Development of a new concept reserve battery that can be folded like paper and preserved long-term

Research results of the team led by Professor Kim, Gyu-tae are introduced on the website of the Royal Society of Chemistry

It is expected to be used not only as a flexible device, but also as an emergency power source for marine rescue, the military, and disaster recovery.

▲ From the left, Professor Kim, Gyu-tae (co-corresponding author), Research Professor Kim, 

Do-hyun (first author, co-corresponding author), and Na, In-yeob (co-author)

A new concept of reserve battery, which can be preserved long-term and folded like paper, has been developed and is becoming a hot topic.

The new concept reserve battery developed by a research team including Research Professor Kim, Do-hyun (first author/corresponding author) and Professor Kim, Kyu-tae (co-corresponding author) of the Department of Electrical Engineering at the College of Engineering was introduced under the title of ‘Giving longer life to wearable batteries’ in the Journals Highlights section of the Royal Society of Chemistry (RSC) website.

The Journals Highlights introduces papers selected by their publishing department from among all the papers in the journals published by the Royal Society of Chemistry. It evaluated the significance of this study from an objective standpoint, introducing the development of a new reserve battery concept by scientists from Korea University in South Korea that simultaneously addresses flexibility and long-term preservation of capacity.

- Paper title : Foldable water-activated reserve battery with diverse voltages

- Authors : Kim, Do-hyun, Na, In-yeob, Lee, Duck-hyun and Kim, Gyu-tae

- Journal : RSC Advances, 2020, 10, 402-410 (DOI: 10.1039/c9ra09401f)

With the advent of wearable and foldable devices, flexible power generating batteries are also required. Much research has been conducted on flexible batteries in this ever-changing environment, and most of that has focused on lithium-ion batteries. Lithium-ion batteries, if not used for a long period, unavoidably naturally self-discharge and eventually become unable to produce electricity. Therefore, after charging and installing a lithium-ion battery in a device such as an emergency flashlight of low use frequency, the electricity cannot be used when required if too much time has passed.

A reserve battery means a battery that is not normally activated but immediately generates electricity by injecting electrolyte into the battery when necessary. In this way, the battery can avoid the self-discharge phenomenon characteristic of existing batteries. Despite the advantages, this idea has not received much attention. Since the shape still conforms to the structure of a typical battery, making it flexible and foldable has long been a challenge.

This study demonstrated how to realize a new concept reserve battery that can retain charge for a long time and be folded like paper. The battery developed by the research team uses aluminum metal as the negative electrode and a paper electrode made of carbon nanotubes and cellulose as the positive electrode.

The specific operation principle is as follows. Electrolyte is injected through the hole in the surface of the battery to activate it. Then, the battery uses air as fuel to convert the aluminum metal used as the cathode into aluminum hydroxide. Electricity is generated from the electrons produced by this process. Various voltages were generated depending on the type of electrolyte injected, and it was possible to confirm the stability of the electric power generation even when seawater was injected. Furthermore, it was possible to confirm stable electricity production characteristics as per the original state even after the battery was folded like paper. In the future, the battery is expected to be used not only as a power source for flexible devices, but also as an emergency power source for offshore rescue, the military, and disaster recovery.

▲Figure 1. Detailed structure of foldable reserve battery

▲Figure 2. Commercially available LED lamps using activated foldable batteries.