Johansson Isabell L, Sångeland Christofer, Uemiya Tamao, Iwasaki Fumito, Yoshizawa-Fujita Masahiro, Brandell Daniel, Mindemark Jonas
Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden.
Department of Materials and Life Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan.
ACS Appl Energy Mater. 2022 Aug 22;5(8):10002-10012. doi: 10.1021/acsaem.2c01641. Epub 2022 Jul 19.
Rechargeable batteries with solid polymer electrolytes (SPEs), Li-metal anodes, and high-voltage cathodes like LiNi Mn Co O (NMC) are promising next-generation high-energy-density storage solutions. However, these types of cells typically experience rapid failure during galvanostatic cycling, visible as an incoherent voltage noise during charging. Herein, two imidazolium-based zwitterions, with varied sulfonate-bearing chain length, are added to a poly(ε-caprolactone--trimethylene carbonate):LiTFSI electrolyte as cycling-enhancing additives to study their effect on the electrochemical stability of the electrolyte and the cycling performance of half-cells with NMC cathodes. The oxidative stability is studied with two different voltammetric methods using cells with inert working electrodes: the commonly used cyclic voltammetry and staircase voltammetry. The specific effects of the NMC cathode on the electrolyte stability is moreover investigated with cutoff increase cell cycling (CICC) to study the chemical and electrochemical compatibility between the active material and the SPE. Zwitterionic additives proved to enhance the electrochemical stability of the SPE and to facilitate improved galvanostatic cycling stability in half-cells with NMC by preventing the decomposition of LiTFSI at the polymer-cathode interface, as indicated by X-ray photoelectron spectroscopy (XPS).
具有固体聚合物电解质（SPEs）、锂金属阳极和诸如LiNi Mn Co O（NMC）等高压阴极的可充电电池是很有前景的下一代高能量密度存储解决方案。然而，这类电池在恒电流循环过程中通常会迅速失效，充电时表现为不连贯的电压噪声。在此，将两种具有不同磺酸酯链长度的咪唑鎓两性离子作为循环增强添加剂添加到聚（ε-己内酯-三亚甲基碳酸酯）：LiTFSI电解质中，以研究它们对电解质电化学稳定性和具有NMC阴极的半电池循环性能的影响。使用带有惰性工作电极的电池，通过两种不同的伏安法研究氧化稳定性：常用的循环伏安法和阶梯伏安法。此外，通过截止增加电池循环（CICC）研究NMC阴极对电解质稳定性的具体影响，以研究活性材料与SPE之间的化学和电化学兼容性。如X射线光电子能谱（XPS）所示，两性离子添加剂被证明可增强SPE的电化学稳定性，并通过防止LiTFSI在聚合物-阴极界面分解，促进具有NMC的半电池中恒电流循环稳定性的提高。
