It was announced that a US company will be supplying critical components for Electric Vehicle (EV) batteries to Panasonic. Redwood Materials, Inc., is set to supply EV battery cathode components from its facility in Kansas City. Redwood Materials was founded to close the battery recycle loop by JB Straubel. Straubel was a co-founder and former CTO of Tesla.

A lithium-ion battery doesn’t just rely on lithium. Other substances work together with lithium and the whole composition will vary between manufacturers. The Wikipedia entry for lithium-ion batteries lists the Panasonic cathode material as LiNiCoAlO₂. Panasonic works in cooperation with Tesla to supply batteries using Lithium Nickel Cobalt Aluminum Oxide cathode batteries. As alluded to above, Redwood will be supplying cathodes made of recycled battery materials.

The lithium battery electrolyte is almost always contains a lithium salt such as LiPF6, lithium hexafluorophosphate, in a non-aqueous organic carbonate electrolyte like ethylene or propylene carbonate. These two carbonates function as high boiling, polar aprotic dispersants. The substances are cyclic carbonate ester compounds and have a high dielectric constant. The high dielectric constant means that the molecules are polar enough to coordinate Li+ ions to aid in electrolyte mobilization of the Li salt. The electrolyte may also contain a solvent like diethyl carbonate to decrease viscosity and lower the melting point. The PF6 anion is a large, charge diffuse, weakly coordinating anion that helps keep the lithium cation mobilized and loosely bound in the polar aprotic carbonate solution. This anion is inert enough and lends solubility in organic solvents making it useful for many applications. Ammonium salts with PF6 anion are often used as ionic liquids. Weakly coordinating anions are used to allow the corresponding cation to be partially unsolvated and therefore more available for reaction chemistry.

Both in producing power and in recharge, when electrons are being passed around between chemical species and changing oxidation states, it means that chemical changes are occurring. When chemical changes (reactions) are happening, it means that heat is being absorbed or evolved. In the emission of heat, the amount of heat energy per second (power) produced can be large or small. It is critical that the temperature of the battery not exceed the boiling point of the lowest boiling component which may be the carbonate dispersant, as in ethylene carbonate (bp 243 C) or viscosity modifier like diethyl carbonate (bp 126 C). A liquid phase internal to the battery flashing to vapor can overpressure the casing and rupture the battery. A liquid changing into a vapor phase wants to increase its volume by from ~650 to 900 times or beyond. To make matters worse, a chemical reaction generally doubles its rate with every 10 degrees C of temperature rise. Runaway reactions generate runaway heat production.

Lithium batteries have flammable components such as ethylene carbonate (flash point 150 C) and diethyl carbonate (flash point 33 C) that could be discharged and ignited if the battery bursts open, possibly leading to ignition of the surroundings, be it in your pants pocket or in the cargo hold of a passenger aircraft.