BCl₃ modified tris(dichloromethylsilylethyl)borane as a precursor for SiBCN ceramics applied in lithium-ion battery anodes

Tris(dichloromethylsilylethyl)borane is a compound containing a B–C bond and Cl and H elements. Herein, we propose a novel method to synthesize polyborosilazanes using tris(dichloromethylsilylethyl)borane and boron trichlorosilane as boron sources and hexamethyldisilazane as a nitrogen source. The microstructure and chemical composition of the as-synthesized polyborosilazanes and as-annealed SiBCN ceramics were investigated using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope methods. The organic precursors were converted entirely into inorganic ceramics at 800 °C, and the ceramic yield of the polyborosilazanes was 88% at 1000 °C. SiBCN ceramics with irregular shapes contained chemical bonds of B–N, Si–N, and Si–C at 1500 °C and retained an amorphous structure below 1600 °C. After the first cycle, the fabricated SiBCN ceramic anodes exhibited a reversible capacity of 261.3 mA h/g, which was 2.6 times that reported in the literature (101 mA h/g). The discharge capacity decreased to 157.6 mA h/g after 30 cycles. The satisfactory electrochemical performance of the resulting SiBCN ceramic anodes can be attributed to the formation of conductive carbon species favoring the transport properties of lithium ion.