Study of C/Si composites as anode materials of lithium-ion batteries
Date Issued
2012
Date
2012
Author(s)
Chang, Yung-Wei
Abstract
Abstract
Due to the invention of hybrid electric vehicles and electric vehicles in recent years, the commercialized batteries cannot make effort of loading. So we need lithium –ion batteries beneficial for their high energy density. But lithium-ion batteries with graphite used as anode materials were not efficient for the operations, so a lot of researchers began to investigate the improvement of electrode materials, components of full-scale batteries, etc.., to construct new lithium-ion batteries with higher energy density for the loading.
In aspect of research of anode materials, many researchers started to investigate silicon to be a new one by its nature of semiconductor, good specific capacity, and lithium-insertion capacity. However, because the volume expansion occurs during operation, resulting mechanical cracking, further losing electric contact with electrolytes and shrinking the cyclability, they found more ways to resolve this disadvantage. One of them was to coat carbonaceous materials on the surface of silicon to form a carbon/silicon composite.
This study was based the effect of different particle-size of silicon (commercial available micron-scale and nano-scale ones), with different processing temperature and holding time to perform the batch pyrolysis of silicon-glucose mixture, followed by analysis of Raman spectrometer to find the coated carbonaceous materials, enhancing mechanical properties of materials, disordered carbons were all detected in various conditions; analysis of X-ray diffractometer to find the existence of crystalline phase, in which the disappearance of specific crystalline phases was observed except for those obtained under 500℃; measurement of thermal differential analyzer to determine the amount of carbonaceous materials, and the amount of carbons of was higher above 50% under the preparation of processing temperature of 300℃ and 400℃; analysis of scanning electron microprobe to observe the morphology, the coating was checked to be well-defined. Then, aqueous SCMC(sodium carboxymethylcellulose) solution was used to bind graphene and pyrolyzed-carbon/silicon composites by mortar. Eventually, assembly half-cell to test the specific capacity of materials with galvanostatic mode by a battery automatic tester for the purpose of investigating the effect of particle size of silicon as anode materials on the performance of Li-ion batteries. By pristine-silicon-based electrodes, nano-Si-based electrode had better performance, its initial discharge capacity was 600mAh/g, charge capacity was 575.24mAh/g; composite-electrodes by the silicon with coating, the one pyrolyzed at 400℃ for 4 hours had better performance, initial discharge capacity was 601.05mAh/g; charge capacity was 420.66mAh/g.
Subjects
C/Si composite
graphene
anode materials of lithium-ion batteries
SDGs
Type
thesis
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