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Boosting Solid‐State Diffusivity and Conductivity in Lithium Superionic Argyrodites by Halide Substitution
Author(s) -
Adeli Parvin,
Bazak J. David,
Park Kern Ho,
Kochetkov Ivan,
Huq Ashfia,
Goward Gillian R.,
Nazar Linda F.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201814222
Subject(s) - ionic conductivity , fast ion conductor , halide , dielectric spectroscopy , chemistry , conductivity , lithium (medication) , solid solution , vacancy defect , thermal diffusivity , analytical chemistry (journal) , inorganic chemistry , materials science , electrolyte , electrochemistry , crystallography , thermodynamics , organic chemistry , medicine , physics , electrode , endocrinology
Developing high‐performance all‐solid‐state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide‐rich solid solution phases in the argyrodite Li 6 PS 5 Cl family, Li 6− x PS 5− x Cl 1+ x , and combine electrochemical impedance spectroscopy, neutron diffraction, and 7 Li NMR MAS and PFG spectroscopy to show that increasing the Cl − /S 2− ratio has a systematic, and remarkable impact on Li‐ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li 5.5 PS 4.5 Cl 1.5 , exhibits a cold‐pressed conductivity of 9.4±0.1 mS cm −1 at 298 K (and 12.0±0.2 mS cm −1 on sintering)—almost four‐fold greater than Li 6 PS 5 Cl under identical processing conditions and comparable to metastable superionic Li 7 P 3 S 11 . Weakened interactions between the mobile Li‐ions and surrounding framework anions incurred by substitution of divalent S 2− for monovalent Cl − play a major role in enhancing Li + ‐ion diffusivity, along with increased site disorder and a higher lithium vacancy population.