• An O2-pressure protocol enhances mass transport and reaction kinetics, achieving ultrahigh discharge capacity (>9,000 mAh g−1) at 3,000 mA g−1.
• The pressure effect simultaneously protects Li anodes by densifying corrosion layers, addressing both cathode and anode challenges.
• A record-high cycle life of ~5,170 h (2,585 cycles) at 500 mA g−1 under continuous operation was achieved, an 11-fold improvement.
• The strategy is extendable to other gas-based batteries, offering a general approach for high-performance energy storage.