Engineers create powerful battery ‘fuel’ that stores energy even in low sun, wind

Columbia Engineering researchers have been creating novel battery types aiming to adavnce the way renewable energy is stored.

A team has now developed battery “fuel,” K-Na/S batteries using abundant potassium, sodium, and sulfur to provide a low-cost, high-energy solution for long-duration energy storage.

These batteries achieve 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.

Researchers claim that these batteries are promising for long-term energy storage because they only use materials that are found on Earth and provide 150–250 Wh per kg of energy.

“It’s important that we be able to extend the length of time these batteries can operate, and that we can manufacture them easily and cheaply,” said Yuan Yang, the team’s leader and an associate professor in the Department of Applied Physics and Mathematics at Columbia Engineering, in a statement.

Innovative battery design

Although renewable energy sources, such as solar and wind power, are essential to maintaining our planet, they have a significant drawback in that they don’t always produce electricity when it’s needed.

To fully utilize them, we must find economical and effective ways to store the energy they generate, ensuring that we always have power, even in the absence of the sun or wind.

K-Na/S batteries face two main problems: their low capacity stems from the formation of inactive solid K2S2 and K2S, which obstructs the diffusion process; additionally, their operation necessitates very high temperatures (>250 oC), which requires complex thermal management, raising the process’s cost.

Previous research has struggled with low capacity and solid precipitates, so a novel method to enhance these kinds of batteries has been sought after.

To boost battery performance, Professor Yang’s team developed a new amide-based electrolyte that improves the solubility of compounds like K2S2 and K2S, enhancing ionic movement and reaction rates.

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

Boosting energy reliability

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

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

With higher sulfur concentrations (up to 4M), the battery retains 71 percent of its capacity after 1000 cycles. This system provides specific energies of 150-250 Wh per kg and is low-cost due to the abundance of materials used.

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

Although the group is concentrating on tiny, coin-sized batteries for the time being, they eventually want to scale up this technology to store significant amounts of energy.

Researchers believe that if these new batteries are successful, they may be able to deliver a steady and dependable power supply from renewable sources, even when there isn’t much wind or sun. Right now, the group is focusing on electrolyte composition optimization.

“Making renewable energy 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,” said Professor Yang.

The details of the team’s research were published in the journal Nature Communications .