A Soft X-ray Journey into Batteries: How Fundamental Spectroscopy Helps Out Practical Energy Storage Devices

Presented by: Wanli Yang of Lawrence Berkeley National Laboratory

Energy storage is a critical but weak link in the chain of modern sustainable energy applications. The pressing demand of improved energy storage systems, especially for electric vehicles and green-grid, calls for speedy strategies for developing materials based on advanced analytic tools. Synchrotron based soft x-ray core-level spectroscopy is one of such incisive tools that probes the key electronic states pertaining to the performance of batteries.

This colloquium starts with introductions on the challenges of batteries for various kind of energy storage requirements. Problems associated with critical electron states in the vicinity of the Fermi level will be emphasized. Soft X-ray core-level spectroscopy, including soft X-ray absorption, emission, and resonant inelastic X-ray scattering will then be introduced in line with the problem-oriented discussions.

We will then discuss some recent achievements on using soft X-rays to reveal critical electronic structure information associated with materials for improving battery performance. We show that soft X-ray spectroscopy (i) reveals the key electron states that could trigger combined functionality of organic battery binder; (ii) quantitatively determines the detrimental effect in battery cycling life time; (iii) clarifies intriguing interstitial water effect of battery electrodes; and (iv) reveals the novel reduction and oxidation reactions in battery electrodes in both transition-metals and anions, which cannot be accessed by any other technique so far. Optionally, we will discuss some state-of-the-art soft x-ray in-situ/operando experiments of electrochemical devices, if there is time/interest.

This presentation itself will not focus on technical discussions for a specific scientific topic in battery materials, instead, the focus here is to showcase the soft X-ray spectroscopy for studying relevant electron states that are associated with a practical device, in hope that this could be taken as an example on corelevel soft x-ray spectroscopy for material researches, and inspire further thoughts and other topics in material physics.