Riboflavin-functionalized activated carbon delivering high energy storage performance and electrochemical stability assisted by potential control

Pseudocapacitive materials are used to increase the energy density of supercapacitors, but their rate performance and cycling stability are frequently unsatisfactory. Herein, we report a riboflavin-functionalized activated carbon (AC/VB2) as a negative electrode with high specific capacitance (419.1F g−1) and outstanding rate performance. The potent combination of VB2 and AC renders VB2 insoluble in alkaline liquids and fully exploits its redox characteristics. VB2 contributes additional redox reactions to AC and its reaction plateau is from −0.65 to −0.9 V (vs. Hg/HgO), favoring the storage of large amounts of energy. Based on the detailed analysis of the surface state of the material during the reaction, a strategy to improve cycling stability by controlling the charge/discharge potential window is proposed, which can effectively inhibit the desorption and overreaction of VB2, thus greatly enhancing cycling stability. The electrode can be operated stably for 100,000 cycles without any decline at high current densities. An AC/VB2(–)||LDH(+, Co-doped Ni(OH)2) device delivered a high energy density of 58.6 Wh kg−1 at a power density of 686 W kg−1 and a high power density of 27,410 W kg−1 at an energy density of 13.2 Wh kg−1. This work offers a practical manual for making high–energy pseudocapacitive negative electrodes and enhancing their cycling stability.