Lithium-Ion-Based Electrochemical Energy Storage in a Layered Vanadium Formate Coordination Polymer.

A vanadium formate (VF) coordination polymer and its composite with partially reduced graphene oxide (prGO), namely VF-prGO, can be applied as anode materials for Li-ion based electrochemical energy storage (EcES) systems in the potential range of 0-3 V (vs Li+ /Li). This study shows that a reversible capacity of 329 mAh g-1 at a current density of 50 mA g-1 after 50 cycles can be realized for VF along with a high rate capability. The composite exhibits even a higher capacity of 504 mAh g-1 at 50 mA g-1 . A good capacity retention is observed even after 140 cycles for both VF and the composite. An ex-situ X-ray photoelectron spectroscopy study indicates the involvement of V3+ /V4+ redox couple in the charge storage mechanism. A significant contribution of this reversible capacity is attributed to the pseudocapacitive behavior of the system.