While aqueous zinc-ion batteries (AZIBs) show great promise for safe energy storage, their practical implementation is impeded by performance issues at the Zn anode, such as parasitic side reactions, hydrogen evolution, and dendritic growth. Here, we report a fluorine-doped carbon nanofiber (FCNF) 3D coating that provides dynamic, durable protection for the zinc anode. The coating's 3D architecture, intrinsic negative charge, and hydrophobicity synergistically guide uniform zinc deposition while inhibiting parasitic reactions. More importantly, a ‘sustained supply and dynamic formation’ mechanism is realized, where C F bonds within the FCNF dynamically cleave during cycling to enable the continuous in-situ formation of a ZnF 2 layer that persistently suppresses side reactions. Consequently, symmetric cells employing FCNF-protected anodes demonstrate an operational lifetime exceeding 3400 h at a high areal capacity of 2.5 mAh cm −2 . Moreover, when assembled with an ammonium vanadate cathode, the full cell stably cycles for over 1000 cycles at 5 A g −1 , maintaining 82% of its initial capacity. This work introduces an approach that synergistically combines physical guidance and dynamic chemical repair, offering a robust solution for developing highly stable and safe metal batteries with aqueous electrolytes.
Electrically isolated metallic Zn (Zn 0 ) and electrochemically side reaction (ECSR), causes irreversible anode capacity loss and limited cycle life in zinc metal battery. However, the quantitative distinguishment between inactive metallic Zn 0 and ECSR, their formation mechanism and correlation with anode cycling reversibility have never been disclosed, limiting further anode modification design. Here, we develop an acid-assisted continuous titration-collection-gas chromatography technique (AAC-TCGC) that accurately quantify the amount of inactive Zn 0 and ECSR in anode, and discover that inactive Zn 0 accounts for the majority of Zn loss, rather than the commonly-assumed electrochemically side reaction-derived ECSR-dominant Zn anode capacity loss. Detailed component of SEI (Solid Electrolyte Interface Layer) compound is also characterized, illustrating a solvent-derived zinc oxide/hydroxide-dominant SEI that facilitates vertical/inclined thin-plate Zn deposition, but salt-derived ZnF 2 -dominant SEI that favors horizontal platelet-shaped Zn(002) deposition. Simulation results reveal a new electric resistance-derived, bottom-preferred Zn stripping mechanism that leads to abundant inactive Zn 0 formation in vertical thin-plate Zn deposition structure, but few inactive Zn 0 in dumpy platelet-shaped Zn structure. Our study provides new theories and strategies on the distinguishment, formation mechanism and structure-performance relationship of inactive Zn, important for building more efficient Zn metal battery.
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