Crumpled Ir Nanosheets Fully Covered on Porous Carbon Nanofibers for Long-Life Rechargeable Lithium-CO_2 Batteries

摘要

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, Li2CO3. 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 Li2C2O4) and delay its further transformation into thin plate-like Li2CO3, whereas during the charge process, it can make Li2CO3 be easily and completely decomposed, which is the key in greatly improving its performance for lithium-CO2 batteries.