Electrodeposition of metal foils for battery current collectors: Status and challenges

• Introduces electrodeposition of metals for battery current collectors. • Discusses properties of copper, aluminum, titanium, and stainless steel. • Focuses on electrolytic metal foils and their production processes. • Reviews research on metal electrodeposition baths. • Highlights challenges such as composition and inert anode utilization. The pursuit of reliable and sustainable energy storage solutions has driven continuous development of rechargeable lithium ion batteries (LIBs). While substantial progress has been made in the exploration of active materials and battery electrolytes, innovation is also necessary in the metal foils used as current collectors, which are crucial for electron transport between the electrode and external circuits. The manufacturing process, particularly shifting from roll process to electrolytic process, i.e. thinner foils with low cost, can offer potential improvements in energy density and cost. However, challenges associated with replacing the rolling process with electrolytic one are not well recognized, even by battery or electroplating researchers. Therefore, this review aims to provide an updated overview of the electrodeposition process for metals, especially stainless steel, aluminum, and titanium, which can be used as current collector foils but currently manufactured by roll process. The first part of the review introduces the basic properties of several current collector metals. The manufacturing process for electroplated copper foil, which is already widely industrialized, is also briefly explained. The second part addresses the current issues of electrodeposition of stainless steel alloys (which are difficult to improve in terms of crystallinity), as well as aluminum and titanium (which cannot be electroplated from aqueous solutions). The final part provides perspectives for “metal on plastic” foils where additional electrolytic treatment should be engaged toward practical use. Overall, this review provides new insights and guidelines for the development of next-generation current collector foil processing that leverage the expertise of electrolytic processes.