Liao Junbin, Liu Zhen, Wang Jianli, Ye Zhibin
Bharti School of Engineering, Laurentian University, Sudbury, Ontario P3E 2C6, Canada.
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China.
ACS Omega. 2020 Apr 1;5(14):8272-8282. doi: 10.1021/acsomega.0c00666. eCollection 2020 Apr 14.
Binder, as one of the key components, plays a crucial role in improving the capacity and cycling performance of lithium-sulfur (Li-S) batteries. In this work, commercially available, low-cost, water-soluble polyvinyl alcohol (PVA) has been systematically investigated as a functional polymer binder for high-sulfur-loading cathodes, with the aim of enhancing sulfur utilization, reducing capacity decay, and extending cycling life of the cathodes. In comparison with polyvinylidene fluoride as a conventional binder, PVA shows a valuable polysulfide entrapping ability and a much stronger binding strength. Its superior polysulfide entrapping ability has been verified through theoretical density functional theory calculations and an experimental adsorption study. In electrochemical Li-S battery performance evaluation, at a sulfur loading density of 3.5 mg cm, the sulfur cathode assembled with the PVA binder displays at 0.5 C a very slow capacity decay of only 0.010% per cycle over 250 cycles. Additionally, the strong binding strength of PVA allows the fabrication of thick sulfur cathodes with a high sulfur loading density of 10.5 mg cm, which shows a high areal capacity of 4.0 mA h cm and a high cycling stability (capacity decay of 0.1% per cycle). In consideration of the superior capacity retention and cycling performance of its enabled cathodes, the cost-effective PVA is a promising candidate for high-sulfur-loading cathodes in practical applications.
粘结剂作为关键部件之一，在提高锂硫（Li-S）电池的容量和循环性能方面起着至关重要的作用。在这项工作中，已对市售的低成本水溶性聚乙烯醇（PVA）作为高硫负载阴极的功能聚合物粘结剂进行了系统研究，目的是提高硫的利用率、减少容量衰减并延长阴极的循环寿命。与作为传统粘结剂的聚偏二氟乙烯相比，PVA具有宝贵的多硫化物捕获能力和更强的结合强度。其优异的多硫化物捕获能力已通过理论密度泛函理论计算和实验吸附研究得到验证。在电化学Li-S电池性能评估中，在硫负载密度为3.5 mg cm时，用PVA粘结剂组装的硫阴极在0.5 C下250次循环中每循环的容量衰减非常缓慢，仅为0.010%。此外，PVA的强结合强度使得能够制造硫负载密度高达10.5 mg cm的厚硫阴极，其显示出4.0 mA h cm的高面积容量和高循环稳定性（每循环容量衰减0.1%）。考虑到其使能的阴极具有优异的容量保持率和循环性能，成本效益高的PVA在实际应用中是高硫负载阴极的一个有前途的候选材料。
