Three-Dimensional WCoFe Ternary Metal Oxide Nanowire Network as a Carbon-Free Cathode Catalyst for High-Performance Li–O2 Batteries

Rechargeable aprotic Li–O2 batteries own great potential in large-scale energy storage and electric vehicles due to high theoretical energy density. However, batteries utilizing the carbon-based cathodes are unstable because the parasitic reaction with discharge products usually leads to the decomposition of carbon and formation of insulating byproducts, thus greatly decreasing the efficiency and cycling stability of batteries. Herein, we report a class of WCoFe@Ni cathodes based on Magnéli phase sub-stoichiometric W18O49 and amorphous cobalt/ferric oxide as carbon-free catalyst for high-performance Li–O2 batteries. The prepared cathode delivers a high discharge capacity of 5800 mAh g–1 and enhanced cycling stability (more than 400 cycles). X-ray photoelectron spectroscopy and synchrotron-based X-ray absorption spectroscopy reveal that the local coordination environments and Co/Fe electronic structures are modulated after the addition of the W element in catalysts. Furthermore, the theoretical calculation results testify that the high-valence state Fe in catalysts stabilizes the Co element at the low-valence state, which boosts the formation of Co(II)O species that is favorable for the Li2O2 decomposition. The synergistic effect among W, Co, and Fe plays a very essential role in improving the performance of Li–O2 batteries.