Hydrothermal synthesis, structural elucidation and electrochemical properties of three nickel and cobalt based phosphonates as anode materials for lithium ion batteries

Abstract Three phosphonates coordination polymers containing different metal ions with the molecular formula C15H32N3M2O16P [M = Ni (PN1) and Co (PC1)] and C30H50N6Ni2.67Co1.33O27P2 (PNC) were prepared by mild hydrothermal synthesis at 100 °C for 48 h. All 3 phosphonates are composed of two different ligands: N-(phosphonomethyl)iminodiacetate (pmida) and 4,4′-bipyridine (4,4′-bpy). The structures of the materials were elucidated via single crystal X-ray diffraction techniques which show all compounds have the similar hybrid three dimensional (3-D) super structures via hydrogen bonds in triclinic symmetric and P-1 space group. The morphologies of the particles were characterized by SEM showing the irregular block shape. The electrochemical properties of 3 phosphonates were studied by cyclic voltammetry (CV), alternating current impedance spectroscopy (EIS) and constant current charge-discharge measurements. The discharge capacity remains to 288.1 mAh/g at 100th cycle with a current density of 50 mA/g and still behaves a growing trend. The CV data shows the large range of 0–10 V with the reduction peak at 4.7 V suggest that PC1 may be suitable for preparing high voltage Libs. The performance of PC1 indicate promising for potential negative electrode material for lithium ion batteries.