金属活性位影响锂硫电池性能的微观机制

Lithium-sulfur battery is one of the most promising high-energy batteries, however, the dissolution of lithium sulfides greatly impeded the practical applications. Metal-based compounds can effectively prevent lithium sulfide from dissolving, nevertheless, the mechanism of the influence of activated metal sites is still unclear. Additional, our recent work demonstrated that the distribution of activated metal sites can heavily affect the performance of lithium-sulfur batteries, whereas the influence of activated metal sites has not been systematic studied, as well as its mechanism. Hereon, by using density functional theory calculation and molecular dynamics simulations, we will systematically study the effects of activated metal sites and their distributions on different surfaces of five kinds of MnO2. Through studying the distribution of activated metal sites and electronic structures of materials surfaces, the influence of distribution of activated metal sites on the electronic structures will be exposed, and the influence of activated metal sites on the structure stability also will be discussed. By exploring interactions between activated metal sites and lithium sulfides, the influence mechanism of the distribution of activated metal sites and electronic structures on the performance of the lithium-sulfur battery will be revealed. And then, materials properties, which can satisfy the practical applications, including distribution of activated metal sites and electronic structures will be summarized. The results of this proposal will promote the designing and synthesizing of metal-based electrode material of lithium-sulfur battery, deeply understand the interface properties of electrode, and improve the theoretical foundation of lithium-sulfur batteries.

锂硫电池是最具发展前景的新型高能电池之一，然而锂硫化物易溶解等问题严重制约了其实用进程。金属基化合物可有效抑制锂硫化物溶解，但金属活性位的影响机制依然不够清晰。重要的是，我们最近的研究发现金属活性位分布差异也会严重影响锂硫电池性能，但其作用机制尚不明确。基于此，本项目拟采用密度泛函计算与分子动力学模拟，以五种不同晶型MnO2为研究对象，系统研究表面金属活性位及其分布的影响。通过研究表面金属活性位及其分布、表面电子结构，总结表面金属活性位分布对电子结构性质的影响；分析金属活性位分布对结构稳定性的影响规律；探索表面金属活性位与锂硫化物分子间的相互作用关系；揭示表面金属活性位分布、电子结构性质影响锂硫电池性能的微观机制，总结符合实用需求的材料表面金属活性位分布规律与电子结构性质。研究结果将促进新型金属基锂硫电池电极材料的设计与合成，加深对锂硫电池电极表面与界面性质的认知，完善锂硫电池的基础理论。

锂硫电池是最具发展前景的新型高能电池之一，然而锂硫化物易溶解等问题严重制约了其实用进程。金属基化合物可有效抑制锂硫化物溶解，但金属活性位的影响机制依然不够清晰。尽管已有研究发现金属活性位分布差异也会严重影响锂硫电池性能，但其作用机制不够明确。此外，锂硫电池电极材料限制锂硫化物溶解以及穿梭的基本科学原理依然不够清楚。基于此，本项目采用密度泛函计算与分子动力学模拟，系统研究了MnO2材料不同表面上氧含量差异的影响，探索了不同金属氧化物中锂硫化物的表现，探究了材料表面与电解液之间的竞争机制，尤其是对锂硫化物的吸引作用。通过这些研究我们发现，氧含量差异导致的配位特性变化，从而改变金属位点的电子分布特性，这会提升电子在电化学反应过程中的迁移机制，从而改变电化学性能。而表面具有的强吸附作用则可以有效地抑制锂硫化物与电解液之间的相互作用，从而抑制其溶解，降低穿梭效应，提升锂硫电池性能。上述研究结果，对设计与合成新型金属基锂硫电池电极材料具有理论指导作用，为促进低成本高性能锂硫电池的开发和发展提供科学基础，加深了对锂硫电池电极表面与界面性质的认知，进一步完善锂硫电池的基础理论，同时还深入地理解了金属氧化物的性质，为其多元化应用提供理论基础。