Organic Solvent Boosts Charge Storage and Charging Dynamics of Conductive MOF Supercapacitors

Abstract

AbstractConductive metal–organic frameworks (c‐MOFs) and ionic liquids (ILs) have emerged as auspicious combinations for high‐performance supercapacitors. However, the nanoconfinement from c‐MOFs and high viscosity of ILs slow down the charging process. This hindrance can, however, be resolved by adding solvent. Here, constant‐potential molecular simulations are performed to scrutinize the solvent impact on charge storage and charging dynamics of MOF‐IL‐based supercapacitors. Conditions for >100% enhancement in capacity and ≈6 times increase in charging speed are found. These improvements are confirmed by synthesizing near‐ideal c‐MOFs and developing multiscale models linking molecular simulations to electrochemical measurements. Fundamentally, the findings elucidate that the solvent acts as an “ionophobic agent” to induce a substantial enhancement in charge storage, and as an “ion traffic police” to eliminate convoluted counterion and co‐ion motion paths and create two distinct ion transport highways to accelerate charging dynamics. This work paves the way for the optimal design of MOF supercapacitors.