Hierarchically Porous, Ultrathick, “Breathable” Wood‐Derived Cathode for Lithium‐Oxygen Batteries

In this work, a hierarchically porous and ultrathick “breathable” wood‐based cathode for high‐performance Li‐O 2 batteries is developed. The 3D carbon matrix obtained from the carbonized and activated wood (denoted as CA‐wood) serves as a superconductive current collector and an ideal porous host for accommodating catalysts. The ruthenium (Ru) nanoparticles are uniformly anchored on the porous wall of the aligned microchannels (denoted as CA‐wood/Ru). The aligned open microchannels inside the carbon matrix contribute to unimpeded oxygen gas diffusion. Moreover, the hierarchical pores on the microchannel walls can be facilely impregnated by electrolyte, forming a continuous supply of electrolyte. As a result, numerous ideal triphase active sites are formed where electrolyte, oxygen, and catalyst accumulate on the porous walls of microchannels. Benefiting from the numerous well‐balanced triple‐phase active sites, the assembled Li‐O 2 battery with the CA‐wood/Ru cathode (thickness: ≈700 µm) shows a high specific area capacity of 8.58 mA h cm −2 at 0.1 mA cm −2 . Moreover, the areal capacity can be further increased to 56.0 mA h cm −2 by using an ultrathick CA‐wood/Ru cathode with a thickness of ≈3.4 mm. The facile ultrathick wood‐based cathodes can be applied to other cathodes to achieve a super high areal capacity without sacrificing the electrochemical performance.