Trace Fe3+ mediated synthesis of LiFePO4 micro/nanostructures towards improved electrochemical performance for lithium-ion batteries

Abstract

Various LiFePO₄ micro/nanostructures have been solvothermally synthesized using FeSO₄ and ethylene glycol (EG) as the reactant and reaction medium, respectively. The LiFePO₄ micro/nanostructures including nanoflakes, stacked microsheets, micro-dumbbells and micro-spindles have been selectively fabricated and tuned via adjusting trace Fe³⁺ obtained from oxidation of the reactant. The content of mediated-Fe³⁺ in the EG system plays an important role in the formation of the micro/nanostructures as well as the change in the pH value. In this work, the content of mediated-Fe³⁺ in the precursor solution as a problem worthy of attention was put forward and the evolution process of the LiFePO₄ micro/nanostructures has been extensively studied. Among these micro/nanostructures of LiFePO₄, the LiFePO₄ micro-dumbbells as a cathode material for lithium-ion batteries showed the most excellent electrochemical performance with a discharge capacity of 117 mA h g⁻¹ at a high rate of 10C (1C = 169 mA h g⁻¹), which demonstrates that the exposed crystal plane and morphology of LiFePO₄ play critical roles in the electrochemical performance. This work not only provides deeper knowledge into the formation mechanism of LiFePO₄ microstructures, but also paves a facile way to prepare scalable LiFePO₄ with a high rate performance and high tap density.