钴基尖晶石氧化物/氮化钛纳米复合结构锂空气电池阴极的研究

The Li-O2 battery, which has a comparable theoretical energy density with gasoline, has been considered one of the most promising energy storage devices for electric vehicles. In recent studies, carbon has been used widely as the basis of cathodes for Li-O2 cells. However, carbon materials is unstable on charging process, oxidatively decomposing to form Li2CO3. The accumulation of Li2CO3 may result in rising potential during galvanostatic charging and consequent electrolyte stability problems. In this study, nanostructured TiN materials are employed as a candidate for carbon materials, which sever as conducting framework for loading Co-based spinel to form a nanostructured Co-based spinel/TiN cathode. This cathode may avoid the irreversible reaction with Li2O2 (or superoxide), improving the distribution of LixO2 species and facilitating the cycle performance. Through tuning the nanostructure of cathode and the electronic structure of spinel species, the electrochemical performance are investigated. Furthermore, theoretical calculations are carried out to demonstrate experiment results. With new insight into the mechanism of cathode reaction, this study could be beneficial to the development of cycle performance for Li-O2 battery applications.

锂空气电池具备极高的理论能量密度，受到国内外科研人员的广泛关注。然而，循环寿命低下是制约锂空气电池实际应用的瓶颈问题，造成该问题的主要原因是Li2CO3在电极表面的不可逆积累和电解液的分解。本项目拟采用兼备良好电子导电性与化学稳定性的TiN材料制备纳米管阵列，代替传统的碳材料作为阴极载体，可以避免碳材料与充放电产物（或中间产物）发生不可逆反应，减少Li2CO3的积累；在TiN纳米管阵列载体上，以电化学沉积法负载钴基尖晶石氧化物，加速Li2O2分解，降低充电电位，限制电解液分解。通过对钴基尖晶石氧化物/TiN纳米复合阴极进行电化学表征，揭示负载成分的纳米结构、电子结构与电化学行为间的构效关系。在此基础上，对充放电过程进行充分表征和理论模拟，探索阴极反应机理。本项目的开展将为设计和制备稳定、高效的锂空气电池阴极提供新思路，并为提高锂空气电池循环寿命的研究提供科学依据。

锂空气电池因其具备极高的理论容量而受到广泛科研关注。目前锂空气电池阴极反应的可逆性是制约其进一步走向商业化的核心问题。为了提升锂空气电池阴极反应的可逆性，本项目首先从阴极材料体系入手，研究了钴基氧化物对中间产物分布的影响，有效抑制了中间产物在电极表面的积累，提升了电池的循环性能。通过球差校正电镜，在钴基氧化物电极上，首次从原子尺度上表征了放电产物Li2O2，并发现了奇特的阶结构，结合理论计算，我们发现了Li2O2表面缺锂结构的证据，为充电过程中Li2O2的分解机理研究提供了支持。为了减少碳材料载体带来的副反应，本项目引入TiN自支撑纳米阵列结构，有效讲了碳材料载体在充电过程中的分解，进一步改善了电池的可逆性。为了深入理解锂空气电池阴极反应机理，申请人通过差分电化学质谱对充电过程的气体产物及副产物进行深入表征，发现电解液分解使阴极副反应的主要来源，因此项目对电解液体系进行了研究和归纳，并开发出准固态电解质基锂空气电池，进一步提升了电池的循环性能。