Ionic Conductivity of Nanocrystalline and Amorphous Li₁₀GeP₂S₁₂: The Detrimental Impact of Local Disorder on Ion Transport

Abstract

Solids with extraordinarily high Li + dynamics are key for high performance all-solid-state batteries. The thiophosphate Li 10 GeP 2 S 12 (LGPS) belongs to the best Li-ion conductors with an ionic conductivity exceeding 10 mS cm −1 at ambient temperature. Recent molecular dynamics simulations performed by Dawson and Islam predict that the ionic conductivity of LGPS can be further enhanced by a factor of 3 if local disorder is introduced. As yet, no experimental evidence exists supporting this fascinating prediction. Here, we synthesized nanocrystalline LGPS by high-energy ball-milling and probed the Li + ion transport parameters. Broadband conductivity spectroscopy in combination with electric modulus measurements allowed us to precisely follow the changes in Li + dynamics. Surprisingly and against the behavior of other electrolytes, bulk ionic conductivity turned out to decrease with increasing milling time, finally leading to a reduction of σ 20°C by a factor of 10. 31 P, 6 Li NMR, and X-ray diffraction showed that ball-milling forms a structurally heterogeneous sample with nm-sized LGPS crystallites and amorphous material. At −135 °C, electrical relaxation in the amorphous regions is by 2 to 3 orders of magnitude slower. Careful separation of the amorphous and (nano)crystalline contributions to overall ion transport revealed that in both regions, Li + ion dynamics is slowed down compared to untreated LGPS. Hence, introducing defects into the LGPS bulk structure via ball-milling has a negative impact on ionic transport. We postulate that such a kind of structural disorder is detrimental to fast ion transport in materials whose transport properties rely on crystallographically well-defined diffusion pathways.

Impact of the Local Environment on Li Ion Transport in Inorganic Components of Solid Electrolyte Interphases

“…It is noted that Li ion diffusion in SEIs is mainly contributed by paths along the grain boundaries. ,, Some studies pointed out that cathode surface modification using some amorphous materials (e.g., Al 2 O 3 and AlF 3 ) is an effective strategy to improve the rate performance. , However, a recent work by Wilkening et al pointed out that introducing defects (enhancing disorder) into the LGPS bulk structure via ball-milling has a negative impact on ionic transport . A question then naturally arises: is the amorphous environment beneficial for improving Li ion diffusivity?…”

Lithium-Conducting Organic Solid Electrolyte for Organic Rechargeable Batteries: Boronated Benzoimidazole-Linked Polymer

“…This may be because the materials can be in the crystalline or amorphous state. 42 ACCEPTED MANUSCRIPT 9 Crystalline ICOF-based solid electrolytes are expected to have lower activation energies owing to the formation of optimal Li-ion conduction pathways. However, B-TFB-HAB-BILP is in an amorphous state, and amorphous materials are disadvantageous for ion transport within and at grain boundaries.…”

Encapsulating and Operating a Stable Li3ErBr6‐Based Solid Li–SeS2 Battery at Room Temperature

“…[ 15–17 ] In contrast, sulfides exhibit good processability and superior ionic conductivity. [ 18–20 ] However, sulfides possess poor electrochemical stability and are sensitive to oxygen and humidity. [ 21–24 ] Therefore, the exploration of inorganic SEs with comprehensive performance is important for the practical application of ASSLBs.…”