A highly active nanostructured metallic oxide cathode for aprotic Li–O 2 batteries

• Published in: Energy & environmental science Vol. 8; no. 4; pp. 1292 - 1298
• Main Authors: Kundu, Dipan, Black, Robert, Berg, Erik Jämstorp, Nazar, Linda F.
• Format: Journal Article
• Language: English
• Published: 2015
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/C4EE02587C

The aprotic lithium–oxygen cell is based on the reversible reduction of oxygen on a cathode host to form lithium peroxide, and has received much attention in the last few years owing to its promise to offer increased electrochemical energy density beyond that provided by traditional Li-ion batteries. Carbon has been extensively utilized as a host, but it reacts with Li 2 O 2 to form an insulating layer of lithium carbonate resulting in high overpotentials on charge. Establishing a stable, and conductive interface at the porous cathode is a major challenge that has motivated a search for non-carbonaceous cathode materials. Very few suitable materials have been discovered so far. Here we report on the synthesis of the metallic Magnéli phase Ti 4 O 7 with a crystallite size between 10–20 nm, and show that a cathode fabricated from this material greatly reduces the overpotential compared to carbon. Oxidation of lithium peroxide on charge starts just above 3 V, comparable to gold and TiC, and the majority (∼65%) of oxygen release occurs in the 3–3.5 V window vs. Li + /Li as determined by on-line electrochemical mass spectrometry. Ti 4 O 7 is much lighter and lower cost than gold, easy to prepare, and provides a controlled interface. X-ray photoelectron spectroscopy measurements show that a conductive, self-passivating substoichiometric metal oxide layer is formed at the surface which is important for stability.