Battery Grade and Carbon Coated Aluminum Foil: Technical Guide
Battery aluminum foil is the cathode current collector in a lithium-ion cell — the metal substrate that the cathode active material is coated onto, and that carries current out of the electrode. It has no electrochemical role. It does not store energy. And precisely because it is “inert”, it is easy to under-specify.
That is a mistake. Current collector foil affects interfacial resistance, aderența acoperirii, rate capability, cycle life, and the scrap rate on a coating line that may be running at tens of metres per minute. Getting it wrong is expensive in a way that is hard to trace back to the foil.
This guide covers alloy selection, ecartament, temperament, the case for carbon coating, and the parameters worth putting into a specification.
Why aluminum for the cathode and copper for the anode
A useful starting point, because it explains most of the design logic:
| Colector de curent catodic | Anode current collector | |
| Material | Folie de aluminiu | Copper foil |
| De ce | Aluminum forms a stable, passivating oxide layer at cathode potentials, and is light and cheap | Copper is stable at low (anode) potentials but would alloy with lithium |
| Densitate | 2.7 g/cm³ | 8.96 g/cm³ |
Aluminum is used on the cathode because copper would oxidise at cathode voltages, and aluminum because copper would be prohibitively heavy. If you are sourcing for a sodium-ion cell, note that ambele electrodes can use aluminum foil — sodium does not alloy with aluminum the way lithium does. This is one reason sodium-ion is attractive on cost, and it is a growing source of battery foil demand.
Base alloy selection
Battery foil uses the 1xxx series — commercially pure aluminum — because conductivity and purity matter more than strength.
| Aliaj | Typical use | Note |
| 1235 | Most common battery foil alloy | ≥99,35% Al. Good balance of conductivity and cost |
| 1060 | Folosit pe scară largă, slightly higher purity | ≥99.60% Al |
| 1070 | Higher purity requirements | ≥99.70% Al |
| 1050 | Used in some battery and electronic foil | ≥99.50% Al |
| 1100 | Selected where slightly higher strength is needed | Contains minor Cu |
Measured purity on production material typically runs above the specification minimum — a ≥99.0% specification commonly measures ≥99.5% in practice.
Practical advice: don’t over-specify purity unless your electrode chemistry needs it. Every purity step costs money, şi 1235 handles the majority of commercial cathode formulations.
Ecartament: the roadmap, and the pressure to go thinner
Thinner foil means less inactive mass in the cell, which means higher energy density. The entire industry is pushing down.
| Grosime | Position |
| 20 μm | Older standard, still used where handling strength matters |
| 18 μm | Conservative, good process stability |
| 16 μm | Common in volume production |
| 15 μm | Common for higher energy density |
| 13 μm | Current mainstream for high-energy cells |
| 12 μm | High-energy-density cells, demanding process control |
| 10 μm și mai jos | Frontier, limited supply |
For high-energy-density cells, 12–15 μm is the usual selection. For applications where coating-line stability and handling strength matter more than the last few percent of energy density, 18–20 μm gives better process margin and lower scrap.
The trade-off is real: as foil gets thinner it wrinkles and stretches more easily at high speed, cracks more readily at bends, and demands tighter gauge control from the mill. If your coating line is not well-tuned, dropping from 16 μm la 13 μm can cost you more in scrap than it gains in energy density.
Temper and mechanical properties
Battery foil has to balance two failure modes. Too soft and it wrinkles or stretches during high-speed coating and winding. Too hard and it cracks at bends and is difficult to wind.
| Temperament | Typical tensile strength | Typical elongation | Typical use |
| O (anexat) | 60–100 MPa | 3–15% | Applications needing ductility and forming stability |
| H18 (plin greu) | 120-170 MPa | 1–4% | High-strength foil for controlled process lines |
| H19 | 140–190 MPa | 1–3% | Higher stiffness requirements |
Most battery foil is supplied in H18. Actual values depend on alloy, ecartament, rolling reduction and annealing conditions — agree the mechanical property range contractually and require it reported on the material test certificate for each production lot.
Typical reference values for coated product: tensile strength ≥180 MPa, elongaţie >1.5%.
Plain foil vs carbon-coated foil
This is the most important decision in this guide, so it is worth being precise.
The problem carbon coating solves
When cathode slurry is coated directly onto bare aluminum foil, three things work against you:
- Contact resistance. The active material touches the metal only at discrete points. Interfacial contact resistance is high, which hurts rate capability and generates ohmic heating.
- Adeziune. Slurry adhesion to smooth metal is weaker than to a rough, high-surface-area carbon layer. Poor adhesion means delamination during calendaring and cycling.
- Coroziune. The aluminum surface can corrode in contact with electrolyte over long cycling, particularly at higher voltages and with certain chemistries.
What the carbon layer does
A sub-micron conductive carbon layer — typically carbon black, graphite, graphene or a blend, applied with a binder — acts as a functional bridge between metal and active material:
- Increases effective contact area, lowering interfacial contact resistance
- Improves electrode adhesion, reducing delamination
- Protects the aluminum from oxidation and electrolyte corrosion
- Improves rate capability and cycle stability
- Improves electrolyte wettability during filling
It is a small addition in mass terms and a large one in performance terms.
Carbon coated specifications
| Parametru | Typical requirement |
| Base foil alloy | 1050, 1060, 1100, 1235 |
| Base foil thickness | 12–20 μm (9–30 μm available) |
| Coating sides | Single side or double side |
| Carbon layer thickness | ≥1 μm per side (0.5–2 μm range, customisable) |
| Rezistenta la suprafata | ≤5 mΩ (production material commonly measures 1–2 mΩ) |
| Tensiunea de umezire a suprafeței | ≥30 dyne for bare foil; ≥40–50 dyne for carbon-coated |
| Coating adhesion | No delamination after 3M tape pull |
| Solvent resistance | >200 cotton-swab cycles without exposing the foil |
| Electrolyte immersion | No delamination after 24 h |
| Edge margin (neacoperită) | De obicei 15 ± 1 mm |
| Areal density (16 μm, acoperite) | ~42 g/m² |
| Drying compatibility | Vacuum drying up to 150 ° C. |
Single side or double side? Match it to your electrode coating configuration. Double-side carbon coating gives lower interfacial resistance and better high-rate performance, and is standard for power cells and pouch cells. Single side is often sufficient and cheaper for energy cells or where only one face receives active material.
Coating width is matched to your die — common widths include 170 mm, 230 mm, 260 mm and 280 mm, with an uncoated edge margin for welding the tab.
Calitatea suprafeței: where most problems actually start
Surface condition has a direct effect on slurry coating. Contaminare, excess rolling oil, zgârieturi, denivelări, edge cracks or uneven roughness all translate into coating defects and rejected electrode.
Requirements to specify:
- Clean surface with controlled residual rolling oil — this is critical. Residual oil reduces slurry wettability and causes coating defects
- No visible corrosion, oxidation staining, black lines or foreign inclusions
- No folds, zgârieturi severe, val de margine, telescoping or loose winding
- Controlled roughness matched to your coating process
- Stable flatness to support uniform coating and drying
- Slit edges with limited burr and no continuous edge cracking
If you are introducing a new electrode formulation, run trial coils before mass production. Coating behaviour depends on the interaction between your active material, binder, solvent, coating weight and calendaring conditions — the foil is one variable in that system, and the only way to know is to test it.
Inspecție și control al calității
Reputable mills inspect throughout production rather than sampling only at the end. Typical inspection items:
| Articol | Scop |
| Compoziție chimică | Confirms alloy compliance |
| Măsurarea grosimii | Verifies gauge accuracy and uniformity |
| Width measurement | Confirms slit tolerance |
| Tensile strength and elongation | Verifies temper and mechanical stability |
| Surface inspection | Zgârieturi, pete, oil marks, incluziuni |
| Inspecție pinhole | Suitability for thin-gauge use |
| Calitate margine | Bavuri, fisuri, trimming defects |
| Coil shape | Telescoping, loose winding, edge alignment |
Ask for certificates of analysis, coil labels, packing lists and inspection records as contract deliverables. Gauge uniformity across the coil width and length is what reduces your coating weight variation and electrode rejection rate — this is the parameter worth arguing about.
Packaging and storage
Battery foil is sensitive to moisture, praf, mechanical damage and surface contamination.
- Coils should be packed with protective wrapping, moisture-resistant material, edge protection, and export-grade wooden pallets or cases
- Store in a curat, depozit uscat, away from corrosive chemicals, condensation and direct floor contact
- Keep sealed until use — surface oxidation and moisture adsorption degrade coating performance
- Respect first-in, first-out rotation
RFQ checklist
A request that says “folie baterie 13 μm” will not get you a useful quote. Include:
- Base alloy — e.g. 1235
- Thickness and tolerance — e.g. 13 μm, ±5%
- Temper and mechanical requirements — e.g. H18, tensile 120–170 MPa
- Plain or carbon coated — and if coated: single or double side
- Carbon layer thickness — e.g. 1 μm per side
- Width and edge margin — e.g. 230 mm coated width, 15 mm margin each side
- Target surface resistance — e.g. ≤2 mΩ
- Surface cleanliness requirement — residual oil limit, if you have one
- Coil ID / OD and length
- Monthly volume and delivery schedule
- Documents required — COA, MSDS, REACH/RoHS, material test certificate
Frequently asked questions
What is the difference between battery foil and ordinary aluminum foil? Battery foil is a high-purity 1xxx alloy with far tighter controls on gauge uniformity, curățenia suprafeței, residual rolling oil and pinholes. Ordinary packaging foil is not produced to those tolerances and will cause coating defects.
Why is carbon coating used on cathode foil? It lowers interfacial contact resistance between the aluminum substrate and the cathode active material, improves adhesion, protects against corrosion, and improves rate capability and cycle life.
Should I choose single-side or double-side carbon coating? Double side for power cells, pouch cells and high-rate applications where lowest interfacial resistance matters. Single side is often sufficient for energy cells and costs less. Match it to your electrode coating configuration.
How thin can battery aluminum foil go? 12 μm is in volume use for high-energy cells; 10 μm and below exists but supply is limited. Going thinner requires both a capable mill and a well-tuned coating line — otherwise scrap increases faster than energy density improves.
Can sodium-ion batteries use aluminum foil for both electrodes? Da. Sodium does not alloy with aluminum the way lithium does, so both current collectors can be aluminum foil. This is part of sodium-ion’s cost advantage and is contributing to demand growth.
What is the typical lead time and MOQ? Both depend on gauge, coating configuration and volume. Coated and slit foil requires additional processing steps beyond plain foil. State your volume and schedule in the RFQ for an accurate figure.
How should I store carbon coated foil? Sigilat, uscat, curat, below roughly 40 ° C., off the floor, away from condensation and corrosive chemicals, used first-in-first-out.
Discuss your specification
Send us your base alloy, ecartament, temper and coating configuration — or tell us your cell chemistry, energy density target and coating line parameters, and we will recommend a starting specification and arrange trial coils for evaluation.
Battery Grade and Carbon Coated Aluminum Foil: Technical Guide
Battery aluminum foil is the cathode current collector in a lithium-ion cell — the metal substrate that the cathode active material is coated onto, and that carries current out of the electrode. It has no electrochemical role. It does not store energy. And precisely because it is “inert”, it is easy to under-specify.
That is a mistake. Current collector foil affects interfacial resistance, aderența acoperirii, rate capability, cycle life, and the scrap rate on a coating line that may be running at tens of metres per minute. Getting it wrong is expensive in a way that is hard to trace back to the foil.
This guide covers alloy selection, ecartament, temperament, the case for carbon coating, and the parameters worth putting into a specification.
Why aluminum for the cathode and copper for the anode
A useful starting point, because it explains most of the design logic:
| Colector de curent catodic | Anode current collector | |
| Material | Folie de aluminiu | Copper foil |
| De ce | Aluminum forms a stable, passivating oxide layer at cathode potentials, and is light and cheap | Copper is stable at low (anode) potentials but would alloy with lithium |
| Densitate | 2.7 g/cm³ | 8.96 g/cm³ |
Aluminum is used on the cathode because copper would oxidise at cathode voltages, and aluminum because copper would be prohibitively heavy. If you are sourcing for a sodium-ion cell, note that ambele electrodes can use aluminum foil — sodium does not alloy with aluminum the way lithium does. This is one reason sodium-ion is attractive on cost, and it is a growing source of battery foil demand.
Base alloy selection
Battery foil uses the 1xxx series — commercially pure aluminum — because conductivity and purity matter more than strength.
| Aliaj | Typical use | Note |
| 1235 | Most common battery foil alloy | ≥99,35% Al. Good balance of conductivity and cost |
| 1060 | Folosit pe scară largă, slightly higher purity | ≥99.60% Al |
| 1070 | Higher purity requirements | ≥99.70% Al |
| 1050 | Used in some battery and electronic foil | ≥99.50% Al |
| 1100 | Selected where slightly higher strength is needed | Contains minor Cu |
Measured purity on production material typically runs above the specification minimum — a ≥99.0% specification commonly measures ≥99.5% in practice.
Practical advice: don’t over-specify purity unless your electrode chemistry needs it. Every purity step costs money, şi 1235 handles the majority of commercial cathode formulations.
Ecartament: the roadmap, and the pressure to go thinner
Thinner foil means less inactive mass in the cell, which means higher energy density. The entire industry is pushing down.
| Grosime | Position |
| 20 μm | Older standard, still used where handling strength matters |
| 18 μm | Conservative, good process stability |
| 16 μm | Common in volume production |
| 15 μm | Common for higher energy density |
| 13 μm | Current mainstream for high-energy cells |
| 12 μm | High-energy-density cells, demanding process control |
| 10 μm și mai jos | Frontier, limited supply |
For high-energy-density cells, 12–15 μm is the usual selection. For applications where coating-line stability and handling strength matter more than the last few percent of energy density, 18–20 μm gives better process margin and lower scrap.
The trade-off is real: as foil gets thinner it wrinkles and stretches more easily at high speed, cracks more readily at bends, and demands tighter gauge control from the mill. If your coating line is not well-tuned, dropping from 16 μm la 13 μm can cost you more in scrap than it gains in energy density.
Temper and mechanical properties
Battery foil has to balance two failure modes. Too soft and it wrinkles or stretches during high-speed coating and winding. Too hard and it cracks at bends and is difficult to wind.
| Temperament | Typical tensile strength | Typical elongation | Typical use |
| O (anexat) | 60–100 MPa | 3–15% | Applications needing ductility and forming stability |
| H18 (plin greu) | 120-170 MPa | 1–4% | High-strength foil for controlled process lines |
| H19 | 140–190 MPa | 1–3% | Higher stiffness requirements |
Most battery foil is supplied in H18. Actual values depend on alloy, ecartament, rolling reduction and annealing conditions — agree the mechanical property range contractually and require it reported on the material test certificate for each production lot.
Typical reference values for coated product: tensile strength ≥180 MPa, elongaţie >1.5%.
Plain foil vs carbon-coated foil
This is the most important decision in this guide, so it is worth being precise.
The problem carbon coating solves
When cathode slurry is coated directly onto bare aluminum foil, three things work against you:
- Contact resistance. The active material touches the metal only at discrete points. Interfacial contact resistance is high, which hurts rate capability and generates ohmic heating.
- Adeziune. Slurry adhesion to smooth metal is weaker than to a rough, high-surface-area carbon layer. Poor adhesion means delamination during calendaring and cycling.
- Coroziune. The aluminum surface can corrode in contact with electrolyte over long cycling, particularly at higher voltages and with certain chemistries.
What the carbon layer does
A sub-micron conductive carbon layer — typically carbon black, graphite, graphene or a blend, applied with a binder — acts as a functional bridge between metal and active material:
- Increases effective contact area, lowering interfacial contact resistance
- Improves electrode adhesion, reducing delamination
- Protects the aluminum from oxidation and electrolyte corrosion
- Improves rate capability and cycle stability
- Improves electrolyte wettability during filling
It is a small addition in mass terms and a large one in performance terms.
Carbon coated specifications
| Parametru | Typical requirement |
| Base foil alloy | 1050, 1060, 1100, 1235 |
| Base foil thickness | 12–20 μm (9–30 μm available) |
| Coating sides | Single side or double side |
| Carbon layer thickness | ≥1 μm per side (0.5–2 μm range, customisable) |
| Rezistenta la suprafata | ≤5 mΩ (production material commonly measures 1–2 mΩ) |
| Tensiunea de umezire a suprafeței | ≥30 dyne for bare foil; ≥40–50 dyne for carbon-coated |
| Coating adhesion | No delamination after 3M tape pull |
| Solvent resistance | >200 cotton-swab cycles without exposing the foil |
| Electrolyte immersion | No delamination after 24 h |
| Edge margin (neacoperită) | De obicei 15 ± 1 mm |
| Areal density (16 μm, acoperite) | ~42 g/m² |
| Drying compatibility | Vacuum drying up to 150 ° C. |
Single side or double side? Match it to your electrode coating configuration. Double-side carbon coating gives lower interfacial resistance and better high-rate performance, and is standard for power cells and pouch cells. Single side is often sufficient and cheaper for energy cells or where only one face receives active material.
Coating width is matched to your die — common widths include 170 mm, 230 mm, 260 mm and 280 mm, with an uncoated edge margin for welding the tab.
Calitatea suprafeței: where most problems actually start
Surface condition has a direct effect on slurry coating. Contaminare, excess rolling oil, zgârieturi, denivelări, edge cracks or uneven roughness all translate into coating defects and rejected electrode.
Requirements to specify:
- Clean surface with controlled residual rolling oil — this is critical. Residual oil reduces slurry wettability and causes coating defects
- No visible corrosion, oxidation staining, black lines or foreign inclusions
- No folds, zgârieturi severe, val de margine, telescoping or loose winding
- Controlled roughness matched to your coating process
- Stable flatness to support uniform coating and drying
- Slit edges with limited burr and no continuous edge cracking
If you are introducing a new electrode formulation, run trial coils before mass production. Coating behaviour depends on the interaction between your active material, binder, solvent, coating weight and calendaring conditions — the foil is one variable in that system, and the only way to know is to test it.
Inspecție și control al calității
Reputable mills inspect throughout production rather than sampling only at the end. Typical inspection items:
| Articol | Scop |
| Compoziție chimică | Confirms alloy compliance |
| Măsurarea grosimii | Verifies gauge accuracy and uniformity |
| Width measurement | Confirms slit tolerance |
| Tensile strength and elongation | Verifies temper and mechanical stability |
| Surface inspection | Zgârieturi, pete, oil marks, incluziuni |
| Inspecție pinhole | Suitability for thin-gauge use |
| Calitate margine | Bavuri, fisuri, trimming defects |
| Coil shape | Telescoping, loose winding, edge alignment |
Ask for certificates of analysis, coil labels, packing lists and inspection records as contract deliverables. Gauge uniformity across the coil width and length is what reduces your coating weight variation and electrode rejection rate — this is the parameter worth arguing about.
Packaging and storage
Battery foil is sensitive to moisture, praf, mechanical damage and surface contamination.
- Coils should be packed with protective wrapping, moisture-resistant material, edge protection, and export-grade wooden pallets or cases
- Store in a curat, depozit uscat, away from corrosive chemicals, condensation and direct floor contact
- Keep sealed until use — surface oxidation and moisture adsorption degrade coating performance
- Respect first-in, first-out rotation
RFQ checklist
A request that says “folie baterie 13 μm” will not get you a useful quote. Include:
- Base alloy — e.g. 1235
- Thickness and tolerance — e.g. 13 μm, ±5%
- Temper and mechanical requirements — e.g. H18, tensile 120–170 MPa
- Plain or carbon coated — and if coated: single or double side
- Carbon layer thickness — e.g. 1 μm per side
- Width and edge margin — e.g. 230 mm coated width, 15 mm margin each side
- Target surface resistance — e.g. ≤2 mΩ
- Surface cleanliness requirement — residual oil limit, if you have one
- Coil ID / OD and length
- Monthly volume and delivery schedule
- Documents required — COA, MSDS, REACH/RoHS, material test certificate
Frequently asked questions
What is the difference between battery foil and ordinary aluminum foil? Battery foil is a high-purity 1xxx alloy with far tighter controls on gauge uniformity, curățenia suprafeței, residual rolling oil and pinholes. Ordinary packaging foil is not produced to those tolerances and will cause coating defects.
Why is carbon coating used on cathode foil? It lowers interfacial contact resistance between the aluminum substrate and the cathode active material, improves adhesion, protects against corrosion, and improves rate capability and cycle life.
Should I choose single-side or double-side carbon coating? Double side for power cells, pouch cells and high-rate applications where lowest interfacial resistance matters. Single side is often sufficient for energy cells and costs less. Match it to your electrode coating configuration.
How thin can battery aluminum foil go? 12 μm is in volume use for high-energy cells; 10 μm and below exists but supply is limited. Going thinner requires both a capable mill and a well-tuned coating line — otherwise scrap increases faster than energy density improves.
Can sodium-ion batteries use aluminum foil for both electrodes? Da. Sodium does not alloy with aluminum the way lithium does, so both current collectors can be aluminum foil. This is part of sodium-ion’s cost advantage and is contributing to demand growth.
What is the typical lead time and MOQ? Both depend on gauge, coating configuration and volume. Coated and slit foil requires additional processing steps beyond plain foil. State your volume and schedule in the RFQ for an accurate figure.
How should I store carbon coated foil? Sigilat, uscat, curat, below roughly 40 ° C., off the floor, away from condensation and corrosive chemicals, used first-in-first-out.
Discuss your specification
Send us your base alloy, ecartament, temper and coating configuration — or tell us your cell chemistry, energy density target and coating line parameters, and we will recommend a starting specification and arrange trial coils for evaluation.