1.What is needed for a button battery casing?
Excellent conductivity: As part of the current loop, resistance must be extremely low.
Superior corrosion resistance: It must be able to resist the erosion of the internal electrolyte (alkaline or organic lithium salt) for extended periods, preventing leakage and rust.
High-precision deep-drawing formability: The casing is a typical miniature deep-drawn part, requiring materials with extremely high plasticity, uniformity, and cupping value. There must be no cracks, necking, or uneven thickness after stamping.
Stable dimensions and mechanical strength: Ensures the battery's sealing performance (with the sealing ring) and resistance to external compression.
Clean surface: Free from oil and particles to ensure the quality of subsequent plating or the reliability of direct contact.
Economy: Cost controllable while meeting performance requirements.
2.What are the advantages and disadvantages of nickel plating on cold-rolled low-carbon steel?
Advantages: Lowest cost.
Good electrical conductivity.
Good corrosion resistance (especially resistance to alkaline solutions) through nickel plating.
Good stamping performance.
Disadvantages/Challenges: Depends on coating quality. Pinholes or uneven thickness in the coating can cause rapid corrosion of the base iron, leading to leakage.
Long-term reliability is at risk in extremely corrosive environments (such as certain lithium salt electrolytes).
3.What are the advantages and disadvantages of austenitic stainless steel?
Advantages: Excellent corrosion resistance, independent of coating, fundamentally eliminating corrosion caused by coating defects.
Better strength and rigidity.
High long-term reliability.
Disadvantages: Significantly higher cost than nickel-plated steel.
Relatively poor electrical conductivity (resistivity 5-7 times that of steel), potentially not optimal for high-current applications.
High stamping hardening rate, requiring sophisticated molds.
4.What is the current state of the industry?
Alkaline button cell batteries (LR): Nickel-plated cold-rolled steel strip is the dominant material due to its optimal balance between cost and performance.
3V lithium-manganese button cell batteries (CR): 304 stainless steel has become the mainstream positive electrode casing material because it reliably resists long-term corrosion from organic electrolytes, ensuring a lifespan of up to 10 years.
5.What are the requirements for the substrate?
Material: Ultra-low carbon steel (such as SPCE, SPCD) to ensure excellent deep-drawing performance.
Performance: Must be in a soft (or extra-soft) state, with low yield strength and high elongation.
Tolerances: Extremely high thickness and width tolerances (micrometer level) are required to ensure stamping stability and sealing.
Surface: Clean and defect-free; surface roughness must match the plating process.