Flexible Energy: The Science and Applications of Stretchable Batteries

By Taha KhanReviewed by Lexie CornerAug 7 2024

Modern electronic devices are becoming smaller, lighter, and more adaptable, requiring flexible energy solutions. In this context, stretchable batteries have emerged as a new class of energy storage devices designed to conform to various shapes and withstand significant deformation without compromising performance.^{1, 2}

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Science Behind Stretchable Batteries

Traditional battery components, such as electrodes, separators, and electrolytes, are typically rigid and brittle. Researchers have developed novel materials and fabrication methods to achieve stretchability. The core materials enabling stretchability in these batteries include elastomers, which are highly flexible polymers, and conductive inks made from materials like silver nanowires or carbon nanotubes.

These components allow the battery to maintain electrical conductivity even when deformed. Moreover, the design often incorporates serpentine or wavy structures that can elongate and compress without breaking.³

The methods used to produce these stretchable batteries often involve microfabrication techniques that precisely position these materials into stretchable configurations and encapsulation methods that protect the battery components while allowing flexibility. Instead of traditional liquid electrolytes, gel or polymer electrolytes are used to enhance flexibility and safety.^1-3

The main features of stretchable batteries are their ability to stretch, bend, and twist while maintaining functionality. This flexibility allows numerous applications, particularly in wearable electronics, where they can conform to the contours of the human body without causing discomfort. Their improved durability and resilience to physical stress make them ideal for environments where conventional batteries would fail.^{2, 3}

Applications in Wearable Technology

Traditional batteries, with their rigid and bulky form, have always been a limiting factor in developing truly adaptable and comfortable wearable devices. Stretchable batteries offer energy solutions that can flex, bend, and stretch with the human body, significantly enhancing the wearability and functionality of devices and allowing for more ergonomic and less obtrusive designs.

In recent years, wearable technology has exponentially grown due to consumer demand for health monitoring, fitness tracking, and smart clothing. Stretchable batteries are central to this growth as they offer a power solution that conforms to the human body's contours.^4-6

Fruit-based, Degradable Stretchable Battery

In a 2021 study, researchers developed a stretchable and fully degradable battery utilizing eco-friendly materials for wearable electronics. This novel battery, composed of fruit-based gel electrolytes and cellulose paper electrodes, represents a significant advancement in sustainable energy storage.

It operates effectively under mechanical deformations, such as bending, twisting, and stretching, which are common in wearable devices. The battery's stretchability, achieved through kirigami patterns, allows it to endure up to 24.6 % strain while maintaining performance.⁶

It powers various electronic devices, including LEDs and health-monitoring sensors, demonstrating its practical application in wearable technology. The battery degrades completely in a phosphate-buffered saline/cellulase solution, emphasizing its environmental friendliness and potential for future applications in sustainable and flexible electronics.⁶

Wearable Device Innovation

In a 2022 study, researchers made significant progress in developing stretchable batteries for wearable devices. They introduced a novel approach combining biodegradable materials with engineered stretchability, utilizing kirigami-patterned magnesium and molybdenum metal foils.

This design ensures both high power output and flexibility, achieving a peak power output of 196 µW cm^-2 and an energy density of 1.72 mWh cm^-2. The batteries can reversibly stretch up to 35 % in uniaxial and 20% in biaxial directions.⁷

These improvements make the batteries suitable for applications such as powering biomedical sensor patches that monitor sodium levels in sweat. This advancement promises a more sustainable and adaptable solution for wearable electronics, integrating high performance with environmental responsibility.⁷

Comprehensive Overview of Physical Characterization Techniques for Lithium-Ion Battery Materials in R&D and Manufacturing

Impact on Medical Devices

The healthcare industry has benefited significantly from stretchable batteries. Implantable medical devices, such as pacemakers, require reliable power sources that are both safe and flexible. Stretchable batteries provide biocompatible solutions for these applications. Moreover, their flexibility allows for easier implantation and removal, reducing surgical risks.^{7- 9}

Stretchable batteries can also be used in wearable medical devices to monitor vital signs, detect health conditions, and deliver therapeutic treatments. For example, flexible patches equipped with stretchable batteries can continuously monitor heart rate, blood pressure, and skin temperature, providing valuable data for disease management and prevention.^{7, 9}

Stretchable Battery Powers a Self-Adapting Wound Dressing System

In a 2022 study, researchers developed a fully stretchable magnesium–air battery using dual-ions-conducting hydrogels, demonstrating its application in medical devices. Specifically, the battery powers a self-adapting wound dressing system, which adjusts antibiotic delivery based on real-time wound conditions.⁹

This innovation overcomes traditional limitations by providing both flexibility and stable performance under mechanical deformation. The stretchable battery's biocompatibility and durability under stretching and bending make it ideal for skin-integrated electronics and personalized medical devices, showing potential for future healthcare monitoring and treatment applications.⁹

Future Outlooks

Stretchable batteries are rapidly evolving, with researchers continuously developing new materials, fabrication techniques, and designs. Future advancements are expected to lead to even higher energy density, longer lifespans, and improved stretchability and safety. One major area where stretchable batteries can make a significant difference is the medical field. Enhancements in biocompatible materials will expand the use of stretchable batteries in these applications in the future.

Similarly, stretchable batteries can provide breakthroughs in the sports and fitness industry by providing more accurate and comprehensive real-time data, enhancing athletic performance and health monitoring.

As research and development progress, we can expect even more remarkable advancements in this field.

References and Further Reading

1. Liu, W., Song, M. S., Kong, B., Cui, Y. (2017). Flexible and stretchable energy storage: recent advances and future perspectives. Advanced materials. https://doi.org/10.1002/adma.201603436
2. Mackanic, D. G., Kao, M., Bao, Z. (2020). Enabling deformable and stretchable batteries. Advanced Energy Materials. https://doi.org/10.1002/aenm.202001424
3. Kong, L., Tang, C., Peng, HJ., Huang, JQ., Zhang, Q. (2020). Advanced energy materials for flexible batteries in energy storage: A review. SmartMat. https://doi.org/10.1002/smm2.1007
4. Song, WJ. (2019). Recent progress in stretchable batteries for wearable electronics. Batteries & Supercaps. https://doi.org/10.1002/batt.201800140
5. Zhai, Q., Xiang, F., Cheng, F., Sun, Y., Yang, X., Lu, W., Dai, L. (2020). Recent advances in flexible/stretchable batteries and integrated devices. Energy Storage Materials. https://doi.org/10.1016/j.ensm.2020.07.003
6. Wang, Z., et al. (2021). Fully transient stretchable fruit‐based battery as safe and environmentally friendly power source for wearable electronics. EcoMat. https://doi.org/10.1002/eom2.12073
7. Karami‐Mosammam, M., Danninger, D., Schiller, D., Kaltenbrunner, M. (2022). Stretchable and biodegradable batteries with high energy and power density. Advanced Materials. https://doi.org/10.1002/adma.202204457
8. Wang, S., Cheng, T., Zhang, YZ., Wu, X., Xiao, S., Lai, WY. (2022). Deformable lithium-ion batteries for wearable and implantable electronics. Applied Physics Reviews. https://doi.org/10.1063/5.0117252
9. Huang, X., et al. (2023). Stretchable magnesium–air battery based on dual ions conducting hydrogel for intelligent biomedical applications. InfoMat. https://doi.org/10.1002/inf2.12388

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