Morphology-dependent electrochemical performance of Ni-1,3,5-benzenetricarboxylate metal-organic frameworks as an anode material for Li-ion batteries.

The performance of energy storage materials is substantially dependent on their nanostructures. Herein, Ni-1,3,5-benzenetricarboxylate metal-organic frameworks (Ni-BTC MOFs) with different morphologies are controllably synthesized using a facile solvothermal method by simply adjusting the solvent and their electrochemical performance as an anode material for lithium-ion batteries is thoroughly investigated. Among the synthesized Ni-BTC MOFs with different morphologies, a hierarchical mesoporous flower-like Ni-BTC MOF (Ni-BTCEtOH) assembled from two-dimensional nanosheets shows the best electrochemical properties including a high capacity of 1085 mA h g-1 at 100 mA g-1 (358 mA h g-1 at 5000 mA g-1), excellent cycling stability at 1000 mA g-1 for 1000 cycles, and great rate performance, which is superior to most of the reported MOF-based anode materials for lithium-ion batteries. The outstanding electrochemical performance of Ni-BTCEtOH is originated from its unique and stable hierarchical mesoporous morphology with a high specific surface area and improved electrical/ionic conductivity. Moreover, our study demonstrates that the charge-discharge mechanism of the Ni-BTCEtOH electrode involves the insertion/extraction of Li ions to/from the organic moieties in Ni-BTCEtOH during the charge-discharge process without the direct engagement of Ni2+. This work highlights that the nanostructure design is an effective strategy to obtain promising energy storage materials.