Meaning
Thresholds for the concentration of alkaline contaminants in lithium salts or precursor materials define the acceptable purity for battery manufacturing. Maintaining strict sodium impurity limits is necessary because sodium ions can interfere with the intercalation process of lithium. These contaminants often originate from the brine extraction process or the reagents used in chemical synthesis.
High levels of foreign ions disrupt the crystalline lattice and reduce the ionic conductivity of the electrode.
Electrochemical Interference
Foreign ions with different radii than lithium create local distortions in the host material. When sodium impurity limits are exceeded, the cell may exhibit erratic voltage behavior or accelerated capacity loss. These atoms do not participate effectively in the charge storage mechanism.
Resistance increases as the lattice becomes congested.
Procurement Quality
Purchase agreements for lithium carbonate or hydroxide specify these maximum values to ensure consistent performance across batches. If a supplier fails to meet the sodium impurity limits, the material is often rejected or diverted to lower grade industrial uses. Prices for high purity grades mirror the additional processing required.
Standard specifications usually target levels below fifty parts per million.
Detection Method
Inductively coupled plasma mass spectrometry identifies trace metals with high precision.
