{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,24]],"date-time":"2026-10-24T12:39:56Z","timestamp":1792845596351,"version":"4.5.0"},"reference-count":34,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T00:00:00Z","timestamp":1774310400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"crossref","award":["NRF-2022R1F1A1062928"],"award-info":[{"award-number":["NRF-2022R1F1A1062928"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Technology development Program","award":["RS-2024-00487176"],"award-info":[{"award-number":["RS-2024-00487176"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>Calcium-ion batteries (CIBs) offer several advantages. CIBs are viable alternatives to lithium-based battery systems owing to the natural abundance, low cost, and high volumetric capacity of calcium. However, their development has been severely constrained by electrolyte instability and water sensitivity. We conducted a systematic examination of Ca(ClO4)2 and Ca(PF6)2 electrolytes, focusing on low-cost salt production, solvent selection, and stringent dehydration procedures. Acetonitrile (ACN) was the ideal solvent for high salt solubility and reversible Ca2+ electrochemistry, while carbonate solvents failed rapidly. We found that even a small amount of moisture in the electrolyte significantly affected the electrochemical performance. This study improved the dehydration process by using 3 \u00c5 molecular sieve (MS3A) and vacuum drying to reduce moisture to ppm levels, stabilizing the electrolyte. Prussian blue (PB) half cells exhibited reversible capacities of up to \u224895 mAh g\u22121, whereas PB-hard carbon full cells utilizing dried Ca(ClO4)2 showed stable cycling over 240 cycles with a Coulombic efficiency of \u224899% and capacity loss of only \u224817%. This study establishes a moisture-controlled electrolyte as a critical enabler for practical CIBs.<\/jats:p>","DOI":"10.3390\/mi17040390","type":"journal-article","created":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T08:02:49Z","timestamp":1774339369000},"page":"390","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Moisture-Controlled Electrolyte Engineering Enables Durable Calcium-Ion Batteries"],"prefix":"10.3390","volume":"17","author":[{"given":"Yeon Jwoong","family":"Kim","sequence":"first","affiliation":[{"name":"School of Chemical, Biological, and Battery Engineering, Gachon University, Seongnam-si 13120, Gyeonggi-do, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8743-9515","authenticated-orcid":false,"given":"Tejaswi Tanaji","family":"Salunkhe","sequence":"additional","affiliation":[{"name":"School of Chemical, Biological, and Battery Engineering, Gachon University, Seongnam-si 13120, Gyeonggi-do, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8857-0061","authenticated-orcid":false,"given":"Il Tae","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Chemical, Biological, and Battery Engineering, Gachon University, Seongnam-si 13120, Gyeonggi-do, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1939","DOI":"10.1007\/s10008-017-3610-7","article-title":"Lithium ion, lithium metal, and alternative rechargeable battery technologies: The odyssey for high energy density","volume":"21","author":"Placke","year":"2017","journal-title":"J. Solid State Electrochem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"118022","DOI":"10.1016\/j.jelechem.2023.118022","article-title":"Exploring inexpensive electrodes for safer and evolved dual-ion batteries using modified electrolytes for enhanced energy density","volume":"953","author":"Yoo","year":"2024","journal-title":"J. Electroanal. Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"107826","DOI":"10.1016\/j.rinp.2024.107826","article-title":"Highly efficient Z scheme heterojunction of colloidal SnO2 quantum dots grafted g-C3N4 for the degradation of rhodamine B under visible light","volume":"62","author":"Bathula","year":"2024","journal-title":"Results Phys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"646","DOI":"10.1038\/s41560-020-0655-0","article-title":"Current status and future directions of multivalent metal-ion batteries","volume":"5","author":"Liang","year":"2020","journal-title":"Nat. Energy"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"5797","DOI":"10.1039\/D2SC00267A","article-title":"Progress and prospects of electrolyte chemistry of calcium batteries","volume":"13","author":"Wei","year":"2022","journal-title":"Chem. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.jechem.2023.10.043","article-title":"Powering the future: A comprehensive review on calcium-ion batteries","volume":"90","year":"2024","journal-title":"J. Energy Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"6616","DOI":"10.1039\/D4EE02003K","article-title":"High-solvation electrolytes for ultra-stable calcium-ion storage","volume":"17","author":"Wang","year":"2024","journal-title":"Energy Environ. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2402157","DOI":"10.1002\/aenm.202402157","article-title":"Challenges and Progress in Anode-Electrolyte Interfaces for Rechargeable Divalent Metal Batteries","volume":"14","author":"Wang","year":"2024","journal-title":"Adv. Energy Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1801702","DOI":"10.1002\/adma.201801702","article-title":"Calcium-Ion Batteries: Current State-of-the-Art and Future Perspectives","volume":"30","author":"Gummow","year":"2018","journal-title":"Adv. Mater."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"6331","DOI":"10.1021\/acs.chemrev.9b00339","article-title":"Achievements, Challenges, and Prospects of Calcium Batteries","volume":"120","author":"Ponrouch","year":"2020","journal-title":"Chem. Rev."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Salunkhe, T.T., and Kim, I.T. (2024). Expanded Graphite as a Superior Anion Host Carrying High Output Voltage (4.62 V) and High Energy Density for Lithium Dual-Ion Batteries. Micromachines, 15.","DOI":"10.3390\/mi15111324"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3536","DOI":"10.1149\/1.2085455","article-title":"The Electrochemical Behavior of Calcium Electrodes in a Few Organic Electrolytes","volume":"138","author":"Aurbach","year":"1991","journal-title":"J. Electrochem. Soc."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1002\/cite.202400121","article-title":"Identification of Electrolyte Salts in Lithium-Ion Battery Black Mass","volume":"97","author":"Hansel","year":"2025","journal-title":"Chem. Ing. Tech."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"101030","DOI":"10.1016\/j.coelec.2022.101030","article-title":"Progress on predicting the electrochemical stability window of electrolytes","volume":"34","author":"Chen","year":"2022","journal-title":"Curr. Opin. Electrochem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1016\/j.coelec.2018.10.015","article-title":"Challenges with prediction of battery electrolyte electrochemical stability window and guiding the electrode\u2013electrolyte stabilization","volume":"13","author":"Borodin","year":"2019","journal-title":"Curr. Opin. Electrochem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"8442","DOI":"10.1021\/acs.chemmater.5b04027","article-title":"Rechargeable Ca-Ion Batteries: A New Energy Storage System","volume":"27","author":"Lipson","year":"2015","journal-title":"Chem. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3369","DOI":"10.1038\/s41467-021-23703-x","article-title":"A new high-voltage calcium intercalation host for ultra-stable and high-power calcium rechargeable batteries","volume":"12","author":"Xu","year":"2021","journal-title":"Nat. Commun."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"201779","DOI":"10.1098\/rsos.201779","article-title":"Strategies for synthesis of Prussian blue analogues","volume":"8","author":"Kjeldgaard","year":"2021","journal-title":"R. Soc. Open Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"118562","DOI":"10.1016\/j.jelechem.2024.118562","article-title":"Synergistic integration of MoS2 nanopetals and SnO2 quantum dots for enhanced supercapacitor performance","volume":"970","author":"Bathula","year":"2024","journal-title":"J. Electroanal. Chem."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"133232","DOI":"10.1016\/j.colsurfa.2024.133232","article-title":"Substantial enhancement of optoelectronics and piezoelectric properties of novel hollow ZnO nanorods towards efficient flexible touch and bending sensor","volume":"685","author":"Misra","year":"2024","journal-title":"Colloids Surf. A Physicochem. Eng. Asp."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"8351","DOI":"10.1021\/jo101589h","article-title":"Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants","volume":"75","author":"Williams","year":"2010","journal-title":"J. Org. Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1016\/j.chemosphere.2009.10.025","article-title":"Mineral oil regeneration using selective molecular sieves as sorbents","volume":"78","author":"Majano","year":"2010","journal-title":"Chemosphere"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2003685","DOI":"10.1002\/aenm.202003685","article-title":"Multi-Ions Electrolyte Enabled High Performance Voltage Tailorable Room-Temperature Ca-Metal Batteries","volume":"11","author":"Song","year":"2021","journal-title":"Adv. Energy Mater."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Dyson, P., and Tilmann, G. (2005). Miscellaneous Reactions. Metal Catalysed Reactions in Ionic Liquids, Springer.","DOI":"10.1007\/1-4020-3915-8"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"4573","DOI":"10.1039\/C7CC01938F","article-title":"Synthesis of Ca(PF6)2, formed via nitrosonium oxidation of calcium","volume":"53","author":"Keyzer","year":"2017","journal-title":"Chem. Commun."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1039\/D4EW00758A","article-title":"Kinetics and mechanism of hydrolysis of PF6\u2212 accelerated by H+ or Al3+ in aqueous solution","volume":"11","author":"Miyashita","year":"2025","journal-title":"Environ. Sci. Water Res. Technol."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Tyler, J.L., Sacci, R.L., and Nanda, J. (2021). Anion Coordination Improves High-Temperature Performance and Stability of NaPF6-Based Electrolytes for Supercapacitors. Energies, 14.","DOI":"10.3390\/en14154409"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"570","DOI":"10.1002\/batt.201900219","article-title":"Current Understanding of Nonaqueous Electrolytes for Calcium-Based Batteries","volume":"3","author":"Melemed","year":"2020","journal-title":"Batter. Supercaps"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"8200","DOI":"10.1039\/D1CP00359C","article-title":"Lithium ion battery degradation: What you need to know","volume":"23","author":"Edge","year":"2021","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Hu, C., Geng, M., Yang, H., Fan, M., Sun, Z., Yu, R., and Wei, B. (2024). A Review of Capacity Fade Mechanism and Promotion Strategies for Lithium Iron Phosphate Batteries. Coatings, 14.","DOI":"10.3390\/coatings14070832"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3788","DOI":"10.1021\/acsenergylett.1c01657","article-title":"Role of Electrolyte Oxidation and Difluorophosphoric Acid Generation in Crossover and Capacity Fade in Lithium Ion Batteries","volume":"6","author":"Jayawardana","year":"2021","journal-title":"ACS Energy Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"144631","DOI":"10.1016\/j.cej.2023.144631","article-title":"Three-dimensional electrodes in hybrid electrolytes for high-loading and long-lasting calcium-ion batteries","volume":"471","author":"Kim","year":"2023","journal-title":"Chem. Eng. J."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2559","DOI":"10.1039\/D0EE00831A","article-title":"Alkoxy-functionalized ionic liquid electrolytes: Understanding ionic coordination of calcium ion speciation for the rational design of calcium electrolytes","volume":"13","author":"Gao","year":"2020","journal-title":"Energy Environ. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"109311","DOI":"10.1016\/j.est.2023.109311","article-title":"A review on ion transport pathways and coordination chemistry between ions and electrolytes in energy storage devices","volume":"74","author":"Gerdroodbar","year":"2023","journal-title":"J. Energy Storage"}],"container-title":["Micromachines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-666X\/17\/4\/390\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T05:14:43Z","timestamp":1774502083000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-666X\/17\/4\/390"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,24]]},"references-count":34,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["mi17040390"],"URL":"https:\/\/doi.org\/10.3390\/mi17040390","relation":{},"ISSN":["2072-666X"],"issn-type":[{"value":"2072-666X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,24]]}}}