Direct synthesis of carbon-coated Li4Ti5O12 mesoporous nanoparticles for high-rate lithium-ion batteries

Abstract

The carbon-coated Li₄Ti₅O₁₂ mesoporous nanoparticles were directly synthesized by a facile solvothermal method with a subsequent N₂ treatment. The resultant Li₄Ti₅O₁₂ did not show any by-products of TiN or TiC, but a unique mesoporous structure and particle dimension of about 20 nm. Confined to the surface thin layer <5 nm of this mesoporous structure was carbon species, which amounts to 0.98 wt%, much less than that when using conventional carbon-coating method. Systematic electrochemical tests on these mesoporous nanoparticles demonstrated an excellent cycling performance with Coulombic efficiencies being all higher than 99% after the initial cycle. Further, when cycled at a high rate of 10 C, these mesoporous nanoparticles delivered an initial discharge capacity of 137 mAh g⁻¹ and maintained a high reversible capacity of 107 mAh g⁻¹ after 1600 cycles, which is apparently much higher than that of 67 mAh g⁻¹ for the first discharge capacity of non-mesoporous Li₄Ti₅O₁₂. The improved electrochemical performances of Li₄Ti₅O₁₂ can be attributed to the mesoporous structure and thin carbon coating on Li₄Ti₅O₁₂ nanoparticles, which facilitates electron and lithium-ion diffusion.