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-O₂ 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-O₂ 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.