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A chemically activated graphene-encapsulated LiFePO4 composite for high-performance lithium ion batteries

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Title: A chemically activated graphene-encapsulated LiFePO4 composite for high-performance lithium ion batteries

Author(s): Ha J.H; Park S.K.; Seung-Ho Yu; Aihua Jin; Jang B.C; Bong S.Y; Kim I.; Yung-Eun Sung; Piao Y.

Subject: Cath-ode materials, ; Cathode active material, ; Conducting networks, ; Cycling stability, ; Electrochemical performance, ; Lithium-ion battery, ; Microscopic observations, ; Nitrogen sorption, ; Cathodes, ; Electrochemical properties, ; Lithium alloys, ; Lithium batteries, ; Graphene, ; graphite, ; hydroxide, ; ion, ; iron, ; LiFePO4, ; lithium, ; phosphate, ; potassium derivative, ; potassium hydroxide, ; article, ; chemistry, ; power supply, ; Electric Power Supplies, ; Graphite, ; Hydroxides, ; Ions, ; Iron, ; Lithium, ; Phosphates, ; Potassium Compounds

Abstract: A composite of modified graphene and LiFePO4 has been developed to improve the speed of charging-discharging and the cycling stability of lithium ion batteries using LiFePO4 as a cathode material. Chemically activated graphene (CA-graphene) has been successfully synthesized via activation by KOH. The as-prepared CA-graphene was mixed with LiFePO4 to prepare the composite. Microscopic observation and nitrogen sorption analysis have revealed the surface morphologies of CA-graphene and the CA-graphene/LiFePO4 composite. Electrochemical properties have also been investigated after assembling coin cells with the CA-graphene/LiFePO 4 composite as a cathode active material. Interestingly, the CA-graphene/LiFePO4 composite has exhibited better electrochemical properties than the conventional graphene/LiFePO4 composite as well as bare LiFePO4, including exceptional speed of charging-discharging and excellent cycle stability. That is because the CA-graphene in the composite provides abundant porous channels for the diffusion of lithium ions. Moreover, it acts as a conducting network for easy charge transfer and as a divider, preventing the aggregation of LiFePO4 particles. Owing to these properties of CA-graphene, LiFePO4 could demonstrate enhanced and stably long-lasting electrochemical performance. © 2013 The Royal Society of Chemistry.