Proving the Business Case for the Internet of Things

Korean researchers develop stretchable battery for medical wearables

Steve Rogerson
January 30, 2018

Researchers in South Korea have developed a stretchable rechargeable battery that can be used in medical wearables.
The team from the Ulsan National Institute of Science & Technology (Unist) has developed a highly stretchable rechargeable lithium-ion battery (ARLB) based on aqueous electrolytes.
The development of stretchable battery materials that mimic the functions of nature has emerged as a highly interesting research area, necessary for the next wave of wearable electronics.
The Unist researchers came up with a bio-inspired Jabuticaba-like hybrid carbon-polymer (HCP) composite that was developed into a stretchable current collector using a simple and cost-effective process. Using the HCP composite as a stretchable current collector, the research team developed the battery.
This breakthrough has been led by Professor Soojin Park (pictured second from the left) from Unist’s School of Energy & Chemical Engineering in collaboration with Professor Kwanyong Seo (third from left) and Professor So Youn Kim (second from right). Also pictured are researchers Jeonghwan Park (far left), Dong Hyup Kim (front centre) and Woo-Jin Song (far right).
Stretchable electronic devices have recently attracted attention as next-generation devices due to their immense flexibility. The increasing interest and demand of flexible electronics has fuelled the search for highly stretchable electrodes with high mechanical durability and high electrical conductivity during deformation. Although many methods have been proposed for these electrodes, none of them has managed to achieve simultaneously high stretchability for the electrodes and a scalable manufacturing process.
Professor Park solved such problems using a conductive polymer composite, composed of Jabuticaba-like hybrid carbon fillers containing carbon nanotubes and carbon black in a simple process. The shape of this structure resembled that of a Jabuticaba tree, the Brazilian grape tree.
The research team observed that the HCP composite is found to retain its electrical conductivity, even under high strain rates. This makes it suitable for use in highly stretchable aqueous Li-ion batteries.
“Our findings are expected to expand the number of stretchable nanocomposites with electrochemical and mechanical properties available for use in a wide variety of applications,” said Professor Seo, who was in charge of the fabrication of stretchable current collectors.
A detailed analysis of the percolation behaviour of the conductive filler within the composite was done using an in situ SAXS measurement under stretching, which revealed that the different types of carbon in the filler led to a formation of highly interconnected co-supporting networks. Professor Kim led the in situ SAXS experiments.
SAXS is a highly useful technique for measuring the behaviour of nanofillers in polymer matrices. Besides, the research team has, for the first time, developed stretchable ARLB as a stretchable power source, using the HCP composite as a stretchable current collector and they have delivered stable power to an LED even under 100% strain.
“This study is expected to facilitate the design of stretchable nanocomposites with optimised electrochemical and mechanical properties for use in energy storage devices and stretchable electronics,” said Professor Kim.
This study has been supported by the Center for Advanced Soft-Electronics funded by the Ministry of Science, ICT & Future Planning as a Global Frontier Project and the 2017 Research Fund of Unist. The work wasn published in the January 2018 issue of Advanced Energy Material.