Enrichment of Chlorine in Porous Organic Nanocages for High-Performance Rechargeable Lithium-Chlorine Batteries.

Abstract

Rechargeable Li-Cl2 batteries are recognized as promising candidates for energy storage due to their ultrahigh energy densities and superior safety features. However, Li-Cl2 batteries suffer from a short cycle life and low Coulombic efficiency (CE) at a high specific cycling capacity due to a sluggish and insufficient Cl2 supply during the redox reaction. To achieve Li-Cl2 batteries with high discharge capacity and CE, herein, we propose and design an imine-functionalized porous organic nanocage (POC) to enrich Cl2 molecules. Based on density functional theory (DFT) calculations, the imine group sites in host cages strongly interact with Cl2 molecules, facilitating the rapid capture of Cl2. As a result, the output capacity of the Li-Cl2 battery using POC (Li-Cl2@POC) is significantly boosted, achieving an ultrahigh discharge capacity of 4000 mAh/g at ∼100% CE. Benefiting from the designed POC, the highest utilization ratio of deposited LiCl at the first cycle in the Li-Cl2@POC battery reaches as high as 85%, superior to all reported values. The Li-Cl2@POC battery exhibits excellent electrochemical performance even at low temperatures, delivering stable cycling over 200 cycles under a capacity of 2000 mAh/g at -20 °C with a voltage plateau of 3.5 V and an average CE of 99.7%. We also demonstrate that the Li-Cl2@POC cells can be assembled and well-operated in a dry room, showing advantages for mass production. Our designed POC promotes the practical deployment of rechargeable Li-Cl2 batteries.