Study On Nickel-base Catalyst As Lithium-oxygen Battery Cathode

In all kinds of renewable energy,chemical power source is attracting more attention for the ability of a high conversion rate,building easily and storing convenience.The energy density of lithium-oxygen batteries is more than 3500 Wh kg^-1,which is expected to replace gasoline.Because of the hopeful application,but there are multiple scientific challenges need to be conquered,such as poor capability,low-round-trip efficiency,instability of electrolyte and especially short cycle life.The main reasons as followed:1)Severe side effects occur during the discharge reactions.2)Lack of the effective catalyst.Based on the problems of the Li-O₂ batteries,we designed the catalysts in the following three aspects:1.A layered nanosphere structured NiO catalyst was successfully synthesized by hydrothermal method.The results revealed the layered nanosphere NiO exhibited excellent electrochemical performance.Moreover,the cut-off voltage of discharging attained about 2.0 V of the NiO-based Li-O₂ batteries while the specific capacity comes up to 3040 mA h g^-1.No obvious performance decline of the battery after 50cycles at the current density of 0.1 mA cm^-2 with superior specific capacity of 800 mA h g^-1 limited.X-ray photoelectron spectroscopy characterization manifest that the formation of Li₂O₂ and Li₂CO₃ during the discharge process and decomposed after charging.Herein,the layered nanosphere structured NiO catalyst is considered as excellent dual-effect catalyst.2.Pt/NiO catalyst was successfully synthesized by hydrothermal method.And the characterization of materials performance is mainly from the following two aspects:Firstly oxygen reduction reaction and oxygen evolution reaction is tested in alkaline solution and hydrogen evolution reaction is tested in acid solution.The tests results revealed that 1%Pt/NiO exhibited excellent electrochemical performance.Then1%Pt/NiO as cathode electrocatalyst of rechargeable nonaqueous Li-O₂ batteries exhibited excellent performance.the cut-off voltage of discharging attained about 2.0 V of the Li-O₂ batteries while the specific capacity comes up to 2329 mAh g^-1 and after 20 cycles the specific capacity still comes up to 900mAh g^-1.No obvious performance decline of the battery after 47 cycles at the current density of 0.1 mA cm^-2 with superior specific capacity of 800 mAh g^-1 limited.3.The CNT/NiO materials with the shape of sea urchins were prepared by hydrothermal methods.It demonstrated that the material have mesoporous.The catalytic performances test is demonstrated that the limiting current density of 2 CNT/NiO can get up to 4.676 mA cm^-2 and close to Pt/C.Electrical performance measurement is based on Li-O₂ batteries and 2 CNT/NiO materials is used as the catalytic of cathode.the specific capacity comes up to 4639 mAh g^-1 at 0.05 mA cm^-2 of the current density and the discharge voltage plateau only up to 2.64 V and cycle efficiency get to 86.2%.It shown 30th cycles at the current density of 0.1 mA cm^-2 with superior specific capacity of 500 mAh g^-1 and 800 mAh g^-1 limited.In order to study the influence of the growth for sphere NiO,layered nanospheres Ni O,microspheres Pt/NiO and urchin-like CNT/NiO materials are designed.By studying the constitutive relationship between the composition,morphology,structure,table/interface chemistry and electrochemical catalysis.It demonstrated that nickel-base material have excellent performance as the catalyst of Li-O₂ batteries and It lays a solid foundation for the application of lithium oxygen battery.