A lithium battery could use greenhouse gases even before it enters the atmosphere – ScienceDaily

Although based on initial research and far from commercial deployment, the new battery formulation could open new avenues to adapt electrochemical carbon dioxide conversion reactions, which could contribute to reducing greenhouse gas emissions in the future. l & # 39; atmosphere.

The battery is made of lithium metal, carbon and an electrolyte designed by the researchers. The results are described today in the journal Joulein a paper by Assistant Professor of Mechanical Engineering Betar Gallant, PhD student Aliza Khurram and postdoc Mingfu He.

Currently, power plants with carbon capture systems typically use up to 30% of the electricity that they generate solely to fuel the capture, release and storage of carbon dioxide. Anything that can reduce the cost of this capture process, or that can result in a valuable end product, could significantly change the economics of these systems, according to the researchers.

However, "carbon dioxide is not very reactive," says Gallant, so "trying to find new ways of reaction is important." Generally, the only way to obtain carbon dioxide for it to have significant activity under electrochemical conditions is to use large amounts of energy in the form of high voltages, which can be a costly and inefficient process. Ideally, the gas would undergo reactions that would produce something worthwhile, such as a useful chemical or a fuel. However, the electrochemical conversion efforts, generally carried out in water, remain hampered by high energy inputs and low selectivity of the chemicals produced.

Gallant and his colleagues, whose expertise is related to non-aqueous (not aqueous-based) electrochemical reactions, such as those underlying lithium batteries, questioned whether the capture chemistry of carbon could electrolytes loaded with dioxide – one of the three essential parts of a battery – where the captured gas could then be used during the discharge of the battery to provide power output.

This approach is different from the release of carbon dioxide in the gas phase for long-term storage, as is now the case for carbon capture and sequestration, or CCS. This field generally examines ways of capturing carbon dioxide from a plant through a process of chemical absorption, then storing it in underground formations or chemically transforming it into a fuel or chemical feedstock.

Instead, this team has developed a new approach that could potentially be used directly in the waste stream of power plants to manufacture materials for one of the major components of a battery.

While the development of lithium-carbon dioxide batteries, which use gas as a reagent during discharge, is attracting increasing interest, the low reactivity of carbon dioxide generally requires the use of metal catalysts. Not only are they expensive, but their function remains poorly understood and reactions are difficult to control.

By incorporating the gas in the liquid state, Gallant and his colleagues found a way to achieve the electrochemical conversion of carbon dioxide using only a carbon electrode. The key is to preactivate carbon dioxide by incorporating it into an amine solution.

"What we showed for the first time is that this technique activates carbon dioxide for easier electrochemistry," says Gallant. "These two chemistries – aqueous amines and non-aqueous battery electrolytes – are not usually used together, but their combination confers new and interesting behaviors that can increase the discharge voltage and enable a sustainable conversion of carbon dioxide."

Through a series of experiments, they showed that this approach worked and that they could produce a lithium-carbon dioxide battery with a competitive voltage and capacity compared to those of the lithium-gas batteries the more modern. In addition, the amine acts as a molecular promoter that is not consumed in the reaction.

The key was to develop the right electrolyte system, explains Khurram. In this initial proof-of-principle study, they decided to use a non-aqueous electrolyte as this would limit the available reaction pathways and thus facilitate the characterization of the reaction and its viability. The amino material they chose is currently used for CCS applications, but it has not been applied to batteries yet.

This early system has not yet been optimized and will require further development, according to the researchers. On the one hand, the life of the battery is limited to 10 charge-discharge cycles. Further research is therefore needed to improve the reloading and prevent degradation of the cell components. "Lithium-carbon dioxide batteries are in the coming years" as a viable product, says Gallant, as this research only covers one of the many advances needed to make them practical.

But the concept offers great potential, according to Gallant. Carbon sequestration is widely considered essential for achieving the global targets for reducing greenhouse gas emissions, but there are still no proven methods to eliminate or use all of the resulting carbon dioxide. Underground geological disposal is still the main competitor, but this approach remains somewhat unproven and may be limited in its capacity. It also requires additional energy for drilling and pumping.

Researchers are also exploring the possibility of developing a continuous process version, which would use a constant flow of carbon dioxide under pressure with the amino material, rather than a pre-loaded supply of material, allowing it to provide power constant. output as long as the battery is supplied with carbon dioxide. In the end, they hope to make it an integrated system that will both capture carbon dioxide from a plant's emissions stream and convert it into an electrochemical material that could then be used in batteries. "It's a way to sequester it as a useful product," explains Gallant.