Corrosion Prevention Mechanism of Aluminum Metal in Superconcentrated Electrolytes

Metal corrosion is a serious problem that has beset various electrochemical systems. For lithium‐ion batteries, oxidative corrosion of an Al current collector has been a great challenge in designing new electrolyte materials, and only a few lithium salts (e.g. LiPF 6 ) are in practical use. The present work shows effective suppression of Al corrosion up to 4.5 V versus Li + /Li by using a highly concentrated electrolyte of lithium bis(fluorosulfonyl)amide (LiFSA). The corrosion prevention mechanism can be interpreted in relation to a remarkable change in solution structures at a certain threshold concentration. It is demonstrated that highly concentrated LiFSA/acetonitrile electrolyte enables highly reversible charge–discharge cycling of a 4 V‐class LiMn 2 O 4 /Li cell at a higher rate (ca. 50 % capacity retention at 20 C compared to C/2) than a state‐of‐the‐art commercial electrolyte (<20 %), thus providing a new design strategy for electrolyte materials in high‐rate lithium‐ion batteries.