A team led by Prof. CHEN Wei, Prof. JIANG Hailong and Prof. LI Zhenyu from the University of Science and Technology of China (USTC) adopted NH 2 -functionalized metal-organic frameworks (MOFs) in lithium-chlorine (Li-Cl 2 ) batteries to achieve high specific capacities, cycle stability and superior low-temperature performance. Their work was published in Joule on March 15 th .
Traditional lithium-thionyl chloride (Li-SOCl 2 ) batteries are widely used for their high energy density and other advantages, but alternatives are still needed since Li-SOCl 2 batteries are not rechargeable. Rechargeable Li-Cl 2 battery was first invented in 2021, with a high specific capacity of 1200 mAh/g and a high output voltage of ~3.6 V.
However, the following problems stand in the way of the practical application of Li-Cl 2 battery. Firstly, the Cl 2 reaction is limited by the weak physical adsorption of porous carbon to Cl 2 molecules. Secondly, the excessive LiCl generation into the carbon pores blocks the channels for Li+ transportation and Cl 2 diffusion, hindering further electrochemical reactions. Furthermore, the shuttle effect of unbonded Cl 2 leads to battery capacity decay, especially at high output capacities. Therefore, the cathode materials with highly porous structures are vital to realize high-performance Li-Cl 2 batteries.
To overcome the above difficulties, the team proposed that MOFs with Lewis basic functional groups should be applied to improve the cathode Cl 2 /LiCl reactions. Guided by theoretical predictions, MOFs with -NH 2 functional groups were screened out using first-principles calculation and applied in Li-Cl 2 batteries. Cryo-TEM and low-dose high-resolution TEM showed that UiO-66-NH 2 maintains a very stable structure during cycling, and XPS verified -NH 2 groups’ strong affinity to Cl 2 and LiCl, thus enhancing its redox reaction kinetics. Li-Cl 2 @MOF batteries designed by the team reached a maximum discharge specific capacity of 2000 mAh/g and are stable for more than 500 cycles at a specific capacity of 1000 mAh/g. Meanwhile, the batteries performed stable function under the temperature of -40 °C.
This work presented an innovative design of cathode materials in Li-Cl 2 batteries, paving the way for future application of rechargeable Li-Cl 2 batteries.
Joule
Metal-organic frameworks for nanoconfinement of chlorine in rechargeable lithium-chlorine batteries
15-Mar-2023