Colossal Stability of SiB11(BO)12-: An Implication as Potential Electrolyte in High-Voltage Alkali-Ion Battery.

High-voltage alkali metal-ion batteries (AMIBs) require a non-hazardous, low-cost, and highly stable electrolyte with a large operating potential and rapid ion conductivity. Here, we have reported a halogen-free high-voltage electrolyte based on SiB11(BO)12-. Because of the weak π-orbital interaction of -BO as well as the mixed covalent and ionic interaction between SiB11-cage and -BO ligand, SiB11(BO)12- has colossal stability. SiB11(BO)12- possesses extremely high vertical detachment energy (9.95 eV), anodic voltage limit (~10.05 V), and electrochemical stability window (~9.95 V). Furthermore, SiB11(BO)12- is thermodynamically stable at high temperatures, and its larger size allows for faster cation movement. The alkali salts MSiB11(BO)12 (M = Li, Na, and K) are easily dissociated into ionic components. Electrolytes based on SiB11(BO)12- outperform commercial electrolytes greatly. In short, SiB11(BO)12--based compound has been demonstrated to be a high-voltage electrolyte for AMIBs.