A new study from Tokyo University of Science reveals how scandium doping dramatically improves the cycling stability of sodium-ion batteries, offering a viable path toward long-life, high-capacity alternatives to lithium-ion systems.
Layered sodium manganese oxides (Na₂/₃MnO₂) are attractive cathode materials due to their high initial capacity and abundance of sodium. Yet, they suffer from rapid capacity fading, largely driven by Jahn-Teller distortion – lattice deformations caused by Mn³⁺ ions during charge-discharge cycles. These distortions accumulate strain and degrade crystallinity over time.
Led by Professor Shinichi Komaba, with Mr Kodai Moriya and Dr Shinichi Kumakura, the team investigated scandium (Sc) doping in the P’2 polytype of Na₂/₃MnO₂. “Previously, we discovered that Sc doping in P’2 Na₂/₃[Mn₁₋ₓScₓ]O₂ electrodes can improve the battery performance and long-term stability,” explains Professor Komaba. “However, the exact mechanism for this improvement remains unresolved.”
Their findings show that scandium doping preserves the cooperative Jahn-Teller distortion unique to the P’2 structure, while modulating particle size and crystal growth. This stabilises the cathode and mitigates side reactions with electrolytes. Notably, the 8% Sc-doped P’2 electrodes retained 60% capacity after 300 cycles in full-cell tests.
Importantly, scandium doping did not enhance performance in the P2 polytype, nor did similar cations like ytterbium or aluminium yield comparable results. This underscores the specific synergy between Sc and the P’2 structure.
“Since scandium is an expensive metal, our study demonstrates its feasibility in the development of batteries,” says Professor Komaba. “Moreover, beyond sodium-ion batteries, our study illustrates a new strategy to extend the structural stability of layered metal oxides involving the lattice distortion.”
The research was published in Advanced Materials on 12 September 2025.
Image: Scandium doping improves the structural stability of P’2 NaMnO2 while maintaining cooperative Jahn-Teller distortion, which significantly improves cycling stability.
