Broadband impedance spectroscopy of Li4Ti5O12: from nearly constant loss effects to long‐range ion dynamics

Abstract

AbstractLi4Ti5O12 (LTO) is known as one of the most robust and long‐lasting anode materials in lithium‐ion batteries. As yet, the Li‐ion transport properties of LTO are, however, not completely understood. Here, we used broadband impedance spectroscopy spanning a wide temperature range to investigate the full electrical response of LTO over a wide frequency range. It turned out that the isotherms recorded entail information about two relaxation processes. While at high temperatures the isotherms show a frequency independent plateau that corresponds to poor long‐range ion transport (<10−11 S cm−1 (298 K), 0.79 eV), they reveal a second region, seen at lower temperatures and higher frequencies, which we attribute to short‐range ion dynamics (10−8 S cm−1) with a significantly reduced activation energy of ca. 0.51 eV. At even lower temperatures, the isotherms are fully governed by nearly constant loss behavior, which has frequently been explained by cage‐like dynamics. The present results agree with those earlier presented by 7Li NMR spin‐lattice relaxation measurements being sensitive to dynamic processes taking place on quite different length scales. Our findings unveil complex Li+ ion dynamics in LTO and help understand its superior electrochemical properties.