A research team at Tokyo University of Science (TUS) has unveiled a significant advancement in sodium-ion battery technology, offering a promising alternative to lithium-based systems. The study, published in Advanced Materials, introduces copper (Cu) doping as a method to eliminate structural defects in β-phase sodium manganese oxide (β-NaMnO₂), thereby significantly enhancing battery life and performance.
Sodium-ion batteries, known for their cost-effectiveness and environmental advantages, rely heavily on stable electrode materials. However, the β-phase of NaMnO₂—a promising cathode material—has been hindered by stacking faults (SFs), which degrade its cycling stability. The TUS research team, led by Professor Shinichi Komaba, discovered that Cu doping can successfully suppress these faults.
“In our previous work, we identified Cu as the only metal dopant that can stabilize the β-phase,” said Prof. Komaba. “This study confirms its role in improving electrochemical performance by drastically reducing stacking faults.”
The team synthesized several NaMn₁₋ₓCuₓO₂ compounds with varying Cu concentrations. Their tests revealed that higher Cu content corresponded with a marked decrease in SFs. One sample with 12% Cu doping (NMCO-12) showed nearly complete elimination of SFs and exhibited no capacity loss after 150 charge-discharge cycles.
This development not only extends the lifespan of sodium-ion batteries but also provides new insights into their structural behavior. By removing SFs, the researchers could observe unique gliding of MnO₂ layers—key to understanding the phase transitions during battery operation.
The breakthrough has broad implications across consumer electronics, electric vehicles, and grid storage, potentially reducing dependence on lithium and associated supply chain risks.
“This work contributes directly to making sustainable, affordable energy storage a reality,” added Prof. Komaba, whose team included researchers from TUS’s Research Institute for Science and Technology.
Funded by Japan’s MEXT and JST programs, the study aligns with the UN’s Sustainable Development Goal 7, advocating clean and accessible energy.
