Improved Electrochemical Performance of Hydrogenated Li4Ti5O12 As Anode Materials for High-Power Li-Ion Batteries

Li₄Ti₅O₁₂ (LTO) with a spinel structure has received much attention as the most promising alternative to the conventional graphite anode material of Li-ion batteries for hybrid electric vehicle, electric vehicle, and large-scale energy storage applications, due primarily to its advantageous material properties, such as enhanced safety, good capacity retention during cycling, and high power density. Also, LTO is a zero-strain insertion material, which has excellent Li⁺ insertion/extraction reversibility with no volume change. In spite of these advantages, LTO presents a relatively poor rate capability due to its low electrical conductivity and Li⁺ diffusion coefficient. Recently, the nanostructured LTO materials coated with carbon-based materials have been extensively studied in the hope of achieving further improvement in the rate capability due to both good electrical conductivity and short Li⁺ diffusion length. However, these nanomaterials present relatively low volumetric energy density and difficulty in the electrode coating process, and also high production cost. Therefore, it is very important to develop a novel method to achieve simultaneously the enhanced electrical conductivity and volumetric energy density of LTO material.

In this work, we suggest a facile method to achieve the improved electrochemical performance of LTO anode material composed of the micro-sized primary particles for high-power Li-ion batteries. The electrochemical performances of the micro-sized LTO particles, including the rate capability and cycling stability were significantly improved by hydrogenation. The hydrogenated LTO (denoted as H-LTO) particles were obtained by thermal annealing of the P-LTO (denoted as P-LTO) particles at 800 °C for 2~7 h in hydrogen atmosphere. Thermal annealing was performed in a quartz tube furnace filled with ultrahigh purity hydrogen gas. The H-LTO particles exhibited vastly superior the rate capability and capacity retention property during cycling to the P-LTO particles at high current density, since the insertion and extraction of Li⁺ through the H-LTO particles were preferable to those through the P-LTO particles, which were probably attributed to the short diffusion length for Li⁺, innumerable reaction sites, and relatively high electrical conductivity.