Investigating the Role of a P(VDF−TrFE) Ferroelectric Separator in Li‐Metal Pouch Cells using Electrochemical Impedance Spectroscopy

This study pioneers the use of P(VDF−TrFE) as a ferroelectric copolymer for mitigating dead lithium formation in Li-metal anodes with carbonate electrolytes. A porous coating is prepared on a commercial polypropylene separator via a novel use of Non-solvent Induced Phase Separation (NIPS). Pouch cells with a high-loading cathode, reveal superior performance, exhibiting slower capacity fading and the weakest impedance growth.

Abstract

This study explores the efficacy of employing P(VDF−TrFE), a ferroelectric copolymer, to mitigate the formation of dead lithium in Li-metal anodes when paired with carbonate electrolytes. Employing non-solvent induced phase separation (NIPS), self-standing membranes and coatings on polypropylene (PP) separators were prepared, both demonstrating a homogenous cellular pore structure and excellent ionic conductivity. Rigorous evaluation in pouch cell formats, featuring a thin Li-metal anode (50 μm), a high-loading NMC532 cathode (3 mAhcm⁻²), and a carbonate electrolyte, reveals the superior performance of cells with P(VDF−TrFE)-coated PP separators. Notably, these cells exhibit slower and more consistent capacity fading, as well as the weakest increase in impedance, as evidenced by Electrochemical Impedance Spectroscopy (EIS) investigations. This work underscores the promising role of P(VDF−TrFE) as a key material for addressing challenges associated with dead lithium, offering valuable insights for advancing Li-metal battery technologies in practical applications.

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