Spatial and time resolved powder diffraction

目前，阴极是商业电池中的能量密度限制部件。然而，根据活性材料的特性估计的能量密度（容量、电压、活性和非活性材料的密度）远不是最终电池性能的精确估计。1由于活性Li+和阴极降解反应的消耗而导致的电极平衡高度依赖于所施加的负载分布，进一步限制了商业电池的能量密度。2此外，电池设计（电池格式、“果冻卷”的尺寸和数量、集电器的位置等）在充电和放电中引入不均匀性，导致应力和沿电极沿着的退化程度的空间变化。3.我们建议通过改变电流、温度和电压窗口，在DLS的I11晶体学光束线上使用空间分辨粉末衍射来研究沿电极的沿着不均匀性。低仪器反射展宽，以及长时间测量的可能性，将使我们能够监测应力的演变，过渡金属运动，不可逆的结构变化和长期循环后的平衡变化。由于应力取决于充电状态，并且在充电和放电过程之间可能不同，因此测量将利用I11处的时间分辨粉末衍射能力。长时间实验将与锁定热成像相结合，以帮助理解热演化沿着果冻卷。5小热点可能足以引发热失控，因此这项工作也涉及安全方面。[1]Andre等人，杰·板牙。A 2015，3，6709中所述。[2]Kleiner等人，Top. Curr. 2017，375，45. [3]Kleiner等人，J. Power Sources 2016，317，25. [5]罗宾逊等人，ECS Electrochem. Lett. 2015年4月9日。

Currently, the cathode is the energy density limiting component in commercial batteries. However, the energy densities estimated from the characteristics of the active material (capacity, voltage, density of active and inactive material) are far from being a precise estimate of the final cell performance.1 The electrode balancing due to the consumption of active Li+ and cathode degradation reactions, highly dependent on the applied load profile, further limit the energy densities of commercial cells.2 Moreover, the cell design (cell format, size and number of 'jelly rolls', position of current collectors, etc.) introduces inhomogeneities in the charge and discharge, leading to stress and a spatial variation in the degree of degradation along the electrodes. 3 We propose to study the inhomogeneities along the electrodes using spatially resolved powder diffraction at the I11 crystallography beamline at DLS by varying the current, the temperature and the voltage window. The low instrumental reflection broadening, as well as the possibility of long duration measurements, will allow us to monitor the evolution of stress, transition metal motion, irreversible structural changes and changes in the balancing upon long-term cycling. As stress is state-of-charge dependant, and might differ between charge and discharge processes, measurements will take advantage of the time resolved powder diffraction capabilities at I11. Long duration experiments will be combined with lock-in thermography in order to help understand the heat evolution along a jelly roll.5 Small hot spots can be enough to initiate a thermal runaway, and thus this work also addresses safety aspects.[1] Andre et al., J. Mater. Chem. A 2015, 3, 6709.[2] Kleiner et al., Top. Curr. Chem. 2017, 375, 45.[3] Kleiner et al., J. Power Sources 2016, 317, 25.[5] Robinson et al., ECS Electrochem. Lett. 2015, 4, 9.