Production process of electrolytic copper foil
The production process of electrolytic copper foil mainly involves melting copper into sulfuric acid to prepare an electrolytic copper solution. This solution is then fed into a foil-making machine(ED machine), where the copper foil is obtained by passing an electric current through titanium cathode drums controlled by adjusting the speed and magnitude of the current.
The basic processes for manufacturing PCB copper foil and lithium battery copper foil are similar. Both undergo electronic processing, utilizing main equipment composed of ED machines and titanium cathode drums. The most significant difference lies in the surface treatment process: PCB copper foil involves a more complex surface treatment, whereas lithium battery foil only requires anti-oxidation treatment.
The production process of electrolytic copper foil primarily involves four parts: raw foil formation, surface treatment, cutting, and inspection and packaging.
Raw Foil Formation: The raw foil process comprises procedures such as copper dissolution, foil formation, and stripping. Refer to the specific raw foil production process for details.
Surface Treatment: Surface treatment primarily involves processes like acid washing, roughening, anti-oxidation, and passivation. (This surface treatment process is exactly for PCB copper foil. For lithium battery copper foil, it just needs anti-oxidation.)Please refer to the surface treatment process for specifics.
Cutting: Post-surface treatment, the finished products are cut into specifications required by customers using a slitting machine.
Inspection and Packaging: Qualified finished products undergo inspection and subsequent packaging.
First, the raw foil production process
| Raw Copper Materials | Processes | Equipment |
| Copper sulfate / Electrolytic copper | Copper dissolving | Dissolution tank |
| Low-level reflux | Low-level tank | |
| Purification | Filter | |
| Low-level clean solution | Storage liquid tank | |
| High-level tank transfer | High-level tank | |
| Raw copper foil | ED machine | |
| Rinsing | ED machine | |
| Stripping | ED machine | |
| Copper foil |
① Copper Dissolution (Preparation of Electrolyte)
Sulfuric acid enters the sealed low-level tank through a closed pipeline. From there, it proceeds through a closed pipeline into the copper dissolution tank for copper plate spraying. Copper plates are fed into the dissolution tank through the tank cover opening. Fifteen minutes before feeding, the valve allowing sulfuric acid from the low-level tank into the dissolution tank is closed. The waste gas from the dissolution tank is collected through a strong suction form via the waste gas collection pipe and is drawn into the acid mist waste gas treatment tower for treatment before being discharged. The dissolution tank maintains a negative pressure suction state throughout the feeding and copper dissolution process, and both the copper dissolution waste gas and sulfuric acid mist are systematically discharged. Each group of dissolution tanks adds copper plates for approximately one hour per day.
The technological processes and production controls of copper dissolution directly determine the stability of copper foil product quality. This primarily affects subsequent factors such as foil flatness, tensile strength, elongation, surface roughness, and surface quality, consequently influencing the yield of negative electrode products, battery capacity, internal resistance, cycle life, battery consistency, stability, and capacity magnitude.
② Raw Foil Production
The process of raw foil production is an electrochemical procedure where divalent copper ions, influenced by an electric field, deposit electrons onto the cathode drum’s surface. This deposition leads to the precipitation of ions, forming raw foil of a certain thickness. By adjusting the rotation speed of the cathode drum under specific current densities (30000-60000Am), varying thicknesses of copper foil can be manufactured. As the cathode drum rotates, copper foil of a specific thickness is continuously peeled off from the drum. Subsequently, it undergoes processes such as rinsing (where the rinse water directly enters the low-level tank for reuse without external discharge) and stripping before being finally wound into copper foil rolls.
Given that electrolytic copper foil is deposited on the surface of the cathode drum, reflecting its surface structure, the condition of the cathode drum surface directly determines the condition of the copper foil surface. Therefore, the critical aspect of the cathode drum lies in obtaining a titanium ring with a high surface grain size and a fine microstructure. Factors such as the smoothness, uniformity, and flatness of the cathode drum’s titanium ring surface, as well as microscopic grain size and electrochemical properties, all impact the crystalline state of the electrolytic copper foil, thereby influencing the physical properties of the copper foil. Excessive roughness of the titanium ring surface can deteriorate the condition of the copper foil, thus affecting the performance of lithium-ion battery negative electrodes.
In the next article, we will share the process of surface treatment, and if you want to know more about the copper foil production facilities, you can click this link https://cstitaniums.com/product-category/electrodeposited-copper-foil-manufacturing-facilities/