CONNEXX SYSTEMS in Japan is developing a solid-state technology with its SHUTTLE BatteryTM that has far greater energy density than lithium-ion batteries.

The new battery is a high temperature operation, all-solid-state storage battery that combines a solid oxide fuel cell component with an iron-air battery. The SHUTTLE Battery™ is unique, because it has 500 percent more electricity storage capacity compared to lithium-ion (Wh/L base) and almost the same amount of thermal energy can be stored at the same time, says CONNEXX Founder and CEO Dr Hisashi Tsukamoto. The device can store 1,000 percent more energy than lithium-ion technology.

Unlike lithium-ion batteries which use a flammable non-aqueous electrolyte, the Shuttle Battery™ is all solid and built from non-flammable materials, so it is intrinsically safe, he says. The use of an iron anode also means the cost of energy production is drastically reduced.

In an article published in Evolutionary and Institutional Economics Review, CONNEXX researchers describe the discharge reaction: Oxygen in air is reduced on the cathode. Hydrogen gas in the anode compartment reacts with the oxygen anions carried through the solid electrolyte from the air electrode to produce water. The water vapour is reduced to hydrogen gas as it reacts with the anode fuel material, and the regenerated hydrogen reacts with the oxygen anions again at the anode to produce water vapour and electrical power. This cycle continues to generate electricity until all the metal is oxidised. The discharge reaction also produces heat.

The charge process can take place when the device is given electricity and heat from outside: the reverse cycle takes place until all metal is reduced and the iron oxide becomes pure iron.

The hydrogen in the system only acts as a carrier for the oxygen moving between the anode and the metal in the anode compartment, so it is not consumed. In potential applications, such as large-scale power storage and electric ships, this negates the need for high-pressure storage tanks, reformers, pipelines and hydrogen gas distribution stations. “The SHUTTLE Battery™ is a hydrogen energy storage device, but since it reproduces hydrogen inside the system it does not need typical hydrogen infrastructure investment,” says Dr Hisashi.

The technology is currently being scaled up and a prototype demonstration unit for large-scale energy storage is being built. While this will be suitable for tens or hundreds of megawatts of storage, Dr Hisashi also sees potential for maritime applications. He says the electrification of shipping bringing environmental benefits as well as a quieter, less toxic working environment for crews. In Japan, the vast majority of materials handling is done by a fleet of 5,000 cargo ships, and Dr Hisashi anticipates this to be the initial market for the technology. He says a prototype system suitable for onboard use could be developed within two years, with uptake by shortsea shipping in Japan in the next three to five years.

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