Takara Shinohara, Kazuaki Kisu, Shigeyuki Takagi and Shin-ichi Orimo
{"title":"Investigating the ion conductivity and synthesis conditions of calcium monocarborane solid-state electrolytes†","authors":"Takara Shinohara, Kazuaki Kisu, Shigeyuki Takagi and Shin-ichi Orimo","doi":"10.1039/D4YA00441H","DOIUrl":null,"url":null,"abstract":"<p >Multivalent-ion and all-solid-state batteries have emerged as potential solutions to address resource concerns and safety issues. Calcium is a promising element for multivalent-ion batteries owing to its abundance in the Earth's crust and low reduction potential. In addition, complex hydrides exhibit both high ion conductivity and reduction stability, making them suitable materials for solid-state ion conductors. In this study, we investigated the thermal stability and optimised the synthesis conditions of calcium monocarborane, namely, Ca(CB<small><sub>11</sub></small>H<small><sub>12</sub></small>)<small><sub>2</sub></small>, which is a <em>closo</em>-type calcium complex hydride. In addition, we conducted electrochemical analysis to assess its performance as a solid-state divalent-ion conductor. The results indicate that a heat-treatment temperature of 433 K provides Ca(CB<small><sub>11</sub></small>H<small><sub>12</sub></small>)<small><sub>2</sub></small> with higher ion conductivity (<em>σ</em> = 1.42 × 10<small><sup>−4</sup></small> S cm<small><sup>−1</sup></small>) than the other heating temperatures. Thus, 433 K is considered optimal because [CB<small><sub>11</sub></small>H<small><sub>12</sub></small>]<small><sup>−</sup></small> anions decompose when heat-treated at and above 453 K. Furthermore, the insertion and deinsertion of Ca<small><sup>2+</sup></small> ions are stable and reversible in symmetric cells employing Ca–Sn alloy electrodes, representing the first time this has been observed for an inorganic solid-state calcium-ion conductor. Such insertion and deinsertion highlight the potential of Ca(CB<small><sub>11</sub></small>H<small><sub>12</sub></small>)<small><sub>2</sub></small> as a solid-state electrolyte for battery applications.</p>","PeriodicalId":72913,"journal":{"name":"Energy advances","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/ya/d4ya00441h?page=search","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Energy advances","FirstCategoryId":"1085","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2024/ya/d4ya00441h","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Multivalent-ion and all-solid-state batteries have emerged as potential solutions to address resource concerns and safety issues. Calcium is a promising element for multivalent-ion batteries owing to its abundance in the Earth's crust and low reduction potential. In addition, complex hydrides exhibit both high ion conductivity and reduction stability, making them suitable materials for solid-state ion conductors. In this study, we investigated the thermal stability and optimised the synthesis conditions of calcium monocarborane, namely, Ca(CB11H12)2, which is a closo-type calcium complex hydride. In addition, we conducted electrochemical analysis to assess its performance as a solid-state divalent-ion conductor. The results indicate that a heat-treatment temperature of 433 K provides Ca(CB11H12)2 with higher ion conductivity (σ = 1.42 × 10−4 S cm−1) than the other heating temperatures. Thus, 433 K is considered optimal because [CB11H12]− anions decompose when heat-treated at and above 453 K. Furthermore, the insertion and deinsertion of Ca2+ ions are stable and reversible in symmetric cells employing Ca–Sn alloy electrodes, representing the first time this has been observed for an inorganic solid-state calcium-ion conductor. Such insertion and deinsertion highlight the potential of Ca(CB11H12)2 as a solid-state electrolyte for battery applications.