Powerful battery ‘fuel’ developed by Columbia engineers is cheap and durable

Researchers at Columbia Engineering have developed a novel type of battery that aims to improve the way we store renewable energy.

The team has now developed a ‘fuel’ for the batteries – K-Na/S batteries, which use large amounts of potassium, sodium and sulfur, providing a cheap and high-energy solution for long-term energy storage.

These batteries reach near maximum capacity (1655 mAh/g sulfur) at 75°C with 1M sulfur. At 4M sulfur they deliver 830 mAh/g at 2mA/cm² and retain 71 percent capacity after 1000 cycles.

Scientists say these batteries show promise for long-term energy storage because they use only materials found on Earth and deliver 150-250 Wh of energy per kg.

“It’s important that we can extend the operating time of these batteries and that we can make them easily and cheaply,” Yuan Yang, team leader and assistant professor in the Department of Applied Physics and Mathematics at Columbia Engineering, said in a statement.

Innovative battery design

While renewable energy sources like solar and wind are essential to preserving our planet, they have a major drawback in that they do not always produce electricity when it is needed.

To fully utilize them, we need to find economical and efficient ways to store the energy they generate, ensuring constant access to electricity even when there is no sun or wind.

K-Na/S batteries face two main problems: their low capacity is due to the formation of inactive solid K2S2 and K2S species, which hinders the diffusion process; furthermore, their operation requires very high temperatures (>250 oC), which requires complex thermal management, increasing the process costs.

In previous studies, low capacity and solid deposition were problems, so they started looking for a new method to improve this type of battery.

To improve battery performance, Professor Yang’s team developed a new amide-based electrolyte that improves the solubility of compounds such as K2S2 and K2S, increasing ion movement and reaction speed.

This design is used in K-Na/S batteries, which offer higher voltage (~2.1 V) than traditional Na/S and K/S batteries and operate at lower temperatures (50-100°C instead of 150°C).

Increasing energy reliability

The team’s experiments showed that the electrolyte’s ability to dissolve K2S2 and K2S can improve the energy and power density of K/S batteries operating at intermediate temperatures.

By using a mixture of acetamide and ε-caprolactam, which can dissolve up to 1.43 M K2S at 75°C, the battery achieves almost full discharge capacity (1655 mAh per gram of sulfur) at 75°C.

At higher sulfur concentrations (up to 4M), the battery retains 71 percent of its capacity after 1,000 cycles. This system provides a specific energy of 150-250 Wh per kg and is inexpensive because of the abundance of materials used.

“Our approach achieves near-theoretical discharge capacities and extended cycle life. This is very exciting for the field of mid-temperature K/S batteries,” said Zhenghao Yang, co-author of the first study and a PhD student with Professor Yang.

While the group is focusing on tiny, coin-sized batteries for now, it wants to eventually expand the technology to store significant amounts of energy.

The researchers believe that if these new batteries are successful, they could be able to provide consistent, reliable power from renewable sources, even when there isn’t much wind or sun. The group is currently focusing on optimizing the electrolyte composition.

“Making renewable energy sources more reliable will help stabilize our energy grids, reduce our dependence on fossil fuels and support a more sustainable energy future for all of us,” Professor Yang said.

Details of the team’s research were published in the journal Nature communication.