Redox potential regulation toward suppressing hydrogen evolution in aqueous sodium-ion batteries: NaTiFe(PO)

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 7; no. 43; pp. 24953 - 24963
• Main Authors: Qiu, Yuegang, Yu, Yonghui, Xu, Jia, Liu, Yi, Ou, Mingyang, Sun, Shixiong, Wei, Peng, Deng, Zhi, Xu, Yue, Fang, Chun, Li, Qing, Han, Jiantao, Huang, Yunhui
• Format: Journal Article
• Language: English
• Published: 05.11.2019
• DOI: 10.1039/c9ta08829f
• ISSN: 2050-7488

Aqueous sodium-ion batteries (ASIBs) show superior characteristics with high safety and low cost for large scale energy storage systems. However, easily occurring hydrogen evolution at a negative potential is a huge barrier to the application of anode materials in ASIBs. Even the most promising insert-type anode material, NaTi 2 (PO 4 ) 3 (NTP), cannot be commercialized due to its inadequate operating potential (−0.807 V vs. Ag/AgCl) that is close to the hydrogen evolution potential (−0.817 V vs. Ag/AgCl). Here, we report a redox potential regulation strategy to overcome this technical problem by integrating the redox couples of Ti 4+ /Ti 3+ and Fe 3+ /Fe 2+ to yield Na 1.5 Ti 1.5 Fe 0.5 (PO 4 ) 3 (NTFP) and increasing its operating potential up to −0.721 V vs. Ag/AgCl, which effectively prevents the potential overlap with the reductive decomposition of H 2 O. Importantly, the excellent electrochemical properties and low energy consuming synthetic route to NTFP open a new perspective to energetically develop low cost and highly stable ASIBs as a large-scale energy storage tool. The redox potential regulation strategy effectively prevented the potential overlap between sodiation and hydrogen evolution in the charging process.