Breaking performance barriers of all solid state batteries
Batteries are an essential technology in modern society, powering smartphones and electric vehicles, yet they face limitations such as fire explosion risks and high costs. While all-solid-state batteries have garnered attention as a viable alternative, it has been difficult to simultaneously satisfy safety, performance, and cost. Recently, a Korean research team successfully improved the performance of all-solid-state batteries simply through structural design—without adding expensive metals.
KAIST announced on January 7th that a research team led by Professor Dong-Hwa Seo from the Department of Materials Science and Engineering, in collaboration with teams led by Professor Sung-Kyun Jung (Seoul National University), Professor Youn-Suk Jung (Yonsei University), and Professor Kyung-Wan Nam (Dongguk University), has developed a design method for core materials for all-solid-state batteries that uses low-cost raw materials while ensuring high performance and low risk of fire or explosion.
Conventional batteries rely on lithium ions moving through a liquid electrolyte. In contrast, all-solid-state batteries use a solid electrolyte. While this makes them safer, achieving rapid lithium-ion movement within a solid has typically required expensive metals or complex manufacturing processes.
To create efficient pathways for lithium-ion transport within the solid electrolyte, the research team focused on "divalent anions" such as oxygen and sulfur . Divalent anions play a crucial role in altering the crystal structure by integrating into the basic framework of the electrolyte.
The team developed a technology to precisely control the internal structure of low-cost zirconium (Zr)-based halide solid electrolytes by introducing these divalent anions. This design principle, termed the "Framework Regulation Mechanism," widens the pathways for lithium ions and lowers the energy barriers they encounter during transport. By adjusting the bonding environment and crystal structure around the lithium ions, the team enabled faster and easier movement.
To verify these structural changes, the researchers utilized various high-precision analysis techniques, including:
- High-energy Synchrontron X-ray diffraction(Synchrotron XRD)
- Pair Distribution Function (PDF) analysis
- X-ray Absorption Spectroscopy (XAS)
- Density Functional Theory (DFT) modeling for electronic structure and diffusion.
The results showed that electrolytes incorporating oxygen or sulfur improved lithium-ion mobility by 2 to 4 times compared to conventional zirconium-based electrolytes. This signifies that performance levels suitable for practical all-solid-state battery applications can be achieved using inexpensive materials.
Specifically, the ionic conductivity at room temperature was measured at approximately 1.78 mS/cm for the oxygen-doped electrolyte and 1.01 mS/cm for the sulfur-doped electrolyte. Ionic conductivity indicates how quickly and smoothly lithium ions move; a value above 1 mS/cm is generally considered sufficient for practical battery applications at room temperature.
Professor Dong-Hwa Seo stated, "Through this research, we have presented a design principle that can simultaneously improve the cost and performance of all-solid-state batteries using cheap raw materials. Its potential for industrial application is very high." Lead author Jae-Seung Kim added that the study shifts the focus from "what materials to use" to "how to design them" in the development of battery materials.
This study, with Jae-Seung Kim (KAIST) and Da-Seul Han (Dongguk University) as co-first authors, was published in the international journal Nature Communications on November 27, 2025.
- Paper Title: Divalent anion-driven framework regulation in Zr-based halide solid electrolytes for all-solid-state batteries
- DOI: https://www.nature.com/articles/s41467-025-65702-2
This research was supported by the Samsung Electronics Future Technology Promotion Center, the National Research Foundation of Korea, and the National Supercomputing Center.
Journal
Nature Communications
Article Title
Divalent anion-driven framework regulation in Zr-based halide solid electrolytes for all-solid-state batteries
New process for stable, long-lasting all-solid-state batteries
Paul Scherrer Institute
image:
Jinsong Zhang (left) and Mario El Kazzi with a test cell of the all-solid-state battery developed at the Paul Scherrer Institute PSI. The two researchers developed a process that combines mild sintering with an ultrathin lithium fluoride coating, thus enabling the production of particularly stable solid-state electrolytes.
view moreCredit: © Paul Scherrer Institute PSI/Mahir Dzambegovic
Researchers at the Paul Scherrer Institute PSI have achieved a breakthrough on the path to practical application of lithium metal all-solid-state batteries – the next generation of batteries that can store more energy, are safer to operate, and charge faster than conventional lithium-ion batteries.
All-solid-state batteries are considered a promising solution for electromobility, mobile electronics, and stationary energy storage – in part because they do not require flammable liquid electrolytes and therefore are inherently safer than conventional lithium-ion batteries.
Two key problems, however, stand in the way of market readiness: On the one hand, the formation of lithium dendrites at the anode remains a critical point. These are tiny, needle-like metal structures that can penetrate the solid electrolyte conducting lithium ions between the electrodes, propagate toward the cathode, and ultimately cause internal short circuits. On the other hand, an electrochemical instability – at the interface between the lithium metal anode and the solid electrolyte – can impair the battery’s long-term performance and reliability.
To overcome these two obstacles, the team led by Mario El Kazzi, head of the Battery Materials and Diagnostics group at the Paul Scherrer Institute PSI, developed a new production process: “We combined two approaches that, together, both densify the electrolyte and stabilise the interface with the lithium,” the scientist explains. The team has reported these results in the journal Advanced Science.
The problem with densification
Central to the PSI study is the argyrodite type Li₆PS₅Cl (LPSCl), a sulphide-based solid electrolyte made of lithium, phosphorus, and sulphur. The mineral exhibits high lithium-ion conductivity, enabling rapid ion transport within the battery – a crucial prerequisite for high performance and efficient charging processes. This makes argyrodite-based electrolytes promising candidates for solid-state batteries. Up to now, however, implementation has been hampered by the difficulty of densifying the material sufficiently to prevent the formation of voids that lithium dendrites could penetrate.
To densify the solid electrolyte, research groups have relied on one of two approaches: applying very high pressure to compress the material at room temperature or employing processes that combine pressure with temperatures exceeding 400 degrees Celsius. In the latter approach, known as classical sintering, the application of heat and pressure causes the particles to fuse into a denser structure.
Both methods, however, can lead to undesirable side-effects: Compression at room temperature is insufficient because it results in a porous microstructure and excessive grain growth. Processing at very high temperatures, on the other hand, carries the risk of breaking down the solid electrolyte. Therefore the PSI researchers had to pursue a new approach to obtain a robust electrolyte and a stable interface.
The temperature trick
To densify argyrodite into a homogeneous electrolyte, El Kazzi and his team did incorporate the temperature factor, but in a more careful way: Instead of the classic sintering process, they chose a gentler approach in which the mineral was compressed under moderate pressure and at a moderate temperature of only about 80 degrees Celsius. This gentle sintering proved successful: The moderate heat and pressure ensured that the particles arranged themselves as desired without altering the material’s chemical stability. The particles in the mineral formed close bonds with each other, porous areas became more compact, and small cavities closed. The result is a compact, dense microstructure resistant to the penetration of lithium dendrites. Already, in this form, the solid electrolyte is ideally suited for rapid lithium-ion transport.
However, gentle sintering alone was not enough. To ensure reliable operation even at high current densities, such as those encountered during rapid charging and discharging, the all-solid-state cell required further modification. For this purpose, a coating of lithium fluoride (LiF), only 65 nanometres thick, was evaporated under vacuum and applied uniformly to the lithium surface – serving as a ultra-thin passivation layer at the interface between the anode and the solid electrolyte.
This intermediate layer fulfils a dual function: On the one hand, it prevents the electrochemical decomposition of the solid electrolyte upon contact with the lithium, thus suppressing the formation of “dead,” inactive lithium. On the other hand, it acts as a physical barrier, preventing the penetration of lithium dendrites into the solid electrolyte.
Best results after 1,500 cycles
In laboratory tests with button cells, the battery demonstrated extraordinary performance under demanding conditions. “Its cycle stability at high voltage was remarkable,” says doctoral candidate Jinsong Zhang, lead author of the study. After 1,500 charge and discharge cycles, the cell still retained approximately 75 percent of its original capacity. This means that three-quarters of the lithium ions were still migrating from the cathode to the anode. “An outstanding result. These values are among the best reported to date.” Zhang therefore sees a good chance that all-solid-state batteries could soon surpass conventional lithium-ion batteries with liquid electrolyte in terms of energy density and durability.
Thus El Kazzi and his team have demonstrated for the first time that the combination of solid electrolyte mild sintering and a thin passivation layer on lithium anode effectively suppresses both dendrite formation and interfacial instability – two of the most persistent challenges in all-solid-state batteries. This combined solution marks an important advance for all-solid-state battery research – not least because it offers ecological and economic advantages: Due to the low temperatures, the process saves energy and therefore costs. “Our approach is a practical solution for the industrial production of argyrodite-based all-solid-state batteries,” says El Kazzi. “A few more adjustments – and we could get started.”
Text: Andreas Lorenz-Meyer
Left: Porous solid electrolyte through which lithium dendrites (gray) can penetrate to the lithium surface (silver); the interface is protected only by a natural boundary layer (pink).
Right: Densely sintered solid electrolyte produced at the Paul Scherrer Institute PSI with a stabilising lithium fluoride coating (blue) that prevents dendrite penetration and protects the lithium surface.
Credit
© Paul Scherrer Institute PSI/Jinsong Zhang
About PSI
The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of future technologies, energy and climate, health innovation and fundamentals of nature. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2300 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 450 million. PSI is part of the ETH Domain, with the other members being the two Swiss Federal Institutes of Technology, ETH Zurich and EPFL Lausanne, as well as Eawag (Swiss Federal Institute of Aquatic Science and Technology), Empa (Swiss Federal Laboratories for Materials Science and Technology) and WSL (Swiss Federal Institute for Forest, Snow and Landscape Research).
Journal
Advanced Science
Subject of Research
Not applicable
Article Title
Synergistic Effects of Solid Electrolyte Mild Sintering and Lithium Surface Passivation for Enhanced Lithium Metal Cycling in All-Solid-State Batteries
Article Publication Date
8-Jan-2026
Illinois Tech researcher finds where lithium ions reside in new solid-state electrolyte that could lead to improved batteries
Research Professor of Chemistry James Kaduk co-authored a paper in Science that details a material with high ionic conductivity—even at low temperatures—which could prove crucial in developing next generation of lithium batteries
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Illinois Tech Research Professor of Chemistry James Kaduk
view moreCredit: Illinois Institute of Technology
CHICAGO—January 9, 2026—New research published in Science introduces a promising solid electrolyte material that could improve the performance of next-generation lithium batteries, particularly at lower temperatures. Illinois Institute of Technology (Illinois Tech) Research Professor of Chemistry James Kaduk, who co-authored the paper, contributed a key finding to the research: identifying where lithium atoms reside within the crystalline structure.
The paper, “Anion Sublattice Design Enables Superionic Conductivity in Crystalline Oxyhalides,” describes a new material known as lithium tantalum oxychloride (LTOC), whose high ionic conductivity and low activation energy, even in the cold, could facilitate the development of high-performance solid-state batteries.
Lithium, the lightest metal, is widely used in batteries because its ions move easily, allowing energy to be stored and released efficiently. Understanding how lithium ions move through this new material was essential to explaining LTOC’s unusually strong performance.
“My contribution is small but ends up being useful,” says Kaduk. “What really gets me excited is finding out where the atoms are.”
Kaduk’s task wasn’t straightforward. The primary tool he often uses to map atomic structures—X-ray diffraction—has trouble detecting lighter elements such as hydrogen and lithium, especially when they are surrounded by heavier elements such as tantalum.
“Since X-rays scatter off electrons, lithium having only three electrons can be especially hard to find,” says Kaduk.
Instead of trying to find the lithium atoms directly, Kaduk used an indirect approach by looking for empty spaces where those atoms could exist. Since atoms can’t overlap, once the positions of the heavier atoms were known, Kaduk could then find small gaps between them that were large enough to accommodate lithium ions.
By gradually narrowing the size of his search, Kaduk identified a set of sites—open positions within the crystal structure where small particles can fit and move through—that could host lithium. Those sites sit close enough together to allow lithium ions to “hop” easily from one site to the next.
That detail proved to be critical. The structure revealed long, rigid chains of tantalum, oxygen, and chlorine that create open channels between them. Lithium ions diffuse through those channels, moving more efficiently than in current batteries along the length of the material. This process helps create better batteries because the more freely lithium ions can move through a structure, the better a battery performs.
With the lithium positions identified, the team then tested the structure using quantum mechanical calculations to confirm that the structure would remain stable.
“We apply what are called ‘density functional quantum mechanical techniques’ to optimize the structure,” Kaduk says. “In this case, the structure stayed very nearly the way it refined, so that provided some extra evidence for the correctness of the structure.”
The open pathways revealed by the structure help explain one of the material’s most promising properties: it conducts lithium ions well even at low temperatures. This property makes it especially valuable for applications ranging from electric vehicles to energy storage in cold climates.
While his role is just one part of a much larger international collaboration, Kaduk’s contribution helped turn an intriguing observation into a clearer understanding of how the material works, bringing researchers one step closer to designing better batteries.
For Kaduk, the reward comes from having solved that molecular puzzle.
“Being able to complete the job just based on some pretty simple ideas, that’s very satisfying,” says Kaduk. “Especially when you do the quantum mechanics calculations and see that they’re pretty happy with where these lithiums were, it gives you extra confidence.”
Journal
Science
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Anion sublattice design enables superionic conductivity in crystalline oxyhalides
Breakthrough in thin-film electrolytes pushes solid oxide fuel cells forward
Researchers achieve record-setting oxide-ion conductivity at medium temperatures, paving the way for safer and more efficient power generation
image:
The highly oriented Sm-doped CeO2 thin films developed in this study achieved remarkable oxide-ion conductivities over a wide temperature range.
view moreCredit: Professor Tohru Higuchi from Tokyo University of Science, Japan Image link: https://journals.jps.jp/doi/10.7566/JPSJ.95.014706
Under the threat of climate change and geopolitical tensions related to fossil fuels, the world faces an urgent need to find sustainable and renewable energy solutions. While wind, solar, and hydroelectric power are key renewable energy sources, their output strongly depends on environmental conditions, meaning they are unable to provide a stable electricity supply for modern grids. Solid oxide fuel cells (SOFCs), on the other hand, represent a promising alternative; these devices produce electricity on demand directly from clean electrochemical reactions involving hydrogen and oxygen.
However, existing SOFC designs still face technical limitations that hinder their widespread adoption for power generation. SOFCs typically rely on bulk ceramic electrolytes and require high operating temperatures, ranging from 600–1,000 °C. This excessive heat not only forces manufacturers to use expensive, high-performance materials, but also leads to earlier component degradation, limiting the cell’s service life and driving up costs. Such extreme temperatures are necessary to overcome resistance that blocks the flow of oxide ions—the charge carriers—through the ceramic electrolyte. This issue, known as grain boundary resistance, is caused by defects and chemical barriers at the interfaces between ceramic particles.
To address this challenge, a research team led by Professor Tohru Higuchi from the Department of Applied Physics at Tokyo University of Science (TUS), Japan, developed an innovative electrolyte design. Their paper, made available online in the Journal of the Physical Society of Japan on December 19, 2025, and in Volume 95, Issue 1, on January 15, 2026, was co-authored by a second-year Master’s Course student Mr. Ryota Morizane from the Graduate School of Advanced Engineering at TUS, as well as Assistant Professor Daisuke Shiga and Professor Hiroshi Kumigashira from the Institute of Multidisciplinary Research for Advanced Materials at Tohoku University, Japan.
The team’s strategy involved fabricating ultra-thin electrolyte layers of samarium-doped cerium oxide (SDC), a material already known for its exceptional oxide-ion conductivity. Their key innovation was ensuring precise control over the material’s structure during deposition of the films. Using single-crystal yttria-stabilized zirconia (YSZ) as a substrate, the researchers directed the SDC crystals to align themselves in a specific direction—known as the a-axis orientation—across the entire thin film. This highly controlled crystal orientation minimized the structural imperfections that typically cause high grain boundary resistance and limit oxide-ion conductivity.
“We thought if we could fabricate an oriented film based on SDC with a large number of oxygen vacancies on YSZ as a substrate, we could achieve high oxide-ion conductivity at a practical level, higher than that of the existing materials,” says Prof. Higuchi
The researchers tested their new thin-film electrolyte design through a series of experiments and analytical measurements. They found that the structurally ordered SDC thin film achieved world-record-high oxide-ion conductivity at temperatures between 200–550 °C. Operating in this temperature range, rather than the standard 600–1,000 °C, can drastically improve the practicality and safety of fuel cell technology. By requiring less heat, the system is less prone to material stress. In turn, this enables the use of less expensive components, speeds up the cell’s start-up time, and increases overall energy efficiency. “Our findings suggest that a-axis-oriented SDC thin films with high chemical stability are promising as innovative electrolyte materials for practical SOFCs,” states Prof. Higuchi.
This green energy innovation directly addresses one of the key roadblocks preventing the mass adoption of hydrogen power. By making SOFCs safer, durable, and more cost-effective, the proposed solution could help accelerate the transition away from fossil fuels and toward a hydrogen economy.
Notably, this development is not limited to power generation alone, as Prof. Higuchi explains, “The proposed thin films with high oxide-ion conductivity have interesting potential applications not only in fuel cells but also in all-solid-state electric double layer transistors based on ionic conductors, which can be used in brain-inspired computing.” Thus, the implications of this materials science breakthrough could extend beyond energy solution technologies to state-of-the-art computing.
If an electrode material that can maximize the performance of this electrolyte membrane is discovered in the future, practical application could be feasible. If more research using the sputtering method is reported around the world, the technology can be commercialized. Further efforts in this field will hopefully pave the way for affordable clean energy in the near future.
***
Reference
DOI: 10.7566/JPSJ.95.014706
About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.
With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.
Website: https://www.tus.ac.jp/en/mediarelations/
About Professor Tohru Higuchi from Tokyo University of Science
Dr. Tohru Higuchi serves as Professor at the Department of Applied Physics at Tokyo University of Science. He received his bachelor's degree in Applied Physics from Tokyo University of Science in 1995, where he later earned his master's and PhD degrees. His research focuses on functional material science, with a particular emphasis on thin-film/surface and interfacial physical characteristics, as well as inorganic industrial materials. He has published over 220 articles and earned several honors, including those for his contributions to the GREEN-2019 conference and the 2019 International Symposium on Advanced Material Research.
Funding information
This work was partially supported by a Grant-in-Aid for Scientific Research (25K01661) from the Japan Society for the Promotion of Science (JSPS).
Journal
Journal of the Physical Society of Japan
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Oxide Superionic Conductivity of a-Axis-Oriented Ce0.75Sm0.25O2-δ Thin Film on Yttria-Stabilized Zirconia Substrate
Article Publication Date
15-Jan-2026
Researchers achieve breakthrough in transition metal fluorides cathodes for thermal batteries
Chinese Academy of Sciences Headquarters
image:
Illustration of size selective transmission of ions between electrolyte and cathode enabled by sub-nanoporous interface
view moreCredit: XU Mengfan
Transition metal fluorides are widely regarded as promising cathode materials because of their high theoretical voltages and excellent thermal stability. However, in real batteries these materials tend to dissolve and migrate within the electrolyte during operation—a phenomenon often called the "shuttle effect"—causing active material loss, declining capacity, and long-term structural damage.
To address this problem, a research team led by Profs. WANG Song and ZHU Yongping from the Institute of Process Engineering of the Chinese Academy of Sciences has developed a new approach to suppressing the shuttle effect in transition metal fluoride cathodes. The team's study focused on thermal batteries—a type of battery that operates at 350–550 °C—with findings published in Advanced Science on January 4.
Using an ion-sieving concept to achieve selective confinement, the researchers constructed a covalent organic framework (COF)-derived carbon shell with uniform sub-nanometer (0.54 nm) channels on the surface of cobalt difluoride (CoF2) particles. This design yields a unique "plum pudding@shell" composite structure, in which active particles are encapsulated within a porous carbon shell.
Experimental results demonstrated that the resulting CoF2@CSC700-24 cathode achieved an unprecedented discharge plateau voltage exceeding 2.5 V at 100 mA cm-2 and 500 °C, with a specific capacity of 365 mAh g-1 and a specific energy of 882 Wh kg-1, representing the highest reported value among high-voltage thermal battery cathodes to date.
To explain this performance breakthrough, the researchers identified a "size-sieving confinement mechanism." Thermodynamic analysis and experimental validation revealed that CoF2 undergoes anion exchange with LiCl in the electrolyte to form CoCl42- complexes, which are primarily responsible for active material migration. The tailored sub-nanometer channels effectively block the diffusion of the larger CoCl42- complexes while allowing the rapid transport of smaller Li+ ions, thereby significantly suppressing the shuttle effect.
"Our findings provide a mechanistical foundation for designing next-generation high-energy-density thermal batteries through precise interfacial engineering," said Prof. WANG Song, corresponding author of the study.
This work not only advances the theoretical understanding of how the shuttle effect can be suppressed in molten salt systems; it also opens up new possibilities for the application of metal fluorides in other high-energy storage devices.
Journal
Advanced Science
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Selective Confinement by a COF-Derived Sub-Nanoporous Interface for High-Performance CoF2 Thermal Battery Cathodes
Article Publication Date
4-Jan-2026
