Scientists uncover key to stable, high-performance, and long-life sodium-ion batteries
A new material design approach, involving copper doping, solves long-standing issue of stacking faults in β-NaMnO2 electrodes, improving stability
Tokyo University of Science
image:
Stacking faults in β-NaMnO2 severely reduce their capacity during charging/discharging cycles. Copper doping effectively eliminates stacking faults, significantly improving cycling stability, enabling the development of long-lasting sodium-ion batteries.
view moreCredit: Professor Shinichi Komaba from Tokyo University of Science, Japan
Sodium (Na)-ion batteries have recently emerged as cost-effective and sustainable alternatives to lithium (Li)-ion batteries. Na, the sixth most abundant element on Earth, offers lower material costs and greater availability compared to Li-ion batteries. The design of cathode materials plays a key role in determining battery life and stability. Layered sodium manganese oxide (NaMnO2) has received increased attention from researchers for its use as a cathode material in Na-ion batteries.
NaMnO2 exists in two crystal forms: α-NaMnO2 and β-NaMnO2. The α-phase features a monoclinic layered structure, where planar MnO2 layers, consisting of edge-sharing distorted MnO6 octahedra, are stacked alternatively with Na-ions in between. β-NaMnO2, on the other hand, features corrugated or zig-zag layers of edge-sharing distorted MnO6 octahedra, also with Na-ions in between. Synthesis of β-NaMnO2 typically requires higher temperatures, often leading to Na-deficient phases.
Attempts to prevent Na-deficient phases produce non-equilibrium β-phases that exhibit several defects. The most notable among these are the stacking faults (SFs), formed by slipping of the crystallographic b-c plane, generating stacking sequences resembling the α-phase. Electrodes made from SF-containing β-NaMnO2 suffer from severe capacity reduction during charge/discharge cycles, limiting their practical applications. Moreover, SFs complicate the understanding of the material’s solid-state chemistry.
In a new study, a research team led by Professor Shinichi Komaba from the Department of Applied Chemistry at Tokyo University of Science (TUS), Japan, investigated how copper (Cu) doping can stabilize SFs in β-NaMnO2. “In a previous study, we found that among the metal dopants, Cu is the only dopant that can successfully stabilize β-NaMnO2,” explains Prof. Komaba. “In this study, we systematically explored how Cu doping can suppress SF and improve the electrochemical performance of β-NaMnO2 electrodes in Na-ion batteries.” The team also included Mr. Syuhei Sato, Mr. Yusuke Mira, and Dr. Shinichi Kumakura from the Research Institute for Science and Technology, TUS. Their findings were published online in the journal Advanced Materials on July 15, 2025.
The team synthesized a series of highly crystalline, Cu-doped β-NaMnO2 samples (NaMn1-xCuxO2) with varying amounts of Cu, denoted as NMCO-00, -05, -10, -12, and -15, corresponding to Cu doping levels from 0% to 15%. The NMCO-00 sample served as the undoped reference. Through X-ray diffraction (XRD) studies, the team found that among the Cu doped samples, NMCO-05 exhibited the highest SF concentration at 4.4%, while in NMCO-12, the SF concentration was only 0.3%, indicating a clear suppression of SFs with increased Cu doping.
Electrochemical evaluation of electrodes made from the NMCO samples in Na half cells revealed significantly enhanced capacity retention in Cu-doped samples. While the undoped sample showed rapid capacity loss within 30 cycles, the SF-free NMCO-12 and -15 samples demonstrated excellent cycle stability, with the NMCO-12 exhibiting no capacity loss for over 150 cycles. These results suggest that the β-phase of layered NaMnO2 is inherently stable when SFs are eliminated.
Importantly, the SF-free structure allowed the researchers to examine the complex phase transitions that occur during Na insertion and extraction in these materials. Using a combination of in situ and ex situ XRD measurements, and density functional theory calculations, the researchers proposed a new structural model involving drastic gliding of the corrugated MnO2 layers. This gliding appears to be unique to the β-phase and was previously obscured by the presence of SFs, marking a major advancement in understanding the characteristic structural changes of the β-phase of NaMnO₂ during electrode reactions.
“Our findings confirm that manganese-based oxides are a promising and sustainable solution for developing highly durable Na-ion batteries,” notes Prof. Komaba. “Owing to the relatively low cost of manganese and Na, this research will lead to more affordable energy-storage solutions for a variety of applications, including smartphones and electric vehicles, ultimately leading to a more sustainable future.”
This study also demonstrates that stabilization of SF using Cu doping could resolve the supply chain vulnerabilities that are commonly faced with metals like lithium. Moreover, the study has potential implications in grid storage, electric vehicles, and consumer electronics.
The study offers valuable insights for developing more stable and long-lasting Na-ion batteries, leading to wider renewable energy adoption, aligning with the United Nations Sustainable Development Goal 7: Affordable and Clean Energy.
***
Reference
DOI:10.1002/adma.202507011
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 Shinichi Komaba from Tokyo University of Science
Dr. Shinichi Komaba is currently a Professor at the Department of Applied Chemistry at Tokyo University of Science (TUS). He obtained his Ph.D. from Waseda University in Japan. At TUS, he also leads the Komaba lab, which focuses on the development of next-generation energy-storage materials. He has published over 490 articles that have received over 40,000 citations. His research primarily focuses on sodium-ion batteries, with a broader focus on functional solid-state chemistry, inorganic industrial materials, and electrochemistry. He has been awarded multiple times for his contributions, which include “Wiley Top viewed article” in 2023.
Funding information
This study was partially funded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Program: Data Creation and Utilization Type Materials Research (JPMXP1122712807), Program for Promoting Research on the Supercomputer Fugaku (JPMXP1020230325), the JST through CREST (Grant No. JPMJCR21O6), ASPIRE (JPMJAP2313), and GteX (JPMJGX23S4).
Journal
Advanced Materials
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Synthesis and Electrochemistry of Stacking Fault-Free β-NaMnO2
Article Publication Date
15-Jul-2025
Pusan National University researchers develop game-changing method to create safer, long-lasting lithium-ion batteries
A novel mathematical framework unlocks unlimited customization of full concentration gradient in high-nickel cathodes for improved safety and stability
image:
The proposed approach allows precise and independent control of average composition, slope, and curvature of full concentration gradients in high-nickel cathodes, resulting in lithium-ion batteries with improved performance, stability, and safety.
view moreCredit: Hyun Deog Yoo from Pusan National University
With the recent global push toward renewable energy and electric vehicles, the demand for lithium-ion batteries (LIBs) is rising rapidly. The performance and stability of LIBs largely depend on the cathode material, which can account for nearly 40–45% of the total battery cost. Among cutting-edge technologies, high-nickel cathodes stand out for their high energy density and cost efficiency. However, increasing the nickel content also intensifies side reactions, severely compromising interfacial robustness and mechanical integrity—factors that limit large-scale applications.
A promising solution is the use of full concentration gradient (FCG) or core–shell designs. In such structures, the nickel concentration gradually decreases from the core to the surface of each cathode particle, where it is replaced by more stable elements such as cobalt and manganese. This gradient enhances surface stability and mechanical strength. Unfortunately, the current fabrication methods offer limited tunability. Once the average composition is set, the slope and curvature of the gradient are also constrained, restricting the design flexibility of FCG cathodes.
In a new study, an international research team led by Associate Professor Hyun Deog Yoo from the Department of Chemistry and the Institute for Future Earth at Pusan National University, Korea, introduced a novel mathematical framework that enables fully flexible FCG design. “Unlike conventional methods, where adjusting one parameter affects the others, our approach allows independent and precise control over multiple descriptors, including average composition, slope, and curvature,” explains Dr. Yoo. The team’s findings were published on June 30, 2025, in the journal ACS Energy Letters.
Traditionally, FCG cathodes are synthesized via a coprecipitation method involving two tanks of metal precursor solutions. The first tank, rich in nickel (Ni), feeds directly into the reactor. The second tank, containing cobalt (Co) and manganese (Mn), is mixed into the first to reduce the Ni concentration over time. In conventional systems, the flow rate of this second tank is fixed, meaning only one specific gradient can be achieved for a given average composition.
The researchers overcame this limitation by expressing the flow rate of the second tank as a time-dependent mathematical function. This innovation allows independent tuning of the average composition, slope, and curvature—enabling the generation of a virtually unlimited range of concentration gradients using just two tanks. By integrating this approach with an automated reactor system, the team successfully synthesized five FCG Ni0.8Co0.1Mn0.1(OH)2 precursors with finely tuned gradients, verified through two- and three-dimensional elemental mapping.
“For this purpose, we assembled an outstanding international research team, collaborating with laboratories at the University of Illinois Chicago, Argonne National Laboratory, and several institutes across Korea and the United States,” says Dr. Yoo. “My lab focused on designing and synthesizing FCG cathodes, while most of the 2D and 3D imaging analyses were conducted by the groups of Prof. Jordi Cabana and Prof. Robert F. Klie. We feel truly privileged to have been part of such a remarkable collaboration.”
The resulting high-nickel cathodes exhibited significantly improved mechanical and structural stability compared to conventional counterparts. They showed enhanced lithium-ion transport for better electrochemical performance and minimal particle cracking—an essential trait for long cycle life. Notably, the optimally designed FCG cathode retained 93.6% of its initial capacity after 300 cycles, the highest cycling stability reported for FCG cathodes of similar composition.
“Our approach has the potential to transform the safety and performance of LIB-based energy storage systems,” says Dr. Yoo. “This could lead to safer consumer electronics and medical devices, more reliable electric vehicles, stable power grids, and broader adoption of renewable energy technologies.”
This work was supported by the Sustainable Utilization of Photovoltaic Energy Research (SUPER) Center, led by Prof. Sung-Ho Jin, under the Engineering Research Center (ERC) program funded by the National Research Foundation of Korea.
***
Reference
DOI: 10.1021/acsenergylett.5c01634
About Pusan National University
Pusan National University, located in Busan, South Korea, was founded in 1946 and is now the No. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service and has approximately 30,000 students, 1,200 professors, and 750 faculty members. The university comprises 14 colleges (schools) and one independent division, with 103 departments in all.
Website: https://www.pusan.ac.kr/eng/Main.do
About Dr. Hyun Deog Yoo
Dr. Hyun Deog Yoo is an Associate Professor of Chemistry at Pusan National University. His research centers on advanced materials for energy storage, with a particular emphasis on lithium-ion and magnesium-ion batteries. The Yoo group adopts a comprehensive approach, integrating materials synthesis, electrochemical analysis, and computational modeling to delve into ion transport and interfacial phenomena. He completed his Ph.D. in Chemical and Biological Engineering from Seoul National University in 2011, followed by postdoctoral training at Bar-Ilan University, the University of Houston, and the University of Illinois Chicago.
Lab website: https://chemlab.pusan.ac.kr/eshel/index.do
ORCID Id: 0000-0001-5188-481X
Journal
ACS Energy Letters
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
High-nickel cathodes with mechanical and interfacial robustness via tailored concentration gradients for stable Li-ion batteries
Solid-state batteries charge faster, last longer
Safer batteries with a smaller footprint
Solid-state batteries charge in a fraction of the time, run cooler, and pack more energy into less space than traditional lithium-ion versions.
A new review from the University of California, Riverside, published in Nano Energy, explains why this technology is poised to transform everything from electric cars to consumer electronics, and represents a major leap in energy storage.
These batteries replace the flammable liquid found in standard versions with a solid material that is safer and far more efficient. Where today’s batteries may take 30 to 45 minutes to reach 80% charge, solid-state models can cut that time to 12 minutes, and in some cases, as little as three.
Lead author Cengiz Ozkan, a professor of mechanical engineering at UCR, said the benefits come down to chemistry and engineering. “By removing the liquid and using stable solid materials instead, we can safely push more electricity into the battery at once, without the risks of overheating or fires,” he said.
Conventional lithium-ion batteries move lithium ions, the particles that carry electric charge, through a liquid. But that liquid can degrade over time, limit charging speed, and pose fire risks. Solid-state batteries use a solid material instead, which offers a safer and more stable environment for lithium ions to move through. This enables faster, more efficient charging with fewer safety concerns.
The solid inside these batteries is known as a solid-state electrolyte. The review highlights three main types: sulfide-based, oxide-based, and polymer-based. Each type has strengths: some allow ions to move faster, others offer better long-term stability or are easier to manufacture. One standout group, sulfide-based electrolytes, performs almost as well as the liquid in current batteries, but without the downsides.
The researchers also describe the tools scientists now use to watch batteries work in real time. Techniques like neutron imaging and high-powered X-rays let researchers see how lithium moves inside a battery as it charges and discharges. This helps identify areas where the lithium gets stuck or where unwanted structures called “dendrites” start to grow. Dendrites are tiny, needle-like formations that can cause a battery to short-circuit or fail.
Understanding these inner workings is key to making better batteries. “These imaging tools are like an MRI for batteries,” Ozkan said. “They let us watch the battery’s vital signs and make smarter design choices.”
Solid-state batteries also tend to use lithium more efficiently. Many designs feature a lithium metal layer that can store more energy in less space than the graphite layers used in current batteries. This means solid-state batteries can be lighter and smaller while still powering devices for just as long, or longer.
While conventional lithium-ion batteries typically begin to show noticeable degradation after approximately 5–8 years of use in electric vehicles, solid-state batteries could remain functional for 15–20 years or more, depending on usage and environmental factors.
“Traditional lithium-ion batteries, while revolutionary, are reaching their performance and safety limits as electric vehicles, renewable energy grids, portable electronics, and aerospace systems become more widespread and demanding,” Ozkan said.
Ozkan said solid-state batteries could also play a pivotal role in the future of interstellar travel and space exploration.
Due to their thermal and chemical stability, these batteries are better suited to withstand extreme temperatures and radiation conditions in outer space. They’re also able to store more power in less space, which is critical for missions where every cubic centimeter counts. And without liquid electrolytes, they would be more reliable in closed, oxygen-controlled environments like spacecraft or planetary bases.
The researchers’ goal with this review was to guide researchers and technologists in accelerating the development, scalability, and real-world deployment of solid-state systems.
But challenges remain. Making these batteries on a large scale is still difficult and expensive. The paper offers a roadmap for solving these problems, including developing better materials, refining how the battery parts interact, and improving factory techniques to make production easier.
“Solid-state batteries are moving closer to reality every day,” Ozkan said. “Our review shows how far the science has come and what steps are needed next to make these batteries available for everyday use.”
Journal
Nano Energy
Article Title
A comprehensive review of solid-state lithium batteries: Fast Charging characteristics and in-operando diagnostics
