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

Rechargeable Li–Cl 2 batteries are recognized as promising candidates for energy storage due to their ultrahigh energy densities and superior safety features. However, Li–Cl 2 batteries suffer from a short cycle life and low Coulombic efficiency (CE) at a high specific cycling capacity due to a sluggish and insufficient Cl 2 supply during the redox reaction. To achieve Li–Cl 2 batteries with high discharge capacity and CE, herein, we propose and design an imine-functionalized porous organic nanocage (POC) to enrich Cl 2 molecules. Based on density functional theory (DFT) calculations, the imine group sites in host cages strongly interact with Cl 2 molecules, facilitating the rapid capture of Cl 2 . As a result, the output capacity of the Li–Cl 2 battery using POC (Li–Cl 2 @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–Cl 2 @POC battery reaches as high as 85%, superior to all reported values. The Li–Cl 2 @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–Cl 2 @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–Cl 2 batteries.