Carbon Encapsulated Silicon Nanoparticles as Anodes for Lithium Ion Batteries

An investigation is carried out on the encapsulation of silicon with carbon nanomaterial via gas phase synthesis. Two methods were used; a spark discharge synthesis and RF induction thermal plasma. In the former, the use of silicon and graphite electrodes resulted in the formation of encapsulated nanoparticles 3-5 up to 70 nm in size. The particles were typically agglomerates of sub particles, encapsulated with 3-5 graphitic layers. Synthesis with RF thermal plasma yielded carbonaceous powders comprising Si, SiC and graphite. The particles were on average 82 nm encapsulated with 7-10 nm thick graphitic layers. Discharge capacity of the electrode made with thermal plasma powder showed a rapid decay implying that the encapsulation did not provide the expected stability to silicon. Smaller particles size and sequential synthesis might be necessary to obtain improved performance, i.e. first synthesize Si nanoparticles without the formation of SiC and then encapsulating them with graphitic material.