Li Yuan, An Yongling, Tian Yuan, Wei Chuanliang, Xiong Shenglin, Feng Jinkui
SDU & Rice Joint Center for Carbon Nanomaterials, Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan 250061, P. R. China.
School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P. R. China.
ACS Appl Mater Interfaces. 2021 Mar 3;13(8):10141-10148. doi: 10.1021/acsami.1c00661. Epub 2021 Feb 17.
The high reactivity between lithium metal and traditional carbonate electrolytes is a great obstacle to realize the long-term cycling ability of lithium metal batteries. Ether-based electrolytes have good stability toward lithium metal anodes. However, the oxidation stability of ether-based electrolytes is generally lower than 4 V, which limits the application of high-voltage (>4 V) cathodes and restricts the energy density. The high flammability of ether is another key issue that hinders the commercialization of ether-based electrolytes. To address these issues, herein, we report a high-voltage, nonflammable ether-based electrolyte with F-, N-, and P-rich hexafluorocyclotriphosphazene (HFPN) as a cosolvent. HFPN can not only act as a highly efficient flame-retarding agent but also form a dense and homogeneous solid electrolyte interphase (SEI) layer rich in LiF and LiN on the lithium metal anode, which stabilizes the lithium/electrolyte interface and inhibits the formation of lithium dendrites. Moreover, the HFPN-based electrolyte has a wider potential window than 4 V. As a result, with this electrolyte, high-voltage lithium metal batteries exhibit a capacity retention of ∼95% after 100 cycles. This study may provide a new pathway for developing safe, high-energy, and dendrite-free lithium metal batteries.
锂金属与传统碳酸盐电解质之间的高反应活性是实现锂金属电池长期循环能力的巨大障碍。醚基电解质对锂金属阳极具有良好的稳定性。然而，醚基电解质的氧化稳定性通常低于4 V，这限制了高压（>4 V）阴极的应用，并限制了能量密度。醚的高易燃性是阻碍醚基电解质商业化的另一个关键问题。为了解决这些问题，在此我们报道了一种以富含F、N和P的六氟环三磷腈（HFPN）作为共溶剂的高压、不可燃醚基电解质。HFPN不仅可以作为高效的阻燃剂，还能在锂金属阳极上形成富含LiF和LiN的致密且均匀的固体电解质界面（SEI）层，从而稳定锂/电解质界面并抑制锂枝晶的形成。此外，基于HFPN的电解质具有比4 V更宽的电位窗口。因此，使用这种电解质的高压锂金属电池在100次循环后容量保持率约为95%。这项研究可能为开发安全、高能且无枝晶的锂金属电池提供一条新途径。
