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Professor Jay Whitacre, Founder and Chief Technology Officer
25 Apr, 2012

What’s Inside an Aqueous Hybrid Ion Battery?

I initially developed the Aqueous Hybrid Ion (AHITM) battery at Carnegie Mellon in 2008. Utilizing a water-based electrolyte and multiple functional active ions, AHI batteries address the needs of the energy storage customers and deliver a system that is safe, reliable, and affordable.

What’s in the AHI battery?

AHI batteries use materials that, while relatively common and inexpensive, are unique to this battery chemistry.

Aqueous Electrolyte: A battery’s electrolyte is the substance through which the active ions flow, from one electrode to the other. The AHI battery’s water-based electrolyte makes it truly unique, as this is unused in nearly all other battery chemistries.

Multiple Functional Ions: When batteries are discharged, electrons flow from the anode to the cathode through the load, while the ions flow from cathode to anode through the electrolyte inside the battery. The opposite occurs during charging. In the case of AHI batteries, sodium, lithium, and hydrogen ions all work together inside the battery to store and release electrical energy.

AHI battery during discharge

Activated Carbon Anode: Carbon, one of the most abundant materials on the planet, makes up the battery’s anode, or negative electrode. Activated carbon is simply carbon powder with a high surface area. This is important because when the battery is in use, a capacitive interaction takes place on the surface of the carbon. That means that as the battery is charged, electrons build up inside the carbon, and the surface becomes negatively charged. The active ions, which are positively charged and attracted to the carbon, fix themselves to the surface.

Manganese Oxide Cathode: Found in some Lithium Ion batteries as well as common alkaline batteries, manganese oxide (MnO2) makes up the cathode, or positive electrode. At the molecular level, MnO2 looks like a repeating three-dimensional lattice, with alternating manganese and oxygen atoms. When the battery is discharged, sodium ions flow into the MnO2, and situate themselves between the manganese and oxygen atoms. This means that there is an “intercalation” reaction taking place, rather than an electrode surface reaction, which is typically more corrosive and results in loss of capacity over time.

cathode and electrode interactions

Cotton Separator: A simple synthetic cotton separator is used to keep the electrodes from directly contacting each other. When soaked with electrolyte, this separator allows the sodium ions to flow between the anode and the cathode, while blocking electrons and preventing a short circuit.

Stainless Steel Current Collectors: The current collectors provide a path for the electrons to flow out of the electrodes.

Want to learn more? Watch my recent TED talk or check out our technology or applications pages.