Ultrathin Zn-free anode based on Ti₃C₂T_x and nanocellulose enabling high-durability aqueous hybrid Zn-Na battery with Zn²⁺/Na⁺ co-intercalation mechanism

With low cost and high safety, aqueous zinc-based batteries have received considerable interest. Nevertheless, the excess utilization of zinc metal in the anodes of these batteries reduces energy density and increases costs. Herein, an ultrathin electrode of approximately 6.2 μm thick is constructed by coating Ti₃C₂T_x/nanocellulose hybrid onto a stainless steel foil. This electrode is used as the Zn-free anode for aqueous hybrid Zn-Na battery, in which, a concentrated electrolyte is used to improve electrochemical reversibility. The Ti₃C₂T_x/nanocellulose coating is found to improve the electrolyte wettability, facilitate desolvation process of hydrated Zn²⁺ ions, lower nucleation overpotential, improve zinc plating kinetics, guide horizontal zinc plating along the Zn(002) facet, and inhibit parasitic side reactions. It is also found that the Na₃V₂(PO₄)₃ cathode material adopts a highly reversible Zn²⁺/Na⁺ co-intercalation charge storage mechanism in this system. Thanks to these benefits, the assembled hybrid Zn-Na battery exhibits excellent rate capability, superior cyclability, and good anti-freezing ability. This work provides a new concept of electrode design for electrochemical energy storage.