Two for one: propylene carbonate co-solvent for high performance aqueous zinc-ion batteries - remedies for persistent issues at both electrodes

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 1; no. 23; pp. 12597 - 1267
• Main Authors: Kakoty, Bhaskar, Vengarathody, Rishikesh, Mukherji, Srimayee, Ahuja, Vinita, Joseph, Anjana, Narayana, Chandrabhas, Balasubramanian, Sundaram, Senguttuvan, Premkumar
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 14.06.2022
• Subjects: Additives; Anions; Batteries; Carbonyl compounds; Carbonyls; Cathodes; Cathodic dissolution; Dendritic structure; Dissolution; Electrical conductivity; Electrical resistivity; Electrolytes; Electrolytic cells; Energy storage; Molecular dynamics; Propylene; Rechargeable batteries; Solvents; Storage batteries; Vanadium pentoxide; Water chemistry; Zinc; Zinc fluorides; Zinc plating
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d2ta01501c

Aqueous rechargeable zinc-ion batteries are attractive for large-scale energy storage applications. However, challenges such as the dendritic growth of zinc, structural degradation and dissolution of oxide cathodes, and poor coulombic efficiencies (CEs) limit their scope. While organic co-solvents and additives in low concentration Zn 2+ -ion electrolytes have had some success in redressing these issues, their efficacy is tempered by them being required in large amounts which reduces key electrolyte features such as electrical conductivity. Herein, we report a significant enhancement in battery characteristics upon the introduction of the highly polar propylene carbonate (PC) which imparts its dual-functionality - it suppresses water-derived parasitic reactions occurring at both the Zn anode and the V 2 O 5 cathode. Upon a small addition of PC (≤20 wt%) in 1 M zinc triflate electrolyte, water molecules solvating Zn 2+ -ions are shown to be partly replaced by the carbonate and the triflate anions, as evidenced by spectroscopic and molecular dynamics simulation studies. Subsequently, the PC and triflate anion get electrochemically reduced to form a ZnF 2 -rich solid-electrolyte interphase, resulting in a stable zinc plating/stripping process in Zn|Cu cells for 700 cycles with CEs of ∼99.3%. The highly basic carbonyl oxygen of PC is shown to strongly interact with water molecules, which in turn suppresses the dissolution of the cathode, enabling exceptional capacities of ∼300 mA h g −1 over 900 cycles at 1 A g −1 . We find that the addition of PC co-solvent suppresses parasitic reactions at both electrodes, and improves the cycling stability and coulombic efficiency of Zn-ion batteries.