A battery just 2.77 micrometers thick could provide a way to power wearable electronics, tiny sensors and medical devices. The thin-film platform, developed by a team at Dongguk University in South Korea, uses tin and carbon layers to control lithium deposition and reduce lithium loss during charging and discharging.
Led by Professor Hyun-Suk Kim from the Department of Energy and Materials Engineering, the researchers combined the coating with an additional lithium reserve to improve battery stability. The university announced the results on November 3rd.
Combating uneven lithium deposits
Solid-state batteries replace liquid electrolytes with solid materials and offer potential advantages in safety and energy density. However, uneven lithium plating and removal can destabilize their operation.
Anodeless designs address part of the manufacturing challenge by allowing lithium from the cathode to deposit onto a current collector during the initial charging process, forming the anode. This architecture can simplify manufacturing and increase volumetric energy density, especially for thin-film batteries.
However, lithium can be electrically isolated, resulting in “dead” lithium, or lose contact with the solid electrolyte during stripping. These processes reduce the lithium available for subsequent cycles and affect capacity.
The Dongguk team investigated whether coating the current collector could help control this process. “Our interlayer acts as a seed for Li nucleation, promotes uniform Li plating, reduces Li loss and improves the reversibility of repeated charge and discharge,” Kim said.
Tin and carbon control lithium growth
The researchers examined pure carbon, pure metal and combined metal/carbon coatings. A tin/carbon bilayer on a copper current collector provided the best overall performance among the tested configurations and demonstrated favorable lithium deposition and interfacial stability.
The two layers fulfill different roles. Tin lowers the energy barrier for lithium nucleation, thereby supporting the formation of lithium at the interface. The carbon overlayer regulates subsequent growth, potentially limiting uneven deposits and stabilizing the area where tin and lithium interact.
The team also applied a thin metallic lithium layer to the coated collector. This pre-lithiation step created a reserve to compensate for lithium loss during the initial cycles.
During the initial lithium plating, a three-dimensional structured region containing tin and lithium-tin was formed within the interlayer. According to the researchers, this structure could accommodate volume and shape changes during later cycles and help maintain contact and stability.
Ultra-thin platform shows storage potential
The finished battery combined a lithium vanadium oxide cathode, a lithium phosphorus oxynitride solid electrolyte and the coated copper current collector. On the 100th cycle, it achieved a volumetric energy density of 235.13 Wh/L, measured at a reported temperature of 0.01 °C. Its total thickness was 2.77 micrometers.
“Our approach shows how interface technology and lithium inventory management can improve anodeless thin-film batteries,” said Kim.
“This approach could support the development of ultra-thin batteries for wearable electronics, IoT sensors and medical devices, as well as scalable anodeless ASSBs for industrial-scale power supply,” he added.
The results demonstrate a way to manage both lithium deposition and lithium supply within an ultra-thin battery architecture.
The study was published in the scientific journal Advanced energy materials.
