Crumpled Ir Nanosheets Fully Covered on Porous Carbon Nanofibers for Long-Life Rechargeable Lithium-CO₂ Batteries.

Abstract

Aprotic Li-CO₂ batteries are a new class of green energy storage and conversion system, which can utilize the CO₂ from the atmosphere in an environmentally friendly way. However, the biggest problem of the existing Li-CO₂ batteries is that they suffer from high polarization and poor cycling performance, mainly caused by the insulating and insoluble discharge product, Li₂ CO₃ . Herein, this study reports the synthesis of wrinkled, ultrathin Ir nanosheets fully anchored on the surface of N-doped carbon nanofibers (Ir NSs-CNFs) as an efficient cathode for improving the performance of lithium-CO₂ batteries. The battery can be steadily discharged and charged at least for 400 cycles with a cut-off capacity of 1000 mAh g^-1 at 500 mA g^-1 . Meanwhile, the cathode can effectively reduce the charge overpotential by showing a charge termination voltage below 3.8 V at 100 mA g^-1 , which is the smallest charge overpotential reported to date. The ex situ analysis of the intermediate products reveals that during the discharge process, Ir NSs-CNFs can greatly stabilize amorphous granular intermediate (probably Li₂ C₂ O₄ ) and delay its further transformation into thin plate-like Li₂ CO₃ , whereas during the charge process, it can make Li₂ CO₃ be easily and completely decomposed, which is the key in greatly improving its performance for lithium-CO₂ batteries.