Effect of different carbon sources on the electrochemical properties of rod-like LiMnPO4–C nanocomposites

Abstract

Olivine structured LiMnPO₄ nanorods as an emerging cathode material for lithium ion batteries have recently triggered intensive interest. Herein, LiMnPO₄ nanorods have been synthesized via a solvothermal route and then coated with a carbon layer from different carbon sources to improve their electrochemical performance. The LiMnPO₄–C nanocomposite obtained from beta-cyclodextrin as the carbon source showed a reversible capacity of 153.4 mA h g⁻¹ at a rate of 0.1 C and maintained it at 120 mA h g⁻¹ after 50 cycles, which is much better than that obtained from ascorbic acid, citric acid, glucose and sucrose. This result can be attributed to the smaller electrode impedance in the nanocomposite obtained from beta-cyclodextrin, based on EIS measurements. Correlated to the molecule structure, it is believed that larger molecules with more oxygenous groups are beneficial to their uniform adsorption on the electrodes and then produce a better electron-conductive carbon layer after calcinations. This result would be very helpful in future work related to carbon coating on other electrodes.