C.X. Meng, F. Zhou, H.Q. Liu, Y.Y. Zhu, Q. Fu,* and Z.-S. Wu*
ACS Energy Letters, 2022, Accepted.
Planar micro-supercapacitors (MSCs)are one key micropower source for microelectronics. However, the pseudocapacitive regulation strategies of extraordinarily multiplying capacitance and energy density of electric double-layer MSCs is underdeveloped. Herein, a versatile strategy for boosting capacitance of graphene-based planar MSCs by highly-concentrated water-in-saltambipolar redox electrolyte (ZnI2+ZnCl2) is proposed, which can serve as anambipolar redox mediator to contribute remarkable pseudocapacitance for positive and negative electrodes simultaneously. The high volumetric capacity of 106 mAh cm-3, unprecedented energy density of 111 mWh cm-3thatoutperfom the reported graphene based MSCs,and long-term cycling stability with 92.1% retention after 5300 cycles are acquired. Thegoodperformance results from the frustrated self-discharge by suppressing the formation and diffusion of polyiodide ions of I3-and I5-, as confirmed by in-situ characterizations.Therefore, this work will open a new avenue of introducing ambipolar redoxmediators into high concentrated electrolytes for high-performance MSCs.