Reviving Zn⁰ Dendrites to Electroactive Zn²⁺ by Mesoporous MXene with Active Edge Sites

Abstract

Zinc metal-based aqueous batteries (ZABs) offer a sustainable, affordable, and safe energy storage alternative to lithium, yet inevitable dendrite formation impedes their wide use, especially under long-term and high-rate cycles. How the battery can survive after dendrite formation remains an open question. Here, we pivot from conventional Zn dendrite growth suppression strategies, introducing proactive dendrite-digesting chemistry via a mesoporous Ti₃C₂ MXene (MesoTi₃C₂)-wrapped polypropylene separator. Spectroscopic characterizations and electrochemical evaluation demonstrate that MesoTi₃C₂, acting as an oxidant, can revive the formed dead Zn⁰ dendrites into electroactive Zn²⁺ ions through a spontaneous redox process. Density functional theory reveals that the abundant edge-Ti-O sites in our MesoTi₃C₂ facilitate high oxidizability and electron transfer from Zn⁰ dendrites compared to their in-plane counterparts. The resultant asymmetrical cell demonstrates remarkable ultralong cycle life of 2200 h at a practical current of 5 mA cm^-2 with a low overpotential (<50 mV). The study reveals the unexpected edge effect of mesoporous MXenes and uncovers a new proactive dendrite-digesting chemistry to survive ZABs, albeit with inevitable dendrite formation.