Electrochemical Li Storage Properties of Carbon-Rich B–C–N Ceramics

Amorphous BCN ceramics were synthesized via a thermal conversion procedure of piperazine–borane and pyridine–borane. The synthesized BC₂N and BC₄N ceramics contained, in their final amorphous structure, 45 and 65 wt % of carbon, respectively. Elemental analysis revealed 45 and 65 wt % of carbon for BC₂N and BC₄N, respectively. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed the amorphous nature of studied compounds. Lateral cluster size of carbon crystallites of 7.43 and 10.3 nm for BC₂N and BC₄N, respectively, was calculated from Raman spectroscopy data. This signified a higher order of the carbon phase present in BC₄N. The electrochemical investigation of the low carbon BC₂N composition as anodes for Li-ion batteries revealed initial capacities of 667 and 235 mAh·g⁻¹ for lithium insertion/extraction, respectively. The material with higher carbon content, BC₄N, disclosed better reversible lithium storage properties. Initial capacities of 1030 and 737 mAh·g⁻¹ for lithium insertion and extraction were recovered for carbon-rich BC₄N composition. Extended cycling with high currents up to 2 C/2 D revealed the cycling stability of BC4N electrodes. Cycling for more than 75 cycles at constant current rates showed a stable electrochemical behavior of BC₄N anodes with capacities as high as 500 mAh·g⁻¹.