Investigating the ion conductivity and synthesis conditions of calcium monocarborane solid-state electrolytes

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.

Graphical abstract: Investigating the ion conductivity and synthesis conditions of calcium monocarborane solid-state electrolytes

Supplementary files

Article information

Article type
Communication
Submitted
03 Jul 2024
Accepted
13 Sep 2024
First published
20 Sep 2024
This article is Open Access
Creative Commons BY license

Energy Adv., 2024, Advance Article

Investigating the ion conductivity and synthesis conditions of calcium monocarborane solid-state electrolytes

T. Shinohara, K. Kisu, S. Takagi and S. Orimo, Energy Adv., 2024, Advance Article , DOI: 10.1039/D4YA00441H

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