Si–Si3N4 composites as anode materials for lithium ion batteries

Si–Si3N4p (amorphous Si3N4 nanoparticles) and Si–Si3N4w (α-Si3N4 whiskers) composites as anode materials for lithium–ion batteries were synthesized by ball-milling. Ball-milling leads to the formation of inactive phases (Si3N4p and Si3N4w) that can be a buffer matrix to support active silicon particles avoiding the aggregation of silicon particles during cycling. The microstructure and electrochemical performance of the Si–Si3N4p and Si–Si3N4w composites with various silicon contents were investigated in detail. It is demonstrated that the composites with the amorphous Si3N4 nanoparticles as inactive materials have larger reversible capacities and improved cycle performance due to active Si nanoparticles being supported in the buffer matrix. A high reversible (charge) capacity of 470 mA h/g is obtained for a Si–Si3N4p composite containing 30 wt.% Si in the potential range from 0.02 to 1.2 V.