Reversible NaFePO4 electrode for sodium secondary batteries

The behavior of a NaFePO4 cathode, obtained by electrochemical Li―Na exchange of LiFePO4 olivine, is characterized in a sodium battery. The NaFePO4 electrode here developed shows remarkable electrochemical properties in the sodium cell, such as long charge–discharge cycle life and high rate capability. X-ray diffraction analysis reveals that the NaFePO4 electrode keeps its original structure upon 50 charge–discharge cycles. The Na/NaFePO4 battery operates with a working voltage of 2.7 V and a stable capacity of 125 mAh g− 1, namely at 80% of the theoretical value. The results here reported demonstrate that the olivine NaFePO4 electrode is indeed a very promising positive electrode for the development of high performance, advanced sodium batteries.