Ether-based electrolytes are widely used in lithium-oxygen batteries because of their relatively high ionic conductivity, O₂ solubility, and electrochemical stability. However, conventional ethers have weak points, particularly the α-H atoms next to the ether bonds. Intermediates formed during the discharge/charge processes, such as O₂^– or ¹O₂, can cause hydrogen abstraction and, thus, decomposition of the electrolyte.

Yue Shen, Yunhui Huang, Huazhong University of Science and Technology, Wuhan, China, and colleagues have developed a fully methylated cyclic ether, 2,2,4,4,5,5-hexamethyl-1,3-dioxolane (HMD, pictured), in which all α-H atoms are replaced with methyl groups and unwanted hydrogen abstraction is avoided. HMD was synthesized via a one-step reaction between pinacol and 2,2-dimethoxypropane.

HMD shows excellent stability in the presence of O₂^– or ¹O₂. Side reactions at the cathode side are significantly suppressed. The cycle life of a cell with an HMD-based electrolyte is four times longer than for a cell with conventional ethers. According to the researchers, the findings could lead to the development of high-performance rechargeable lithium-oxygen batteries.

• A stable lithium-oxygen battery electrolyte based on fully methylated cyclic ether,
  Zhimei Huang, Haipeng Zeng, Meilan Xie, Xing Lin, Zhaoming Huang, Yue Shen, Yunhui Huang,
  Angew. Chem. Int. Ed. 2018.
  https://doi.org/10.1002/anie.201812983