Enhancing the Lithium Storage Capacities of Coordination Compounds for Advanced Lithium-Ion Battery Anodes via a Coordination Chemistry Approach

The influence of the water molecule on both the structural dimensionality and the lithium storage capacities of four coordination compounds was studied. Increasing the reaction temperature to remove the terminal water ligand of discrete coordination compounds [M(HNA)2(H2O)4] (H2NA = 5-hydroxynicotinic acid, M = Co for 1 and Ni for 2) led to forming three-dimensional (3D) coordination polymers [M(NA)] n (M = Co for 3 and Ni for 4). When 1-4 were investigated as active anode materials for lithium storage at 100 mA g-1, the relatively low capacities of 455 and 411 mA h g-1 were obtained after 60 cycles with discrete 1 and 2, while that of 3 and 4 showed high capacities of 618 and 610 mA h g-1 after 100 cycles. Detailed mechanism studies by powder X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy showed that the structural dimensionality change induced by water molecules can greatly contribute the cyclability and rate performance for coordination compounds as anode material for lithium storage.