2.2V High Performance Symmetrical Fiber-Shaped Aqueous Supercapacitors Enabled by “Water-in-Salt” Gel Electrolyte and N-Doped Graphene Fiber

The dominated obstacle facing current quasi-solid-state fiber-shaped aqueous supercapacitors (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，8.96M) 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 20000 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 all-climate aqueous energy device.

当前准固态纤维状水系超级电容器（quasi-solid-state fiber-shaped aqueous supercapacitors, FSASs）体系所面临的主要制约瓶颈为能量密度极为有限，该问题源于电极活性位点不足与电解质工作电压窗口狭窄。针对上述问题，本工作报道了一种新型对称型FSAS，其采用表面褶皱且氮掺杂还原氧化石墨烯纤维（N-doped reduced graphene oxide fiber, NRGF）作为电极，并匹配浓度为8.96M的浓“盐包水”凝胶聚合物电解质（gel polymer electrolyte, GPE）。得益于NRGF的一维多孔微观结构与GPE提升的水合能，所组装的FSAS实现了0~2.2 V的宽化工作电压窗口、高达25.6 μWh cm⁻²（22.7 mWh cm⁻³）的超高能量密度，以及超过20000次循环的优异循环稳定性。该FSAS的电化学性能在不同形变工况下或经多次弯折循环后仍可保持良好。值得注意的是，所制备的FSAS在-20~70 ℃的温度区间内仍可输出8.4 μWh cm⁻²至36.6 μWh cm⁻²的高能量密度，展现出全气候水系储能器件的巨大应用潜力。