Highly Stable Metal Mono-Oxide Alloy Nanoparticles and Their Potential as Anode Materials for Li-Ion Battery

We report the synthesis of Mn x Ni1‑x O and Mn y Co1‑y O alloy nanoparticles by the thermal decomposition of the metal precursor in a surfactant. The different sized and shaped Mn x Ni1‑x O and Mn y Co1‑y O nanoparticles could be obtained by controlling precursors and surfactants. These alloy nanoparticles are antiferromagnetic and their stability is better than that of pure metal mono-oxides. On the basis of these results, we expect these alloy nanoparticles to have potential applications as electrodes in energy-generating devices such as Li-ion batteries. The higher Ni content (Mn0.19Ni0.81O) electrode exhibited a large reversible capacity (650 mAh g–1), a better initial efficiency (56%), and an improved rate and cycle performance, which was ascribed to higher electrical/electrolyte conductivity or improved surface film property. To our best knowledge, the reversible Li storage in metal oxides like MnO or NiO nanoparticles with about 10 nm diameter material itself has not been reported yet, indicative of the originality of the anode application of our materials. Also, we could expect a higher stability by addition of Mn into theconversion anode and reduction of material cost when compared with the very expensive Sn- or Mo-based oxide materials, electrolyte conductivity, or improved surface film property.