Hsia Ting-Nan, Lu Hsin-Chun, Hsueh Yu-Chih, Rajesh Kumar Selvaraj, Yen Chien-Sheng, Yang Chun-Chen, Jessie Lue Shingjiang
Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan City 333, Taiwan.
Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan City 333, Taiwan; Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Keelung City 204, Taiwan.
J Colloid Interface Sci. 2022 Nov 15;626:524-534. doi: 10.1016/j.jcis.2022.06.172. Epub 2022 Jul 3.
In this study, a dense polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) coating is fabricated on a lithium (Li) anode sheet, which acts as a synergistic protective layer and electrolyte separator for Li-oxygen (Li-O) batteries. This thin coating is dried through slow solvent evaporation and vacuum drying methods. The solvent-free, dense PVDF-HFP coating has a thickness of 45 µm and can absorb 62% of electrolyte. The battery containing the PVDF-HFP coating demonstrates a maximum peak power density of 3 mW cm, significantly higher than that of the battery with the PVDF coating (0.8 mW cm) but lower than that without coating (equipped with a commercial glass fiber separator, 7.3 mW cm). However, the PVDF-HFP coating enables the Li-O battery to reach a capacity of 4400 mA h g, much higher than that without the coating (glass fiber separator, 850 mA h g). The symmetric Li-Li cells further confirm steady and low overpotentials using the anode coating at a high current density of 1.0 mA cm, indicating stable Li plating/stripping process. The PVDF-HFP-coated battery has a longer cycling lifetime (1700 h) than those with the PVDF coating (120 h) and a glass fiber separator (670 h). The Raman spectra show that there are lithium compounds (mainly lithium hydroxide) and residual PVDF-HFP on the aged anode surface. The dense PVDF-HFP coating on the Li anode plays dual roles: it creates a strong protective layer for stabilizing the solid-electrolyte interface (in the solid phase), and acts as a separator for modulating the Li metal deposition and stripping behaviors in liquid electrolyte.
在本研究中，在锂（Li）阳极片上制备了致密的聚偏二氟乙烯 - 六氟丙烯（PVDF - HFP）涂层，该涂层作为锂氧（Li - O）电池的协同保护层和电解质隔膜。这种薄涂层通过缓慢溶剂蒸发和真空干燥方法干燥。无溶剂的致密PVDF - HFP涂层厚度为45 µm，可吸收62%的电解质。含有PVDF - HFP涂层的电池显示出最大峰值功率密度为3 mW/cm²，明显高于具有PVDF涂层的电池（0.8 mW/cm²），但低于无涂层的电池（配备商用玻璃纤维隔膜，7.3 mW/cm²）。然而，PVDF - HFP涂层使Li - O电池能够达到4400 mA h/g的容量，远高于无涂层的电池（玻璃纤维隔膜，850 mA h/g）。对称Li - Li电池进一步证实，在1.0 mA/cm²的高电流密度下使用阳极涂层时具有稳定且低的过电位，表明锂电镀/剥离过程稳定。与具有PVDF涂层（120 h）和玻璃纤维隔膜（670 h）的电池相比，PVDF - HFP涂层的电池具有更长的循环寿命（1700 h）。拉曼光谱表明，老化的阳极表面存在锂化合物（主要是氢氧化锂）和残留的PVDF - HFP。Li阳极上的致密PVDF - HFP涂层起着双重作用：它形成一个强大的保护层以稳定固体电解质界面（在固相中），并作为隔膜调节液体电解质中锂金属的沉积和剥离行为。
