Biodegradeable Supercapacitors

 

The continued research and development of greener, cheaper, lighter, more efficientenergy storage is required to keep pace with the currentand future functionalities of consumer electronics and portable devices. The forecast of the consumer electronics marketprojects that new, emerging product categories will grow by 107 percentyear-over-year in 2014. These new technology categories, including 3D printers,Bluetooth wireless speakers, convertible PCs, health and fitness devices, smartwatches and Ultra HD television displays, are cumulatively expected tocontribute more than $6 billion to the overall CE industry in 2014. While theseemerging product categories represent less than three percent of the entire CEindustry, 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 tosatisfy an ever-increasing number of variable power demands. The United States is the world leader inproducing electronic waste.

Batteries underperform in today’s smart devices and are theprimary limitation for future development of new features. Furthermore, allelectronic scrap components, including batteries, can contain environmentalcontaminants such as lead, cadmium, beryllium, or brominated flame retardants.Electrical waste not only contains hazardous, but also valuable and scarcematerials. Up to 60 different elements can be found in complex electronics. Anestimated 50 million tons of E-waste are produced each year. For example, theUSA discards 30 million computers and Europe, 100 million phones each year. TheEnvironmental Protection Agency estimates that only 15-20% of e-waste isrecycled, the rest of these electronics go directly into landfills andincinerators. According to a report by UNEP titled, "Recycling - fromE-Waste to Resources," the amount of e-waste being produced - includingmobile phones and computers - could rise by as much as 500 percent over the nextdecade in some countries, such as India. The United States is the world leaderin 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 asociety to reduce our waste from consumer electronics.

Supercapacitors are an emerging energy storage technology whosecharacteristics make them strong candidates for satisfying those specificfunctions where (lithium) batteries underperform, ie for those functionsrequiring a burst of energy.  Supercapacitors can deliver a considerableamount of energy at high power, making them suitable for supplying high powerin multifunctional devices where current batteries can't provide it withoutalso reducing their total energy capacity. Using biochemical reactions togenerate electrochemical potential promises to reduce the costs of productionand size compared to current commercially available supercapacitors. Recentdiscoveries have shown that we can harness cellular energy production forelectrocatalysis in electrochemical energy conversion devices. Biological supercapacitors are similar to traditional supercapacitors in that they are energyconversion devices that convert the chemical energy of a fuel into electricity.However, biological super capacitors perform energy conversion through the useof biological catalysts between the electrodes.

We have an innovative approach to reducingthis waste and lessening the impact of energy production and storage forelectronic devices; by harnessing the power of natural cellular energyproduction. 32ATPs isseeking to develop biological supercapacitors to increase “green” energystorage for electronic devices including; consumer products, defense, andmedical devices.

The goals ofour current research and development project are threefold.

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

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

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

Previouswork performed in my academic collaborator’s lab (Dr.Shelley Minteer, University of Utah) has shown that pyruvate, fatty acids and amino acids, canall be used as fuel for mitochondria in a bio-battery. Mitochondria cannot directly use sugar themselves, because they donot contain the enzymes for the glycolytic pathway. Deep oxidation of simplefuels (the complete conversion of pyruvate to CO2) has been shown AND the goodnews is that this results in high energy density, and high current and powerdensities. This previous work also indicates that there are two pathways thatcan be used to transfer electrons to the electrode, "mediated electrontransfer (MET)" and "direct electron transfer (DET)". DuringDET, mitochondria transfer electrons directly to the electrode surface. In MET,small molecules or polymeric redox mediators are needed to transfer electronsfrom the mitochondria to the electrode (biological co-factors such as FAD/NAD).Lastly, in a mitochondrial biofuel cell, for instance, a variety ofamino acid fuel types have been experimentally measured for open circuitpotential, current density, and maximum power density. it has been shown thatthe highest performing amino acid is cysteine with 100mM of fuel gives185plus/minus 39uA CM-2 current density and 10.3 plus/minus 1.4 uW cm-2 powerdensity.

We very much need to test theseobservations both in a supercapacitor and to try to power a consumer device.Current examples of commercial applications of thin devices, with multiplepower hungry functionalities, that use energy quite efficiently include therecently 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 flagshiptablet - only possible because it comes with a reduced battery capacity.Tellingly, the Air comes with two cell, 32.9Wh battery compared to the previousiPad's three cell, 42.5Wh unit.