摘要
以单质硫为正极的锂硫电池表现出极高的放电比容量(1672 mAh·g^(-1)),是极具潜力的下一代二次动力电池。然而,充放电过程中溶解的高阶多硫化锂(Li_(2)S_(n),4≤n≤8)的穿梭效应,以及硫物种缓慢的氧化还原动力学过程是锂硫电池商业应用前需要解决的关键问题。而电化学催化的引入是解决上述问题行之有效的策略。本文从电化学催化角度出发,重新讨论认识多硫化物的存在形式,并从吸附-催化、活性中间体两个方面,根据不同的反应机理、路径分析多硫化物转化机制,总结定量评价催化性能方法,以期为锂硫电池高效电催化剂的设计提供思路。
Lithium-sulfur(Li-S)batteries have emerged as promising candidates for next-generation secondary power batteries given that they exhibit extremely high discharge specific capacity(1672 mAh·g^(-1))when sulfur is used as the positive electrode.Despite the potential of Li-S batteries for commercial applications,two significant issues need to be addressed:the shuttle effect of dissolved high-order lithium polysulfides(Li_(2)S_(n),4≤n≤8)during charge/discharge processes and the slow redox kinetics of sulfur species.Fortunately,the introduction of electrochemical catalysis is an effective strategy to mitigate the above problems.In the context of electrochemical catalysis,in this paper we discuss the existence forms of polysulfides and draw clear conclusions.Specifically,in ether electrolyte systems,the dominant form of polysulfide is the neutral molecule,while a smaller proportion exists as anions and cations.In addition,we also propose the corresponding solutions for different forms of polysulfides.Unlike previous reports,we analyze the conversion mechanism of polysulfides from two perspectives:adsorption-catalysis and reactive intermediates.In terms of the strength of the interaction force between the substrate materials and polysulfides,adsorption-catalysis can be classified into physisorption-catalysis and chemisorption-catalysis.The differences between both types are analyzed and discussed indepth.Additionally,the reactive intermediates are further classified into sulfur free radicals,thiosulfates,and organosulfur molecules based on different electrochemical reaction pathways.The mechanisms involved in the reactions of these intermediates are subsequently analyzed in detail.We also evaluate different strategies and list the types of catalysts that may correspond to each mechanism.Finally,the quantitative evaluation method of catalytic performance is also summarized,which paves a new way for the design of high-efficiency electrocatalysts in Li-S batteries.The nucleation transformation ratio(NTR)is a quantitative measure we developed to assess the catalytic properties of materials.When the reaction is ideal,the NTR should be equal to 3.A calculated NTR close to 3 indicates that the reaction from Li2S6 to Li2S4 occurs rapidly,suggesting that the material is highly catalytic to polysulfide nucleation.This quantitative approach enables researchers to determine the adsorption and catalytic effects of cathode materials on polysulfides,allowing the study of lithium-sulfur battery cathode materials to move from qualitative description to quantitative evaluation with specific factors.As a result,we can move from a qualitative description of lithium-sulfur battery cathode materials to their quantitative evaluation.
作者
汪涛
董琴
李存璞
魏子栋
Tao Wang;Qin Dong;Cunpu Li;Zidong Wei(College of Chemistry and Chemical Engineering,Chongqing University,Chongqing 400044,China;Suining Lithium Battery Research Institute of Chongqing University(SLiBaC),Suining 629000,Sichuan Province,China)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2024年第2期45-57,共13页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(22075033,U21A20312,91834301)资助项目。
关键词
锂硫电池
催化转化
电催化
化学吸附
硫自由基
Lithium-sulfur battery
Catalytic conversion
Electrocatalysis
Chemical adsorption
Sulfur radical
