Improved Stability of Oxysulfide Solid-State Electrolytes in Li(G3)TFSI Solvate Ionic Liquid Electrolyte

• Published in: Journal of the Electrochemical Society Vol. 171; no. 7; pp. 70529 - 70536
• Main Authors: Yersak, Thomas A., Zhang, Yubin, Hafiz, Hasnain, Pieczonka, Nicholas P. W., Gonzalez Malabet, Hernando J., Cunningham, Hayden, Cai, Mei
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 01.07.2024
• Subjects: Electrochemistry; Materials Science; oxysulfide; semi-solid battery; solid-state electrolyte; solvate ionic liquid; stability
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/ad6292

The performance of all solid-state batteries is limited by poor interfacial contact between active material and solid-state electrolyte (SSE) particles. Semi-solid batteries utilize a secondary electrolyte phase to wet the SSE/AM interface to improve cell performance. Solvate ionic liquids (SILs) are one class of liquid electrolytes under consideration for use in semi-solid batteries. This paper focuses on the Li(G3)TFSI SIL consisting of the bis(trifluoromethanesulfonyl)imide (TFSI − ) anion coupled to a [Li(G3)] + solvate cation. Sulfide SSEs are normally subject to nucleophilic attack by trigylme (G3), however, strong coordination of Li + to G3 in the [Li(G3)] + solvate cation prevents this reaction from taking place. Consequently, the stability of sulfide SSE depends on the ideal 1:1 molar ratio of G3 to TFSI, which may be difficult to maintain. We studied the chemical stability of 70Li 2 S·(30-x)P 2 S 5 ·xP 2 O 5 (x = 0, 2, 5, 10) (oxy)sulfide solid-state electrolyte in Li(G3)TFSI SIL. By physical measurement, UV–vis spectroscopy, electrochemical evaluation, X-ray photoelectron spectroscopy, and first principles calculation it is shown that increased oxygen content improves the stability of SSE in various Li(G3) x TFSI (x = 1, 2, 3, 4) liquid electrolytes. The results suggest that an oxysulfide SSE + SIL semi-solid electrolyte is a good choice for future semi-solid battery designs.