Electrochemical performances of 0.9Li₂MnO₃–0.1Li(Mn₀.₃₇₅Ni₀.₃₇₅Co0.₂₅)O₂ cathodes: Role of the cycling induced layered to spinel phase transformation
By Ghanty, C.; Basu, R.N. & Majumder, S.B.
Published in Solid State Ionics
2014
Abstract
In the present work, we have reported that as compared to Li₂MnO₃ lean compositions, the electrochemical properties of Li₂MnO₃ rich integrated cathodes (viz. 0.9Li₂MnO₃–0.1Li(Mn₀.₃₇₅Ni₀.₃₇₅Co0.₂₅)O₂ ) are singular in three different ways. First, unlike its Li₂MnO₃ lean counterparts, the oxygen and concomitant lithium extraction in Li₂MnO₃ rich composition (viz. Li(Li₀.₃₁Mn₀.₆₄₆Ni₀.₀₂₆Co₀.₀₁₇)O₂) continues beyond first charging cycle. Second, for Li₂MnO₃ rich compositions, layered to spinel phase transformation seems to be unavoidable with repeated charge–discharge cycling. Formation of spinel phase triggers capacity fading in these cathodes. We have found that for these cathodes, galvanostatic cycling at relatively higher rate (> 20 mA g⁻¹) retards the spinel formation with concomitant improvement of capacity retention with cycling. Finally, forLi₂MnO₃ rich integrated cathodes the major capacity contribution is found to be due to the reversible manganese redox (~ 3 V and ~ 2.6 V). Therefore, the energy densities of these cathodes are less as compared to Li₂MnO₃ lean compositions.