Issue 5, 2024

A flexible solid-state electrolyte based on comb-like PEG-functionalized covalent organic frameworks for lithium metal batteries

Abstract

Solid-state batteries have great potential for increased safety and energy density, but most solid-state electrolytes show relatively low ionic conductivity and can't fully meet the requirements of solid-state batteries. Herein, vinyl-functionalized covalent organic frameworks (Bt-COFs) based on a C[double bond, length as m-dash]N bond, poly(ethylene glycol) methyl ether methacrylate (PEGMA), and LiTFSI were used to prepare a composite solid polymer electrolyte via a simple in situ polymerization technique. Bt-COF can improve the ionic conductivity of polyethylene glycol (PEG)-based electrolytes by creating a fast highway for Li+ conduction along one-dimensional nanochannels through the robust network of covalent organic backbones. At the same time, the Bt-COF-modified composite solid polymer electrolyte with a variety of “lithium-friendly” elements results in the construction of a LiF-rich SEI to regulate Li plating/stripping, which can effectively reduce the growth of dendrites. It has also been shown that the introduction of Bt-COF can effectively reduce the crystallinity of PEGMA and improve the ionic conductivity of composite solid electrolytes. The Bt-COF2%-SPE with 2 wt% Bt-COF shows a high ionic conductivity of 5.3 × 10−5 S cm−1 and an excellent lithium ion transference number (tLi+) of 0.47 at room temperature. Simultaneously, the Li∥Li symmetric cell with Bt-COF2%-SPE as the electrolyte exhibits remarkable cycling stability over 450 h. Moreover, the Li∥Bt-COF2%-SPE∥LiFePO4 cell shows a high discharge specific capacity of 146.2 mA h g−1, and a capacity of 126.7 mA h g−1 is also delivered with a coulombic efficiency of 86.6% after 200 cycles at 60 °C. Thus, solid-state electrolytes based on Bt-COF show broad prospects for practical application in lithium metal batteries.

Graphical abstract: A flexible solid-state electrolyte based on comb-like PEG-functionalized covalent organic frameworks for lithium metal batteries

Supplementary files

Article information

Article type
Paper
Submitted
14 Nov. 2023
Accepted
02 Janv. 2024
First published
05 Janv. 2024

Polym. Chem., 2024,15, 454-464

A flexible solid-state electrolyte based on comb-like PEG-functionalized covalent organic frameworks for lithium metal batteries

X. Tan, Y. Tong, J. Yang, X. Du, A. Yang, A. Zhang and Q. Xu, Polym. Chem., 2024, 15, 454 DOI: 10.1039/D3PY01265D

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