Modification of the Solution Flameless Combustion Synthesis of Spinel LiMn2O4 by Nitric Acid

Abstract

In present work, the effect of auxiliary oxidant HNO₃ with different amounts on structures and properties of spinel LiMn₂O₄ using lithium nitrite and manganese acetate as raw materials by means of the solution flameless combustion synthesis method has been studied. The phase composition, microscopic morphology and electrochemical properties of the LiMn₂O₄ were investigated using XRD, SEM and charge-discharge cycling, respectively. The results showed that the main phase of productions obtained was the LiMn₂O₄ and the impurity phase was greatly affect by the amount of HNO₃, for instances, a Mn₃O₄ impurity phase was detected at low HNO₃ amount (below 1.0 for the NO₃^–/CH₃COO^– molar ratio), while a Mn₂O₃ phase was observed at high HNO₃ amount (above 1.0 for the NO₃^–/CH₃COO^– molar ratio). From their XRD patterns, it can be seen that the diffraction peaks became sharper, with the increasing concentration of HNO₃, indicating that the crystalline of LiMn₂O₄ was forming and their particle size decreased gradually. After adding proper HNO₃ into raw compounds, the LiMn₂O₄ nano-particles were the most uniform. Compared with the direct productions, the nitric acid modified productions possessed bigger capacity and better capacity retention rate. The discharge capacity of the product increased first and then decreased with increasing concentration of nitric acid.