A team from Tokyo University of Science (TUS) has identified a structural mechanism by which adding small amounts of scandium to layered sodium manganese oxide cathodes slows degradation, which typically limits the life of sodium-ion batteries.
A new materials study from Japan shows that targeted scandium substitution in layered sodium manganese oxide can reduce the lattice voltage responsible for rapid capacity decay in sodium ion battery cathodes.
The research focuses on layered sodium manganese oxide (Na₂⁄₃MnO₂), a high-capacity cathode material that is widely studied as a cheaper alternative to lithium-ion chemistry due to its abundance of sodium. Although Na₂⁄₃MnO₂ offers strong initial performance, it is limited by rapid capacity decay during repeated charge-discharge cycles.
The study, led by Prof. Shinichi Komaba of Tokyo University of Science, investigates how replacing small amounts of scandium at manganese sites affects two structural variants of the material, known as P2 and P′2 polytypes. Capacitance loss in these cathodes is mainly caused by Jahn-Teller distortion associated with changes in the oxidation state of manganese during cycling, which causes structural stress and crystallinity loss over time.
According to the researchers, scandium doping selectively improves the cycling stability of the P′2 polytype, which exhibits cooperative Jahn-Teller deformation over long distances. Structural analysis showed that scandium-modified P′2 Na₂⁄₃[Mn₁₋ₓScₓ]O₂ retained its crystal structure during cycling, reduced particle size, and suppressed side reactions with liquid electrolytes by forming a more stable cathode-electrolyte interface.
In half-cell testing, the P′2 material with 8% scandium content provided the strongest performance, maintaining structural integrity and capacity during extended cycling. The same doping strategy did not improve the stability of the P2 polytype, indicating that the effect depends on the presence of cooperative lattice distortion rather than simple metal substitution. Doping with other cations, including ytterbium and aluminum, did not produce comparable results.
The team also reported improved moisture resistance and additional benefits from the pre-cycling treatment. In coin-type full-cell tests, the 8% scandium-doped P′2 cathode retained approximately 60% of its capacity after 300 cycles.
The article, “Unique impact of scandium doping on the electrode performance of P′2 and P2 type Na₂⁄₃MnO₂”, was recently published in Advanced materials. It describes the mechanism by which scandium stabilizes the deformed lattice without suppressing the electrochemical activity of manganese. The findings suggest a route to longer-lasting sodium-ion batteries, although the authors note that the cost of scandium could limit large-scale deployment, the scientists said.
The study was conducted by researchers from Tokyo University of Science and supported by funding from the Japanese Ministry of Education, Culture, Sports, Science and Technology, the Japan Science and Technology Agency and the Japan Society for the Promotion of Science.
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