硫化物@碳（壳）调控硫化硒（核）储锂性能、反应动力学及其机理研究

Lithium-sulfur (Li-S) battery is one of the promising next-generation power batteries. However, several fundamental problems impeding the practical applications of Li-S battery originate from the low areal loading, poor utilization, and unsatisfactory cycle performance of sulfur active material. Given spherical core-shell structure with the advantage of high sulfur loading capacity and high tap density, this project focuses mainly on the following issues for developing the high-energy density Li-S battery: (1) The microscopic compositions and structures of the spherical sulfides/carbon@selenium sulfides core-shell structured material would be rationally designed to efficiently confine/adsorb the soluble polysulfides, facilitate the electron transport, and further achieve the long-term durability/stability of the electrical conduction and contact between core and shell during the cycling. (2) The electrochemical activities and stabilities of sulfides reaction with lithium for sulfur/polysulfides binding are systematically studied, and the unveiled influence rule and internal mechanism can provide the theoretical foundation for the design of sulfur adsorbents with low cost, high conductivity, and high efficiency. (3) The effect of shell on the lithium storage and reaction kinetics of core is clarified, and the essence of battery performance evolution is revealed as well. Following these efforts, the structure of the target product is further optimized with the purpose of achieving high-loading, high-power, and long-period performance. The research results can also provide a valuable reference for the construction of the in-situ characterization method monitoring electrode surface/interface and lay a theoretical foundation for the technical breakthrough in power-type Li-S batteries.

锂硫电池是前景极佳的下一代动力电池体系之一；然而，硫基正极活性物质存在载量低、利用率低和循环性差等缺点制约了其应用发展。本项目以高能量密度锂硫电池的开发为导向，针对球形壳核材料具有载硫量大、振实密度高等突出优势，拟开展以下研究：（1）设计硫化物@碳（壳）-硫化硒（核）球状正极材料，实现其微组分/微结构的可控调变，使限域、导电、固硫高效协同，注重维持循环过程中外壳与内核电导性和电接触的长效性与稳定性；（2）阐明硫化物电化学活性与循环稳定性对固硫作用的影响规律及内在机制，为低成本、高导电、高效能固硫剂的设计提供理论支撑和优化依据。（3）探究外壳对内核储锂性能和反应动力学的调变作用及规律，揭示电池性能演变的本质原因，优化结构使目标硫基壳核材料兼备高载量、大功率、长寿命性能。项目研究还可为电极表界面原位表征方法的构建提供富有借鉴的思路和启发，为动力型锂硫电池技术的突破奠定理论基础。

硫基壳核正极材料存在高固硫能力外壳与高载硫内核电子电导率难以协调匹配的问题，同时外壳材料自身电化学活性与稳定性对固硫作用机制仍不明确。据此，本项目设计了一系列结构或组分新颖的宿主，系统地探究了它们对元素硫电化学活性的促进与催化作用和对多硫化锂的吸附与转化等作用。项目研究取得的结果、重要数据和科学意义，主要包括：①立足项目特色与创新之处，系统地总结并评述了金属硫化物的设计、合成与应用研究进展，此为本领域的发展指明了重要方向；②开发出结构新颖的氮掺杂碳限域封装的ZnS/SnS2纳米片异质结，成功使限域、导电、固硫协调统一，有效解决了外壳与内核电导性和电接触长效性与稳定性，为低成本、高导电、高效能固硫剂的设计提供了优化依据；③设计出组分新颖的双功能Ni/Zn双掺杂CoSe2以增强CoSe2的催化效果进而提高锂硫电池的反应动力学，此为高载量、大功率、长寿命硫基正极材料的设计与优化提供了理论支撑；④构筑新型载硫宿主期间，项目亦开展了一些储锂/钠/钾的研究工作，主要涉及从微观晶体结构（掺杂、缺陷、异质结）或形貌（零维、一维、二维以及特殊三维结构）设计到导电复合材料构筑等，以期解决当下电极材料面临的储能机制不详、动力学迟缓、倍率性能低下以及循环稳定性不佳等问题。总之，本项目研究结果可为研发具有自主知识产权的下一代高比能二次电池技术提供重要的理论基础和技术指导。