South China Advanced Institute for Soft Matter Science and Technology, School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou 510640, China.
Nano Lett. 2023 Jun 14;23(11):5194-5200. doi: 10.1021/acs.nanolett.3c01171. Epub 2023 May 23.
Solid polymer electrolytes (SPEs) are attractive for next-generation lithium metal batteries but still suffer from low ionic conductivity. Nanostructured materials offer design concepts for SPEs with better performance. Using molecular dynamics simulation, we examine SPEs under nanoscale confinement, which has been demonstrated to accelerate the transport of neutral molecules such as water. Our results show that while ion diffusion indeed accelerates by more than 2 orders of magnitude as the channel diameter decreases from 15 to 2 nm, the ionic conductivity does not increase significantly in parallel. Instead, the ionic conductivity shows a nonmonotonic variation, with an optimal value above, but on the same order as, its bulk counterparts. This trend is due to enhanced ion association with decreasing channel size, which reduces the number of effective charge carriers. This effect competes with accelerated ion diffusion, leading to the nonmonotonicity in ion conductivity.
固体聚合物电解质（SPE）在下一代锂电池中具有吸引力，但仍存在离子电导率低的问题。纳米结构材料为具有更好性能的 SPE 提供了设计理念。我们使用分子动力学模拟研究了纳米受限条件下的 SPE，这种受限条件已被证明可以加速中性分子（如水）的传输。我们的结果表明，尽管随着通道直径从 15nm 减小到 2nm，离子扩散确实加速了两个数量级以上，但离子电导率并没有同步显著增加。相反，离子电导率呈非单调变化，在通道尺寸减小时出现峰值，其值高于但与本体值相当。这种趋势是由于随着通道尺寸的减小，离子缔合增强，有效载流子数量减少。这种效应与加速的离子扩散竞争，导致离子电导率呈非单调变化。
