Self-Standing N-Doped Inverse Opal Carbon via Ultrafast Polymerization of Polydopamine and its High Energy Storage Capability in Li-O₂ Batteries

3D ordered N-doped carbon with an inverse opal nanostructure (cPDA-IO) is synthesized by the carbonization of polydopamine using self-assembled polystyrene as a template. The inverse opal structure provides an ideal architecture for storing the discharge product and transporting Li⁺ and oxygen. The direct current flow through the framework of the inverse opal structure, which does not contain any binder or conductive additives, decreases the electrode's electrical resistance and eliminates side effects associated with binder decomposition. The inverse opal structure made of N-doped carbon increases the catalytic activity by lowering the overpotential for the oxygen reduction reaction and oxygen evolution reaction. A Li-O₂ battery fabricated using cPDA-IO as the cathode exhibits remarkably enhanced performance, such as a high specific capacity of 43※908 mAh g^-1 _cPDA-IO with a reversibility of 99.5% as well as stable cycling performance for up to 91 cycles under the harsh conditions of 500 mA g^-1 _carbon and a curtaining capacity of 1000 mAh g^-1 _carbon. Its good electrochemical performance can be attributed to the synergistic effects of the inverse opal structure, binder-free structure, and N-doped carbon.