Low cycling Coulombic efficiency (CE) and messy Li dendrite growth problems have greatly hindered the development of anode-free Li-metal batteries (AFLBs). Thus, functional electrolytes for uniform lithium deposition and lithium/electrolyte side reaction suppression are desired. Here, we report a locally fluorinated electrolyte (LFE) medium layer surrounding Cu foils to tailor the chemical compositions of the solid-electrolyte interphase (SEI) in AFLBs for inhibiting the immoderate Li dendrite growth and to suppress the interfacial reaction. This LFE consists of highly concentrated LiTFSI dissolved in a fluoroethylene carbonate and/or succinonitrile plastic mixture. The CE of Cu||LiNi0.8Co0.1Mn0.1O2 (NCM811) AFLB increased to a high level of 99% as envisaged, and the cycling ability was also highly improved. These improvements are facilitated by the formation of a uniform, dense, and LiF-rich SEI. LiF possesses high interfacial energy at the LiF/Li interface, resulting in a more uniform Li deposition process as proved by density functional theory (DFT) calculation results. This work provides a simple yet utility tech for the enhancement of future high-energy-density AFLBs.
Lei Fu,Chao Zou,Yun Huang,Xinyan Xiang,Jie Xiao,Wenping Zeng,Xing Li,Mingshan Wang,Bingshu Guo,Yuanhua Lin
Multifunctional modified separators have the potential to effectively regulate Li ion deposition, suppress the growth of dendrite and improve the safety of lithium metal batteries (LMBs). Here, we designed a separator, constructed by co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) on PP separator. Due to the introduction of polar functional groups such as amine groups, PDA/PEI-3 modified separator exhibits better electrolyte wettability, higher Li ion migration number (0.9), lower energy barrier and faster ion transfer kinetics. Electrochemical tests prove that PDA/PEI-3 modified separator has achieved better cycling stability at different current density in Li//Li symmetric cells and higher CE in Li//Cu cells. Meanwhile, the Li/LFP full cells show more excellent rate performance and long cycle performance (80%). SEM and XPS also prove that modified separator has achieved homogenized Li ions flux and more uniform LiF-rich SEI layer. This work provides a simple and effective strategy for functional separator to protect Li metal anode and improve safety performance of LMBs.
危险品化学品经营许可证（带存储）