Superdry poly(vinylidene fluoride-co-hexafluoropropylene) coating on a lithium anode as a protective layer and separator for a high-performance lithium-oxygen battery

Ting-Nan Hsia; Hsin-Chun Lu; Yu-Chih Hsueh; Selvaraj Rajesh Kumar; Chien-Sheng Yen; Chun-Chen Yang; Shingjiang Jessie Lue

doi:10.1016/j.jcis.2022.06.172

Superdry poly(vinylidene fluoride-co-hexafluoropropylene) coating on a lithium anode as a protective layer and separator for a high-performance lithium-oxygen battery

J Colloid Interface Sci. 2022 Nov 15:626:524-534. doi: 10.1016/j.jcis.2022.06.172. Epub 2022 Jul 3.

Authors

Ting-Nan Hsia¹, Hsin-Chun Lu², Yu-Chih Hsueh¹, Selvaraj Rajesh Kumar¹, Chien-Sheng Yen¹, Chun-Chen Yang³, Shingjiang Jessie Lue⁴

Affiliations

¹ Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan City 333, Taiwan.
² Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan City 333, Taiwan; Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Keelung City 204, Taiwan.
³ Department of Chemical Engineering and Battery Research Center of Green Energy, Ming Chi University of Technology, New Taipei City 243, Taiwan.
⁴ Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan City 333, Taiwan; Department of Safety, Health and Environment Engineering, Ming Chi University of Technology, New Taipei City 243, Taiwan; Division of Joint Reconstruction, Department of Orthopedics, Chang Gung Medical Center at Linkou, Taoyuan City 333, Taiwan. Electronic address: jessie@mail.cgu.edu.tw.

PMID: 35809441
DOI: 10.1016/j.jcis.2022.06.172

Abstract

In this study, a dense polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) coating is fabricated on a lithium (Li) anode sheet, which acts as a synergistic protective layer and electrolyte separator for Li-oxygen (Li-O₂) batteries. This thin coating is dried through slow solvent evaporation and vacuum drying methods. The solvent-free, dense PVDF-HFP coating has a thickness of 45 µm and can absorb 62% of electrolyte. The battery containing the PVDF-HFP coating demonstrates a maximum peak power density of 3 mW cm^-2, significantly higher than that of the battery with the PVDF coating (0.8 mW cm^-2) but lower than that without coating (equipped with a commercial glass fiber separator, 7.3 mW cm^-2). However, the PVDF-HFP coating enables the Li-O₂ battery to reach a capacity of 4400 mA h g^-1, much higher than that without the coating (glass fiber separator, 850 mA h g^-1). The symmetric Li-Li cells further confirm steady and low overpotentials using the anode coating at a high current density of 1.0 mA cm^-2, indicating stable Li plating/stripping process. The PVDF-HFP-coated battery has a longer cycling lifetime (1700 h) than those with the PVDF coating (120 h) and a glass fiber separator (670 h). The Raman spectra show that there are lithium compounds (mainly lithium hydroxide) and residual PVDF-HFP on the aged anode surface. The dense PVDF-HFP coating on the Li anode plays dual roles: it creates a strong protective layer for stabilizing the solid-electrolyte interface (in the solid phase), and acts as a separator for modulating the Li metal deposition and stripping behaviors in liquid electrolyte.

Keywords: Aged lithium anode; Anode protective layer; Cycling stability; Dendrite formation; Lithium metal rechargeable batteries.