Although the material in a battery electrode may look uniform to the naked eye, at the atomic level, it’s a diverse landscape. Tiny variations in materials can affect reaction rates, and thus battery performance, in complex ways.
Professor Jiangyu Li and his colleagues at the University of Washington have built a new tool that could provide a better understanding of how chemical reactions progress at the level of atoms and molecules, creating “new opportunities to engineer materials properties so as to achieve quantum leaps in performance.”
In “Scanning Thermo-ionic Microscopy for Probing Local Electrochemistry at the Nanoscale,” published in the Journal of Applied Physics, Jiangyu Li and his team describe a nanoscale probe that they developed. The concept is similar to atomic force microscopy – a tiny heated cantilever causes fluctuations in temperature and stress in the material beneath the probe. As the material expands and contracts, the cantilever vibrates in a way that can be measured using a laser beam, yielding a nanometer-scale map of the material.
The new approach has advantages over other types of atomic microscopy, and the team believes it will offer researchers a valuable tool for studying electrochemical material properties at the nanoscale. They tested it by measuring the concentration of charged species in Sm-doped ceria and LiFePO4, important materials in solid oxide fuel cells and lithium batteries.
A nanoscale map of the metal ceria produced with the new probe shows a higher response, represented by a yellow color, near the boundary between grains of metal. The higher response corresponds to a higher concentration of charged species.
Image credit: Ehsan Nasr Esfahani/University of Washington
“The concentration of ionic and electronic species are often tied to important rate properties of electrochemical materials – such as surface reactions, interfacial charge transfer, and bulk and surface diffusion – that govern the device performance,” Li said. “By measuring these properties locally on the nanoscale, we can build a much better understanding of how electrochemical systems really work, and thus how to develop new materials with much higher performance.”