College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P. R. China.
Langmuir. 2016 Dec 27;32(51):13778-13786. doi: 10.1021/acs.langmuir.6b03001. Epub 2016 Oct 25.
Residual Mg reduces the performance of lithium-ion batteries. However, separating Mg and Li is difficult because of their similar ionic properties. Inspired by the high selectivity of biological Mg channels, this work utilizes atomistic simulations to investigate the ability of graphene-based nanopores with diameters of 0.789, 1.024, and 1.501 nm to separate Mg and Li under a series of transmembrane voltages. We analyzed the spatial distribution of molecules in the nanopores' vicinity, structure properties of ionic hydration, and potential of mean force of ions traveling through the nanopores. Separation was mainly caused by the difference in dehydration between the second hydration shells of Mg and Li. When ions traveled through nanopores, Li had to overcome a greater energy barrier than Mg because it had to shed more water molecules and break more hydrogen bonds in the second hydration shell compared with Mg. Moreover, the ionic Coulomb blockade of Mg occurred near the pore mouth, impeding Li transport and increasing selectivity when the pore diameter decreased to subnanometer.
残留的镁会降低锂离子电池的性能。然而，由于它们具有相似的离子特性，因此分离镁和锂很困难。受生物镁通道高选择性的启发，本工作利用原子模拟研究了直径为 0.789、1.024 和 1.501nm 的基于石墨烯的纳米孔在一系列跨膜电压下分离镁和锂的能力。我们分析了纳米孔附近分子的空间分布、离子水合结构特性以及离子通过纳米孔的平均力势。分离主要是由于镁和锂的第二水合壳的去水化程度不同造成的。当离子穿过纳米孔时，由于与镁相比，它必须脱去更多的水分子并破坏第二水合壳中的更多氢键，因此需要克服更大的能量障碍。此外，当孔径减小到亚纳米级时，镁的离子库仑阻塞发生在孔口附近，阻碍了锂的传输，从而提高了选择性。
