Fabrication of Nanoporous Ni by Chemical Dealloying Al from Ni-Al Alloys for Lithium-ion Batteries

Nanoporous nickel (np-Ni) was fabricated through dealloying of Ni-Al alloys and its application in lithium-ion batteries (LIBs) was assessed. The effect of alloy composition of the Ni-Al alloys on the formation of np-Ni has been investigated using X-ray diffraction (XRD), scanning electron microscopy combined with energy dispersive X-ray spectrometry (SEM-EDX), and 3D profilometry analysis. The experimental results show that the Ni-Al alloy composition has a significant effect on the dealloying feasibility, the phase constituents and the microstructures of the resultant np-Ni. As compared to Ni50Al50 alloy, Ni30Al70 was easier for dealloying since the percentage of Ni content is higher in Ni50Al50. SEM images revealed that the np-Ni exhibited approximately a mean inner diameter of 71.10 ± 43.69 nm and 40.84 ± 24.70 nm for the Ni30Al70 and Ni50Al50 alloy, respectively. Pore distribution analysis revealed that due to the multiple intermetallic phases in the precursor Ni-Al alloys, the nanoporous structure was heterogeneous with a large variation in pore size and porosity. 3D profilometry revealed that almost all of the surfaces of the as-formed np-Ni displayed a leptokurtoic distribution. In addition, the surface area, pore volume, and mean pore diameter of the np-Ni were assessed using Brunauer-Emmett-Teller (BET) analysis. The specific surface area of the np-Ni dealloyed from Ni30Al70 alloy was as high as 198.70 m2 g-1 compared to 9.46 m2 g-1 for dealloyed from Ni50Al50 alloy. The as-dealloyed np-Ni was used as negative electrode of LIBs and the performance was evaluated. The dealloyed np-Ni from Ni30Al70 alloy with an oxide (NiO) layer surface and highly conductive Ni metal cores exhibited maximum discharge capacity of 651 mA h g-1 at 1C rate after 9th cycle, which is reduced to a neglectable level of 80 mA h g-1 after 150th cycles.