Scientists at South Korea's Tonguk University have created a thin-film solid-state battery only 2.77 µm thick, about 30 times thinner than a human hair. The battery achieves an energy density of 235 Wh/L and uses a tin‑carbon coating to manage lithium distribution.
The design eliminates a separate anode: during the first charge, lithium from the cathode plates directly onto the current collector, forming an internal anode. This simplifies production and could be used in wearables, tiny sensors and medical devices where conventional batteries are too large.