Electrochemical behaviour of tin borophosphate negative electrodes for energy storage systems

Tin borophosphate compounds doped with antimony, Sn2BP1−xSbxO6 (x = 0–0.3), have been prepared and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transmission infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) and galvanostatic measurements. XRD patterns of all the samples were indexed to the tetragonal system. The EIS showed that the conductivities are enhanced by antimony doping. It was observed that the Warburg impedance coefficient (σw) was 1163.265 Ω cm2 s−0.5 for the Sn2BP0.9Sb0.1O6 (x = 0.1) sample, and this was the lowest value compared to those of the other samples. Sn2BP0.9Sb0.1O6 (x = 0.1) showed the highest specific discharge capacity of 1050 mAh g−1 among all the samples and a reversible capacity of 540 mAh g−1 at the 150th cycle.