Understanding the Effects of the Mixing Processes on the Performance of NMC-LMO Blend Electrodes Made By a Dry Electrostatic Spray Deposition Process

Abstract

Improving the manufacturing process of making lithium-ion batteries (LIBs) is a key to further decreasing the cost and expanding the market of LIBs for many applications, especially for electric vehicles. Since electric vehicles require durable, sustainable, and cost-effective battery systems for their continued enlargement, advanced manufacturing processes of LIBs need to be investigated. The conventional wet slurry operation for LIB electrode manufacturing imposes several limitations on cost and performance mostly due to solvent usage. The drying process for the evaporation and recovery of organic solvent requires the use of unwanted solvents that do not contribute to the final product, thus consuming energy. If solvent evaporation is not controlled well, issues such as binder migration, segregation, and cracking of the electrode can occur, affecting the performance of the battery. Therefore, using a solventless dry process for electrode manufacturing has the potential to reduce the cost and environmental impact by eliminating solvent usage.In this work, electrostatic spray deposition (ESD) without the use of a solvent is investigated for manufacturing thick NMC811/LMO electrodes. Comparing two different dry powder mixing methods, we showed that dry powder mixing prior to ESD has a significant effect on the electrode microstructure and, consequently, its performance. Electrodes made by ball mill mixing retained better discharge capacity, which was attributed to the low charge transfer resistance and improved ionic conductivity due to porous conductive pathways formed between and on the active material particles. High speed mixing, on the other hand, caused dense layers of binder and conductive agent agglomerates, limiting the contact area of the electrolyte with active materials and increasing the resistance.