Nanostructured 0.8Li2FeSiO4/0.4Li2SiO3/C composite cathode material with enhanced electrochemical performance for lithium-ion batteries

A strategy is proposed and developed to promote Li+ diffusion in polyanion cathode materials such as 0.8Li(2)FeSiO(4)/0.4Li(2)SiO(3)/C with the incorporation of Li2SiO3 as a lithium ionic conductive matrix. It is shown that the presence of Li2SiO3 separates the Li2FeSiO4 particles into small domains of a few nanometres and provides a fast Li+ diffusion channel, thus effectively enhancing Li+ diffusion in the 0.8Li(2)FeSiO(4)/0.4Li(2)SiO(3)/C composite. As a result, the composite material shows enhanced electrochemical performance and delivers a capacity as high as 240 mA h g(-1) (corresponding to 1.44 electrons exchange per active Li2FeSiO4 formula unit) with good cyclic stability at 30 degrees C. The XRD and FTIR results indicate that the Li2SiO3 component exists in an amorphous phase. SEM and TEM analyses show an aggregate structure consisting of primary nanocrystallites (about tens of nanometres in diameter). The primary particles consist of a crystal Li2FeSiO4 phase and an amorphous Li2SiO3 and C, and a nanocrystalline Li2FeSiO4 surrounded by amorphous Li2SiO3 and C which are well known as a lithium ion conductor and electron conductor. The smaller nanoparticles of Li2FeSiO4 and the presence of lithium ionic and electronic conducting amorphous Li2SiO3 and carbon matrix both contributed to the enhanced electrochemical performance of the composite.