With each week that passes, it seems as if we are being informed of another breakthrough in electric car battery chemistries. Researchers and developers currently involved in the energy storage industry are currently hard at work to try and find new ways to make future EV batteries safer, more reliable, and denser, in a bid to improve long-term viability, cost-effectiveness, and sustainability. Lithium-ion is currently the leading chemistry in the modern EV sphere, affording some cars as much as 300 miles of range on a single charge.
Despite its effectiveness and 15-year lifespan, lithium chemistry still struggles with a lot of challenges. The sourcing of the rare earth remains a problematic issue, as it has ecological and humanitarian concerns tied to it. Lithium is also a very expensive material to source and distribute, adding to the issue of reducing net-zero carbon outputs at a feasible rate. A team of researchers in Berlin may have come up with a way to alleviate the strain that lithium battery production places on the industry by using an innovative chemical method that consists of sodium.
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Understanding The Effectiveness Of Sodium In Batteries
The New Chemical Process Vastly Improves Stability
Researchers at the Helmholtz Institute Berlin have uncovered a new storage mechanism that could change the future of sodium-ion batteries. It consists of the co-intercalation of sodium ions and solvent molecules in cathode materials that operate as a reversible and rapid process rather than a destructive one. Opting for this method enables efficient high-rate sodium-ion cells with fast charging potential. Co-intercalation is a mechanism in batteries where both ions and solvent molecules simultaneously insert into a layered electrode material. This process can significantly alter battery performance by improving kinetics and power density, though it can also lead to electrode degradation.
Traditionally, both lithium-ion and sodium-ion batteries rely on intercalation. This process involves the migration of ions into electrode structures, while co-intercalation involves ions moving together with solvent molecules, which have long been considered unstable and likely to trigger premature battery failure. The HZB study, led by Professor Philipp Adelhelm, demonstrates that solvent co-intercalation can instead stabilize and enhance cathode performance, delivering high rate capability with minimal capacity loss and suggesting entirely new design strategies for next-generation sodium-ion batteries.
The Process Of Testing Sodium Under Stressful Conditions
The team focused on layered transition metal sulfides as potential cathode hosts. Since 2022, Dr. Yanan Sun has performed extensive volume change measurements, structural studies using synchrotron radiation, and electrochemical tests on electrode solvent systems to understand the mechanisms at play. This work revealed that while co-intercalation in graphite anodes with glyme molecules had previously been shown as reversible, translating this concept to cathodes had been an elusive process, until HZB’s discovery. The breakthrough shows us that cathodes can retain capacity while displaying unusually fast reaction kinetics, with certain materials even approaching supercapacitor-like behavior.
Dr. Sun explains that cathode co-intercalation processes differ fundamentally from those in graphite, which underscores the novelty of the finding and highlights the potential for designing new cathode chemistries around this effect. Adelhelm emphasizes that exploring co-intercalation as a beneficial mechanism was risky because it contradicted established battery science, yet support from the European Research Council through an ERC Consolidator Grant enabled the research to move forward.
What Comes Next For The Research Team
The group published its results in Nature Materials, showing that, instead of being a liability, solvent-assisted ion migration can open a pathway towards highly efficient batteries with faster charging and discharging rates. Earlier HZB studies had already shown reversible co-intercalation of sodium with glyme molecules in graphite anodes, but replicating the same process for cathodes remained elusive until this project focused on layered transition metal sulfides as potential hosts.
In collaboration with theorist, Dr. Gustav Åvall, the team also identified key parameters that can be used to predict future co-intercalation behavior, which will guide the discovery of next-generation electrode materials. Adelhelm emphasized that pursuing this idea went against classical battery knowledge and carried significant risk, but funding through the ERC Consolidator Grant allows the research to proceed and ultimately reveal a vast chemical landscape of layered materials that could be tuned for novel applications beyond traditional energy storage. He stressed that the project’s success depended on international collaboration as well as institutional support from the Helmholtz Zentrum Berlin, Humboldt University, and the joint research group on operando battery analysis, which enabled real-time studies of electrode processes under working conditions.
Looking ahead, the formation of the Berlin Battery Lab involving HZB will create even more opportunities to advance this line of research and accelerate the development of sodium-ion batteries that combine low-cost-abundant raw materials with superfast kinetics. Adelhelm and Sun note that the ability to engineer cathode materials capable of stable co-intercalation marks a turning point in sodium ion research because it redefines a process once thought fatal to battery life as a mechanism that can deliver the kind of rapid charge and discharge performance required for scalable energy storage solutions.
The Downside Of Applying Sodium To Batteries
The Innovative Application Still Has Its Flaws
Sodium is a cost-effective and abundant alternative to lithium for batteries, but developers are going to have to confront some downsides, which will ultimately limit its widespread adoption. The most noteworthy issue is its lower energy density, due to the fact that sodium ions are larger and heavier than lithium ions. This reduces how tightly manufacturers can pack them into electrode structures, leading to lower energy per unit weight or volume. Considering EVs are already much heavier than they need to be, this is a very noteworthy concern.
Heavier batteries translate into shorter driving ranges and less compact designs for general portable electronics such as smartphones. Another drawback is the overall cycle life that larger sodium ions will place in the pack. This element suffers from greater structural strain and volume expansion in electrode materials during repeated charging and discharging, which accelerates material degradation and shortens overall battery lifespan. Electrolyte compatibility also poses a challenge, as sodium tends to form unstable interfaces with common liquid electrolytes, resulting in poor solid electrolyte interphase layers that compromise efficiency and safety.
Thermal stability presents further concerns, as sodium-ion batteries generally operate within narrower temperature windows and show a higher risk of performance drop under extreme heat or cold compared to lithium-ion systems. Additionally, cathode material options for sodium are more limited, with fewer proven high-performance chemistries available. This makes large-scale commercialization a much more challenging task. The manufacturing infrastructure also still favors lithium, which is something that is very unlikely to change anytime soon.
Scaling sodium technology requires new production lines and supply chains, which will add to the cost and complexity in the short term. Manufacturers have already invested billions in their current energy storage plans, so it’s unlikely that we are going to get to see innovations that deviate from lithium come into play. Ultimately, while sodium is abundant, its lower energy density makes it less suited to applications demanding maximum storage capacity, such as aviation or long-range vehicles, restricting its role mainly to stationary grid storage or low-cost short-range devices.
HZB’s Other Noteworthy Achievements In The Field
The Helmholtz Institute Berlin has built a reputation as one of Europe’s leading centers for energy and materials research, with projects extending far beyond sodium ion batteries into areas that address the challenges of renewable integration, sustainable energy storage, and advanced material development.
The facility spends a lot of time focusing on photovoltaics, where researchers have made breakthroughs in thin film solar cells, including perovskite silicon tandem designs that push efficiency levels close to commercial viability while reducing production costs. HZB also has an advanced hydrogen research program. The institute has explored photoelectrochemical water splitting, aiming to harness solar energy to generate green hydrogen, and has contributed to catalyst development that improves efficiency in fuel cells and electrolyzers.
Breakthroughs And Collaborative Efforts Prove To Be Valuable Moving Forward
The firm has long been associated with the operation of BESSY II, which is a powerful synchrotron light source in Berlin that supports materials science investigations across physics, chemistry, and biology, enabling researchers worldwide to probe structures at atomic and molecular scales. Collaborations with universities and industry have led to advances in thermoelectrics, magnetic materials, and quantum materials, with the goal of finding practical routes to more efficient energy conversion and storage. The institute has also invested in developing sustainable recycling strategies for critical battery materials like cobalt and nickel to reduce dependence on resource-intensive mining, which has proven to be a crucial contribution to the region’s burgeoning EV production industry.