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The mechanism of enhancing the capacity of the LiFePO 4 cathodes in lithium ion batteries by the addition of a small amount of vanadium, which locate on the lithium site and induce lithium vacancies in the crystal structure, is reported in this article. As a result, the capacity increases from 138 mAh/g found for pristine LiFePO 4 to 155 mAh/g for the V-added compound, and the conductivity increases from 4.75 × 10 −4 S/cm for the LiFePO 4 without V addition to 1.9 × 10 −2 S/cm for the V-added compound. A possible model to facilitate the enhancement of conductivity and capacity is described with evidence supported by X-ray powder diffraction, X-ray absorption spectroscopy, and neutron powder diffraction data.

A vertical electrophoretic deposition technique was employed to prepare polystyrene ͑PS͒ colloidal crystals with negligible crystallographic defects. The colloidal crystals were plated with Ni, followed by selective removal of PS microspheres to fabricate inverse opals. With adjustments in relevant processing parameters, we were able to obtain inverse opals in multiple layers with excellent surface uniformities. The inverse opals were used as the electrode material for water electrolysis. Results from currentpotential polarizations in 1 M KOH aqueous solution indicated that the catalytic abilities for oxygen evolution reaction ͑OER͒ and hydrogen evolution reaction ͑HER͒ increased with the layers of inverse opals. Estimation of the effective current densities determined that the entire area of the inverse opals was available for electrochemical reactions. In galvanostatic measurements for both OER and HER, the inverse opals demonstrated stable voltage profiles without notable degradations for 120 h. Compared with a planar Ni plate, the inverse opals exhibited a significantly reduced overpotential for the water electrolysis.