Sol-Gel Synthesis of Nanostructured Li2FeSiO4/C as Cathode Material for Lithium Ion Battery

Abstract

Nanostructured Li2FeSiO4/C composites have been successfully synthesized by adopting polyethylene glycol (PEG) as the surfactant and L-ascorbic acid as the carbon additive, using a sol-gel method based on the acid-catalyzed hydrolysis/condensation of tetraethoxysilane (TEOS). The Li2FeSiO4/C nanocomposites possess dispersed spherical particles (∼50 nm) with narrow particle size distribution, embedded in a continuous carbon matrix. The Li2FeSiO4/C nanocomposites deliver first discharge capacity of 138.2 mAhg−1 at C/16 and maintain at about 130.4 mAhg−1 after 40 cycles at various rates at room temperature, which outperform those of Li2FeSiO4/C samples synthesized without PEG. The electrochemical performances of Li2FeSiO4/C were largely enhanced after the introduction of PEG due to the following two aspects. On one hand, the smaller particle size facilitated the shorter diffusion length for lithium ions; On the other hand, the more continuous carbon film coated on the particle surface enhanced the electronic conductivity of the nanocomposites and restrained the side reaction occurring at the electrode-electrolyte interface.