Why promising battery materials break down when researchers build real cells

A battery material can look impressive in a laboratory and still fail when turned into a working battery. US researchers at Oak Ridge National Laboratory (ORNL) are investigating why, focusing on the manufacturing challenges that can prevent promising solid-state and sulfur-based batteries from delivering their expected performance.

The problem is that a battery is more than the sum of its materials. Even if an electrode or electrolyte performs well on its own, gaps between particles, chemical reactions at interfaces, and mechanical changes during charging can disrupt the movement of ions and electrons.

ORNL’s STAR (Sulfide/Sulfur Translational Advanced Research) Lab aims to uncover these failures before battery technologies reach large-scale manufacturing.

“Our mission is to close the gap between promising battery materials and scalable, manufacturable cell technologies,” Guang Yang, one of the researchers and an electrochemical scientist at ORNL, said in a press release.

From promising materials to working batteries

STAR lab focuses on sulfide-based solid-state batteries and sulfur electrodes, both of which could support higher-energy batteries for drones, robotics, transportation and grid storage.

Solid-state batteries replace the liquid electrolyte found in most commercial lithium-ion batteries with a solid material. While this can reduce leakage and flammability risks, solid electrolytes cannot flow into gaps when battery materials expand or contract.

Maintaining contact between these materials therefore becomes a major engineering challenge. Sulfide electrolytes offer a potential advantage because they can conduct lithium ions rapidly at room temperature.

Their particles can also deform under pressure, helping them pack together and reduce gaps. However, their performance depends on how the complete battery is designed, processed, and operated.

STAR Lab examines electrode formulations, binders, interfaces, pressure, cell designs, and testing conditions to determine how these factors influence performance.

Finding what goes wrong inside the cell

The researchers also looked into Sulfur-based electrodes, which offer high theoretical capacity and could increase the energy stored per unit of battery mass. Sulfur is relatively inexpensive and widely available, including as a byproduct of petroleum refining and natural gas processing.

However, sulfur conducts electrons poorly. To overcome this limitation, manufacturers generally combine it with conductive materials such as carbon. The resulting electrode must maintain connected pathways for both electrons and lithium ions.

This becomes harder as electrodes grow thicker. Practical high-energy sulfur cells typically require around 4–5 milligrams of sulfur per square centimeter (0.0009–0.0011 ounces per square inch) of electrode or more. Increasing the sulfur loading can make ion transport more difficult, increase mechanical stress, and disrupt the connections needed for electrochemical reactions.

To investigate these problems, STAR Lab tests complete cells rather than evaluating materials in isolation. Researchers control variables such as electrode thickness, temperature, charging conditions, and pressure, allowing them to compare results more reliably.

Their evaluation also draws on performance metrics from the United States Advanced Battery Consortium (USABC) and objectives set by DOE programs. The team then uses neutron and X-ray techniques, spectroscopy, microscopy, and electrochemical measurements to identify the causes of performance loss.

At ORNL, instruments include the VENUS neutron imaging facility at the Spallation Neutron Source and the MARS beamline at the High Flux Isotope Reactor, which supports high-resolution imaging and 3D computed tomography. This 3D imaging can help researchers reconstruct internal structures and investigate battery electrode degradation.

Collaborations with SLAC National Accelerator Laboratory and Stanford University provide access to synchrotron X-rays at the Stanford Synchrotron Radiation Lightsource. These techniques help reveal structural and chemical changes inside battery materials and at their interfaces.

Computational models complement the experiments by helping researchers predict how manufacturing choices and material properties might affect performance. The results guide subsequent rounds of cell fabrication and testing.

Testing whether batteries can survive scale-up

STAR Lab’s purpose is to evaluate technologies in a research environment larger than conventional laboratory experiments but smaller than industrial production. This allows researchers and industry partners to identify manufacturing risks before scaling up.

The lab studies both dry and liquid-based processing. Dry manufacturing can reduce exposure to liquids that may damage moisture-sensitive sulfide electrolytes, while liquid-based methods may work more easily with established lithium-ion manufacturing equipment.

“A material that works well in a small laboratory cell may fail when it is processed into a manufacturable electrode, separator or pouch cell,” Yang said.

This is why STAR Lab examines how materials can be formulated and processed, how much pressure cells require, and how to maintain consistent quality during manufacturing. The bigger challenge is not simply finding better battery materials, but ensuring they remain effective when manufacturing and real-world operating conditions enter the equation.