Lithium iron phosphate (LiFePO4) is the prototypical two-phase battery material, whose complex patterns of lithium ion intercalation provide a testing ground for theories of electrochemical thermodynamics. Using a depth-averaged (a-b plane) phase-field model of coherent phase separation driven by Faradaic reactions, we reconcile conflicting experimental observations of diamond-like phase patterns in micron-sized platelets and surface-controlled patterns in nanoparticles. Elastic analysis predicts this morphological transition for particles whose a-axis dimension exceeds the bulk elastic stripe period. We also simulate a rich variety of non-equilibrium patterns, influenced by size-dependent spinodal points and electro-autocatalytic control of thermodynamic stability.
@article{arxiv.1808.06164,
title = {Size-dependent phase morphologies in LiFePO4 battery particles},
author = {Daniel A. Cogswell and Martin Z. Bazant},
journal= {arXiv preprint arXiv:1808.06164},
year = {2018}
}