For Li-O2 batteries, a challenge still remains to achieve high discharge capacity and easy decomposition of the discharge product (Li2O2) simultaneously. In this work, conformal growth of thin-layered Li2O2 on Co3O4 nanowire arrays (Co3O4 NAs) during discharge is realized through the cocatalytic effect of solid/immobile Co3O4 NAs and mobile Pd nanocrystals (Pd NCs), rendering easy decomposition of Li2O2 during recharge. Meanwhile, high discharge capacity is also ensured with unique array-type design of the catalytic cathode despite the surface growth mode of Li2O2. The Li-O2 cells can deliver a high discharge capacity of 5337 mAh g-1 and keep a stable cycling of 258 cycles at a limited capacity of 500 mAh g-1. The achievement of excellent electrochemical performance is attributed to the highly efficient cocatalytic ability of Co3O4 NAs and Pd NCs as well as the desirable array-type architecture of the catalytic electrode free of carbon and binder. The cocatalytic mechanism of Co3O4 NAs and Pd NCs is clarified by systematic electrochemical tests, microstructural analyses, and ζ-potential measurements.
Keywords: binder/carbon free; cobalt oxide arrays; cocatalysis; controlled Li2O2 growth; lithium−oxygen batteries; palladium nanocrystals.