We report synthesis of a sheet-like composite composed of hexagonal boron nitride (or BN) chemically integrated with silicon carbonitride (SiCN) matrix via a simple pyrolysis route. The composite offers several unique features such as improved electrical conductivity, high-temperature oxidation resistance (at 1000 degrees C), and high electrochemical activity toward Li-ions generally not observed in SiCN or boron-doped SiCN. Tested as electrode in Li-ion half-cell, SiCN/BN show charge capacity of similar to 517 mAh g(-1) at 100 mA g(-1) and 283 mAh g(-1) at 2400 mA g(-1) with respect to total weight of electrode. Additionally, a stable charge capacity of similar to 401 mAh g(-1) at 100 mA g(-1) is retained even after continuous operation for 1000 cycles at 1600 mA g(-1). Chemical characterization of the composite suggests that addition of BN to polysilazane in moderate amounts (similar to 10 wt %) and subsequent pyrolysis resulted in an increased free-carbon content in the amorphous SiCN phase, which exceeded the percolation limit, leading to the improved electrical conductivity and Li-reversible capacity.