Abstract
The composite LiFePO4/polyaniline was prepared by chemical synthesis to promote the intensification of the electrochemical properties for use as cathodes in lithium ion batteries. The X-ray diffraction (XRD) of LiFePO4 synthesized by solvothermal method were indexed to the orthorhombic structure, according to the JCPDS 40-1499. The spectra Raman and FTIR showed a high degree of ordering of LiFePO4 with interaction between LiFePO4 surface with structure conjugate of conducting polymers. The cyclic voltammogram of the composite synthesized chemically showed a significant reduction in the value of ΔE p (ΔE p = 0.20 V) when compared to LiFePO4 (ΔE p = 0.41 V), with lower charge transfer resistance values, indicating favoring electron transfer rate in the composite. Thus, the alternative synthesis route of the LiFePO4 / PAni composite was easy to handle and allowed an increase in the electrochemical properties of the LiFePO4, compared to the traditional methods that require additional thermal treatments.
Highlights
The demand for energy sources that are renewable and environmentally clean has driven research and the use of alternative energy sources instead of fossil fuel use
In the synthesis by solvothermal method is not observed the presence of peaks attributable to second phases such as Li3PO4 and Fe3(PO4)[2] because the ethylene glycol acts as a weak reducing agent and minimizes the oxidation of Fe2+ to Fe3+ during synthesis of the LiFePO417
Ethylene glycol (EG) reduced significantly the mobility rates of the different ions species (Li+, Fe2+) in this medium and it acted as a soft template for facilitating the self-assembly of in situ grown nanoparticles through forming hydrogen bonds which control the crystal growth of LiFePO421
Summary
The demand for energy sources that are renewable and environmentally clean has driven research and the use of alternative energy sources instead of fossil fuel use. The transition metal oxides have been the main subject of research in the area of cathode materials for lithium ion batteries[6] Such materials exhibit good charge storage capacity, high specific energy and excellent cycle life[7]. Among the cited cathode materials, LiFePO4 has lower toxicity, which, together with its low cost, enables its large-scale production[9,10] Despite these superior characteristics, the LiFePO4 has low ionic and electron conductivity at room temperature, about 10-5 S cm-1 and 10-10 S cm-1, respectively[11,12]. Polyaniline (PAni) is one of the most interesting in terms of its use as active component of the cathodes of lithium batteries since it has low cost, high energy density, facile synthesis and environmental friendliness. The LiFePO4/PAni composite was synthesized by chemical synthesis and its electrochemical properties as cathode material in lithium ion batteries were investigated
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