Si-Si3N4P (amorphous Si3N4 nanoparticles) and Si-Si3N4W (alpha-Si3N4 whiskers) composites as anode materials for lithium-ion batteries were synthesized by ball-milling. Ball-milling leads to the formation of inactive phases (Si(3)N(4)p 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-Si(3)N(4)p and Si-Si(3)N(4)w 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 perfortuance 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-Si(3)N(4)p? composite containing 30 -,wt.% Si in the potential range from 0.02 to 1.2 (c) 2007 Elsevier B.V. All rights reserved.