Control of number of graphene layers using ultrasound in supercritical CO2 and their application in lithium-ion batteries

Abstract This study reports a novel strategy using ultrasound in supercritical CO2 for exfoliating graphite directly into single and few-layer graphene sheets. The mutually complementary characterizations of the as-exfoliated samples via atomic force microscopy, transmission electron microscopy and Raman spectroscopy indicate that the ultrasonic power greatly affects the number of layers and the lateral size of the graphene. Single-layer graphene with a lateral size of 50–100 nm and two-layer graphene with a lateral size of 0.5–10 μm are obtained using an ultrasonic power of 300 and 120 W, respectively. As-exfoliated graphene sheets heighten the electrochemical performance of LiFePO4 cathode materials, demonstrating graphene's remarkable electrical conductivity. The specific capacity of the LiFePO4/graphene composite cathode achieves 160 mAh/g and displays stable cycling for more than 15 cycles. This technique will enable cost-effective mass production of graphene sheets with good quality, and the as-exfoliated graphene will find wide applications, including lithium-ion batteries.

[1]  A Gupta,et al.  Raman scattering from high-frequency phonons in supported n-graphene layer films. , 2006, Nano letters.

[2]  T. Ohta,et al.  Controlling the Electronic Structure of Bilayer Graphene , 2006, Science.

[3]  N. Pu,et al.  Production of few-layer graphene by supercritical CO2 exfoliation of graphite , 2009 .

[4]  R. Ruoff,et al.  Graphene-based ultracapacitors. , 2008, Nano letters.

[5]  Hu Guoxin,et al.  Solution-based synthesis and characterization of a silver nanoparticle–graphene hybrid film , 2011 .

[6]  A. Bleloch,et al.  Free-standing graphene at atomic resolution. , 2008, Nature nanotechnology.

[7]  Xufeng Zhou,et al.  Graphene modified LiFePO4 cathode materials for high power lithium ion batteries , 2011 .

[8]  S. Stankovich,et al.  Graphene-based composite materials , 2006, Nature.

[9]  Andre K. Geim,et al.  Electric Field Effect in Atomically Thin Carbon Films , 2004, Science.

[10]  P. Feng,et al.  Fabrication and characterization of few-layer graphene , 2010 .

[11]  G. Fudenberg,et al.  Ultrahigh electron mobility in suspended graphene , 2008, 0802.2389.

[12]  J. Kysar,et al.  Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene , 2008, Science.

[13]  C. N. Lau,et al.  Superior thermal conductivity of single-layer graphene. , 2008, Nano letters.

[14]  D. Golberg,et al.  Rapid and direct conversion of graphite crystals into high-yielding, good-quality graphene by supercritical fluid exfoliation. , 2010, Chemistry.

[15]  E. Yoo,et al.  Large reversible Li storage of graphene nanosheet families for use in rechargeable lithium ion batteries. , 2008, Nano letters.

[16]  Yaping Zhao,et al.  Preparation of Two Dimensional Atomic Crystals BN, WS2, and MoS2 by Supercritical CO2 Assisted with Ultrasound , 2013 .

[17]  R. Li,et al.  3D porous LiFePO4/graphene hybrid cathodes with enhanced performance for Li-ion batteries , 2012 .

[18]  A. Hollenkamp,et al.  Carbon properties and their role in supercapacitors , 2006 .

[19]  J. Coleman,et al.  Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials , 2011, Science.

[20]  N. Rodriguez,et al.  Carbon Nanofibers: A Unique Catalyst Support Medium , 1994 .

[21]  Zhongwei Chen,et al.  Durability investigation of carbon nanotube as catalyst support for proton exchange membrane fuel cell , 2006 .

[22]  S. Stankovich,et al.  Preparation and characterization of graphene oxide paper , 2007, Nature.

[23]  Hanyang Gao,et al.  Preparation of few-layer and single-layer graphene by exfoliation of expandable graphite in supercritical N,N-dimethylformamide , 2012 .

[24]  K. Novoselov,et al.  Detection of individual gas molecules adsorbed on graphene. , 2006, Nature materials.

[25]  Guohua Chen,et al.  Preparation and characterization of graphite nanosheets from ultrasonic powdering technique , 2004 .

[26]  Xiaoning Yang,et al.  A molecular simulation of interactions between graphene nanosheets and supercritical CO2. , 2011, Journal of colloid and interface science.

[27]  Andre K. Geim,et al.  The rise of graphene. , 2007, Nature materials.

[28]  Andre K. Geim,et al.  Two-dimensional atomic crystals. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[29]  J. Flege,et al.  Epitaxial graphene on ruthenium. , 2008, Nature materials.

[30]  Wei Zhao,et al.  Study of LiFePO4 cathode modified by graphene sheets for high-performance lithium ion batteries , 2013 .