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

Purna Chandra Rath; Ming-Song Liu; Shih-Ting Lo; Rajendra S Dhaka; Dominic Bresser; Chun-Chen Yang; Sheng-Wei Lee; Jeng-Kuei Chang

doi:10.1021/acsami.2c22268

Suppression of Dehydrofluorination Reactions of a Li_0.33La_0.557TiO₃-Nanofiber-Dispersed Poly(vinylidene fluoride-co-hexafluoropropylene) Electrolyte for Quasi-Solid-State Lithium-Metal Batteries by a Fluorine-Rich Succinonitrile Interlayer

ACS Appl Mater Interfaces. 2023 Mar 29;15(12):15429-15438. doi: 10.1021/acsami.2c22268. Epub 2023 Mar 15.

Authors

Purna Chandra Rath¹, Ming-Song Liu², Shih-Ting Lo², Rajendra S Dhaka³, Dominic Bresser^{4

5}, Chun-Chen Yang⁶, Sheng-Wei Lee², Jeng-Kuei Chang^{1

7}

Affiliations

¹ Department of Materials Science and Engineering, National Yang-Ming Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan.
² Institute of Materials Science and Engineering, National Central University, 300 Jhong-Da Road, Taoyuan 32001, Taiwan.
³ Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
⁴ Helmholtz Institute Ulm (HIU), 89081 Ulm, Germany.
⁵ Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany.
⁶ Battery Research Center of Green Energy, Ming Chi University of Technology, New Taipei City 243, Taiwan.
⁷ Department of Chemical Engineering, Chung Yuan Christian University, 200 Chung Pei Road, Taoyuan 32023, Taiwan.

PMID: 36920173
DOI: 10.1021/acsami.2c22268

Abstract

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 Li_0.33La_0.557TiO₃ (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.

Keywords: composite solid electrolyte; electrospinning; interface modification layer; morphology effects; polymer decomposition.