Preparation Of Titanium Dioxide With Oxygen Defects And Its Cathode Performance In Lithium Air Batteries

Lithium air battery is considered as the most promising secondary chemi cal power as a result of high specific capacity(3860 m Ah g^-1).But problems arisen from cathode catalysts,electrolyte and anode materials limit its application.Among them,activity and stability of cathode catalysts are of vital importance.TiO₂ is universally viewed as the most stable cathode catalysts in lithium air battery.However,its poor catalytic capability and electron conductivity lead to terrible electrochemistry performance in lithium air battery.In our work,by means of introducing oxygen defects in TiO₂ to enhance its catalytic capability,we aim to increase its performance using in lithium air battery as cathode catalysts.HF wet corrision is needed to prepare Ti nanowire arrays,then h ydrothermal in alkaline solution can accomplish the transform from Ti nanowire arrays to Ti@TiO₂ nanowire arrays.Finally,annealing Ti@TiO₂ nanowire arrays in Ar/H2 atmosphere to achieve introducing oxygen defects into Ti@TiO₂ nanowire arrays.Ti nanowire arrays offer high-speed channels for electron conductivity,and introduction of oxygen defects enhance its ORR and OER capability.Limitting voltage between 2 and 4.5 V and setting current density at 0.1 A g^-1,its specific capacity of first cycle can reach 3057 m Ah g^-1,higher than that of Ti@TiO₂ nanowire arrays with no oxygen defects(500 m Ah g^-1).The lithium air battery with Ti@TiO₂ nanowire arrays as cathode catalyst can cycle 90 times with a limit specific capacity at 1000 m Ah g^-1.The SEM result of Ti@TiO₂ nanowire arrays cycling 90 times show they still maintain the array structure,which means a good stability.Using two-step method to prepare TiO₂ powder with oxygen defects.According to different ultimate annealing atomosphere,we can obtain two samples with different oxygen defect quantity,which are named as Ar-TiO₂?Ti IV:Ti III=18?and air-TiO₂?Ti IV:Ti III=24?.Data of electrochemical test shows that limitting current density at 0.1 A g^-1,specific capacity of Ar-TiO₂ and air-TiO₂ can reach 1017 m Ah g^-1 and 936 m Ah g^-1,much higher than that of TiO₂ powder(455 m Ah·g^-1)and Ti₂O₃ powder(259 m Ah g^-1).Limitting specific capacity at 500 m Ah g^-1 and setting current density at 0.1 A g^-1,the charge platform of Ar-TiO₂ is 3.75 V and the discharge platform is 2.75 V.In same conditions,the charge platform of air-TiO₂ is 4 V and the discharge platform is 2.62 V.The lithium air battery with Ar-TiO₂ as positive electrode catalyst can cycle 37 times with a limit specific capacity at 500 m Ah g^-1.Results of various materials show that introducton of oxygen defec ts can improve catalytic capability of TiO₂.