Abstract
A novel complementary approach for promising anode materials is proposed. Sodium titanates with layered Na2Ti3O7 and tunnel Na2Ti6O13 hybrid structure are presented, fabricated, and characterized. The hybrid sample exhibits excellent cycling stability and superior rate performance by the inhibition of layered phase transformation and synergetic effect. The structural evolution, reaction mechanism, and reaction dynamics of hybrid electrodes during the sodium insertion/desertion process are carefully investigated. In situ synchrotron X‐ray powder diffraction (SXRD) characterization is performed and the result indicates that Na+ inserts into tunnel structure with occurring solid solution reaction and intercalates into Na2Ti3O7 structure with appearing a phase transition in a low voltage. The reaction dynamics reveals that sodium ion diffusion of tunnel Na2Ti6O13 is faster than that of layered Na2Ti3O7. The synergetic complementary properties are significantly conductive to enhance electrochemical behavior of hybrid structure. This study provides a promising candidate anode for advanced sodium ion batteries (SIBs).
Highlights
In situ X-ray diffraction (XRD) analysis demonstrated that the solid solution reaction occurred in tunnel Na2Ti6O13 component and phase transition appeared in the layered Na2Ti3O7 structure
The Na2Ti3O7 and tunnel Na2Ti6O13 hybrid material (NNTO) electrodes exhibited an excellent stability at a high current density due to the less amount of Na+ insertion in the layered Na2Ti3O7, which resulted in a small volume effect
It was worth noticing that synchrotron X-ray powder diffraction (SXRD) characteristic peak located at 8.8° was splitting into two different peaks at the discharge state, which were incorporated again into one peak at the charge state (Figure S8, Supporting Information)
Summary
In situ X-ray diffraction (XRD) analysis demonstrated that the solid solution reaction occurred in tunnel Na2Ti6O13 component and phase transition appeared in the layered Na2Ti3O7 structure. As compared to the electrochemical performance of single Na2Ti3O7 and Na2Ti6O13 phase (Figure S5, Supporting Information), the hybrid structures showed the excellent cycling performance and a high capacity.
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