Surface-redox sodium-ion storage in anatase titanium oxide

Qiulong Wei; Xiaoqing Chang; Danielle Butts; Ryan DeBlock; Kun Lan; Junbin Li; Dongliang Chao; Dong-Liang Peng; Bruce Dunn

doi:10.1038/s41467-022-35617-3

Surface-redox sodium-ion storage in anatase titanium oxide

Nat Commun. 2023 Jan 3;14(1):7. doi: 10.1038/s41467-022-35617-3.

Authors

Qiulong Wei^{1

2}, Xiaoqing Chang³, Danielle Butts⁴, Ryan DeBlock⁴, Kun Lan^{5

6}, Junbin Li³, Dongliang Chao⁵, Dong-Liang Peng^{3

7}, Bruce Dunn⁸

Affiliations

¹ Department of Materials Science and Engineering, Fujian Key Laboratory of Surface and Interface Engineering for High Performance Materials, Xiamen Key Laboratory of High Performance Metals and Materials, College of Materials, Xiamen University, Xiamen, 361005, PR China. qlwei@xmu.edu.cn.
² Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, 361005, PR China. qlwei@xmu.edu.cn.
³ Department of Materials Science and Engineering, Fujian Key Laboratory of Surface and Interface Engineering for High Performance Materials, Xiamen Key Laboratory of High Performance Metals and Materials, College of Materials, Xiamen University, Xiamen, 361005, PR China.
⁴ Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA.
⁵ Laboratory of Advanced Materials, Department of Chemistry, State Key Laboratory of Molecular Engineering of Polymers, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Fudan University, Shanghai, 200433, PR China.
⁶ College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010070, PR China.
⁷ Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, 361005, PR China.
⁸ Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA, 90095, USA. bdunn@ucla.edu.

Abstract

Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO₂(A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO₂(A) becomes amorphous but still undergoes Ti⁴⁺/Ti³⁺ redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO₂(A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g^-1, at high charge/discharge rates. Kinetic studies of TiO₂(A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO₂(A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO₂(A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO₂(A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.

Abstract

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