2.2V high performance symmetrical fiber-shaped aqueous supercapacitors enabled by “water-in-salt” gel electrolyte and N-Doped graphene fiber

Quasi-solid-state fiber-shaped aqueous supercapacitors (FSASs) are regarded as one of the most promising candidates for high-performance energy storage devices of wearable consumer electronics, due to outstanding cycle stability, high safety and decent mechanical flexibility. The dominated obstacle facing current FSASs system is their quite limited energy density, which is the consequence of insufficient active sites of electrodes, and narrow operating voltage window of electrolyte. In the light of the outlined issues, a novel symmetric FSAS comprising surface-wrinkled and N-doped reduced graphene oxide (rGO) fiber (NRGF) electrodes matched with concentrated “water-in-salt” gel polymer electrolyte (GPE, 8.96 M) was reported in this work. Benefit from the one-dimensional porous microstructure of NRGF and improved hydration energy of GPE, the assembled FSAS has delivered a widely broadened voltage window of 0–2.2 V, an ultrahigh energy density of 25.6 μWh cm−2 (22.7 mWh cm−3) and an outstanding cycling stability for over 20,000 cycles. The electrochemical performance of this FSAS can be well-maintained even under different deformation conditions or after numerous bending cycles. Interestingly, the as-fabricated FSAS can also deliver high energy density from 8.4 μWh cm−2 to 36.6 μWh cm−2 in a temperature range of -20-70 °C, exhibiting a great potential for wide-temperature aqueous energy device.