镍-钴合金镀钢带及其制成的锂电池钢壳的耐腐蚀性能

Corrosion Resistance of Nickel-Cobalt Alloy Coating on Steel Strip and Lithium Ion Battery Shell Made of the Coated Steel Strip

用于锂电池壳体制备的预镀镍工艺会使钢壳表面有大量裂纹,耐蚀性下降。通过3种方式在钢带上镀覆镍-钴合金层,并冲压制成电池钢壳,采用扫描电镜(SEM)、能谱、X射线衍射(XRD)、电化学测试、中性盐雾试验、硫酸铜点滴试验研究了镀覆钢带和电池钢壳的组织结构和耐腐蚀性能。结果表明:电镀2μm镍-钴合金层经700℃热处理3 h后再加镀2μm镍-钴合金层制备的钢带表层致密均匀,加镀的薄膜封闭了热处理后晶粒间存在的位错等缺陷产生的针孔,具有良好的耐腐蚀性能;电镀4μm镍-钴合金层经700℃热处理3 h制备的钢带冲压而成的电池钢壳表面裂纹少且细小,裂纹处为镍/钴/铁固溶体,耐腐蚀性能明显优于其他2种方式制备的钢壳。

Ni-Co alloy coatings were prepared on the surface of steel strips by electroplating. Resultant steel strips coated with Ni-Co alloy coatings were heat-treated and then made into lithium ion battery shells by stamping. The microstructure and corrosion resistance of the steel strips and battery shells were investigated using a scanning electron microscope, an energy dispersive spectrometer, an X-ray diffractometer and an electrochemical workstation as well as using neutral salt-spray test and dropping corrosion test of aqueous copper sulfate. It was found that when the steel strip coated with Ni-Co alloy coating of 2 μm was heat treated at 700 ℃ for 3 h and further coated with Ni-Co alloy coating of 2 μm, defects like needle-pores originated from intergranular dislocations were sealed, and relevant coated steel strips had dense and uniform surface as well as good corrosion resistance. When the steel strip was coated with Ni-Co alloy coating of 4 μm and then heat treated at 700 ℃ for 3 h, followed by stamping to give battery shell, as-obtained steel shell had few tiny cracks on the surface and possessed considerably improved corrosion resistance, and its cracked zone at the coating-substrate interface was dominated by Ni-Co-Fe solid solution.