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

The energy-power trade-off in lithium-oxygen batteries (LOBs) arises from sluggish oxygen (O₂) transport in the porous positive electrode and pore clogging by lithium peroxide (Li₂O₂). While increasing porosity enhances electrolyte accessibility and Li₂O₂ storage, it also increases electrolyte demand, compromising the overall energy density of the cell and necessitating alternative strategies to boost power capabilities without sacrificing energy density. In this study, theoretical simulations of O₂ transport reveal that reducing tortuosity by improving pore interconnectivity has a more significant impact on O₂ transport than porosity itself. Based on this insight, a freestanding graphene-based electrode with a highly interconnected macroporous network is fabricated via a non-solvent-induced phase separation approach using polyacrylonitrile (PAN) as a carbon scaffold and polyethylene oxide (PEO) as a sacrificial porogen. The selective decomposition of PEO creates spatially interconnected macropores, effectively reducing tortuosity. The resulting electrode enables LOB cells to achieve >2500 mAh g^-1 at 1.0 mA cm^-2 under lean-electrolyte conditions. Stable cycling at 4 mAh cm^-2 is maintained with only 3.25 g Ah^-1 electrolyte, and high-rate performance persists over 90 cycles at 1.5 mA cm^-2. This work demonstrates a robust strategy to simultaneously improve energy and power performance in practical LOBs through rational electrode architecture.