Rationally fabricating nitrogen-doped carbon coated nanocrystalline Li2FeSiO4@N-C with excellent Li-ion battery performances

Nitrogen-doped carbon coated nanocrystalline Li2FeSiO4@N-C cathode materials are rationally synthesized via tartaric acid assisted sol-gel method by using urea as the nitrogen source. The addition of urea not only successfully dopes N into the carbon coating but also decreases the average particle size by heat induced ammonium molecular releasing that affects the agglomeration process of the precursor sol. The optimized sample of Li2FeSiO4@N-C1 is composed of uniformly distributed Li2FeSiO4 nanocrystals with a diameter of ∼10 nm coating by N-doped carbon layer (about 1 nm). N-doping on the carbon layer significantly increases the electronic conductivity of Li2FeSiO4, and results in ultrahigh rate performance and excellent cycling stability for lithium storage. Li2FeSiO4@N-C1 delivers a high capacity of 246.1 mAhg−1 at 0.1 C that corresponds to reversible 1.48 Li+ storage capacity. Charge/discharge cycling at 0.5 C shows a steady capacity of 220 mAhg−1 without obvious capacity fading within 100 cycles. Thus, we believe that the nirogen-doped carbon coated nanocrystalline-Li2FeSiO4@N-C composites, possessing high-capacity and excellent cyclic performance, is a promising next-generation cathode material for high-power lithium-ion batteries.