Revealing Rate Limitations in Nanocrystalline Li 4 Ti 5 O 12 Anodes for High‐Power Lithium Ion Batteries

Li 4 Ti 5 O 12 is a promising anode material for lithium ion batteries due to its high safety, excellent cycling stability, environmental friendliness, and low cost. Strategies of incorporation with a conductive component (such as carbon) and constructing nano‐structure are frequently adopted to improve the rate‐capability of Li 4 Ti 5 O 12 by means of enhancing the electronic conductivity and promoting the lithium ion transport within electrodes, respectively. However, which charge carrier transport process is the limiting step for Li 4 Ti 5 O 12 electrode reactions still remains unclear, and this limits the abilities to rationally design high performance Li 4 Ti 5 O 12 materials. In this work, the nanosized Li 4 Ti 5 O 12 and Li 4 Ti 5 O 12 /C materials are prepared with nearly identical particle size and morphology. The results demonstrate that the synthesized single phase Li 4 Ti 5 O 12 delivers a higher specific capacity and superior rate‐capability than Li 4 Ti 5 O 12 /C composite. As such, in contrast to a popular belief, it is lithium ion transport that restricts kinetics of the electrochemical reactions on Li 4 Ti 5 O 12 . The synthesized single phase Li 4 Ti 5 O 12 shows a specific capacity of ≈160 mAh g −1 at 0.5 C and 130 mAhg −1 at 50 C rates, respectively. This rate‐capability is the best reported for Li 4 Ti 5 O 12 anodes. The single phase Li 4 Ti 5 O 12 also demonstrated remarkable stability at high‐temperature (50 °C), showing cycling life of over 4000 cycles at 1 C.