SOFT HYDROGEL BATTERIES: THE DANIELL CELL CONCEPTUALIZED IN HYBRID HYDROGELS
Raghavan, Srinivasa R
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Energy storage devices such as batteries are important elements in many electronic devices. Currently, researchers are seeking to create new electronic devices that are "soft", i.e., bendable and stretchable. However, the batteries that power such devices are still mostly hard structures. In the current thesis, we have attempted to develop a "soft" battery out of hydrogels. Specifically, we have made a soft version of the Daniell Cell, which is a classic electrochemical cell. Our design involves a hybrid gel composed of three distinct layers. The top and bottom layers are gels swollen with a zinc salt and a copper salt, respectively, while the middle layer is akin to a "salt bridge" between the two. The hybrid gel is made by a polymerization technique developed in our laboratory and it retains good mechanical integrity (i.e., the individual layers do not delaminate). Zinc and copper foils are then attached to the hydrogel, thus creating an overall battery, and its discharge performance is reported. One unique aspect of these gel batteries is that they can be dehydrated and stored in a dry form, whereupon they are no longer batteries. In this inactive state, the materials are safe and light to transport. Upon rehydration, the gels revert to being functional batteries. This concept could be useful for military or other applications where an emergency energy storage is needed.