(173e) Graphene-Encapsulated Hollow Fe3O4 Nanoparticle Aggregates As a High Performance Anode Material for Lithium Ion Batteries

Graphene-Encapsulated
Hollow Fe₃O₄ Nanoparticle
Aggregates as a High Performance Anode Material for Lithium Ion Batteries

Dongyun Chen^1,2, Ge Ji¹, Yue Ma¹, Jim Yang Lee¹ and Jianmei Lu²

¹Department of Chemical
& Biomolecular Engineering, Faculty of Engineering, National University of
Singapore, 10 Kent Ridge Crescent, Singapore, 119260; Tel: (65) 65162186; E-mail:
cheleejy@nus.edu.sg.

²Key Laboratory of
Organic Synthesis of Jiangsu Province, Key Laboratory of Absorbent Materials
and Techniques for Environment, College of Chemical, Chemical Engineering and
Materials Science, Soochow University, Suzhou, China, 215123; E-mail: lujm@suda.edu.cn

In this work we combined the unique properties
of graphene sheets and a hollow assembly of nanoparticles to simultaneously
provide large reversible Li⁺ storage capacity,
good rate performance and long cycle life. Specifically graphene-encapsulated
ordered aggregates of Fe₃O₄ nanoparticles with
nearly-spherical geometry and hollow interior (G-HPM)
were synthesized by a simple self-assembly process. The
HPM particles were first prepared by a one-pot hydrothermal synthesis. They
were then modified by 3-aminopropyltriethoxysilane (KH550) to acquire a positive
surface charge, which enabled electrostatic assembly with negatively charged
graphene oxide. Finally, a chemical reduction was used to reduce the graphene
oxide to graphene; finalizing the packaging of HPM particles in individual
graphene cages. This assembly could be carried out under relatively mild
conditions; thereby minimizing the perturbations to the properties of HPM. In
our design, the open interior structure has adapted well to the volume change
in repetitive Li⁺ insertion and extraction reactions; and the
encapsulating graphene connects the Fe₃O₄ nanoparticles
electronically. The composite particles showed a stable high specific
reversible capacity of about 897 mA h g^-1 which was nearly unvarying
over 50 cycles. These graphene-Fe₃O₄ composites are therefore
a capable reversible Li⁺ host with high storage capacity and good
cycle life which can be cycled at high rates.