Two Layers of Computational Screening on Silaborane‐based Clusters Filter Ca(SiB₁₁H₁₁CH₃)₂ as the Promising Electrolyte for Calcium‐Ion Batteries

Abstract

Calcium‐ion batteries (CIBs) are promising energy storage systems, but the unavailability of adept electrolytes has hindered their development. In this work, a range of silaborane clusters ( normalSnormalinormalBn-1Hn- ${{{\rm S}{\rm i}{\rm B}}_{n-1}{{\rm H}}_{n}^{-}}$ ; n=5–15) were investigated using density functional theory (DFT) at ωB97XD3/6‐311+G(d,p) level of theory. The vertical detachment energy (VDE), electrochemical stability window (ESW) and binding energy (BE) of the silaboranes were computed at the same level of DFT. A methodology based on molecular electrostatic potential surface analysis was designed to locate the most suitable binding site for calcium ions on the clusters. DFT results show that the SiB11 normalH12- ${{{\rm H}}_{12}^{-}}$ cluster turns out to be superior to other candidates. Effect of substitution on silaboranes ( normalSnormalinormalBn-1Hn-1 ${{{\rm S}{\rm i}{\rm B}}_{n-1}{{\rm H}}_{n-1}}$ R− R=−CH3, −NCS, −CF3, −F and −Cl) was computed. −NCS and −CF3 substituted SiB11 normalH12- ${{{\rm H}}_{12}^{-}}$ ions were found to be the best from DFT. Ab initio molecular dynamics (AIMD) studies were performed to explore the interactions between silaborane‐based electrolytes and the Ca anode. AIMD results highlight the decomposition of −NCS and −CF3 substituted SiB11 normalH12- ${{{\rm H}}_{12}^{-}}$ on Ca anode. DFT and AIMD studies reveal that −CH3 substituted silaborane‐based Ca‐salt (Ca(SiB11H11CH3)2) is the promising electrolyte for CIBs.