Wayne State's Arava Research Group is working on making phones, laptops and car batteries more sustainable and longer-lasting
Wayne State University College of Engineering faculty members have demonstrated a new configuration of Lithium-Sulfur (Li/S) battery that is a more powerful and less expensive alternative to commercially available lithium-ion batteries.
The group recently published its findings in Nature's online, open-access journal, Scientific Reports. Titled, "Electrocatalysis of Lithium Polysulfides: Current Collectors as Electrodes in Li/S Battery Configuration," the paper outlines the need for and innovation and design of the group's version of an Li/S battery that addresses not only poor cycle-life issues, but also enhances other areas, such as low sulfur utilization and poor reaction kinetics that impede Li/S battery commercialization.
The primary advantages of the Li/S battery is that it can theoretically store five times more energy than the lithium-ion batteries that currently power several electric cars, including the Tesla S model. Though Li/S batteries have the potential to be the next generation of batteries, they have languished in research and development due to a host of practical limitations and bottlenecks that hinder full-scale development.
The typical Li/S battery configuration consists of two current collectors, lithium anode, carbon-sulfur cathode and electrolyte. During discharge, the sulfur cathode converts to polysulfides and dissolves in the electrolyte to form a barrier layer on the lithium anode. This chemical degradation depletes the active sulfur in the cathode, leading to rapid performance loss, and shortening the cycle life to the Li/S system dramatically.
The past decade has seen intense research efforts to stabilize polysulfide shuttle processes by entrapping them in the cathode using various micro-, meso- and nanoporous carbons; however, low sulfur loading in these carbons and their poor adsorption toward polysulfides has yielded limited success.
"We have been trying to tackle these issues through unconventional approaches and looked back at some of the old chemistries relevant to the field. Research attempts on utilizing catalysis in aqueous sulfur batteries from almost four decades ago grabbed our attention" said Leela Mohana Reddy Arava, assistant professor of mechanical engineering. "We were very curious to know how a catalyst influences the present, non-aqueous Li/S chemistry.
"Our novel electrode configuration helps to overcome the major drawback of short cycle life caused due to migration of dissolved polysulfides towards Li-anode in Li/S system," Arava continued. "Such batteries could provide an opportunity to develop electric vehicles that match the power, range and cost of combustion engines."
Using a systematic approach, the authors have screened several known metals - such as platinum, gold and nickel - as potential catalysts for Li/S batteries, and validated the mechanism by varying some of the basic catalysis principles. Achieving stable performance over extended cycles without compromising on storage capacity makes the group's approach unique. The carefully engineered porous collectors have been found to be key to stabilizing the polysulphides shuttle process.
"We have completely eliminated the use of carbon and its complex electrode processing of loading sulfur, handling solvents, and using binders and additives," said Arava. "We utilize current collectors - one of the key components of a battery - to trap polysulfides and catalyze Li/S electrochemical reaction.
"This is the simplest configuration that a battery can have. By flooding two metal foils, such as nickel and lithium, with catholyte [a solution form of sulfur cathode in the electrolyte], you end up having a high-power energy-storage device. The whole battery manufacturing process becomes inexpensive, as we don't need any industrial process to make the cathode," said Ganguli Babu, lead author and postdoctoral fellow in the Arava group
"We are surprised to see a working battery without any traditional carbon cathode," said Khalid Ababtain, co-author and graduate student in the Arava group. "We believe there is a lot of room for further improvement in performance by choosing cheaper catalytic collectors, varying its morphology and concentration of the catholyte."
The group is far from finished. Its next step is eliminating the lithium metal on the other side of the battery. This is needed because lithium has severe safety issues and is a finite resource. Preliminary findings of the group's research for this step will be presented by undergraduate student Jaron Lloyd Bentley (pictured to the left) in the upcoming Electro Chemical Society (ECS) Meeting in Chicago. The ultimate goal for the group is to construct better-performing, more sustainable and safer batteries to help power next-generation technologies.
"This research project is a good example of interdisciplinary collaboration. The group's combined expertise in Material science, Mechanical and Chemical Engineering served to augment our skill base thereby enabling us to develop a novel approach for the next generation of battery systems," says co-author Simon Ng, Associate Dean for Research and Graduate Studies.
Access the paper here http://www.nature.com/srep/2015/150303/srep08763/full/srep08763.html
Access Bentley's work here https://ecs.confex.com/ecs/227/webprogram/Paper51089.html
To learn about or contact the Arava Research Group, visit blogs.wayne.edu/arava/.
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Wayne State University is a premier urban research institution of higher education offering 370 academic programs through 13 schools and colleges to nearly 28,000 students. For more information about engineering at Wayne State University, visit engineering.wayne.edu.