A Novel Bifunctional Self‐Stabilized Strategy Enabling 4.6 V LiCoO₂ with Excellent Long‐Term Cyclability and High‐Rate Capability

Abstract

Although the theoretical specific capacity of LiCoO₂ is as high as 274 mAh g^-1, the superior electrochemical performances of LiCoO₂ can be barely achieved due to the issues of severe structure destruction and LiCoO₂/electrolyte interface side reactions when the upper cutoff voltage exceeds 4.5 V. Here, a bifunctional self-stabilized strategy involving Al+Ti bulk codoping and gradient surface Mg doping is first proposed to synchronously enhance the high-voltage (4.6 V) performances of LiCoO₂. The comodified LiCoO₂ (CMLCO) shows an initial discharge capacity of 224.9 mAh g^-1 and 78% capacity retention after 200 cycles between 3.0 and 4.6 V. Excitingly, the CMLCO also exhibits a specific capacity of up to 142 mAh g^-1 even at 10 C. Moreover, the long-term cyclability of CMLCO/mesocarbon microbeads full cells is also enhanced significantly even at high temperature of 60 °C. The synergistic effects of this bifunctional self-stabilized strategy on structural reversibility and interfacial stability are demonstrated by investigating the phase transitions and interface characteristics of cycled LiCoO₂. This work will be a milestone breakthrough in the development of high-voltage LiCoO₂. It will also present an instructive contribution for resolving the big structural and interfacial challenges in other high-energy-density rechargeable batteries.