3D yolk-shell Si@void@CNF nanostructured electrodes with improved electrochemical performance for lithium-ion batteries
Sojeong Choi, Min-Cheol Kim, Sang-Hyun Moon, Ji-Eun Lee, Yeon-Kyung Shin, Eun-Soo Kim, Kyung-Won Park
Index: 10.1016/j.jiec.2018.03.035
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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 9 h 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 304.9 mAh g−1 at a current density of 200 mA g−1 after 500 cycles and an improved high rate performance (166@2000 mA g−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.