Facile Synthesis of Ni Nanofoam for Applications in Energy Storage Devices
Metal foams are utilized in various applications, such as in the automotive industries and electrochemical devices. Herein, the Ni nanofoam (NF) is synthesized by a facile method for applications in energy storage devices, including Li-air cathodes, Li-ion anodes, and supercapacitors. Self-aligned or randomly linked Ni wires are produced with or without magnetic field, respectively. The surface area of Ni wires is increased by oxalic acid etching at 80oC with 5–30 wt% water, leading to Ni oxalate nanosheets, nanowires or nanoleaves. Metallic Ni are obtained by reducing Ni oxalate with H2 at 350oC in 10 min.
Ni nanofoam is utilized as a novel current collector in Li-ion anode. C-coated Si nanoparticles on Ni NF (C-Si NP/Ni NF) show 38% rate enhancement in comparison to C-Si NP/Cu foil. Higher stability of C-Si NP/Ni NF with a capacity retention of 91% is reached vs. 73% for C-Si NP/Cu foil over 180 cycles.
Regarding NiO anode, NiO-decorated Ni nanowires derived from Ni wire backbone is directly synthesized on commercially available Ni foam. Excellent stability with capacity 680 mAh g-1 at 0.5C (1C = 718 mA g-1) is achieved for 1000 cycles.
Amorphous RuO2 nanoflakes deposited on Ni nanofoam (RuO2/Ni NF) is utilized in Li-O2 battery. Stability of the RuO2/Ni NF cathode is shown with ~87.7% capacity retention after 75 cycles. Capacity as high as 6537.8 mAh g-1 based on RuO2 weight can be reached at 0.02 mA cm-2 with low charge potential 3.78 V leading to high voltaic efficiency 70.11%.
RuO2/Ni NF is utilized in symmetric supercapacitors. Highest specific capacitance 678.6 F g-1 can be achieved with energy density 60.3 Wh kg-1. The template-less and self-assembled Ni NF synthesis requires only low temperature and eco-friendly chemicals, and can be simply dip-coated with RuO2 nanoparticles. All of these render the Ni nanofoam readily adapted into mass manufacturing without efforts.