Revealing the lithium migration paths in Li4+xTi5O12 by neutron diffraction

Abstract

For lithium-ion battery materials, lithium migration is one of the key parameters that determine performance. Neutron powder diffraction is considered to be one of the best approaches to reveal the lithium migration path in lithium-ion battery materials because of its sensitivity to lithium and ability to observe positions and concentrations at the atomic scale. With this analytical method, neutron diffraction patterns enable the lithium migration path at the atomic scale to be visualized experimentally. Spinel Li_4+xTi₅O₁₂ is remarkable for its excellent rate performance in lithium-ion battery domains. However, further elucidation is necessary to determine the lithium migration mechanism of Li_4+xTi₅O₁₂. One of the problems lies in the lack of mobility of lithium atoms, and only partial lithium migration paths can be experimentally observed. In this study, we used neutron powder diffraction to examine the lithium migration in Li_4+xTi₅O₁₂. Efforts were made to increase the mobility of the lithium atoms in Li_4+xTi₅O₁₂, including thermal excitation and modulation of the chemical state of lithium. The observation of the complete and connective lithium migration paths, which guarantee sustainable lithium migration in Li_4+xTi₅O₁₂, was accomplished and experimentally visualized. Activation energy barriers were also derived based on these neutron powder diffraction results.