Nonwoven rGO Fiber-Aramid Separator for High-Speed Charging and Discharging of Li Metal Anode

Li metal, which has a high theoretical specific capacity and low redox potential, is considered to the most promising anode material for next-generation Li ion-based batteries. However, it also exhibits a disadvantageous solid electrolyte interphase (SEI) layer problem that needs to be resolved. Herein, an advanced separator composed of reduced graphene oxide fiber attached to aramid paper (rGOF-A) is introduced. When rGOF-A is applied, F⁻ anions, generated from the decomposition of the LiPF₆ electrolyte during the SEI layer formation process form semi-ionic C-F bonds along the surface of rGOF. As Li⁺ ions are plated, the “F-doped” rGO surface induces the formation of LiF, which is known as a component of a chemically stable SEI, therefore it helps the Li metal anode to operate stably at a high current of 20 mA cm⁻² with a high capacity of 20 mAh cm⁻². The proposed rGOF-A separator successfully achieves a stable SEI layer that could resolve the interfacial issues of the Li metal anode.