Synthesis and characterization of in situ carbon-coated Li2FeSiO4 cathode materials for lithium ion battery

Li2FeSiO4/C composites with in situ carbon coating were synthesized via sol–gel method based on acid-catalyzed hydrolysis/condensation of tetraethoxysilane (TEOS) with sucrose and l-ascorbic acid as carbon additives, respectively. As-obtained Li2FeSiO4/C composites prepared with l-ascorbic acid as a carbon additive are composed of nanoparticulate Li2FeSiO4 in an intimate contact with a continuous thin layer of residual carbon and exhibit large specific surface area up to 395.7 m2 g−1. The results indicate that structure of the residual carbon is graphene-rich with obviously lower disordered/graphene (D/G) ratio. These as-obtained Li2FeSiO4/C composites exhibit first discharge capacity of 135.3 mAh g−1 at C/16 and perform cycling stability, which are superior to those of Li2FeSiO4/C composites synthesized with sucrose as a carbon additive.

► Sucrose and l-ascorbic acid as carbon additives. ► Li2FeSiO4/C were obtained under our carbon coating experimental conditions. ► Graphite-rich carbon was formed uniformly when ascorbic acid was employed. ► The composites employing l-ascorbic acid exhibited a large specific surface area. ► Sample using l-ascorbic acid exhibited better rate performance and cycling stability.