Abstract
The electrocatalytic activities of Mn3O4/C composites are studied in lithium–oxygen (Li–O2) batteries as cathode catalysts. The Mn3O4/C composites are fabricated using ultrasonic spray pyrolysis (USP) with organic surfactants as the carbon sources. The physical and electrochemical performance of the composites is characterized by X-ray diffraction, scanning electron microscopy, particle size analysis, Brunauer–Emmett–Teller (BET) measurements, elemental analysis, galvanostatic charge–discharge methods and rotating ring-disk electrode (RRDE) measurements. The electrochemical tests demonstrate that the Mn3O4/C composite that is prepared using Trition X-114 (TX114) surfactant has higher activity as a bi-functional catalyst and delivers better oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance in Li–O2 batteries because there is a larger surface area and particles are homogeneous with a meso/macro porous structure. The rate constant (kf) for the production of superoxide radical (O2•−) and the propylene carbonate (PC)-electrolyte decomposition rate constant (k) for M3O4/C and Super P electrodes are measured using RRDE experiments and analysis in the 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6)/PC electrolyte. The results show that TX114 has higher electrocatalytic activity for the first step of ORR to generate O2•− and produces a faster PC-electrolyte decomposition rate.
Highlights
Rechargeable lithium–oxygen (Li–O2) batteries are very efficient energy-storage devices and are used as power sources for electric vehicles (EV) and hybrid electric vehicles (HEV) because of their low cost, environmentally benign effects and high theoretical energy density (~3500 Wh·kg−1), which is almost nine times higher than that of current Li-ion batteries (~400 Wh·kg−1) [1,2,3,4]
A bi-functional cathode catalyst that facilitates the complete reversibility of oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) at low polarization in Li–O2 batteries is required
We present a detailed study of the Li–O2 electrochemistry of the Mn3O4/C material, using an electrolyte of 1 M LiPF6 in a propylene carbonate (PC) solvent
Summary
Rechargeable lithium–oxygen (Li–O2) batteries are very efficient energy-storage devices and are used as power sources for electric vehicles (EV) and hybrid electric vehicles (HEV) because of their low cost, environmentally benign effects and high theoretical energy density (~3500 Wh·kg−1), which is almost nine times higher than that of current Li-ion batteries (~400 Wh·kg−1) [1,2,3,4] Despite these favorable characteristics, their practical applications have still been hampered in the past decade because of their limited rate capability, poor cycling stability due to the instability of the electrode and electrolyte, and low round-trip efficiency induced by excessive polarization, resulting in a wide charge–discharge voltage gap [1,2,3,4,5,6,7,8]. This study of Li–O2 batteries focuses on Mn3O4/C catalysts
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