Car manufacturers and energy companies are eager to adopt lithium-sulphur (Li-S) batteries. They promise more energy, faster charging, better safety, and lower costs than lithium-ion batteries.

But a big hurdle has held them back – Li-S cells wear out too quickly.

Researchers at the Norwegian University of Science and Technology (NTNU) believe they may have solved that problem. 

A new coating, developed and patented under the HiSep-II project, could extend battery life fivefold and make these lighter, cheaper packs a serious option for electric cars. 

Li-S batteries degrade fast because of the shuttle effect. When the battery operates, lithium polysulfides form and move between the anode and cathode. That movement causes the battery to lose capacity quickly. 

“This happens because chemical substances, lithium polysulfides (LPS), form when the battery is in operation. The substances move between the electrodes, the positive anode and the negative cathode, in the battery. It is these substances that cause LiS batteries to degrade quickly, lose capacity and have a short lifespan,” said postdoctoral fellow Önder Tekinalp of NTNU’s Department of Chemical Engineering.

Instead of focusing on cathodes or electrolytes like many researchers, Tekinalp’s team looked at the separator.

By adding the HiSep-II coating to the separator wall, they created a smart filter. It blocks harmful chemicals while allowing lithium ions to pass freely.

Longer life, lighter packs

Battery lifespan is often measured in charge cycles. NTNU’s lab results show Li-S cells with HiSep-II can increase cycles from 200 to 1,000. That means a battery life up to five times longer. 

The improvement could significantly impact electric cars. A typical 800-volt battery pack could be made more than 200 kilograms lighter. Less weight means better efficiency and range.

Sulphur, the main component, is also abundant and inexpensive, lowering costs.

“Although HiSep-II has not yet been used in electric cars, we have shown that it can handle the shuttle effect. It has been the major brake on commercial exploitation – until now,” said Tekinalp.

NTNU patented the coating in 2023 and is working with its Technology Transfer Office (TTO) to bring it to market.

Beyond cars: air, sea, and land

The team sees broader applications. “The goal is to scale up the technology and license it to an industrial partner so that it can be used in everything from electric cars to storage of green energy,” said Kristina Nydal, business developer at TTO. 

She said the coating improves safety and could benefit aviation, drones, maritime transport, and large-scale energy storage. “It is also an attractive and cost-effective alternative for storing energy. Especially where longevity and stability are crucial factors,” she said.

The coating process is environmentally friendly and designed for scale. It can also work with today’s lithium-based batteries, adding flexibility.

Challenges remain before commercialisation.

External players must test the technology and confirm performance over time. Industry also needs to prove it can be produced at scale, safely, and profitably. Patent processes add further costs.

NTNU is now seeking license partners to finance testing and commercialisation.

“Many Li-S breakthroughs focus on improving cathode materials or electrolytes. The HiSep-II targets the separator, or filter, alone. It is a simpler, more scalable solution without the use of complex materials,” said Tekinalp.