摘要
It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.
It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.
基金
supported by the National Natural Science Foundation of China (Nos. 51501085, 11704019, 51522212 and 51421002)
National Program on Key Basic Research Project (2014CB921002)
the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB07030200)
