Nanoengineers Develop the First Printed, Rechargeable and Flexible Battery

The first printed battery that is rechargeable, stretchable and flexible has been developed by Nanoengineers at the University of California, San Diego.

The zinc batteries are capable of being used to power everything from solar cells to wearable sensors and various other kinds of electronics. The work has been published in the April 19^th, 2017 issue of Advanced Energy Materials.

The printed batteries were made stretchable and flexible by integrating a hyper-elastic polymer material developed from isoprene, one of the key ingredients in rubber, and a resin-like component called polystyrene. SIS is a substance that permits the batteries to stretch, in any direction, to twice their size, without suffering damage.

The ink that has been used to print the batteries has been produced from zinc silver oxide blended with SIS. Zinc batteries are generally not rechargeable even though they have been used for a long period of time. The Researchers made the batteries rechargeable by adding bismuth oxide.

This is a significant step toward self-powered stretchable electronics. We expect this technology to pave the way to enhance other forms of energy storage and printable, stretchable electronics, not just for zinc-based batteries but also for Lithium-ion batteries, as well as supercapacitors and photovoltaic cells.

Joseph Wang, Senior Author and Nanoengineering Professor, Jacobs School of Engineering, University of California, San Diego

The prototype battery developed by the team has almost 1/5 the capacity of a rechargeable hearing aid battery. However, it is cheaper, 1/10 as thick, and employs materials that are commercially available. A 3 Volt LED is powered by two of these batteries. The Researchers are currently working on enhancing the performance of the battery. Next steps involve expanding the use of the technology to a wide range of applications, such as fuel and solar cells; and then using the battery to power a variety of electronic devices.

Conventional screen printing techniques were used to produce the batteries—a method that considerably brings down the costs of the technology. Typical materials for a single battery cost just $0.50. A comparable commercially available battery that is rechargeable costs $5.00.

It is possible to directly print batteries on fabric or on materials that permit wearables to stick to the skin. Batteries can also be printed as a strip in order to power a device requiring more energy. They can be worn for a longer span of time and are also stable.

Making the batteries rechargeable

A molecule called bismuth oxide is the ingredient that makes the batteries rechargeable. This key ingredient prolongs the life of devices and allows them to recharge when mixed into the zinc electrodes of the battery. The concept of adding bismuth oxide to zinc batteries is considered to be a traditional practice in industry in order to enhance performance, but until recently, a rough scientific explanation for why this is done has not been provided.

In 2016, UC San Diego Nanoengineers headed by Professor Y. Shirley Meng addressed this question by published an in-depth molecular study. When zinc batteries discharge, their electrodes respond to the liquid electrolyte present inside the battery, generating zinc salts that dissolve into a solution. This ultimately short circuits the battery. Adding bismuth oxide prevents the electrode from losing zinc to the electrolyte. This guarantees that the batteries continue to function and can be recharged.

The work demonstrates the possibility of using minimal amounts of additives, such as bismuth oxide, in order to modify the properties of materials.

Understanding the scientific mechanism to do this will allow us to turn non-rechargeable batteries into rechargeable batteries—not just zinc batteries but also for other electro-chemistries, such as Lithium-oxygen.

Professor Y. Shirley Meng, Director, Sustainable Power and Energy Center, University of California, San Diego

From Innovation to Market

Rajan Kumar, a Nanoengineering Ph.D. Student at the Jacobs School of Engineering, is a Co-first Author on this Advanced Energy Materials paper. He and Wang are heading a team working on commercializing aspects of this work. The team is one of five to be selected to join a new technology accelerator at UC San Diego. The technology accelerator is operated by the UC San Diego Institute for the Global Entrepreneur, which is a partnership between the Jacobs School of Engineering and Rady School of Management.

Kumar is excited at the very outlook of taking advantage of all that can be offered by the IGE Technology Accelerator.

“For us, it’s strategically perfect,” said Kumar, referring to the $50,000 funding for prototype enhancements, the entrepreneurship mentoring, and the focus on prototype testing with a strategic partner.

Kumar expresses his confidence on his team’s innovations, which include the potential to replace coin batteries with stretchable, thin batteries. Making the correct strategic moves now is essential for commercialization success.

It’s now about making sure our energies are focused in the right direction.

Rajan Kumar, Nanoengineering Ph.D. Student, Jacobs School of Engineering, University of California, San Diego

Besides the IGE Technology Accelerator, the team was also recently selected to take part in the NSF Innovation-Corps (I-Corps) program at UC San Diego, also administered by the Institute for the Global Entrepreneur. One of the main tenets of the I-Corps program is to help startup teams certify their business models and target markets early in the commercialization process. Through NSF I-Corps, for instance, Kumar has already commenced interviewing potential customers and this has helped the team to improve the focus of its commercialization strategy.

Kumar, through these programs, concentrates on leading the team through a series of milestones in order to enable them to best position their innovations to improve, "Both what to build and who to build it for,” he said.