Detailed investigation of Na(2.24)FePO(4)CO(3) as a cathode material for Na-ion batteries

Na-ion batteries are gaining an increased recognition as the next generation low cost energy storage devices. Here, we present a characterization of Na(3)FePO(4)CO(3) nanoplates as a novel cathode material for sodium ion batteries. First-principles calculations reveal that there are two paths for Na ion migration along b and c axis. In-situ and ex-situ Fe K-edge X-ray absorption near edge structure (XANES) point out that in Na(3)FePO(4)CO(3) both Fe(2+)/Fe(3+) and Fe(3+)/Fe(4+) redox couples are electrochemically active, suggesting also the existence of a two-electron intercalation reaction. Ex-situ X-ray powder diffraction data demonstrates that the crystalline structure of Na(3)FePO(4)CO(3) remains stable during the charging/discharging process within the range 2.0–4.55 V.