Transparent battery

Since the end of February 2013, a group of scientists from Kogakuin University of Japan, six people led by Professor Sato, have been developing and implementing an innovative idea - an almost transparent lithium-ion battery.

Finally, after two and a half years, namely on August 27, 2015, at the Innovation Japan 2015 exhibition held in Tokyo, the researchers presented to the general public a working prototype, a translucent battery that can be charged from light with different wavelengths, from red to near ultraviolet .

Thin films of the electrodes of the anode and cathode, 90 and 80 nanometers thick, respectively, turned out to be almost transparent. The longer the wavelength of the charging light, the more transparent the film electrodes remain after charging. So, under the influence of green light, the wavelength of which is 550 nanometers, the overall transparency is 60%, and under the action of sunlight, the lithium density on the electrodes increases significantly, and the transparency drops to 30%.

It was immediately decided to use Li3Fe2 (PO4) 3 (LFP) as the basis of the electrolyte for the positive electrode, and Li4Ti5O12 (LTO) and LiPF6 (lithium hexafluorophosphate) for the negative electrode. These materials are widely used in the production of conventional, opaque lithium-ion batteries.

It was on them, back in 2013, that scientists chose as the most suitable for the goal. Anode and cathode films were applied to glass substrates at an air temperature of 550 degrees for 30 and 10 minutes, respectively.

The resulting batteries can be charged both from sunlight, replacing solar panels, and from other light sources of suitable brightness. A demonstration at the exhibition showed how a new battery was discharged five times and charged from ultraviolet with an energy density of 10 mW / cm2, which is about 10% of ordinary sunlight. The output voltage was 3.6 volts, as well as conventional lithium batteries.

Tests in laboratories preceding the exhibition showed that the new type of batteries can withstand 20 cycles of discharge-charge without loss in performance.

The inventors themselves believe that their transparent batteries will prove to be quite a promising solution for covering them with windows of buildings, car windows, and other transparent surfaces, as a light tint capable of generating electric current.

This is exactly what will allow combining renewable energy sources, the methods of accumulation and storage of this energy, with the latest systems of so-called "smart buildings", the windows of which will be able to collect and accumulate solar energy.