Material Search for a Li₁₀GeP₂S₁₂-Type Solid Electrolyte in the Li–P–S–X (X = Br, I) System via Clarification of the Composition–Structure–Property Relationships

Abstract

All-solid-state Li-metal batteries require fast Li-ion conductors that are compatible with Li-metal electrodes. Herein, we aim to obtain such Liion conductors in Li 2 S−P 2 S 5 −LiX (X = Br, I) systems, where new tetragonal phases with P4 2 /nmc symmetry were formed at compositions of Li 10 P 3 S 12 Br (LPSBr) and Li 10.25 P 3 S 12.25 I 0.75 (LPSI). Rietveld refinement analyses indicated that both materials were structural analogues of a renowned superionic conductor, Li 10 GeP 2 S 12 (LGPS), with additional anions at 2a or 4c sites within LPSBr or LPSI, respectively. The LPSBr and LPSI phases exhibited ionic conductivities of 5.8(1) and 9.1(2) mS cm −1 at 300 K, respectively, with the latter having the highest conductivity among the reported Li−P−S−X (X = Br or I) systems. All-solid-state Li metal cells were prepared using LPSBr or LPSI as the separator to compare their charge−discharge cycle performances with those previously reported for Li cells using separator electrolytes with various chemical compositions. The most stable cyclability was observed for the Li cell using LPSBr, which exhibited a high ionic conductivity and phase purity, indicating that these two properties of the solid electrolyte are important for ensuring extended cycling of all-solid-state Li-metal batteries.

Recent Developments in the Field of Sulfide Ceramic Solid‐State Electrolytes

“…It was found that Li 10 P 3 S 12 Br and Li 10.25 P 3 S 12.25 I 0.75 retain the LGPS‐type structure demonstrating excellent Li + conductivities; namely, the reported σ RT of Li 10 P 3 S 12 Br is 5.8 mS cm −1 , and the reported σ RT of Li 10.25 P 3 S 12.25 I 0.75 is 9.1 mS cm −1 . [ 48 ]…”

Developments in New Materials for Electrochemistry and Energy Storage Devices

“…Additionally, materials, such as halogen-substituted systems that form a stable interface with lithium metal and silicon-based materials, that further enhance the ionic conductivity are available. 88,89 More recently, a LGPSderivative with a conductivity of 32 mS cm ¹1 has been synthesized by a high-entropy approach. 90…”

Investigating the Li+substructure and ionic transport in Li10GeP2−xSbxS12(0 ≤x≤ 0.25)

“…1,3,4 Within recent years, many researchers have focused on sulfide-based conductors, e.g. argyrodite Li 6 PS 5 X (X = Cl, Br, I), [5][6][7][8] thio-LISICON Li x M 1Ày M 0 y S 4 (M = Ge, Si, and M 0 = P, Sb, Al, Ga), [9][10][11][12] and the Li 10 GeP 2 S 12 (LGPS) family, [13][14][15][16][17] using substitutions to understand the underlying Li ion diffusion mechanism.…”