Highly Crystalline Flower-Like Covalent-Organic Frameworks Enable Highly Stable Zinc Metal Anodes

Abstract

Aqueous zinc (Zn) ion batteries with low cost and high safety are promising devices for grid energy storage; however, the Zn anode problems, including dendrite growth and parasitic side reactions, severely retard their practical implementation. Here, a two-dimensional covalentorganic framework (COF) coating is developed to address these issues. Under the regulation of an optimal modulator, the prepared COF (COF− H) containing rich alkynyl units in an AA-stacking mode not only features a flower-like structure but also exhibits high crystallinity, large surface area, and high stability in strong acid and base medium. Consequently, the Zn anode with this COF-based artificial interface layer greatly mitigates the surface corrosion and efficiently suppresses the growth of the Zn dendrite, which is mainly attributed to the homogeneous distribution of Zn 2+ in uniform channels and strong affinity of electron-rich sites including alkynyl, ketone, and enamine groups in COF−H toward Zn 2+ . The resulting Zn anode endows the symmetric cell with a long cycling lifetime of over 900 h at 3 mA cm −2 and promotes the cyclability of the COF@ Zn||MnO 2 full cell. This study provides insights into designing highly crystalline COFs and constructing a highly reversible Zn anode for advanced rechargeable aqueous Zn ion batteries.

Monolayer Thiol Engineered Covalent Interface toward Stable Zinc Metal Anode

“…In accordance, the bare Zn anode shows a larger total voltage hysteresis of 187 mV (154 mV for the Zn-RS anode) as disclosed by the enlarged voltage–time curves (Figure S13). The Zn-RS symmetric cell presents one of the state-of-the-art Zn metal anodes based on the cycling time, preceding reported modification measures of interface coating on Zn anodes (Figure e). ,− In addition, the effect of soaking time of Zn metal in thiol solution on electrochemical performance was also explored, where a stable Zn anode could be obtained with a reaction time of 24 h rather than the incomplete reaction time of 1 h (Figure S14). The rate capability is further evaluated in symmetric cells (Figure f), and the results show that the Zn-RS anode exhibits smaller voltage hysteresis and less fluctuation from the current density of 0.5 to 4.0 mA cm –2 compared to the bare Zn anode (Figure g).…”

Covalent organic frameworks as electrode materials for rechargeable metal‐ion batteries

“…[ 166,167 ] Benefiting from the merits of COFs as mentioned above, a growing number of studies have focused on the development of high‐performance organic electrode materials for ZIBs. [ 99,106,134,168–176 ]…”

“…[166,167] Benefiting from the merits of COFs as mentioned above, a growing number of studies have focused on the development of high-performance organic electrode materials for ZIBs. [99,106,134,[168][169][170][171][172][173][174][175][176] Khayum et al utilized a β-ketoenamine HqTp COF as the cathode material to bind Zn 2+ ions (Figure 12A). [168] Benefiting from the interlayer interaction of Zn 2+ with C=O and N-H groups, a high discharge capacity of 276.0 mAh g −1 at 125.0 mA g −1 was achieved in aqueous Zn/HqTp cells.…”

Advances in functional organic material-based interfacial engineering on metal anodes for rechargeable secondary batteries

“…Hu et al prepared zinc electrodes using a 2D high-crystallinity alkynyl-based COF (COF-H) as an artificial protective layer. 154 Due to the large number of electronrich sites (acetylene, keto and enylamine) in COF-H, Zn 2+ could be evenly distributed in 2D COF-H, which inhibited the formation of zinc dendrites and increased the corrosion resistance of Zn metal surface. Wu et al synthesized a homogeneous and dense 3D-COOH-COF protective layer with hydro-philic functional groups and microporous morphology (Fig.…”