Li3Fe2(HPO3)3Cl: an electroactive iron phosphite as a new polyanionic cathode material for Li-ion battery†
A novel lithium containing iron-chlorophosphite, Li3Fe2(HPO3)3Cl has been synthesized by employing low melting phosphorous acid flux. The single-crystal X-ray structure determination established that the compound has a 3-dimensional structure built up by edge-shared octahedral dimers and phosphite moieties that create narrow channels along the a- and b-axis. Two crystallographically independent Li ions are located in those channels. The compound was further characterized by TGA, IR, magnetic measurements, and Mössbauer spectroscopy. Magnetic measurements indicate that the compound has a field-induced metamagnetic transition. In this article we report for the first time an iron chloro-phosphite, Li3Fe2(HPO3)3Cl, as a new polyanion-based cathode with a promising electrochemical activity that shows an average voltage of 3.1 V vs. Li+/Li for the Fe2+/Fe3+ redox couple and a reversible capacity of 70 mA h g−1. Details of electrochemical studies including cyclic voltammetry, galvanostatic charge–discharge, and electro-impedance spectroscopy are reported here.