Percolation Characteristics of Conductive Additives for Capacitive Flowable (Semi-Solid) Electrodes

Abstract

Understanding the percolation characteristics of multicomponent conducting suspensions is critical for the development of flowable (semi-solid) electrochemical systems for energy storage and capacitive deionization with optimal electrochemical and rheological performance. Despite its significance, not much is known about the impact of the selected particle morphology on the agglomeration kinetics and the state of dispersion in flowable electrodes. In this study, the impact of the conductive additive morphology on the electrochemical and rheological response of capacitive flowable electrodes has been systematically investigated. Critical viscosity limits have been determined for common carbon additives that offer slurry formulations with improved electrochemical and rheological performance. For instance, at the same electrical conductivity of 60 mS cm–1, higher aspect ratio particles, such as graphene and carbon nanotubes, offered 4 and 2.4 times lower viscosity compared to carbon black due to the improved packing and conformity of the high aspect ratio particles. On the other hand, thixotropic measurements showed that the flowable electrodes with carbon black exhibit the fastest agglomeration kinetics, offering 25 % less time to recover from the applied shear due to spherical morphology and facile agglomeration kinetics. Overall, our findings show that the particle morphology has a significant impact on the electrochemical and rheological performance of flowable electrodes with up to 40 % difference in capacitance for similar viscosity suspensions. Furthermore, a direct correlation between the rheological and the electrochemical properties was established, offering morphology-independent practical guidelines for formulating slurries with optimal performance. In this manner, particles that can achieve the highest density of packing before the critical limit were found to offer the optimal balance between electrochemical and rheological performance.

Highly conductive colloidal carbon based suspension for flow-assisted electrochemical systems

“…Parant et al (Parant et al, 2017) reported a viscosity above 30 Pa.s at a shear rate of 5 s À1 for optimal acetylene black ll OPEN ACCESS materials. These results show that achieving a compromise of high conduction and flowability remains challenging (Madec et al, 2015;Akuzum et al, 2017Akuzum et al, , 2020Boota et al, 2014;Hauptman et al, 2011;Helal et al, 2016).…”

Systematic Optimization of High‐Energy‐Density Li–Se Semi‐Solid Flow Battery

“…All the optimized suspensions have the suitable viscosity (<1000 Pa s) for SSFBs considering their flowability and electrochemical property. [ 53 ] Therefore, to enhance the utilization of active materials, increase their concentration in suspension, and reduce suspension viscosity, it is an effective way to directly impregnate the active materials and KB in proportion, so no extra KB is needed in suspension.…”

Flow-electrode capacitive deionization enables continuous and energy-efficient brine concentration

“…An upcoming CDI technology suitable for the treatment of higher salinities is flow-electrode capacitive deionization (FCDI) [8]. In case of FCDI, flow electrodes consisting of pumpable carbon suspensions replace the static CDI electrodes, in which charge percolation leads to a utilization of the suspended carbon particles as electrode material [9,10]. Flow electrodes can be regenerated via mixing [11] or in a separate module or compartment, and enable a fully continuous operation.…”