No abstract

No abstract

Semisolid redox flow batteries simultaneously address the need for high energy density and design flexibility. The electrical percolating network and electrochemical stability of the flowable electrodes are key features that are required to fully exploit the chemistry of the semisolid slurries. Superconcentrated electrolytes are getting much attention for their wide electrochemical stability window that can be exploited to design high-voltage batteries. Here, we report on the effect of the ion concentration of superconcentrated electrolytes on the electronic percolating network of carbonaceous slurries. Slurries based on different concentrations of lithium bis(trifluoromethane)sulfonamide in tetraethylene glycol dimethyl ether (0.5, 3, and 5 mol/kg) at different content of Pureblack carbon (from 2 up to 12 wt %) have been investigated. The study was carried out by coupling electrochemical impedance spectroscopy (EIS), optical fluorescence microscopy, and rheological measurements. A model that describes the complexity and heterogeneity of the semisolid fluids by multiple conductive branches is also proposed. For the first time, to the best of our knowledge, we demonstrate that besides their recognized high electrochemical stability, superconcentrated electrolytes enable more stable and electronically conductive slurry. Indeed, the high ionic strength of the superconcentrated solution shields interparticle interactions and enables better carbon dispersion and connections.

Water-processable natural polymers represent a valuable alternative for the sustainable manufacturing of electrical double layer capacitors (EDLCs). Here, we demonstrate for the first time the feasibility of the use of pullulan to produce high mass loading electrodes (>10 mg cm−2) at low binder content (10%) for ionic-liquid based EDLCs. Pullulan has also been processed as a porous separator by electrospinning. Its ionic resistance and thermal stability have been evaluated in different electrolytes and were found to be superior compared to those of a cellulose triacetate electrospun separator. Pullulan-ionic liquid EDLCs were, thus, assembled and charged up to 3.2 V. The EDLCs delivered specific energy and power of 7.2 Wh kg−1 and 3.7 kW kg−1 and featured good cycling stability over 5000 cycles.