Understanding the Molecular Structure of the Elastic and Thermoreversible AlCl3 : Urea/Polyethylene Oxide Gel Electrolyte

• Published in: ChemSusChem Vol. 13; no. 20; pp. 5523 - 5530
• Main Authors: Miguel, Álvaro, Fornari, Rocco Peter, García, Nuria, Bhowmik, Arghya, Carrasco‐Busturia, David, García‐Lastra, Juan Maria, Tiemblo, Pilar
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 21.10.2020
• Subjects: ab initio calculations; Aluminum; Aluminum chloride; aluminum secondary batteryenergy storage; Elastomers; Electroactivity; Electrolytes; Gels; ionic liquids; Molecular structure; Polyethylene; Polyethylene oxide; polymer gel electrolytes; Rheological properties; Rheology; Speciation; Ureas; Vibrational spectra
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202001557

It is possible to prepare elastic and thermoreversible gel electrolytes with significant electroactivity by dissolving minimal weight fractions of ultra‐high molecular weight polyethylene oxide (UHMW PEO) in an aluminum deep eutectic solvent (DES) electrolyte composed of AlCl3 and urea at a molar ratio of 1.5 : 1 (AlCl3/urea). The experimental vibrational spectra (FTIR and Raman) provide valuable information on the structure and composition of the gel electrolyte. However, the complexity of this system requires computational simulations to help interpretation of the experimental results. This combined approach allows us to elucidate the speciation of the DES liquid electrolyte in the gel and how it interacts with the polymer chains to give rise to an elastic network that retains the electroactivity of the liquid electrolyte to a very great extent. The observed reactions occur between the ether in the polymer and both the amine groups in urea and the aluminum species. Thus, similar elastomeric gels may likely be prepared with other aluminum liquid electrolytes, making this procedure an effective way to produce families of gel aluminum electrolytes with tunable rheology and electroactivity. Al sticks forever: Aluminum chloride and urea can form a deep eutectic solvent (DES) electrolyte for aluminum batteries. Adding polyethylene oxide (PEO) polymer turns the DES into a sticky and elastic gel, which improves the battery's safety while retaining its electrochemical performance. The excellent mechanical properties are due to bonds formed between the PEO and the components of the DES, which can act as crosslinkers and contribute to the elastomeric character of the gel.