Hierarchical hollow microspheres assembled from N-doped carbon coated Li4Ti5O12 nanosheets with enhanced lithium storage properties†
Hierarchical hollow microspheres composed of N-doped carbon coated Li4Ti5O12 nanosheets (NC-LTO) have been synthesized on a large scale by a facile low-temperature solution-based approach combined with high temperature calcination. The primary Li4Ti5O12 nanosheets show zigzag morphology with a typical thickness of about 5.0 nm, which are uniformly coated with N-doped carbon layers. When evaluated for lithium storage capacity, the NC-LTO hollow microspheres display enhanced electrochemical energy storage performances compared to the pristine hollow microspheres composed of Li4Ti5O12 nanosheets (A-LTO), including high capacity (181.4 mA h g−1 at 0.5 C), excellent rate capability (140.8 mA h g−1 at 20 C), and good cyclic stability (92.8% capacity loss after 100 cycles at 20 C). The reasons for these improvements are explored in terms of the increased electronic conductivity and the facilitation of lithium ion transport arising from the introduction of N-doped carbon layers and the thin zigzag Li4Ti5O12 nanosheets.