Fabrication of core–shell porous nanocubic Mn2O3@TiO2 as a high-performance anode for lithium ion batteries

Abstract

A novel composite, porous cubic Mn₂O₃@TiO₂, was fabricated via a simple and cost-effective approach and characterized in terms of structure and performance as an anode for lithium ion batteries. The porous Mn₂O₃ cubes were developed by calcining cubic MnCO₃ particles without using any template and then coated with TiO₂ from heat decomposition of tetrabutyl titanate. The characterization from FESEM, TEM, HRTEM, XPS, BET, and XRD indicates that the as-fabricated Mn₂O₃@TiO₂ takes a hierarchically porous cubic morphology with an edge of ∼340 nm and a core–shell structure with porous cubic Mn₂O₃ as the core, which consists of nanoparticles of ∼30 nm, and a layer of porous single-crystalline spinel TiO₂ as the shell, which consists of smaller nanoparticles of ∼5 nm. The charge–discharge tests demonstrate that this unique configuration endows the as-fabricated Mn₂O₃@TiO₂ with superior charge–discharge performance, to be specific, a rate capacity of 263 mA h g⁻¹ at 6000 mA g⁻¹ compared to the 9.7 mA h g⁻¹ of Mn₂O₃, and a cyclic capacity of 936 mA h g⁻¹ after 100 cycles at 200 mA g⁻¹ compared to the 443 mA h g⁻¹ of Mn₂O₃. The nanosized particles of Mn₂O₃ and TiO₂ and the hierarchically porous structure among them provide paths for lithium-ion diffusion and sites for lithium-ion intercalation/deintercalation, while the chemically and mechanically stable TiO₂ ensures the structural stability of Mn₂O₃ cubes, yielding excellent rate capability and cyclic stability of the as-fabricated Mn₂O₃@TiO₂ as an anode for lithium ion batteries.