Na-storage reactions of rutile TiNbO4

• Published in: Electrochemistry communications 2023-10, Vol.155, p.107579, Article 107579
• Main Authors: Usui, Hiroyuki, Domi, Yasuhiro, Tanaka, Tomoyuki, Takemoto, Masataka, Oishi, Naoto, Nitta, Noriko, Sakaguchi, Hiroki
• Format: Article
• Language: English
• Subjects: Diffusion path size; Na-ion battery; Nb amount; Rutile structure; Sol-gel method; TiNbO4
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2023.107579

[Display omitted] •New anode materials are required for Na-ion battery of electric vehicle.•We discovered a new promising anode material, rutile-type TiNbO4.•Na-storage property could be clearly improved by increasing Nb amount.•Higher amount of Nb expand Na+ diffusion path size in TiNbO4. As a novel anode material for Na-ion battery, we evaluated rutile-type TiNbO4 synthesized by a sol−gel method. It was revealed for the first time that TiNbO4 showed reversible reactions of Na+-insertion and Na+-extraction in the potential ranges of 0.005–1.0 and 0.6–1.6 V vs. Na+/Na, respectively. TiNbO4 maintained its rutile structure even after charge−discharge cycling. The size of Na+ diffusion path along its c-axis was broadened with increasing Nb amount in TiNbO4, leading to the improvement in the reversible capacity. The TiNbO4 electrode with Nb 48 at.% exhibited a high capacity of 360 mA h g−1. The long-term cyclability and rate capability were also improved by increasing Nb amount. We consider that the wider space in the diffusion path increases the degree of freedom of Na+ occupancy position, which weakens the electrostatic repulsion between Na+ and Na+ to increase Na storage capacity. These results clearly demonstrate that TiNbO4 can be applied as a promising anode material.