Preparation and Lithium Storage Properties of Low Cost Silicon Nanotube/Carbon Composites

The preparation of silicon anode materials via reduction of silicate minerals can improve the electrochemical properties and reduce the production cost. In this paper, silicon-carbon composites were prepared by a simple evaporation solvent method with natural halloysite aluminothermic reductive product as a raw material and asphalt as a carbon source. The results show that silicon exists in the form of nanotubes with a diameter of approximately 30 nm. The carbon layer is uniformly coated on the silicon nanotubes, which increases the diameter of the silicon carbon composite. The thickness of the carbon layer is approximately 7 nm. The carbon exists in an amorphous structure, and the carbon coating leads to the decrease of the specific surface area. According to the results of electrochemical tests, the optimum electrochemical performance of silicon-carbon composites can be obtained at a mass fraction of coated carbon of 15%, i.e., the first charge and discharge capacities of 1387.8 mA·h/g and 1615.7 mA·h/g, respectively, and the first coulomb efficiency of 85.9%. The silicon-carbon composites maintain the first charge discharge efficiency of silicon nanotubes, and greatly improve the cycle performance. Compared with the 200 cycles capacity retention rate of silicon nanotubes of 38%, the 200 cycles capacity retention rate of silicon-carbon composites coated with a carbon content of 15% is increased by 45.8%. The specific capacity of silicon-carbon composites coated with a carbon content of 15% is 1065.6 mA·h/g after 500 cycles. The capacity retention rate is 76.8%.