# Impact of Chelating Agent Choice on Growth Kinetics and Defect Chemistry in Sol–Gel-Synthesized Li- and Mn-Rich Layered Cathodes

## TL;DR

Choosing the right chelating agent during synthesis affects the structure and performance of Li- and Mn-rich cathodes for batteries.

## Contribution

The study shows how chelating agents influence defect chemistry and electrochemical stability in layered oxide cathodes.

## Key findings

- Oxalic acid-derived samples show better electrochemical stability and capacity retention compared to citric acid-derived ones.
- Oxygen vacancy mobility during cycling improves structural flexibility and limits Li/TM mixing.
- Precursor selection allows tailoring defects without post-synthesis treatment.

## Abstract

The electrochemical performance and structural stability
of Li-
and Mn-rich layered oxide cathodes are critically influenced by synthesis
conditions, yet the roles of chelating agents and defect chemistry
remains elusive. In this study, we systematically investigate Li1.2Mn0.54Ni0.13Co0.13O2 cathode powders synthesized via the sol–gel method
using citric acid or oxalic acid as the chelating agent, each calcined
at 850 and 900 °C. Despite introducing greater initial disorder,
oxalic acid-derived samples, particularly the one calcined at 900
°C, demonstrate improved electrochemical stability and capacity
retention. Operando XRD reveals that this material
undergoes a pronounced unit cell expansion during the first cycle,
a response linked largely to the mobility and homogenization of oxygen
vacancies introduced during the synthesis. This structural flexibility
accommodates redox-driven strain during cycling, which limits Li/TM
mixing and enables over-reduction of Ni, as confirmed by operando XANES and ex situ EXAFS. These results highlight
that oxygen vacancy mobility during cycling dominates the effects
of the initial structural order, where different types of defects
are present, and plays a decisive role in governing redox pathways
and cycling stability. The selection of the precursor allows tailoring
introduction of these defects without postsynthesis treatment. This
study provides a comprehensive framework for designing high-performance
Li- and Mn-rich layered oxide cathodes by tuning synthesis chemistry
to engineer beneficial structural disorder and defect dynamics.