Vinylene carbonate water determination via coulometric Karl Fischer titration

Vinylene carbonate (vc) is commonly used as a battery electrolyte additive in lithium-ion batteries. Its popularity is due to the positive impact it has on anode cyclability and reduction of irreversible capacity. Small amounts of moisture in Li-ion batteries can significantly decrease performance and lifetime. Therefore, moisture levels in electrolyte solutions and their additives are controlled for use in manufacturing. Until recent years, accurate moisture quantification in vinylene carbonate samples was difficult due to side reactions. With the commercial development of alcohol-free coulometric Karl Fischer reagents, accurate determination is now much more accessible to end-users.

This analysis was performed using an 852 Titrando (2.852.0060) instrument, equipped with the electrodes listed in Table 1.

A small volume of vinylene carbonate was aspirated into a gas-tight syringe to coat its interior before being disposed of. Excess vinylene carbonate was then drawn into the gas-tight syringe. The prepared syringe was then tared on a balance with four decimal places.

The titration vessel was pre-titrated during conditioning to remove any moisture present from both the immediate environment and the reagents themselves. A volume of 0.5 mL of vinylene carbonate was directly injected into the titration vessel equipped with NEXTGEN Coulomat A-FA/C-FA reagents. The mass was measured by difference. Water from the sample was finally titrated in the coulometric vessel.

During battery manufacturing, control of all moisture present is important to guarantee adequate performance in the finished product. More easily quantifying the moisture contribution from additives such as vinylene carbonate makes this a much simpler task. The introduction of alcohol-free Karl Fischer reagents accomplishes this effectively, allowing the generation of accurate and repeatable moisture data—even for a difficult sample matrix.