Metal-Phosphonate-Organic Network as Ion Enrichment Layer for Sustainable Zinc Metal Electrode with High Rate Capability.

Zinc (Zn) metal batteries could be the technology of choice for sustainable battery chemistries owing to its better safety and cost advantage. However, their cycle life and Coulombic efficiency (CE) are strongly limited by the dendritic growth and side reactions of Zn anodes. Herein, we proposed an in situ construction of a metal-phosphonate-organic network (MPON) with three-dimensional interconnected networks on Zn metal, which can act as an ion enrichment layer for Zn anodes in Zn-metal batteries. This MPON with abundant porous structure and phosphate sites possesses ion enriching properties and high Zn ²⁺ transference number (0.83), which is beneficial for enhancing Zn ²⁺ migration and self-concentrating kinetics. Meanwhile, MPON offers hydrophobicity to effectively inhibit the water-induced Zn anode corrosion. As a result, the Zn electrode exhibits superior Zn/Zn ²⁺ reversibility of over 4 months at 3 mA cm ^-2 and a high CE of 99.6 %. Moreover, the Zn/NaV ₃ O ₈  ⋅ 1.5H ₂ O and Zn/MnO ₂ full cells using ultrathin Zn anodes (10 μm) exhibit high-capacity retention of 81 % and 78 % after 1400 and 1000 cycles, respectively. This work provides a unique promise to design high-performance anode for practical Zn-metal-based batteries.
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