It’s usually a bad thing to "gum up the works," but in the case of the safety issues confronting lithium ion batteries, maybe gum is the solution.
Washington State University researchers have developed a chewing gum-like battery material that could dramatically improve the safety of lithium ion batteries.
A WSU group led by Katie Zhong, Westinghouse Distinguished Professor in the School of Mechanical and Materials Engineering, recently reported on their work in the journal, Advanced Energy Materials. And they have filed a patent on the substance.
High-performance lithium batteries are widely used in everything from computers to airplanes because they are able to store a large amount of energy in comparison to other types of batteries.
But they do have a serious downside, as companies such as Dell and Boeing have found out. Their biggest potential risk comes from the electrolytes in the battery, which is made of either a liquid or gel in all commercially available rechargeable lithium batteries. Electrolytes are the part of the battery that allow for the movement of ions between the anode and the cathode to create electricity. But if the liquid acid solutions leak, a fire or chemical burn hazard can result.
While commercial battery makers have ways to address these safety concerns, such as adding temperature sensors or flame retardant additives, they “can’t solve the safety problem fundamentally,’’ says Zhong.
So the WSU researcher developed a gum-like lithium battery electrolyte, which works as well as liquid electrolytes at conducting electricity, but doesn’t cause a fire hazard.
According to the university, researchers have studied solid electrolytes to address safety concerns for some time, but they don’t conduct electricity well and it’s difficult to connect them physically to the anode and cathode. Zhong’s group looked for a material that would work as well as liquid and could stay attached to the anode and cathode, “like when you get chewing gum on your shoe,’’ she told her students.
Yu “Will” Wang, a graduate student, designed his electrolyte model specifically with gum in mind. It is twice as sticky as real gum and adheres very well to the other battery components.
The material—technically known as “nanoporous polymer-ceramic composite electrolytes”—is a hybrid of liquid and solid, and contains liquid electrolyte material that is hanging on solid particles of wax or a similar material. Electric current can easily travel through the liquid parts of the electrolyte, WSU says, but the solid particles act as a protective mechanism. If the material gets too hot, the solid melts and stops the electric conduction, preventing a fire hazard.
The electrolyte material is also flexible and lightweight, which could be useful in future flexible electronics because it can be stretched, smashed and twisted, while continuing to conduct electricity nearly as well as liquid electrolytes. In addition, Zhong says the gummy electrolyte should be easy to assemble into current battery designs.
While the researchers have shown good conductivity with their gummy electrolyte, the next step is to begin testing the idea in real batteries. Zhong’s group was part of a larger group of WSU researchers that received support from the Washington Research Foundation last year to equip a battery manufacturing laboratory for building and testing lithium battery materials in commercial sizes. The research groups are also working together to combine their technologies into safer, flexible, low-cost batteries.
Thanks to scientific research, sticking it to lithium batteries could be the solution that adheres for increased safety. But does it come in flavors?
Image: Battery+Zhong via the WSU media transfer site