Operando monitoring of the open circuit voltage during electrolyte filling ensures high performance of lithium-ion batteries

The wetting process plays an important role in battery production efficiency and battery quality, including available energy density, cycling life, power, and battery consistency. A convenient and efficient method for characterizing electrolyte filling, which becomes more crucial for lithium-ion batteries (LIBs) with a large format or super energy density, is desperately needed in the battery industry. Herein, we propose the operando monitoring of the open circuit voltage (OCV) during the electrolyte filling process. It is found that battery OCV drops dramatically to − 0.80 V at the beginning of filling (within 300 ms), and then characteristically recovers to 0.10 V with the wetting process, involving valuable information about the electrolyte filling process. Insights of the correlation between electrolyte wetting process and battery OCV are further stimulated using an equivalent circuit model. The recovery rate of OCV can be a critical indicator to quantify the electrolyte wetting process, verifying by batteries used separators with different wettability. This study provides a practical and effective tool to ensure the high-quality electrolyte infiltration process of LIBs.