Abstract:

The application of metallic lithium cathodes can significantly improve the energy density of existing lithium-ion batteries，due to their ultra-high specific capacity（3 860 mA·h/g） and ultra-low reduction potential（-3.04 V）.However，the continuous side reactions between metallic lithium and electrolyte lead to severe polarization of the battery，the increasing of inactive lithium，as well as the fast capacity decay.In this study，in order to improve the cycling performance of the Li metal batteries，the boron nitride film was used as the artificial solid electrolyte interphase（SEI） on the surface of metallic lithium to inhibit the side reaction between the boron nitride film and the electrolyte，so as to achieve the long cycle of metallic lithium battery.Boron nitride film could be uniformly deposited on the surface of metallic lithium by a simple and easy spraying deposition method，and the optimal deposition time by electrochemical impedance spectroscopy was investigated.The boron nitride SEI film possessed the character of ionic conducting and electron blocking，which successfully suppressed the polarization increasing.Compared with the unmodified lithium metal，the area specific resistance of the cathode interface was decreased from 4.6 Ω/cm² to 1.2 Ω/cm² after boron nitride modification.The initial coulombic efficiency of the assembled lithium manganate/metallic lithium battery was increased from 89.2% to 96.6%.The capacity retention was increased from 86.3% to 94.6% after 300 cycles at 1C.

Key words: lithium-ion battery, boron nitride, lithium cathode, artificial solid-state interphase