锂空气电池用过渡金属硫化物催化剂的研究

Cathode catalyst plays important role on the performance of Li-air batteries, and transition metal oxides are the mostly studied catalysts. As an element in the same group as oxygen, sulfur has closely similar electron structure to oxygen, their transition metal compounds have similar properties. Thus, the transition metal sulfides have attracted much attention in recent years in the field of electrochemical energy storage and conversion systems. However, its application in Li-air batteries as cathode catalyst is only at the beginning stage, its actual catalytic performance and the mechanism is unknown. In this project, transition metal sulfides will be systematically investigated as cathode catalyst of Li-air batteries in three groups of layered graphene-like sulfides, spinel sulfides and non-layered/spinel sulfides, the co-relationship of preparation-microstructure-performance as well as the oxygen electrochemistry will be analyzed and understood in depth. Then, the solid-solid hybrid catalysts of layered graphene-like sulfides/non-layered sulfides and the solid-liquid hybrid of transition metal sulfides/lithium multi-sulfur compounds in solution will be studied in sequence to further improve the catalytic performance. With these studies, the actual catalytic mechanism of transition metal sulfides as cathode catalysts of Li-air batteries will be elucidated and the best strategy for fabricating high performance catalyst based on transition metal sulfides will be proposed.

阴极催化剂是制约锂空气电池性能的关键因素，目前研究最多的锂空气电池阴极催化剂是过渡金属氧化物。硫与氧属于同族元素，两者有着相似的外围电子结构，其过渡金属化合物与过渡金属氧化物有许多相似的性质，近年来逐渐引起电化学工作者的广泛关注。但是，过渡金属硫化物在锂空气电池中作为催化剂的应用研究才刚刚起步，文献资料非常有限，学术界对其性能及其影响因素和作用机理知之甚少。本项目拟以锂空气电池阴极用过渡金属硫化物催化剂为研究对象，分别对层状结构的类石墨烯硫化物、尖晶石结构硫化物和非层状/尖晶石结构硫化物的制备-微结构-催化性能之间的构效关系进行研究，阐明其锂空气电池氧电极电化学作用机理；并进一步通过薄层低维纳米层状过渡金属硫化物/非层状结构硫化物的固固复合和过渡金属硫化物/多硫化锂溶液的固液复合提升催化剂的性能，正确理解其构效关系和作用机理，提出构建高性能锂空气电池用过渡金属硫化物催化剂的最佳方案。

锂空气电池作为一种以金属锂为负极材料、空气中的氧气为正极材料的新型电池体系，其理论能量密度高达3458 Wh/kg，远高于日本新能源产业技术研究机构设定的二次电池完全替代内燃机的目标（500 Wh/kg），再加上空气中的氧气资源丰富、获取价格低廉，从而使锂空气电池被认为是极具前景的下一代低成本、高能量二次电池新体系，近年来国际学术界对其进行了广泛的关注的大量的研究。但是，锂空气电池目前的实际工作性能离实用要求尚有较大的差距。在众多制约锂空气电池性能的因素中，阴极催化剂是关键之一。本项目考虑到硫元素相对于氧元素所具有的低电负性、大原子半径等特点，以过渡金属硫化物为研究对象，分别对层状结构的类石墨烯硫化物、尖晶石结构硫化物、其他结构硫化物及多功能复合硫化物的制备-微结构-催化性能之间的构效关系进行大量的研究工作，通过实验测试和密度泛函理论计算相结合阐明其锂空气电池氧电极电化学作用机理，提出构建高性能锂空气电池用过渡金属硫化物催化剂的新思路和有效途径。