Elastomers, or synthetic rubbers, are widely used in consumer products and advanced technologies such as wearable electronics and soft robotics because of their superior mechanical properties.

Researchers at the Georgia Institute of Technology (Georgia Tech) found that the material, when formulated into a 3D structure, acted as a superhighway for fast lithium-ion transport with superior mechanical toughness, resulting in longer charging batteries that can go farther.

The research, conducted in collaboration with the Korea Advanced Institute of Science and Technology, was published Wednesday in the journal Nature.

A researcher stretches the large-scale rubber material. (Photo: Georgia Tech)

In conventional lithium-ion batteries, ions are moved by a liquid electrolyte. However, the battery is inherently unstable: even the slightest damage can leak into the electrolyte, leading to explosion or fire. The safety issues have forced the industry to look at solid-state batteries, which can be made using inorganic ceramic material or organic polymers.

“Most of the industry is focusing on building inorganic solid-state electrolytes. But they are hard to make, expensive and are not environmentally friendly,” said Seung Woo Lee, associate professor in the George W. Woodruff School of Mechanical Engineering, who is part of a team of researchers who have uncovered a rubber-based organic polymer superior to other materials.

Solid polymer electrolytes continue to attract great interest because of their low manufacturing cost, non-toxicity and soft nature. However, conventional polymer electrolytes do not have sufficient ionic conductivity and mechanical stability for reliable operation of solid-state batteries.

Georgia Tech engineers have solved common problems (slow lithium-ion transport and poor mechanical properties) using the rubber electrolytes. The key breakthrough was allowing the material to form a three-dimensional (3D) interconnected plastic crystal phase within the robust rubber matrix. This unique structure has resulted in high ionic conductivity, superior mechanical properties and electrochemical stability.

Prof. Seung Woo Lee (right) and Michael J. Lee (left) have charged the rubber-material-based all-solid-state battery using galvanostatic techniques. (Photo credit: Georgia Tech)

This rubber electrolyte can be made using a simple polymerization process at low temperature conditions, generating robust and smooth interfaces on the surface of electrodes. These unique characteristics of the rubber electrolytes prevent lithium dendrite growth and allow for faster moving ions, enabling reliable operation of solid-state batteries even at room temperature.

“Higher ionic conductivity means you can move more ions at the same time,” said Michael Lee, a mechanical engineering graduate researcher. “By increasing specific energy and energy density of these batteries, you can increase the mileage of the electric vehicle (EV).”

The researchers are now looking at ways to improve the battery performance by increasing its cycle time and decreasing the charging time through even better ionic conductivity. So far, their efforts have seen a two-time improvement in the battery's performance / cycle time.

Elastomers, or synthetic rubbers, are widely used in consumer products and advanced technologies such as wearable electronics and soft robotics because of their superior mechanical properties.

Researchers at the Georgia Institute of Technology (Georgia Tech) found that the material, when formulated into a 3D structure, acted as a superhighway for fast lithium-ion transport with superior mechanical toughness, resulting in longer charging batteries that can go farther.

The research, conducted in collaboration with the Korea Advanced Institute of Science and Technology, was published Wednesday in the journal Nature.

A researcher stretches the large-scale rubber material. (Photo: Georgia Tech)

In conventional lithium-ion batteries, ions are moved by a liquid electrolyte. However, the battery is inherently unstable: even the slightest damage can leak into the electrolyte, leading to explosion or fire. The safety issues have forced the industry to look at solid-state batteries, which can be made using inorganic ceramic material or organic polymers.

“Most of the industry is focusing on building inorganic solid-state electrolytes. But they are hard to make, expensive and are not environmentally friendly,” said Seung Woo Lee, associate professor in the George W. Woodruff School of Mechanical Engineering, who is part of a team of researchers who have uncovered a rubber-based organic polymer superior to other materials.

Solid polymer electrolytes continue to attract great interest because of their low manufacturing cost, non-toxicity and soft nature. However, conventional polymer electrolytes do not have sufficient ionic conductivity and mechanical stability for reliable operation of solid-state batteries.

Georgia Tech engineers have solved common problems (slow lithium-ion transport and poor mechanical properties) using the rubber electrolytes. The key breakthrough was allowing the material to form a three-dimensional (3D) interconnected plastic crystal phase within the robust rubber matrix. This unique structure has resulted in high ionic conductivity, superior mechanical properties and electrochemical stability.

Prof. Seung Woo Lee (right) and Michael J. Lee (left) have charged the rubber-material-based all-solid-state battery using galvanostatic techniques. (Photo credit: Georgia Tech)

This rubber electrolyte can be made using a simple polymerization process at low temperature conditions, generating robust and smooth interfaces on the surface of electrodes. These unique characteristics of the rubber electrolytes prevent lithium dendrite growth and allow for faster moving ions, enabling reliable operation of solid-state batteries even at room temperature.

“Higher ionic conductivity means you can move more ions at the same time,” said Michael Lee, a mechanical engineering graduate researcher. “By increasing specific energy and energy density of these batteries, you can increase the mileage of the electric vehicle (EV).”

The researchers are now looking at ways to improve the battery performance by increasing its cycle time and decreasing the charging time through even better ionic conductivity. So far, their efforts have seen a two-time improvement in the battery's performance / cycle time.