Significance: Filter capacitors play a vital role in rectification and filtering circuits by stabilizing voltage and smoothing electrical signals. With the rapid miniaturization and performance enhancement of electronic equipment—particularly ultra-small devices—there is an urgent demand for filter capacitors that combine high capacitance density, compact size, and excellent frequency response. Traditional dielectric capacitors, although exhibiting excellent frequency response, are constrained by low capacitance density and large volume, preventing them from meeting the integration requirements of modern ultra-small electronic devices. In contrast, electrochemical capacitors, which offer high capacitance in a small volume, have emerged as a research hotspot for ultra-small devices and are widely regarded as promising candidates for next-generation high-end filter capacitors. However, slow ion migration within these electrochemical capacitors severely limits their frequency response, creating a key bottleneck that hinders practical application and industrialization. This underscores the importance of summarizing existing research on electrochemical filter capacitors (EFCs), clarifying key technical issues, and exploring effective solutions to guide future development and advance filter capacitor technology. Progress: To overcome the frequency response limitation caused by slow ion migration, researchers have made progressive breakthroughs in three key areas. First, in selecting electrode material phases, efforts have focused on developing materials with high conductivity, excellent ion accessibility, and stable electrochemical properties—optimizing carbon-based materials (e.g., activated carbon, carbon nanotubes, and graphene) and transition-metal-oxide-based materials to enhance ion transport efficiency within electrodes. Second, in regulating micro-pore structures, hierarchical pore architectures (integrating macropores, mesopores, and micropores) have been designed: macropores serve as rapid ion transport channels, mesopores provide space for ion storage and migration, and micropores increase specific surface area—collectively shortening ion diffusion paths and reducing ionic migration resistance to improve frequency response. Third, in device structure design, innovations such as sandwich-like structures and interdigital electrode structures have reduced overall device volume while optimizing ion transport paths between electrodes. These advances have significantly improved the specific capacitance of EFCs, increasing it from 80μF·cm^-2 to 6mF·cm^-2. Additionally, this paper outlines the development trajectory of EFCs, reviews the latest progress in material systems and multi-scale structure design, and summarizes strategies tailored for high-frequency filtering scenarios (e.g., integrating high-conductivity materials with optimized pore structures and combining device structure innovation with material performance enhancement). Conclusions and Prospects: To enhance performance, future research should focus on optimizing ion migration efficiency. Developing new electrode materials with ultra-high conductivity and designing more efficient ion transport channels can boost the frequency response while maintaining high capacitance density. In industrial-scale manufacturing, challenges such as consistent material preparation, scalable device fabrication, and cost control must be addressed through low-cost, large-scale, high-quality manufacturing technologies. For cross-field applications, EFCs must meet field-specific requirements (e.g., high-temperature stability for automotive electronics and long cycle life for energy storage systems). In conclusion, with continuous advances in materials science, structural design, and manufacturing technology, EFCs are expected to play an increasingly important role in electronic devices; however, further investigation is still required to address existing challenges and fully realize their application potential.