Tailoring Electrolytes For High-Power High-Load Li-Ion Extruded Electrode Batteries

Christian Hans Krause a*, Bastian Billmann a, Naoki Matsuoka a
Martin Pulst b, Michael Deutmeyer b

a: Asahi Kasei Europe GmbH, Fringsstraße 17, 40221 Düsseldorf, Germany
b: EAS Batteries GmbH, Montaniastraße 17, 99734 Nordhausen
*corresponding author christian.krause@asahi-kasei.eu

For lithium-ion battery (LIB) technology to be widely used as energy storage for electromobility applications, such as land vehicles, shipping and air transport, the energy density, fast charging capability and manufacturing costs of the cells must be further optimized.[1] The bottleneck of current LIB technology is the accessible battery energy density and power, since there is a limit of how much active material and thus capacity can an electrode be prepared with and at the same time be accessible during charge and discharge in a wide temperature range (-20 °C to 60 °C). Conventional carbonate-based electrolytes do not allow for sufficient lithiation/delithiation of high-load electrodes and thus, the power performance is limited. This is exactly what the BMBF-funded HEADLINE (High-power high-load Li-Ion Cell-development for extruded electrodes) project is targeting at, in which a new concept of an energy-dense, fast-charging Li-ion cell with innovative, environmentally friendly manufacturing processes for high-capacity electrodes was developed and validated with a demonstration cell. The innovation of the concept lies in the fact that both durability and charge/discharge-rate capability are significantly improved by using a highly conductive electrolyte in combination with high-load electrodes, manufactured by using a novel extrusion process, in which Ethylene carbonate (EC) is used instead of N-Methyl-2-pyrrolidon (NMP) as a solvent.
The primary goal was to improve the service life and cycling stability as well as power performance of LIB cylindrical cells. To achieve this goal, Acetonitrile (AcN) was used as electrolyte co-solvent. AcN is a promising aprotic organic solvent for LIB electrolytes due to its high relative dielectric constant and low viscosity.[2,3,4] Moderately concentrated AcN-containing electrolytes exhibit high ionic conductivity and provide LIBs with outstanding power performances.[2] By the right choice of additives and conducting salt and their amounts, Asahi Kasei succeeded to overcome AcN-solvent’s drawbacks. To achieve high-temperature cycling stability and storage capability of the cell, electrolyte additives were chosen to suppress lithium salt degradation and HF generation.
22 Ah and 50 Ah LFP||Graphite cylindrical cell cycling and C-rate constant current cycling experiments as well as battery storage tests show that Asahi Kasei’s electrolyte formulation was able to outperform conventional carbonate electrolytes and enabling high-load extruded electrodes for high-power batteries.

[1] A. Yoshino, Bull. Chem. Soc. Jpn. 2022, 95, 195–197
[2] N. Matsuoka, H. Kamine, Y. Natsume, A. Yoshino, ChemElectroChem, 2021,8, 3095–3104.
[3] C. H. Krause, P. Röring, H. Onishi, D. Diddens, J. H. Thienenkamp, G. Brunklaus, M. Winter, and I. Cekic-Laskovic, J. Chem. Phys. 2020, 152, 174701
[4] C. H. Krause, P. Röring, S. Röser, D. Diddens, J. H. Thienenkamp, I. Cekic-Laskovic, G. Brunklaus, and M. Winter, J. Power Sourc. 2020, 478, 229047