Direct formation of LiFePO4/graphene composite via microwave-assisted polyol process

作者：Lim Jinsub; Gim Jihyeon; Song Jinju; Dang Thanh Nguyen; Kim Sungjin; Jo Jeonggeun; Mathew Vinod; Kim Jaekook^*

来源：Journal of Power Sources, 2016, 304: 354-359.

DOI：10.1016/j.jpowsour.2015.11.069

• Lithium ion battery
• Nanocomposite cathodes
• Graphene nanosheets
• Microwave-assisted polyol synthesis
• Electrochemistry

The present study reports on the direct synthesis of LiFePO4 nanoparticles and graphene nanosheets to form a composite cathode (LFP/GNs) in a one-step microwave-assisted polyol reaction. The polyol reaction induced by microwave irradiation for a few minutes produces nanocrystalline LFP and graphene nanosheets simultaneously from lithium, iron and phosphorus and carbon (5 wt% of graphite oxide) sources, respectively, used as starting precursors. Powder X-ray diffraction (XRD), electron microscopy, and atomic force microscopy (AFM) studies on microwave-reacted sample obtained using just graphite oxide confirms the formation of graphene nanosheets separately. Whereas, electron microscopy studies on the LFP/GNs composite reveals that olivine nanoparticles of average sizes ranging between 5 and 20 nm are well dispersed on the graphene nanosheets. Electrochemical measurements reveal that the LiFePO4/GNs nanocomposite cathodes registered enhanced discharge capacities (79 and 108 mAh g(-1) for the as prepared and annealed composite cathodes, respectively) at 32 C rates with good capacity retention capabilities. The AC impedance measurements confirm that the enhanced cathode properties of the LFP/GNs nanocomposite are ascribed to the improved electronic conductivity of the graphene nanosheets and the nano-sized particles. The slightly better electrochemical properties of the annealed LFP/GNs are attributed to its higher crystallinity.

• 出版日期2016-2-1