Abstract
Li2MnO3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li2MnO3, Li1.5Al0.17MnO3, Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 were synthesized by a sol-gel Pechini method. All the samples were characterized with XRD, Raman, XPS, SEM, Tap density and BET analyzer. XRD patterns indicated the presence of monoclinic phase for pristine Li2MnO3 and mixed monoclinic/spinel phases (Li2-xMn1-yAlx+yO3+z) for Al-substituted Li2MnO3 compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. XPS analysis for Mn 2p orbital reveal a significant decrease in binding energy for Li1.0Al0.33MnO3 and Li0.5Al0.5MnO3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g-1 for Li2MnO3, 68mAh g-1 for Li1.5Al0.17MnO3, 58 mAh g-1 for Li1.0Al0.33MnO3 and 74 mAh g-1 for Li0.5Al0.5MnO3 were obtained. Aluminum substitutions increased the discharge capacity and the spinel phase.
