A low-overpotential sodium/fluorinated graphene battery based on silver nanoparticles as catalyst

Fluorinated graphene (F-GNS) was synthesized using commercial graphene (GNS) as starting material and introduced in sodium batteries, which exhibited good rate performance, but large voltage gap between discharge and charge process. Ag nanoparticles were employed in freestanding and binder-free F-GNS electrode (the composite film electrode was labeled as FGA) as catalyst, which were shown to strongly facilitate the decomposition of NaF during charge process in sodium/carbon fluorides (Na/CF_x) secondary batteries. During discharge process, the discharge voltage with Ag was about the same as that of Na/F-GNS cell. During charge process, the charge voltage of Na/FGA cell was substantially lower (by 480 mV) than that of Na/F-GNS cell, thus leading to a lower overpotential and a higher electric efficiency. Nanosized amorphous discharge products of NaF formed in Na/FGA cells were ascribed as the key role in reducing the polarization.