One-Step Route Synthesized Co2P/Ru/N-Doped Carbon Nanotube Hybrids as Bifunctional Electrocatalysts for High-Performance Li-O_2 Batteries

摘要

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 Li_2O_2. Herein, an elaborate design on a highly catalytic LOBs cathode constructed by N-doped carbon nanotubes (CNT) with in situ encapsulated Co2P and Ru nanoparticles is reported. The homogeneously dispersed Co2P and Ru catalysts can effectively modulate the formation and decomposition behavior of Li_2O_2 during discharge/charge processes, ameliorating the electronically insulating property of Li_2O_2 and constructing a homogenous low-impedance Li_2O_2/catalyst interface. Compared with Co/CNT and Ru/CNT electrodes, the Co2P/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 Co2P and Ru. Li-O_2 cells based on the Ru/Co2P/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.