Self-Assembly of Polyoxometalate-Resorcin[4]arene-Based Inorganic-Organic Complexes: Metal Ion Effects on the Electrochemical Performance of Lithium Ion Batteries.

Polyoxometalate (POM)-resorcin[4]arene-based inorganic-organic complexes are a kind of potential multifunctional materials for their adjustable structures and diverse functions. They have potentials applications for lithium ion batteries (LIBs). Additionally, the relationship between different coordinated metal ions and electrochemical performance was also rarely investigated. Herein, three functionalized POM-resorcin[4]arene-based inorganic-organic materials, [Co2(TMR4A)2(H2O)10][SiW12O40]·2EtOH·4.5H2O (1), [Ni2(TMR4A)2(H2O)10][SiW12O40]·4EtOH·13H2O (2) and [Zn2(TMR4A)2(H2O)10][SiW12O40]·2EtOH·2H2O (3), have been synthesized. Further, to enhance the conductivities of these compounds, 1-3 were doped with reduced graphene oxide (RGO) to gain composites 1@RGO-3@RGO, respectively. As anode materials for LIBs, 1@RGO-3@RGO can deliver very high discharge capacities (1445.9, 1285.0 and 1095.3 mAh g-1, respectively) in the initial run, and show the discharge capacities of 898, 665 and 651 mAh g-1 at the current density of 0.1 A g-1 over 100 runs, respectively. More importantly, the discharge capacities of 319, 283 and 329 mAh g-1 were still maintained for 1@RGO-3@RGO even after 400 cycles at the large current density (1 A g-1).