This Small Business Innovation Research (SBIR) Phase II project aims to develop novel type of porous carbon materials with aligned pores for applications in electrical double-layer capacitors (EDLCs). These devices are serving multiple applications, such as smart electrical grids, hybrid-electric vehicles, energy-efficient industrial equipment and personal electronics. Conventional EDLCs store energy by adsorbing organic electrolyte ions on the internal surface of activated carbon electrodes under the application of electrical potential. They commonly take 10 to 100 seconds to charge or discharge. This charge rate is limited by the diffusion of ions inside the tortuous pores of activated carbons. The growing numbers of pulse-power applications, however, often need current boosts for only 1-10 seconds. These applications, therefore, will utilize a fraction of the energy storage capability of conventional EDLCs, which greatly increases the total weight and cost of the energy storage system, slowing down technology adoption. Herein, we propose an innovative low-cost material synthesis route for the formation of porous carbons with finely controlled microstructure, tunable pore size, high surface area, and, most importantly, aligned micropores for rapid ion transport and high power density. These materials offer a combination of fast charging rate and high specific capacitance.
The broader impact/commercial potential of this project is the contribution to dramatic improvements in EDLC technology and reduction of its cost. EDLCs, unlike secondary batteries, exhibit much higher specific power and demonstrate outstanding cycle life and greatly improved safety. The use of EDLCs in transportation and industrial equipment could lead to a major reduction in energy consumption and greenhouse gas emissions. Their application in electrical grids will make multiple renewable energy technologies, such as wind and solar, more economical. The rate of adoption of this important technology could be significantly enhanced if EDLCs could be produced at a lower cost or if they offered further improved performance. These device characteristics are linked to the cost and properties of activated carbon electrodes. Unfortunately, nearly all EDLC manufacturers rely on the existing manufacturers of activated carbon. The expected improvements in material properties from this Phase II project are expected to have a major impact on the EDLC market size and the EDLC technology adoption.
for General Public Economical production and storage of clean energy has recently become one of the most important research topics. Among electrochemical energy storage devices, supercapacitors offer a unique combination of critical performance characteristics. For example, when compared with batteries, supercapacitors can store more power in a smaller volume and often at a lower cost. These devices may operate efficiently in a large temperature window, could be charged in seconds or less and have a long cycle life even when charged so rapidly. The state of charge in supercapacitors is easy to detect, which is convenient for integrating them into other devices and systems. Such properties are unattainable in Li-ion batteries and other alternative energy storage technologies. The energy storage in pure carbon-based supercapacitors is based on the adsorption of electrolyte ions on the large specific surface area of porous carbons, commonly low cost activated carbon powders. Such carbons, unfortunately, suffer from low reproducibility of their properties and limited ion storage ability. In this project we focused on the development of advanced porous carbon powders for use in supercapacitors with improved and more predictable performance. In the course of this project we have developed and implemented several low-cost scalable synthesis routes for the formation of spherical porous carbon powder with tunable specific surface area, pore volume, pore size distribution and particle size distribution. In contrast to the majority of commercial activated carbons used in supercapacitor applications and derived from various natural precursors (ranging from coal to coconut shells), the developed technology offers higher energy and power storage characteristics. More importantly, physical properties of the produced carbons are significantly more reproducible, controllable and tunable than that achievable in the majority of commercial activated carbons. The spherical shape of the powder is attractive for achieving high rate device performance, particularly for thicker densely packed electrodes. Gradual improvements in the material purity and electrode formulations allowed us to achieve over 100,000 charge-discharge cycles without any visible capacity deterioration. In addition to its use in supercapacitors, the developed porous carbon technology may find use in high power batteries, hybrid energy storage devices, specialized adsorbents for ions, organic molecules and gases, catalyst support and other critical applications requiring the use of high surface materials with high purity, precisely controlled size, microstructure and porosity.
