Promoting Surface Electric Conductivity for High-Rate LiCoO 2 .

The cathode materials work as the host framework for both Li + diffusion and electron transport in Li-ion batteries. The Li + diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock-salt phase was coherently constructed at the surface of LiCoO 2 , promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (V eff ) imposed in the bulk, thus driving more Li + extraction/insertion and making LiCoO 2 exhibit superior rate capability (154 mAh g -1 at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high-rate cathode materials by tuning the surface electron transport property.