Energy landscapes in diexo and exo/endo isomers derived from Li2B12H12

► A new thermal injection/ejection mechanism found for an endohedral closo-borane: diexo-Li2B12H12 ↔ exo/endo-{Li+···[Li@B12H12]-}. ► The two Li+ ions in diexo-Li2B12H12 orbit around the closo-borane cage with an energy barrier window of 5-8 kcal/mol. ► Li atoms inside the cage bear a formal charge corresponding to a Liδ− anion.