Redox Shuttles for Overcharge Protection of Lithium-Ion Battery

Abstract

Redox shuttle was proposed for overcharge protections of lithium-ion battery. Development of novel redox shuttles is in great needs since this method provides an economic and efficient way to make the cell system safer and does not require extra cost, weight, and volume. To accommodate different chemistry of lithium-ion battery, redox shuttles have to be versatile and tunable in terms of many properties, such as redox potential, electrochemical stability, and compatibility. A series of novel redox shuttles has been developed based on organic synthesis and delicate design, many of which were developed with intentional improvement, such as solubility in carbonate based electrolytes, elevated potentials, and better electrochemical stability. For instance, ANL-2 redox shuttle was developed with improved solubility in carbonate based electrolytes and excellent overcharge performance. The success of ANL-2 was based on the previous attempts using various design strategies to improve the solubility of DDB, including asymmetric ANL-1 redox shuttle, and DBMOEB (1,4-di-tert-butyl-2,5-bis(2-methoxyethoxy)methoxy-benzene). Other examples are ANL-3 and ANL-4 redox shuttles, with focus on increasing the redox potentials. ANL-3 is able to provide 4.8 V vs Li/Li+ oovercharge protection, highest ever reported in the literature. ANL-4, on the other hand, can deliver more than 90 cycles of overcharge protection for LMO cathode.