Elucidating the Effect of Iron Doping on the Electrochemical Performance of Cobalt-Free Lithium-Rich Layered Cathode Materials

The eco-friendly and low-cost Co-free Li1.2Mn0.585Ni0.185Fe0.03O2 is investigated as a positive material for Li-ion batteries. The electrochemical performance of the 3 at% Fe-doped material exhibits an optimal performance with a capacity and voltage retention of 70 and 95%, respectively, after 200 cycles at 1C. The effect of iron doping on the electrochemical properties of lithium-rich layered materials is investigated by means of in situ X-ray diffraction spectroscopy and galvanostatic intermittent titration technique during the first charge–discharge cycle while high-resolution transmission electron microscopy is used to follow the structural and chemical change of the electrode material upon long-term cycling. By means of these characterizations it is concluded that iron doping is a suitable approach for replacing cobalt while mitigating the voltage and capacity degradation of lithium-rich layered materials. Finally, complete lithium-ion cells employing Li1.2Mn0.585Ni0.185Fe0.03O2 and graphite show a specific energy of 361 Wh kg−1 at 0.1C rate and very stable performance upon cycling, retaining more than 80% of their initial capacity after 200 cycles at 1C rate. These results highlight the bright prospects of this material to meet the high energy density requirements for electric vehicles.