Robust hexagonal nut-shaped titanium(IV) MOF with porous structure for ultra-high performance lithium storage

Metal-organic frameworks (MOFs) can be applied as LIBs electrode materials with novel structure and potential for development, due to their ability to provide metal ions and organic ligands with redox activity and porosity/channel for the diffusion of electrolyte ions. Here, a Ti-based MOF (Ti-MOF) with stable Ti-skeleton and hexagonal nut shape is synthesized and selected for LIBs. The Ti-MOF exhibits a specific capacity of the maximum initial discharge capacity of 1590.24 mAh g(-1) at 100 mA g(-1), and it displayed excellent structural reversibility even over 8000 cycles. Density functional theory calculations demonstrate the carboxyl groups act as an electrochemically active site to reversibly bond with Li+, and the Ti octahedron functions as stable skeleton. The porous structure provides channels for the dein-tercalation of Li+, enhancing the contribution of the pseudocapacitive process, but the overall electrochemical rate determining step is still controlled by Li+ diffusion. (C) 2018 Elsevier Ltd. All rights reserved.