The use of Nano- Synthesis Methodology on Electrochemical Performance of limn₂o₄ Cathode at elevated Temperature

Abstract

The effects of different starting materials using nano-synthesis methodology on electrochemical performance of lithium manganese oxide (Li_xMn₂O₄) are studied. Four spinel-type Li_xMn₂O₄ (LMO) cathode materials were prepared with different lithium and manganese sources and were analyzed chemically and characterized by BET and XRD. The electrochemical performance of the cathodes at room temperature and elevated temperature was tested. The crystal structure was indexed to be a cubic system with lattice parameters of 8.2342 ±0.170 Å and defined to the space group Fd3m. There was no peak of impurity because the raw materials for Mn source were first treated with acid. Although the results showed that the structures of the samples were confirmed to be cubic spinel structure, the lattice parameter and specific surface area of the samples were different. The LiMn₂O₄ cathodes have an initial discharge capacity of over 120mAh/g and show an ordinary two-step voltage profile. The results demonstrated that the cathode materials prepared with LiNO₃ as Li source have larger lattice parameters, than those prepared from LiOH·H₂O as Li source. The cathode prepared from Electrochemical Manganese Dioxide (EMD) as Mn source have larger particle sizes, lower first charge and discharge capacity, better cyclic performance, whereas those from Chemical Manganese Dioxide (CMD) as Mn source have smaller particle size, higher first charge and discharge capacity, and poor cyclic stability at elevated temperature. The cell polarization of the cathode developed by LiOH•H₂O and EMD was identified to be the least and the elevated temperature cycelability to be the best. These manifestations can be attributed to differences in Li and Mn sources, specific surface areas, purities of starting materials and synthesis conditions. Melt-impregnation as a nano-synthesis method proved to be an excellent method to synthesize LiMn₂O₄ cathode materials that can operate at elevated temperatures when using correct starting materials and good control of synthesis temperatures.