This Small Business Innovation Research (SBIR) Phase I Project seeks to solve the problems of limited voltage, energy density, and lifetime in Electric Double Layer Capacitors (EDLCs). These issues have largely lead to the failure of EDLCs to become a significant part of the energy storage landscape. Over the years, many different efforts have focused on developing new carbon materials for EDLCs, including those focused on exotic and expensive materials such as carbon nanotubes, carbide derived carbons and Graphene. None of these have so far succeeded at matching the energy density, lifetime, or voltage range of 15 year old commercial carbon materials. This project will attempt to prove that this is related to functional groups on the carbon surface that, when assembled in an EDLC and charged, are REDOX active to form water in the electrolyte. The objective of the research will be to eliminate these species and other surface functional groups, while maintaining the exceptionally high surface area necessary for high capacitance, through precisely controlled thermal treatment of activated carbon. This will result in dramatic increases in the voltage, energy density, and life of current EDLC products.

The broader impact/commercial potential of this project will involve dramatically expanding the value of ultracapacitors to various applications and enhancing their societal impact. Supercapacitors have failed to meet expectations for market growth largely due to high cost, premature failure, low voltage (matching Li-ion battery voltages requires two devices in series) and low energy density, and have seen minimal technical progress over the last decade. Our technology would increase the energy density, lifetime and voltage to levels that would enable much more widespread adoption in applications currently restricted to batteries alone. Additional societal impact, and directly related commercial advantage, would stem from the fact that this technology could eliminate the requirement for exotic and expensive precursors for carbon production, allowing, for the first time, the use of inexpensive water filtration carbons. The combined lower cost and improved performance would expand EDLCs use in applications like hybrid cars, buses, wind turbine pitch control and grid storage, all of which have tremendous societal impact and where cost is the primary barrier to entry for EDLC manufacturers.

Project Report

Dr. Edward R. Buiel Coulometrics LLC 100 Cherokee Blvd, STE 318 Chattanooga, TN, 37405 NSF Project# 1315040 Project Outcome Report: Coulometrics is a company located in Chattanooga, TN that is currently working on advanced energy storage devices such as supercapacitors and lithium ion batteries. We also provide consulting and engineering services to a wide range of companies developing advanced materials for lead acid batteries, lithium ion batteries, supercapacitors, and integration of energy storage systems. The main objectives of NSF Project #1315040 was the development of a surface modification technique for supercapacitors that would improve life and/or increase cell voltage and hence energy density. Coulometrics was able to demonstrate in Phase I of this project that up to a 2X increase in cell life and an increase in cell voltage from 2.7 to 3.0 V is possible with the process that we have developed. This increase in cell voltage is important because it corresponds to an almost 25% increase in energy density of the cell with minimal increase in cell cost. Coulometrics is currently working with many supercapacitor cell manufactures and activated carbon production companies that could benefit directly from the technology developed under this project. During our Phase II effort, if awarded, Coulometrics will work to rapidly fully validate and commercialize this technology. A pilot surface treatment system will be developed that will have capacity to treat up to 1 ton/month of activated carbon. This system will be designed so that it can easily be scaled up to 10 ton/month. Such a system would be able to support production of up to 400,000 - 350F supercapacitors per month or $30M / year in sales. Coulometrics is currently partnered with supercapacitor manufacturers and activated carbon manufacturing companies. We can produce and sell electrode materials using high performance activated carbon from our process directly to sell manufacturers or license the technology to an activated carbon company to produce the carbon for us. Coulometrics has also determined that the surface modification process can be used to improve the performance of natural graphite to make it suitable for use in high-end lithium ion batteries. Normally, synthetic graphite is used for high-end lithium ion battery applications, such as electric vehicles, due to the high purity and other properties synthetic graphite. When natural graphite was treated using Coulometrics proprietary process, the irreversible capacity was reduced from very high levels > 100 mAh/g, to less than 30 mAh/g which is consistent with synthetic graphite performance. This result is important as it would provide a new high-value market for North American graphite mining companies and also provide the United States with a local supply of anode materials for lithium ion batteries. Currently almost all natural graphite used in lithium ion batteries are sourced from China and synthetic graphite production is expensive and also environmentally unfriendly. The process to mine and treat natural graphite would be far more cost effective and environmentally benign.

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