# The Role of Intergranular Cracks on Fast Charging and Accelerated Degradation in Polycrystalline Layered Oxide Cathodes

## TL;DR

This paper explains how cracks in battery cathode materials can both harm and help battery performance, affecting how we design better energy storage.

## Contribution

The paper highlights the dual role of intergranular cracks in enhancing and degrading battery performance in layered oxide cathodes.

## Key findings

- Intergranular cracks in cathode materials cause structural degradation and performance loss.
- Cracks also improve reaction kinetics by increasing surface area and electrolyte access.
- Understanding this duality is essential for optimizing cathode design and modeling.

## Abstract

Polycrystalline layered oxide cathodes such as Li(NixMnyCoz)O2 (NMC) and Li(NixCoyAlz)O2 (NCA) are some of the most widely used materials for Li‐ion batteries. Due to anisotropic volume expansion upon lithium insertion and removal, such particles undergo substantial intergranular cracks. In this article, we presents a perspective on both the positive and negative roles of cracks on the electrochemical performance of these polycrystalline cathode particles based on recent research. Like in many other systems, cracks and fractures result in performance degradation and failure. However, in layered oxide particles, they also play a critical role in faster reaction kinetics by enabling electrolyte penetration, thereby shortening the diffusion length and increasing the reaction area. Acknowledging this dual nature of cracks and electrolyte penetration is critical in understanding how cathode materials are analyzed, modeled, and engineered for future energy storage applications.

Polycrystalline layered oxide cathodes, such as Li(Ni,Mn,Co)O2, create intergranular cracks from anisotropic volume changes during electrochemical cycling. These cracks negatively affect structural integrity and accelerate particle degradation, but also increase the surface area and thereby enable fast charge and discharge. Acknowledging this dual role is crucial for analyzing, modeling, and engineering cathode materials for advanced energy storage.