Ionic covalent organic frameworks triggered efficient synergy: Li+ de-solvation and the formation of LiF-rich interphase
Journal of Power Sources(2022)
摘要
The parasitic side reaction between the electrolyte and the lithium metal (Li0) forms an unstable heterogeneous interphase, causing the poor reversibility of Li plating/stripping. The rational design of protection layer on Li0 anode is imperative to inhibit side reactions and achieve fast Li + transport on the Li0/electrolyte interface. Herein, by firstly coordinating the bis(fluorosulfonyl)imide anion (FSI−) to the protection layer, a layer consisting of 2D ionic vinylene-linked covalent organic frameworks (ivCOF-FSI) is proposed to stabilize the Li0/electrolyte interface. As demonstrated theoretically and experimentally, the triazine group in the cationic framework is identified to promote Li+ de-solvation process while partial FSI− prefers to form LiF-rich interphase. Attributed to these superiorities, the ivCOF-FSI layer endows the Li0/electrolyte interface with high reversibility in carbonate-based electrolytes by simultaneously suppressing the side effect and achieving rapid Li+ transfer. Combined with the high stability of solid-liquid interface, the LiFePO4 full cells with ivCOF-FSI/Li anode display enhanced cyclability under a high cathode loading of 9.4 mg cm−2 and a low negative/positive capacity ratio of 5. This work provides a novel route for stabilizing the interfacial chemistry of solid-liquid interface, aiming to pave the way for the next-generation high-energy-density batteries.
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关键词
Lithium metal batteries,Covalent organic frameworks,Bis(fluorosulfonyl)imide anion,Solid–electrolyte interphase,De-solvation
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