Surface Oxidation, Not Water, Harms Prussian Blue Batteries
Researchers have identified surface oxidation during dehydration as the cause of Prussian blue battery degradation, developing a new liquid-phase bubbling method to prevent it.
A Korean research team has pinpointed surface oxidation, not the presence of water itself, as the primary culprit behind performance degradation in Prussian blue cathode materials for sodium-ion batteries. These batteries are considered a promising next-generation energy storage technology due to the abundance and lower cost of sodium compared to lithium.
Prussian blue, an iron-based cathode material, inherently contains crystal water from its synthesis. While this water can lead to issues like electrolyte decomposition and reduced battery lifespan, conventional methods to remove it, such as high-temperature heat treatment, have paradoxically resulted in performance deterioration. The underlying cause of this degradation remained unclear until now.
The research team, led by Professor Changshin Jo at POSTECH, discovered through detailed surface analysis that high-temperature dehydration creates iron-oxygen (Fe-O) bonds on the Prussian blue surface. These bonds promote oxidation, accelerate electrolyte decomposition, and generate gas, ultimately compromising battery performance and stability.
To address this, the scientists developed a novel liquid-phase bubbling dehydration process. This method involves continuously injecting nitrogen gas into a non-aqueous solvent. As nitrogen bubbles pass through, they effectively remove crystal water while minimizing oxygen exposure, thereby suppressing surface oxidation. This process is akin to drying delicate fabric with a gentle breeze instead of harsh heat.
Using this new technique, the team successfully reduced the crystal water content in Prussian blue from approximately 12 wt.% to about 1 wt.% while significantly inhibiting surface oxidation. The treated material demonstrated reduced gas generation during operation and superior capacity retention after 100 charge-discharge cycles compared to conventionally treated samples. Furthermore, this process can be integrated directly into the electrode fabrication step, as it uses the same solvent, minimizing moisture reabsorption and enhancing long-term stability.
This research addresses a critical bottleneck in the development of Prussian blue sodium-ion batteries, a key alternative for energy storage. By identifying surface oxidation as the degradation mechanism during dehydration, rather than water removal itself, the team provides a pathway for more stable and durable battery materials. Their innovative liquid-phase bubbling method offers a gentle, integrated approach to material processing, potentially accelerating the commercialization of next-generation batteries for electric vehicles and grid storage.
Edited by the news editor with AI from the original report — please refer to the original source.