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Research progress and challenges of lithium-oxygen battery soluble catalysts

2019-07-02 来源:亚科官网
 
The rechargeable lithium-oxygen battery has a very high theoretical specific energy of about 3,500 Wh kg-1. If it can be applied in practice, it will definitely have a revolutionary impact on the battery industry and people's lives. However, current developments in lithium-oxygen batteries have encountered key technical challenges such as poor cycle performance and low energy efficiency. These problems are mainly caused by the charging process accompanying the precipitation of oxygen. Theoretically, the discharge product lithium peroxide resolves oxygen at 2.96 V vs. Li/Li+. However, in the actual charging process, due to the low conductivity of lithium peroxide and the weak catalytic activity of the solid catalyst interface, the charging overpotential is too high, resulting in a series of problems such as electrolyte decomposition and electrode material corrosion.
In the past 20 years of research, solid heterogeneous catalysts have been widely used in lithium oxygen batteries, and great progress has been made. However, due to the intrinsic disadvantage of low solid-solid interface catalytic activity between the solid phase catalyst and the discharge product, it is difficult to significantly increase the energy storage efficiency and cycle life of the lithium-oxygen battery. Compared with the traditional solid phase catalyst, the soluble catalyst can convert solid-solid electrochemical catalysis into a solid-liquid electrocatalytic process, which significantly reduces the decomposition overpotential of the lithium peroxide of the discharge product. It is considered to be a promising strategy to improve the performance of lithium-oxygen batteries.
Recently, Prof. He Ping from the School of Modern Engineering and Applied Science of Nanjing University and postdoctoral Zhao Wenjia and doctoral student Mu Xiaowei published a review article on Batteries & Supercaps, summarizing the reaction mechanism of various types of soluble catalysts and in lithium-oxygen battery research. Professor Zhou Haoshen of the institute guided the writing of the review.
In this paper, soluble catalysts are divided into inorganic compounds and organic compounds. The new materials, new mechanisms and new functions of soluble catalysts in lithium-oxygen battery research are summarized. In particular, new research hotspots such as two-liquid phase catalysts, positive/negative function catalysts, and high-rate liquid phase catalysts. In addition, the paper discusses the basic principles of soluble catalysts and the effects on the morphology and discharge capacity of lithium peroxide. Finally, the challenges and development directions of soluble catalysts in lithium-oxygen batteries are presented.