Polymer Engineering: Creating Batteries that Keep Going

By Cheryl A. Reed

Doctoral graduate Yu “Will” Wang believes that polymer—a ubiquitous material made from hydrocarbons and other elements bonded together—may play the most important role in our daily lives. His undergraduate degree in polymers and desire to earn a doctoral degree in the area is what drew him to travel from China to study in the Materials Science and Engineering program at Washington State University.

Natural polymers are things like tortoise shells and antlers, whereas manmade polymers, which are ever-present in our daily lives, are things like plastic, rubber, and synthetic fabrics like rayon. Polymers have increasingly taken the place of natural materials, and the polymer industry is one of the fastest growing in the world. Engineers interested in producing new polymer materials are constantly searching for ways to manipulate the molecular structure of the polymer by introducing fillers, reinforcements, and additives to expand its uses and possibilities.

“The possibilities for applications of new polymers is immense,” said Will, who has created a gum-like electrolyte for use in high-performance lithium batteries. Will works in WSU researcher Katie Zhong’s laboratory. The material, which looks like black tar, can significantly extend the life of lithium batteries, and has gained global attention. An article in the Advanced Energy Materials journal in December 2013 about the electrolyte says that rechargeable lithium ion batteries are expected to dominate the marketplace for the foreseeable future. Think electric cars, aircraft, and pacemakers—technologies that could benefit from a higher energy and safer battery.

“The material is very special,” said Will, reaching for a jar of wax beads used in the mixture. “Instead of liquid, the electrolyte is a mixture of several components that makes it sticky like gum so that it can adhere well to the other battery components.”

Batteries work by converting chemical energy to electrical energy. There are three components to most batteries: the anode, cathode, and electrolyte. The electrolyte is the chemical medium that facilitates the flow of electrons between the cathode and the anode. Put simply, during a discharge of electricity, the chemicals from the anode and cathode make contact in the electrolyte medium, transforming chemical energy to electrical energy. Over time, the anode and cathode will stop producing electrons, and if the battery is not rechargeable, is disposed.

The electric car industry is one that could benefit from a longer-lasting battery. Some of the newest electric cars will run for about 80 miles with a charge—although some of those miles will be exchanged for cabin heat or air conditioning. The recharge time for electric car batteries ranges from 2 to 8 hours, depending on the outlet. A standard 110 volt outlet could extend recharge time to 16 hours.

“Right now electric cars are not popular because of the limited distance they can travel,” said Will. “Our gum-like electrolyte holds a charge longer than the liquid electrolyte—but we need to redesign the entire battery to maximize the storage capacity for the electrolyte. To store more energy, we will need to store more of the high-capacity material.”

In addition to longevity, safety is another major goal for the new battery electrolyte. The liquid medium in current lithium ion batteries is a strong acid that can leak and create fire or chemical burns. “People believe if we want safety, we need to replace the liquid in the battery,” said Will.

Will’s work with Professor Zhong has attracted attention and publication in Advanced Energy Materials.

Will graduated with is doctoral degree from Washington State University in the summer of 2015 and is now Assistant Research Professor in the School of Mechanical and Materials Engineering. He earned his B.S. and M.S. in Polymer Science and Polymer Processing Engineering at Sichuan University in China.

“The quality of education in the U.S. is best, and Pullman is a beautiful and quiet place for students to study. It is small, but everything you want to do is here,” he said.