Nanoscale defect engineering and mapping for cathode materials of multivalent ion batteries

Aqueous multivalent ion batteries, particularly Zn-ion batteries (ZIBs), represent a promising next-generation solution for grid-scale energy storage. However, their practical application is hindered by the lack of suitable cathode materials that can support reversible Zn-ion intercalation, as well as an incomplete understanding of their fundamental reaction mechanisms. This thesis aims to address these challenges by advancing nanoscale characterization techniques and offering fundamental insights into how particle size reduction and stacking fault (SF) engineering enhance Zn-ion diffusion within the spinel lattice. Chapter 1 provides a brief introduction to manganese-based oxides as cathode materials for ZIBs and outlines the remaining scientific and technical challenges. Chapter 2 investigates the influence of particle size on the phase transition pathways of λ-MnO2 during Zn-ion insertion, along with water-induced side reactions. We find that although Zn-ion insertion is enhanced in nanoparticles (NPs), their extraction from the spinel lattice is still difficult, leading to poor cycling stability. To address this limitation, Chapter 3 presents a novel method to improve the cycling performance of λ-MnO2 NPs in ZIBs by introducing SFs via thermal treatment. These SF defects are identified and quantified at nanometer resolution using four-dimensional scanning transmission electron microscopy (4D-STEM). Collocated 4D-STEM and electron energy loss spectroscopy (EELS) mapping reveals SFs enable reversible Zn-ion insertion and extraction in the spinel lattice. The thermal-induced phase transition pathway and the underlying mechanism by which SFs promote Zn-ion extraction are discussed in Chapter 4. We further extend the 4D-STEM technique and associated data-mining methods to other battery systems, demonstrating the effect of Na+ on Li-Na ion exchange in LiFePO4 through strain mapping. Finally, Chapter 5 summarizes the key findings and proposes future research directions, emphasizing the potential of integrating 4D-STEM with in-situ liquid-phase transmission electron microscopy to investigate ion transport and structural evolution in real time. These advances provide a powerful platform for the fundamental study and rational design of intercalation-type cathode materials for next-generation energy storage systems.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Tang, Zhichu

Contributors dc:contributor

• Chen, Qian
• Zuo, Jian-Min
• Braun, Paul V.
• Yang, Hong

• Defect Engineering
• Zn-ion Battery
• Energy Storage
• 4d-stem
• Nanomaterial Characterization

Statement dc:rights

• Copyright 2025 Zhichu Tang

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130132

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130132