Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries

Bingyi Ma; Lei Zhong; Sheng Huang; Min Xiao; Shuanjin Wang; Dongmei Han; Yuezhong Meng

doi:10.3390/molecules29081759

Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries

Molecules. 2024 Apr 12;29(8):1759. doi: 10.3390/molecules29081759.

Authors

Bingyi Ma¹, Lei Zhong¹, Sheng Huang², Min Xiao², Shuanjin Wang², Dongmei Han^{1

2}, Yuezhong Meng^{1

2

3

4}

Affiliations

¹ School of Chemical Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China.
² The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China.
³ Institute of Chemistry, Henan Academy of Sciences, Zhengzhou 450000, China.
⁴ Research Center of Green Catalysts, College of Chemistry, Zhengzhou University, Zhengzhou 450001, China.

Abstract

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI^-) and aldehyde groups in COF-LZU1, the Li⁺ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-⁺ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO₄|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g^-1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs.

Keywords: covalent organic frameworks; lithium metal batteries; solid polymer electrolyte.

Abstract

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