Stepwise Activation-Guided Zn Deposition for Ultra-High Capacity in Flowless Zn-Br Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Flowless Zn-bromine batteries (FL-ZBBs) offer advantages over conventional flow batteries but face challenges in zinc utilization and areal capacity.
• Zinc electrodes in FL-ZBBs often exhibit top-plating and dendrite accumulation, hindering reversible zinc plating/stripping and overall performance.

Purpose of the Study:

• To develop a novel electrode architecture for FL-ZBBs that enables uniform zinc deposition and enhances practical feasibility.
• To overcome limitations in zinc utilization and achieve ultra-high areal capacity in FL-ZBBs.

Main Methods:

• Introduction of a stepwise activation (SWA) electrode architecture.
• Design involves insulating porous membranes separating stacked carbon fiber (CF) layers with controlled zinc penetration.
• Evaluation of SWA electrode performance in FL-ZBBs under high current cycling.

Main Results:

• The SWA electrode guides top-plating-free, bottom-to-top sequential zinc deposition.
• FL-ZBBs with SWA electrodes demonstrated stable high Coulombic and energy efficiencies over 10,000 cycles at 20 mA cm⁻².
• Achieved stable cycling of 100 mAh cm⁻² in FL-ZBBs, maximizing ZnBr₂ utilization to ~33%.

Conclusions:

• The SWA electrode design effectively addresses zinc plating issues in FL-ZBBs.
• This simple and scalable approach enables high-capacity operation and broad applicability in flowless batteries and other metal-deposition-limited systems.