Gel-combustion synthesis of LiFePO<inf>4</inf>/C composite with improved capacity retention in aerated aqueous electrolyte solution

Abstract

The LiFePO4/C composite containing 13.4 wt.% of carbon was synthesized by combustion of a metal salt-(glycine + malonic acid) gel, followed by an isothermal heat-treatment of combustion product at 750 °C in reducing atmosphere. By a brief test in 1 M LiClO4-propylene carbonate solution at a rate of C/10, the discharge capacity was proven to be equal to the theoretical one. In aqueous LiNO3 solution equilibrated with air, at a rate C/3, initial discharge capacity of 106 mAh g-1 was measured, being among the highest ones observed for various Li-ion intercalation materials in aqueous solutions. In addition, significant prolongation of cycle life was achieved, illustrated by the fact that upon 120 charging/discharging cycles at various rates, the capacity remained as high as 80% of initial value. The chemical diffusion coefficient of lithium in this composite was measured by cyclic voltammetry. The obtained values were compared to the existing literature data, and the reasons of high scatter of reported values were considered. © 2013 Elsevier Ltd.