High corrosion resistance chromium-free passivated copper foils for lithium-ion batteries

Abstract

Presently, the widely electronic copper foil passivation technology in the field of lithium-ion batteries mostly adopts chromate-containing treatment, but there are serious environmental pollution problems. Here, a novel organic-inorganic chromium-free passivation formula was developed by utilising benzotriazole (BTA), 3-chloropropyltriethoxysilane (CPTES) and taking advantage of the corrosion resistance of nickel. The best passivation formula for corrosion resistance treatment was realised by an orthogonal experiment, consisting of 6 g/L BTA, 5 mL/L CPTES and 6 g/L NiSO₄. Through Tafel and impedance tests, the copper foil treated with the passivation solution possesses the most excellent corrosion resistance. The corrosion current density is 1.06 × 10⁻⁶ A·cm⁻², and the corrosion inhibition efficiency reaches 99.5%. Moreover, the surface of the copper foil transformed from hydrophobicity to hydrophilicity. Surface characterisation through X-ray photoelectron spectroscopy, scanning electron microscope etc. results indicate that BTA, CPTES and Ni in the passivation solution participate in the formation of the passivation film. The chromium-free passivation film has been successfully prepared on the surface of copper foil.