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Determine H2O and HF in Lithium Ion Batteries by Karl Fischer Titration

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Testing Battery Components: Electrolyte, Cathode and Anode

Test H<sub>2</sub>O and HF in Lithium Ion Battery — Karl Fischer Titration
Test H<sub>2</sub>O and HF in Lithium Ion Battery — Karl Fischer Titration

Lithium ion batteries consist of three main components: the cathode, the anode and the liquid electrolyte. In order to ensure high quality, the amount of water inside a battery must be as low as possible and each component needs to be tested for water before it is built into the battery housing.

Download the free white paper about the determination of detrimental water and hydrofluoric acid in the main lithium ion battery components.

Water – Poison for Lithium Ion Batteries

Electrolyte is usually a mixture of organic carbonates and electrolyte salt that increases lithium ion conductivity. Lithium hexafluorophosphate (LiPF6) is the state-of-the-art electrolyte salt in such electrolytes. However, the use of LiPF6 also comes with certain caveats. Traces of water in the electrolyte catalyze the formation of degradation products that can compromise the electrodes and the electrolyte itself. Among others, the electrical insulator, lithium fluoride (LiF), and hydrofluoric acid (HF) are formed. Both substances lower the electrode's efficiency over time. HF can further lead to heat being released due to degradation of the cathode, thereby risking a thermal runaway scenario. This negative influence on the battery's performance gives water its meaningful name: battery poison.

Water – The Most Important Quality Control Parameter for Battery Manufacturers

Karl Fischer titration has proven to be the method of choice. The gas-phase extraction technique with coulometric detection enables the determination of water in solid electrodes, whereas coulometric KF titration with direct injection can be used to determine the water content of the electrolyte. Along with water, hydrofluoric acid (HF) – one of the detrimental degradation products of LiPF6 – can be tested using an acid-base titration with sodium hydroxide as the titrant.


Lithium Ion Batteries