Rethinking Battery Design Assumptions

New Understanding of Cathode Cracking in Lithium-Ion Batteries

Improving battery power density is a key driver for the adoption of EVs over internal combustion engines. Consumer safety is another major concern, though the public perception of fire risk often exceeds the reality.

Durability is equally critical. Buyers demand batteries that last over a decade—ideally outliving the vehicle itself—to preserve residual value and avoid costly replacements.

“Electrification of society needs everyone’s contribution. If people don’t trust batteries to be safe and long-lasting, they won’t choose to use them.”

Khalil Amine – Argonne Distinguished Fellow

To address these criteria, the industry is shifting from polycrystalline Ni-rich materials (PC-NMC) to single-crystal Ni-rich layered oxides (SC-NMC).

This transition aims to mitigate the nanoscopic strains that cause cathode cracking over time. Until now, the design of monocrystalline (single-crystal) cathodes followed the assumptions previously used for polycrystalline cathodes.

However, researchers at Argonne National Laboratory, Brookhaven National Laboratory, and the University of Chicago have discovered that these two cathode types crack in fundamentally different ways, paving the way for new optimization strategies.

They published their findings in Nature Nanotechnology¹, titled “Nanoscopic strain evolution in single-crystal battery positive electrodes”.

Why Cathode Cracking Is a Primary Failure Mechanism

Polycrystalline Cracking

In a polycrystalline cathode, the material is comprised of multiple nanoscopic crystals. As the battery charges and discharges, these particles expand and contract.

This repeated movement can widen the grain boundaries that separate the polycrystals, creating cracks. If a crack becomes too wide, electrolyte can infiltrate the particle—similar to how water freezing and thawing creates potholes in city streets.

Source: Nature

When this expansion exceeds elastic limits, the cathode cracks. At worst, this can lead to thermal runaway and fire. More commonly, it reduces the battery’s charge capacity over time, leading to performance degradation.

“Typically, it will suffer about five to 10% volume expansion or shrinkage. Once an expansion or shrinkage exceeds the elastic limits, it will lead to particle cracking.”

Jing Wang – Postdoctoral researcher at Argonne National Laboratory

Because monocrystalline cathodes lack boundaries between crystal grains, they do not suffer from this specific failure mode. However, battery degradation persists.

Monocrystalline Cathodes’ Unique Features

To investigate this, the researchers utilized multi-scale synchrotron X-ray techniques and a high-resolution transmission electron microscope.

Source: Nature

In a polycrystalline cathode, cobalt helps moderate Li/Ni disorder (nickel ions migrating into lithium layers) but is also a known contributor to cracking. Traditionally, manganese is added to balance this issue.

The Argonne researchers found that in monocrystalline cathodes, the opposite is true: manganese was more mechanically detrimental, while cobalt actually helped extend battery life.

“When people try to transition to single-crystal cathodes, they have been following similar design principles as the polycrystal ones.

Our work identifies that the major degradation mechanism of the single-crystal particles is different from the polycrystal ones, which leads to the different composition requirements.”

Jing Wang – Postdoctoral researcher at Argonne National Laboratory

The study reveals that reaction heterogeneity causes strain within individual crystals, rather than between them. Different regions of the crystal react at varying rates, creating internal stress that leads to cracking.

Source: Nature

How This Discovery Could Improve Next-Generation Batteries

Cobalt is more expensive than nickel or manganese and carries ethical production concerns, driving the industry’s push to reduce its use.

“By identifying this previously underappreciated mechanism, this work establishes a direct link between material composition and degradation pathways, providing deeper insight into the origins of performance decay in these materials.”

Tongchao Liu – Chemist at Argonne National Laboratory

The next step is applying these findings to identify cobalt-free materials that reduce cracking risks while maintaining cost efficiency.

Conclusion

Improving the cathode is a vital step for enhancing lithium battery performance. This is particularly crucial for newer, anode-free designs where cathode efficiency is paramount.

This innovation provides a new theoretical framework for optimizing monocrystalline cathode designs. Ideally, it will lead to a cobalt-free alternative that significantly reduces cracking risks and lowers costs.

Such advancements are particularly valuable for cathode-agnostic battery developers like QuantumScape. Since their anode-free platform supports various cathode chemistries, they can rapidly integrate these resilient single-crystal designs to extend battery life without redesigning their core solid-state technology.

Battery Company

QuantumScape

A large segment of consumers remains doubtful of the range and recharging speeds of most EV models. The risk of fire from traditional lithium-ion batteries is also a concern.

Solid-state batteries offer an ideal solution by replacing the liquid electrolyte with a solid one, thereby eliminating fire risks and massively increasing energy density.

QuantumScape is particularly innovative for its anode-free design. This allows it to integrate multiple cathode materials, positioning the company to benefit from future improvements in cathode manufacturing and design.

Source: QuantumScape

After years of slow progress in labs, solid-state batteries are finally moving from promising prototypes to mass production and integration into commercial vehicles.

A key milestone was reached in 2025 when QuantumScape debuted its battery in the Ducati V21L electric motorcycle, a result of its partnership with Volkswagen.

Source: QuantumScape

QuantumScape’s design is significantly superior to lithium-ion batteries in almost all metrics:

• It can charge in just 15 minutes (10-80% at 45 ºC).
• The separator replacing the liquid electrolyte is nonflammable and noncombustible.
• Its battery cells’ energy density is 844 Wh/L and 301 Wh/kg.
• For reference, Tesla’s 4680 cells stand at 643 Wh/L and 241 Wh/kg, and BYD’s blade cells at ~375 Wh/L and 160 Wh/kg.

Volkswagen’s battery subsidiary, PowerCo, will provide QuantumScape up to $131 million in new payments over the next two years upon achieving certain milestones, demonstrating the group’s commitment to solid-state technology.

(You can read more about QuantumScape in our dedicated investment report.)

Latest QuantumScape (QS) Stock News and Developments

Study Referenced

^{1. Wang, J., Liu, T., Huang, W. et al. Nanoscopic strain evolution in single-crystal battery positive electrodes. Nat. Nanotechnol. (2025). https://doi.org/10.1038/s41565-025-02079-9}