A team of Chinese researchers has enhanced the performance of flexible sodium-ion batteries using a bio-inspired technique. This technique involves the methylation of the hydrogel’s structural polymer, which increases salt stability and improves battery capacity and cycling performance.
Sodium-Ion Batteries: A Promising Alternative
Sodium-ion batteries are a promising alternative to Lithium-ion batteries. They are cheaper and more eco-friendly. However, they require the development of new components, including the electrolyte. In thin, flexible batteries, the electrolyte often takes the form of a hydrogel. These flexible materials absorb dissolved sodium salts and conduct ions.
Overcoming Hydrogel Challenges
Despite their suitability, hydrogels face a challenge: phase separation and salting out at high salt concentrations. Guanglei Cui and his team from the Chinese Academy of Sciences have found a solution. They modified a hydrogel to absorb more salt in a stable and secure manner.
The Role of Methylation
The team used methylation, a technique nature uses to regulate water- and salt-binding in large biomolecules. Methylation ‘caps’ amine and amide groups, making them less accessible for water molecules. This prevents salting out and leads to the breakdown of the electrolyte.
Improved Battery Performance
The methylated hydrogel absorbed more salt than the original variant. It remained transparent and stable even at record-high salt concentrations. The higher salt content expanded the electrochemically usable voltage range of the cell. The team also observed better cycling stability and greater capacity in the assembled battery cell.
The simple polyamide methylation technique could also be suitable for other technologies, such as drug development. It could make hydrogels more resistant to salts and therefore more stable.
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