#Japan #Tokyo #Sodium-ion #Battery Innovation #Scandium Doping

Enhancements in Sodium-Ion Batteries with Scandium Substitution

Introduction

Sodium-ion batteries (SIBs) are receiving increasing attention as a promising alternative to lithium-ion batteries due to their potential for lower costs and greater environmental sustainability. Recent research conducted by a collaborative team at Tokyo University of Science has made notable strides in this field, enhancing the performance of sodium-ion batteries through the substitution of manganese ions with scandium ions in the cathode material.

Research Overview

In a study published in the journal Advanced Materials on September 12, 2025, researchers demonstrated that incorporating scandium into the structure of P’2-type Na0.67MnO2 can significantly improve both water resistance and cycle life. The specific compound tested, P’2-Na0.67[Mn0.92Sc0.08]O2, also known as o-NMSO8, exhibited an average discharge voltage exceeding 2.1 V and an initial discharge capacity above 170 mAh/g, maintaining approximately 60% of its capacity after 300 cycles.

Background to Sodium-Ion Batteries

NaxMnO2, a sodium-containing layered oxide commonly used as a cathode material, has faced challenges regarding its cycle stability. The primary issue arises from structural degradation due to redox reactions occurring in manganese ions during sodium ion insertion and removal, leading to significant performance drops over repeated cycles. Previous studies indicated that partial substitution of manganese with other metals can enhance stability and capacity retention, thus sparking further research into the mechanisms behind these improvements.

The Role of Scandium

In the current study, the research team, which includes scholars such as Kodai Moriya and Shinichi Kumakura, aimed to elucidate the effects of scandium substitution on both the electrochemical properties and structural stability of sodium-layered oxides. The research revealed that scandium acts as a stabilizing agent within the P’2-type structure, enhancing the balance between electron localization and ionic mobility, which is crucial for efficient battery operation.

Results and Discussion

Structural Stability Improvement

The findings indicate that the scandium doping enhances the stability of the P’2 structure by effectively controlling the Jahn-Teller distortions associated with manganese. Furthermore, structural analyses showed that the crystallinity of o-NMSO8 remains intact after extensive cycling, unlike its unmixed counterpart, Na0.67MnO2, which suffers significant structural degradation. This is primarily attributed to the ability of scandium ions to modulate the local and macroscopic structure of the material, suppressing excessive lattice distortion.

Electrochemical Performance

Electrochemical testing using coin cells demonstrated that o-NMSO8 outperforming earlier manganese-only compositions by maintaining a higher capacity retention over cycles. Initial capacities for scandium-substituted samples remained consistently high, indicating enhanced electrode performance due to the formation of a protective layer at the electrode-electrolyte interface, which decreases side reactions and enhances moisture resistance.

Mechanistic Insights

The substitute's success stems from the larger ionic radius of scandium, which provides a structural backbone robust enough to stabilize the material during redox cycling. Unlike other substitutes tested, such as aluminum and yttrium, scandium shows unique capabilities in maintaining the desired properties of the layered structure, further supporting its relevance in battery technology.

Conclusion

This innovative approach involving the replacement of manganese ions with scandium presents new opportunities in the development of high-performance sodium-ion batteries. As the demand for efficient and sustainable energy storage solutions rises, the insights garnered from this study could pave the way toward wider adoption and practical applications of sodium-ion batteries in various energy storage systems. Professor Shinichi Komaba, who led the project, expressed optimism regarding the findings, revealing their potential contribution to advancing the practical implementation and longevity of sodium-ion technology.

Future Directions

With the demonstrated promise of scandium doping in sodium-ion batteries, future research will explore broader applications and further optimization of cathode materials to push towards commercial viability. The ongoing support from various research programs emphasizes the significance of this work in addressing the energy challenges faced globally.

References

1. Moriya, K., Kumakura, S., & Komaba, S. (2025). Unique Impacts of Scandium Doping on Electrode Performance of P’2- and P2-type Na2/3MnO2. Advanced Materials. DOI:10.1002/adma.202511719