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

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.