NOVELTY - Electrochemical cell (I) comprises: a fuel electrode for oxidizing a metal fuel; a low temperature ionic liquid comprising positive ions and negative ions; an oxygen reduction enhancing compound added to the low temperature ionic liquid to form oxygen reduction enhancing positive ions, where the oxygen reduction enhancing positive ions are coordinated with at least negative ions forming oxygen reduction enhancing positive-negative ion complex; and an air electrode configured to absorb and reduce oxygen.    USE - The electrochemical cell is useful as a part of rechargeable battery (claimed), and in metal-air battery including rechargeable and non-rechargeable metal-air battery.    ADVANTAGE - The electrochemical cell utilizes oxygen reduction enhancing positive-negative ion complex which improves oxygen reduction thermodynamics and/or kinetics, relative to the ionic liquid without the oxygen reduction enhancing compound.    DETAILED DESCRIPTION - Electrochemical cell (I) comprises: a fuel electrode for oxidizing a metal fuel; a low temperature ionic liquid comprising positive ions and negative ions; an oxygen reduction enhancing compound added to the low temperature ionic liquid to form oxygen reduction enhancing positive ions, where the oxygen reduction enhancing positive ions are coordinated with at least negative ions forming oxygen reduction enhancing positive-negative ion complex; and an air electrode configured to absorb and reduce oxygen, where the oxygen reduction enhancing positive-negative ion complex improves oxygen reduction thermodynamics and/or kinetics, relative to the ionic liquid without the oxygen reduction enhancing compound. INDEPENDENT CLAIMS are also included for:    (1) a method (A) comprising: mixing an oxygen reduction enhancing compound with a low temperature ionic liquid to create a solution comprising an oxygen reduction enhancing positive-negative ion complex; exposing the solution to oxygen; and electrochemically reducing the oxygen;    (2) an electrochemical cell (II) comprising: a metal fuel electrode for oxidizing a metal fuel; a low temperature ionic liquid comprising positive ions and negative ions; a local oxide formation promoting compound added to the low temperature ionic liquid, the local oxide formation promoting additive dissolving in the low temperature ionic liquid to form local oxide formation promoting positive ions, where the positive ions of the local oxide formation promoting compound are coordinated with at least one negative ions forming local oxide formation promoting positive ion-negative ion complex; and an air electrode configured to absorb and reduce oxygen, and store oxides of the metal fuel, where the local oxide formation promoting positive ion-negative ion complex increases the formation and storage of oxides of the metal fuel at the air electrode during discharge relative to the ionic liquid without the local oxide formation promoting compound;    (3) an electrochemical cell (III) comprising: a fuel electrode for oxidizing a metal fuel; an ionically conductive medium comprising at least one aprotic ionic liquid and at least one protic ionic liquid comprising at least one available proton per ion pair; and an air electrode configured to absorb and reduce oxygen;    (4) a method (B) comprising: mixing a protic ionic liquid with an aprotic ionic liquid to create an ionically conductive medium comprising negative ions and positive ions, where at least one of the positive ions is a proton; exposing the ionically conductive medium to oxygen; and electrochemically reducing the oxygen; and    (5) an electrochemical cell (IV) comprising: a metal fuel electrode for oxidizing a metal fuel; an ionically conductive medium comprising at least one aprotic ionic liquid and at least one protic ionic liquid comprising at least one proton; and an air electrode configured to absorb and reduce oxygen and store oxides of the metal fuel, where the proton increases the formation and storage of oxides of the metal fuel at the air electrode during discharge relative to the ionically conductive medium without the protic ionic liquid.