As the world searches for alternatives to lithium-ion batteries, sodium-ion batteries are emerging as a promising solution.
Sodium is far more abundant in the Earth’s crust than lithium, making these batteries cheaper and more sustainable.
But there has been one big challenge: keeping them stable and reliable over many charge and discharge cycles.
A major hurdle lies in the choice of cathode material, which largely determines the performance of a battery.
One of the most promising options is a layered compound called sodium manganese oxide (Na₂/₃MnO₂).
It offers high capacity without relying on expensive or rare elements. Unfortunately, it also tends to lose performance quickly with repeated use.
The reason comes down to manganese.
When sodium ions move in and out of the cathode during charging and discharging, manganese atoms switch between two oxidation states—Mn³⁺ and Mn⁴⁺. When Mn³⁺ forms, it distorts the surrounding atomic structure, a process known as the Jahn-Teller effect.
These repeated distortions strain the material, eventually breaking down its crystal structure and leading to rapid capacity loss.
To overcome this problem, researchers have been experimenting with replacing some of the manganese with other metals.
A team led by Professor Shinichi Komaba at Tokyo University of Science has now shown that adding small amounts of scandium (Sc) can dramatically extend the life of sodium-ion batteries—at least for a certain type of cathode material.
Their study, published in Advanced Materials in September 2025, focused on two versions of sodium manganese oxide, known as the P2 and P’2 polytypes. These two forms look similar but behave differently at the atomic level.
In the P2 type, distortions happen in a scattered, localized way. In the P’2 type, distortions line up in a cooperative, long-range order.
The team discovered that scandium doping works only in the P’2 type. By carefully adding about 8% scandium, they were able to shrink particle size, control crystal growth, and maintain the ordered distortions that give the material stability. The doped material resisted structural collapse, reduced unwanted side reactions with the electrolyte, and even showed improved resistance to moisture.
In battery tests, scandium-doped P’2 electrodes kept much of their structure intact even after hundreds of cycles. A coin-sized full cell built with this material retained 60% of its capacity after 300 charge-discharge cycles—an impressive improvement over non-doped versions.
Interestingly, attempts to use other metals such as aluminum or ytterbium did not show the same benefit, highlighting the unique role of scandium. Although scandium is expensive, the results suggest that even small amounts can greatly extend battery life, making it a feasible strategy.
According to Professor Komaba, this approach not only points the way toward better sodium-ion batteries but could also inspire new ways to strengthen other types of layered metal oxide batteries.
With further development, scandium could help make large-scale, cost-effective, and durable sodium-ion batteries a reality.
