Qi Shihan, Wang Huaping, He Jian, Liu Jiandong, Cui Chunyu, Wu Mingguang, Li Fang, Feng Yuezhan, Ma Jianmin
School of Physics and Electronics, Hunan University, Changsha 410082, China.
Key Laboratory of Materials Processing and Mold (Zhengzhou University), Ministry of Education, Zhengzhou University, Zhengzhou 450002, China.
Sci Bull (Beijing). 2021 Apr 15;66(7):685-693. doi: 10.1016/j.scib.2020.09.018. Epub 2020 Sep 12.
Lithium (Li) metal is widely considered as a promising anode for next-generation lithium metal batteries (LMBs) due to its high theoretical capacity and lowest electrochemical potential. However, the uncontrollable formation of Li dendrites has prevented its practical application. Herein, we propose a kind of multi-functional electrolyte additives (potassium perfluorinated sulfonates) from the multi-factor principle for electrolyte additive molecular design (EDMD) view to suppress the Li dendrite growth. The effects of these additives are revealed through experimental results, molecular dynamics simulations and first-principles calculations. Firstly, K can form an electrostatic shield on the surface of Li anode to prevent the growth of Li dendrites. Secondly, potassium perfluorinated sulfonates can improve the activity of electrolytes as co-conductive salts, and lower the electro-potential of Li nucleation. Thirdly, perfluorinated sulfonate anions not only can change the Li solvation sheath structure to decrease the desolvation energy barrier and increase the ion migration rate, but also can be partly decomposed to form the superior solid electrolyte interphase (SEI). Benefited from the synergistic effects, an outstanding cycle life over 250 h at 1 mA cm is achieved in symmetric Li||Li cells. In particular, potassium perfluorinated sulfonate additives (e.g., potassium perfluorohexyl sulfonate, denoted as KPFHS) can also contribute to the formation of high-quality cathode electrolyte interphase (CEI). As a result, Li||LiNiMnCoO full cells exhibit significantly enhanced cycling stability. This multi-factor principle for EDMD offers a unique insight on understanding the electrochemical behavior of ion-type electrolyte additives on both the Li metal anode and high-voltage cathode.
锂（Li）金属因其高理论容量和最低电化学电位，被广泛认为是下一代锂金属电池（LMBs）颇具前景的阳极材料。然而，锂枝晶的不可控生长阻碍了其实际应用。在此，我们从电解质添加剂分子设计（EDMD）的多因素原理出发，提出了一种多功能电解质添加剂（全氟磺酸钾），以抑制锂枝晶的生长。通过实验结果、分子动力学模拟和第一性原理计算揭示了这些添加剂的作用。首先，K可以在锂阳极表面形成静电屏蔽，防止锂枝晶的生长。其次，全氟磺酸钾作为共导电盐可以提高电解质的活性，并降低锂成核的电位。第三，全氟磺酸根阴离子不仅可以改变锂溶剂化鞘层结构，降低去溶剂化能垒并提高离子迁移速率，还可以部分分解形成优异的固体电解质界面（SEI）。受益于协同效应，对称Li||Li电池在1 mA cm下实现了超过250 h的出色循环寿命。特别地，全氟磺酸钾添加剂（例如全氟己基磺酸钾，记为KPFHS）也有助于形成高质量的阴极电解质界面（CEI）。结果，Li||LiNiMnCoO全电池表现出显著增强的循环稳定性。这种EDMD的多因素原理为理解离子型电解质添加剂在锂金属阳极和高压阴极上的电化学行为提供了独特的见解。
