A system and method for a liquid electrolyte used in secondary electrochemical cells having at least one electrode including a TMCCC material, the liquid electrolyte enabling an increased lifetime while allowing for fast discharge to extremely high depth of discharge. The addition of dinitriles to liquid electrolytes in electrochemical cells in which energy storage is achieved by ion intercalation in transition metal cyanide coordination compounds (TMCCC) has the advantage of increasing device lifetime by inhibiting common chemical and electrochemical degradation mechanisms.