Flexible and Safe Batteries for the Technologies of Tomorrow

As the demand for sustainable energy storage continues to grow, new types of batteries are needed—not only for large-scale energy systems, but also for emerging technologies such as wearable electronics, soft robotics, and medical devices. These applications require batteries that are not only efficient, but also safe, flexible, and adaptable.

One promising approach is the development of hydrogel-based batteries. Hydrogels are soft, water-rich materials that can stretch, bend, and even self-heal. This makes them ideal for use in flexible devices and systems that need to conform to complex shapes—even those found in the human body.

However, early versions of these soft batteries faced important limitations. While they were mechanically flexible, their energy storage performance was relatively low. This was mainly due to the properties of traditional water-based electrolytes, which limit how much energy the battery can safely store and deliver.

A New Approach with Abundant Materials

To overcome these challenges, we are exploring new electrolyte concepts based on sodium, an abundant and low-cost alternative to lithium. Sodium offers a more sustainable pathway for future battery technologies, reducing dependence on scarce resources.

A key innovation in our work is the use of highly concentrated electrolytes, known as “water-in-salt” systems. In these systems, the balance between salt and water is carefully adjusted to make the electrolyte more stable and capable of operating at higher performance levels.

Combining Performance with Safety and Flexibility

We integrate these advanced electrolytes into hydrogel materials, creating a fully flexible, all-hydrogel battery system. The hydrogel not only provides mechanical flexibility, but also helps to safely contain the electrolyte, reducing the risk of leakage and improving overall stability.

This combination of materials offers several advantages:

• Enhanced safety, thanks to stable, water-based chemistry

• Flexibility and durability, enabling use in wearable and soft devices

• Sustainability, through the use of abundant sodium instead of lithium

Understanding and Improving Battery Performance

To optimize these systems, we study how the electrolyte behaves at a fundamental level—how ions move, how stable the system is, and how its performance changes under different conditions. These insights help us design better materials and improve battery efficiency and lifetime.

Towards the Next Generation of Energy Storage

Our research brings together safety, flexibility, and sustainability in a single battery concept. By advancing sodium-based hydrogel batteries, we are helping to enable a new class of energy storage technologies—designed not only for performance, but also for real-world usability in next-generation applications.