The role of vacancies and defects in Na 0.44 MnO 2 nanowire catalysts for lithium–oxygen batteries

Na0.44MnO2 nanowires were acid leached in nitric acid, and dehydrated by heat treatment to induce controllable defect formation as monitored by high resolution TEM studies. The charge–discharge tests using these materials as catalysts (or “promoters”) in rechargeable lithium–oxygen batteries (in non-carbonate electrolytes) showed that a high defect concentration results in a doubling of the reversible energy storage capacity up to 11000 mA h g−1, and lowered overpotentials for oxygen evolution. The role of the defects/vacancies in determining oxygen reduction behavior is highlighted.