基于莫特-肖特基异质结定向催化机制的锂硫电池正极研究

锂硫电池理论能量高、成本低，被认为是最有前景的新一代高能量密度电池器件之一。然而，循环过程中多硫化锂的穿梭效应导致容量快速衰减，严重阻碍了锂硫电池的商业化应用。本项目拟通过构筑具有本征特性的莫特-肖特基异质结的手段，通过诱导表面电荷定向分布，构筑界面贫/富电区，进而通过内建电场选择性激活硫的氧化和还原反应。富电区加速S8的还原反应，贫电区加速Li2S的氧化反应。这两者之间形成的异质界面加速Li+的传输速率，降低反应能垒，特别是加速Li2S2和Li2S之间的转化反应，从而获得快的氧化和还原反应动力学，抑制多硫化物穿梭效应，实现高比能长循环锂硫电池电化学性能。为此，通过阐明莫特-肖特基异质结和3D多孔石墨化碳以及导电聚合物之间的协同作用，揭示电催化剂高效的氧化和还原反应活性位点的空间分离和快速的电子和离子迁移机制，为高活性催化剂机制的高比能长循环锂硫电池的设计提供实验和理论上的借鉴和新的理解。

Lithium-sulfur batteries are considered as one of the most promising next-generation high-energy-density storage devices due to their advantages of high theoretical energy and low cost. However, the rapid capacity attenuation caused by the shuttle effect of lithium polysulfides in the cycle process seriously impedes the commercial application of lithium-sulfur batteries. This project aims to develop a novel Mott-Schottky heterojunction electrocatalyst to improve and stabilize the electrochemical performance of lithium-sulfur batteries. Based on the intrinsic characteristics of the Mott-Schottky heterojunction, the electron-rich and electron-poor areas can be established at the heterojunction interface by inducing the directional distribution of surface charge, thereby leading to the generation of a built-in electric field, which can further selectively activate the oxidation and reduction of sulfur. The electron-rich zone accelerates the reduction of S8, while the electron-poor zone expedites the oxidation of Li2S. Meanwhile, the created heterogeneous interface can accelerate the Li+ transfer rate, reduce the reaction energy barrier, and especially promote the transformation reaction between Li2S2 and Li2S, which thereupon result in fast oxidation and reduction reaction kinetics, inhibition of the shuttle effect of polysulfide, and acquisition of lithium-sulfur batteries with the high specific energy and long lifespan. Moreover, by illustrating the synergy effect among Mott-Schottky heterojunction, 3D porous graphitized carbon, and conductive polymers, revealing the high-efficiency electrocatalysts with the spatial separation of the efficient oxidation/reduction active sites, and investigating the mechanism of rapid electron and ion migration, this project will provide valuable experimental and theoretical reference as well as new understanding for the design of high-specific-energy and long-cycle lithium-sulfur batteries.