Electrolyte‐Induced Interfacial ZnMn2O4 Formation on MnO2@MOF‐5 Cathodes for Ultra‐Stable Aqueous Zinc‐Ion Batteries

Why It Matters

The approach offers a scalable path to dramatically extend cycle life and energy density of aqueous zinc‑ion batteries, a key technology for low‑cost grid storage and electric mobility.

Key Takeaways

• MOF-5 confines nucleation, enabling selective ZnMn2O4 formation
• ZnMn2O4 interphase stabilizes δ‑MnO2 and boosts Zn2+ transport
• Capacity reaches 173.7 mAh g⁻¹ at 0.1 A g⁻¹
• Retains 79 mAh g⁻¹ after 5,000 cycles at 1 A g⁻¹
• Shows electrolyte‑interphase co‑design for multivalent battery stability

Pulse Analysis

Aqueous zinc‑ion batteries (AZIBs) have attracted attention for their safety and low cost, yet their commercial viability is hampered by rapid cathode degradation. Conventional MnO2 cathodes suffer from dissolution and structural collapse during repeated Zn2+ insertion, leading to capacity fade. Researchers have therefore focused on interfacial engineering to create protective layers that can accommodate volume changes while maintaining ion conductivity. The challenge lies in forming such layers uniformly and reversibly without compromising the intrinsic electrochemical activity of the host material.

In the new study, scientists introduced metal‑organic framework‑5 (MOF‑5) as a nanoconfined scaffold that directs the in‑situ formation of a ZnMn2O4 interphase. By pre‑loading Mn2+ ions in a 2 M ZnSO4 + 0.2 M MnSO4 electrolyte, the MOF‑5 surface promotes selective nucleation of ZnMn2O4, which acts as a self‑expanding, reversible host. This interphase not only shields the underlying δ‑MnO2 from dissolution but also creates fast pathways for Zn2+ migration, resulting in a high reversible capacity of 173.7 mAh g⁻¹ at low current and remarkable retention of 79 mAh g⁻¹ after 5,000 high‑rate cycles.

The implications extend beyond a single material system. Demonstrating that electrolyte composition and interfacial architecture can be co‑designed opens a versatile platform for next‑generation multivalent batteries, where stability under extreme cycling is paramount. For utilities and manufacturers seeking cost‑effective, long‑life storage solutions, such advances could accelerate the adoption of AZIBs in grid‑scale applications and electric‑vehicle platforms. Future work will likely explore scaling the MOF‑5 synthesis, integrating other cathode chemistries, and optimizing electrolyte additives to further boost energy density while preserving the ultra‑stable performance reported here.