Tailoring NiO Nanostructured Arrays by Sulfate Anions for Sodium‐Ion Batteries

In this contribution, a novel sulfate‐ion‐controlled synthesis is developed to fabricate freestanding nickel hydroxide nanoarrays on Ni substrate. As an inorganic morphology‐controlled agent, SO42− ions play a critical role in controlling the crystal growth and the nanoarray morphologies, by modulating the growth rate of adsorbed crystal facets or inserting into the metal hydroxide interlayers. By controlling the SO42− concentration, the nanostructured arrays are tailored from one‐dimensional (1D) Ni(SO4)0.3(OH)1.4 nanobelt arrays to hierarchical β‐Ni(OH)2 nanosheet arrays. With further graphene oxide modification and postheat treatment, the obtained NiO/graphene hybrid nanoarrays show great potential for high‐performance sodium‐ion batteries, which exhibit a cyclability of 380 mAh g−1 after undergoing 100 cycles at 0.5 C and reach a rate capability of 335 mA h g−1 at 10 C. Sulfate anions as inorganic morphology‐controlled agents show green advantages over the organic ones, and play critical roles in controlling the crystal growth and the morphologies. The morphology‐controlled effect of SO42− ions is found to tailor the nanostructured arrays from one‐dimensional (1D) Ni(SO4)0.3(OH)1.4 nanobelt arrays to hierarchical β‐Ni(OH)2 nanosheet arrays. The obtained NiO/graphene hybrid nanoarrays show great potential for high‐performance sodium‐ion batteries.