表面钒离子掺杂的锂⑦过剩层状正极材料的可逆氧氧化还原反应( Promoting the Reversible Oxygen Redox Reaction of Li〦xcess Layered Cathode Materials with Surface Vanadium Cation Doping )

Y Lee J Shin H Kang D Lee T Kim Y Kwon EA Cho cation doping density functional theory calculation Li〆xcess cathode lithium﹊on batteries oxygen redox reaction

Li〆xcess layered cathode (LLC) materials have a high theoretical specific capacity of 250 mAh g induced by transition metal (cationic) and oxygen (anionic) redox activity. Especially, the oxygen redox reaction related to the activation of the Li2MnO3 domain plays the crucial role of providing a high specific capacity. However, it also induces an irreversible oxygen release and accelerates the layered‐to﹕pinel phase transformation and capacity fading. Here, it is shown that surface doping of vanadium (V) cations into LLC material suppresses both the irreversible oxygen release and undesirable phase transformation, resulting in the improvement of capacity retention. The Vヾoped LLC shows a high discharge capacity of 244.3 ± 0.8 mAh g with 92% retention after 100 cycles, whereas LLC delivers 233.6 ± 1.1 mAh g with 74% retention. Furthermore, the average discharge voltage of Vヾoped LLC drops by only 0.33 V after 100 cycles, while LLC exhibits 0.43 V of average discharge voltage drop. Experimental and theoretical investigations indicate that doped Vヾoping increase the transition metal–oxygen (TMO) covalency and affect the oxidation state of peroxo﹍ike (O2) species during the delithiation process. The role of Vヾoping to make the oxygen redox reversible in LLC materials for high〆nergy density Li﹊on batteries is illustrated here.

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