We went with a pure NMC, which offers the highest energy density, about 40% higher than iron phosphate. The technique that Sony and Sanyo use is to blend [their NMC] with Manganese spinel to get the high rate capability. That results in a big sacrifice in cycle life. Our technology allows us to get the high rate without the blending of the spinel.

—Neil Maguire

Cycle life performance. Click to enlarge. Source: Imara

The process—about which Imara reveals few details—creates a cathode with very low impedance, stable cycle life and high current carrying capacity. The initial core technology, exclusively licensed from the Stanford Research Institute (SRI), was developed and funded in conjunction with the US Department of Energy as part of the Partnership for the Next Generation Vehicle (PNGV) initiative.

One of the approaches SRI explored with PNGV (and that was reviewed by the National Research Council in a series of reports on PNGV) was the use of a non-carbon anode material and a nonflammable solvent base for the electrolyte. While these features and the nearly 2 V less-negative anode potential reduced safety concerns, it was at the expense of reduced energy-density and power-density potential. Because larger amounts of active materials and larger electrode areas were required to achieve the same energy and power levels as more conventional lithium-ion batteries, the SRI technology would likely have higher production costs.

Imara is not using that specific technology (although it does have access to some of the non-flammable electrolyte IP, Maguire said), but is leveraging material preparation and electrode manufacturing techniques developed by SRI. The Imara cells do not require more (nor less) electrode material than comparable cells on the market, and there is no great cost penalty or savings in the manufacture of cells. The savings are in the dollars per delivered Watt hours, Maguire said.

Imara has demonstrated the technology across multiple lithium-ion chemistries. It is being scaled to high-volume production and will be shipping by the 4th quarter of 2009.

The automotive market. Imara would like to get into the automotive sector, but sees that as a multi-year process, and one that begins with a ramping up of production capability via the tools market (an approach also taken by A123Systems). Its strategy for packs is to work with companies such as Ricardo and Tier One system integrators, as well as directly with the OEMs.

The Imara technology is very suited for high-power applications in hybrids; it is not clear yet whether or not it offers an advantage for an optimized energy cell (e.g., for EVs or longer-range PHEVs).

The technology we have is very low impedance. That’s important in high power applications, but we’ve yet to be determine how much of a technology advantage it is for a pure energy cell. With our equipment, we can coat more material, adjust porosity, and control how thick I want the material crushed, or how porous [the material will be]. If very porous, we have lots of ability to move lithium ions. Crush it thin, there’s not as good rate capability. We can wind more material, we can create energy cells, but our real technology advantage is power. The hybrid market is a really good fit for our batteries.

—Neil Maguire

Imara plans to introduce a larger format cylindrical cell next; that cell might be a better fit for SLI batteries as well as some small hybrid packs.

Manufacturing. Imara, based in Menlo Park, CA, has a pilot manufacturing facility in its headquarters that can produce more than 1 million 18650 cells per year. (Moving to a 32650 format would cut that in half.) It currently, however, has the ability to produce cathode material sufficient for 8 million 18650 cells per year out of the building. The company plans to ship rolls of the cathode material to where its customers are. Imara is currently in discussion with contract manufacturers in Asia.

Longer term, Imara is looking to set up a greenfield manufacturing facility in the US.

Resources

• Review of the Research Program of the Partnership for a New Generation of Vehicles: Third Report (1997)