Silicon Single Walled Carbon Nanotube-Embedded Pitch-Based Carbon Spheres Prepared by a Spray Process with Modified Antisolvent Precipitation for Lithium Ion Batteries

Si is regarded as a next-generation anode material for high-energy density lithium-ion batteries (LIBs). However, Si-based anode materials cause intractable problems that result in ceaseless capacity decay and poor cyclic performance. In this study, two types of industrial wastes, Si powder (from the photovoltaic industry) and pitch (from petroleum residue), were selected as the active material and carbon source, respectively, for preparing a Si single-walled carbon nanotube (SWCNT)-embedded carbon composite. A good conductive pathway was created by the SWCNTs, and the inner voids in the composite increased its conductivity and provided extra space for accommodating the volume expansion of lithiated Si. In addition, a porous pitch-based spherical composite with embedded Si and SWCNTs was fabricated through a designed one-step process using a combination of the spray-drying and antisolvent precipitation techniques and a series of thermal treatments. The cycling test results revealed that the composite showed the high reversible specific capacities of 2001 mAh g–1 at 1 A/g (0.5 C) with a retention of 66.1% and 1682 mAh g–1 at 1 A/g (0.5 C) with a retention of 55.6% after the 100th and 200th cycles, respectively. These results imply that the pitch-derived soft carbon and SWCNTs provided an excellent conductivity, and the porous structure of the composite accommodated the stress produced by the Si expansion.