物理化学学报2021，Vol.37Issue(1)：126-135,10.DOI:10.3866/PKU.WHXB202007016
一种有助于稳定锂金属循环的富氟化位点框架结构
A Framework with Enriched Fluorinated Sites for Stable Li Metal Cycling
摘要
Abstract
In past decades,lithium-ion batteries(LIBs)were the dominant energy storage systems for powering portable electronic devices because of their reliable cyclability.However,further increase in the energy density of LIBs was met by a bottleneck when low-specific-capacity graphite was used at the anode.Li metal has long been regarded as the ideal anode material for building the next high-energy-density batteries due to its ultrahigh capacity of 3860 mAh-g-1,which is ten times higher than that of graphite.However,using Li metal as an anode in rechargeable batteries is challenging due to its highuncontrolled volume expansion and aggressive side reactions with liquid electrolytes. In this study, we demonstrate the effect of a three-dimensional (3D) framework with enriched fluorinated sites for Li metal protection. This framework is obtained via a facile integration of down-sized fluorinated graphite (CFx) particles into Li+ conducting channels. Thermogravimetry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy results show that Li+ conducting channels rich in lithium fluoride (LiF) are formed in situ across the embedded CFx particles during the initial lithiation process, leading to fast Li+ transfer. Scanning electron microscopy results show that residual CFx particles could act as high-quality nucleation sites for uniform Li deposition inside the framework. These features could not be achieved with a 2D structure consisting of large CFx flakes, due to the limited Li+ transfer paths and low utilization ratio of CFx for conversion into LiF-based solid electrolyte interphase (SEI) layers. Consequently, better performance of Li metal anodes in a 3D framework with enriched fluorinated sites is demonstrated. Stable Li plating/stripping over 240 cycles is obtained at a current density of 0.5 mA?cm-2 for a fixed capacity of 1 mAh?cm-2 by maintaining a voltage hysteresis below 80 mV. Improved Li-LiFePO4 full cell performance with a practical negative/positive capacity ratio of 3 is also demonstrated. These results show the rational combination of well-developed 3D Li+ transfer channels and enriched fluorinated sites as an optimized interfacial design beyond the single use of a 2D fluorinated interface, giving new insight into the protection of Li metal anodes in high-energy-density batteries.关键词
锂金属电池/锂金属负极/氟化石墨/固液界面/库伦效率Key words
Li metal battery/Li metal anode/Fluorinated graphite/Solid electrolyte interphase/Coulombic efficiency分类
化学化工引用本文复制引用
王木钦,彭哲,林欢,李振东,刘健,任重民,何海勇,王德宇..一种有助于稳定锂金属循环的富氟化位点框架结构[J].物理化学学报,2021,37(1):126-135,10.基金项目
The project was supported by the National Natural Science Foundation of China(51872304),Ningbo 2025 Project,China(2018B10061,2019B10044)and the National Key R& D Program of China(2018YFB0905400).国家自然科学基金(51872304),宁波市2025计划(2018B10061,2019B10044)和国家重点研发计划(2018YFB0905400)资助项目 （51872304）
