What is 1235 H18 aluminum foil, and why is it suitable for lithium batteries?
1235 H18 refers to a specific alloy (AA1235) with 99.35% aluminum purity, cold-rolled to an H18 temper (hardened state). This foil is ideal for lithium batteries due to its high electrical conductivity, corrosion resistance, and mechanical strength. The H18 temper provides rigidity for electrode coating processes while maintaining flexibility for winding. Its ultra-thin thickness (typically 10–20 μm) minimizes weight and maximizes energy density. Additionally, the alloy's low iron content (<0.65%) reduces electrochemical side reactions.
2. How does the H18 temper affect the performance of 1235 aluminum foil in batteries?
The H18 temper enhances tensile strength (up to 180 MPa), preventing foil breakage during high-speed electrode manufacturing. However, it slightly reduces elongation compared to softer tempers (e.g., O or H14), requiring precise handling. This hardness ensures dimensional stability during slurry coating and drying. It also improves puncture resistance, critical for avoiding short circuits. Manufacturers balance H18's rigidity with post-annealing treatments to optimize formability.
3. What are the key differences between 1235 H18 and other aluminum foils (e.g., 1060 or 8079) for batteries?
1235 H18 offers higher purity (99.35% Al) than 1060 (99.6%) but lower than 8079 (99.8%), striking a balance between cost and performance. Its iron-silicon ratio minimizes intermetallic particles that harm conductivity. Unlike 8079 (often used for packaging), 1235 H18 is optimized for adhesion with cathode materials like LiFePO₄. Thickness consistency is stricter for 1235 H18 to meet battery-grade standards. Surface treatments (e.g., hydrophilic coatings) are also tailored for 1235's microstructure.
4. What surface properties must 1235 H18 foil have to ensure good electrode adhesion?
The surface must be clean, oxide-free, and slightly roughened (Ra ~0.2–0.5 μm) to promote slurry bonding. Pinhole defects must be <5 per m² to prevent electrolyte leakage. A uniform oxide layer (2–5 nm) forms naturally, but excessive oxidation weakens conductivity. Some manufacturers apply nano-carbon coatings to reduce interface resistance. Electrochemical tests (e.g., peel strength ≥1.0 N/cm) validate adhesion quality.
5. How is 1235 H18 aluminum foil recycled in the battery supply chain?
Post-production scraps and end-of-life foils are melted and refined to remove impurities (e.g., electrode residues). Advanced sorting technologies separate aluminum from other battery components (e.g., copper or plastics). Recycled 1235 alloy retains ~95% of its original conductivity after purification. Closed-loop recycling reduces energy consumption by 90% vs. primary production. Battery makers increasingly demand recycled-content foils to meet sustainability goals.
