Research Of The BCN-Based Composites As Cathode Catalysts For Lithium-air Batteries

Considering the demand on a superior energy storage technology in the modern society,rechargeable Li-air batteries have triggered extensive attention and exploration beyond traditional Li-ion batteries,and are regarded as a promising candidate for popularizing in electric vehicles due to their ultrahigh theoretical energy density.However,Li-air batteries still face a great many of plagued challenges which include poor cyclability,high overpotential,decaying capacity.For the above-mentioned reasons,it is not negligible to explore valid and available electrocatalysts as key enablers for Li-air batteries.In this article,we selected BCN nanotubes as the research object.And the X-ray diffraction?XRD?,the X-ray photoelectron spectroscopy?XPS?and the scanning electron microscopy?SEM?were applied to the material characterizations for materials prepared.Furthermore,the catalytical activities in aqueous alkaline electrolyte and electrochemical performances based on Li-air battery were also investigated.In the first section of this article,NCO@BCNNTs nanocomposite was synthesized via facile hydrothermal treatment,and initially employed as a bifunctional electrocatalyst for oxygen cathode in rechargeable Li-air batteries.Series of characterization and testing were carried out.The results show that the as-assembled Li-air batteries exhibited lower overpotential?⁰.96 V?,a higher discharge capacity(9823 m Ah g^-1) and better cycling stability?³20 cycles?than single material.In order to clarify the catalytic mechanism,DFT analysis was performed.The calculation results indicated that both electron conductivity and activity of the composite catalyst were increased.Hence,more charged sites and defect sites were produced,which can facilitate the formation and decomposition of reversible Li₂O₂.In the present work,the importance of the rational design of the bifunctional catalyst and its promising application in Li-air battery were highlighted.In another section,through in situ deposition and growth of IrO₂nanoparticles on graphitic carbon nitride sheets,an IrO₂@BCNNTs composite was synthesized and compared with C-IrO₂@BCNNTs material as the catalyst for non-aqueous lithium-air battery.As a result,the IrO₂@BCNNTs composite exhibits higher catalytic activity for an air cathode than the C-IrO₂@BCNNTs composite for both the ORR and OER.The IrO₂@BCNNTs composite also exhibits better performance in a Li-air battery than BCN catalysts,which includes superior discharge capacity,low charge overpotential and high cycle stability.