The Lithium Storage Mechanism of Zero-Strain Anode Materials with Ultralong Cycle Lives

At present, graphite is a widely used anode material in commercial lithium-ion batteries for its low cost, but the large volume expansion (about 10%) after fully lithiated makes the material prone to cracking and even surface stripping in the cycle. Therefore, the development of zero-strain anode materials (volume change <1%) is of great significance. LiAl₅O₈ is a zero-strain insertion anode material with a high theoretical specific capacity. However, the Li⁺ storage mechanism remains unclear, and the cycle life as well as fast-charging capability need to be greatly improved to meet the practical requirements. In this study, LiAl₅O₈ nanorods are prepared by utilizing aluminum ethoxide nanowires as a soft template and doped with the Zr element to further improve the Li⁺ diffusion coefficient and electronic conductivity, which in turn improves cycle and rate performances. The Zr-doped LiAl₅O₈ presents a high reversible capacity of 227.2 mAh g^-1 after 20,000 cycles under 5 A g^-1, which significantly outperforms the state-of-the-art anode materials. In addition, the Li⁺ storage mechanisms of LiAl₅O₈ and Zr-doped LiAl₅O₈ are clearly clarified with a variety of characterization techniques including nuclear magnetic resonance. This work greatly promotes the practical process of zero-strain insertion anode materials.