Research On Cathode Materials And Solution Phase Catalyst Of Lithium Air Battery

Lithium-air battery,whose energy density can reach 11586 Wh/kg,as the highest theoretical energy density,at present.Lithium-air battery becomes a good promsing system in lithium battery,that people have more and more demand in high energy density.Although the theoretical energy is extremely high,the application of lithium-air battery is still challenging,especially,the secondary lithium-air battery.Such as,a huge different between the practical energy density and theoretical energy density,meanwhile the cycling life still limits its practicality.The discharge capacity is only about 5000-6000mAh/g_carbon in the commercial carbon blacks,therefore it has lower commercial value.The decomposition of solid discharge products is in the control of the electron conduction between discharge products and electrode,a solid phase catalyst still remains solid-solid interface,which increases the overpotential of charge decomposition.It is going to exacerbate the electrolyte degradation,which may produce more by-product.The increasing accumulations cannot be decomposed,leading to the death of Li-air battery.In this thesis,a good fluidity of the ionic liquid was used as the precursor,the commercial carbon black?KB?was used as a skeleton.With mixing two materials and after heating treatment,the carbon coated with nitrogen doped carbon?NC-KB?was obtained.The result of the specific surface area?BET?indicate that the complex still maintained the pore structure,and the XPS results showed that the nitrogen doped carbon coating on the carbon was mainly composed of pyridine-nitrogen and pyrrolidine-nitrogen.As a cathode material of Li-air battery,the complex can make the discharge product Li₂O₂ vertical growth,the morphology of Li₂O₂ growth become form with nanosheet-like on the electrode to slow down the Li₂O₂ cover around on electrode process.It can improve the utilization efficiency of pore structure.The discharge capacity is increasing from 7400mAh/g_carbon to 12400mAh/g_carbon under25mA/g_carbon current density.At the same time,the influence of electrolyte concentration on discharge capacity has also been significantly reduced.The pyridine nitrogen plays an important role in catalyzing the oxygen reduction reaction?ORR?in Li-air battery.Using a novel structure Co?bpp?₃?TFSI?₂?CobT?,which can be dissolved in commonly used organic electrolyte for Li-air battery such as TEGDME and DMSO.CobT as a solution phase catalyst in Li-air battery.With the cyclic voltammetry curve?CV?,it can be catalyze oxygen evolution reaction?OER?at about 4.0V.The result of Li₂O₂ decomposition shows that it has a good catalytic activity.XRD and SEM shows that Li₂O₂ is completely decomposed.Besides,we also explored the catalytic action of the decomposition of by-products in Li-air battery,including LiAC,LiOH and Li₂CO₃.A combination of XRD,FTIR and SEM,it have good catalytic activity for LiAC,LiOH,but poor catalytic activity for Li₂CO₃.Li-air battery,which has added CobT to the electrolyte,exhibited a stable discharge-charge polarization.The cycle life of Li-air battery was increased from 30 to 100 cycles at 500mAh/g_carbon.