Environmentally friendly driving, fuel efficiency, electric vehicles- all topics that have been a subject of major debate in recent years, and yet only a limited few manufacturers have the courage to pursue ground-breaking developments. Toyota Motor Corp, one of the leading producers of ‘green vehicles’, might just hold the solution.
At a meeting held on September 24th, 2012, in Tokyo, the company presented their brand new prototype of an all-solid-state battery with a five times higher output density, a.k.a storage energy capacity, than this of their existing Li-ion batteries. The main improvements are related to the conductivity of Lithium (Li) ions, which now go above levels of 1 x 10-2S/cm. The company still bids on the use of Sulfide-based solid supersonic conductor (Li10GeP2S12) in order to maintain voltages and exchange electrical impulses, however this time Germanium (Ge) was added.
“Germanium enables to realize a structure in which crystals have refined shapes and Li ions are linearly arranged,” the company said. Furthermore, the material experiences high lithium ionic conductivity, which can be considered the highest conductivity achieved by a solid electrolyte.
Technically, each fuel cell consists of seven layers of negative and positive electrodes with a solid electrolyte placed in between, enfolded in laminated film. Each layer has an estimated voltage of 4V adding up to an overall of 28V per fuel cell. The electrodes, together with the solid electrolyte, have dimensions of 70x105x2.5-3mm. The negative and positive electrodes are of a three-dimensional type, consisting of graphite and Ni-Co-Mn, commonly found in standard Li-ion rechargeable batteries.
In order to demonstrate the new development, Toyota presented an electric scooter powered by the prototyped all-solid-state battery, realizing a voltage of 28V through eighteen fuel cells connected in parallel.
In a short-run, Toyota intends to make the improved battery available commercially in the next 3 to 8 years. According to Japan’s New Energy and Industrial Technology Development Organization, releasing the product on the market, it is expected that the cost of battery production can drop up one-fifth the current level by 2020.