Iridium\nDoping Boosting the Electrochemical Performance\nof Lithium-Rich Cathodes for Li-Ion Batteries

Abstract

Li₂MnO₃, as one traditional member of lithium-rich\nlayered cathodes, gives batteries with large specific capacity. However,\nit suffers from unexpected severe capacity fading and discharge voltage\ndecay upon cycling. Iridium doping obviously pronounces the electrochemical\nperformance, that is, storage capacity and cycling life. Iridium successfully\noccupies in the transition-metal (TM) layer of Li₂MnO₃ through one facile solid–solution method at 650–1050\n°C. Both dopant concentration and calcination temperature have\nlarge influence on the performance due to the intrinsic microstructure\nand crystallization. The Li₂(Ir_0.1Mn_0.9)­O₃-850°C cathode exhibits an initial capacity of\n192 mA h·g^–1, with 68.8% capacity retention\nafter 50 cycles. The introduction of iridium in the TM sites obviously\nreduces electrochemical impedance and alleviates the voltage decay\nin cycles. The performance improvement can be attributed to the structure\nstability induced by partial conversion from Mn³⁺ to Mn⁴⁺ ions of TM valence in iridium-doping cathodes. This work\nunveils a microstructure-optimized mechanism of Li₂MnO₃ cathodes, which is beneficial for designing high-capacity\nlayered cathode materials for high-voltage lithium-ion batteries.