Appraisal of carbon-coated Li₄Ti₅O₁₂acanthospheres from optimized two-step hydrothermal synthesis as a superior anode for sodium-ion batteries

In this study, carbon-coated nanostructured Li₄Ti₅O₁₂acanthospheres with a highly porous and open structure, are prepared by a two-step hydrothermal synthesis, and are investigated as the anode for sodium-ion batteries (SIBs). The impact of the amount of glucose on the spinel-phase formation, the secondary morphological structure, carbon content and graphitization of the as-prepared C/Li₄Ti₅O₁₂microspheres is studied. Additionally, the subsequent electrode performance, including capacity, rate capability, and cycling stability, particularly at elevated temperatures, is emphasized. By optimizing the amount of the glucose organic carbon precursor, attractive capacities of 186 mAh g⁻¹at 0.2 C, 141 mAh g⁻¹at 2.0 C, and 68 mAh g⁻¹at 10 C are achieved for the as-synthesized C/Li₄Ti₅O₁₂, better than most reports on similar Li₄Ti₅O₁₂electrodes, suggesting the beneficial effect of morphology and carbon coating on the electrode performance. In addition, an outstanding cycling stability is demonstrated, with capacity retention of 93% after continuous cycling for 400 cycles at 1.0 C. At elevated temperatures, the important role of carbon in suppressing SEI formation and thus improving the cycling stability is highlighted. This suggests that the hierarchical carbon-modified Li₄Ti₅O₁₂acanthosphere from the optimized two-step hydrothermal synthesis is a promising anode material for SIBs with superior electrode performance.