Hydrogenated core-shell MAX@K2Ti8O17 pseudocapacitance with ultrafast sodium storage and long-term cycling.

Zou, Guodong; Guo, Jianxin; Liu, Xianyu; Zhang, Qingrui; Huang, Gang; Fernandez, Carlos; Peng, Qiuming

Abstract

Sodium-ion batteries are considered alternatives to lithium-ion batteries for energy storage devices due to their competitive cost and source abundance. However, the development of electrode materials with long-term stability and high capacity remains a great challenge. Here, this paper describes for the first time the synthesis of a new class of core-shell MAX@K2Ti8O17 by alkaline hydrothermal reaction and hydrogenation of MAX, which grants high sodium ion-intercalation pseudocapacitance. This composite electrode displays extraordinary reversible capacities of 190 mA h g-1 at 200 mA g-1 (0.9 C, theoretical value of ~219 mA h g-1) and 150 mA h g-1 at 1000 mA g-1 (4.6 C). More importantly, a reversible capacity of 75 mA h g-1 at 10 000 mA g-1 (46 C) is retained without any apparent capacity decay even after more than 10 000 cycles. Experimental tests and first-principle calculations confirm that the increase in Ti3+ on the surface layers of MAX@K2Ti8O17 by hydrogenation increases its conductivity in addition to enhancing the sodium-ion intercalation pseudocapacitive process. Furthermore, the distorted dodecahedrons between Ti and O layers not only provide abundant sites for sodium-ion accommodation but also act as wide tunnels for sodium-ion transport.

Citation

ZOU, G., GUO, J., LIU, X., ZHANG, Q., HUANG, G., FERNANDEZ, C. and PENG, Q. 2017. Hydrogenated core-shell MAX@K2Ti8O17 pseudocapacitance with ultrafast sodium storage and long-term cycling. Advanced energy materials [online], 7(18), article number 1700700. Available from: https://doi.org/10.1002/aenm.201700700

• Journal Article Type: Article
• Acceptance Date: May 22, 2017
• Online Publication Date: May 22, 2017
• Publication Date: Sep 20, 2017
• Publicly Available Date: Oct 22, 2019
• Journal: Advanced energy materials
• Print ISSN: 1614-6832
• Electronic ISSN: 1614-6840
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 18
• Article Number: 1700700
• DOI: https://doi.org/10.1002/aenm.201700700
• Keywords: Electrode; Hydrogenation treatment; MAX@K2Ti8O17 composite; Sodium batteries
• Public URL: https://rgu-repository.worktribe.com/output/247444