“Our research can contribute to the development of batteries that store more energy"

Batteries are everywhere. We use them daily, from small button cells to large high‑energy batteries. 

High‑energy batteries are powerful battery packs designed to store and deliver large amounts of energy relative to their weight. They are primarily used in electric vehicles and heavy machinery. 

Such battery packs have high voltage and are based on lithium technology.

Researchers want to gain more insight

Batteries rely on critical metals such as lithium, cobalt, and nickel to maximise energy density. The extraction of these raw materials has significant environmental impacts. 

That's why researchers are working to develop batteries with a long lifespan. 

Many of the processes that determine how well a battery functions and how long it lasts involve ions and electrons. These processes occur on a microscopic level, and researchers still want to gain more insight into them.

“We were especially interested in what happens at the interface between the metal electrode and the liquid electrolyte in high‑energy batteries, one of the oldest questions in this research field. That is where performance loss and degradation begin,” says Jelena Popovic‑Neuber.

An important thin layer

She is a professor of materials science and electrochemistry at the University of Stavanger.

Together with colleagues in the battery technology research group, she has recently published several articles on electrolytes in batteries.

“We study how materials react when electricity flows through them. Alkali metals are promising as battery electrodes, but they are also highly reactive. When they meet electrolytes, they form a thin layer that plays a crucial role in how the battery performs and how quickly it ages,” says Popovic‑Neuber.

She explains that the thin layer is called the solid electrolyte interphase (SEI).

A protector, but also a problem

So, what exactly is the SEI, and why does it matter?

“You can think of the SEI as both a protector and a problem. On one hand, it prevents unwanted reactions between the electrode and the electrolyte. On the other hand, this thin layer adds resistance," says Popovic‑Neuber.

The electrolyte layer can also grow over time, reducing the battery’s efficiency. 

"Understanding how this layer forms and evolves is key to developing batteries with longer lifespans,” she says.

"It's like listening to a large orchestra"

In recent lab experiments, the researchers have used a technique called electrochemical impedance spectroscopy. 

The idea is to send a small signal into the battery to observe how it responds across a range of frequencies. This allows researchers to distinguish between different processes happening inside the battery.

“It’s like listening to a large orchestra and being able to pick out each individual instrument,” she says.

Comparing different metals

The researchers have compared lithium, sodium, and potassium. They have also studied metals such as magnesium and aluminum.

The last two are attractive alternatives to lithium because they are more abundant, more sustainable, and cheaper.

By comparing these metals, researchers can understand how fundamental properties change across metal groups.

“A surprising finding from the latest study was how significant charge transfer is, a process where ions and electrons meet. This is often simplified or overlooked in models, but our experiments showed that charge transfer can contribute substantially to the total resistance in the battery,” Popovic‑Neuber says.

She adds that another interesting finding was how the ions’ ability to move through the electrolyte – called transference number – changes as cells age or are exposed to different temperatures.

Everyday technology

The researchers’ goal is to gain a deeper understanding of the fundamental processes inside a battery. 

This forms the basis for designing better battery materials and better electrolytes.

“Our research can contribute to the development of batteries that store more energy, last longer, and charge faster. In the long term, it supports the development of more sustainable energy storage solutions as part of the green transition,” says Popovic‑Neuber.

She adds that there is still much to explore in the field.

“We are moving toward more complex and powerful energy storage systems, and understanding materials’ interfaces will be crucial,” she says.

References:

Grill et al. Revisiting the Electrochemical Response of Alkali Metals in Contact With Liquid Battery Electrolytes (Abstract), Advanced Energy Materials, 2026. DOI: 10.1002/aenm.202506747

Grill, J. & Popovic-Neuber, J. Bulk and interphase properties of W-doped K3SbS4 solid-state electrolyte (Abstract), Journal of Energy Chemistry, 2025. DOI: 10.1016/j.jechem.2025.07.057

Grill, J. & Popovic-Neuber, J. Long term porosity of solid electrolyte interphase on model silicon anodes with liquid battery electrolytes, Communications Chemistry, 2024. DOI: 10.1038/s42004-024-01381-2

Löw et al. Magnesium and Aluminum in Contact with Liquid Battery Electrolytes: Ion Transport through Interphases and in the Bulk, ACS Materials Letters, 2024. DOI: 10.1021/acsmaterialslett.4c01589

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