Rubber is expected to replace traditional materials to become the key material for the next generation of solid -state batteries

In order for electric vehicles (EVs) to go mainstream, they need cost-effective, safer and longer-lasting batteries that don't explode or harm the environment during use. Researchers at Georgia Institute of Technology may have found a promising alternative to conventional lithium-ion batteries: rubber.

Elastomers, or synthetic rubber, are widely used in consumer products and advanced technologies such as wearable electronics and soft robots due to their superior mechanical properties. The researchers found that when the material is formulated into a 3D structure, it acts as a superhighway for fast lithium ion transport, with superior mechanical toughness that allows batteries to charge longer and go farther. The research was carried out in collaboration with the Korea Advanced Institute of Science and Technology and is published in the journal Nature.

In a conventional lithium-ion battery, the ions are moved by a liquid electrolyte. However, such batteries are inherently unstable: even the slightest damage can leak into electrolytes, leading to an explosion or fire. Safety concerns have forced the industry to focus on solid-state batteries, which can be made using inorganic ceramic materials or organic polymers.
"Most industries are focused on building inorganic solid electrolytes. But they are hard to make, expensive and not environmentally friendly, "says Seung Woo Lee, an associate professor at the George W. Woodruff School of Mechanical Engineering who was part of a research team that found a rubber-based organic polymer superior to other materials. Solid polymer electrolytes continue to attract great interest because of their low manufacturing cost, non-toxic and soft properties. However, conventional polymer electrolytes do not have sufficient ionic conductivity and mechanical stability to ensure reliable operation of solid state batteries.
The novel 3d design brings a leap in energy density and performance
Georgia Tech engineers used rubber electrolytes to solve common problems (slow lithium ion transport and poor mechanical properties). The key breakthrough was to allow materials to form three-dimensional (3D) interconnected plastic crystalline phases in a rugged rubber matrix. This unique structure brings high ionic conductivity, excellent mechanical properties and electrochemical stability.
The rubber electrolyte can be made at low temperatures using a simple polymerization process that produces a firm and smooth interface on the electrode surface. These unique properties of the rubber electrolyte prevent the growth of lithium dendrites and allow faster movement of ions, enabling solid state batteries to operate reliably even at room temperature.
Rubber, used everywhere for its high mechanical properties, will enable us to make cheaper, more reliable and safer batteries. Higher ion conductivity means you can move more ions at the same time, and by increasing the specific energy and energy density of these batteries, you can increase the range of the electric vehicle.

The researchers are now working on ways to improve the battery's performance, increasing its cycle time and reducing charging time through better ionic conductivity. So far, their efforts have resulted in two improvements in battery performance/cycle time.

This work could enhance Georgia's reputation as an innovation hub for electric vehicles. SK Innovation, a global energy and petrochemical company, is funding additional research into electrolyte materials as part of its ongoing collaboration with the Institute to build next-generation solid-state batteries that are safer and more energy-intensive than traditional lithium-ion batteries. SK Innovation recently announced the construction of a new electric vehicle battery plant in Commerce, Georgia, which is expected to produce 21.5 gigawatt hours of lithium-ion batteries a year by 2023.
All-solid-state batteries could greatly improve the mileage and safety of electric vehicles. Fast-growing battery companies, including SK Innovation, see the commercialization of all-solid-state batteries as a game changer for the ev market. Kyounghwan Choi, director of SK Innovation's Next Generation Battery Research Center, said: "There are high hopes for the rapid application and commercialization of all-solid-state batteries through the ongoing project in collaboration with SK Innovation and Professor Seung Woo Lee from Georgia Institute of Technology."