Tunnel-Structured KxTiO2Nanorods by in Situ Carbothermal Reduction as a Long Cycle and High Rate Anode for Sodium-Ion Batteries.
The low electronic conductivity and the sluggish sodium-ion diffusion in the compact crystal structure of Ti-based anodes seriously restrict their development in sodium-ion batteries. In this study, a new hollandite KxTiO2with large (2 × 2) tunnels is synthesized by a facile carbothermal reduction method, and its sodium storage performance is investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses illustrate the formation mechanism of the hollandite KxTiO2upon the carbothermal reduction process. Compared to the traditional layered or small (1 × 1) tunnel-type Ti-based materials, the hollandite KxTiO2with large (2 × 2) tunnels may accommodate more sodium ions and facilitate the Na+diffusion in the structure; thus, it is expected to get a large capacity and realize high rate capability. The synthesized KxTiO2with large (2 × 2) tunnels shows a stable reversible capacity of 131 mAh g-1(nearly 3 times of (1 × 1) tunnel-structured Na2Ti6O13) and superior cycling stability with no obvious capacity decay even after 1000 cycles, which is significantly better than the traditional layered Na2Ti3O7(only 40% of capacity retention in 20 cycles). Moreover, the carbothermal process can naturally introduce oxygen vacancy and low-valent titanium as well as the surface carbon coating layer to the structure, which would greatly enhance the electronic conductivity of KxTiO2and thus endow this material high rate capability. With a good rate capability and long cyclability, this hollandite KxTiO2can serve as a new promising anode material for room-temperature long-life sodium-ion batteries for large-scale energy storage systems, and the carbothermal reduction method is believed to be an effective and facile way to develop novel Ti-based anodes with simultaneous carbon coating and Ti(III) self-doping.
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Qing
Q
Zhang
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Yaqing
Y
Wei
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Haotian
H
Yang
Brookhaven National Laboratory , Upton, New York 11973, United States.
Dong
http://orcid.org/0000-0002-1921-6683
D
Su
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Ying
Y
Ma
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Huiqiao
http://orcid.org/0000-0001-8114-2542
H
Li
State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST) , Wuhan, Hubei 430074, P. R. China.
Tianyou
http://orcid.org/0000-0003-0985-4806
T
Zhai
anode; carbothermal reduction; high rate; hollandite; long cycle; sodium-ion batteries; tunnel structure