Finite Element Simulation of NMC Particle Fracture during Calendering: a Route to Optimize Electrode Microstructures

TL;DR

This study uses finite element simulations to analyze NMC particle fracture during electrode calendering, revealing how pressure influences microstructure and guiding manufacturing optimization for better battery performance.

Contribution

First finite element model of NMC particle fracture during calendering, calibrated with experiments, to predict microstructural changes and optimize manufacturing processes.

Findings

Identified three calendering regimes: particle rearrangement, fracturing, and crushing.

Demonstrated microstructure sensitivity to calendering pressure.

Validated stress-strain predictions with experimental data.

Abstract

Beyond active material intrinsic properties, the electrode manufacturing process is a crucial step to reach high energy density and long-life of Li-ion batteries. In particular, very high pressures are applied to the electrode during the calendering step, that directly influence the microstructure and the electrochemical performances. This article reports the first calendering simulation of a NMC cathode using a finite element method (FEM), including the post-fracturation behaviour of the secondary NMC particles. Calibrated with nano-indentation experiments, the mechanical model provides stress-strain predictions fully consistent with experimental data. On assemblies up to 100 particles, simulations reveal three calendering regimes along compression: particle rearrangement, moderatepressure fracturing, and complete crushing. The model shows the strong sensitivity of the electrode microstructure to the calendering pressure level, and can thus be used as a guidance in the multi-criteria optimization of the manufacturing process.