For High-Performance Aqueous Zinc-ion Batteries
Hebei University & Hebei Agricultural University AFM: Gradiently Distributed MCM-41 Molecular Sieve Bifunctional Separator for High-Performance Aqueous Zinc-Ion Batteries
Link: https://doi.org/10.1002/adfm.202517715
Introduction
Aqueous zinc ion batteries (AZIBs) are promising candidates for large-scale energy storage systems. However, cathode dissolution, zinc anode corrosion, and dendrite growth severely hinder their further development. This work designs a dual-functional separator with gradient-distributed MCM-41 zeolite that simultaneously stabilizes both the cathode and zinc anode. Specifically, the side with a heavy zeolite distribution reduces the desolvation energy barrier and modulates zinc ion flux, thereby suppressing the hydrogen evolution reaction (HER) and its associated side reactions while promoting uniform zinc deposition. The opposite side, featuring a light zeolite distribution and relatively dense polymer, inhibits the dissolution and shuttling of VO₂⁺, enabling stable cycling of the V₂O₅ cathode. Zn//Zn symmetric cells assembled with this bifunctional separator demonstrated a cycling life exceeding 2400 hours (1 mA cm⁻², 1 mAh cm⁻²). Full cells employing commercial V₂O₅ as the cathode material retained a high capacity of 212.5 mAh g⁻¹ after 1000 cycles at a current density of 1 A g⁻¹. This work offers a promising direction for developing functional separators that stabilize both cathodes and anodes. The research findings were published in the internationally renowned journal Advanced Functional Materials under the title “A Bifunctional Separator with Gradient Distribution of MCM-41 Zeolite for High-Performance Aqueous Zinc-ion Batteries.”
Figure 1. Schematic diagram showing how the dual-function MZS membrane stabilizes the cathode and Zn anode.
Figure 1. a) XRD pattern of MCM-41, b) TEM image, and c) HRTEM image. d) Cross-sectional SEM image of MZS. e) Laser confocal topography of MZS-U and f) MZS-D, along with g) and h) corresponding optical images. i) Contact angle of MZS-U and j) MZS-D.
Figure 2. a) Tafel plots and b) LSV curves of Zn//Zn symmetric cells using GF and MZS separators, respectively. c) Chronocurrent curves of GF and MZS at −150 mV overpotential. d) Ion conductivity and e, f) Zn²⁺ migration number comparison between MZS and GF separators. g) Rate performance of Zn//Zn symmetric cells. h) Deposition/stripping of Zn//Cu half-cells. i) Cycling stability of Zn//Zn cells with MZS and GF separators at 1 mA cm⁻² and 1 mAh cm⁻². j) Comprehensive comparison of this work with recent reports.
Figure 3. SEM images of the zinc anode after 50 cycles of contact with a) MZS-D, b) MZS-U, and c) GF. AFM images of the zinc anode after 50 cycles of contact with d) MZS-D, e) MZS-U, and f) GF. Raman spectra of the zinc anode after 50 cycles of contact with g) MZS-D, h) MZS-U, and i) GF. j) Ion distribution field simulation of MZS and k) Finite element simulation of current density field distribution for MZS.
Figure 4. a) EIS of Zn//Cu half-cells assembled with MZS and b) GF under continuous constant-current discharge at different time points. DRT analysis of Zn//Zn symmetric cells using c) MZS and d) GF separators. e) Overpotentials of Zn//Cu half-cells with MZS and GF separators. f) Activation energies under different separator conditions. g) Schematic of the in situ Raman setup. h) In situ Raman spectra at the electrolyte/zinc interface during zinc plating for MZS and i) GF separators.
Figure 5. a) XRD and b) Raman spectra of Zn anodes with different separators after 50 cycles. c) Sulfur (S) elemental content based on XPS AR+ etching analysis of cycled Zn anodes in contact with different separators. d) FTIR spectra of H₂O and fitted strong HB, medium HB, and weak HB curves e). f) Raman spectra of ν-SO₄²⁻ band and O-H stretching vibrations for 2 M ZnSO₄ and MZS. g) Structures and binding energies of MCM-41-H₂O, MCM-41-Zn²⁺, P(VDF-co-HFP)-H₂O, and P(VDF-co-HFP)-Zn²⁺. h) Electrostatic potential maps of MCM-41-H₂O and P(VDF-co-HFP)-Zn²⁺. i) Free energy of the desolvation process in the presence and absence of MCM-41 and P(VDF-co-HFP). j) Evolution of the solvation structure during Zn²⁺ desolvation in the presence of MCM-41 and P(VDF-co-HFP).
Figure 6. Permeation experiments using H-type cells equipped with a) GF and b) MZS membranes, with yellow V solution in the left chamber and colorless ZnSO₄ solution in the right chamber. CV curves c), voltage curves d), and self-discharge tests e) for the Zn//V₂O₅ full cells with GF and MZS membranes, respectively. f) Rate capability tests of Zn//V₂O₅ full cells using GF and MZS separators. g) Cycling stability test of Zn//V₂O₅ full cells under GF, MZS-UC, and MZS-UA conditions at 1 A g^(−1). h) Cycling performance of a Zn//V₂O₅ full cell with a high mass loading of 9.78 mg cm^(−2). i) Digital photograph of an LED array powered by a pouch cell using MZS.
Conclusion
This study proposes a novel gradient zeolite-distributed membrane and demonstrates its potential to simultaneously stabilize both the cathode and anode electrodes of AZIBs. Compared to conventional GF membranes, this zeolite membrane significantly enhances the electrochemical performance of AZIBs. On the anode side, the redistributed MCM-41 zeolite in MZS-D provides excellent hydrophilicity, while P(VDF-co-HFP) exhibits strong binding affinity for Zn²⁺ ions. This reduces the desolvation energy barrier, suppressing HER and byproduct formation. On the other hand, the redistributed zeolite with a loose porous structure modulates the flux, electric field, and concentration field of Zn²⁺ ions, promoting uniform zinc deposition. For the cathode side, MZS-U with redistributed MCM-41 zeolite and a dense polymer structure effectively prevents the dissolution of V-based compounds, thereby achieving a stable cathode. Through this synergistic effect, the Zn//V₂O₅ full cell retains a high capacity of 212.5 mAh g^(−1) after 1000 cycles at a current density of 1 A g^(−1), significantly outperforming conventional GF separators. This zeolite design with concentration gradient distribution paves the way for developing high-performance AZIBs, offering novel insights.
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Source: WeChat Battery Energy and Technology
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