Pioneering researchers at Stanford University have announced what appears to be the first practical, transparent lithium ion battery. The experimental battery technology is said to be very flexible, utilizes a traditional Li-ion chemistry and can be manufacturered using a relatively simple process.
To create a transparent battery, researchers fabricated an extremely fine, gold mesh through lithography. The result is a mesh-like pattern comprised of ultra fine "wires", each measuring about 35 μm thick. At this width, lines become very difficult to see but visible light continues to flow through gaps in the grid mostly unfettered. A clear electrolytic gel is then sandwiched between two mesh layers and then sealed in a clear housing to produce a rather inconspicous battery.
Despite the obvious cool-factor of these stealthy batteries, they do come with a few caveats. For one, lithography, as it is used for most electronics, would actually destroy the chemicals used to generate and store power. With this in mind though, the team managed to develop a simplistic yet novel process to overcome this obstacle (liquid assisted lithography).
Also, because the mesh current collector is less dense than the electrodes found in typical Li-ion cells, these batteries are expected to deliver roughly half the power of traditional Li-ion batteries. As one last noteworthy point, while researchers claim the battery is 'transparent', the research paper indicates a best-case scenario of about 60% transparency, so completely invisible batteries may not quite be here as of yet.