Electrochemical Energy Storage

Using a novel characterization technique combining in situ X-ray diffraction and chemical sodiation to study the Li₄Ti₅O₁₂ as new anode material for Sodium-ion batteries

A novel characterization technique using the combination of chemical sodiation and synchrotron based in situ X-ray diffraction (XRD) has been developed. The power of this new technique was demonstrated in elucidating the structure evolution of Li₄Ti₅O₁₂ upon sodium insertion. The sodium insertion behavior in Li₄Ti₅O₁₂ is strongly size dependent. A solid solution reaction behavior in a wide range has been revealed during sodium insertion into the nano-sized Li₄Ti₅O₁₂ (~44 nm), which is quite different from the well-known two-phase reaction of Li₄Ti₅O₁₂/Li₇Ti₅O₁₂ system during lithium insertion, and also has not been fully addressed in the literature so far. Based on this in situ experiment, the apparent Na⁺ ion diffusion coefficient (D_Na+) of Li₄Ti₅O₁₂ was estimated in the magnitude of 10^-16 cm² s^-1, close to the values estimated by electrochemical method, but 5 order of magnitudes smaller than the Li⁺ ion diffusion coefficient (D_Li+~10^-11 cm² s^-1), indicating a sluggish Na⁺ ion diffusion kinetic in Li₄Ti₅O₁₂ comparing with that of Li⁺ ion. Therefore, preparing the Li₄Ti₅O₁₂ cathode with nano-sized particles is critical to make it a suitable anode material for sodium-ion batteries. The application of this new in situ chemical sodiation method developed by our group provides a facile way and a new opportunity for in situ structure investigations of various sodium-ion battery materials and other systems.

“A size-dependent sodium storage mechanism in Li4Ti5O12 investigated by a novel characterization technique combining in situ X-ray diffraction and chemical sodiation,” X. Yu, H.L. Pan, W. Wan, C. Ma, J. Bai, Q.P. Meng, S.N. Ehrlich, Y.S. Hu, X.-Q. Yang, Nano Lett. (2013), 13, 4721.