A Novel Bifunctional Self-Stabilized Strategy Enabling 4.6 V LiCoO with Excellent Long-Term Cyclability and High-Rate Capability.

Although the theoretical specific capacity of LiCoO is as high as 274 mAh g, the superior electrochemical performances of LiCoO can be barely achieved due to the issues of severe structure destruction and LiCoO/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 LiCoO. The comodified LiCoO (CMLCO) shows an initial discharge capacity of 224.9 mAh g 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 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 LiCoO. This work will be a milestone breakthrough in the development of high-voltage LiCoO. It will also present an instructive contribution for resolving the big structural and interfacial challenges in other high-energy-density rechargeable batteries.