Symmetrical electrochemical capacitors are attracting immense attention because of their fast charging–discharging ability, high energy density, and low cost of production. The current research in this area is mainly focused on exploring novel low-cost electrode materials with higher energy and power densities. In the present work, we fabricated an electrochemical double-layer capacitor using methylammonium bismuth iodide (CH₃NH₃)₃Bi₂I₉, a lead-free, zero-dimensional hybrid perovskite material. A maximum areal capacitance of 5.5 mF/cm² was obtained, and the device retained 84.8% of its initial maximum capacitance even after 10 000 charge–discharge cycles. Impedance spectroscopy measurements revealed that the active layer provides a high surface area for the electrolyte to access. As a result, the charge transport resistance is reasonably low, which is advantageous for delivering excellent performance.

中文翻译：

---

零维甲基铵碘化铋基无铅钙钛矿电容器

对称电化学电容器因其快速充放电能力、高能量密度和低生产成本而备受关注。目前该领域的研究主要集中在探索具有更高能量和功率密度的新型低成本电极材料。在目前的工作中，我们使用无铅、零维混合钙钛矿材料甲基碘化铋 (CH ₃ NH ₃ ) ₃ Bi ₂ I ₉制造了电化学双层电容器。最大面电容为 5.5 mF/cm ²获得，并且即使在 10 000 次充放电循环后，该器件仍保持其初始最大电容的 84.8%。阻抗光谱测量表明，活性层​​为电解质提供了高表面积。结果，电荷传输电阻相当低，有利于提供优异的性能。