Suppression of Dehydrofluorination Reactions of a Li0.33La0.557TiO3‑Nanofiber-Dispersed Poly(vinylidene fluoride-co-hexafluoropropylene) Electrolyte for Quasi-Solid-State Lithium-Metal Batteries by a Fluorine-Rich Succinonitrile Interlayer

• Published in: ACS applied materials & interfaces Vol. 15; no. 12; pp. 15429 - 15438
• Main Authors: Rath, Purna Chandra, Liu, Ming-Song, Lo, Shih-Ting, Dhaka, Rajendra S., Bresser, Dominic, Yang, Chun-Chen, Lee, Sheng-Wei, Chang, Jeng-Kuei
• Format: Journal Article
• Language: English
• Published: American Chemical Society 29.03.2023
• Subjects: Energy, Environmental, and Catalysis Applications; composite solid electrolyte; morphology effects; polymer decomposition; interface modification layer; electrospinning
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.2c22268

Solid-state lithium-metal batteries have great potential to simultaneously achieve high safety and high energy density for energy storage. However, the low ionic conductivity of the solid electrolyte and large electrode/electrolyte interfacial impedance are bottlenecks. A composite solid electrolyte (CSE) that integrates electrospun Li0.33La0.557TiO3 (LLTO) nanofibers, poly­(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), and lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI) is fabricated in this work. The effects of the LLTO filler fraction and morphology (spherical vs fibrous) on CSE conductivity are examined. Additionally, a fluorine-rich interlayer based on succinonitrile, fluoroethylene carbonate, and LiTFSI, denoted as succinonitrile interlayer (SNI), is developed to reduce the large interfacial impedance. The use of SNI rather than a conventional ester-based interlayer (EBI) effectively decreases the Li//CSE interfacial resistance and suppresses unfavorable interfacial side reactions. The LiF- and CF x -rich solid electrolyte interphase (SEI), derived from SNI, on the Li metal electrode, mitigates the accumulation of dead Li and excessive SEI. Importantly, dehydrofluorination reactions of PVDF-HFP are significantly reduced by the introduction of SNI. A symmetric Li//CSE//Li cell with SNI exhibits a much longer cycle life than that of an EBI counterpart. A Li//CSE@SNI//LiFePO4 cell shows specific capacities of 150 and 112 mAh g–1 at 0.1 and 2 C (based on LiFePO4), respectively. After 100 charge–discharge cycles, 98% of the initial capacity is retained.