A new CaCO3-template method to synthesize nanoporous manganese oxide hollow structures and their transformation to high-performance LiMn2O4 cathodes for lithium-ion batteries

This paper presents a new CaCO3-template synthesis of highly nanoporous manganese oxide hollow structures and their transformation to high-performance LiMn2O4 cathodes for lithium-ion batteries via the facile coprecipitation of Mn–Ca-carbonates and temperature-controlled decomposition of MnCO3 and CaCO3, followed by the selective removal of the carbonates by washing with HCl. The as-prepared Mn2O3 nanostructures showed very high specific surface area with their subunit particle size of <30 nm, as compared with conventional processes with subunits of >100 nm. The transformation to uniformly porous LiMn2O4 hollow structures was successfully achieved by the facile impregnation of LiOH into the porous Mn2O3 hollow precursors, followed by a conventional solid-state reaction. The LiMn2O4 hollow structures deliver a discharge capacity of about 120 mA h g−1 at a 1 C rate and 115 mA h g−1 at a 10 C rate with excellent cycling stability. The capacity retention approached 94% after up to 800 cycles of charging–discharging at a 10 C rate.