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.