For decades, most batteries have been rigid, dry, and poorly suited to the demands of marine environments. These energy sources, while highly effective in controlled environments, are usually incompatible with water, which can cause corrosion, electrical short circuits, and a complete failure of the power source. However, researchers are taking a bold step toward changing the narrative surrounding batteries in wet environments. They are investigating flexible, yarn-like batteries that are not only water-resistant but also capable of functioning within saltwater.
A New Approach to Power
The need for adaptable, waterproof power sources in marine environments has long been recognized. People frequently work and play in oceans, estuaries, and other bodies of water—whether it’s through activities like fishing, kayaking, or offshore research. These environments require devices that are durable and can operate reliably even when exposed to saltwater. Enter the latest developments in flexible and seawater-compatible batteries: the latest efforts aim to transform the way we think about battery functionality.
The fundamental concept behind these advanced batteries is quite simple. Rather than preventing water from making contact with the battery, researchers are focusing on integrating seawater directly into the device’s power system. The latest findings, recently reported in ACS Applied Materials and Interfaces, present a yarn-like battery prototype that operates successfully when immersed in seawater. This research could lead to widespread applications such as lighting systems for fishing nets, energy for life jackets, and power sources for buoys. Imagine being able to rely on the very environment you’re working in to power your devices.
Creating the Seawater-Compatible Battery
The team behind this innovation is led by Yan Qiao, Zhisong Lu, and their colleagues. They had already pioneered the concept of a water-friendly battery using carbon fiber and cotton yarn for an exercise monitor, utilizing sweat from the human body as an electrolyte—a conductive liquid used in batteries. Sweat contains sodium, chloride, and sulfate ions, which made it ideal for this application. Drawing on that success, they turned their attention to an even more complex medium: seawater.
To create a battery that would work in seawater, the team began by thinking about what makes seawater a viable solution for use as an electrolyte. Sea water is naturally rich in ions such as sodium, chloride, and sulfate, which makes it capable of conducting electricity, just like sweat. By harnessing the power of seawater, they would eliminate the need for chemical electrolytes found in typical batteries—an exciting breakthrough, given the environmental implications of relying on natural, abundant resources instead of synthetic materials.
The team began by creating electrodes for the new seawater battery. They coated carbon fiber bundles with nickel hexacyanoferrate for the positive electrode (cathode) and polyamide for the negative electrode (anode). These coated bundles were then twisted together, creating the foundation for what would eventually become flexible, thread-like battery strands.
Constructing the Yarn-Like Battery
The researchers set out to create a seamless system where the battery could store and discharge energy, even while being exposed to water. To accomplish this, they wrapped the cathode string in a protective layer of fiberglass to provide structural integrity. They then carefully placed the wrapped cathode along with the unwrapped anode inside a nonwoven, permeable fabric. This fabric was essential because it serves as a shield to protect the components of the battery from wear and tear, while also allowing seawater to infiltrate and act as the conducting electrolyte. In essence, the permeable fabric ensured that the battery could still function underwater, taking advantage of the surrounding seawater instead of fighting against it.
The flexibility of the battery was critical for its application in real-world marine environments. Battery technologies often struggle in flexible formats because they can break under mechanical stress. The research team tested the yarn-like battery’s ability to withstand bending. To their delight, the battery retained most of its initial charging efficiency and storage capacity even after being bent more than 4,000 times. This flexibility allowed the battery to be used in dynamic conditions, such as those in the marine environment where materials frequently experience physical stress from waves, tides, and handling.
Real-World Applications and Proof of Concept
As a demonstration of their battery’s capabilities, the team assembled the yarn-like battery in two unique configurations: as a fishing net and as a woven fabric.
The fishing net prototype consisted of knotted strands of the flexible battery material. The researchers submerged the entire net in seawater to ensure it absorbed the electrolyte and was fully charged. Once the net absorbed enough seawater and charged up, it was able to power a 10-LED panel, effectively lighting up the fishing net. This prototype presents an exciting solution for the maritime industry, where large nets can be deployed in oceans, with LEDs providing illumination or possibly guiding boats, ships, or other devices, all without a need for traditional power sources. This could be particularly useful for applications such as search and rescue or fisheries, where a reliable, safe, and easy-to-integrate power source is required.
In another experiment, the team wove a rectangular piece of fabric using the same yarn-like battery material. This fabric was then submerged in a sodium sulfate solution and successfully powered a timer for over an hour, demonstrating its ability to perform more delicate operations that require a continuous and reliable energy supply. By integrating these batteries into fabrics, manufacturers could create smart fabrics that power various devices, making life jackets and wetsuits equipped with lights or communication tools a reality.
Potential Impact of Marine-Friendly Battery Technologies
These novel marine energy sources have the potential to dramatically change the way energy is used in water-based applications. From being able to provide continuous power to critical safety devices like life jackets and buoy systems, to enabling advanced technology integration on watercraft or research vessels, this flexible, seawater-powered battery could redefine power management in many industries.
Beyond practical applications in the fishing, research, or recreational boating sectors, the environmental and operational advantages of such technology cannot be overstated. Traditional batteries are often an environmental hazard when discarded, especially in marine environments. Creating batteries that can safely interact with seawater—and function efficiently in it—marks a major step toward environmentally conscious technology in oceans and estuaries.
The flexible battery prototype is not only durable and seawater-compatible but is also lightweight and versatile. Its potential to be woven, knit, or configured into various shapes could lead to an explosion in wearable technology, where energy becomes seamlessly integrated into fabrics, threads, and ropes used in marine environments. From the coating of fishing nets to the electrification of safety gear, the ability to power devices using the ocean’s natural resources opens up exciting opportunities for sustainable energy solutions in maritime fields.
Conclusion
The development of flexible, seawater-powered batteries marks a significant step forward in energy technology, particularly for marine applications. By leveraging seawater as an electrolyte, researchers have created an environmentally-friendly and adaptable power source ideal for use in oceans and estuaries. These yarn-like batteries open new possibilities for powering devices such as fishing nets, life jackets, and buoys, all without relying on traditional power sources. Their ability to endure bending and integration into fabrics adds to their versatility, allowing them to function effectively in diverse conditions. As research improves battery efficiency, storage capacity, and durability, seawater-powered batteries could become essential for a wide range of marine industries. This technology has the potential to transform how we generate and utilize energy in aquatic environments, creating more sustainable and practical solutions for industries that operate in or rely on water-based activities. The future of marine power systems looks increasingly bright with the promise of these innovative energy sources.
Reference: Yihao Jian et al, Constructing High-Performance Yarn-Shaped Electrodes via Twisting-after-Coating Technique for Weavable Seawater Battery, ACS Applied Materials & Interfaces (2024). DOI: 10.1021/acsami.4c16439