Structural engineering enabled 2D metal-organic frameworks nanosheets with fast Li+ transfer for Li ion batteries

Li ion batteries (LIBs) are nowadays widely used in wearable portable devices and electric vehicles, but the low specific capacity and unstable structural stability of commercial graphite anode have limited further performance improvement of the LIBs. Hence, it is needed to explore an anode material with better electrochemical performance. Metal-organic framework (MOF) has aroused much interest due to its good mechanical performance and controllable structure. However, most of MOFs are electrical insulators with low charge mobility and the thick bulk usually has long-range diffusion of Li + , resulting in rapid capacity decay at high current densities. In this work, we employ a bottom-up approach, in which the structure-directing agent was used to induce deprotonation of the carboxylic acid groups and non-covalent interactions, thus facilitating the anisotropic growth of hierarchical structures while suppressing unwanted 3D aggregation. Attributing to the thin thickness of MOF nanosheets, the transport channels of Li + have been greatly reduced, which was beneficial for the high-rate performance. Meanwhile, benefiting from in-plane charge delocalization and extended π-conjugation of 2D nanosheets, the electronic conductivity of MOF has been effectively improved. As a result, the 2D MOF-based anode materials displays an ultra-high reversible specific capacity of 1443 mAh g −1 with the capacity retention of almost 100 % after 100 cycles. Besides, it exhibits outstanding high-rate performance with 1000 mAh g −1 retaining at the high current density of 2000 mA g −1 , suggesting the good application value in LIBs.