Sungkyunkwan University (President Jibeom Yoo) and a research team led by Prof. Seongpil An from the SKKU Advanced Institute of Nanotechnology (SAINT) has recently  developed a flexible lithium-ion battery with high energy density (208 Wh kg-1) and high power density (1,048 W kg-1), based on a three-dimensional (3D) percolative metal microweb structure. This breakthrough offers promising applications in a wide range of flexible devices and a power source for electric vehicles.

Flexible batteries are a cornerstone technology for wearable electronics, capable of maintaining electrochemical performance under physical deformation. However, existing commercial lithium-ion batteries face safety issues, such as short circuits and potential explosions when subjected to mechanical deformation. To address these challenges and enhance both flexibility and energy density, prior studies have focused on the development of 3D electrode architectures. Nevertheless, conventional electrode coating methods have struggled to preserve their structures, thus limiting their performance benefits. In this study, the research teams have fabricated an ultra-lightweight flexible current collector based on a 3D percolative metal microweb via electrospinning and electroplating techniques. Furthermore, 3D electrode structure-based flexible lithium-ion battery with enhanced energy and power densities has been developed by employing electrostatic spray coating technology. Through two-dimensional modeling and electrochemical characterization, they identified significant enhancements in lithium-ion diffusion and electron transfer rate within this structure. Additionally, by incorporating a polymer gel electrolyte, they have developed a flexible all-solid-state lithium-ion battery that maintained operational stability even under mechanical deformation and cutting, demonstrating exceptional robustness. These advancements are expected to applicable to wide array of cutting-edge devices, including virtual and augmented reality, the metaverse, healthcare, and medical devices.

※ Traditional Electrode Coating Process: Slot die coating, a technique used to apply solutions, slurries, hot melt, or extruded thin films onto flat substrates.

     ※ Electrospinning: A fiber production method that uses electric force to draw charged threads of polymer solutions or polymer melts up to fiber diameters in the order of some hundred nanometers.

     ※ Electrostatic spraying: A voltage-driven process governed by the electrohydrodynamic phenomena where particles are made from a polymer solution.

Prof. An's research team (1st author, research professor Dr. Hongseok Jo) developed a flexible electrode based on 3D percolative metal microweb to address the inherent limitations of flexibility and energy density in conventional two-dimensional (2D) flat electrodes. This novel 3D microweb structure is more than four times lighter than traditional two-dimensional electrodes and exhibited remarkable mechanical durability, with less than a 2% change in electrical properties after more than 3,000 cycles of mechanical deformation. The 3D architecture significantly increased the surface area in contact with the electrolyte and reduced electron transfer distances, l resulting in over six-fold and four-fold improvements in lithium-ion diffusion and electron mobility, respectively, compared to conventional 2D structures. This is verified through 2D modeling and electrochemical analysis. This led to the realization of a flexible lithium-ion battery with energy density (208 Wh kg-1) and power density (1,048 W kg-1) that exceeds the performance of existing commercial lithium-ion batteries by more than double. Additionally, the all-solid-state flexible lithium-ion battery, utilizing a polymer gel electrolyte, maintained stable voltage even after undergoing significant mechanical deformations, such as bending and cutting, thereby ensuring both safety and operational stability. This research provides a significant breakthrough in the development of next-generation flexible electronic devices, offering a crucial solution to the limitations of existing battery technologies.

Prof. An, the corresponding author of this study, stated, “Recently, research and development in battery system architecture have been actively pursued. Therefore, innovative advancements in battery architecture must continue in the future through active knowledge exchange between researchers across various fields.”

Lastly, the 1st author of this study, research professor Hongseok Jo, expressed his intention, “These 3D percolative metal microweb-based flexible electrode exhibits ultra-lightweight and high specific area, which significant contribute to improved energy- and power-densities.  The unique architecture is also expected to effectively dissipate heat generated during electrochemical reactions. I believed that this approach offers a promising solution to address recent concerns related to overheating and the risk of explosion in lithium ion batteris.”

I believed that this approach offers a promising solution to address recent concerns related to overheating and the risk of explosion in lithium ion batteris.”

This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) RS-2023-00211303, RS-2023-00247975, and 2022M3H4A408507611.

This study was published on Aug. 13th in Advanced Materials (IF: 27.4), one of the world-renowned academic journals in the top 2.2% of the material science field.

※ Title : Percolative Metal Microweb-Based Flexible Lithium-Ion Battery with Fast Charging and High Energy Density

(Journal: Advanced Materials, https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202407719)

▲ Schematic of fabrication process of high-energy/-power density flexible lithium-ion batteries based on 3D percolative metal microweb, and the properties of the developed electrode

▲ Half-cell performance results of 3D electrodes, including electrochemical and simulated analysis, including C-rate performance, cycling test, lithium ion diffusion, electron transfer, and overpotential

▲ Performance of 3D electrode-based full cell and polyer gel electrolyte-based all-solid-state flexible lithium ion battery.