金属锂电池负极界面氮化硼修饰膜的研究

Research on boron nitride modified film for cathode interface of metallic lithium battery

金属锂负极由于具有超高的比容量(3 860 mA·h/g)与超低的还原电位(-3.04 V),其应用能够大幅提升现有锂离子电池的能量密度。然而,金属锂与电解液持续不断的副反应可导致电池的严重极化、非活性锂的增加及电池容量的迅速衰减。为了提升金属锂电池的循环性能,采用氮化硼薄膜作为金属锂表面的人工固体电解质膜(SEI膜)抑制其与电解液之间的副反应,以实现金属锂电池的长循环。采用简单易操作的喷涂沉积法,可将氮化硼薄膜均匀地沉积于金属锂表面,并通过电化学阻抗谱探索了最佳沉积次数。氮化硼SEI膜具有离子导通且电子绝缘的特性,成功地抑制了界面副反应与电池的极化增加。相比未经修饰的金属锂,经氮化硼修饰后,电池负极单位面积阻抗由4.6Ω/cm^(2)降低至1.2Ω/cm^(2)。所组装的锰酸锂/金属锂电池首圈库伦效率由89.2%提升至96.6%;1C条件下循环300次后,容量保持率由86.3%提升至94.6%。

The application of metallic lithium cathodes can significantly improve the energy density of existing lithium-ion batteries,due to their ultra⁃high specific capacity(3860 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 me⁃tallic 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 sup⁃pressed the polarization increasing.Compared with the unmodified lithium metal,the area specific resistance of the cathode interface was decreased from 4.6Ω/cm^(2) to 1.2Ω/cm^(2) 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 in⁃creased from 86.3%to 94.6%after 300 cycles at 1C.