Liu Xuejiao, Iqbal Asma, Ali Nazakat, Qi Rongrong, Qian Xuefeng
Shanghai Electrochemical Energy Devices Research Center, School of Chemistry and Chemical Engineering and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19431-19438. doi: 10.1021/acsami.0c00755. Epub 2020 Apr 15.
PSS has been studied as a silicon-based binder due to its inherent superior electricity and electrochemical stability. However, it cannot effectively alleviate the huge volume changes of silicon during lithiation/delithiation due to its linear structure, resulting in poor cycling stability. Ion-cross-linking is a usual method to cross-link linear polymers into 3D structures. In this paper, multivalent cations of the 5th period and Group 2 cross-linked PEDOT:PSS were applied as silicon anode binders and studied systematically. It was found that the variation trend of viscosity and conductivity of PEDOT:PSS after cross-linking was consistent with that of ionic potential and softness parameters of multivalent cations. The mesostructure of a binder after cross-linking is influenced by the solubility product constant of sulfites or hydroxides of cations and the growth characteristics of crystals. An Sn-cross-linked binder displayed increased viscosity and electrical conductivity and higher reduced modulus and hardness due to its positive softness parameter and higher ion potential. The Si electrode with the Sn-cross-linked binder showed improved cycling stability (1876.4 mAh g compared with 1068.4 mAh g of the electrode with the pure PEDOT:PSS binder after 100 cycles) and superior rate capability (∼800 mAh g at an ultrahigh current density of 8.0 A g).
由于其固有的优异电学和电化学稳定性，聚（3,4-乙撑二氧噻吩）：聚苯乙烯磺酸盐（PEDOT:PSS）已被作为一种硅基粘合剂进行研究。然而，由于其线性结构，它不能有效缓解硅在锂化/脱锂过程中的巨大体积变化，导致循环稳定性较差。离子交联是将线性聚合物交联成三维结构的常用方法。在本文中，第5周期第2族的多价阳离子交联的PEDOT:PSS被用作硅阳极粘合剂并进行了系统研究。发现交联后PEDOT:PSS的粘度和电导率变化趋势与多价阳离子的离子势和柔软度参数一致。交联后粘合剂的介观结构受阳离子亚硫酸盐或氢氧化物的溶度积常数以及晶体生长特性的影响。由于其正的柔软度参数和较高的离子势，一种锡交联的粘合剂表现出粘度和电导率增加以及更高的压缩模量和硬度。具有锡交联粘合剂的硅电极显示出改善的循环稳定性（100次循环后为1876.4 mAh g，而纯PEDOT:PSS粘合剂电极的为1068.4 mAh g）和优异的倍率性能（在8.0 A g的超高电流密度下约为800 mAh g）。
