In the course of energy crisis energy revolution is taking place with important changes to renewable energy sources. In this process lithium ion batteries (LIBs) are one key technology concerning energy storage and electromobility because of their high efficiency and their environmental-acceptability. In Germany the government has made it a strategic objective to increase the number of electric cars on the streets to 1 million until 2020 and become more independent of oil as resource. [1] Nevertheless, to target this goal several shortcomings in LIBs have to be addressed. For instance, their unsatisfying energy density, which goes along with the driving range of automobiles or the inadequate long-term cyclability compared to the costs of acquisition. Furthermore, poor rate capability especially at high cycling rates still prevails in battery technology independent of system.

One simple approach to concern named problems and increase the reliability of LIBs, is to modify the cell design, namely cathode or anode in order to adapt the cell performance to its application. Pioneering is the preparation of hierarchically structured composites since they unite the positive effects of nano particles with the manageability of powders in the micrometer range. Nano-structuring itself goes along with shorter diffusion paths, improved conductivities and the suppression of structural changes during cycling [2]. Latter effect is of great interest when facing future materials with stronger volume changes during cycling like Ni-rich NCM cathode materials with their potential to provide higher energy densities. [3]

In this presentation the approach of hierarchical structuring cathode active materials by an elaborated process of grinding, spray drying and calcination and with that the preparation of hierarchically structured composite electrodes will be given for LiNi_1/3Co_1/3Mn_1/3O₂ (NCM-111), which is often integrated as active material in commercially available batteries. The relationship between process parameters, structures and performance of the as prepared LIBs will be given by detailed material characterization in combination with electrochemical investigations. Here, the focus will be on effects of primary particle and granule size on electrochemical performance and their causes. It will be shown that active material granules prepared in sizes between 9 and 42 µm with nanostructured morphology and defined porosity have superior discharge capacities and power densities compared to bulk unprocessed NCM material. A tuning of the performance at high C-rates can be reached by adaption of process parameters.

This research project is supported by the Federal Ministry of Economics and Energy (BMWi), project No. 03ET6095A.

[1] Die Bundesregierung, Nationaler Entwicklungsplan Elektromobilität der Bundesregierung, 2009.

[2] D. Chen, D. Kramer, R. Mönig, Electrochimica Acta 2018, 259, 939.

[3] L. de Biasi, A. O. Kondrakov, H. Geßwein, T. Brezesinski, P. Hartmann, J. Janek, J. Phys. Chem. C 2017, 121, 26163.