A universal strategy to improve interfacial kinetics of solid supercapacitors used in high temperature

The growing application domain of energy storage devices (ESDs) is leading research to temperature tolerant supercapacitors. To realize reliable and safe devices, high modulus solid electrolytes are favored by most researchers. However, the inferior infiltrating ability of such electrolytes usually results in poor electrochemical performances of the ESDs. Herein, we adopted a hierarchical optimization strategy to address the aforementioned interfacial issues. Continuous ionic percolation throughout the hierarchical pores of the 3D electrode was formed by in-situ introducing an ionogel buffer layer. Benefiting from this, the rate of ions diffusing within electrodes was increased by 5 times. Furthermore, the kinetics of ions entering into nanopores was improved via introducing small size ions into ionic liquids (ILs) and adjusting the solvated structures. Both the capacity and rate performance of the electrochemical double layer capacitors (EDLCs) were improved. Additionally, the buffer layer exhibited sufficient thermostability to cooperate with poly(ether ether ketone) (PEEK)-based solid electrolyte. Consequently, the EDLCs exhibited excellent cycling stability (79% capacitance retention after 5000 cycles) at 120 °C and delivered a maximum energy density of 46.9 Wh kg^-1 with a power density of 926.9 W kg^-1. Our strategy is believed to be effective to cooperate with various solid electrolyte systems and offer a general design principle for durable and high performance EDLCs.