Microwaved plastic increases lithium-sulfur battery lifespan

May 09, 2018

WEST LAFAYETTE, Ind. -- Purdue engineers have figured out a way to tackle plastic landfills while also improving batteries - by putting ink-free plastic soaked in sulfur-containing solvent into a microwave, and then into batteries as a carbon scaffold.

Lithium-sulfur batteries have been hailed as the next generation of batteries to replace the current lithium ion variety. Lithium-sulfur batteries are cheaper and more energy-dense than lithium ions, which would be important characteristics in everything from electric vehicles to laptops.

But the knock on lithium-sulfur batteries to this point is that they don't last as long, being usable for about 100 charging cycles.

Purdue researchers have found a way to increase the lifespan in a process that has the added bonus of being a convenient way to recycle plastic. Their process, which was recently published in ACS Applied Materials and Interfaces, shows that putting sulfur-soaked plastic in a microwave, including transparent plastic bags, transforms the material into the ideal substance for increasing the lifespan of the forthcoming batteries to more than 200 charging-discharging cycles.

"No matter how many times you recycle plastic, that plastic stays on the earth," said Vilas Pol, associate professor in Purdue's School of Chemical Engineering. "We've been thinking of ways to get rid of it for a long time, and this is a way to at least add value."

The need to reduce landfills runs parallel to making lithium-sulfur batteries good enough for commercial use.

"Because lithium-sulfur batteries are getting more popular, we want to get a longer life sucked out of them," Pol said.

Low-density polyethylene plastic, which is used for packaging and comprises a big portion of plastic waste, helps address a long-standing issue with lithium-sulfur batteries - a phenomenon called the polysulfide shuttling effect that limits how long a battery can last between charges. Watch a YouTube video explaining this at https://youtu.be/9vgGA4vHaWg.

Lithium-sulfur batteries, as their name suggests, have a lithium and a sulfur. When a current is applied, lithium ions migrate to the sulfur and a chemical reaction takes place to produce lithium sulfide. The byproduct of this reaction, polysulfide, tend to cross back over to the lithium side and prevent the migration of lithium ions to sulfur. This decreases the charge capacity of a battery as well as lifespan.

"The easiest way to block polysulfide is to place a physical barrier between lithium and sulfur," said Patrick Kim, a Purdue postdoc research associate in chemical engineering.

Previous studies had attempted making this barrier out of biomass, such as banana peels and pistachio shells, because the pores in biomass-derived carbon had the potential to catch polysulfide.

"Every material has its own benefit, but biomass is good to keep and can be used for other purposes," Pol said. "Waste plastic is really valueless and burdensome material."

Instead, researchers thought of how plastic might be incorporated into a carbon scaffold to suppress polysulfide shuttling in a battery. Past research had shown that low-density polyethylene plastic yields carbon when combined with sulfonated groups.

The researchers soaked a plastic bag into sulfur-containing solvent and put it in a microwave to cheaply provide the quick boost in temperature needed for transformation into low-density polyethylene. The heat promoted the sulfonation and carbonization of the plastic and induced a higher density of pores for catching polysulfide. The low-density polyethylene plastic could then be made into a carbon scaffold to divide the lithium and sulfur halves of a battery coin cell.

"The plastic-derived carbon from this process includes a sulfonate group with a negative charge, which is also what polysulfide has," Kim said. Sulfonated low-density polyethylene made into a carbon scaffold, therefore, suppressed polysulfide by having a similar chemical structure.

"This is the first step for improving the capacity retention of the battery," Pol said. "The next step is fabricating a bigger-sized battery utilizing this concept."
-end-
This research was funded by the Naval Enterprise Partnership Teaming with Universities for National Excellence Center for Power and Energy Research at Purdue.

ABSTRACT

Toward High-Performance Lithium-Sulfur Batteries: Upcycling of LDPE Plastic into Sulfonated Carbon Scaffold via Microwave-Promoted Sulfonation
Patrick J. Kim, Harif D. Fontecha, Kyungho Kim, Vilas G. Pol
Purdue University, West Lafayette, IN, USA
doi:10.1021/acsami.8b03959

Lithium-sulfur batteries were intensively explored during the last few decades as next-generation batteries owing to their high energy density (2600 Wh kg-1) and effective cost benefit. However, systemic challenges, mainly associated with polysulfide shuttling effect and low Coulombic efficiency, plague the practical utilization of sulfur cathode electrodes in the battery market. To address the aforementioned issues, many approaches have been investigated by tailoring the surface characteristics and porosities of carbon scaffold. In this study, we first present an effective strategy of preparing porous sulfonated carbon (PSC) from low-density polyethylene (LDPE) plastic via microwave-promoted sulfonation. Microwave process not only boosts the sulfonation reaction of LDPE but also induces huge amounts of pores within the sulfonated LDPE plastic. When a PSC layer was utilized as an interlayer in lithium-sulfur batteries, the sulfur cathode delivered an improved capacity of 776 mAh g-1 at 0.5C and an excellent cycle retention of 79% over 200 cycles. These are mainly attributed to two materialistic benefits of PSC: (a) porous structure with high surface area and (b) negatively charged conductive scaffold. These two characteristics not only facilitate the improved electrochemical kinetics but also effectively block the diffusion of polysulfides via Coulomb interaction.

Purdue University

Related Batteries Articles from Brightsurf:

New research says Sodium-ion batteries are a valid alternative to Lithium-ion batteries
A team of scientists including WMG at the University of Warwick combined their knowledge and expertise to assess the current status of the Na-ion technology from materials to cell development, offering a realistic comparison of the key performance indicators for NBs and LIBs.

Fast calculation dials in better batteries
A simpler and more efficient way to predict the performance of batteries will lead to better batteries, according to Rice University engineers.

Building the batteries of cells
A new study, led by Dr. Ruchika Anand and Prof.

Researchers create a roadmap to better multivalent batteries
Lithium-ion batteries power everything from mobile phones to laptop computers and electric vehicles, but demand is growing for less expensive and more readily available alternatives.

New NiMH batteries perform better when made from recycled old NiMH batteries
A new method for recycling old batteries can provide better performing and cheaper rechargeable hydride batteries (NiMH) as shown in a new study by researchers at Stockholm University.

Seeing 'under the hood' in batteries
A high-sensitivity X-ray technique at Berkeley Lab is attracting a growing group of scientists because it provides a deep, precise dive into battery chemistry.

Better, safer batteries
For the first time, researchers who explore the physical and chemical properties of electrical energy storage have found a new way to improve lithium-ion batteries.

New catalyst provides boost to next-generation EV batteries
A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has introduced a new composite catalyst that could efficiently enhance the charg-discharge performances when applied to metal-air batteries (MABs).

New lithium batteries from used cell phones
Research from the University of Cordoba (Spain) and San Luis University (Argentina) was able to reuse graphite from cell phones to manufacture environmentally friendly batteries.

Safe potassium-ion batteries
Australian scientists have developed a nonflammable electrolyte for potassium and potassium-ion batteries, for applications in next-generation energy-storage systems beyond lithium technology.

Read More: Batteries News and Batteries Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.