Abstract
It has been reported that improving electrical conductivity and maintaining stable structure during discharge/charge process are challenge for Si to be used as an anode for lithium ion batteries (LIB). To address this problem, milkweed (MW) was carbonized to prepare hollow carbon microtubes (HCMT) derived from biomass as an anode template for LIB. In order to improve electrical conductivity, various materials such as chitosan (CTS), agarose, and polyvinylidene fluoride (PVDF) are used as carbon source (C1, C2, and C3) by carbonization. Carbon coated HCMT@Si composits, HCMT@Si@C1, HCMT@Si@C1@C2, and HCMT@Si@C1@C3, have been successfully synthesized. Changes in structure and crystallinity of HCMT@Si composites were characterized by using X-ray diffraction (XRD). Specific surface area for samples was calculated by using BET (Brunauer–Emmett–Teller). Also, pore size and particle size were obtained by particle and pore size analysis system. The surface morphology was evaluated using high resolution scanning electron microscopy (HR-SEM), Field Emission transmission electron microscopy (TEM). The thermal properties of HCMT@Si composites were analyzed by thermogravimetric analysis (TGA). Our research was performed to study the synthesis and electrochemical performance of Si composite with HCMT by the carbonization of natural micro hollow milkweed to form an inner space. After carbonization at 900 °C for 2 h in N2 flow, inner diameter of HCMT obtained was about 10 μm. The electrochemical tests indicate that HCMT@Si@C1@C3 exhibits discharge capacity of 932.18 mAh/g at 0.5 A/g after 100 cycles.
Highlights
It has been known Silicon (Si) has many advantages such as high theoretical capacity (4200 mAh/g), non-toxic, low cost, and abundant reserve [1,2,3,4,5,6]
hollow carbon microtubes (HCMT) displays a broad feature at 22.8◦ and 44.5◦, indicating that carbon structure is dominant in the obtained HCMT
It was reported that the peak for willow catkins, wheat straw and cotton fibers around 21.7◦ should arise from the cellulose they owned and shift to the right a little by increasing the temperature of carbonization [23,33]
Summary
It has been known Silicon (Si) has many advantages such as high theoretical capacity (4200 mAh/g), non-toxic, low cost, and abundant reserve [1,2,3,4,5,6]. Energies 2020, 13, 5124 graphite, and hard carbon are widely applied for Si coating and the mixture of high carbon Si/carbon composite was synthesized [13,14,15]. It was shown a limitation in the number of times the cycle test. Other researchers have reported that the specific capacity for porous Si/C anode is 600~750 mAh/g for LIB after 100 cycles [2,4,13,14]. It is confirmed that carbon materials in the silicon–carbon composite can improve the electronic conductivity of composite
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