Enhanced safety of polymer solid electrolytes by using black phosphorene as a flame-retardant

Solid polymer electrolytes attract much attention due to their good flexibility and good interfacial contact property. However, the inherent thermal instability of polymers inhibits the practical application of solid polymer electrolytes. In this work, the black phosphorene nanosheet, a fire-retardant additive, was introduced and incorporated into poly (ethylene oxide) (PEO)-based solid polymer electrolyte to improve the thermal property. The BP/PEO based solid polymer electrolyte membrane is thermally stable, nonflammable, and mechanically strong, more than 400 h of cycling with low polarization based on a Li-Li symmetric cell was achieved. LiFePO4//Li solid state battery with the BP/PEO based solid polymer electrolyte shows a high-capacity performance (153 mAh g−1 at 0.1 C) as well as cycling performance (100 cycles at 0.2 C rate) at 60 °C. The flammability tests indicated that a small amount of black phosphorene can make the electrolyte display good non-flammability. In the micro-scale combustion calorimetry test, the peak heat release rate of BP/PEO based solid polymer electrolyte reduced by 62.5% and flame ignition time is slower compared with the PEO based solid polymer electrolyte without incorporating black phosphorene. The present work demonstrated that the black phosphorene nanosheets do not weaken the electrochemical properties of solid polymer electrolytes, but also enhance their thermal properties.