3.1 Pre-Treatment

Pre-treatment comprises a series of crucial steps performed right after the cell is assembled and filled with electrolyte, but before the main electrochemical formation cycles start. The main goal is to create the best possible, even conditions inside the cell. This ensures that the critical protective layers—the Solid Electrolyte Interphase (SEI) on the anode and the Cathode Electrolyte Interphase (CEI)—form with high quality and consistency during the subsequent formation process.

The most vital part of pre-treatment is making sure the electrolyte completely and evenly soaks into the entire porous structure of the anode, cathode, and separator (a process called wetting). If wetting is incomplete or uneven, it can cause serious problems. These include uneven current distribution, lithium plating in localized areas, inconsistent SEI properties, and ultimately, poor cell performance, a shorter lifespan, and reduced safety.

The specific pre-treatment methods and how long they take depend heavily on the cell design—format, size, and electrode thickness, the materials used, and the desired level of quality. Generally, pre-treatment strategies can involve thermal or mechanical methods, and sometimes initial electrical pulses or conditioning.