Nickel's Role in EV Battery Packs - Busbar Manufacturer Insight

Why High-End EV Battery Packs Depend on Nickel: Insights from a Busbar Manufacturer

In EV battery pack design and manufacturing, material selection directly affects system safety, reliability, and service life. Nickel, though not the main conductor, is a critical functional material in electrical connections. This article explores nickel’s role in battery packs, referencing industry practice and national standards.

1. Nickel Properties and Standards

Material Characteristics
Nickel provides excellent corrosion resistance, stable electrical and thermal conductivity, strong mechanical properties, and good weldability. It maintains surface stability in humid or acidic environments, reducing electrochemical corrosion, and bonds reliably with copper, aluminum, and steel.

Grades in China (GB/T 5235):

• N4 (≥99.9% Ni+Co): ultra-high purity for demanding applications.

• N6 (≥99.5% Ni+Co): balanced performance and cost, widely used in battery connectors.

• N8 (≥99.0% Ni+Co): for general industrial use.

Processing Conditions (GB/T 17792):

• M (annealed): ductile, suitable for stamping (e.g., sensing tabs).

• Y2 / Y (half-hard / hard): higher strength, for stiff components.

Battery packs typically use N6 or higher grades to ensure material consistency and stability.

2. Nickel in Copper–Aluminum Connections

1. Corrosion Prevention
Direct Cu–Al contact creates a ~2V potential difference, causing galvanic corrosion and connection failure. Nickel, with an intermediate potential, serves as a buffer layer, greatly improving long-term reliability.

2. Nickel-Plated Busbars
Copper or aluminum busbars are plated with a 3–8 μm nickel layer (GB/T 9797), ensuring:

• Dense, uniform coating with strong adhesion.

• Neutral salt spray resistance ≥96h.

• Stable, low-resistance interfaces.

This is widely applied in battery modules to avoid Cu–Al direct contact corrosion.

3. Nickel Tabs for Flexible Busbar Connectors
For laminated copper or aluminum foils, nickel tabs are laser-welded or brazed at terminals. These act as a welding transition layer, improve aluminum weldability, reduce vibration fatigue, and isolate Cu–Al contact.

4. Improved Welding Quality
Nickel bonds well with copper and tin, reducing weak joints and cracks. Welds achieve higher strength and conductivity compared with direct Cu–Al welding.

3. Nickel Tabs for Voltage Sensing

Material Compliance and Core Performance
Voltage sensing tabs typically use annealed N6 pure nickel strip, offering stable resistivity and strong high-temperature oxidation resistance. The material fully complies with QC/T 29106 Automotive Wire and Cable Technical Requirements for BMS sensing applications.

• Material: Soft N6 nickel strip, stable resistivity, high oxidation resistance, compliant with QC/T 29106 (automotive BMS).

• Surface: Clean, burr-free, bright annealed or passivated for weldability and oxidation resistance.

• Performance: Laser-welded to aluminum terminals with tensile strength ≥80 MPa, low contact resistance, durable under vibration and fatigue.

4. Cost and Process Considerations

• Material Cost: Nickel is more expensive than copper or aluminum, but usage as plating or small tabs keeps costs low.

• Process Cost: Extra plating or welding steps increase processing, but significantly enhance connection reliability and reduce risks of failure or recall.

• Comparison with Cu–Al Composite Busbars:
  Cu–Al composite busbars rely on ultrasonic welding, brazing, diffusion welding, or friction welding. While effective in reducing direct contact, long-term fatigue under vibration and thermal cycling remains a challenge.

Nickel plating or nickel tabs, by forming stable Ni–Ni or Ni–Sn joints, offer superior chemical stability, mechanical strength, and proven long-term performance. For high-reliability, long-life battery systems, nickel remains the preferred solution.

Nickel may not be the primary conductor in EV battery packs, but it is essential for ensuring long-term connection reliability. By preventing galvanic corrosion, improving weld integrity, and stabilizing sensing signals, nickel safeguards system safety.

At RHI, we focus on nickel material selection (compliant with GB standards), plating, and welding technologies. Every electrical busbar and sensing tab is engineered for consistency and reliability.

With professional connection technologies, RHI empowers safe and efficient green energy.