Nature-Inspired Tri-Pathway Design Enabling High-Performance Flexible Li-O2 Batteries

Trees have an abundant network of channels for the multiphase transport of water, ions, and nutrients. Recent studies have revealed that multiphase transport of ions, oxygen (O-2) gas, and electrons also plays a fundamental role in lithium-oxygen (Li-O-2) batteries. The similarity in transport behavior of both systems is the inspiration for the development of Li-O-2 batteries from natural wood featuring noncompetitive and continuous individual pathways for ions, O-2, and electrons. Using a delignification treatment and a subsequent carbon nanotube/Ru nanoparticle coating process, one is able to convert a rigid and electrically insulating wood membrane into a flexible and electrically conductive material. The resulting cell walls are comprised of cellulose nanofibers with abundant nanopores, which are ideal for Li+ ion transport, whereas the unperturbed wood lumina act as a pathway for O-2 gas transport. The noncompetitive triple pathway design endows the wood-based cathode with a low overpotential of 0.85 V at 100 mA g(-l), a record-high areal capacity of 67.2 mAh cm(-2), a long cycling life of 220 cycles, and superior electrochemical and mechanical stability. The integration of such excellent electrochemical performance, outstanding mechanical flexibility, and renewable yet cost-effective starting materials via a nature-inspired design opens new opportunities for developing portable energy storage devices.