{"title":"Unraveling the contribution of water to the discharge capacity of Li-O2 batteries from a modelling perspective","authors":"Yuanhui Wang , Tianci Zhang , Liang Hao","doi":"10.1016/j.apenergy.2024.123852","DOIUrl":null,"url":null,"abstract":"<div><p>Adding water (H<sub>2</sub>O) to the electrolyte improves discharge capacity by enhancing the solution mechanism, but the evolution of discharge capacity with H<sub>2</sub>O content growth remains divergent. In view of this, the contribution of H<sub>2</sub>O to discharge capacity is revealed by modelling a lithium‑oxygen (Li-O<sub>2</sub>) battery coupled with the H<sub>2</sub>O reaction mechanism. With increasing H<sub>2</sub>O content in the electrolyte, the discharge capacity first rises thanks to the alleviation of surface passivation and then declines owing to the limitation of O<sub>2</sub> diffusion. Although the promotion of solution mechanism is most pronounced with a small amount of H<sub>2</sub>O (below 2000 ppm) in the dimethoxyethane (DME)-based electrolyte, the enhancement of solution mechanism in the tetraethylene glycol dimethyl ether (TEGDME)-based electrolyte is more sensitive to changes in H<sub>2</sub>O contents (above 500 ppm) than DME- and DMSO (dimethyl sulfoxide)-based electrolytes. Hence the H<sub>2</sub>O contents corresponding to the maximum discharge capacity (defined as “optimized water content”) of TEGDME- and DMSO-based electrolytes are 2000 ppm and 10,500 ppm based on the Super P carbon cathode, respectively. The evolutions of “optimized water content” and discharge capacity are more sensitive to changes in the porosity and initial carbon particle radius of the carbon cathode. Compared to the absence of H<sub>2</sub>O, the discharge capacities with the “optimized water content” increase by 360% and 346% at a porosity of 0.9, as well as by 268% and 290% for TEGDME- and DMSO-based electrolytes at an initial carbon particle radius of 70 nm, respectively. In consequence, the electrolyte composition and cathode structure codetermine the “optimized water content” and the maximum promotion of H<sub>2</sub>O to the discharge capacity.</p></div>","PeriodicalId":246,"journal":{"name":"Applied Energy","volume":null,"pages":null},"PeriodicalIF":10.1000,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Energy","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0306261924012352","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
Adding water (H2O) to the electrolyte improves discharge capacity by enhancing the solution mechanism, but the evolution of discharge capacity with H2O content growth remains divergent. In view of this, the contribution of H2O to discharge capacity is revealed by modelling a lithium‑oxygen (Li-O2) battery coupled with the H2O reaction mechanism. With increasing H2O content in the electrolyte, the discharge capacity first rises thanks to the alleviation of surface passivation and then declines owing to the limitation of O2 diffusion. Although the promotion of solution mechanism is most pronounced with a small amount of H2O (below 2000 ppm) in the dimethoxyethane (DME)-based electrolyte, the enhancement of solution mechanism in the tetraethylene glycol dimethyl ether (TEGDME)-based electrolyte is more sensitive to changes in H2O contents (above 500 ppm) than DME- and DMSO (dimethyl sulfoxide)-based electrolytes. Hence the H2O contents corresponding to the maximum discharge capacity (defined as “optimized water content”) of TEGDME- and DMSO-based electrolytes are 2000 ppm and 10,500 ppm based on the Super P carbon cathode, respectively. The evolutions of “optimized water content” and discharge capacity are more sensitive to changes in the porosity and initial carbon particle radius of the carbon cathode. Compared to the absence of H2O, the discharge capacities with the “optimized water content” increase by 360% and 346% at a porosity of 0.9, as well as by 268% and 290% for TEGDME- and DMSO-based electrolytes at an initial carbon particle radius of 70 nm, respectively. In consequence, the electrolyte composition and cathode structure codetermine the “optimized water content” and the maximum promotion of H2O to the discharge capacity.
期刊介绍:
Applied Energy serves as a platform for sharing innovations, research, development, and demonstrations in energy conversion, conservation, and sustainable energy systems. The journal covers topics such as optimal energy resource use, environmental pollutant mitigation, and energy process analysis. It welcomes original papers, review articles, technical notes, and letters to the editor. Authors are encouraged to submit manuscripts that bridge the gap between research, development, and implementation. The journal addresses a wide spectrum of topics, including fossil and renewable energy technologies, energy economics, and environmental impacts. Applied Energy also explores modeling and forecasting, conservation strategies, and the social and economic implications of energy policies, including climate change mitigation. It is complemented by the open-access journal Advances in Applied Energy.