Did your junior high science teacher demonstrate how to make a battery out of a potato? Spud cells share the same fundamental principles as alkaline, lead-acid, nickel-cadmium, lithium-ion and other types of batteries.

Every battery does the same thing: it causes electrons to flow from one pole, or electrode, to another. This electron movement—or electric current—is created by various kinds of chemical reactions (and therein lies the difference between the spud cell and the li-ion cell).

Every battery has four basic functional components: two electrodes, the anode and cathode; the separator; and the electrolyte.

Electrodes
The negative electrode is called the anode; the positive is the cathode. One electrode acts as a source of lithium ions and the other as a sink. Lithium ions flow from the anode to the cathode when the battery is discharging, and from the cathode to the anode when the battery is charging.

Separator
The anode and cathode can’t come in direct contact—that’s a short circuit. But the material separating the poles must have sufficient porosity to allow lithium ions to flow between them. (Potato flesh is an adequate separator at the junior-high level.)

Electrolyte
The electrolyte—for which a host of different compounds can be used— soaks the separator and conducts lithium ions between the electrodes.

To balance the chemical equations, electrons are drawn through an external circuit to do work during discharge and are put into the system via an external power source during charging. In the spud cell, potato juice acts as the electrolyte; in the lead-acid battery, acid does the trick.

From these fundamentals, the combinations of materials and chemistries are bounded only by the periodic table of elements, and the resulting battery characteristics vary hugely:

• Primary batteries discharge their stored electricity just once, and can’t be recharged. AA alkaline batteries are one example, lithium metal batteries are another.
• Rechargeable batteries might take anywhere from one hour to twelve hours to recharge. Lead acid batteries typically take 8-10 hours to recharge.  Lithium-ion batteries charge to 80% of full capacity in less than one hour.
• Power describes the rate capability of the cell. It takes more power to drive a jackhammer than an electric whisk.  High-power applications (Imara’s focus) include outdoor equipment, power tools and hybrid vehicles. 
• Energy describes the runtime of the battery. Energy driven applications include laptops, cell phones and pure electric vehicles. High-energy batteries deliver long runtimes—one Imara 18650 battery provides the equivalent lifetime energy of 2200 AA alkaline batteries.
• Cycle-life describes the battery’s ability to charge and discharge (one cycle) repeatedly. Cycle life is extremely dependent on the depth of discharge, temperature and the rate of discharge.  All three factors must be known to compare cycle life data.
• Toxicity is a function of the materials used in the battery. Lithium-ion batteries are non-toxic (lithium was once a key ingredient in 7-Up).  Many batteries employ toxic compounds such as cadmium and lead.
• Weight and Size matter in real-world applications. Who cares how much power, energy, runtime, and cycle-life a battery delivers—if it weighs 60 pounds? Lithium is next to Helium on the periodic table; it is the lightest metal with the greatest energy density.

The unique Imara advantage is that our cathodes are “materials agnostic” or able to use a variety of lithium-ion cathode blends. Therefore, we can focus on choosing the materials that deliver the best combination of power and energy without compromising runtime or cycle life. We are able to use standard electrolyte, anode and separator materials to keep our costs down.

Imara batteries are powerful, compact, lightweight, long-lived, and cost-effective. Who needs cords?