The Effect of Al and Fe Substitution on the Structure and the Electrochemical Properties of NMC Type Positive Electrode Materials for Lithium Ion Batteries
The current study discusses three NMC type materials obtained by cationic substitution of cobalt with aluminum and/or iron in the starting material LiNi0.6Mn0.2Co0.2O2. The three compounds with the following compositions LiNi0.6Mn0.2Co0.15Al0.5O2 (NMCA), LiNi0.6Mn0.2Co0.15Fe0.5O2 (NMCF) and LiNi0.6Mn0.2Co0.15Al0.025Fe0.025O2 (NMCAF) were synthesized by the self-combustion method using sucrose as fuel. These materials belong to α-NaFeO2-type structure (space group R-3m) with hexagonal ordering. Rietveld refinement analysis of the XRD patterns revealed a very low cationic mixing for the double substituted material NMCAF (5%) compared to the non-substituted material (13%) suggesting a higher structural stabilization for the double substituted compound. Galvanostatic cycling measurements indicate improved electrochemical performance, good cycling stability and higher reversible capacity preferentially for NMCAF (190 mAh.g-1), NMCF (167 mAh.g-1), NMCA (145 mAh.g-1) then NMC (140 mAh.g-1).
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