The preparation of high-performance aqueous supercapacitor with high-entropy pyrochlore-type electrode and super-concentrated electrolyte

Aluthough High-entropy oxides have the diversity of elements composition and structures, these compounds always maintain a single-phase crystal structure and show excellent physical and chemical properties. Inspired by this, we have synthesized high-entropy pyrochlore oxide (LaY) (Zr0·5Ti0·5Ce0.5Hf0.5)O7 with the sol-gel method, which is denoted as HEPO. To begin with, the HEPO samples calcinated at various temperatures were investigated by using a series of technique, such as TG, FT-IR, XRD and electrochemical workstation and the results indicated that 800 °C was the best processing temperature for HEPO. Besides, a super-concentrated sugar-based solution was used as the electrolyte for the HEPO-800 electrodes and increased the electrochemical window to 3V. Moreover, the HEPO-800 electrode also showed the excellent capacitance of 703.3F·g−1 at a current density of 1A·g−1. Consequently, the symmetrical HEPO-800//HEPO-800 supercapacitor device presents a high capacitance of 128.5F·g−1 at a current density of 3A·g−1. In addition, this device exhibits a high energy density of 160.6 Wh·kg−1 at a corresponding power density of 4500W·kg−1 with outstanding cycling life.