Spray drying construction of hierarchical hollow ZnMn2O4 folded microspheres as anode materials for lithium ion batteries

Abstract

ZnMn₂O₄ (ZMO) has been paid close attention by researchers because of its high capacity of lithium storage, abundant reserves on earth, environmental friendliness and simple preparation process. However, as with most transition metal oxides, the low conductivity and the structural collapse caused by volume expansion limit the commercial application of ZMO. Herein, ZMO hollow folded microspheres (ZMO-HFs) are prepared by a spray-drying method. After annealing, ZMO-HFs with single and/or double shells are formed. The mixed shells not only increase the effective contact area between the electrolyte and active substance, but also shorten the Li⁺ diffusion path and increase the active sites for the electrochemical reaction. In addition, the special structure can effectively alleviate the bulk expansion of the material to improve the cyclic rate performance of the material. Thanks to these attractive structural advantages, the obtained ZMO-HFs exhibit excellent rate behavior (∼460 mA h g⁻¹ at 2 A g⁻¹) and ultra-long cycle performance (∼724 mA h g⁻¹ after more than 400 cycles at 2 A g⁻¹). More importantly, this simple yet high-yield method will provide meaningful guidance for smart design/synthesis of other hollow materials.