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. Reduced graphene oxide (rGO) fibers attached to aramid paper acts as a conductive frame which helps a solid electrolyte interphase (SEI) layer to grow stably in the confined fibers structure and induces a chemically stable SEI layer containing LiF. This functional separator dramatically improves the stability of a Li metal anode.