Ion-Sieving Separator Functionalized by Natural Mineral Coating toward Ultrastable Zn Metal Anodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc-ion batteries (AZIBs) offer eco-friendly, safe, and cost-effective large-scale energy storage.
• Zinc dendrite growth and side reactions hinder the practical application of AZIBs.

Purpose of the Study:

• To develop a functionalized Janus separator for AZIBs to overcome dendrite formation and side reactions.
• To improve Zn²⁺ ion transport and deposition behavior in AZIBs.

Main Methods:

• Fabrication of a Janus separator by coating halloysite nanotubes (HNTs) onto a glass fiber (GF) substrate.
• Characterization of the HNT-GF separator's ion-sieving properties and interfacial ion-comb effect.
• Evaluation of Zn anode plating/stripping performance and full cell cycling stability.

Main Results:

• The HNT-GF separator exhibits an ion-sieving property due to the electronegativity difference of HNTs, achieving a high Zn²⁺ transference number (t_Zn = 0.71).
• The separator promotes uniform Zn²⁺ deposition and reduces nucleation overpotential, enabling an ultralong Zn anode plating/stripping life of 3000 hours.
• AZIB full cells with the HNT-GF separator demonstrate ultrastable cycling, retaining 93.4% capacity after 1000 cycles at 2 A g^-1.

Conclusions:

• The functionalized Janus separator effectively addresses key challenges in AZIBs, namely Zn dendrite growth and poor ion flux.
• This separator design significantly enhances the electrochemical performance and cycle life of AZIBs.
• The study presents a facile and effective strategy for modifying separators to advance AZIB technology for practical energy storage applications.