Engineered Heat Dissipation and Current Distribution Boron Nitride-Graphene Layer Coated on Polypropylene Separator for High Performance Lithium Metal Battery

Abstract Li metal as a battery anode has been intensively studied because of its capacity (3860 mA g−1), a low standard electrode potential (−3.04 vs. SHE), a reasonable electronic conductivity and low density. However, lithium metal suffers from a continuous Li dendrite growth upon charge-discharge cycling, delivering a poor coulombic efficiency and consequently its early failure. Here, engineered bilayer separators demonstrate that a boron nitride-graphene (BNxGry) layer coated on one side of polypropylene (PP) membrane remarkably reduces the polarization and impedance, and significantly improve the performance and stability of Li/Cu half-cells. Moreover, Li/LiFePO4 full cell with modified BN50Gr50/PP separator presents a remarkably stable 1000 charge-discharge cycles with a specific capacity of 114 mAh g−1 at 1 C-rate. The superiority of the modified separator is due to an effective synergistic effect between physico-chemical properties of Gr (reducing local current density) and BN (dissipating local heat) as well as providing enhanced structural and mechanical stability.