Pre-treatment of spent batteries before pyrometallurgical recycling is a critical step to ensure safety, efficiency, and material recovery. The process varies depending on battery chemistry, size, and application, such as electric vehicle (EV) batteries versus consumer electronics batteries. Key steps include discharging, mechanical processing, sorting, and material-specific preparations to mitigate hazards like thermal runaway and contamination.

**Discharging Spent Batteries**
Before physical processing, batteries must be fully discharged to eliminate residual energy. High-voltage EV batteries require controlled discharging to prevent short circuits or thermal events. This is typically done using resistive loads or specialized discharge equipment that brings the voltage to a safe level. Consumer electronics batteries, such as lithium-ion cells in smartphones, often have lower energy capacity but still require careful discharge to avoid risks. Incomplete discharge can lead to arcing or fires during shredding.

**Mechanical Processing: Shredding and Crushing**
Once discharged, batteries undergo size reduction through shredding or crushing. EV batteries, due to their large format and robust casing, need heavy-duty shredders capable of handling metal enclosures and modules. The process typically involves coarse shredding followed by fine grinding to liberate active materials from current collectors and separators. Consumer electronics batteries are smaller and often shredded in bulk, but their varied form factors (cylindrical, prismatic, pouch) require adaptable equipment.

Shredding must occur in an inert atmosphere (e.g., nitrogen or argon) to prevent fires caused by reactive lithium or electrolyte solvents. Some facilities use cryogenic shredding to minimize thermal risks, as low temperatures reduce reactivity. The output is a mixed material stream called "black mass," containing cathode and anode materials, metals, and plastics.

**Sorting and Separation**
After shredding, materials are sorted to improve recovery efficiency. Magnetic separation removes ferrous metals like steel casings, while eddy current separators recover non-ferrous metals such as aluminum and copper. For EV batteries, the higher metal content necessitates more intensive sorting to maximize copper and aluminum recovery from busbars and foils.

Polyvinyl chloride (PVC) and other halogenated plastics must be removed before pyrometallurgical processing. Halogens, when heated, form corrosive gases (e.g., hydrogen chloride) that damage furnace linings and emission control systems. PVC is common in consumer electronics battery insulation but less prevalent in EV packs, which often use halogen-free materials. Sieving and air classification separate lightweight plastics from denser metal and active material fractions.

**Thermal Runaway Mitigation**
Thermal runaway is a major hazard during pre-treatment, especially for damaged or high-energy cells. EV batteries, with their large energy density, pose greater risks if internal short circuits occur. Safety measures include:
- Monitoring cell temperatures during discharge and shredding.
- Using fire suppression systems (e.g., inert gas or specialized extinguishing agents).
- Implementing explosion-proof equipment in processing areas.

Consumer electronics batteries, while smaller, can still ignite if improperly handled. Some facilities pre-treat cells with saltwater baths to fully discharge and passivate reactive components, though this adds complexity to downstream drying.

**Material-Specific Preparations**
Pyrometallurgy is sensitive to feedstock composition. Lithium-ion batteries require:
- Removal of electrolytes: Solvents like dimethyl carbonate (DMC) or ethylene carbonate (EC) vaporize at high temperatures, requiring gas scrubbing.
- Separation of fluorine-containing components: PVDF binders and LiPF6 salts release toxic HF gas if not controlled.
- Handling of cobalt and nickel: These metals are primary targets for recovery, but their oxides may require additives (e.g., carbon as a reducing agent) in the smelting process.

Lead-acid batteries, still common in consumer applications, need separate pre-treatment due to sulfuric acid content. Neutralization and lead paste separation are required before smelting.

**Comparison: EV vs. Consumer Electronics Batteries**
EV batteries present unique challenges due to their size, complexity, and higher metal content. Pre-treatment often includes:
- Manual or robotic disassembly to access modules and cells.
- Higher energy management during discharge.
- More extensive metal recovery due to larger copper and aluminum components.

Consumer electronics batteries are smaller but more heterogeneous. Pre-treatment focuses on:
- Bulk processing of mixed chemistries (Li-ion, NiMH, etc.).
- Higher halogenated plastic content requiring removal.
- Less manual disassembly due to standardized cell sizes.

**Conclusion**
Effective pre-treatment is essential for safe and efficient pyrometallurgical recycling. Discharging, shredding, sorting, and material-specific preparations must be tailored to battery type, with EV batteries demanding more robust handling due to their scale and energy density. Mitigating thermal runaway and removing contaminants like PVC are critical across all battery types to ensure smooth downstream processing and high-purity metal recovery. Advances in automation and sorting technologies continue to improve the efficiency of these pre-treatment steps, enabling better recycling rates for both EV and consumer electronics batteries.