"Thick Yet Highly Flexible" Paves the Way for Commercialization of Next-Generation Flexible Batteries

“We developed thick yet highly flexible electrodes, enabling the production of 3D free-form batteries. This marks a promising step toward the commercialization of next-generation flexible batteries tailored to complex product shapes.”

Hyun Seung-min (left) and So Hye-mi (right), Ph.D. Photo by Korea Research Foundation

The National Research Foundation of Korea announced on the 25th that Dr. Seungmin Hyun and Dr. Hyemi So’s research team at the Korea Institute of Machinery and Materials successfully developed thick flexible electrodes for secondary batteries by utilizing stainless steel fibers as 3D current collectors, achieving higher energy density than existing flexible batteries.

The current collector is a 10μm-thick film that contacts the battery’s internal electrodes (anode and cathode). It physically secures the electrodes and facilitates electron movement during charging and discharging. Flexible batteries refer to energy storage devices designed to bend or stretch without performance degradation.

Recently, the demand for flexible batteries has surged due to the expansion of wearable devices and smart gadgets markets. However, existing technologies face limitations in simultaneously achieving high energy density and mechanical flexibility.

In particular, using thick electrodes in flexible batteries hinders the movement of electrons and ions, leading to performance degradation and loss of flexibility. Securing both high energy density and mechanical flexibility in thick electrodes has been a critical challenge for the commercialization of flexible batteries.

To address this challenge, the research team developed high-performance flexible batteries by combining lightweight fibrous current collectors with porous electrode structures.

They realized thick and flexible electrodes by forming a porous dual-continuous structure through a thermally induced phase separation process. Thermally induced phase separation involves molding a uniformly mixed molten polymer solution at a temperature above the polymer’s melting point into a film, then cooling it to induce phase separation between the polymer and active materials.

The team reinforced interfacial adhesion, bending durability, and electrical conductivity by incorporating stainless steel fiber reinforcement.

The secondary battery electrodes developed through this process operated without performance degradation even when bent at right angles (minimum bending radius of 3 mm), demonstrating superior performance compared to existing flexible batteries.

Most importantly, the fibrous current collector forms a network with the electrode materials, allowing application to any free-form curved surface. This enables the production of 3D free-form batteries that are difficult to manufacture with conventional electrode structures, according to the research team.

Dr. Seungmin Hyun and Dr. Hyemi So stated, “The electrodes developed by our team simultaneously realize high energy density and flexibility, laying the foundation for the commercialization of next-generation flexible batteries. In particular, the ability to produce 3D free-form batteries is expected to enable the development of batteries for complex product shapes demanded by the industry.”

Meanwhile, this research was conducted with support from the Nano and Materials Technology Development Project promoted by the Ministry of Science and ICT and the National Research Foundation of Korea. The research results were published on the 2nd of last month in the international journal Advanced Fiber Materials.