Lithium-Ion-Conducting Argyrodite-Type Li₆PS₅X (X = Cl, Br, I) Solid Electrolytes Prepared by a Liquid-Phase Technique Using Ethanol as a Solvent

Abstract

Argyrodite-type crystals, Li 6 PS 5 X (X = Cl, Br, I), are promising solid electrolytes (SEs) for bulk-type allsolid-state lithium-ion batteries with excellent safety and high energy densities because of their high ionic conductivities and electrochemical stabilities. However, these advantageous features alone are not sufficient to achieve good cell performance. It is also critically important to have a simple and effective synthetic route to SEs and techniques for forming favorable solid−solid interfaces with large contact areas between the electrode and electrolyte particles. Here, we report an effective route for the preparation of argyrodite-type crystals using a liquid-phase technique via a homogeneous ethanol solution to improve cell performance using an SE-coating on the active material. The preparation conditions, such as appropriate halogen species and alcohol solvents, dissolution time, and drying temperature, are examined, finally resulting in Li 6 PS 5 Br with a lithium-ion conductivity of 1.9 × 10 −4 S cm −1 . Importantly, the obtained solution forms a favorable solid−solid electrode−electrolyte interface with a large contact area in the all-solid-state cells, resulting in a higher capacity than conventional techniques such as hand mixing using a mortar.

Graphitic Hollow Nanocarbon as a Promising Conducting Agent for Solid‐State Lithium Batteries

“…Figure a,b depict the EIS results for the coin‐type NCM and LCO cells, respectively. The Nyquist plots consist of two semicircles and Warburg tails . The semicircle in the middle‐frequency region is associated with the interfacial charge transfer resistance between the cathode and the SE layer ( R 1).…”

Quantitative analysis of crystallinity in an argyrodite sulfide-based solid electrolyte synthesized via solution processing

“…The electrolyte showed a high lithium-ion conductivity of 3.1 mS cm À1 at 25 C. 23 In addition, coating the electrode active material particles with electrolytes and inltrating the electrolytes into the porous electrode sheets using the precursor solutions were useful for obtaining dense composite electrodes with wide electrode-electrolyte contact areas, achieving high-performing all-solid-state cells. [21][22][23][24]34,35 These results are sufficient for demonstrating the advantages of the liquid-phase techniques for all-solid-state cells. To obtain a deeper understanding of liquid-phase synthesis, the reaction mechanisms in the solution and the structural changes aer removing the solvents must be claried.…”

“…A liquid-phase process for preparing the sulde-based solid electrolytes is a necessary technique to replace conventional solid-phase and vapor-phase methods. Based on the initial report on b-Li 3 PS 4 synthesized using tetrahydrofuran (THF), 11 there have been several investigations of the liquid-phase syntheses of various solid electrolytes such as b-Li 3 PS 4 , [12][13][14] Li 7 P 3 S 11 , [15][16][17][18] Li 7 P 2 S 8 I, 19,20 Li 6 PS 5 X (X ¼ Cl, Br, I, BH 4 ), [21][22][23][24][25][26] and Na 3 MS 4 (M ¼ P, Sb). [27][28][29][30][31][32][33] In particular, we have focused on the liquid-phase synthesis of argyrodite electrolytes via solutions because of their high applicability.…”

Tailoring Li6PS5Br ionic conductivity and understanding of its role in cathode mixtures for high performance all-solid-state Li–S batteries

“…8 To address these challenges, the wet chemical synthesis route based on a dissolution-reprecipitation process was proposed. [14][15][16][17][18][19] Although this solution route provides a more homogeneous electrolyte with higher repeatability compared with the mechanical milling route, it still has other issues, such as the low ionic conductivity of the final sample [18][19] and/or the application of high-toxicity solvents during the preparation process [16][17] .…”