Suppression of Phase Separation in LiFePO4 Nanoparticles During Battery Discharge

TL;DR

This paper introduces a phase-field model showing that high discharge currents prevent phase separation in LiFePO4 nanoparticles, explaining their improved battery performance.

Contribution

It presents a novel electrochemical phase-field model demonstrating suppression of phase separation at high currents in LiFePO4 nanoparticles.

Findings

High currents eliminate phase separation in nanoparticles.

Homogeneous filling occurs above a critical current density.

This explains the superior rate capability of nano-LiFePO4.

Abstract

Using a novel electrochemical phase-field model, we question the common belief that LixFePO4 nanoparticles separate into Li-rich and Li-poor phases during battery discharge. For small currents, spinodal decomposition or nucleation leads to moving phase boundaries. Above a critical current density (in the Tafel regime), the spinodal disappears, and particles fill homogeneously, which may explain the superior rate capability and long cycle life of nano-LiFePO4 cathodes.