Tailoring Carbon Black Distribution in LFP Based Electrodes via High-Intensity Drymixing

Raffenberg, Simon; Junghans, Katrin; Winter, Martin; Börner, Markus

Abstract

Conductive electrode additives, such as graphite or carbon black (CB), are imperative inactive materials for lithium ion battery electrodes that contain active materials with limited electronic conductivity such as LiFePO4 (LFP). However, the distribution of these additives and their impact on the electrodes conductive carbon binder domain (CBD) are not yet fully understood. In order to address this issue, the present study investigates the influence of a pre drymixing step of LFP and CB on the electrochemical performance of LFP-based electrodes. Electrochemical characterization of the electrodes based on the LFP/CB drymix revealed lower electronic through-plane conductivity and an inferior performance at higher discharge rates compared to conventionally processed electrodes. This phenomenon was attributed to the difference in the percolation network and their alteration in long- and short-range electronic contacts within the CBD of the composite electrode. In order to address these alterations, a combination of premixed LFP/CB with additional undispersed “free carbon” was introduced, yielding improved electrochemical performance. These findings highlight the necessity of tailoring the CBD in LFP-based electrodes and demonstrate a scalable upstream unit operation to optimize electronic contacts throughout the entire composite electrode. This approach can be adapted to other battery materials with inherently low electronic conductivity.