Japanese researchers at Kogakuin University have developed a prototype lithium-ion battery which is capable of recharging using sunlight.
The battery uses a photovoltaic cell along with a cathode, made mostly from lithium iron phosphate, and an anode made of lithium titanate and lithium hexafluorophosphate.
The output voltage of the battery is reportedly around 3.6V and has achieved 20 full cycles— which means it is still a very long way off from being commercially viable.
While there is nothing new with the ingredients, what makes the latest development stand-out is the electrodes are only 80-90 nanometers in width.
To achieve the breakthrough the group doped a cubic lattice of K1 molecules with rock salt lithium borohydride (LiBH4), which allowed the group to make a solid solution at normal atmospheric pressure that remains stable at room temperature.
The group, led by Kogakuin University president and professor Mitsunobu Sato, began work in 2013. However, some changes to the current battery were made so that electrons excited by light coming to the negative electrode could be used to charge the battery.
It is not the first time researchers have developed ‘see through’ cells. Back in 2011, researchers at Stanford University used silicon lithography, liquid silicone and electrodes fashioned into grids that appeared transparent to the naked eye.