Yoo Dong-Joo, Elabd Ahmed, Choi Sunghun, Cho Yunshik, Kim Jaemin, Lee Seung Jong, Choi Seung Ho, Kwon Tae-Woo, Char Kookheon, Kim Ki Jae, Coskun Ali, Choi Jang Wook
School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea.
Department of Chemistry, University of Fribourg, Chemin de Musee 9, Fribourg, 1700, Switzerland.
Adv Mater. 2019 Jul;31(29):e1901645. doi: 10.1002/adma.201901645. Epub 2019 May 30.
Despite their unparalleled theoretical capacity, lithium-metal anodes suffer from well-known indiscriminate dendrite growth and parasitic surface reactions. Conductive scaffolds with lithium uptake capacity are recently highlighted as promising lithium hosts, and carbon nanotubes (CNTs) are an ideal candidate for this purpose because of their capability of percolating a conductive network. However, CNT networks are prone to rupture easily due to a large tensile stress generated during lithium uptake-release cycles. Herein, CNT networks integrated with a polyrotaxane-incorporated poly(acrylic acid) (PRPAA) binder via supramolecular interactions are reported, in which the ring-sliding motion of the polyrotaxanes endows extraordinary stretchability and elasticity to the entire binder network. In comparison to a control sample with inelastic binder (i.e., poly(vinyl alcohol)), the CNT network with PRPAA binder can endure a large stress during repeated lithium uptake-release cycles, thereby enhancing the mechanical integrity of the corresponding electrode over battery cycling. As a result, the PRPAA-incorporated CNT network exhibits substantially improved cyclability in lithium-copper asymmetric cells and full cells paired with olivine-LiFePO , indicating that high elasticity enabled by mechanically interlocked molecules such as polyrotaxanes can be a useful concept in advancing lithium-metal batteries.
尽管锂金属阳极具有无与伦比的理论容量，但它们存在众所周知的枝晶无差别生长和寄生表面反应问题。具有锂吸收能力的导电支架最近被视为有前景的锂宿主，而碳纳米管（CNTs）因其能够渗透形成导电网络，是实现此目的的理想候选材料。然而，由于在锂吸收-释放循环过程中产生的巨大拉伸应力，CNT网络容易破裂。在此，报道了通过超分子相互作用将含聚轮烷的聚丙烯酸（PRPAA）粘合剂整合到CNT网络中，其中聚轮烷的环滑动运动赋予整个粘合剂网络非凡的拉伸性和弹性。与具有无弹性粘合剂（即聚乙烯醇）的对照样品相比，具有PRPAA粘合剂的CNT网络在重复的锂吸收-释放循环中能够承受较大应力，从而在电池循环过程中增强了相应电极的机械完整性。结果，掺入PRPAA的CNT网络在锂-铜不对称电池和与橄榄石型LiFePO₄配对的全电池中表现出显著改善的循环性能，表明由聚轮烷等机械互锁分子实现的高弹性在推进锂金属电池发展方面可能是一个有用的概念。
