Electrospun Phthalocyanine-Based COF Nanofibrous Separators for Dendrite-Free Lithium Metal Batteries with Enhanced Ionic Conductivity and Thermal Stability

Abstract

It is well recognized that lithium dendrite formation within polymer-based separators severely compromises both the safety and electrochemical performance of lithium metal batteries (LMBs). To mitigate this issue, the development of separator materials that exhibit superior electrolyte wettability and high ionic conductivity is essential. In this work, a novel nanofibrous separator composed of a phthalocyanine-based covalent organic framework (Pc-COF) and polyacrylonitrile (PAN) is fabricated via electrospinning and is denoted as PAN@COF. The resulting PAN@COF separator possesses a nanochannel array architecture enriched with lithophilic C=N groups originating from the phthalocyanine-based COF, thereby promoting homogeneous Li⁺ flux distribution. Density functional theory (DFT) simulations indicate that the COF can interact with electrolyte solvent molecules to form a desolvated Li⁺ structure, thereby enabling rapid Li⁺ transport. In situ optical microscopy visually monitored the lithium dendrite deposition during cycling, underpinning the theoretical simulations and kinetic analyses. The separator exhibits exceptional ionic conductivity (1.72 mS cm^-1) and a high Li⁺ transference number (0.78). When applied in a Li||Li symmetric cell, the separator enables uninterrupted cycling stability exceeding 3200 hours at 0.2 mA cm^-2. Furthermore, the corresponding pouch cells maintain stability under extreme shear, highlighting their practical reliability. This study presents a novel strategy for developing dendrite-free lithium metal batteries, offering both significant scientific implications and promising application potential.

Graphical Abstract

Keywords

Phthalocyanine-based covalent organic frameworks / Electrospinning / Lithium metal batteries / Composite separators

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Funding

National Natural Science Foundation of China(21762019)

Natural Science Foundation of Jiangxi Province(20232BCJ22020)

RIGHTS & PERMISSIONS

Donghua University, Shanghai, China