Synthesis and electrochemical performance of Li2FeSiO4/C/carbon nanosphere composite cathode materials for lithium ion batteries

Highlights: •The Li2FeSiO4/C/CNS was prepared by effective double-carbon composite route. •The CNS as the conductivity belt connects the Li2FeSiO4/C particles. •The samples have a high capacity and excellent cyclic and rate performance. -- Abstract: Li2FeSiO4/C/carbon nanosphere (CNS) composites as cathode materials for lithium-ion batteries were synthesized by a simple hydro-chemical method. The double-carbon structural design of glucose pyrolysis-carbon (C) and CNS improved electrochemical performance of the composite where the CNS can build conductivity belts to connect the Li2FeSiO4/C particles and to favor electronic transmission. The exchange current density and the diffusion coefficient of lithium ions with the composite were 0.208 mA cm−2 and 1.06E−11 cm2 S−1, respectively, which were much larger than that of conventional Li2FeSiO4/C composite cathode materials (i = 0.131 mA cm−2, DLi = 4.69E−12 cm2 S−1). The electrochemical test results showed that the discharge capacity of 164.7 mA h g−1 could be obtained, and especially, after 60 cycles, 98.4% of the initial discharge capacity remained at 0.1 C of galvanostatic discharge in the potential range of 1.5–4.8 V (vs. Li/Li+). In addition, the discharge capacity of 92.4 mA h g−1 at 5 C was easily recovered to 159.8 mA h g−1 at 0.1 C