An azamacrocyclic electrolyte additive to suppress metal deposition in lithium-ion batteries

Abstract An azamacrocyclic compound (1,4,8,11-tetraazacyclotetradecane, cyclam), which forms strong chelate complexes with metal ions such as Mn(II) and Fe(II), is tested as an electrolyte additive to suppress metal deposition. The tetradentate cyclic ligand is electrochemically stable within the working voltage of lithium-ion batteries (0.0-4.5 V vs. Li/Li⁺), hence it is practicable as an electrolyte additive. Deposition of Mn on a graphite electrode, which is severe when a Li/graphite cell is cycled in a Mn(II)-containing electrolyte solution, is greatly suppressed by adding cyclam. Our elemental analysis reveals negligible Mn deposits on a graphite electrode indicating the beneficial role of cyclam. The suppression of metal deposition is further indicated by the absence of an internal short between Li metal and lithium cobalt oxide positive electrode.