To overcome the intrinsic limitations of energy density and operating voltage in conventional solid-state supercapacitors, a high-voltage solid-state device was developed by integrating titanium-based hollow nanotube array electrodes with a self-synthesized sulfonated poly(aromatic ether) (SPEP) solid electrolyte. The nanotube electrodes fabricated via a rapid wet anodic etching process offer a large accessible surface area and fast ion transport pathways, resulting in a high specific capacitance of 799.9 F g −1 . Low-concentration phosphoric acid was identified as an optimal electrolyte additive, effectively suppressing electrode oxidation while enhancing electrochemical stability. When incorporated into the SPEP matrix, phosphoric acid enabled a stable operating voltage of up to 5 V, far exceeding the voltage limitation of conventional Nafion-based solid-state supercapacitors. As a result, the SPEP-based device achieved a specific capacitance of 63.33 F g −1 , an ultrahigh energy density of 219.91 Wh kg −1 , and a power density of 30,925 W kg −1 , corresponding to 1.3-, 33-, and sixfold improvements over the Nafion-based system. Furthermore, the device exhibited excellent durability, retaining 97.7% of its initial capacitance after 20,000 charge–discharge cycles. This study demonstrates that rational electrolyte–electrode co-engineering enables simultaneous realization of high voltage, high energy density, and long-term stability, offering a scalable strategy for next-generation solid-state supercapacitors.
Yu et al. (Thu,) studied this question.