Cathode-solid electrolyte interfaces

全固态电池的一个主要挑战是设计具有足够柔顺性的阴极，以便在活性粒子膨胀或收缩时避免高应力，以便在充放电时保持接触。像NMC这样的实用阴极是强氧化的，因此通常会在界面上降解固体电解质。已经研究了LiTaO_3和LiNbO_3涂层来抑制反应性，但机械问题仍然存在。陶瓷涂层不顺应，随着活性颗粒的充放电而容易脱落。为了了解复合电极中体积变化的影响，学生将直接将零应变活性材料(如Li4Ti5O12)与体积变化材料(如LixNb16W5O55和LixTiS2)进行比较。这将使体积效应与表面现象分离。该项目将侧重于硫化物固体电解质，因为与分离器(10微米)相比，阴极(80-100微米)的路径较长所需的离子导电率更高。通过比较LixNb16W5O55和LixTiS2，可以看出电极硬度对界面完整性的影响。阴极/固体电解质界面将作为充电状态、循环、电流密度、温度和压力的函数进行研究。学生将接受有关电化学表征(三电极电池)和阻抗光谱学、等离子体FIB扫描电子显微镜的形态研究、样品稀释和透射电子显微镜、术中X射线断层扫描、XPS和EDX的培训。等静压将与电化学相结合，以建立复合材料的机械响应。EPSRC研究领域主题：能源

A major challange in all-solid-state batteries is to design cathodes with sufficient compliance that high stresses are avoided when active particles swell or contract, so that contact is maintained upon charge and discharge. Practical cathodes like NMC are strongly oxidising, and so generally degrade solid electrolytes at interfaces. LiTaO3 and LiNbO3 coatings have been investigated to suppress reactivity, but the mechanical problems remain. Ceramic coatings are not compliant, and tend to detach as active particles charge or discharge. To understand the impact of volume changes within composite electrodes the student will compare directly zero-strain active materials, such as Li4Ti5O12, with volume-change materials, e.g. LixNb16W5O55 and LixTiS2. This will decouple volume effects from surface phenomena. The project will focus on sulphide solid electrolytes because of the higher ionic conductivities required for the longer path lengths in cathodes (80-100 mu m) compared with the separator (10 mu m). Comparing LixNb16W5O55 and LixTiS2 will show how electrode hardness affects interfacial integrity. The cathode/solid electrolyte interface will be studied as a function of charge state, cycling, current density, temperature, and pressure. The student will be trained on electrochemical characterisation (3-electrodes cells) and impedance spectroscopy, morphology studies by plasma-FIB SEM, sample thinning and TEM, in-operando X-ray tomography, XPS, and EDX. Isostatic pressing will be combined with electrochemistry to establish the mechanical responses of composites.EPSRC Research Area Theme: Energy