Interconnected Hierarchically Porous Graphene-Based Membrane Electrode for High-Power and Long-Cycle Lithium-Oxygen...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-oxygen batteries (LOBs) face energy-power trade-offs due to slow oxygen transport and pore clogging.
• Increasing electrode porosity can worsen energy density by increasing electrolyte demand.

Purpose of the Study:

• To investigate strategies for improving oxygen transport in LOB electrodes.
• To develop an electrode architecture that enhances both energy and power density without compromising electrolyte efficiency.

Main Methods:

• Theoretical simulations of oxygen transport in porous electrodes.
• Fabrication of a freestanding graphene-based electrode using a non-solvent-induced phase separation method with polyacrylonitrile (PAN) and polyethylene oxide (PEO).
• Selective decomposition of PEO to create interconnected macropores and reduce tortuosity.

Main Results:

• Theoretical simulations indicated that reducing tortuosity via pore interconnectivity is more critical than porosity for oxygen transport.
• The fabricated graphene electrode exhibited a highly interconnected macroporous network.
• LOB cells with the new electrode achieved over 2500 mAh g⁻¹ at 1.0 mA cm⁻² under lean electrolyte conditions.
• Stable cycling at 4 mAh cm⁻² was achieved with minimal electrolyte (3.25 g Ah⁻¹).
• High-rate performance was maintained over 90 cycles at 1.5 mA cm⁻².

Conclusions:

• Reducing electrode tortuosity through enhanced pore interconnectivity is a key strategy for improving LOB performance.
• The developed graphene electrode architecture effectively addresses the energy-power trade-off in LOBs.
• This approach offers a viable pathway for enhancing energy and power density in practical LOB applications.