Surface charge-reinforced and ion-selective layers for stable metal zinc anode chemistry

The application of zinc (Zn) metal-based batteries is hindered by the uncontrollable thermodynamic-driven hydrogen evolution reactions and kinetic-induced dendrite growth, resulting in reduced cycling stability and premature battery failure. To tackle these challenges, we introduce a pH-mediated surface charge-reinforced and ion-selective strategy by using a facile self-assembled approach, by which cysteamine (SH-CH₂-CH₂-NH₂) molecular layers (SALs) are in situ constructed on the Zn metal surface (Zn@SCRIS-SALs). Triggered by the pH-mediated-protonation effect, these layers generate a partial positive surface (-NH₃⁺) to repel the hydrated protons and zinc-philic sites (-NH₂) for anchoring Zn²⁺. The synergistic combination of the above effects enabled highly reversible Zn metal chemistry to effectively suppress side reactions and dendrite growth. Zn@SCRIS-SALs in symmetric cells exhibited stability with an ultralong lifespan of 2500 h under a high current density of 10 mA cm⁻². The superior reversibility was further ascertained by integrating Zn@SCRIS-SALs with the I₂ cathode in full cells, which showed high-capacity retention compared to bare Zn-based cells. Furthermore, 80 mA h pouch cells assembled with Zn@SCRIS-SALs were operated over 2500 cycles at an areal capacity of 5.18 mA h cm⁻². This work offers a new platform to finely modulate the electron state of interfacial molecular layers for highly reversible aqueous Zn ion batteries. © The Royal Society of Chemistry 2024.