高效离子筛分修饰纳米纤维隔膜的构筑及其在锂硫电池中的应用基础

Aiming at the dissolution of lithium polysulfur intermediate and the shuttle effect in lithium-sulfur batteries, the project propose a new ion-sieving layer modified nanofiber composite membrane as a high performance separator used for lithium-sulfur batteries. Through the design of highly porous 3D nanofibers to achieve high electrolyte loading mass and fast Li+ diffusion rate, improve the lithium polysulfur adsorption by introducing high polar nanoparticles to the nanofibers , introducing the ion-sieving layer to modified the nanofiber membrane to block the polysulfur diffusion based on the difference electronegativity and radius of the Li ion and lithium polysulfur, realizing the effective blocking of the polysulfide ions and then inhibit the shuttle effect of polysulfur, and finally improve the electrochemical properties of the lithium-sulfur batteries. The research includes the preparation of nanofiber composite membrane, the design of high performance ion sieving layer, the influence of the three-dimensional structure and composition on electrolyte infiltration, polysulfur blocking, Li+ transportation and then electrochemical performance. The project will focus on the design of separator structure, and the influence of modified ion seiving layers on lithium polysulfur barrier and related electrochemical properties from the theoretical level, clarify the internal mechanism effect of ion-sieving modified layer on the membrane/electrolyte interface reaction. On the technical level, developing the functional membrane with high lithium polysulfur seive efficiency and rapid lithium ion transfer rate. The research results will provide theoretical and technical basis for the preparation and application of the separator used for lithium-sulfur batteries, which has important scientific significance and practical value.

针对目前锂硫电池中间产物多硫离子溶解及穿梭效应等问题，本项目提出设计离子筛分功能化纳米纤维复合隔膜用于锂硫电池体系。通过纳米纤维的高孔隙实现高电解液负载和锂离子传输速率；引入高极性颗粒提高隔膜对多硫离子的吸附作用；并利用多硫离子和锂离子的正负电性和半径的差异，设计离子筛分修饰层，实现对多硫离子的有效截流，抑制穿梭效应，最终实现电池电化学性能的提升。研究内容包括复合纳米纤维薄膜的制备，高效离子筛分修饰层的设计，隔膜结构/组成对电解液浸润、Li+传输、多硫离子阻隔乃至电化学性能的影响。本项目将从理论层面研究隔膜组成、结构、修饰层等对多硫离子阻隔乃至电化学性能的影响规律，阐明离子筛分修饰层影响隔膜/电解液界面反应的内在机制。从技术层面上，研制出高效多硫离子筛分和快速锂离子传输的功能化隔离膜，建立完善的制备工艺。研究成果将为锂硫电池隔离膜制备和应用提供理论和技术基础，具有重要的科学意义和实用价值。

本项目针对目前锂硫电池中间产物多硫离子溶解及穿梭效应等问题，提出设计系列功能化复合修饰层用于锂硫电池隔膜修饰，有效改善多硫化锂穿梭效应，提高锂硫电池的电化学性能。开发了M-N-C（Fe-N-C及Co-N-C）及碳纳米纤维复合修饰层、二维MoN纳米片修饰层，密堆MnO2纳米颗粒层等，这些超轻薄功能化的修饰层的引入保证了良好的锂离子传输，有效抑制了多硫化锂的穿梭效应，促进硫的氧化物还原反应，保证快速反应动力学，提高了硫正极的利用率，最终实现电池性能的提升。项目研究成果为锂硫电池隔离膜制备和应用提供理论和技术基础，具有重要的科学意义和实用价值。在此基础上，我们还将研究拓展到固态电解质方面的研究，开发了二维纳米片复合的PEO基聚合物电解质，发展了流延法制备超薄氧化物电解质薄膜的制备工艺，所得的固态电解质用于全固态锂电池的组装，大幅提升电池的安全性能。