Ramsdellite-MnO₂ Regeneration via Acid-Mediated Redox Tuning toward Rechargeable Aqueous Zinc-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Environmental Science

Background:

• Spent alkaline batteries (SABs) pose environmental risks and economic challenges in recycling.
• Manganese oxides are key components in SABs, but their recovery and utilization are complex.
• Sustainable recycling strategies are needed to address waste accumulation and resource recovery.

Purpose of the Study:

• To develop a sustainable acid-modulated phase-reconstruction strategy for recovering manganese oxides from SABs.
• To synthesize and characterize the metastable ramsdellite-MnO2 (RM-R) phase.
• To investigate the structure-property relationships of RM-R for energy storage applications.

Main Methods:

• Acid-modulated phase-reconstruction of manganese oxides from SABs.
• First-principles calculations to determine Zn2+ diffusion barriers.
• Electrochemical testing of RM-R as a cathode material for hybrid energy storage.

Main Results:

• Successfully synthesized metastable ramsdellite-MnO2 (RM-R) with a unique tunneled framework.
• RM-R exhibited lower Zn2+ diffusion barriers (0.44 eV) compared to pyrolusite-MnO2 (RM-β, 0.99 eV).
• The RM-R cathode demonstrated high capacity (214.9 mA h g-1 at 0.1 A g-1) and excellent cycling stability (98% retention over 1000 cycles).

Conclusions:

• The acid-modulated strategy enables sustainable recovery of valuable manganese oxides from SABs.
• The metastable RM-R phase offers superior electrochemical performance for energy storage due to its unique structure.
• This work provides a pathway for closed-loop battery recycling and advances understanding of metastable manganese oxides.