Understanding the Impact of Fe-Doping on the Structure and Battery Performance of a Co-Free Li-Rich Layered Cathodes

Abstract

A series of Co-free Li-rich layered oxides, Li1.24Mn0.62-xNi0.14FexO2 (x=0, 0.01, 0.02 and 0.03) has been synthetized by a self-combustion reaction. Fe doping affects either lattice structure and bonding as shown by the changes in the size of unit cell calculated from diffraction patterns and in the vibrational frequencies observed in Raman spectra. The electrochemical performance has been evaluated in a lithium cell by galvanostatic cycling: Doped samples show better capacity retention and minor decreases in the specific capacity (i. e., Li1.24Mn0.60Ni0.14Fe0.02O2 can supply a specific capacity of 235 mAhg−1 with 94 % of capacity retention after 150 cycles). These positive effects originated by alterations in the point defectivity (Ni3+ concentration, anionic and cationic vacancies), changes in the transport properties, as showed by Cyclic Voltammetry; as well as an improved structural resilience compared to the un-doped material in postmortem analyses.