Assembling metal oxide nanocrystals into dense, hollow, porous nanoparticles for lithium-ion and lithium–oxygen battery application

Abstract

New dense hollow porous (DHP) metal oxide nanoparticles that are smaller than 100 nm and composed of Co₃O₄, FeO_x, NiO and MnO_x were prepared by densely assembling metal oxide nanocrystals based on the hard-template method using a carbon colloid as a sacrificial core. These nanoparticles are quite different from the traditional particles as their hollow interior originates from the stacking of nanocrystals rather than a spherical shell. The DHP nanoparticles preserve the intriguing properties of nanocrystals and possess desirable surface area and pore volume that enhance the active surface, which ultimately benefits applications such as lithium-ion batteries. The DHP Co₃O₄ nanoparticles demonstrated an enhanced capacity of 1168 mA h g⁻¹ at 100 mA g⁻¹vs. 590 mA h g⁻¹ of powders and stable cycling performance greater than 250 cycles when used as an anode material. Most importantly, the electrochemical performance of DHP Co₃O₄ nanoparticles in a lithium–O₂ battery was also investigated for the first time. A low charge potential of ∼4.0 V, a high discharge voltage near 2.74 V and a long cycle ability greater than 100 cycles at a delivered capacity of 2000 mA h g⁻¹ (current density, 200 mA g⁻¹) were observed. The performances were considerably improved compared to recent results of mesoporous Co₃O₄, Co₃O₄ nanoparticles and a composite of Co₃O₄/RGO and Co₃O₄/Pd. Therefore, it would be promising to investigate such properties of DHP nanoparticles or other hollow metal (oxide) particles for the popular lithium–air battery.