The large-scale commercial application of lithium-oxygen batteries (LOBs) is overwhelmed by the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) associated with insoluble and insulated Li2 O2 . Herein, an elaborate design on a highly catalytic LOBs cathode constructed by N-doped carbon nanotubes (CNT) with in situ encapsulated Co2 P and Ru nanoparticles is reported. The homogeneously dispersed Co2 P and Ru catalysts can effectively modulate the formation and decomposition behavior of Li2 O2 during discharge/charge processes, ameliorating the electronically insulating property of Li2 O2 and constructing a homogenous low-impedance Li2 O2 /catalyst interface. Compared with Co/CNT and Ru/CNT electrodes, the Co2 P/Ru/CNT electrode delivers much higher oxygen reduction triggering onset potential and higher ORR and OER peak current and integral areas, showing greatly improved ORR/OER kinetics due to the synergistic effects of Co2 P and Ru. Li-O2 cells based on the Ru/Co2 P/CNT electrode demonstrate improved ORR/OER overpotential of 0.75 V, excellent rate capability of 12 800 mAh g-1 at 1 A g-1 , and superior cycle stability for more than 185 cycles under a restricted capacity of 1000 mAh g-1 at 100 mA g-1 . This work paves an exciting avenue for the design and construction of bifunctional catalytic cathodes by coupling metal phosphides with other active components in LOBs.
Keywords: Li2O2; cathodes; lithium-oxygen batteries; metal phosphides; oxygen reduction reaction.
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