Iridium Doping Boosting the Electrochemical Performance of Lithium-Rich Cathodes for Li-Ion Batteries

Li2MnO3, as one traditional member of lithium-rich layered cathodes, gives batteries with large specific capacity. However, it suffers from unexpected severe capacity fading and discharge voltage decay upon cycling. Iridium doping obviously pronounces the electrochemical performance, that is, storage capacity and cycling life. Iridium successfully occupies in the transition-metal (TM) layer of Li2MnO3 through one facile solid-solution method at 650-1050 degrees C. Both dopant concentration and calcination temperature have large influence on the performance due to the intrinsic microstructure and crystallization. The Li-2(Ir0.1Mn0.9)O-3-850 degrees C cathode exhibits an initial capacity of 192 mA h.g(-1), with 68.8% capacity retention after 50 cycles. The introduction of iridium in the TM sites obviously reduces electrochemical impedance and alleviates the voltage decay in cycles. The performance improvement can be attributed to the structure stability induced by partial conversion from Mn3+ to Mn4+ ions of TM valence in iridium-doping cathodes. This work unveils a microstructure-optimized mechanism of Li2MnO3 cathodes, which is beneficial for designing high-capacity layered cathode materials for high-voltage lithium-ion batteries.