Zn–Ni–Co ternary hydroxide nanoarrays with a controlled morphology are used as the cathode material for supercapacitors for the first time.

Intrinsic defects, including oxygen vacancies, can efficiently modify the electrochemical performance of metal oxides. There is, however, a limited understanding of how vacancies influence charge storage properties. Here, using tungsten oxide as a model system, an extensive study of the effects of structure, electrical properties, and charge storage properties of oxygen vacancies is carried out using both experimental and computational techniques. The results provide direct evidence that oxygen vacancies increase the interlayer spacing in the oxide, which suppress the structural pulverization of the material during electrolyte ion insertion and removal in prolonged stability tests. Specifically, no capacitive decay is detected after 30 000 cycles. The medium states and charge storage mechanism of oxygen‐deficient tungsten oxide throughout electrochemical charging/discharging processes is studied. The enhanced rate capability of the oxygen‐deficient WO3−x is attributed to improved charge storage kinetics in the bulk material. The WO3−x electrode exhibits the highest capacitance in reported tungsten‐oxide based electrodes with comparable mass loadings. The capability to improve electrochemical capacitance performance of redox‐active materials is expected to open up new opportunities for ultrafast supercapacitive electrodes.

Polypyrrole (PPy) is a very promising pseudocapacitive electrode material for supercapacitors. However, the poor electrochemical performances and cycling stability caused by volumetric change and counterion drain severely limited its practical application and commercialization. Herein, we present a pulsepotential polymerization strategy for uniformly depositing a dual-doped PPy with ordered and shorter molecular structure by balancing the concentration polarization. Such a strategy ensures more homogeneous stress distribution of PPy during ultralong cycling tests and improves the cycle stability. Moreover, the pulse-potential polymerized PPy with dual anion doping behavior induces enhanced protonation level and improved electrical conductivity, which boosting the charge transfer kinetics. Therefore, the as-synthesized PPy exhibits a remarkable capacitance performance (7250 mF/cm 2 @ 3 mA/cm 2 ), outstanding rate capability (3073 mF/cm 2 @ 200 mA/cm 2 ) and a long cycle life. The assembled symmetric and asymmetric supercapacitors (ASC) exhibit good energy densities (0.8 mWh/cm 2 for ASC and 0.5 mWh/cm 2 for symmetric supercapacitor), and excellent durability with zero capacitive loss after 35,000 cycles. In addition, we have fabricated small pouch devices, which can effectively operate a variety of electronic products (including the high-voltage 5 V smartphone, and tablet) and well withstand the external extreme tests during operation, demonstrating the quantitative investigation of the real-life application of aqueous supercapacitors.