What Lies Beneath? Probing Buried Interfaces in Working Batteries

The interfaces between the active components in rechargeable batteries play a pivotal role in determining performance. This is where electrons and ions transfer between the electrodes and electrolyte during charging and discharging, and where many of the undesirable reactions that limit battery lifetime take place. Understanding how the structure and chemistry of these interfaces changes during operation is critical to developing higher capacity battery materials, fast charging protocols, and models to predict when batteries need replacing.

However, these interfaces are buried within the battery, making it extremely challenging to extract information without interference from the surrounding materials. This project investigates adapting powerful interface-sensitive methods, typically limited to vacuum conditions, so that they are compatible with battery measurements. The focus is on techniques that provide quantifiable, depth-resolved information on the chemical environment close to buried interfaces and includes X-ray photoelectron and absorption spectroscopies (XAS/XPS), second ion mass spectrometry (SIMS), and electron microscopy.

The project is pursuing both in situ cells that can be repeatedly disassembled and reassembled without breaking vacuum to allow measurement of each battery component at specific stages of cycling, and operando cells based on X-ray and electron transparent windows that allow measurement of interfaces during cycling.