Mill Scale - Secondary Resource for Lithium Iron Phosphate Batteries

Mill scale, a by-product of the steel manufacturing process, is primarily composed of iron oxides (FeO, Fe₂O₃, and Fe₃O₄) and is increasingly recognized as a valuable resource for iron recovery. Recent research and industrial interest have focused on utilizing iron recovered from mill scale for advanced applications, such as producing materials for lithium-ion batteries (LIBs).

The growing demand for sustainable and cost-effective battery components has driven interest in secondary sources like mill scale. Lithium iron phosphate (LiFePO₄), commonly abbreviated as LFP, is a widely used cathode material in lithium-ion batteries due to its excellent thermal stability, long cycle life, and relatively low cost. Recovered iron from mill scale has potential for synthesizing LiFePO₄, which is essential for batteries used in electric vehicles (EVs), energy storage systems (ESS), and other applications.

Various processes can be employed to recover iron from mill scale, using either pyrometallurgical or hydrometallurgical methods. Pre-treatment of mill scale is necessary to remove impurities such as oil, grease, or carbon, which can interfere with subsequent processing. This pre-treatment may involve drying, grinding, or roasting. The main objective is to convert the iron oxides (FeO, Fe₂O₃, Fe₃O₄) into metallic iron or iron-containing compounds suitable for LIB applications.

Several reduction methods can be used to recover iron from mill scale:

Direct Reduction: Mill scale can be reduced to metallic iron by using a reducing agent such as hydrogen or carbon monoxide. This process typically occurs in a furnace at high temperatures (700–1000°C).

Chemical Reduction: In some processes, mill scale is treated with chemical reducing agents in solution to produce iron-based compounds, such as iron salts, which can then be further processed.

Once the mill scale is converted into metallic iron or iron oxides, it can be used in the synthesis of battery cathode materials. The recovered iron, in combination with lithium and phosphate, can be processed through calcination and other chemical methods to produce active cathode material.

Advantages of Using Mill Scale for Lithium-Ion Batteries:

Cost Efficiency: Recovering iron from mill scale provides a low-cost source of raw materials for battery production compared to virgin iron ores or complex mining operations.

Sustainability: Recycling mill scale supports a circular economy by reducing waste and minimizing the environmental impact of iron ore mining and extraction.

Reduced Carbon Footprint: Repurposing mill scale for LIB applications reduces the carbon footprint associated with the extraction and processing of virgin materials, making it an eco-friendly solution for battery production.

Large Supply: Mill scale is abundantly produced during steel manufacturing and often treated as waste. Utilizing it in LIBs can significantly reduce waste while providing a reliable material source.

Recovering iron from mill scale for use in lithium-ion batteries presents a promising opportunity for resource recycling and sustainable battery production.

Hydromet specializes in innovative solutions for resource recovery and can assist in the advancement of processes to convert mill scale into valuable materials for lithium-ion batteries.