As vehicle manufacturers move toward electric-powered drivetrains (and away from fossil fuels and carbon gas emissions), the lithium-ion battery takes on a greater role.

This trend toward “e-mobility,” however, requires a conversion.

All batteries, including the lithium-ion batteries powering everything from electric vehicles to drones to computers, operate with direct current (DC). A majority of appliances rely on AC, or alternating-current, power sources.

Traditionally, alternating current from the power grid must be transformed from AC to DC and stored in the battery, resulting in power loss.

A new battery concept eliminates the current conversion by introducing a new type of electrode: The Biode.

The lithium titanate “Biode” features the characteristics of an anode and a cathode, enabling an AC system to store energy.

"The Biode is a new word we created, as it is in between an anode (minus) and a cathode (plus)," Tadashi Kubo, CEO and co-founder of the Cambridge, UK-headquartered AC Biode, told Tech Briefs via email.

Kubo and his company were one of eight category winners in the 2019 "Create the Future" Design Contest. (See all of the winners of this year's competition.)

The left figure shows when the semiconductor switch is on; the right figure shows when the semiconductor switch is off. The arrow demonstrates the direction of the electron, to show Alternating Current.

In addition to saving the energy lost in AC-to-DC conversion, the more compact Biode battery leads to lower (and therefore safer) electric potential between electrodes, says Kubo.

The team currently has a prototype of the AC battery at 20W, which they plan to scale.

In an edited interview below, Kubo tells Tech Briefs about the kinds of battery applications he wants to take to the skies by 2020.

Tech Briefs: Can you explain the energy inefficiencies of current batteries?

Tadashi Kubo: Ever since Alessandro Volta developed a primary battery in 1800, the general public has begrudgingly accepted that the battery electricity source must be DC. Although it makes sense to use DC batteries for lower-power devices such as lights, radios, or smartphones, battery applications for electric vehicles and drones consume much more power within the same amount of time. Thus, DC batteries alone prove to be insufficient to provide a steady voltage or current that these devices require. In these cases, AC batteries are needed, and they are more efficient and easier to control than conventional DC batteries.

Tech Briefs: Do you have a patent?

Tadashi Kubo: We [AC Biode] applied for two patents in Japan in 2016 and will apply for additional two patents in Japan and at Patent Cooperation Treaty (PCT).

We already have a prototype of our AC battery at 20W. We will scale it up to around 50kW within a year once we raise seed funding or receive public grants.

"A prototype of our world's first standalone AC battery, consisting of an anode (-), a Biode (in between + and -), and a cathode (+)," says Kubo.

Tech Briefs: How is your battery better than conventional DC batteries?

Tadashi Kubo: Compared to the current DC batteries, our innovative technology has the following six advantages:

  1. It is safer, thus reducing yield rates at battery production lines. Voltage within the battery cells is divided by the Biode, leading to safer operations. While there is 4V between anode and cathode within the conventional Li-ion battery, for example, Biode can divide the voltage into 2V each and at the same time increase the battery capacity.
  2. A double lifecycle: Quality of electrode particles varies a lot; in particular, that of cathode particles. The quality of the electrode particles is a limiting factor for DC batteries; however, it is not a limiting factor for AC batteries because AC, a shape of wave, can instead utilize the average, not the worst, quality as electrodes advance.
  3. Regarding volume, our battery is up to 30% more compact. In addition to anode and cathode, the Biode has both characteristics.
Compared to the conventional battery system shown on the left, the Biode reduces battery size by 30%.
  1. We utilize all the existing materials and production lines of batteries and circuits. The production cost of Biode is the same as that of an anode, manufactured by the existing roll-to-roll method.
  2. The technology is applicable not only to Li-ion batteries but also any type, including all-solid-state batteries.
  3. The input is AC, and our output can be AC or DC, depending on the needs.

Tech Briefs: What inspired this idea?

Tadashi Kubo: While power transmission/distribution and motors have both the option of AC and DC, batteries do not. All batteries use DC, not AC. Realizing AC batteries expands more flexibility, especially when combining with the Cockcroft-Walton Multiplier, [a circuit that generates DC voltage from an input of alternating current].

Tech Briefs: What kinds of applications are possible with these benefits?

Tadashi Kubo: Our first target is for drones because it is easier for us to start with, and drones' batteries are critical. We will expand to e-bikes, e-scooters, then EVs, aerospace, and more.

Tech Briefs: What’s next for you, regarding this technology?

Tadashi Kubo: We have tested this out in our laboratory in Kyoto, Japan. Once we raise seed funding, we will scale up our prototype and test more. By mid 2020, we would like to test our battery and Cockcroft-Walton Multiplier for drone applications.

What do you think? Share your comments and questions below.