Crumpled ir nanosheets fully covered on porous carbon nanofibers for long-life rechargeable lithium–CO₂ batteries

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.