Heterogeneous Ti3SiC2@C-Containing Na2Ti7O15 Architecture for High-Performance Sodium Storage at Elevated Temperatures.

Rational design of heterogeneous electrode materials with hierarchical architecture is a potential approach to significantly improve their energy densities. Herein, we report a tailored microwave-assisted synthetic strategy to create heterogeneous hierarchical Ti3SiC2@C-containing Na2Ti7O15 (MAX@C-NTO) composites as potential anode materials for high-performance sodium storage in a wide temperature range from 25 to 80 °C. This composite delivers first reversible capacities of 230 mAh g-1 at 200 mA g-1 and 149 mAh g-1 at 3000 mA g-1 at 25 °C. A high capacity of ∼93 mAh g-1 without any apparent decay even after more than 10 000 cycles is obtained at an ultrahigh current density of 10 000 mA g-1. Moreover, both a high reversible capacity and an ultralong durable stability are achieved below 60 °C for the same composites, wherein a 75.2% capacity retention (∼120 mAh g-1 at 10 000 mA g-1) is achieved after 3000 cycles at 60 °C. To the best of our knowledge, both the sodium storage performances and the temperature tolerances outperform those of all the Ti-based sodium storage materials reported so far. The superior sodium storage performances of the as-synthesized composites are attributed to the heterogeneous core-shell architecture, which not only provides fast kinetics by high pseudocapacitance but also prolongs cycling life by preventing particle agglomeration and facilitates the transportation of electrons and sodium ions by large micro/mesopore structure.