This project SUPERFACE aims the improvement of the energy-storage capability of electrochemical energy storage (EES) devices as supercapacitors (SCs) from the better understanding of the electrolyte/electrode interface. In particular, the project focuses on the proper design of the electrolyte (salt concentration, sort of solvents with different hydrogen-bond (HB) capabilities and their proportion, cost, safety and sustainability) that provides the optimum molecular structure for the optimum performance of the EES devices with a deep analysis of the correlation between composition, solvation structure and performance at the electrode/electrolyte interface also in operando conditions. As the energy storage capability of any EES is intimately related to the maximum operating cell voltage and the electrochemical stability window (ESW) of the electrolyte of choice, the design of electrolytes composition is of great interest. In this regard, the so-called water-in-salt (WIS) electrolytes opened the path to 3 V Li-ion batteries thanks to the absence of “‘free”’ water molecules in highly concentrated solutions and/or the formation of protective solid electrolyte interphase (SEI) layer on the electrodes that prevents the reduction of both ions and water molecules. However, the typically high viscosity of these electrolytes limited their transport properties and hence, an optimum performance in terms of power densities. In our previous project (RTI2018-097728-B-I00/MAT), we first explored the use of WIS electrolytes based on (deep) eutectic mixtures (WIDESs) in SC cells in order to circumvent these matters by dilution with some coordinating co-solvents to, after combination with water, obtain partially saturated liquid (PSL) electrolytes. Then, we noticed that identifying the molecular structure of PSL electrolytes is critical to understand the rationale behind their electrochemical performance. Furthermore, its processing in the form of hydrogels/organogels to obtain partially saturated gel polymer (PSGP) electrolytes will be very interesting for their possible use in flexible devices. Summarizing, this project will provide a deep study of the correlation between the original chemical composition and the HB coordination among salts, co-solvents and polymers that results in the particular molecular structure (e.g., in terms of ion solvation and speciation, free vs. bound water molecules, etc.) that better performs as electrolyte., Proyectos de I+D+I (Generación de Conocimiento y Retos Investigación), Peer reviewed

European Union. (n.d.). EuroVoc dataset. Retrieved from https://op.europa.eu/en/web/eu-vocabularies/dataset/-/resource?uri=http://publications.europa.eu/resource/dataset/eurovoc. Additionally, the terminology set out in UNE-EN IEC 62933-1:2025 (UNE in force as of 07/05/2025) will be used to clarify terms, definitions, and concepts related to Electrical Energy Storage (EES) systems. Part 1: Terminology. The International equivalent standard is IEC 62933-1:2024., Dataset corresponding to the figures of articles: Anion-rich solvation structures in high entropy aqueous electrolytes for supercapacitors with enlarged potential windows and superior rate capabilities; González-Aguilera, Laura et al.; Journal of Materials Chemistry A 2025, 13, 31421-31434, DOI 10.1039/D5TA04796J, This work was supported by PID2021-125357OB-I00, Peer reviewed

The use of aqueous electrolytes as suitable electrolytes for supercapacitors (SCs) largely depends on maintaining a wide operating cell voltage window while ensuring good rate capabilities, thereby achieving high energy and power densities over many cycles. Electrolyte engineering with anion- and/or solvent-rich solvation structures has been recently explored in batteries of any type to enhance the interphase stability at high voltages, typically by the formation of a SEI. This approach has been less explored in SCs to not only extend the range of operational voltage but also balance the inherently distinct electrochemical stability of cations and anions with carbon electrodes. Herein, we prepared electrolytes composed of two ionic liquids with a common cation (e.g., EMIMTFSI and EMIMBF<inf>4</inf>) in solvent mixtures of H<inf>2</inf>O, DMSO and CH<inf>3</inf>CN. We found that the electrolyte with the richest solvation structure (i.e., with many and diverse anions that surrounded the cation) was the most effective at widening the cell voltage at which the electrolyte is capable of operating (e.g., up to 2.2 V). Interestingly, this extremely rich solvation structure also exhibited the best transport properties for different ions that, ultimately, were responsible for an excellent maintenance of the energy density at high power densities., This work was supported by MCIN/AEI/10.13039/501100011033 (TED2021-130372B-C42, TED2021-131812B-I00 and PID2021-123648OB-I00), by “ERDF A way of making Europe” (PID2021-123648OB-I00) and by “European Union Next Generation EU/PRTR” (TED2021-130372B-C42 and TED2021-131812B-I00). Authors also acknowledge the Severo Ochoa Centres of Excellence Program through Grant CEX2024-001445-S. L. G.-A. acknowledges the grant PRE2019-090008 funded by MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future”. P. G.-B. acknowledges the grant PRE2022-101750 funded by MCIN/AEI/10.13039/501100011033 and ESF+. X. L. also acknowledges the National Natural Science Foundation of China (22393961). J. M. V.-L., S. C., and R. M. M.-C. also thank C3UPO for HPC support. The Servicio Interdepartmental de Investigación (SIdI) of the Universidad Autónoma de Madrid and the Thermal Analysis Unit at the Instituto de Ciencia de Materiales de Madrid (ICMM) are acknowledged for helpful assistance with FTIR and NMR spectroscopies and DSC studies, respectively., Data for this article, including data presented in gures and tables have been included as part of the SI. Experimental procedures, tables with different data (physicochemical properties, NMR chemical shis, etc.), NMR, ATR and NIR spectra, RDFs from MD simulations, and electrochemical results (CVs, GCDs, Nyquist plots, etc.). See DOI: https://doi.org/10.1039/d5ta04796j., Peer reviewed

Dataset corresponding to the figures of articles: Phytic Acid-Based Deep Eutectic Solvents for Metal Extraction from Lithium Cobalt Oxide and Nickel Manganese Cobalt and the Use of the Resulting Leachates as Electrolytes for 2.0 V Supercapacitors; Xu, Boren et al.; ChemSusChem 2025, 18 (24), e202501306, DOI 10.1002/cssc.202501306, Dataset for experiments in publication DOI:10.1002/cssc.202501306; Xu, Boren et al.; 2025; Phytic Acid-Based Deep Eutectic Solvents for Metal Extraction from Lithium Cobalt Oxide and Nickel Manganese Cobalt and the Use of the Resulting Leachates as Electrolytes for 2.0 V Supercapacitors; https://doi.org/10.1002/cssc.202501306 [Dataset];, Data for this article, including data presented in gures and tables have been included as part of the SI. Experimental procedures, tables with different data (physicochemical properties, NMR chemical shis, etc.), NMR, ATR and NIR spectra, RDFs from MD simulations, and electrochemical results (CVs, GCDs, Nyquist plots, etc.). See DOI: https://doi.org/10.1039/d5ta04796j., Peer reviewed