摘要
富锂层状氧化物(LLOs)是下一代高容量锂离子电池正极材料的有利竞争者.然而,LLOs材料常掺杂的Co元素不仅价格昂高,且环境有害.因此,本工作使用价格便宜、环境友好的Fe元素代替Co,构建了具有聚集和分散LiMn_(6)的Li_(1.17)Ni_(0.17)Fe_(0.17)Mn_(0.49)O_(2)体系.使用密度泛函理论(DFT)计算方法对体系结构、氧化过程、氧释放焓、过渡金属离子迁移及Fe掺杂作用等进行了研究.研究发现,掺杂的Fe激活了更多的氧参与电荷补偿,分散的LiMn_(6)抑制了由Fe引起的Jahn-Teller效应畸变、氧的释放和Mn^(4+)的迁移,进而稳定了结构.特别需要指出的是不同环境O的活性不同,线性Li-O-Li中O是主要氧化还原中心,主导氧化还原反应;其次Fe-O-Li中O也参与氧化,LiTMO_(2)相O前期参与氧化,LiTMO_(2)与Li_(2)MnO_(3)相的边界O后期参与氧化.本工作为设计无Co且结构稳定容量高的锂离子电池富锂层状正极材料提供了新的见解.
Lithium-rich layered oxides(LLOs)are a favorable competitor for the next generation of high-capacity lithi-um-ion battery cathode materials.However,the doped Co in LLOs materials is not only expensive,but also harmful to the environment.Furthermore,in LLOs cathodes,the aggregation of Li_(2)MnO_(3)domains and lattice oxygen release lead to severe capacity/voltage degradation,ultimately impeding their commercial viability.Therefore,in this work,we substituted envi-ronmentally friendly and cost-effective Fe for Co,and designed two structural models—local distribution(LD)and delocal-ized distribution(DD)in the LiMn_(6)的Li_(1.17)Ni_(0.17)Fe_(0.17)Mn_(0.49)O_(2)system.A spin-polarized generalized gradient approximation(GGA)method with the PBE(Perdew-Burke-Ernzerhof)exchange-correlation functional was explored.A 2×2×1 supercell with a total of 96 atoms,namely Li_(28)Fe_(4)Ni_(4)Mn_(12)O_(48)is selected.We systematically investigated geometrical and electronic structures of DD and LD systems,oxidation processes,oxygen release enthalpy,transition metal ion migration and the role of Fe using density functional theory(DFT)calculations.It was found that the doped Fe activates more interfacial oxygen ions to partic-ipate to the charge compensation and disperses oxygen oxidation,thereby sharing the oxidation pressure of oxygen in the Li-O-Li configuration,which would be beneficial for suppressing the release of lattice oxygen.The dispersed LiMn_(6) in the Li_(1.17)Ni_(0.17)Fe_(0.17)Mn_(0.49)O_(2)system inhibits the Jahn-Teller distortion caused by Fe and the migration of Mn^(4+)ions,thus stabi-lizing the structures.Oxygen in the linear Li-O-Li structure serves as the primary redox center,driving the redox reactions.Additionally,oxygen in Fe-O-Li-based systems also participates in the oxidation process.Specifically,the oxygen in the LiTMO_(2)phase contributes to the early-stage oxidation,while oxygen at the interface between the LiTMO_(2) and Li_(2)MnO_(3)phases plays a role in the later stages of oxidation.This work provides new insights into the design of lithium-rich layered cathode materials without Co and with the high structural stability and the high capacity for lithium-ion batteries.
作者
张旭
郭鑫
张纪阳
刘继洪
祝佳鹏
黄超洋
黎明
贾桂霄
安胜利
Zhang Xu;Guo Xin;Zhang Jiyang;Liu Jihong;Zhu Jiapeng;Huang Chaoyang;Li Ming;Jia Guixiao;An Shengli(School of Materials Science and Engineering,Inner Mongolia University of Science and Technology,Inner Mongolia Key Laboratory of Advanced Ceramic Material and Devices,Key Laboratory of Green Extraction&Efficient Utilization of Light Rare-Earth Resources Inner Mongolia University of Science and Technology,Ministry of Education,Baotou 014010,China;School of Rare Earth Industry,Inner Mongolia University of Science and Technology,Baotou 014010,China;State Key Laboratory of Public Big Data,Guizhou University,Guiyang 550025,China)
出处
《化学学报》
北大核心
2025年第4期369-376,共8页
Acta Chimica Sinica
基金
国家自然科学基金(No.52262039)
内蒙古自治区自然科学基金(No.2024FX19)
内蒙古自治区直属高校基本科研业务费资助。
