Enhanced cycling stability in 4.6 V LiCoO2 for high energy density lithium-ion batteries through Al and Y co-doping

For the first time, this work investigates the synergetic impact of yttrium (Y) and aluminium (Al) co-doping on the electrochemical properties of 4.6 V LiCoO2 (LCO) cathode for high energy density lithium-ion batteries. The optimized LCO demonstrates an impressive initial discharge capacity of 208.6 mAh g−1 in the voltage range of 3-4.6 V, along with superior structural stability, retaining over 86% of its initial capacity even after 125 cycles at the current of 100 mA g−1 that is far higher than the capacity retention of 40% for the pristine LCO under the same condition. Thanks to the synergistic effect, Al in Co layers enhances the bonds of Al/Co-O to stabilize oxygen in the LCO crystal structure while Y serves "pillar" in Li layers, migrated from the initial Co layers during cycling process, effectively curtail the formation and expansion of interlayer cracking, which contributes to the long-term cycle stability of LCO under high voltage. Most importantly, Al/Y co-doping is a facile process compatible with the existing industrial infrastructure for LCO mass production, and thus it can be scaled up readily for commercial applications. Al/Y co-doped LCO is assembled into commercial-level pouch cells with graphite anode, achieves an extremely high energy density of 750 Wh/L, and exhibits a superior cycling stability and obtains a capacity retention of 88.2% at 25 °C after 800 cycles with the high cutoff voltage of 4.55 V.