(280c) Dry Process for Battery Electrodes: The Role of Powders Mixture Properties and Mixing Conditions on Flowability and Electrode Performance Using Design of Experiments

In a rapidly evolving global landscape, lithium-ion batteries (LIB) are increasingly utilized in transportation, energy storage, and electronics underscoring the imperative to enhance battery characteristics. While the near-future LIB production capacity is expected to continue its growth during the next years(1), numerous challenges still need to be faced, for instance, manufacturing requires a better supply chain, including sustainable sourcing of minerals and the use of recycled cells materials. Moreover, the current manufacturing process suffers from several limitations such as high energy consumption and limited speed, both induced by the drying step, which consists in solvent evaporation during heating. LIB dry processes not only avoid the use of toxic solvents, but also aims for breakthroughs in lithium-ion and post lithium-ion technologies contributing to a more environmentally friendly approach, reducing energy consumption and costs while offering a dual environmental advantage. However, the dry process needs the development of specific unit operations such as powder formulation, mixing, electrospray deposition and calendering. Among them, electrospray deposition stands out as one promising technique for dry electrode manufacturing, and it is strongly dependent on the formulation and mixing parameters.

Ensuring large-scale viability necessitates optimizing the dry process from the standpoint of each unit operation. This is crucial for crafting high-performance electrodes, guaranteeing enhanced cyclability and greater capacity during high-rate discharge. The statistical design of Experiments (DoE) is a powerful tool for optimizing processes. This study investigates the impact of formulation and mixing operations on the flowability of the powder mixture and the electrochemical performance of the electrode. The evaluation criteria, DoE responses, include the surface coverage of active particles with the “polymeric binder”, minimal fluidization speed, and electrode porosity, all of which seem crucial for achieving high-performance electrodes following electrospray deposition. The DoE factors examined include mixing parameters such as time, rotation speed, and mixing order, along with the investigation of the formulation (active material/PVDF/conductive additives ratios). This methodology serves as an initial approach to analyze which factors are the most influent and to evaluate their impact for the next steps of the process.

[1] « The Battery Report 2023. », Volta Foundation, Jan. 2024. https://www.volta.foundation/annual-battery-report. Accessed 08 Apr. 2024.