Variation in structure and Li+-ion migration in argyrodite-type Li6PS5X (X = Cl, Br, I) solid electrolytes

• Published in: Journal of solid state electrochemistry Vol. 16; no. 5; pp. 1807 - 1813
• Main Authors: Rayavarapu, Prasada Rao, Sharma, Neeraj, Peterson, Vanessa K., Adams, Stefan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2012
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Original Paper; Physical Chemistry; Lithium ion conduction; Ion transport; Bond valence; Neutron diffraction
• ISSN: 1432-8488; 1433-0768
• DOI: 10.1007/s10008-011-1572-8

All-solid-state rechargeable lithium-ion batteries (AS-LIBs) are attractive power sources for electrochemical applications due to their potentiality in improving safety and stability over conventional batteries with liquid electrolytes. Finding a solid electrolyte with high ionic conductivity and compatibility with other battery components is a key factor in raising the performance of AS-LIBs. In this work, we prepare argyrodite-type Li 6 PS 5 X (X = Cl, Br, I) using mechanical milling followed by annealing. X-ray diffraction characterization reveals the formation and growth of crystalline Li 6 PS 5 X in all cases. Ionic conductivity of the order of 7 × 10 −4 S cm −1 in Li 6 PS 5 Cl and Li 6 PS 5 Br renders these phases suitable for AS-LIBs. Joint structure refinements using high-resolution neutron and laboratory X-ray diffraction provide insight into the influence of disorder on the fast ionic conductivity. Besides the disorder in the lithium distribution, it is the disorder in the S 2− /Cl − or S 2− /Br − distribution that we find to promote ion mobility, whereas the large I − cannot be exchanged for S 2− and the resulting more ordered Li 6 PS 5 I exhibits only a moderate conductivity. Li + ion migration pathways in the crystalline compounds are modelled using the bond valence approach to interpret the differences between argyrodites containing different halide ions.