Self-assembled supramolecular interfaces enable stable and high-rate zinc anodes for aqueous hybrid supercapacitors

A research team led by Professor Feiyu Kang from Tsinghua University and Professor Liubing Dong from Jinan University has made a breakthrough in zinc-ion hybrid supercapacitor (ZHS) technology by engineering a novel zinc anode interface using supramolecular electrolyte additives. Published in Nano-Micro Letters, their work demonstrates a scalable and highly effective strategy to simultaneously improve the cycling stability and reaction kinetics of zinc anodes—longstanding barriers to realizing practical, high-performance aqueous ZHS systems.

Why This Interface Matters

• Stabilizes Zinc Anodes: The supramolecule-modified interface delivers outstanding electrochemical reversibility, achieving a Coulombic efficiency of 99.7% and extending the operational lifetime of Zn//Zn symmetric cells by 30 times compared to conventional electrolytes.
• High-Rate Capability: The engineered interface supports rapid zinc plating/stripping and enables stable cycling at current densities up to 10 mA cm^-2 for over 2400 cycles.
• 20,000-Cycle Supercapacitors: The resulting ZHS devices exhibit ultralong lifespan (20,000 cycles) and superior rate performance, offering a viable solution for future grid-level and wearable energy storage systems.

Design Strategy: Self-Assembled Interconnecting SC Supramolecules

The key innovation lies in introducing a sulfobutyl-grafted β-cyclodextrin (SC) supramolecule as a trace additive in ZnSO₄ electrolyte. These supramolecules:

• Spontaneously Adsorb onto zinc surfaces due to strong affinity with metal zinc.
• Self-Assemble into an interconnecting molecular layer via mutual attraction between their electron-rich sulfobutyl groups and electron-deficient cyclodextrin cavities.
• Form a Stable Interphase that anchors to the zinc surface, resists desorption, and creates a robust, uniform deposition interface.

This interconnecting molecular interface acts as a multifunctional layer that suppresses corrosion and dendrite growth while enhancing Zn²⁺ transport and deposition uniformity.

Mechanistic Insights

• Solvation Shell Engineering: SC supramolecules partially replace water and sulfate ions in the primary Zn²⁺ solvation shell, decreasing water-induced parasitic reactions and promoting faster Zn²⁺ desolvation.
• Hydrogen Bond Disruption: SC molecules weaken bulk hydrogen-bond networks, mitigating hydrogen evolution reactions that normally corrode the anode.
• Ion Selectivity: The interior cavity of the SC molecule traps sulfate anions, effectively raising the Zn²⁺ transference number from 0.30 to 0.83, enhancing selective ion transport.

Theoretical calculations (DFT and MD simulations) reveal that the SC–Zn²⁺ binding energy significantly exceeds that of water, confirming the supramolecule’s dominance in solvation coordination and interfacial stabilization.

Performance Highlights

• Dendrite Suppression: Zinc deposited in the SC-containing electrolyte displays dense, smooth morphology with minimal surface roughness, avoiding dendrite formation even at high current densities.
• Desolvation Kinetics: Activation energy for Zn²⁺ desolvation drops from 37.7 to 24.4 kJ mol^-1, facilitating faster charge/discharge processes.
• Interfacial Capacitance: Electric double-layer capacitance (EDLC) increases nearly tenfold at the interface, signaling abundant zincophilic adsorption sites provided by the SC layer.

Device-Level Application

• Coin and Pouch Cell Validation: Both Zn//AC coin cells and pouch-type ZHSs using the ZSO/SC-10 electrolyte show superior capacity retention and rate performance.
• Cycling Stability: Pouch-type ZHSs exhibit 95% capacity retention over 20,000 cycles with nearly 100% Coulombic efficiency, confirming the long-term stability of the engineered interface in practical systems.
• Broad Compatibility: The SC additive also improves performance in Zn//VO₂ zinc-ion batteries (ZIBs), proving its adaptability to multiple zinc-based electrochemical systems.

Future Outlook

This study introduces a scalable, low-cost, and chemistry-driven solution for stabilizing zinc anodes in aqueous energy storage devices. By leveraging the self-assembling nature and functional versatility of SC supramolecules, the researchers present a new paradigm in electrolyte–electrode interfacial engineering. The interconnecting molecule–metal interface strategy not only improves zinc anode performance across the board, but also provides a blueprint for designing other functional supramolecular systems for energy storage applications.

Stay tuned for further innovations from Professors Kang and Dong’s teams as they continue to redefine zinc-based energy storage through molecular-level interface design！