Structural Composite Supercapacitors: Electrical and Mechanical Impact of Separators and Processing Conditions

Development of efficient multifunctional structures is of interest for mass reduction of a variety of U.S. Army platforms. Structural batteries and supercapacitors are of particular interest for their ability to provide energy storage in load-bearing materials. Electrical separation of the electrode materials is required to prevent shorting and reduce self-discharge of the energy storage component. Polymer-based separator materials are typically used in traditional energy storage devices. For multifunctional composite applications this separator must also facilitate interlaminar bonding while maintaining chemical and physical compatibility. A series of potential inter-electrode separator materials, including a cellulosic paper, a microglass paper, and a porous polymer membrane, were investigated for adhesion, resistance, and lap shear strength. Vacuum-assisted resin transfer processing setups were used to fabricate composite-based supercapacitors. Throughout processing, resistance through the cells was monitored using a multimeter, and trends in resistance and overall resistivity were determined. Lap shear tests were conducted to better understand the effect each material would have on system strength as well as the separators adhesion to the resin matrix and carbon fabric electrodes. The mode of failure for each material was also determined. The results of the experiments are instrumental in the determination of the proper electrical separator for use in structural energy storage devices. Initial testing on composite matrix and fiber-dominated properties, tensile modulus and short beam shear strength were also conducted. These experiments give significant insight into proper materials, processing methods, and testing protocols for the lab scale production of multifunctional structural batteries and supercapacitors. The original document contains color images. Prepared in collaboration with ORISE, Oak Ridge, TN (1120-1120-99).