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Defects, Entropy, and the Stabilization of Alternative Phase Boundary Orientations in Battery Electrode Particles
Author(s) -
Heo Tae Wook,
Tang Ming,
Chen LongQing,
Wood Brandon C.
Publication year - 2016
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201501759
Subject(s) - materials science , phase boundary , phase (matter) , chemical physics , configuration entropy , kinetics , microstructure , thermodynamics , electrode , structural stability , rigidity (electromagnetism) , statistical physics , chemistry , classical mechanics , physics , composite material , structural engineering , quantum mechanics , engineering
Using a novel statistical approach that efficiently explores the space of possible defect configurations, the present study investigates the chemomechanical coupling between interfacial structural defects and phase boundary alignments within phase‐separating electrode particles. Applied to the battery cathode material Li X FePO 4 as an example, the theoretical analysis reveals that small, defect‐induced deviations from an ideal interface can lead to dramatic shifts in the orientations of phase boundaries between Li‐rich and Li‐lean phases, stabilizing otherwise unfavorable orientations. Significantly, this stabilization arises predominantly from configurational entropic factors associated with the presence of the interfacial defects rather than from absolute energetic considerations. The specific entropic factors pertain to the diversity of defect configurations and their contributions to rotational/orientational rigidity of phase boundaries. Comparison of the predictions with experimental observations indicates that the additional entropy contributions indeed play a dominant role under actual cycling conditions, leading to the conclusion that interfacial defects must be considered when analyzing the stability and evolution kinetics of the internal phase microstructure of strongly phase‐separating systems. Possible implications for tuning the kinetics of (de)lithiation based on selective defect incorporation are discussed. This understanding can be generalized to the chemomechanics of other defective solid phase boundaries.