The Preparation and Applications of Carbon-Coated Silicon Composites as Negative Electrodes for Lithium Cells
Date Issued
2015
Date
2015
Author(s)
Lo, Chieh-min
Abstract
Silicon is regarded as one of the most promising anode materials for Li-ion batteries due to its high theoretical capacities (~4200mAh/g), which is 10 times higher than conventional graphite (372mAh/g) used in commercial Li-ion batteries. However, Si-based Li-ion battery exhibits low intrinsic electrical conductivity and dramatic volumetric variation (~350%) during the lithiation and delithaition process. To improve the stability of Si-based anodes, carbon-coated Si composite materials have been developed. In this study, we prepare a graphite/carbon-coated Si nanoparticles hybrid to overcome the poor cycling stability and enhance the intrinsic electrical conductivity. Efficient and low-cost thermal treatment is introduced to prepare new anode materials. Initially, honey, which is adopted as carbon precursor, is mixed with Si nanoparticles and graphite via ultrasonication. Next, amorphous carbon coats Si nanocomposites prepared by pyrolysis at 1000 oC for 2 hr in Ar atmosphere. Within the materials, Si nanoparticles are wrapped evenly among amorphous carbon layers and firmly attached to graphite, which indicate the strong interactions among Si nanoparticles、amorphous carbon and graphite. This structure effectively suppress the huge volumetric variation (189% after 50 cycles ) and improve the cycling stability. In addition, it keep the electrode materials highly conductive. Consequently, the composites (honey:nano-Si: KS-6 ,5:1:0.25 in weight) exhibit outstanding specific capacity for cycling performance of 711mAh/g after 51 cycles at 100mA/g . The graphite/carbon-coated Si nanoparticles hybrid with distinguished electrochemical performance is prepared by a low-cost, simple pyrolysis method, making it greatly promising for a large-scale production of high-performance Si-based anode materials.
Subjects
Lithium-ion battery
Silicon
Carbon-coated Si materials
SDGs
Type
thesis
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