Impact of carbon black distribution on dry coating and PTFE-fibrillation in cathodes for lithium-ion batteries

Solvent-free technologies have gained significant attention as promising alternatives for producing lithium-ion battery electrodes. Dry electrode manufacturing by roll-to-roll calendering based on a polytetrafluoroethylene binder has reached high technological maturity, offering the potential to lower manufacturing costs and enable sustainable production. Here, the influence of carbon black distribution on the properties of the composite granules, the calendering step for dry-coated cathodes, as well as the interplay between carbon black and polytetrafluoroethylene is investigated. Various carbon black distribution patterns are obtained by varying the mixing time of the active material and carbon black during premixing. The results reveal that carbon black distribution has a critical impact on the processibility of the composite. Homogenous mixtures with uniformly distributed carbon black exhibit improved compressibility and higher degrees of polytetrafluoroethylene fibrillation in the electrodes after calendering. Both, the electronic and ionic conductivity, as well as the electrochemical performance of the electrodes, indicate that different distributions of carbon black still result in comparable characteristics of the electrodes, only if a sufficient percolation network is established. The findings contribute to the understanding of the basic interaction between carbon black and polytetrafluoroethylene in dry-coated cathodes and facilitate the design of electrode formulations tailored to specific process requirements.