Three-Dimensional Fast Na-Ion Transport in Sodium Titanate Nanoarchitectures via Engineering of Oxygen Vacancies and Bismuth Substitution

Jun Mei; Tiantian Wang; Dongchen Qi; Jianjun Liu; Ting Liao; Yusuke Yamauchi; Ziqi Sun

doi:10.1021/acsnano.1c04479

Three-Dimensional Fast Na-Ion Transport in Sodium Titanate Nanoarchitectures via Engineering of Oxygen Vacancies and Bismuth Substitution

ACS Nano. 2021 Aug 24;15(8):13604-13615. doi: 10.1021/acsnano.1c04479. Epub 2021 Aug 6.

Authors

Jun Mei^{1

2}, Tiantian Wang^{3

4

5}, Dongchen Qi^{1

2}, Jianjun Liu⁴, Ting Liao^{1

3}, Yusuke Yamauchi^{6

7}, Ziqi Sun^{1

2}

Affiliations

¹ Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia.
² School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia.
³ School of Mechanical, Medical and Process Engineering, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia.
⁴ State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China.
⁵ University of Chinese Academy of Sciences, Beijing 100049, China.
⁶ Australian Institute for Bioengineering and Nanotechnology and School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia.
⁷ JST-ERATO Yamauchi Materials Space-Tectonics and International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.

PMID: 34355881
DOI: 10.1021/acsnano.1c04479

Abstract

Layered sodium titanates (NTO), one of the most promising anode materials for advanced sodium-ion batteries (SIBs), feature high theoretical capacity and no serious safety concerns. The pristine NTO electrode, however, has unfavorable Na⁺ transport kinetics, due to the dominant two-dimensional (2D) Na-ion transport channels within the crystal along the low energy barrier octahedron layers, which impedes the practical application of this class of potential materials. Herein, an interesting concept of opening three-dimensional (3D) fast ion transport channels within the intrinsic NTO frameworks is proposed to enhance the electrochemical performance through a combination of oxygen vacancy generation and cation substitution strategies, by which the interlayer spacing of the NTO frameworks is expanded for fast 3D Na-ion transport. It is evidenced that the oxygen-deficient and bismuth-substituted HBNTO (Bi_xNa_2-xTi₃O_y, 0 < x < 2, 0 < y < 7, HBNTO) exhibits obvious enhancements on the reversible capacity (∼145% enhancement at 20 mAh g^-1 compared with NTO), the rate capability (∼200% enhancement at 500 mAh g^-1 compared with NTO), and the cycling stability (∼210% enhancement of retention capacity after 150 cycles at 20 mAh g^-1 compared with NTO). The molecular dynamic simulations and theoretical calculations demonstrate that the enhanced performance of HBNTO is contributed by the multiplied sodium diffusion pathways and the increased ion migration rates with the successful opening of 3D internal ion transport channels. This work demonstrates the effectiveness of the strategies in opening the 3D intercrystal ion transport channels for boosting the electrochemical performance of SIBs.

Keywords: bismuth; cation substitution; ion transport; sodium titanate; sodium-ion batteries; vacancy.