Why use nickel in battery pack

Nickel is a metal with important industrial value. Its melting point is 1453 ℃, boiling point is 3075 ℃, and specific gravity is 8.8g/cm ³. It has excellent corrosion resistance, is not easy to oxidize in the air, and can remain stable even when heated to 700~800 ℃. At the same time, it has good weldability. These characteristics make it widely used in battery packs.

Welding and connection performance as a transition layer for heterogeneous materials, nickel is suitable for complex connection scenarios in the battery pack:
1. Copper aluminum connection: ultrasonic welding requires horizontal tension ≥ 1500N, vertical tension ≥ 500N, and residual welding area ≥ 1/3. Nickel can alleviate the melting point difference between copper (1083 ℃) and aluminum (660 ℃) and reduce brittle intermetallic compounds.
2. Aluminum nickel connection: the vertical tensile force per unit width is required to be ≥ 3n/mm for polymer diffusion welding. The compatibility of nickel can offset the difference in thermal expansion between aluminum (23.1 × 10 ⁻⁶/℃) and nickel (13.3 × 10 ⁻⁶/℃) to avoid loose connection.
3. Bus bar treatment: the output bus bar adopts electroless nickel plating or electroless nickel plating (the latter coating is more uniform, but the cost is high), reducing welding pores and cracks, and improving the connection strength.

With the core characteristics of "strong corrosion resistance, excellent weldability and stable mechanical properties", nickel and nickel alloys have become the ideal protection and connection materials for copper and aluminum bars in battery packs, as well as the key components for voltage acquisition. The application of nickel sheet mainly solves the problems of dissimilar metal connection and corrosion protection, so as to ensure the safety and performance stability of the battery pack.