Hydrothermal Synthesis Of Tantalum Oxides And Its Application In Li-Air Batteries

More recently,a new wave of research for metal-air batteries was raised in the academic world.Compared with most of batteries,the active cathode material of metal-air battery is oxygen,which is acquired from the environment and not stored in the interior of the cell.In the process of charge and discharge,it participates in the associated reaction of the battery by catalyzing of these catalysts on the surface of cathode.Generally,the electrolyte of metal-air batteries is KOH solution.However,lithium-air batteries usually use nonaqueous electrolytes do not join the chemical reactions when batteries work.Among batteries system,lithium-air batteries stand out by the highest theoretical specific energy?11700 Wh/kg?.Meanwhile,there are many challenges to deal with for applying to the real life such as the cathodic reaction mechanism,the stability of each battery components on a half open system,the capacity attenuation,short cycle life and so on.In order to improve the lithium-air batteries performance,scholars constantly adjust and perfect their research system especially the design of cathode catalyst materials.At present,the main materials of cathode catalysts are porous carbon materials?carbon nanotubes,graphene,etc.?,transition metal oxides?Fe₂O₃,MnO₂,Co₃O₄,etc.?,noble metal?Au-Pt/XC-72,Pt-GNS,etc.?,etc.In this work,we synthesized Ta₂O₅,rGO/Ta?MeO?₅,rGO/Ta₂O₅ nanomaterials by hydrothermal method.The morphology and structure were characterized by XRD,SEM,TEM and other test method.According to date,the Ta₂O₅ is orthorhombic and space group P21212?18?whose lattice parameters are a=6.198 ?,b=40.29 ?,c=3.888 ? and ?=?=?=90°.Sample of rGO/Ta₂O₅ owns the most specific surface area and the highest degree of reduction.As a cathode catalyst,it has the best performance comparing to several other catalysts.Its first discharge specific capacity is up to 8300 mAh/g and has 0.4 V overpotential decreased.There is no doubt that rGO/Ta₂O₅ deserves the best cycle stability even three times increased.Combined with the literature,electrode material of large surface area and high reduction degree can provide more reactive sites during charge and discharge process that is beneficial to improve the deposition quantity of discharge products and interlayer Li₂O₂ generation.So the discharge capacity was improved and the overpotential reduced which lead to a better cells cycle stability.This research shows that rGO/Ta₂O₅ composite catalyst materials will be one of the most promising cathode catalysts for lithium-air battery.In addition,we also prepared Ta₂O₅ with a graphene skeleton.We characterized and analyzed it by XRD,SEM and TEM.According to the Li-air battery tests,its first discharge specific capacity is up to 2843 mAh/g when the current density is 100 mA/g.And compared with the amorphous Ta₂O₅,it improved 30%.In contrast,Ta₂O₅ with a graphene skeleton owns a better rate capability and cycle stability.In this work,we provided a new research idea and experimental method for the metal-air cells by exploring tantalum oxide catalytic performance in Li-air batteries.