Carbon dioxide in the atmosphere is a major driver of global warming. While climate change talks progress on how to reduce carbon dioxide emissions, an interdisciplinary team of scientists has worked out a way to reduce carbon dioxide already existing in the atmosphere.
The focus is on the batteries used by electric automobiles. The researchers found out that the graphite electrodes in the lithium-ion batteries could be replaced with carbon electrodes sourced from atmospheric carbon dioxide.
The laboratory of Cary Pint, assistant professor of mechanical engineering, Vanderbilt University and laboratory of Stuart Licht, professor of chemistry, George Washington University, undertook the research.
The experiment started with the use of a solar thermal electrochemical process (STEP) to convert carbon dioxide into carbon. STEP uses solar energy as the source of the thermal and electrical energy required for the dissolution of the atmospheric carbon dioxide to its constituent elements—carbon and oxygen.
The team then used the carbon generated to create carbon nanotubes/nanofibers. These carbon nanotubes turn out to be flexible, conductive, stable, and stronger than steel.
Going further, the team incorporated these carbon nanotubes into lithium-ion batteries by using them as the positive electrode or anode. In addition to electric car batteries, the innovative lithium-ion battery setup using carbon nanotubes can work effectively in everyday electronic devices.
However, the application of carbon nanotubes in batteries is not an exclusive preserve of lithium-ion batteries. The researchers also demonstrated that they could infuse the nanofibers as positive electrodes in sodium-ion batteries as well. Sodium-ion batteries are low-cost storage solutions currently developed for use in large-scale applications like the electric grid.
Moving on from batteries, other applications for the carbon nanotubes include carbon composites for truck and airplane bodies, strong and lightweight construction materials, and sport equipment and car.
In terms of performance, the carbon nanotubes offer more juice. The researchers found that small defects in the carbon, which STEP can create, could lead to stable storage performance that is over 350 percent above that of sodium-ion batteries using graphite electrodes. Across the board, there was a performance boost. Quicker charging of the battery amplified this boost.
Remarkably, the carbon-nanotube batteries showed no sign of “fatigue” after they were exposed to about 10 weeks of continuous charging and discharging.
According to Pint, as much as 40 percent of the battery could be made out of recycled carbon dioxide depending on the specifications. This estimate excludes the outer protective packaging. However, Pint maintains that a similar process to producing the packaging using a process similar to STEP was possible.
With lithium-ion battery production cost of about $325 per kWh, one kilo of carbon dioxide has an estimated value of $18 as a battery material, 6 times more than when it is converted to methanol and much more when smaller batteries for electronic devices are made.
Also pushing the drive for reduced CO2 emissions, Licht proposed the use of STEP in a natural gas powered electrical generator. The generator would produce electricity, heat, and carbon dioxide. STEP will progress using the carbon dioxide to produce carbon and oxygen.
While the carbon is used in the manufacture of carbon nanotubes, the oxygen is channeled back to the generator to boost the combustion efficiency of the generator. The increased efficiency will balance the electricity consumption of STEP. In the end, the fossil fuel electrical power plant could have zero net carbon dioxide emissions.
The researchers published their findings in the journal ACS Central Science.