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Water Content of Lithium-Ion Battery Electrolyte without Additives

A Method Using Coulometric KF Titration with Direct Injection

The application describes a method to measure the water content of lithium battery electrolyte via coulometric KF titration with direct injection.

Background

Lithium-ion batteries are commonly used for portable electronic devices and electric vehicles (EVs). The electrolyte used in these batteries is usually a mixture of organic carbonates and the electrolyte salt that increases the lithium-ion conductivity. Lithium hexafluorophosphate (LiPF6) is the state-of-the-art electrolyte salt in such electrolytes. It dissolves well in organic carbonates, is electrochemically stable and helps to conduct lithium cations. However, the use of LiPF6 also brings up a problem: it is not stable against hydrolysis. Traces of water in the electrolyte lead to the formation of hydrofluoric acid (HF), which is considered battery poison destroying the electrodes and lowering the capacity. Therefore, the amount of water in the lithium-ion battery electrolyte should be as low as possible.

This can be achieved with automated Karl Fischer Titrators.

This application note includes:

  • An introduction to the method
  • Sample preparation and procedures
  • Solutions and chemicals
  • Chemistry
  • Instruments and accessories
  • Results and remarks

And method files (.lmt and .xml) for direct import and implementation on the instrument.
 

Lithium Ion Batteries