29.03.2011

Synthesis of carbon coated nanocrystalline porous α-LiFeO₂ composite and its application as anode for the lithium ion battery

M.M. Rahman^a^,^b^,^,^,, Jia-Zhao Wang^a^,^b, Mohd Faiz Hassan^a^,^b^,^c, Zhixin Chen^d and Hua-Kun Liu^a^,^b

^a Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522, Australia

^b ARC Centre of Excellence for Electromaterials Science, University of Wollongong, NSW 2522, Australia

^c Department of Science Physics, University of Malaysia Terengganu, Kuala Terengganu 20522, Malaysia

^d School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522, Australia

Received 11 January 2011;

revised 11 February 2011;

accepted 11 February 2011.

Available online 21 February 2011.

Abstract

In this work, we describe for the first time a high surface area nanocrystalline porous α-LiFeO₂-C composite anode material synthesized by a simple molten salt method, followed by a carbon coating process. The synthesized nanocomposite presents an interconnected porous architecture, as was confirmed by field emission scanning electron microscope observations. Transmission electron microscope investigations revealed that amorphous carbon was incorporated into the pores among the nanoparticles and that some nanoparticles were covered by a thin layer of amorphous carbon as well. Electrochemical measurements showed that the carbon played an important role, as it affected both the cycle life and the rate capability of the electrode. The α-LiFeO₂-C nanocomposite electrode delivered a higher reversible capacity and good cycle stability (540 mAh g⁻¹ at 1 C after 200 cycles) compared to the pure α-LiFeO₂ electrode. Good electrochemical performance of the α-LiFeO₂-C nanocomposite electrode could be attributed to the porous conductive architecture among the nanoparticles, which not only has benefits in terms of decreasing the absolute volume changes and increasing the mobility of lithium ions, but also offers conductive pathways along the whole interconnected wall in the structure, which is favourable for the transport of electrons, promotes liquid electrolyte diffusion into the bulk material, and acts as a buffer zone to absorb the volume changes. Our results indicate that α-LiFeO₂-C nanocomposite could be considered as a potential anode material for lithium-ion batteries.

Research highlights

► Synthesis of nanocrystalline porous α-LiFeO₂/C composite. ► Application as anode material for lithium ion battery. ► α-LiFeO₂/C composite electrode delivered a higher reversible capacity and good cycle stability (540 mAh g⁻¹ at 1 C after 200 cycles). ► Only 4% capacity fading is observed from 50 to 200 cycles for the α-LiFeO₂/C electrode. ► Synthesis method provides a simple and feasible platform for further advances in carbon-based nanoporous composites for different applications.