Preparation and Properties of an Ultrahigh-Energy-Density Aqueous Supercapacitor with a Superconcentrated Electrolyte and a Sr-Modified Lanthanum Zirconate Flexible Electrode.

Although supercapacitors are considered to play a vital role in flexible electronic devices, there are still some problems that need to be overcome, such as low energy density and narrow electrochemical stability windows in aqueous electrolytes. Herein, we have successfully synthesized a series of Sr-modified La2Zr2O7 (LZO-x) nanofibers as a new electrode material by a facile electrospinning technique. To determine the best doping sample, the changes in structures and electrochemical performances of La2Zr2O7 (LZO-x) nanofibers with various Sr contents are investigated carefully. Then, the LZO-0.2 sample shows the highest capacitance (1445 mF·cm-2). Furthermore, we also develop a low-cost superconcentrated electrolyte, which achieves a wide electrochemical stability window of 2.7 V using a working electrode (LZO-0.2). Finally, we use the LZO-0.2 electrode and the superconcentrated electrolyte to fabricate a flexible supercapacitor device, which shows an excellent capacitance of 175 F·g-1 at a current density of 1.15 A·g-1. Moreover, the aqueous device has excellent cycle stability and outstanding flexibility, and the energy density of this device is 177.2 Wh·kg-1 and the corresponding power density is 1557.7 W·kg-1.