85–105 MPa Tensile Strength Lithium Battery Soft Pack Foil 8021 – Reliable Strength for High‑Performance Pouch Cells | Mingtai Aluminum
Introduction: The Strength Requirement for Soft Pack Battery Foil
Lithium‑ion soft pack (pouch) batteries demand a delicate balance of material properties. The aluminum foil used as the barrier layer in the laminated outer casing must be flexible enough to withstand deep drawing and folding, yet strong enough to resist puncture, tear propagation, and mechanical stress during battery assembly and cycling. While high elongation is essential for formability, tensile strength is equally critical – it determines the foil‘s ability to withstand the stresses of lamination, pouch formation, and long‑term service without failure.
8021 soft pack battery foil with a tensile strength range of 85–105 MPa offers the optimal balance: sufficient strength to maintain barrier integrity, yet not so high that it sacrifices the ductility required for deep drawing. This specification has become the industry benchmark for high‑performance lithium‑ion pouch cells used in electric vehicles, consumer electronics, and energy storage systems.
Mingtai Aluminum (Stock Code: 601677), with nearly 30 years of experience and an annual production capacity exceeding 1.6 million tonnes, supplies premium 8021 lithium battery soft pack foil precisely controlled to deliver 85–105 MPa tensile strength. Our foil is engineered to meet the rigorous demands of battery manufacturers worldwide.
Why Tensile Strength Matters for Soft Pack Battery Foil
Tensile strength is the maximum stress a material can withstand while being stretched or pulled before breaking. For soft pack battery foil, this property influences several critical aspects:
1. Resistance to Tearing During Pouch Formation
During the deep drawing and folding processes that shape the laminated film into a pouch, the foil experiences significant tensile stresses. If the tensile strength is too low, the foil may tear prematurely. The 85–105 MPa range provides adequate resistance to tearing while still allowing the high elongation (15–26%) needed for forming.
2. Mechanical Integrity During Battery Assembly
Pouch cells are stacked, compressed, and sealed. The foil must withstand the forces applied during these operations without developing pinholes or micro‑cracks. Higher tensile strength (within the optimal range) ensures robust handling.
3. Long‑Term Cyclic Durability
During battery charge/discharge cycles, the electrodes expand and contract slightly, subjecting the pouch foil to repeated mechanical stress. A foil with consistent tensile strength within the 85–105 MPa range resists fatigue failure over thousands of cycles.
4. Resistance to Puncture from Electrode Edges
Sharp edges of the anode and cathode can press against the inner surface of the pouch. Higher tensile strength helps resist puncture, preventing electrolyte leakage and short circuits.
Why 8021 Alloy for Soft Pack Battery Foil?
8021 aluminum alloy (Al‑Fe‑Si system) is specifically formulated for flexible packaging and battery applications. Its composition – iron 1.2–1.7%, silicon ≤0.15% – provides a unique combination of high elongation and moderate tensile strength. Compared to pure aluminum (1235), 8021 offers:
Higher tensile strength (85–105 MPa vs. 60–80 MPa for 1235 O temper)
Better pinhole resistance due to tighter grain structure
Excellent deep drawability with elongation of 15–26%
Compared to 8079 or 8011 alloys, 8021 delivers a more balanced performance for soft pack battery casings, making it the preferred choice for leading battery manufacturers.
Mechanical Properties of Mingtai‘s 8021 Soft Pack Foil
| Property |
Specification | Benefit |
| Tensile strength | 85 – 105 MPa | Optimal strength for pouch formation and long‑term durability |
| Elongation | 15% – 26% (depending on thickness) | Excellent deep drawability, crack‑free forming |
| Yield strength | 45 – 65 MPa (typical) | Low enough for forming, high enough for structural integrity |
| Pinhole density | ≤5 per m² | Absolute barrier integrity |
| Thickness range | 0.025 – 0.045 mm (25–45 microns) | Standard for battery laminates |
| Thickness tolerance | ±0.002 mm | Consistent lamination and sealing |
Tensile strength by thickness (typical values):
| Thickness (mm) |
Tensile Strength (MPa) | Elongation (%) |
| 0.025 | 85 – 95 | 15 – 18 |
| 0.030 | 88 – 98 | 18 – 22 |
| 0.035 | 90 – 100 | 20 – 24 |
| 0.040 | 92 – 105 | 22 – 26 |
The tensile strength increases slightly with thickness due to the rolling process; thinner foils are at the lower end of the range, thicker foils at the higher end.
How Tensile Strength Affects Pouch Manufacturing
Understanding the relationship between tensile strength and processability helps battery manufacturers select the right foil specification:
●Forming (Deep Drawing) : Lower tensile strength (closer to 85 MPa) allows easier stretching and deeper draws, reducing the risk of cracking. This is advantageous for complex pouch shapes.
●Handling & Assembly: Higher tensile strength (closer to 105 MPa) provides greater resistance to tearing from sharp edges or mechanical handling, improving production yield.
●Final Pouch Strength: The finished pouch‘s resistance to burst pressure correlates with the foil‘s tensile strength. A 105 MPa foil offers greater burst resistance than an 85 MPa foil.
Mingtai‘s 8021 foil is supplied with tight control over tensile strength, ensuring that each batch falls within the specified 85–105 MPa range. Customers can request material with tensile strength targeted to a narrower sub‑range (e.g., 90–95 MPa) for specific processes.
Additional Critical Properties for Battery Foil
Excellent Pinhole Resistance
Pinholes are the enemy of battery safety. Mingtai‘s 8021 foil achieves pinhole density ≤5 per m² through precision rolling and strict quality control. 100% online pinhole detection ensures that any foil with defects is rejected.
Surface Cleanliness
Residual oil must be minimized to ensure strong adhesion between the aluminum foil and the laminating adhesive (which bonds the foil to PP and nylon layers). Mingtai‘s degreasing process achieves residual oil ≤2 mg/m² (A‑level per DIN EN 14287).
Wetting Tension
A wetting tension of ≥72 dyn/cm guarantees that the foil surface is receptive to adhesives and coatings, ensuring reliable lamination.
Corrosion Resistance
The 8021 alloy‘s dense oxide layer provides excellent resistance to electrolyte corrosion. Accelerated tests confirm no significant degradation after extended exposure to LiPF₆‑based electrolytes.
Quality Assurance for Battery Applications
Mingtai‘s 8021 soft pack foil is manufactured under strict quality management systems:
IATF 16949 certified – Automotive grade quality management, essential for battery supply chains.
100% online tensile testing – Continuous monitoring ensures every coil meets the 85–105 MPa specification.
Pinhole detection – Laser or optical scanners reject any foil with pinholes above limit.
Cleanroom packaging – Foil is packed in a controlled environment to prevent contamination.
Why Choose Mingtai for 8021 Battery Foil?
Nearly 30 years of aluminum processing experience – Publicly traded company with dedicated battery foil production lines.
Precise tensile strength control – 85–105 MPa range, fully customizable within this window.
High elongation (15–26%) – Excellent formability for deep‑drawn pouch designs.
Ultra‑low pinhole density – ≤5 per m², protecting battery safety.
Clean, anodizing‑ready surface – Residual oil ≤2 mg/m², wetting tension ≥72 dyn/cm.
Tight thickness tolerance – ±0.002 mm for consistent lamination.
Full compliance – IATF 16949, ISO 9001, ISO 14001, RoHS, REACH.
Flexible ordering – MOQ 3 tonnes; free samples for validation.
Fast delivery – 7–45 days to over 150 countries.
Conclusion
For lithium‑ion soft pack battery manufacturers seeking a reliable, high‑performance barrier foil, 8021 aluminum foil with 85–105 MPa tensile strength from Mingtai Aluminum delivers the optimal balance of strength, formability, and barrier integrity. Our precision‑engineered foil ensures that your pouch cells are protected against mechanical stress, electrolyte corrosion, and pinhole defects – contributing to safer, longer‑lasting batteries.
Contact Mingtai Aluminum today for free samples, technical data sheets, or a factory‑direct quotation.
FAQ – 85–105 MPa Tensile Strength 8021 Soft Pack Battery Foil
Q1: What is the typical thickness of 8021 foil for soft pack batteries?
A: Most applications use 0.025–0.045 mm (25–45 microns) . Thinner foils reduce weight and cost; thicker foils offer higher strength and pinhole resistance.
Q2: Why is the tensile strength range 85–105 MPa optimal for pouch foil?
A: Below 85 MPa, the foil may be too weak to resist tearing during assembly or burst pressure in service. Above 105 MPa, elongation typically decreases, making deep drawing more difficult. The 85–105 MPa range balances strength and formability.
Q3: Does higher tensile strength mean better battery safety?
A: Not necessarily. Excessively high tensile strength often comes with reduced elongation, increasing the risk of cracking during pouch formation. The optimal balance is moderate strength (85–105 MPa) combined with high elongation (15–26%).
Q4: Can Mingtai supply 8021 foil with tensile strength targeted to a narrower range (e.g., 90–95 MPa)?
A: Yes. We can adjust rolling and annealing parameters to achieve a narrower tensile strength window. Please specify your requirement when ordering.
Q5: What is the minimum order quantity for a trial coil?
A: For standard thicknesses (0.03–0.04 mm), trial coils of 500–1,000 kg are available. Full production MOQ is 3 tonnes.
Q6: How is the foil tested for pinholes?
A: We use online pinhole detection systems (laser or optical scanners) that inspect 100% of the foil surface at production speed. Any pinhole exceeding the size or density limit triggers automatic rejection.
Q7: Does the foil require any surface treatment before lamination?
A: Mingtai‘s foil is supplied with a clean, degreased surface (residual oil ≤2 mg/m²). It is ready for adhesive lamination with PP and nylon layers without additional treatment.
Q8: What certifications does Mingtai hold for battery materials?
A: IATF 16949 (automotive quality), ISO 9001, ISO 14001. Our products comply with RoHS and REACH.
Contact Mingtai for your 8021 battery foil requirements.
Mingtai Aluminum – Battery Materials Division
Phone: +86‑18776078273
Email: sales@mingtai-al.com
Website: www.mingtaialuminum.com
Factory Address: Gongyi City Industrial Agglomeration Area, Henan, China
