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 large 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 ^- greatly outperform commercial electrolytes. In short, SiB₁₁ (BO)₁₂ ^- -based compound is demonstrated to be a high-voltage electrolyte for AMIBs.