In Operando Investigation of the Structural Evolution during Calcination and Corresponding Enhanced Performance of Three-Dimensional Na₂Ti₆O₁₃@C–N Hierarchical Microflowers

Three-dimensional (3D) Na2Ti6O13 microflowers assembled from directionally arranged and closely interlinked one-dimensional N-doped carbon Na2Ti6O13 nanorods have been successfully prepared by a self-sacrificed template method followed by sintering in argon. In situ high-temperature X-ray powder diffraction (XRD) characterization was conducted to explore the phase transformation and structural evolution. The results indicated that the NaTi3O6(OH)·2H2O precursor was converted into the tunnel Na2Ti6O13 phase and the layered Na2Ti3O7 phase at the different temperatures. At a certain temperature, the tunnel and layered phases have a mutual transformation. The higher temperature was not conductive to the formation of pure phases. The crystal structural evolution has been given based on the synthesis process and in situ high temperature XRD patterns. When served as anode for SIBs, a capacity of ca. 30 mAh g–1 over 6000 continuous cycles was retained at 2000 mA g–1. Moreover, the structural and morphology integrity, reaction mechanism and pseudocapacitance behavior were also investigated