High-voltage MIM-type aluminum electrolytic capacitors

Metal-insulator-metal aluminium electrolytic capacitors (MIM-AECs) combine high capacity-density and high breakdown field strength of solid AECs with high-frequency responsibility, wide working-temperature window and waterproof properties of MIM nanocapacitors. However, interfacial atomic diffusion poses a major obstacle, preventing the high-voltage MIM-AECs exploitation and thereby hampering their potential and advantages in high-power and high-energy-density applications. Here, an innovative high-voltage MIM-AECs were fabricated. The AlPO₄ buffer layer is formed on AlO(OH)/AAO/Al surface by using H₃PO₄ treatment, then a stable van der Waals (vdW) SnO₂/AlPO₄/AAO/Al multilayer was constructed via atomic layer deposition (ALD) technology. Due to higher diffusion barrier and lower carrier migration of SnO₂/AlPO₄/AAO interfaces, Sn atom diffusion is inhibited and carrier acceleration by electric field is weakened, guaranteeing high breakdown field strength of dielectric AAO and avoiding local breakdown risks. Through partial etching to hydrated AlO(OH) by H₃PO₄ treatment, the tunnel was further opened up to facilitate subsequent ALD-SnO₂ entry, thus obtaining a high SnO₂ coverage. The SnO₂/AlPO₄/AAO/Al capacitors show a comprehensive performance in high-voltage (260 V), high-temperature (335 °C), high-humidity (100% RH) and high-frequency response (100 kHz), outperforming commercial solid-state AECs, and high-energy density (8.6 µWh/cm²), markedly exceeding previously reported MIM capacitors. The work lays the foundation for next-generation capacitors with high-voltage, high-frequency, high-temperature and high-humidity resistance.