Who sets the specification
There is no single global standard for battery-grade lithium carbonate, lithium hydroxide, nickel sulphate or cobalt sulphate. Specifications are largely set by the customers who use them: cathode active material producers and the cell manufacturers behind them. Each has its own limits based on their synthesis process and the performance their cells need.
In practice, specifications cluster around similar values, and some national and industry standards exist. But a refinery selling into several customers often has to meet the tightest limit across its contracts. That is why qualification of a new supplier takes time and involves both assay work and trial cathode production.
Which impurities matter
Limits are usually expressed in parts per million for named elements. Sodium, calcium, magnesium, iron, copper, zinc and sulphate are common entries, alongside moisture and particle size requirements. The impurities that matter most depend on the product. Copper and iron, for example, can cause internal short circuits if they reach the cell, so their limits tend to be very low.
For recycled material, the risk profile is different from mined material. Fluoride, aluminium and copper from battery components are more likely to be present, while some mining-related impurities may be less of a concern. Refineries design their impurity removal steps around these battery-specific contaminants.
- Metallic impurities that can cause short circuits, such as copper and iron
- Alkali and alkaline earth metals such as sodium, calcium and magnesium
- Anions such as sulphate, chloride and fluoride
- Moisture and physical properties such as particle size
Proving compliance batch by batch
Every shipment should carry a certificate of analysis stating results for each specified element and the method used, typically ICP-OES or ICP-MS for metals and ion chromatography for anions. Buyers commonly retain samples and may run their own checks, with an agreed umpire laboratory for disputes.
Consistency matters as much as meeting the limit once. A cathode producer would rather have a supplier that meets specification every time than one whose results swing between very pure and borderline. Recycled feed varies by chemistry and source, so refineries rely on blending, process control and tight feed assay to keep output stable.