Continuous vs. batch-type processing of negative electrode pastes for lithium ion batteries

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In order to produce lithium-ion batteries efficiently and to meet the growing demands on the production process, a reduction of the corresponding processing costs, process time, material and energy consump-tion are of central importance. In this context, the mixing process is particularly relevant, as its quality significantly determines the properties of the generated electrode paste and thus the quality of the subsequent process steps of coating, drying, and finally the electrochemical performance, including the longevity and fast-charging capability of the generated electrodes and batteries [1,2]. During the mixing process, active material(s), binder(s) and conductive additive(s) are supposed to be efficiently deag-glomerated, homogenized and dispersed. Therein, both particle agglomerates due to insufficient deag-glomeration and particle fractures due to excessive energy input must be prevented by tailoring the process parameters and equipment setup.
The state of the art process for electrode paste production is a batch-based process, which offers the necessary flexibility especially required in the field of academic research and development where novel materials and components are commonly only available in limited scales and various formula-tions are investigated. In contrast, innovative continuous mixing processes represent a promising alter-native when it comes to upscaling and production on industrial scale with established materials since it allows the continuous production of electrode pastes with consistently high quality [3].
Therefore, in this study a conventional batch-based mixing process is compared to an innovative contin-uous process using a twin-screw extruder for aqueous graphite-based anode formulations. Process pa-rameter variations are carried out in the continuous and discontinuous process to compare relevant processes and processing steps, respectively, as well as material and electrode characteristics such as: process time, energy input, properties of the produced pastes (rheology, particle size distribution, etc.) and electrodes with regard to morphological, mechanical, electronic and electrochemical properties. Based on the comprehensive characterization, it can be deduced that The properties of an electrode paste produced in a batch process can be represented in an extrusion process by specifically adapting the kneading concentration. For electrode pastes with comparable properties, the underlying mixing process does not significantly influence properties of the electrodes nor their electrochemical perfor-mance, thus the mixing process may be exchanged within a production line without affecting cell quali-ty.

Literature

[1] Haarmann, Matthias, Wolfgang Haselrieder, and Arno Kwade. „Extrusion‐Based Processing of Cath-odes: Influence of Solid Content on Suspension and Electrode Properties.“ Energy Technology 8.2 (2020): 1801169.

[2] Bockholt, Henrike, et al. „The interaction of consecutive process steps in the manufacturing of lithium-ion battery electrodes with regard to structural and electrochemical properties.“ Journal of Power Sources 325 (2016): 140-151.

[3] Haarmann, Matthias, Desiree Grießl, and Arno Kwade. „Continuous Processing of Cathode Slurry by Extrusion for Lithium‐Ion Batteries.“ Energy Technology (2021): 21002

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