A New Cathode Material for a Li–O₂ Battery Based on Lithium Superoxide

Abstract

Li–O2 batteries suffer from large charge overpotentials due to the high charge transfer resistance of Li2O2 discharge products. A potential solution to this problem is the development of LiO2-based batteries that possess low charge overpotentials due to the lower charge transfer resistance of LiO2. In this report, IrLi nanoparticles were synthesized and implemented for the first time as a LiO2 battery cathode material. The IrLi nanoparticle synthesis was achieved by a temperature- and time-optimized thermal reaction between a precise ratio of iridium nanoparticles and lithium metal. Li–O2 batteries employing the IrLi-rGO cathodes were cycled up to 100 cycles at moderate current densities with sustained low cell charge potentials (<3.5 V). Various characterization techniques, including SEM, DEMS, TEM, Raman, and titration, were used to demonstrate the LiO2 discharge product and the absence of Li2O2. On the basis of first-principles calculations, it was concluded that the formation of crystalline LiO2 can be stabilized by epitaxial growth on the (111) facets of IrLi nanoparticles present on the cathode surface. These findings demonstrate that, in addition to the previously studied Ir3Li intermetallic, the IrLi intermetallic also provides a means by which LiO2 discharge products can be stabilized and confirms the importance of templating for the formation process.