Journal of Power Sources, Vol.295, 108-116, 2015
High voltage electric double layer capacitor using a novel solid-state polymer electrolyte
We designed and fabricated a bipolar-type electric double layer capacitor (EDLC) with a maximum 7.5 V operating voltage using a new concept in solid electrolytes. A cell having a high operating voltage, that is free from liquid leakage and is non-flammable is achieved by a bipolar design utilizing a solid polymer electrolyte made up of particles in a three-dimensional array, such as crystals composed of 75 wt% of hybrid particles decorated with a concentrated ionic liquid polymer brush (PSiP) and 25wt% of an ionic liquid (IL). The resulting solid film had sufficient physical strength and a high enough ionic conductivity to function as an electrolyte. Solidification as well as ionic conduction is due to the regular array of PSiPs, thereby producing a high ion-conductivity from a networked path between cores containing an appropriate amount of IL as a plasticizer. The demonstration cell shows a relatively good cycle durability and rate properties up to a 10C discharge process. It also has a very small leakage current in continuous charging and better self-discharge properties, even at 60 degrees C, compared with conventional cells. This paper demonstrates the first successful fabrication of a bipolar EDLC in a simple structure using this novel polymer solid electrolyte. (C) 2015 Elsevier B.V. All rights reserved.
Keywords:Electric double layer capacitor;Ionic liquid;Polymer solid electrolyte;Bipolar cell design;High voltage