MXene-based suspension electrode with improved energy density for electrochemical flow capacitors

Abstract

The development of high capacitance materials with high packing density and low viscosity in suspension electrodes is critical for progressing towards high-efficiency, low-footprint electrochemical flow capacitors (EFCs). Here, we report on the first electrochemical and rheological characterization of MXene-based suspension electrodes, using multilayer Ti3C2Tx as the active material and carbon black (CB) as the conductive additive in symmetric and asymmetric EFC devices. In the case of symmetric Ti3C2Tx devices, the Ti3C2Tx concentration is fixed to 22 vol.% in the slurry and the CB concentration is varied from 0.5 to 2.0 vol.%. The symmetric device arrangement offers a high capacitance of 240 F ml−1 (2 mV s−1) and volumetric energy density of 2.65 Wh l−1 @ power density of 47.82 W l−1. Additionally, to extend the potential window, an asymmetric device assembly of activated carbon and Ti3C2Tx is investigated. This arrangement allows a stable operating potential window of 1 V with an energy density of 4.12 Wh l−1 and power density of 31.73 W l−1. Overall, multilayer Ti3C2Tx seems to be excellent candidate for flowable electrode applications, offering high capacitance, energy density and low viscosity due to its high electrochemical activity, excellent electrical conductivity, and versatile surface chemistry.