For the first time, researchers at Helmholtz-Zentrum Berlin (HZB) have captured real-time images of how liquid electrolytes move inside working lithium-sulfur (Li-S) pouch cells with lean electrolyte, using operando neutron tomography.

The study provides critical insights into why these high-energy-density batteries, which promise more than twice the energy of conventional lithium-ion cells, often degrade quickly and fail. With potential energy densities exceeding 700 Wh/kg, Li-S batteries are highly attractive for aerospace, robotics, and long-range electric vehicles. Sulfur is also cheap and abundant, making it a sustainable alternative to cobalt and nickel.

Figure 1. Electrolytes in Lithium-Sulfur Batteries.

The challenge of lean electrolytes

Maximizing energy density requires reducing inactive materials like the electrolyte. But using less electrolyte makes it harder to fully wet electrodes, disrupting electrochemical reactions and accelerating aging.

“Key questions are how electrolytes spread across electrodes, penetrate pores, and distribute within Li-S pouch cells — and how these processes affect performance,” explains Prof. Dr. Yan Lu, who led the study. Observing this wetting inside sealed batteries has been nearly impossible without damaging the cells. Figure 1 shows Electrolytes in Lithium-Sulfur Batteries.

To overcome this, the team built multilayer pouch cells under industry-relevant conditions and tracked them during charge-discharge cycles using neutron tomography at the Institut Laue-Langevin in Grenoble.

Electrolyte dynamics revealed

Neutron imaging, highly sensitive to light elements like lithium and hydrogen, allowed the researchers to visualize how electrolyte distribution shifted during operation [1]. They observed unwetted regions forming during rest, with short pauses improving wetting but longer rests showing little effect. By contrast, charging and discharging cycles enhanced electrolyte homogeneity and promoted sulfur activation, improving capacity.

The team also identified unique “breathing” wetting patterns — periodic changes linked to the dissolution and precipitation of sulfur compounds — a phenomenon distinct from conventional lithium-ion chemistry.

“These findings offer vital clues to why Li-S batteries age so quickly and how we can extend their lifespan,” says Yan Lu. The results, published in Nature Communications, demonstrate a powerful, non-destructive method for studying electrolyte behavior in real time.

This breakthrough could guide the design of lighter, longer-lasting Li-S batteries and accelerate their path toward practical use in next-generation energy storage.

References:

1. https://interestingengineering.com/energy/electrolyte-flow-lithium-sulfur-battery-imaging

Cite this article:

Keerthana S (2025), Scientists Capture First-Ever Real-Time Look at Electrolytes in Lithium-Sulfur Batteries, AnaTechMaz, pp.251