Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO4NO3 (A = NH4/Li, K)

A new class of mixed polyanionic transition metal phosphatonitrate with the general formula AFePO(4)NO(3) (A = NH4/Li, K) has been synthesized following a computational predictive study based on DFT calculations. Structures of the crystalline products have been solved through synchrotron powder XRD and single-crystal XRD techniques. This class of materials exhibits the rare coordination of PO43- and NO3- to a single transition metal center and is structurally related to the rare mineral bonshtedtite (Na3FePO4CO3), which has been used as the initial model for predicting phosphatonitrates. (NH4)(1-x)LixFePO4NO3 has been found to be capable of reversible electrochemical Li- and Na-ion intercalation in the potential range 2.0-4.2 V at a theoretical capacity of ca. 116 mAh-g(-1). Various aspects of structural, chemical/electrochemical, and spectroscopic features of AFePO(4)NO(3) have been discussed in this article.