Enabling stable 4.6 V LiCoO2 cathode through oxygen charge regulation strategy

LiCoO2 is the preferred cathode material for consumer electronic products due to its high volumetric energy density. However, the unfavorable phase transition and surface oxygen release limits the practical application of LiCoO2 at a high-voltage of 4.6 V to achieve a higher energy density demanded by the market. Herein, both bulk and surface structures of LiCoO2 are stabilized at 4.6 V through oxygen charge regulation by Gd-gradient doping. The enrichment of highly electropositive Gd on LiCoO2 surface will increase the effective charge on oxygen and improve the oxygen framework stability against oxygen loss. On the other hand, Gd ions occupy the Co-sites and suppress the unfavorable phase transition and micro-crack. The modified LiCoO2 exhibits superior cycling stability with capacity retention of 90.1% over 200 cycles at 4.6 V, and also obtains a high capacity of 145.7 mAh/g at 5 C. This work shows great promise for developing high-voltage LiCoO2 at 4.6 V and the strategy could also contribute to optimizing other cathode materials with high voltage and large capacity, such as cobalt-free high-nickel and lithium-rich manganese-based cathode materials.