Self‐supported VO2 on polydopamine‐derived pyroprotein‐based fibers for ultrastable and flexible aqueous zinc‐ion batteries

Abstract A conventional electrode composite for rechargeable zinc‐ion batteries (ZIBs) includes a binder for strong adhesion between the electrode material and the current collector. However, the introduction of a binder leads to electrochemical inactivity and low electrical conductivity, resulting in the decay of the capacity and a low rate capability. We present a binder‐ and conducting agent‐free VO 2 composite electrode using in situ polymerization of dopamine on a flexible current collector of pyroprotein‐based fibers. The as‐fabricated composite electrode was used as a substrate for the direct growth of VO 2 as a self‐supported form on polydopamine‐derived pyroprotein‐based fibers (pp‐fibers@VO 2 (B)). It has a high conductivity and flexible nature as a current collector and moderate binding without conventional binders and conducting agents for the VO 2 (B) cathode. In addition, their electrochemical mechanism was elucidated. Their energy storage is induced by Zn 2+ /H + coinsertion during discharging, which can be confirmed by the lattice expansion, the formation of by‐products including Zn x (OTf) y (OH) 2 x − y · n H 2 O, and the reduction of V 4+ to V 3+ . Furthermore, the assembled Zn//pp‐fibers@VO 2 (B) pouch cells have excellent flexibility and stable electrochemical performance under various bending states, showing application possibilities for portable and wearable power sources.