Carbothermal reduction synthesis of carbon coated Na2FePO4F for lithium ion batteries

Carbon coated spherical Na2FePO4F particles with typical diameters from 500 nm to 1 mu m have been synthesized through an economical carbothermal reduction method with a simple apparatus. Mixed carbon source consists of citric acid and phenolic resin can form highly graphitized carbon and remarkably improve the electrical conductivity. When cycled against lithium, Na2FePO4F/C cathodes deliver maximum discharge capacity of 119 mAh g(-1) at a low rate of 0.05 C. Reversible capacity of 110 mAh g(-1), 74 mAh g(-1) and 52 mAh g(-1) can be obtained at 0.1 C, 1 C and 2 C rates, respectively. And after 30 cycles at 0.1 C, 91% of the discharge capacity can still be maintained. The electrochemical kinetic characteristic of electrode material is investigated by EIS and the apparent Li+ diffusion coefficient in the Li/Na2FePO4F system is evaluated to be as high as 1.152 x 10(-11) cm(2) s(-1). This study demonstrates that the practical and economical synthesis process can be a promising way for industrial production of high performance Na2FePO4F/C electrode material for large-scale lithium ion batteries. (C) 2015 Elsevier B.V. All rights reserved.