Why Is Copper And Zinc Prohibited in Lithium Battery Production? ——Zimflex Hose Knowledge Explanation

Quick overview: The prohibition of the use of copper and zinc in lithium-ion batteries stems from the fact that copper and zinc ions can undergo dissolution–reprecipitation reactions within the battery cell, forming dendrites that penetrate the separator, leading to internal short circuits and thermal runaway; additionally, the galvanized coating may delaminate and powderize in the presence of NMP solvent and the ambient humidity in the workshop, directly contaminating the powder. Therefore, the hose framework used in lithium-ion battery production lines must be replaced with a 304 stainless steel spiral wire, ensuring both continuous conductive static discharge and the prevention of metal deposition; the hose manufacturing process should employ a single-step co-extrusion technique to achieve a fully smooth inner wall. These hoses are utilized in processes such as coating, rolling and slitting, winding and stacking, electrolyte filling, capacity optimization, powder vacuum feeding, and centralized dust collection in the workshop.

I. Why the use of copper and zinc is not permitted in lithium-ion battery production?

Lithium-ion batteries have extremely low tolerance for metallic impurities. The cathode powder, anode graphite, and electrolyte possess high chemical reactivity; therefore, if zinc, copper, or iron ions enter the battery material due to pipeline wear or corrosion, they can create irreversible failure risks within the cell. The industry generally classifies copper, zinc, and iron as metallic contaminants that require strict control.

1. Copper: Trace amounts of copper ions can induce dendrite formation, which may penetrate the separator.

The standard electrode potential of copper is approximately +0.34 V (relative to Li/Li⁺). Under the high-potential conditions at the cathode, copper is oxidized and dissolved into Cu²⁺ ions, which then enter the electrolyte; upon migrating to the anode, these ions are reduced back to metallic copper and deposit as dendrites. When the dendrites grow to a certain extent, they may pierce the separator, causing direct contact between the cathode and anode and resulting in an internal short circuit. In mild cases, this leads to increased self-discharge and accelerated capacity degradation; in severe cases, it can trigger thermal runaway. Consequently, the lithium-ion battery industry typically enforces stringent control over the presence of copper contaminants at concentrations on the order of ppm; some power battery production lines impose even more rigorous requirements.

2. Zinc: The zinc coating "falls" into powder due to the workshop environment.

The electrode potential of zinc is approximately –0.76 V; under these conditions, zinc undergoes dissolution–reprecipitation within the battery, forming zinc dendrites that can penetrate the separator. A more practical risk arises from the galvanized steel wire itself: during the coating and electrolyte filling processes, NMP solvent and water vapor are released, creating condensation within the workshop; under such conditions, the galvanized layer may delaminate or powder, allowing zinc powder and zinc ions to be directly mixed into the positive and negative electrode powders, resulting in batch-related contamination.

3. Iron: Rust particles causing black spots and excessive self-discharge

Ordinary carbon steel wire rusts rapidly in humid environments; when the rust particles are mixed into the powder, they form black spots on the electrode sheet, causing the self-discharge performance to exceed the specified limits, resulting in the finished product having to be downgraded or scrapped.

4. Comparison of Hazards and Control Measures for Three Metals

II. Why is copper-plated steel wire not typically used for electrostatically grounded hoses?

The conveying and dust removal of lithium battery powders require the dissipation of static electricity. Ultrafine powders-such as graphite, silicon-carbon, and lithium iron phosphate-can generate and accumulate static charges under the frictional action of high-speed airflow; once this static charge is discharged, it may serve as an ignition source for combustible dust. The metal spiral wire within the hose skeleton acts as a pathway for conducting static electricity from the hose into the ground. For this pathway to function effectively, the metal wire must simultaneously satisfy two conditions:

1.Continuous conductivity: A continuous conductive path is formed from the tube body to both end connections;

2.No introduction of metal contamination: The material must not release copper, zinc, or iron ions.

General industrial dust collection hoses often utilize copper-plated steel wire to ensure conductivity. However, this practice is prohibited on lithium-ion battery production lines – as copper ions can contaminate the battery cells, and the conductive pathway may be interrupted if the copper coating undergoes oxidative wear.

304 stainless steel wire meets two requirements simultaneously: it forms a dense passivation film on its chromium-nickel alloy surface, preventing the precipitation of copper, zinc, or iron ions; at the same time, it exhibits stable volumetric resistance, allowing any static electricity accumulated inside the hose to be continuously discharged into the ground when the two ends of the hose are grounded.

Model selection reminder: Standard 304 stainless steel does not contain copper; however, certain machinable or antibacterial stainless steel grades that contain copper are available on the market. For applications involving lithium-ion batteries, please confirm with your supplier that the steel wire is 304 stainless steel without copper.

III. Where is 304 stainless steel wire reinforcement used for PU soft tubes applied in lithium-ion battery manufacturing processes?

Depending on whether it is used in the upstream, midstream, or downstream stages of lithium battery manufacturing, the hose is primarily employed for four types of operations: dust suction, exhaust gas discharge, vacuum conveying, and the transition between gas and liquid flows.

Front End · Polar Film Manufacturing

Mixing (slurry preparation): feeding and dust removal systems for slurry mixing and dispersion equipment; exhaust piping;

Coating: The exhaust gas suction pipeline for the NMP solvent volatilization process in the coating machine's drying oven must be resistant to solvent corrosion;

Rolling: Dust and edge material extraction from the rolling machine;

Shearing/Cutting: Absorption of active material dust generated during electrode sheet shearing or cutting; complemented by brush dust removal and vacuum cleaning systems;

Electrode sheet dust removal: A vacuum suction system for cleaning the electrode sheet surface.

Mid-Stage · Cell Assembly

Winding/Stacking: Vacuum-assisted handling of electrode sheets; Dust removal piping system for separators and electrode sheets;

Lead terminal welding: suction of welding fumes and metal splashes generated during laser welding;

Encapsulation/Package Assembly: Dust extraction at the assembly station;

Electrolyte filling: The exhaust gas suction system for the electrolyte filling machine must be resistant to the volatilization atmosphere of the electrolyte.

Final Stage · Chemical Composition Separation and Drying

Final Assembly / Capacity Distribution: Negative pressure suction and exhaust gas discharge pipelines for the final assembly cabinet and capacity distribution cabinet;

Drying Room / Dehumidification: Gas supply and exhaust ductwork for the drying room's air conditioning system.

Full-Scale Powder Transportation and Dust Removal System

Powder vacuum feeding: vacuum feeding, vacuum lifting, and pneumatic conveying for graphite, silicon-carbon, and lithium iron phosphate raw materials; the system operates under a continuous negative pressure range of –0.04 to –0.08 MPa;

Screening/Iron Removal: Conveying and dust removal pipelines at the feed and discharge ports of the screening machine;

Central dust collection: branch pipes and terminal suction pipes of the workshop centralized dust collection system;

PACK Assembly: Dust extraction for the energy storage PACK and the 3C soft-pack battery grinding station.

IV. Process – Equipment – Hose Application Correspondence Table

V. Why must the inner wall be completely smooth?

The inner wall of a hose manufactured using the conventional two-step coating process features concentric rings of steel wire protrusions and grooves; in lithium-ion battery applications, this design poses four types of potential hazards:

Self-ignition of powder: When ultrafine powder is stored for an extended period in a groove, the slow oxidation process releases heat; once the self-ignition temperature is reached, combustion occurs; the Dust Explosion Prevention Code also requires that the inner surfaces of air ducts be smooth and free of dust accumulation;

Cross-contamination: Old powder material accumulated in the trench may occasionally shed and mix into the new batch of raw materials, adversely affecting battery capacity and cycle consistency;

Increased wind resistance: The raised inner wall induces airflow vortices, leading to higher wind resistance and increased fan energy consumption; when the wind velocity within the pipe is insufficient, it can also accelerate dust deposition and cause pipe blockage;

Cleaning difficulty: The grooves cannot be thoroughly cleaned during material replacement; therefore, the pipes must be disassembled and cleaned, which increases downtime.

The mirror-like inner wall, produced by the single-step co-extrusion process, features no steel wire protrusions; the material is completely carried away by the airflow, and cleaning can be accomplished simply using compressed air blowdown. As a result, this design offers a longer service life compared to conventional corrugated pipes.

VI. Mandatory Procurement Standards for Lithium Battery Soft Pipes

Steel wire: 304 stainless steel spiral wire only; galvanized, copper-plated, or ordinary iron wire shall not be used;

Forming process: One-step co-extrusion creates a fully smooth inner wall – upon touch, there are no steel wire ridges or wavy grooves;

Anti-static: The steel wire maintains continuous conduction, with its surface resistance stabilized between 10⁶ and 10⁹ Ω; the two ends of the wire are reliably grounded.

Negative pressure resistance: Capable of withstanding long-term negative pressures ranging from-0.04 to-0.08 MPa without flat deformation;

Compliance documentation: Third-party test reports (e.g., for no copper/zinc precipitation, anti-static properties, and RoHS compliance) may be provided.

VII. Frequently Asked Questions

Q1: Why can't galvanized steel wire be used for lithium-ion battery hoses?

The galvanized coating may delaminate and powder under conditions involving NMP solvent, water vapor, or condensation; zinc powder and zinc ions may then be introduced into the powder mixture. Additionally, zinc can deposit within the battery cell, forming dendrites that penetrate the separator. Furthermore, wear of the coating can lead to insulation discontinuities, preventing the dissipation of static electricity.

Q2: Copper-plated steel wire offers better conductivity – why is it not used instead?

Copper ions are a highly hazardous impurity in lithium-ion battery systems; they can dissolve and deposit, forming copper dendrites that cause internal short circuits; additionally, the copper coating is prone to oxidation and blackening, which can disrupt the electrical conduction path.

Q3: Can a standard hose with steel wire protrusions on its inner wall be cleaned using compressed air?

The powder accumulated in the groove is difficult to blow away; therefore, during material changeover, it is often necessary to disassemble the pipe for cleaning, which can also lead to batch cross-contamination.

Q4: Does ZIMFLEX (蚱蜢) offer models compatible with lithium-ion batteries?

Yes. ZIMFLEX provides 901-SS 304 stainless steel wire inner-plain PU soft tubing; the core consists of 304 stainless steel spiral wire free of copper and zinc, with a single-step co-extruded mirror finish – the surface resistance is stabilized between 10⁶ and 10⁹ Ω. Standard specifications cover DN25 to DN300; stock is available at dual warehouses in Shanghai and Foshan, with minimum order quantity of 10 meters.

Q5: Besides lithium-ion batteries, in what other scenarios are these hoses suitable?

This same design is also applicable to conveying and dust removal applications involving materials sensitive to metal contamination, such as food powders, pharmaceutical excipients, and chemical powders.

ZIMFLEX Grasshopper – Over 3,000 SKUs in stock, covering pipe diameters from DN6 to DN300; over 5,000 long-term customers; dual regional warehouses in Jiashan and Foshan; standard orders shipped within 48 hours; 24/7 engineer support; provides service condition assessment, component selection and adaptation, and pressure testing solutions.

Overcoming rigidity with flexibility, building a career on quality – in industrial piping systems, no detail is too small; every hose serves as a vital safety barrier.