THESIS
2015
xviii, 121 pages : illustrations ; 30 cm
Abstract
Among various types of anode materials, SnO
2 and Si-based materials are considered as the
most promising anode candidates for next generation lithium ion batteries, due to their high
theoretical specific capacity, low operating potential, natural abundance and environmental
benignity. The main drawbacks of SnO
2 and Si-based anode materials are their large
volume change during alloying/dealloying processes and low electrical conductivity. To
solve these problems, in the present work, graphene oxide (GO) was introduced as the
carbon matrix to ameliorate the poor electrical conductivity and buffer the large volume
variation. Further modifications of SnO
2/GO and Si/GO nanocomposites have also been
investigated.
The SnO
2/GO nanocomposites were synthesized by a facile hydrotherma...[
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Among various types of anode materials, SnO
2 and Si-based materials are considered as the
most promising anode candidates for next generation lithium ion batteries, due to their high
theoretical specific capacity, low operating potential, natural abundance and environmental
benignity. The main drawbacks of SnO
2 and Si-based anode materials are their large
volume change during alloying/dealloying processes and low electrical conductivity. To
solve these problems, in the present work, graphene oxide (GO) was introduced as the
carbon matrix to ameliorate the poor electrical conductivity and buffer the large volume
variation. Further modifications of SnO
2/GO and Si/GO nanocomposites have also been
investigated.
The SnO
2/GO nanocomposites were synthesized by a facile hydrothermal method. The
optimal conditions were found to be 12.5 wt. % of GO, 3 wt. % of vinylene carbonate (VC)
and 48 hours hydrothermal reaction time. Under these conditions, SnO
2/GO nanocomposite
delivers a reversible diacharging capacity of 891 mAh g
-1 with a Coulombic efficiency of
99% after 200 cycles at a current density of 800 mA g
-1.
The graphene oxide/polydopamine-coated Si nanocomposite (GO/PD-Si) was synthesized
by a facile solution-based chemical method at room temperature. The nanocomposite with a
PD coating layer of ~2 nm exhibits a high reversible specific capacity and excellent cycling
stability (1074 mAh g
-1 after 300 cycles at 2100 mA g
-1) as anode material for lithium ion
batteries. The PD coating layer can not only serve as a cushion to buffer the volume change
of Si nanoparticles (NPs) during charge/discharge process and avoid direct contacts of Si
NPs with liquid electrolyte, but also modify the surface property of Si NPs by introducing
secondary amine groups, which can form amide groups with carboxyl groups and hydrogen
bonds with hydroxyl groups on GO. These chemical interactions firmly anchor Si NPs to
GO so that aggregations of Si NPs could be prevented. Moreover, the good lithium ion
conductivity of PD is beneficial for rate performance.
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