Scandium Improves Sodium Battery Life by Stabilizing a Manganese Cathode

A small material change delivers a longer lasting sodium cell

Researchers at Tokyo University of Science have improved the durability of a sodium-ion battery by replacing about 8 percent of the manganese in a layered oxide cathode with scandium. In a coin type full cell, the material retained roughly 60 percent of its initial capacity after 300 charge and discharge cycles, addressing a weakness that has limited sodium batteries in many uses.

The advance, described in research published in Advanced Materials, concerns the cathode, one of the battery's two electrodes. Its atomic structure must repeatedly accommodate sodium ions as the battery charges and discharges. When that structure deteriorates, the battery stores less energy.

The Tokyo team found that scandium helped one particular arrangement of sodium manganese oxide maintain its structure, reduced unwanted reactions with the electrolyte and improved resistance to moisture during handling. The strongest result came from a crystal form called P prime 2. The same benefit did not appear in the related P2 form.

Sodium's appeal begins with its abundance and wide geographical distribution, which can reduce pressure on costs and supplies. The manganese oxide chemistry examined here also avoids cobalt, a metal associated with price and ethical concerns. Durability remains a central tradeoff: sodium ions are relatively large and can strain the materials that hold them.

The study, supported by national research programs in Japan, focused on fundamental material behavior. Its practical promise is a cathode that can withstand repeated use more successfully, although the demonstration remains at the scale of a coin type cell.

Why sodium manganese oxide loses capacity

Layered sodium manganese oxides have attracted interest because they can store substantial amounts of charge. The P prime 2 form of Na2/3MnO2 is especially promising because manganese can switch between its +3 and +4 charge states. This reversible exchange of electrons, called a redox reaction, helps the battery store and release energy.

The difficulty is keeping the material intact through that process. After dozens or a few hundred cycles, capacity can fall as the crystal structure deteriorates and unwanted reactions accumulate at the surface of its particles. Sodium then has a harder time moving into and out of the cathode.

A major cause is the Jahn-Teller effect. When manganese is in the +3 state, the arrangement of its electrons stretches some bonds and compresses others. Surrounding atoms move in response, distorting the crystal lattice, the repeating framework that holds the material together.

Distortions become damaging when they occur unevenly and change repeatedly. Internal strain builds, tiny cracks can form, and the orderly atomic arrangement begins to break down. The result is declining capacity and efficiency as the battery undergoes more charging and discharging.

Why the arrangement of atomic layers matters

P2 and P prime 2 are polytypes of sodium manganese oxide. A polytype is a version of a material whose atomic layers are arranged differently, even though its chemical formula can be the same. That difference in arrangement changes how the material responds during battery operation.

In P2, the distortions associated with manganese tend to remain local and unpredictable. In P prime 2, they line up across many atoms in a cooperative pattern. This order can help the material, provided the underlying structure remains intact.

The Tokyo researchers therefore compared scandium additions in both forms and varied how much scandium they used. Their aim was to determine whether the added element could stabilize the coordinated distortions in P prime 2 and improve its useful life.

The comparison showed why the choice of crystal form matters alongside the choice of element. Scandium did not deliver the same improvement in P2, where distortions remained localized and the structure continued moving toward less favorable arrangements.

What the researchers changed

The strongest result came from P prime 2 Na2/3[Mn1-xScx]O2 with x near 0.08. In this formula, x describes the share of manganese sites occupied by scandium. A value of 0.08 means roughly 8 percent of those sites contain scandium instead of manganese.

Scandium entered the manganese layer and changed the local surroundings of the manganese ions. It also affected crystal growth, producing smaller particles and a more uniform internal structure. The doped material better preserved the cooperative distortion that defines P prime 2 instead of allowing that order to deteriorate.

Attempts to replace manganese with other trivalent metals, which have a +3 charge, did not produce similar gains. The result points to a particular fit between scandium's size and charge and the way the P prime 2 lattice organizes itself.

The team also found that a brief conditioning step before regular cycling further improved capacity retention. This pre-cycling treatment helped the electrode prepare for repeated operation, adding to the improvement achieved by the scandium substitution itself.

How scandium helps the structure keep working

In P prime 2, the distortions around manganese ions in the +3 state form a repeating pattern resembling a honeycomb. Scandium helps preserve that cooperative arrangement. The lattice can then expand and contract during charging and discharging while keeping its atoms in an orderly relationship.

A simple way to understand the change is to picture a structure flexing in a predictable pattern instead of bending unevenly until it cracks. The researchers' findings connect improved battery life with the preservation of that coordinated movement.

Smaller, more uniform particles offer another advantage: sodium ions have shorter distances to travel inside the solid. Easier movement through the cathode supports its operation as charge enters and leaves the battery.

The doped cathode also showed fewer unwanted reactions with the electrolyte, the medium through which ions move between electrodes. Such reactions can create resistive surface films that consume useful material and make it harder for the battery to deliver power. A cleaner interface between the cathode and electrolyte helps limit that damage.

Improved moisture resistance adds a manufacturing benefit. Powders must be handled and processed before a finished cell is assembled, and greater tolerance of moisture could help during those steps. Production would still require strict environmental controls.

What the full cell test showed

The researchers paired the scandium modified P prime 2 cathode with a hard carbon anode in a coin type full cell. A full cell uses both working battery electrodes together, making the pairing relevant to how a complete battery functions.

After 300 charge and discharge cycles, the cell retained about 60 percent of its initial capacity. Put simply, a battery beginning with 100 units of storage would have about 60 units left at that point, a loss of roughly 40 units. The result represented a clear improvement in cycle life compared with the undoped samples.

The electrodes also retained their crystallinity better than the controls. Their impedance, or resistance to the movement of electrical charge, increased more slowly. These observations supported the finding that scandium reduced harmful side reactions while helping the structure survive repeated operation.

The central finding is specific: scandium worked particularly well with the cooperative distortion of P prime 2. Chemistry and the arrangement of atomic layers need to be designed together. Adding the same element to a related structure did not automatically produce the same outcome.

An overview of the research, including the relationship between scandium and the coordinated distortion in P prime 2, is available through the PubMed study entry.

Other scandium cathodes show a related pattern

Research on other sodium cathode families has also found benefits from scandium. In NASICON type materials, which have a different structure from layered oxides, scandium has improved pathways for both sodium ions and electrons.

One example is scandium doped Na3MnTi(PO4)3. An optimized composition improved conductivity and sodium ion mobility while retaining about 93 percent of its capacity after 250 cycles at a modest operating rate. It retained about 88 percent after 500 cycles at a higher rate.

Another example is Na3V2(PO4)2F3 modified with scandium and covered with a carbon coating. That material showed strong performance at higher operating rates and retained about 90 percent of its capacity after 1,000 cycles at elevated current.

The studies used different testing procedures and measurements, so their percentages are not directly comparable. Their shared finding is that small scandium additions can help stabilize different structures and reduce polarization, the voltage losses that develop as a battery operates.

The layered oxide study adds a more specific lesson to that wider picture: preserving an organized distortion can be useful. The goal is to manage how a particular crystal changes during cycling so that it continues to function.

Scandium brings a cost and supply challenge

Scandium is scarce in concentrated deposits and is usually recovered as a byproduct of other mining and refining activities. Supply is limited and concentrated in a few countries. Recent export controls and wider geopolitical tensions have increased caution about relying heavily on individual regions for critical materials.

Scandium oxide prices are commonly quoted in the hundreds of dollars per kilogram. That creates an economic question for a battery technology whose appeal includes the abundance of sodium and the prospect of lower material costs.

Professor Shinichi Komaba, who leads the work at Tokyo University of Science, acknowledged the tradeoff while describing the broader value of the research:

Scandium is an expensive element, but our work demonstrates its potential to unlock long life sodium-ion batteries. The findings also suggest new design strategies for layered metal oxides beyond sodium systems.

The amount of scandium needed helps put the expense in context. Replacing a few percent of manganese adds a relatively small mass fraction of the expensive element to the cathode, which can limit its contribution to material costs.

Possible ways to use less include concentrating scandium near particle surfaces, where it could improve the interface with the electrolyte, combining smaller additions with protective coatings, or finding pairs of other dopants that reproduce its structural effect. These are routes for further research and development.

Projects in Australia, North America and other regions are working to expand scandium recovery as a byproduct. Higher output could ease price and supply pressures if demand rises.

Where more durable sodium batteries could be useful

Stationary energy storage is a promising application for sodium-ion technology because cost, safety and useful life often matter more than storing the maximum energy in the least weight. Batteries serving the electricity grid, buildings or communities face different weight constraints from batteries in vehicles.

A stable layered cathode with high capacity could reduce the amount of material required for each kilowatt hour of storage. That could improve competitiveness in grid connected systems, storage behind a customer's electricity meter and community installations.

Applications requiring many thousands of cycles with little capacity loss may also benefit from NASICON based cathodes. The range of sodium cathode structures offers different options depending on whether the priority is capacity, durability or performance at higher operating rates.

Transport is another area of activity. Several manufacturers have announced plans for sodium-ion cells in entry level vehicles and two wheelers. Performance at lower temperatures and charging behavior remain active research topics.

Further progress in cathode stability, electrolyte design and anode engineering will shape sodium's reach in mobility. A safer battery option with fewer resource constraints would have value if its performance continues to improve.

What must happen beyond the coin cell

The scandium modified material has been demonstrated in coin type full cells. Moving to stacked pouch cells or prismatic cells, the larger formats used in practical battery systems, would require uniform scandium distribution across larger production batches and close control of particle shape and size.

Manufacturers would also need compatibility with standard electrolyte mixtures and separators, the components that keep the electrodes apart while allowing ions to pass. Better moisture tolerance is encouraging for production yield, but careful handling and environmental controls would remain necessary.

Researchers could also search for less expensive ions that provide similar control of the lattice. Another possibility is to adjust vacancies, or empty atomic sites, and the ordering of manganese sites so that cooperative distortions remain stable without scandium.

Changes elsewhere in the cell could complement cathode design. Higher electrolyte salt concentrations or additives could help create more durable protective layers at electrode surfaces and reduce unwanted reactions. Improved hard carbon or alternative anodes could raise initial efficiency and stability over repeated use.

The research therefore offers both a material improvement and a design principle: the useful behavior of a battery depends on how its chemistry works with its crystal structure. Larger cells, manufacturing control, material costs and coordinated improvements to the other cell components are the next practical tests.

The Bottom Line

• Tokyo University of Science researchers retained about 60 percent of initial capacity after 300 cycles in a coin type full cell using a scandium modified sodium manganese oxide cathode.
• The strongest result came near 8 percent scandium substitution at manganese sites in the P prime 2 crystal form.
• Scandium helped preserve coordinated Jahn-Teller distortions, reduced unwanted electrolyte reactions and improved moisture tolerance.
• The same benefit did not appear in P2 or with the other trivalent metals tested. Brief electrode conditioning provided a further improvement.
• Related NASICON cathode studies also found gains from scandium, although different testing conditions limit comparisons.
• Scandium's expense and limited supply complicate scaling, while small additions and new byproduct recovery projects offer possible ways to manage those pressures.
• Stationary storage and entry level mobility are potential uses. Larger cell demonstrations, production control and further electrolyte and anode improvements remain necessary.