Immobilizing zwitterionic molecular brush in functional organic interfacial layers for ultra-stable Zn-ion batteries

A breakthrough study in Nano-Micro Letters led by Limeng Sun, Xianjun Cao and Hao Liu presents an organic-assist pre-construction (OAPC) strategy that grafts a densely packed, imidazolium-propane-sulfonate (IPS) zwitterionic brush onto Zn anodes, yielding record-breaking stability and efficiency for next-generation aqueous Zn-ion batteries.

Why This Research Matters
• Overcoming Dendrite & HER Barriers: Bare Zn suffers from uncontrolled dendrite growth and hydrogen-evolution side reactions that limit cycle life to < 200 h at 1 mA cm^-2 and < 70 cycles in full cells.
• Enabling Grid-Scale Storage: With theoretical capacity of 820 mAh g^-1 and intrinsic safety, Zn metal remains the most cost-effective anode—provided interfacial stability can be delivered at industrial current densities (> 50 mA cm^-2).

Innovative Design & Mechanisms
• Functional Organic Interfacial Layer (OIL-IPS@Zn): A one-step OAPC process in PC-water-IPS electrolytes forms a 23 nm-smooth, densely packed organic SEI that immobilizes IPS in a directional cation-out/anion-in zwitterionic brush.
• Theoretical & Experimental Synergy: DFT shows Zn²⁺ adsorption energy drops to −2.26 eV (vs −1.45 eV on bare Zn); MD simulations reveal a 62 % reduction in desolvation barrier (0.30 vs 0.79 eV), accelerating ion transport while suppressing HER.
• Scalable Electrolyte Compatibility: After pre-construction, the modified anode operates seamlessly in standard 0.5 M Zn(OTf)₂ aqueous electrolyte—bridging organic SEI robustness with aqueous cost/safety advantages.

Applications & Future Outlook
• Symmetric Cells: 3500 h at 1 mA cm^-2 / 1 mAh cm^-2 and 3200 h at 50 mA cm^-2 / 10 mAh cm^-2—state-of-the-art among reported Zn||Zn cells.
• Full-Cell Validation: Paired with H₂V₃O₈ cathode, the OIL-IPS@Zn||H₂V₃O₈ system delivers 99.9 % plating/stripping CE and > 7000 cycles at 10 A g^-1 with 91 % retention—outperforming bare-Zn cells that fade within 70 cycles.
• Commercial Roadmap: The OAPC process is compatible with roll-to-roll electrode manufacturing and requires only ppm-level IPS additive, promising direct integration into existing Zn-ion production lines.

Conclusions
By embedding an immobilized zwitterionic molecular brush within a functional organic interfacial layer, this work redefines the stability envelope of Zn metal anodes. The resulting OIL-IPS@Zn platform not only suppresses dendrites and parasitic reactions across extreme current densities but also establishes a scalable pathway for ultra-long-life aqueous Zn-ion batteries critical for renewable-energy storage.