Corrosion of Lithium-ion Battery Cylindrical Cell Hardware: Understanding the Mechanisms and Exploring Effective Solutions

We present a detailed examination of Ni corrosion in lithium-ion battery Ni-coated steel cylindrical cell hardware, focusing on LiPF 6 -based electrolytes contaminated with water. The corrosion potential of the cell hardware is predominantly controlled by the iron component of the cylindrical can which cathodically protects the Ni coating. Despite the presence of cathodic protection, the Ni coating still experiences significant crevice corrosion, as confirmed through chemical aging tests. Mechanistic investigations on pure Ni metal reveal two distinct corrosion pathways depending on the presence or absence of oxygen in the electrolyte. The pathway involving oxygen proves to be more detrimental, as it oxidizes Ni in conjunction with acid, leading to the generation of water and the regeneration of corrosive species. This pathway exhibits corrosion rates two orders of magnitude higher than the alternative pathway. The dissolved Ni species predominantly exist in the +2 oxidation state and forms highly soluble F-rich compounds, comprising a mixture of associated species denoted by the formula Ni(P x O y F z ) w . Finally, several suggestions for effectively mitigating Ni corrosion have been proposed, with alloying with chromium being the most effective.