Perovskite-Type La0.8Sr0. 2Co0. 8Fe0. 2O3 with Uniform Dispersion on Graphene As an Efficient Bi-Functional Li-O2 Battery Cathode

Abstract

With the increasing threat from the energy demand, greenhouse effect and environmental pollution, searching for new clean and rechargeable energy to replace conventional fuel energy has been our research urgency.[1] In recent years, Li-ion technology has captured the potable electronics market, invaded the power tool equipment markets because of its low cost, long cycle life and good reversibility. However, the energy density of commercial lithium-ion batteries (theoretical value is 400 Wh kg-1) is far from meeting the high energy demands of large-scale electricity storage for renewable energy.[2] Lithium oxygen (Li-O2) batteries with a theoretical energy density of 11140 Whkg-1 have been thought to be the most attractive contender in the future power tool equipment markets. Nevertheless, recent studies have demonstrated that the insulated products Li2O2 or electrolyte decomposition products would passivate the cathode which could cause very high charge-discharge overpotential. Moreover, the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) also compromise the capacity and cycle life.[3, 4] Noble metals may possess the highest bi-functional (ORR and OER) catalytic activities, but the expensive prices prevent them from large-scale applications. Therefore, it is crucial to find an efficient bi-functional and no-precious metal cathod for Li-O2 batteries.[5] Our previous work have been demonstrated that perovskite oxides La0.6Sr0.4Co0.2Fe0.8O3 (LSCF6428) is an effective and costless bi-functional catalyst in Li-O2 batteries especially for OER to reduce the charge potential. As like as the oxygen cathod of many other researchers, our cathod is composed of Ketjen black EC-600JD (KB), polyvinylidene fluoride (PVDF) and the as-prepared perovskite oxides, but the perovskite and KB partikles can’t uniformly distribute on the current collector, which can damage the performance of batteries.[6, 7] Reduced graphene oxide (rGO) have been applid as electrocatalyst and cathod to enhance the activity for ORR while still struggle poor stability during OER process.[8] Herein a bi-functional cathode composed of perovskite oxidesLa0.8Sr0. 2Co0. 8Fe0. 2O3 (LSCF8282) and rGO have been prepared and employed in Li-O2batteries. As shown in Figure 1, the perovskite particles with about 50 nm can uniformly disperse on the rGO nanoplatelets. Moreover, the composite cathod have shown both efficient OER and ORR activities accordding to the cyclic voltammetry measurements. The detailed results and specific analysis will be exhibited in the presentation. Acknowledgements: The authors would like to thank Materials Characterization Center of Huazhong University of Science and Technology for samples characterization assistance.