Fast charging is a critical concern for the next generation of electrochemical energy storage devices, driving extensive research on new electrode materials for electrochemical capacitors and micro-supercapacitors. Here we introduce a significant advance in producing thick ruthenium nitride pseudocapacitive films fabricated using a sputter deposition method. These films deliver over 0.8 F cm^–2 (~500 F cm^–3) with a time constant below 6 s. By utilizing an original electrochemical oxidation process, the volumetric capacitance doubles (1,200 F cm^–3) without sacrificing cycling stability. This enables an extended operating potential window up to 0.85 V versus Hg/HgO, resulting in a boost to 3.2 F cm^–2 (3,200 F cm^–3). Operando X-ray absorption spectroscopy and transmission electron microscopy analyses reveal novel insights into the electrochemical oxidation process. The charge storage mechanism takes advantage of the high electrical conductivity and the morphology of cubic ruthenium nitride and Ru phases in the feather-like core, leading to high electrical conductivity in combination with high capacity. Accordingly, we have developed an analysis that relates capacity to time constant as a means of identifying materials capable of retaining high capacity at high charge/discharge rates.

快速充电是下一代电化学储能设备的关键问题，推动了电化学电容器和微型超级电容器新型电极材料的广泛研究。在这里，我们介绍了使用溅射沉积方法生产厚氮化钌赝电容薄膜的重大进展。这些薄膜可提供超过 0.8 F cm ^–2 (~500 F cm ^–3 ) 的能量，时间常数低于 6 s。通过利用原始的电化学氧化工艺，体积电容加倍（1,200 F cm ^–3），而不会牺牲循环稳定性。相对于 Hg/HgO，这可将工作电位窗口扩展至高达 0.85 V，从而提升至 3.2 F cm ^–2 (3,200 F cm ^–3 )。Operando X 射线吸收光谱和透射电子显微镜分析揭示了对电化学氧化过程的新见解。电荷存储机制利用了羽毛状核中立方氮化钌和Ru相的高电导率和形态，从而实现高电导率和高容量。因此，我们开发了一种将容量与时间常数联系起来的分析方法，作为识别能够在高充电/放电速率下保持高容量的材料的方法。