Synthesis and electrochemical characterizations of nano-crystalline LiFePO4 and Mg-doped LiFePO4 cathode materials for rechargeable lithium-ion batteries

Abstract

Nano-crystalline LiFePO4 and LiMg0.05Fe0.95PO4 cathode materials were synthesized by sol–gel method in argon atmosphere using succinic acid as a chelating agent. Physico-chemical characterizations were done by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and Raman spectroscopy. Electrochemical behavior of the cathode materials were analyzed using cyclic voltammetry, and galvanostatic charge/discharge cycling studies were employed to characterize the reaction of lithium-ion insertion into and extraction from virginal and magnesium-doped LiFePO4, in the voltage range 2.5 to 4.5 V (Vs Li/Li+) using 1 M LiPF6 with 1:1 ratio of ethylene carbonate and dimethyl carbonate as electrolytes. LiMg0.05Fe0.95PO4 exhibits initial charge and discharge capacities of 159 and 141 mAh/g at 0.2 C rate respectively, as compared to 121 and 107 mAh/g of pristine LiFePO4. Furthermore, LiMg0.05Fe0.95PO4 has retained more than 89% of the capacity even after 60 cycles. Hence, LiMg0.05Fe0.95PO4 is a promising cathode material for rechargeable lithium-ion batteries.