Unique Li4Ti5O12/TiO2 multilayer arrays with advanced surface lithium storage capability

Nanostructured arrays grown on metal substrates have been attracting considerable attention as promising electrode materials for energy storage systems. Herein, unique Li4Ti5O12/TiO2 multilayer arrays (LTO/TiO2 MLAs) featuring advanced surface lithium storage capability are successfully synthesized for the first time via a facile substrate-free hydrothermal method with subsequent calcination. The proposed substrate-free growth mechanism of the LTO/TiO2 MLA is demonstrated in detail. Compared to previously reported LTO and LTO/TiO2 arrays grown on various substrates, a novel multilayer array structure and remarkable surface lithium storage capability have been clearly detected in our newly prepared LTO/TiO2 MLA. The unique framework of the LTO/TiO2 MLA can not only offer abundant grain boundaries and phase interfaces for increasing the number of Li+ storage sites but also provide rich and hierarchical channels to ensure more lithium ions and electrons rapidly diffuse and migrate, contributing to advanced surface lithium storage capability. The as-prepared LTO/TiO2 MLA exhibits great practical potential for further achieving both high-capacity and high-rate lithium storage, delivering an ultrahigh reversible capacity of 193 mA h g(-1) at 0.5C and a superior rate capability of 148 mA h g(-1) at 30C between 1.0 and 2.5 V. Our present work provides a facile yet scalable and substrate-free approach for the rational design and fabrication of multilayer arrays with superior electrochemical performance. We believe that the multilayer array structure with abundant active sites and diffusion channels will attract intense interest.