Abiram Krishnan

(Advisor: Prof. Faisal Alamgir)

will propose a doctoral thesis entitled,

Revealing Anion Contributions in Lithium-Ion Batteries using Inner-Shell X-Ray Spectroscopy

On

Friday, March 21, 2025 at 11 am ET

Virtually via Microsoft Teams:

Join the meeting now

Meeting ID: 227 516 451 677

Passcode: 8Ks2rv79

Committee:

Prof. Faisal Alamgir – School of Material Science and Engineering (advisor)

Prof. Preet Singh – School of Material Science and Engineering

Prof. Matthew McDowell – School of Material Science and Engineering

Prof. Gleb Yushin – School of Material Science and Engineering

Prof. Yang Shao-Horn - Department of Material Science and Engineering at MIT

Dr. Jagjit Nanda - SLAC National Accelerator Laboratory

Abstract

The chemical state of elements in a battery electrode provides valuable insights into the redox reactions occurring at the electrode site during charge-discharge cycles. While past research has extensively investigated the role of cations in these reactions, the contribution of anions has received little to no attention. This is primarily due to the limited tools available to directly study the chemical state of anions. Inner-shell spectroscopy, a set of x-ray-based methods that generates core electron holes, is well-suited for this purpose due to its element selectivity and ability of X-rays to probe electrode materials during in-situ or operando studies. Among these methods, x-ray absorption spectroscopy (XAS) examines the process of generating electron core holes, offering insights into the electronic structure and local atomic arrangements of specific elements. Complementarily, x-ray emission spectroscopy (XES) studies the filling of generated electron core holes, providing sensitivity to chemical state, spin state, and ligand environment, making it an essential companion to XAS.

In this thesis, I will be exploring the role of anions in monoanion LiCoO2 (LCO) and polyanion-based LiFePO4 (LFP) cathode material for lithium-ion batteries (LIBs). In LCO, the activity of oxygen during the initial 10% of lithium removal will be explored. This region is selected as it is suspected to have a phase change resulting in an anomalous spin change of cobalt, altering LCO’s magnetic and electronic behavior. In LFP, the change in oxidation state of Fe, P, and O, along with Fe-O and P-O interactions are investigated to study the role of anions and its relationship to the formation of a metastable phase during the charge cycle. Additionally, this work will explore the relationship between transition metal-oxygen covalency in LiNixMnyCozO2 (x + y + z = 1, NMCs) to nickel content. This is done using valence-to-core emissions from the transition metal (TM), which represent the occupied state of TM 3d – O 2p hybrid orbitals. This work further includes an investigation of using these emissions to detect anion redox in TM-based batteries. The material examined to benchmark this capability is Ni3S2 anode material for LIBs. Sulfur activity will be detected using Ni Kβ emission and verified using established methods.