Donnan-Engineered Inner Helmholtz Plane Enabling Ultra-Stable Aqueous Bismuth Electrode

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Electrochemical instability at the solid-liquid interface hinders rechargeable aqueous metal batteries (RAMBs).
• Existing methods struggle to balance desired electrochemical reactions with parasitic ones at the inner Helmholtz plane (IHP).
• The Donnan effect offers principles for ion sieving and charge partitioning.

Purpose of the Study:

• To engineer a stable solid-liquid interface for RAMBs by integrating classical electrostatics with interfacial modification.
• To leverage the Donnan effect for selective ion partitioning and electron confinement at the electrode-electrolyte interface.
• To improve the cycling stability and rate capability of bismuth electrodes in RAMBs.

Main Methods:

• Phosphate anions (PO₄³⁻) were adsorbed onto a bismuth (Bi) electrode surface to create a modified IHP.
• The immobilized PO₄³⁻ established a Donnan potential to control ion flux and electron transfer.
• Electrochemical performance was evaluated, focusing on cycling stability and rate capability.

Main Results:

• The phosphate-adsorbed IHP exhibited ion and reaction sieving, enriching Na⁺ and excluding OH⁻ to favor (de)alloying over corrosion.
• The Donnan potential suppressed parasitic electron leakage and dynamically stabilized the IHP through anion chemisorption.
• The modified Bi electrode achieved excellent cycling stability (200 mAh g⁻¹ retention after 3000 cycles at 2 A g⁻¹) and ultrahigh-rate performance (134 mAh g⁻¹ at 16 A g⁻¹).

Conclusions:

• The study successfully extended the Donnan effect into electrochemistry for interfacial engineering in RAMBs.
• A universal interfacial paradigm based on charge-selective ion partitioning and electron confinement was established.
• This approach offers a transformative strategy to decouple desired electrochemical reactions from parasitic side reactions, advancing RAMB technology.