上世纪九十年代流行的锂离子电池因比能量密度低等问题，无法满足市场需求。锂空电池理论能量密度11400Wh·kg^-1（不包含氧气）接近汽油的12200Wh·kg^-1,成为近年来的研究热点。但它存在着正极反应动力学缓慢等问题，寻找高效催化剂是解决问题的关键。钴基氧化物用作催化剂，价格便宜，具备很大的商业化潜力。创造氧空位和引入异质结构是提高钴基氧化物电催化性能常用的两种策略，本文旨在合成具有独特异质结构和氧缺陷的CoO@Co₉S₈复合材料，并测试其电催化性能。主要研究内容如下：

利用水热法制备前驱体Co(OH)₂，在空气氛围中煅烧得到Co₃O₄，再在Ar保护下将其部分硫化合成CoO@Co₉S₈复合材料。为探究CoO@Co₉S₈复合材料的催化活性，把KB、CoO作为对比电极，保持其他条件一致，研究将三者用作正极催化剂的锂空电池各项电化学性能的差异。CoO具有吸附性，Co₉S₈具有显著的电催化功能，因此CoO@Co₉S₈异质结构能发挥协同吸附电催化作用，具有较好的容量、循环性能，能明显降低充放电过程中的极化。在电流密度为200mA·g^-1的全放电测试中，CoO@Co₉S₈的放电比容量可达5517mAh·g^-1。在电流密度为200mA·g^-1，限制放电比容量为500mAh·g^-1的条件下可以稳定循环49圈，优于对比样KB和CoO。

The lithium-ion batteries popular in the 1990s were unable to meet the market demand due to their low specific energy density. The theoretical energy density of lithium-air battery is 11400Wh·kg^-1 (excluding oxygen), which is close to 12200Wh·kg^-1 of gasoline, and has become a hot research topic in recent years. However, it has a series of problems such as slow reaction kinetics at the anode, and finding an efficient catalyst is the key to solve the problem. Cobalt-based oxides are used as catalysts, which are inexpensive and have great potential for commercialization. Creating oxygen vacancies and introducing heterostructures are two commonly used strategies to improve the electrocatalytic performance of cobalt-based oxides. The aim of this paper is to synthesize CoO@Co₉S₈ composites with unique heterostructures and oxygen defects and to test their electrocatalytic performance. The main methods and results are as follows:

    The precursor Co(OH)₂ was prepared by hydrothermal method, and Co₃O₄ is calcined in the air atmosphere, and then partially sulfurized to synthesize CoO@Co₉S₈ composites under the protection of Ar . In order to explore the catalytic activity of CoO@Co₉S₈ composites, taking KB and CoO as comparison samples to maintain consistency in other conditions, and study the differences in the electrochemical properties of the three when they are used in the cathode catalyst of lithium-air batteries. CoO showed strong adsorption function and Co₉S₈ has significant electrocatalytic function, so the CoO@Co₉S₈ heterogeneous structure could play a synergistic adsorption electrocatalytic role with good capacity and cycling performance and significantly reduce the polarization in the charging process. In the full discharge test with a current density of 200 mA·g^-1, the specific capacity of CoO@Co₉S₈ can reach 5517 mAh·g^-1. Under the condition that the current density is set to 200mA·g^-1 and the limited discharge ratio capacity is 500mAh·g^-1, the cycle can be stable for 49 turns, which is better than the comparison sample KB and CoO.