Importance of Cooling Speed on Rapid Synthesis of LiNi_0.5Mn_1.5O₄ by a Solution Combustion Synthesis Method

摘要

Cooling speed is a significant factor for LiNi0.5Mn1.5O4 synthesized by solution combustion synthesismethod. In order to investigate the influence of cooling speed on LiNi0.5Mn1.5O4 spinels, in this paper,LiNi0.5Mn1.5O4 spinels have been synthesized by an improved solution combustion synthesis method at800 C for 10min with different cooling speed. X-ray diffraction (XRD), Fourier transform infraredpectroscopy (FTIR) and scanning electron microscope (SEM) have been used to investigate the phasecomposition and micro-morphologies of the products. Charge-discharge measurements, cyclicvoltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been used to study theelectrochemical performance of the products. The results indicate that the fast cooled LiNi0.5Mn1.5O4(FC-LNMO) is single phase and possesses highly disordered phase structure and large amounts of3+ Mn ions. Contrastively, the slowly cooled product (SC-LNMO) is a combination of two phases, themain phase of LiNi0.5Mn1.5O4 and the minor phase of LixNi1-xO impurity. SC-LNMO has more ordered3+ phase structure and possesses little amounts of Mn ions. Although the reversible capacity of FC- LNMO is smaller than that of SC-LNMO, the cycle stability and rate capability of FC-LNMO are3+ much better than these of SC-LNMO, due to the larger amounts of Mn , lower polarization andsmaller charge transfer resistance of FC-LNMO than these of SC-LNMO.