Famously an insulator, rubber might not seem like a great candidate for an electrolyte material in a battery, but researchers at Georgia Tech have developed a new rubbery material with a high conductivity. This elastomer electrolyte could make for safer electric vehicle batteries with longer range.
Lithium-ion batteries have ushered in revolutions in many kinds of technology, from smartphones to electric vehicles. But there’s always the risk of fire or explosion when the battery is damaged or overheated, thanks to the liquid electrolyte that ferries lithium ions between the electrodes.
Solid-state electrolytes can help reduce that risk, but they bring their own problems. Often made of ceramic materials, they can be somewhat fragile, and the interface between them and the electrodes can be patchy, reducing the conductivity of ions through the battery.
The Georgia Tech researchers say their new elastomer electrolyte takes steps towards solving both these problems. The rubbery material can bounce back from bumps to the battery, and maintains a smooth connection with the electrodes. That keeps its conductivity high but also prevents the growth of lithium dendrites, which are often the first step towards failure of a battery.
The rubber itself isn’t the part doing the conducting though. It’s embedded with conductive plastic crystals of a material called succinonitrile, while the elastomer provides a 3D scaffold to give the electrolyte its shape and stability.
In tests, lithium metal batteries made with the new electrolyte were able to operate at a voltage of 4.5 V at room temperature, with a capacity of 93 mAh g-1 and almost no capacity fading over 1,000 cycles. There was also no sign of dendrites forming after 100 cycles.
There’s still room for improvement of course, and the team is investigating ways to boost the cycle time and ionic conductivity. The team says this could eventually lead to safer and longer lasting batteries for electric vehicles.
“Higher ionic conductivity means you can move more ions at the same time,” says Michael Lee, lead author of the study. “By increasing specific energy and energy density of these batteries, you can increase the mileage of the EV.”
The research was published in the journal Nature.
Source: Georgia Tech