Synthesis and electrochemical performance of spherical-like Li2FeSiO4/C/SP cathode material for lithium-ion batteries

• The spherical Li2FeSiO4/C/SP was prepared by two-step precipitation method.
• The growth mechanism of spherical Li2FeSiO4/C was discussed.
• The spherical Li2FeSiO4/C/SP was improved the lithium ion diffusion coefficient.
• The Li2FeSiO4/C composites presented excellent rate performance and cycling stability.

The novel spherical Li2FeSiO4/C/SP is successfully synthesized by two-step precipitation method. The structure and morphology of the as-prepared samples are characterized by means of XRD, SEM, TEM and HRTEM. The results show that the product is consisted of spherical Li2FeSiO4 microparticles coated with carbon layer and dispersive nanoparticle which is conductive carbon black. The growth mechanism of the spherical Li2FeSiO4/C/SP composites is discussed in particularly. The electrochemical performance is demonstrated by the electrochemical impedance spectra and charge–discharge curves. The product presents excellent electrochemical performance. This is the result of the uniform spherical morphology improved lithium-ion diffusion rate (1.271 × 10−12 cm2 s−1) by shortening diffusion pathways of lithium ion, and the carbon coating enhance the electronic conductivity. It is found that the spherical Li2FeSiO4/C/SP composites show a high capacity as 171.8 mA h g−1 at 0.1 C and high coulombic efficiency as 93.6%. The outstanding high-rate capability is also presented as 113.7 mA h g−1 at 5 C. Moreover, it exhibits very stable discharge specific capacity at different current densities from 0.2 to 5 C. These indicate that the spherical Li2FeSiO4/C/SP is a very promising candidate for cathode material in lithium-ion batteries.