Glucose-assisted synthesis and wet-chemistry preparation of pyrophosphate cathodes for rechargeable Na-ion batteries

Pyrophosphate-based materials, in particular Na2FeP2O7, constitute an interesting class of cathode compounds for rechargeable Na-ion batteries. In this work we investigate the effect of different synthetic procedures, namely: (i) glucose-assisted solid-state synthesis, and (ii) Pechini-based wet chemistry approach, on the electrochemical performances of Na2FeP2O7. Both the methods allow good specific gravimetric capacity during charge/discharge, with values close to the theoretical one at low current rates, good capacity retention and coulombic efficiency to be obtained. These results, which are better than those obtained from solid-state synthesis without added glucose, are quite independent on the different microstructures originating from the synthesis approaches, and can be attributed to the residuals of the organic fractions added during the synthesis. In addition we show that the glucose-assisted solid-state synthesis assures electrochemical stability even at relatively high currents rates (100 cycles at 1C rate).