A solution-to-solid conversion chemistry enables ultrafast-charging and long-lived molten salt aluminium batteries

• Published in: Nature communications 2023-07, Vol.14 (1), p.3909-3909, Article 3909
• Main Authors: Meng, Jiashen, Yao, Xuhui, Hong, Xufeng, Zhu, Lujun, Xiao, Zhitong, Jia, Yongfeng, Liu, Fang, Song, Huimin, Zhao, Yunlong, Pang, Quanquan
• Format: Article
• Language: English
• Subjects: 147/135; 147/137; 147/143; 639/301/299/161/891; 639/4077/4079/891; 639/638/161/891; Aluminum; Cathodes; Charging; Chemistry; Conversion; Cycles; Degradation; Electrolytes; Electrolytic cells; Humanities and Social Sciences; Kinetics; Molten salt electrolytes; Molten salts; multidisciplinary; Oxidation; Reaction kinetics; Rechargeable batteries; Redox properties; Salts; Science; Science (multidisciplinary); Stability
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-39258-y

Conventional solid-to-solid conversion-type cathodes in batteries suffer from poor diffusion/reaction kinetics, large volume changes and aggressive structural degradation, particularly for rechargeable aluminium batteries (RABs). Here we report a class of high-capacity redox couples featuring a solution-to-solid conversion chemistry with well-manipulated solubility as cathodes—uniquely allowed by using molten salt electrolytes—that enable fast-charging and long-lived RABs. As a proof-of-concept, we demonstrate a highly reversible redox couple—the highly soluble InCl and the sparingly soluble InCl 3 —that exhibits a high capacity of about 327 mAh g −1 with negligible cell overpotential of only 35 mV at 1 C rate and 150 °C. The cells show almost no capacity fade over 500 cycles at a 20 C charging rate and can sustain 100 mAh g −1 at 50 C. The fast oxidation kinetics of the solution phase upon initiating the charge enables the cell with ultrafast charging capability, whereas the structure self-healing via re-forming the solution phase at the end of discharge endows the long-term cycling stability. This solution-to-solid mechanism will unlock more multivalent battery cathodes that are attractive in cost but plagued by poor reaction kinetics and short cycle life. Conventional solid-to-solid conversion cathodes in rechargeable aluminium batteries suffer from sluggish reaction kinetics and cumulative structural degradation. Here the authors disclose a solution-to-solid conversion chemistry using molten salt electrolytes to achieve fast-charging capability and good cycling stability.