Double Sided Polished Copper Foil

Double Sided Polished Copper Foil is characterized by a symmetrical structure of two sides, metal density close to the theoretical density of copper, very low profile of the surface, excellent elongation and tensile strength, and so forth. As the cathode collector for lithium batteries, it has excellent cold/thermal resistance and can significantly extend the battery longevity. Double Sided Polished Copper Foil can be widely applied in batteries for new-energy vehicles, the 3C industry represented by smart phones, notebook computers, and the ESS storage system, and space.

 

 

 

 

Type

High Resistance Copper Foil

copper thickness

4µm

4.5µm

5µm

6µm

7µm

8µm

9µm

12µm

15µm

18µm

20µm

Mass per unit g/m²

35-38

39-42

43-46

50-55

60-65

70-75

85-90

100-105

128-133

155-160

175-180

tensile strength(kg/mm²)

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

≥50.0

Elongation rate(%)

≥2.0

≥2.0

≥2.5

≥3.0

≥3.0

≥4.0

≥4.0

≥5.0

≥6.0

≥8.0

≥8.0

Mechanical thickness(µm)

0,+1

0,+2

0, +3

Surface roughness

Smooth surface

Rz≤3.0 ( perhaps Ra≤0.3)

(µm)

matte side

Rz≤3.0

Wettability

≥36dyne

oxidize resistance

140±2℃ /15min No visible discoloration or oxidation after baking

chemical composition(%): Cu≥ 99.8% (Cu+Ag)

Wide tolerance(MM) ：± 1MM

 

 

Electrolytic Copper Foil Produced via electrodeposition from a copper sulfate solution onto a rotating titanium or stainless steel drum.The deposited copper is peeled off, then treated (roughening, heat resistance, anti-corrosion).

Rolled Copper Foil Made by cold-rolling high-purity copper cathodes into thin sheets, followed by annealing.Surface can be further treated (e.g., oxidation resistance coating).

 

PRODUCTION PROCESS FLOW CHART

 

• Low surface roughness (Rz) on both sides: Typically Rz ≤ 0.5 µm for each side, significantly lower than standard electrolytic copper foil (where the matte side often has Rz > 3 µm).
• Excellent coating uniformity: The smooth and symmetrical surface ensures even spreading of anode slurry, reducing the risk of coating defects and improving active material adhesion.
• Reduced internal resistance: Better contact between the current collector and the anode material lowers interfacial resistance, contributing to improved rate capability and cycle life.
• Thin gauge capability: Available in thicknesses from 4.5 µm to 12 µm, meeting the requirements of high‑energy‑density batteries.
• Good mechanical properties: Maintains adequate tensile strength (≥300 MPa) and elongation (≥3.0 % for 6 µm) for battery manufacturing processes.

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It features excellent physical properties such as fine grain structure, low profile, and high elongation. In the PCB manufacturing process, it offers the advantages of short circuit etching time and highly uniform circuit etching.



It can effectively contribute to improving the energy density of lithium batteries, provides a stable, conductive substrate onto which the anode active material slurry is coated and rolled.aligning with a major trend in the development of future power battery systems for electric vehicles-lightweighting.



With advantages including light weight, high flexibility, improved electrolyte wetting efficiency, and reduced internal resistance of lithium batteries, it significantly enhances the specific energy and charge-discharge rate of lithium-ion batteries.Copper is electrochemically stable within the operating voltage window of the anode, meaning it does not alloy with lithium.



It exhibits good thermal conductivity, excellent processability, ductility, and formability, along with remarkable resistance to softening and high fatigue strength.Collects and transports electrons generated during the battery's discharge phase to the external circuit. Conversely, it distributes electrons evenly during charging

 

 

The rolled copper foil with soft temper used as a conductor in the apparel for cancer treatment research from our Indonesia customer.

Our ED Shielding Copper Foils with High Elongation and High Tensile Strength, can be used in many areas. We can provide the specific single-matte, double-matte, and double-shiny ED Copper for the Li-ion Battery. And we can also offer 2oz to 6oz ( nominal thickness 70um to 210um) Shielded ED Copper Foils used for shielding of electric products, especially as transformer, cable, mobile phone, computer, mechanical treatment, aerospace, and industry Applications . What is more, HTE (high temperature elongation) from 1/2oz to 2oz thickness copper foil and VLP-HTE-HF( very-low-profile, high temperature elongation, and heavy ED Copper Foils, used in PCB, which the max dimension is 1295mm x 2450mm.Below is the US customer Feedback pics for the Shielding Copper Foils used in MRI Room

 

 

 

 

 

 

 

• High‑energy‑density lithium‑ion batteries (EVs, consumer electronics)
• Silicon/silicon‑carbon composite anodes – the smooth surface provides more uniform stress distribution during volume expansion
• Advanced research cells (coin cells, pouch cells) where reproducibility and low interfacial resistance are critical
• Thin‑film batteries and micro‑batteries requiring extremely flat current collector surfaces

 

 

 

Q1:How is it different from regular electrolytic copper foil?

A:Regular electrolytic copper foil has one smooth drum side (Rz < 0.5 µm) and one rough matte side (Rz typically 3–5 µm). Double sided polished foil has both sides smooth (Rz ≤ 0.5 µm). This eliminates the asymmetry and improves coating uniformity.

 

Q2: Why is surface roughness important for battery performance?
A:Lower roughness on both sides ensures more uniform spreading of anode slurry, better adhesion, and lower interfacial resistance between the current collector and active material. This leads to more consistent current distribution, reduced risk of lithium dendrite formation, and improved cycle life, especially at high charge/discharge rates.

 

Q3: Is double sided polished copper foil made from electrolytic or rolled copper?
A:It can be made from either. Most commonly, it is produced by post‑treating standard electrolytic copper foil (polishing the rough matte side). It can also be made from rolled annealed (RA) copper foil, which naturally has smooth surfaces on both sides, then optionally further polished.

 

Q4:What thicknesses are available?
A:Typical thicknesses range from 4.5 µm to 12 µm, with 6 µm, 8 µm, and 10 µm being the most common for high‑energy‑density lithium‑ion batteries.

 

Q5:Does double sided polishing affect mechanical strength?
A:The polishing process itself does not significantly reduce tensile strength or elongation if properly controlled. Typical tensile strength remains ≥300 MPa for 6 µm foil, and elongation ≥3.0 %. However, the base foil quality and any additional passivation treatments also play a role.

 

Q6:Does double sided polished copper foil improve battery cycle life?

A:Yes, in many cases. By providing a more uniform interface, it reduces local current hot spots and mitigates the risk of premature active material delamination. For silicon‑containing anodes, the smooth surface helps distribute expansion stresses more evenly, which can extend cycle life significantly compared to standard rough‑side foil.

 

Q7: What surface roughness values are typical for both sides?
A:Typically, Rz ≤ 0.5 µm and Ra ≤ 0.1 µm on each side. Some ultra‑smooth grades achieve Rz ≤ 0.3 µm.

 

Q8:How does it perform with silicon‑dominant anodes?
A:Very well. Silicon anodes undergo large volume changes during cycling. A smooth, symmetrical current collector provides a more uniform mechanical constraint and better interfacial adhesion, reducing the tendency for the anode film to crack or delaminate. Many silicon‑anode battery developers specify double sided polished copper foil for this reason.

 

Q9:Can double sided polished copper foil be used in solid‑state batteries?
A:Yes. Solid‑state batteries require very flat and defect‑free interfaces to maintain good solid‑solid contact and avoid local overpotentials. Double sided polished copper foil is an excellent candidate for the anode current collector in solid‑state designs.

 

Q10:Is the polished surface still suitable for coating with anode slurry?
A:Absolutely. In fact, the smooth surface improves coating uniformity and reduces pinhole defects. Some users worry about adhesion, but a well‑polished copper surface actually provides better wetting and uniform bonding for most standard anode slurries (graphite, silicon‑carbon, etc.). No special roughening is needed.

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