Dual Polarization in Extended π-Conjugated Zwitterionic COF Facilitates Li+ Aligned Transportation for High Performance Solid-State Lithium-Metal Batteries

Abstract

Rational design of covalent organic frameworks (COFs) with tailored topology and multipolar characteristics offers a promising avenue for developing advanced composite electrolytes in high-rate solid-state lithium-metal batteries (SLMBs). Herein, we report an extended π-conjugated zwitterionic COF (QZwiCOF) that innovatively modulates the microstructure of PVDF-HFP to enable aligned Li⁺ transport. The unique dual polarization induced by enhanced intramolecular charge transfer in QZwiCOF maximizes PVDF-HFP's dipole moment and structural regularity. Coupled with the amphiphilic nanochannel of QZwiCOF that provides Li⁺-selective conduction, the resulting QZwiCOF-based composite electrolyte (ZiCP CPE) with merely 3 wt% QZwiCOF achieves enhanced ionic conductivity (σ = 3.44×10^-4 S cm^-1), high Li⁺ transference number (t_Li⁺ = 0.56), improved mechanical and thermal stability. Consequently, a Li||NCM811 cell with ZiCP CPE achieves excellent rate performance, which delivers a specific capacity of 145 mAh g^-1 at 3.0 C, much higher than that of PVDF-HFP SPE (51 mAh g^-1). Notably, even under 80 °C, 6.0 C, it retains a capacity of 96 mAh g^-1 after 200 cycles while that with PVDF-HFP SPE experiences a short circuit within 50 cycles, highlighting its potential for thermally resilient high-rate SLMBs. This work provides a molecular-level design strategy for engineering high-performance CPEs through zwitterionic COF-mediated ion channel regulation.