锂硫电池具有极高的理论能量密度，是具有应用前景的下一代高比能电池体系。多硫化物的固–液–固转化保证了锂硫电池的高比能，但是锂硫电池的实用化仍面临循环寿命短的问题。实用化条件下多硫化物与金属锂负极持续反应，导致有限活性锂和多硫化物快速消耗，造成锂硫电池容量快速衰退。因此，调控锂硫电池负极界面反应机制，以抑制金属锂负极和多硫化物持续反应，是提升锂硫电池循环寿命和推动锂硫电池实用化的关键。针对多硫化物与金属锂负极反应动力学快的问题，分析电解液中多硫化物的溶剂化结构，提出封装多硫化物电解液设计，即通过引入还原稳定、弱溶剂化能力的共溶剂占据外层溶剂壳，构筑纳米异质的双层溶剂壳层以封装多硫化物，动力学上抑制多硫化物和金属锂负极的反应。进而论证了封装多硫化物设计的一般性，验证削弱外层溶剂的溶剂化能力可以提升封装多硫化物的效果。针对固态电解质界面膜（SEI）不稳定导致金属锂和多硫化物持续反应的问题，提出增强SEI均匀性和机械稳定性以阻断多硫化物和金属锂反应路径的思路。将经典硝酸锂添加剂改造为硝酸异山梨酯，促进硝酸酯优先分解构筑富含氮氧化物的SEI；分析含硫组分对SEI均匀性的作用并构筑富含硫氧化物的SEI以提升SEI的均匀性，提升锂沉积均匀性。在保证SEI均匀性基础上，利用三聚甲醛的优先分解和强聚合性质构筑富含有机物的高机械稳定性SEI，缓解充放电过程中负极体积形变导致的SEI破裂，减弱多硫化物和金属锂的界面反应。针对实用化锂硫电池循环寿命短的问题，采用高硫面载量、低电解液用量、有限金属锂条件构筑安时级软包电池，实现电芯级别400 Wh?kg?1的能量密度。在软包电池尺度通过封装多硫化物的溶剂化结构设计和SEI稳定性设计，降低金属锂负极和多硫化物的消耗速率，将350 Wh?kg?1软包电池的循环寿命提升1倍，并实现400 Wh?kg?1软包电池27圈循环。综上所述，本论文在理解锂硫电池中多硫化物和金属锂界面反应机制的基础上，提出了多硫化物溶剂化结构设计、SEI均匀性和机械稳定性设计的界面反应调控思路，有助于推动实用化高比能锂硫电池的发展。

Lithium–sulfur (Li–S) batteries are considered as one of the most promising next-generation high-energy-density batteries due to the ultrahigh theoretical energy density. The multistep solid–liquid–solid conversion of the S cathode involving Li polysulfide (LiPS) intermediates basically ensures the high energy density and the S cathode has gained momentum recently. However, practical Li–S batteries are severely hindered by the unsatisfactory cycle lifespan. Limited Li metal anodes react with LiPSs, resulting in the consumption of active Li and LiPSs and further the rapid decay of battery capacity. Therefore, regulating the reaction mechanism on anode interface to suppress the continuous interfacial reactions is vital for prolonging the cycle lifespan and promoting the practical application of Li–S batteries.To slow the reaction kinetics of LiPSs with Li metal anodes, the basic solvation structure of LiPSs was disclosed in routine ether electrolyte. An encapsulating-LiPS electrolyte (EPSE) was proposed to encapsulate LiPSs to suppress the parasitic reactions of LiPSs on Li metal anodes. EPSE was achieved by introducing reduction-stable and weakly solvating co-solvents to construct nano-heterogeneous double solvent shells around LiPSs. The generality of EPSE design was demonstrated and the effect of EPSE was improved by reducing the solvation power of the outer solvent.To suppress the continuous reactions between Li metal anodes and LiPSs due to the instability of solid electrolyte interfacial interphase (SEI), it is proposed to improve the uniformity and mechanical stability of SEI. The classical lithium nitrate additive was modified to nitrate molecules with non-resonant structure by molecular scale design. Homogeneous LiNxOy-rich SEI was formed by the preferential decomposition of nitrate. The role of sulfur-containing components in SEI was analyzed, and lithium oxysulfide-rich SEI was designed to improve the uniformity of SEI and Li deposition. As for the easy fracture of SEI, an innovative electrolyte with 1,3,5-trioxane (TO) as co-solvents was proposed for Li–S batteries. TO with high polymerization capability can preferentially decompose and form organic-rich SEI, strengthening the mechanical stability of SEI. The SEI with high mechanical stability mitigates the crack of SEI during volume change of anodes and reduces the consumption rate of active Li and LiPSs.To address the problem of short cycle life of practical Li–S batteries, pouch cells with ampere-hour level were constructed under the conditions of high S loading, low electrolyte usage, and limited Li metal anodes, achieving an energy density of 400 Wh?kg?1 at the cell level. Solvate structure design of LiPSs and SEI stability design were utilized in the pouch cells to reduce the consumption rate of Li metal anodes and LiPSs. The cycle life of the 350 Wh?kg?1 pouch cell was doubled and the 400 Wh?kg?1 pouch cells stably operate 27 cycles.In summary, on the basis of understanding the reaction mechanism between Li metal anodes and LiPSs, the regulation of polysulfide solvation structure and the uniformity and mechanical stability of SEI was proposed to inhibit the interfacial parasitic reactions. This contribution is helpful for promoting the development of practical high-energy-energy Li–S batteries.