Cathode-solid electrolyte interfaces

全固态电池的一个主要变化是设计具有足够顺应性的阴极，以避免活性颗粒膨胀或收缩时的高应力，从而在充电和放电时保持接触。实际的阴极如NMC是强氧化性的，因此通常在界面处降解固体电解质。已经研究了LiTaO 3和LiNbO 3涂层以抑制反应性，但是机械问题仍然存在。陶瓷涂层是不柔顺的，并且倾向于随着活性颗粒充电或放电而分离。为了了解复合电极内体积变化的影响，学生将直接比较零应变活性材料，如Li 4 Ti 5 O 12，与体积变化材料，如LixNb 16 W5 O 55和LixTiS 2。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，因为与隔膜（10 μ m）相比，阴极（80-100 μ m）中较长的路径长度需要更高的离子电导率。比较LixNb 16 W5 O 55和LixTiS 2将显示电极硬度如何影响界面完整性。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。学生将接受电化学表征（3电极电池）和阻抗谱，等离子体FIB SEM，样品细化和TEM，操作中X射线断层扫描，XPS和EDX的形态学研究的培训。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