锂-空气电池高导电性W(Mo)-Ox负载MnxCo3–xO4催化剂的制备及其界面调控

The development of bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a bottleneck that limits the performance of secondary lithium–air batteries. Spinel MnxCo3–xO4 is a promising bifunctional electrocatalyst for Li-air batteries due to its low cost and high catalytic activity. However, the poor electronic conductivity of MnxCo3–xO4 results in the high polarization of the air electrode during the charge/discharge process, the bad cycling performance and poor rate capability of the Li-air batteries. In this project, the W(Mo)-Ox with oxygen vacancy and high electronic conductivity is used as the support for MnxCo3–xO4 to improve its electronic conductivity. Meanwhile, “the oxygen buffering effect” provided by the oxygen vacancy in W(Mo)-Ox can improve the electrocatalytic activity of MnxCo3–xO4 for both the ORR and OER. The highly reactive surface/interface of the MnxCo3–xO4/W(Mo)-Ox composites will be constructed by tailoring the interface between MnxCo3–xO4 and W(Mo)-Ox. This will promote the effective formation and decomposition of Li2O2，decreasing the polarizaition of the air electrode and increasing the cycling performance and rate capability of the Li-air batteries. The structure change of the MnxCo3–xO4/W(Mo)-Ox and Li2O2 during the charge and discharge will be studied. The mechanism of the ORR and OER on MnxCo3–xO4/W(Mo)-Ox will be eluciated based on these studies. A new method will be provided for the improvement the activiyty of other electrocatalysts for Li-air batteries.

对氧气还原反应（ORR）和氧气析出反应（OER）具有催化活性的双功能催化剂是制约二次锂-空气电池性能的瓶颈。尖晶石MnxCo3–xO4具有低成本和高催化活性的优点，是一种最有希望的双功能催化剂。然而由于其导电性差，使锂-空气电池的充/放电极化大、循环性能和倍率特性差。本项目以含有氧空位的、高导电性金属氧化物W(Mo)-Ox作为载体制备MnxCo3–xO4/W(Mo)-Ox复合材料，提高材料的电子导电性；并利用W(Mo)-Ox中氧空位的“氧气缓冲作用”提高材料对ORR和OER的催化活性。通过调控复合材料的界面形态和结构构筑高反应活性表/界面，促进放电产物Li2O2的有效生成和分解，降低锂-空气电池的充/放电极化、提高其循环性能和倍率特性。通过研究催化剂和Li2O2的微观结构在充放电过程中的变化，阐明该复合材料对ORR和OER的催化机理，为发展锂-空气电池其它高催化活性双功能催化剂提供新途径。

针对二次锂-空气电池空气电极的氧气还原反应（ORR）和氧气析出反应（OER）的缓慢动力学的瓶颈、尖晶石氧化物催化剂导电性低以及碳载体稳定性差等问题，以含有氧空位的、高导电性金属氧化物负载尖晶石氧化物MnxCo3–xO4（0≤x≤3）制备复合材料，作为锂-空气电池的空气电极的双功能催化剂。一方面通过与导电W(Mo,Ti)-Ox复合来提高MnxCo3–xO4（0≤x≤3）的电子导电性；另一方面利用W(Mo,Ti)-Ox中的氧空位的“氧气缓冲作用”提高MnxCo3–xO4（0≤x≤3）的催化活性。对W(Mo,Ti)-Ox/MnxCo3–xO4(0≤x≤3)的界面进行调控，构筑高反应活性表/界面，促进放电产物Li2O2的有效形成和分解，从而进一步降低锂－空气电池的充/放电极化，提高电池循环性能和倍率特性。重点制备和探讨了Ti4O7/MnCo2O4、MnCo2O4/MoO2@Ni、W18O49/CoO/Co3O4/ Fe2O3等复合材料的性能。并将尖晶石氧化物拓展至FeCo2O4，含有氧空位的氧化物拓展至CeO2，制备了FeCo2O4/CeO2复合材料。还特别制备了含氧空位的氧化物MoOx保护碳纳米管，即MoOx/CNT复合材料。系统研究了所制备复合材料的微观结构与其宏观电化学性能之间的关系。研究结果表明，以含有氧空位的、高导电性金属氧化物与尖晶石氧化物复合可以显著提高尖晶石氧化物的双功能催化活性，其高的催化活性主要来自两种氧化物间的协同电子调控作用。深入探讨并阐明所研究复合材料在有机电解液中对ORR和OER的催化机理，结合密度泛函理论（DFT）计算，提出带有氧缺陷型的氧化物对Li和O2发生反应生成LiO2中间产物稳定性以及最终产物Li2O2形成和分解具有重要影响。项目发展了一种制备锂-空气电池的空气电极的双功能催化剂的新方法，研究结果也为提高锂-空气电池的其它金属氧化物催化剂的催化活性和循环性能提供了新的思路和途径。