Controllable synthesis of spinel nano-ZnMn₂O₄via a single source precursor route and its high capacity retention as anode material for lithium ion batteries

Agglomerated pure spinel ZnMn₂O₄ nanoparticles with flake-shaped structure have been synthesized via calcination of an agglomerated Zn-Mn citrate complex precursor, which was prepared with high yield by a convenient, environmentally benign and low temperature route. The composition, morphology and thermal decomposition of the Zn-Mn citrate complex were studied by C&H elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The resulting ZnMn₂O ₄ nanoparticles obtained from the precursor calcination at 700 °C were systematically characterized by XRD, FTIR, N₂ Adsorption/Desorption, SEM, TEM, HRTEM and selected area electron diffraction (SAED). The results show that the ZnMn₂O₄ material was agglomerated to form a porous texture in pure phase. The electrochemical properties of the agglomerated ZnMn₂O₄ material were investigated to determine its reversible capacity, rate and cycling performance as the anode material for lithium ion batteries (LIBs). This ZnMn ₂O₄ material exhibited promising capacity retention of over 200 cycles at varying discharge rates. The electrode also exhibited attractive rate capabilities yielding capacity of 330 mAh g^-1 after more than 35 cycles at 600 mA g^-1.The ameliorated electrochemical performance can be ascribed to the high crystallinity and porous texture of the ZnMn₂O₄ material which provided short diffusion paths for lithium ions. Ex situ XRD analysis of the electrodes after discharging and charging to the selected voltage was conducted and the possible lithium insertion mechanisms are discussed. This study suggests that the ZnMn ₂O₄ material synthesized via the single source precursor route is a promising anode material for LIBs. © The Royal Society of Chemistry 2011.