3D yolk–shell Si@void@CNF nanostructured electrodes with improved electrochemical performance for lithium-ion batteries

Abstract

Si-based anode materials are studied to overcome the limitations of high-capacity lithium-ion batteries (LIBs). However, Si-based anodes have critical drawbacks such as volumetric electrode expansion during cycling in LIBs, that result in deterioration in cycling performance. Herein, we prepare 3D yolk–shell Si and carbon nanofiber (CNF) nanostructured electrodes with different void portions (Si@void@CNF-x) using oxidation, etching, and electrospinning process. The portions of the void in the Si@void@CNF electrodes can be controlled by electrospinning with Si powder oxidized at 700°C under an air atmosphere for a reaction time (x) of 3, 6, and 9h followed by chemically etching in HF solution. The electrodes are structurally characterized using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The charge/discharge and rate performance of the electrodes is evaluated in the coin-type cells. Si@void@CNF-6 shows a highest reversible discharge capacity of 304.9mAhg−1 at a current density of 200mAg−1 after 500 cycles and an improved high rate performance (166@2000mAg−1 after 500 cycles), compared to Si@void@CNF-3 and Si@void@CNF-9. The particular void portion in the Si@void@CNF-6 can be responsible for the superior LIB performance, representing the efficiently volumetric expansion-relieved electrode structure during cycling.