I-Corps: Plasma enhanced electrochemical capacitors

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The widespread use of portable electronic devices, e.g., smart phones, and other wireless devices, relies on durable electrical energy storage devices as well as rapid energy delivery. While significant effort and development is underway to improve the energy capacity of batteries which provide such energy, a major issue with the related technology is the relatively poor capability and rate at which at which the energy can be provided. This is reflected for example, in the rapid draining of the battery, e.g., when flash photography is used. Electrochemical capacitors (ECs) constitute a new class of devices that may be used to efficiently produce rapid spurts of electrical power and constitute the topic of discussion in the proposed work. The goals of the project are aimed at alleviating a major issue of presently used ECs, which is that while energy can definitely be supplied in a short time span, the quantity of energy is typically very small. The successful completion of the project, followed by a wide implementation of high energy density ECs will then have a major technological impact. The energy enhanced ECs could be used broadly, (a) in wireless applications and mobile phones, (b) for consumer use, such as e-gift cards and digital cameras, e.g., as flashes in mobile phones, as well as (c) in larger scale utilities, incorporating medical devices, automotive applications, etc. The project aims towards a large societal and environmental impact, e.g., the deployment of electric vehicles could be further accelerated through the use of ECs, which provide sustained acceleration with reduced burden on the battery. The improved capacitance and concomitant energy density would lead to the wider deployment of the ECs, with the potential to even substitute for batteries. The proposed work involves the application of innovative methods to enhance the energy density of the ECs, through the addition of electrical charges introduced through carefully controlled plasma processing. Moreover, charge introduction can enhance the constituent nanocarbon capacitance through exploiting pseudocapacitive contributions in addition to the nominal double-layer charge accumulation. In preliminary experiments, a three-fold enhancement of the capacitance was observed, which lends credence to the hypotheses related to enhanced charge density. Based on these principles, a prototype EC device was constructed in the PI's laboratory. While the initial proof of principle was shown through relatively well controlled nanostructures, e.g., graphene or carbon nanotubes, it is proposed to extend the principles to more widely used nanocarbons such as activated carbon (AC). A large commercial impact would accrue from the fabrication of higher energy density electrodes in the ECs, through relatively cheap industrial scale plasma processing. The close interactions with capacitor manufacturers and with the EC industry would give the team the opportunity to understand issues involved in device manufacture and foster creative engineering attitudes. Several constituent components of the net charge density, incorporating the electrostatic capacitance (e.g., space charge, double-layer, etc.) as well as the quantum capacitance effects would be clarified with respect to their utility in commercial scale ECs.