Biodegradeable Supercapacitors

Lab Note #4
Sep 19, 2014

The continued research and development of greener, cheaper, lighter, more efficient energy storage is required to keep pace with the current and future functionalities of consumer electronics and portable devices. The forecast of the consumer electronics market projects that new, emerging product categories will grow by 107 percent year-over-year in 2014. These new technology categories, including 3D printers, Bluetooth wireless speakers, convertible PCs, health and fitness devices, smart watches and Ultra HD television displays, are cumulatively expected to contribute more than $6 billion to the overall CE industry in 2014. While these emerging product categories represent less than three percent of the entire CE industry, they drive 65 percent of total industry revenue growth. Additionally, consumer electronic products are becoming increasingly thinner, more power-hungry, multi-functional and capable of more efficient energy use to satisfy an ever-increasing number of variable power demands. The United States is the world leader in producing electronic waste.

Batteries underperform in today’s smart devices and are the primary limitation for future development of new features. Furthermore, all electronic scrap components, including batteries, can contain environmental contaminants such as lead, cadmium, beryllium, or brominated flame retardants. Electrical waste not only contains hazardous, but also valuable and scarce materials. Up to 60 different elements can be found in complex electronics. An estimated 50 million tons of E-waste are produced each year. For example, the USA discards 30 million computers and Europe, 100 million phones each year. The Environmental Protection Agency estimates that only 15-20% of e-waste is recycled, the rest of these electronics go directly into landfills and incinerators. According to a report by UNEP titled, "Recycling - from E-Waste to Resources," the amount of e-waste being produced - including mobile phones and computers - could rise by as much as 500 percent over the next decade in some countries, such as India. The United States is the world leader in producing electronic waste, tossing away about 3 million tons each year. China already produces about 2.3 million tons (2010 estimate) domestically, second only to the United States. It is imperative and incumbent on us as a society to reduce our waste from consumer electronics.

Supercapacitors are an emerging energy storage technology whose characteristics make them strong candidates for satisfying those specific functions where (lithium) batteries underperform, ie for those functions requiring a burst of energy.  Supercapacitors can deliver a considerable amount of energy at high power, making them suitable for supplying high power in multifunctional devices where current batteries can't provide it without also reducing their total energy capacity. Using biochemical reactions to generate electrochemical potential promises to reduce the costs of production and size compared to current commercially available supercapacitors. Recent discoveries have shown that we can harness cellular energy production for electrocatalysis in electrochemical energy conversion devices. Biological super capacitors are similar to traditional supercapacitors in that they are energy conversion devices that convert the chemical energy of a fuel into electricity. However, biological super capacitors perform energy conversion through the use of biological catalysts between the electrodes.

We have an innovative approach to reducing this waste and lessening the impact of energy production and storage for electronic devices; by harnessing the power of natural cellular energy production. 32ATPs is seeking to develop biological supercapacitors to increase “green” energy storage for electronic devices including; consumer products, defense, and medical devices.

The goals of our current research and development project are threefold.

1) Can we use mitochondrial energy production in a super-capacitor the way we have in bio-batteries?

2) How will we maximize charge capacity and rate capability in a biological super capacitor?

3) Can we increase the energy storage of a super capacitor to that of a battery?

Previous work performed in my academic collaborator’s lab (Dr. Shelley Minteer, University of Utah) has shown that pyruvate, fatty acids and amino acids, can all be used as fuel for mitochondria in a bio-battery. Mitochondria cannot directly use sugar themselves, because they do not contain the enzymes for the glycolytic pathway. Deep oxidation of simple fuels (the complete conversion of pyruvate to CO2) has been shown AND the good news is that this results in high energy density, and high current and power densities. This previous work also indicates that there are two pathways that can be used to transfer electrons to the electrode, "mediated electron transfer (MET)" and "direct electron transfer (DET)". During DET, mitochondria transfer electrons directly to the electrode surface. In MET, small molecules or polymeric redox mediators are needed to transfer electrons from the mitochondria to the electrode (biological co-factors such as FAD/NAD). Lastly, in a mitochondrial biofuel cell, for instance, a variety of amino acid fuel types have been experimentally measured for open circuit potential, current density, and maximum power density. it has been shown that the highest performing amino acid is cysteine with 100mM of fuel gives 185plus/minus 39uA CM-2 current density and 10.3 plus/minus 1.4 uW cm-2 power density.

We very much need to test these observations both in a supercapacitor and to try to power a consumer device. Current examples of commercial applications of thin devices, with multiple power hungry functionalities, that use energy quite efficiently include the recently launched Huawei Ascend P6 (only 6.18mm thick) and the new iPad Air, which is the thinnest (7.5mm) and lightest (0.470g) version of Apple's flagship tablet - only possible because it comes with a reduced battery capacity. Tellingly, the Air comes with two cell, 32.9Wh battery compared to the previous iPad's three cell, 42.5Wh unit.

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