Enhanced conductivity and electrical relaxation studies of carbon-coated LiMnPO4 nanorods

• Published in: Ionics 2013-03, Vol.19 (3), p.461-469
• Main Authors: Kumar, P. Ramesh, Venkateswarlu, M., Misra, Manjusri, Mohanty, Amar K., Satyanarayana, N.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Optical and Electronic Materials; Original Paper; Renewable and Green Energy
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-012-0778-9

Lithium manganese phosphate (LiMnPO 4 ) nanorods were synthesized using the modified polyol method. Polyvinylpyrrolidone was used as a stabilizer to control the shape and size of LiMnPO 4 nanorods. Resin coating process was used to coat the carbon over the LiMnPO 4 nanorods. X-ray diffraction and Fourier transform infrared spectroscopy results showed the formation of LiMnPO 4 crystalline phase. The TEM image shows a uniform coating of the nano size (2.3 nm) carbon over the surface of LiMnPO 4 nanorods and the EDS spectrum of the carbon-coated LiMnPO 4 nanorods confirming the presence of carbon element along with the other Mn, P, and O elements. Impedance measurements were made on pure and carbon-coated LiMnPO 4 nanorods, and their conductivities were evaluated by analyzing the measured impedance data using the WinFIT software. More than two orders of magnitude of conductivity enhancement was observed in the carbon-coated LiMnPO 4 nanorods compared to pure ones, and the conductivity enhancement may be attributed to the presence of carbon over LiMnPO 4 nanorods. Temperature dependence of conductivity and ac conductivity were calculated using impedance data of pure and carbon-coated LiMnPO 4 nanorods. CR2032 type lithium ion coin cells were fabricated using pure and carbon-coated LiMnPO 4 nanorods and characterized by measuring charge–discharge cycles between 2.9 and 4.5 V at room temperature. More than 25 % of improved capacity was achieved in the carbon-coated LiMnPO 4 nanorods when compared to pure ones synthesized using modified polyol and resin coating processes.