Dongguk University Develops Ultra-Thin Solid-State Battery Technology to Enhance Battery Stability and Energy Density

A battery with a thickness of just 2.77 microns could provide power solutions for wearable electronics, micro-sensors, and medical devices. This technology was developed by a research team at Dongguk University in South Korea, utilizing a film platform that employs tin and carbon layers to control lithium deposition and reduce lithium loss during charging and discharging. The research was led by Professor Kim Hyun-sook from the Department of Energy and Materials Engineering, where researchers combined the coating with additional lithium reserves to enhance battery stability. The university announced the research findings on November 3.

Advantages of Anode-Free Design

Addressing the issue of uneven lithium deposition, solid-state batteries replace liquid electrolytes with solid materials, providing potential safety and energy density advantages. However, uneven lithium plating and stripping can lead to unstable operation. The anode-free design partially addresses manufacturing challenges, allowing lithium to deposit from the cathode onto the current collector, forming the anode, simplifying the manufacturing process and increasing volumetric energy density, especially in thin-film batteries. However, during the stripping process, lithium may become electrically isolated, forming "dead lithium," or lose contact with the solid electrolyte. These processes reduce the available lithium in subsequent cycles and affect battery capacity.

The team at Dongguk University investigated whether coating the current collector could help control this process.

Professor Kim stated, "Our intermediate layer acts as a seed for lithium nucleation, promoting uniform lithium plating, reducing lithium loss, and improving the reversibility of repeated charge and discharge." The researchers screened coatings of pure carbon, pure metal, and metal/carbon combinations. Results showed that using a tin/carbon bilayer coating on a copper current collector configuration performed best across various tests, demonstrating good lithium deposition and interface stability. The two layers of materials play different roles, with tin lowering the energy barrier for lithium nucleation, aiding in the initial formation of lithium at the interface. The carbon cover layer regulates subsequent growth, potentially limiting uneven deposition and stabilizing the region of interaction between tin and lithium.

The research team also deposited a thin layer of metallic lithium on the coated current collector. This pre-lithiation step creates a reserve to compensate for lithium loss during the initial cycle. During the first lithium plating process, a three-dimensional textured region containing tin and lithium-tin was formed. The researchers noted that this structure can adapt to volume and shape changes in subsequent cycles, helping to maintain contact and stability.

Prospects for Ultra-Thin Battery Applications

The ultra-thin platform demonstrates energy storage potential, with completed batteries combining lithium vanadium oxide cathodes, lithium phosphorus oxynitride solid electrolytes, and coated copper current collectors. At the 100th cycle, its volumetric energy density reached 235.13 Wh/L, measured at a rate of 0.01 C. Professor Kim stated, "Our approach shows how interface engineering and lithium storage management can improve anode-free thin-film batteries." He added, "This method can support the development of ultra-thin batteries for wearable electronics, IoT sensors, and medical devices, as well as scalable anode-free all-solid-state battery (ASSB) applications for industrial-scale power."

This research identifies a method for managing lithium deposition and supply in ultra-thin battery architectures. The findings were published in the journal Advanced Energy Materials.