功能多孔骨架材料核心位点修饰及锂离子传导机理研究

Ion motion in lithium secondary battery has a strong directivity. Li+ ions tend to migrate to the anode while anions tend to migrate to the cathode during the charge process. However, Li+ ions move slower than anions due to the bulky solvation shell, which leads to the accumulation of anions near the cathode surface and thus a buildup of the concentration gradient. This concentration gradient limits the fast charge property and energy density of the cells. In this program, a new type of porous material with ordered pore channels will be applied to construct ion conductor to improve ion migration in battery. The pore channels inside the target porous materials possessed abundant unsaturated metal sites (or open metal sites) which could provide strong affinity toward guest molecules through bonding. Moreover, the uniformly distributed nano-size pore channels in the material provide confinement effect on the guest molecules, leading to much improved guest density. Due to these properties, this type of material has been intensively studied for the storage or separation of small molecules, like H2 and CH4 gas. It could also be an ideal candidate as ion conductor to tune the ion migration behaviors in batteries. Several ion conductors will be prepared based on the porous material and the microstructure and surface chemistry of the pore channels will be first studied. The spatial distribution and migration tendency of the anions, cations and solvent molecules will be studied by neutron diffraction with or without external stimulus. The proposed study will provide theoretical instruction for the optimization of lithium conducting and transport in batteries, and be significant for the development of new solid electrolytes.

离子在锂二次电池中的运动具有强的方向性，在充电过程中带正电的锂离子向负极移动，带负电的阴离子向正极移动。锂离子由于溶剂化外壳迁移较慢，导致阴离子更多的聚集在正极附近，电池产生浓差极化，限制了电池快充能力和能量密度的提升。本项目将开发一种具有规则孔道结构的新型多孔材料，由于该材料内部开放金属位点的键合作用和纳米空间的限域作用，具备筛选客体小分子的性能，可以用来作为离子导体，调控电池内部离子的迁移，实现高的锂离子数。本研究将系统调控材料孔道的微观结构和化学特性，利用中子探测技术和外界条件刺激，研究离子、溶剂等在多孔材料内部的占有位置和迁移规律，为锂离子输运优化提供理论指导，对新型固态电解质的开发及实际应用也具有重要意义。

采用固态电解质替代传统有机电解液，构筑全固态电池，有望显著提高电池能量密度，同时提升电池安全性能，是新能源汽车和储能等理想的化学电源，极具发展前景。但是，全固态电池走向应用还面临诸多挑战，其中重要的一点是高性能固态电解质核心材料缺失。针对这一问题，本项目从基于第一性原理的理论设计出发，模拟筛选具有快离子传输通道和室温结构稳定的新物相/组分，积极探索电解质合成方法和工艺，深入开展晶体场优化调控，发展形成了几种具有高离子电导率（>1 mS/cm）和良好电极兼容性的新型卤化物固态电解质，并探索了在全固态电池器件中的应用，结合先进同步辐射X射线衍射、中子衍射和全散射方法，深入研究了电解质新材料结构，并揭示了新结构中离子输运机制。研究结果对于高性能固态电解质材料开发以及全固态电池器件应用具有重要的指导作用。