Boosting Magnesium Storage Performance of π-Conjugated Polyimide Cathodes Through Synergistic Molecular and...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Magnesium metal batteries (MMBs) promise low cost, safety, and high energy density.
• Key challenges include finding cathodes for reversible Mg2+ storage and overcoming cathode-electrolyte incompatibilities.

Purpose of the Study:

• To demonstrate fast and durable Mg storage in MMBs by coupling molecularly engineered polyimide (PI) cathodes with tailored electrolytes.
• To investigate the influence of electrolyte composition and PI structure on Mg storage performance.

Main Methods:

• Systematic evaluation of two PIs (NUPI and PUPI) in chloride-containing and chloride-free electrolytes.
• Utilized operando/ex situ spectroscopy and theoretical calculations to confirm the redox mechanism.
• Incorporated a graphene oxide-modified separator for enhanced performance.

Main Results:

• Chloride-free electrolytes with weakly coordinating anions facilitate reversible enolization and suppress side reactions.
• NUPI cathodes exhibit enhanced Mg2+ transport and interfacial charge transfer due to stronger π–π stacking and ordered structures.
• The NUPI cathode achieved 175 mAh g-1 at 50 mA g-1 with ultralow capacity fading (0.05% per cycle over 1000 cycles at 500 mA g-1).

Conclusions:

• A molecular-electrolyte co-design strategy using carbonyl polymer chemistry enables high-rate, durable MMBs.
• Reversible enolization is the dominant redox mechanism in these PI cathodes.
• This approach offers a pathway for developing next-generation MMBs.