<p>Etched aluminum foil plays a crucial role in enhancing the performance of aluminum electrolytic capacitors, particularly in medium- and high-voltage applications. Over recent decades, substantial research has focused on optimizing the structure and morphology of etched tunnels to improve capacitor efficiency. This review provides a comprehensive overview of the electrochemical etching processes commonly used to fabricate aluminum foils, exploring the various preparation techniques, structural characteristics, and morphological developments. It also examines the challenges and limitations faced by these technologies, such as scalability, cost-efficiency, and the uniformity of tunnel distribution, which have hindered their large-scale industrial adoption. Furthermore, this article critically analyzes the most promising future research directions, including innovative etching techniques, novel additives, and process optimizations. It identifies key areas where breakthroughs are essential to advancing the technology and enhancing the performance of aluminum electrolytic capacitors. By addressing these challenges, the potential for improved capacitor efficiency, higher specific capacitance, and longer lifespans will be realized, benefiting industries such as renewable energy, electric vehicles, and consumer electronics.</p>