过渡金属高熵氧化物的结构调控、形成机制及储锂性能研究

As a new multicomponent oxide, high entropy oxide with disordered cations configuration, high stability, excellent conductivity and wide varieties exhibit great application potential in the field of energy storage. This project takes the transition metal high-entropy oxide as the research objective and researches the composition and structure regulation, formation mechanism, doping modification and lithium storage mechanism. The high entropy oxides with salt rock structure and spinel structure would be prepared by high temperature solid phase method, and the structure evolution would be studied by variable temperature in situ XRD, the effect of single element on the formation of high entropy structure would be investigated, and the formation mechanism, structural regulation and control approach would be expounded. Furthermore, the defect concentration would be regulated by non - equivalent doping to improve its conductivity, and the charge compensation mechanism should be explained. The electrochemical storage of lithium in high entropy oxides would be studied systematically, the effects of composition and structure on performance would be investigated, the phase transition behavior of high entropy structure during charging and discharging and its influence on the transformation reaction would be studied by in-situ XRD and in-situ Raman techniques. We will delve into the differences between high entropy oxides and classical transition metal oxide, explain the mechanism of lithium ion storage. It provides theoretical guidance and experimental basis for scientific design, efficient preparation and application in energy storage of high entropy oxide materials.

高熵氧化物是一种阳离子无序排列的新型多组分氧化物，具有高稳定性、超高离子电导率、种类多样化等特点，在储能领域的应用潜力巨大。本项目以过渡金属高熵氧化物为研究目标，围绕其成分结构调控、形成机制、掺杂改性及储锂机理等展开研究。拟采用高温固相法制备盐岩结构和尖晶石结构高熵氧化物，利用变温XRD技术原位研究其结构演变过程，考察单一元素对高熵结构形成的作用，阐明其形成机制并揭示结构调控途径。此外，通过非等价掺杂调控其缺陷浓度，从而提高其电导率，并阐明电荷补偿机制。系统研究高熵氧化物的电化学储锂性能，考察其组成和结构对性能的影响，利用原位XRD和原位Raman技术研究高熵结构在充放电过程中的相变行为及其对转化反应的影响，深入挖掘高熵氧化物与经典过渡金属氧化物的差异，阐明其储锂机理，为高熵氧化物材料的科学设计、高效制备及其在储能领域应用等方面提供理论指导和实验依据。

电动汽车和大规模储能的快速发展对锂离子电池的能量密度和功率密度提出了更大的挑战。目前商业化的石墨负极理论容量有限，而高比容量的过渡金属氧化物仍存在体积膨胀严重，导电性差，不可逆容量大等问题。元素掺杂是目前最有效的改性手段之一。由于“高熵”材料能固溶多种过渡金属离子并保持单相结构，具有极大的储能潜力，但目前仍处于研究萌芽阶段，其形成机制和储能机制尚不清晰。针对以上现状，我们以高熵氧化物为对象，围绕其成分结构调控、形成机制、掺杂改性及储锂机理等展开深入研究。（一）我们采用高温固相法制备了系列尖晶石结构高熵氧化物，利用变温XRD研究了其结构演变过程，发现随着温度升高，原料中混合氧化物各自的物相逐渐消失，尖晶石结构逐渐出现，当温度升高900℃以上时，可获得纯净、高结晶度的单相尖晶石结构。（二）对(FeCoNiCrMn)3O4进行了不同组元的掺杂，发现在此结构基础上进行单一或多重元素掺杂不会明显影响其尖晶石结构，但会对晶胞参数，比表面积，形貌特性，电子结构，氧空位浓度，电化学反应电位等产生不同情况的影响，进而影响其储锂性能。（三）利用非原位XRD、XPS、TEM等手段对高熵结构在充放电过程中的相变行为进行了研究，发现其在一周循环后，普遍出现非晶化的现象，同时显著提高了氧空位浓度，进而提高了其导电性和结构稳定性。（四）本项目还拓展了关于钙钛矿结构和非晶结构高熵氧化物的研究，并在电催化领域的应用进行了相关探索。以上研究认为高熵氧化物在储能领域极具开发潜力。本项目对高熵氧化物的组分设计，高效制备，及储能应用提供了理论指导和实验依据。