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Dependence of Ion Transport on the Electronegativity of the Constituting Atoms in Ionic Crystals
Author(s) -
Zhang Qian,
Kaghazchi Payam
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201601208
Subject(s) - electronegativity , ionic bonding , chemistry , vacancy defect , ion , excited state , valence (chemistry) , fermi level , electrolyte , activation energy , schottky defect , schottky diode , atomic physics , electron , materials science , electrode , crystallography , physics , optoelectronics , organic chemistry , quantum mechanics , diode
Ion transport in electrode and electrolyte materials is a key process in Li‐based batteries. In this work, we study the mechanism and activation energy of ion transport ( E a ) in rock‐salt Li‐based LiX (X=Cl, Br, and I) materials. It is found that E a at low external voltages, where Li–X Schottky pairs are the most favorable defect types, is about 0.42 times the Gibbs energy of formation of LiX compound ( Δ G f). The value of 0.42 is the slope of the electronegativity of anions of binary Li‐based materials as a function ofΔ G f. At high voltages, where the Fermi level is located very close to the valence band maximum (VBM), electrons can be excited from the VB to Li vacancy‐induced states close to the Fermi level. Under this condition, the formation of Li vacancies that are compensated by holes is energetically more favorable than that of Li–X Schottky pairs, and therefore, the activation energies are lower in the former case. The wide range of reported experimental values of activation energies lies between calculated values at low and high voltage regimes. This work motivates further studies on the relation between the activation energy for ionic conductivity in solid materials and the intrinsic ground‐state properties of their free atoms.