 mAh·g^–1 at a discharging current density of 50 mA·cm^–2. Its cycle stability was up to 1200 cycles with a capacity retention of >96% at attaining an energy density of 150 Wh·kg^–1. Compared with a 6 mol·L^–1 KOH solution electrolyte battery, the sodium polyacrylate gel electrolyte battery displayed better cycle performance. The function of the gel electrolyte was discussed. The facile method could be extended to the oxidization of the other carbon materials and synthesis of the others carbon composites