Engineering high-energy-density sodium battery anodes for improved cycling with superconcentrated ionic-liquid electrolytes

• Published in: Nature materials Vol. 19; no. 10; pp. 1096 - 1101
• Main Authors: Rakov, Dmitrii A., Chen, Fangfang, Ferdousi, Shammi A., Li, Hua, Pathirana, Thushan, Simonov, Alexandr N., Howlett, Patrick C., Atkin, Rob, Forsyth, Maria
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.10.2020; Nature Publishing Group
• Subjects: 639/301/299/891; 639/638/440; 639/638/563/981; Anodes; Atomic force microscopy; Biomaterials; Chemistry and Materials Science; Condensed Matter Physics; Cycles; Dendrites; Dendritic structure; Density; Deposition; Electrodes; Electrolytes; Energy storage; Ionic liquids; Materials Science; Metal concentrations; Metal ions; Molecular dynamics; Nanotechnology; Optical and Electronic Materials; Pollutant deposition; Preconditioning; Safety; Salts; Sodium; Solid electrolytes; Storage batteries
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-020-0673-0

Non-uniform metal deposition and dendrite formation in high-density energy storage devices reduces the efficiency, safety and life of batteries with metal anodes. Superconcentrated ionic-liquid electrolytes (for example 1:1 ionic liquid:alkali ion) coupled with anode preconditioning at more negative potentials can completely mitigate these issues, and therefore revolutionize high-density energy storage devices. However, the mechanisms by which very high salt concentration and preconditioning potential enable uniform metal deposition and prevent dendrite formation at the metal anode during cycling are poorly understood, and therefore not optimized. Here, we use atomic force microscopy and molecular dynamics simulations to unravel the influence of these factors on the interface chemistry in a sodium electrolyte, demonstrating how a molten-salt-like structure at the electrode surface results in dendrite-free metal cycling at higher rates. Such a structure will support the formation of a more favourable solid electrolyte interphase, accepted as being a critical factor in stable battery cycling. This new understanding will enable engineering of efficient anode electrodes by tuning the interfacial nanostructure via salt concentration and high-voltage preconditioning. Non-uniform metal deposition and dendrite formation reduce the efficiency, safety and life of batteries with metal anodes. The influence of these factors in a sodium electrolyte now shows how a molten-salt-like structure at the electrode surface results in dendrite-free metal cycling at higher rates.