Air-Stable Binary Hydrated Eutectic Electrolytes with Unique Solvation Structure for Rechargeable Aluminum-Ion Batteries

Pengyu Meng; Jian Huang; Zhaohui Yang; Min Jiang; Yibo Wang; Wei Zhang; Jiao Zhang; Baode Sun; Chaopeng Fu

doi:10.1007/s40820-023-01160-z

Air-Stable Binary Hydrated Eutectic Electrolytes with Unique Solvation Structure for Rechargeable Aluminum-Ion Batteries

Nanomicro Lett. 2023 Jul 29;15(1):188. doi: 10.1007/s40820-023-01160-z.

Authors

Pengyu Meng^#¹, Jian Huang^#², Zhaohui Yang¹, Min Jiang¹, Yibo Wang¹, Wei Zhang³, Jiao Zhang¹, Baode Sun¹, Chaopeng Fu⁴

Affiliations

¹ School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
² State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, People's Republic of China.
³ Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, Surrey, UK.
⁴ School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China. chaopengfu@sjtu.edu.cn.

^# Contributed equally.

Abstract

Aluminum-ion batteries (AIBs) have been highlighted as a potential alternative to lithium-ion batteries for large-scale energy storage due to the abundant reserve, light weight, low cost, and good safety of Al. However, the development of AIBs faces challenges due to the usage of AlCl₃-based ionic liquid electrolytes, which are expensive, corrosive, and sensitive to humidity. Here, we develop a low-cost, non-corrosive, and air-stable hydrated eutectic electrolyte composed of aluminum perchlorate nonahydrate and methylurea (MU) ligand. Through optimizing the molar ratio to achieve the unique solvation structure, the formed Al(ClO₄)₃·9H₂O/MU hydrated deep eutectic electrolyte (AMHEE) with an average coordination number of 2.4 can facilely realize stable and reversible deposition/stripping of Al. When combining with vanadium oxide nanorods positive electrode, the Al-ion full battery delivers a high discharge capacity of 320 mAh g^-1 with good capacity retention. The unique solvation structure with a low desolvation energy of the AMHEE enables Al³⁺ insertion/extraction during charge/discharge processes, which is evidenced by in situ synchrotron radiation X-ray diffraction. This work opens a new pathway of developing low-cost, safe, environmentally friendly and high-performance electrolytes for practical and sustainable AIBs.

Keywords: Al-ion battery; Hydrated eutectic electrolyte; Mechanism; Solvation structure.