Erabhoina Harimohan, Thelakkat Mukundan
Applied Functional Polymers, University of Bayreuth, Universitätsstraße.30, 95447, Bayreuth, Germany.
Bavarian Centre for Battery Technology (BayBatt), University of Bayreuth, Universitätsstraße.30, 95447, Bayreuth, Germany.
Sci Rep. 2022 Mar 31;12(1):5454. doi: 10.1038/s41598-022-09244-3.
All solid-state rechargeable lithium metal batteries (SS-LMBs) are gaining more and more importance because of their higher safety and higher energy densities in comparison to their liquid-based counterparts. In spite of this potential, their low discharge capacities and poor rate performances limit them to be used as state-of-the-art SS-LMBs. This arise due to the low intrinsic ionic and electronic transport pathways within the solid components in the cathode during the fast charge/discharge processes. Therefore, it is necessary to have a cathode with good electron conducting channels to increase the active material utilization without blocking the movement of lithium ions. Since SS-LMBs require a different morphology and composition of the cathode, we selected LiFePO (LFP) as a prototype and, we have systematically studied the influence of the cathode composition by varying the contents of active material LFP, conductive additives (super C65 conductive carbon black and conductive graphite), ion conducting components (PEO and LiTFSI) in order to elucidate the best ion as well as electron conduction morphology in the cathode. In addition, a comparative study on different cathode slurry preparation methods was made, wherein ball milling was found to reduce the particle size and increase the homogeneity of LFP which further aids fast Li ion transport throughout the electrode. The SEM analysis of the resulting calendered electrode shows the formation of non-porous and crack-free structures with the presence of conductive graphite throughout the electrode. As a result, the optimum LFP cathode composition with solid polymer nanocomposite electrolyte (SPNE) delivered higher initial discharge capacities of 114 mAh g at 0.2C rate at 30 °C and 141 mAh g at 1C rate at 70 °C. When the current rate was increased to 2C, the electrode still delivered high discharge capacity of 82 mAh g even after 500 cycle, which indicates that the optimum cathode formulation is one of the important parameters in building high rate and long cycle performing SS-LMBs.
与基于液体的同类电池相比，所有固态可充电锂金属电池（SS-LMBs）因其更高的安全性和更高的能量密度而变得越来越重要。尽管有这种潜力，但它们的低放电容量和较差的倍率性能限制了它们作为先进的SS-LMBs使用。这是由于在快速充放电过程中，阴极固体成分内的固有离子和电子传输路径较低。因此，需要有一个具有良好电子传导通道的阴极，以提高活性材料的利用率，同时不阻碍锂离子的移动。由于SS-LMBs需要不同形态和组成的阴极，我们选择LiFePO（LFP）作为原型，并通过改变活性材料LFP、导电添加剂（超级C65导电炭黑和导电石墨）、离子传导成分（PEO和LiTFSI）的含量，系统地研究了阴极组成的影响，以阐明阴极中最佳的离子和电子传导形态。此外，还对不同的阴极浆料制备方法进行了比较研究，其中发现球磨可以减小LFP的粒径并提高其均匀性，这进一步有助于锂离子在整个电极中的快速传输。对所得压延电极的SEM分析表明，电极形成了无孔且无裂纹的结构，并且整个电极中都存在导电石墨。结果，具有固体聚合物纳米复合电解质（SPNE）的最佳LFP阴极组合物在30°C下以0.2C倍率时的初始放电容量为114 mAh g，在70°C下以1C倍率时为141 mAh g。当电流倍率增加到2C时，即使在500次循环后，电极仍具有82 mAh g的高放电容量，这表明最佳的阴极配方是构建高倍率和长循环性能的SS-LMBs的重要参数之一。
