Tuning the interlayer spacing of graphene laminate films for efficient pore utilization towards compact capacitive energy storage

The volumetric performance of supercapacitors needs to be improved, but the usual trade-off between porosity and density is a problem. Here the authors develop a graphene laminate film with tunable porosity that leads to a volumetric energy density of 88.1 Wh l(-1) at the device level. Supercapacitors have shown extraordinary promise for miniaturized electronics and electric vehicles, but are usually limited by electrodes with rather low volumetric performance, which is largely due to the inefficient utilization of pores in charge storage. Herein, we design a freestanding graphene laminate film electrode with highly efficient pore utilization for compact capacitive energy storage. The interlayer spacing of this film can be precisely adjusted, which enables a tunable porosity. By systematically tailoring the pore size for the electrolyte ions, pores are utilized optimally and thereby the volumetric capacitance is maximized. Consequently, the fabricated supercapacitor delivers a stack volumetric energy density of 88.1 Wh l(-1) in an ionic liquid electrolyte, representing a critical breakthrough for optimizing the porosity towards compact energy storage. Moreover, the optimized film electrode is assembled into an ionogel-based, all-solid-state, flexible smart device with multiple optional outputs and superior stability, demonstrating enormous potential as a portable power supply in practical applications.