Bosch acquisition of Seeo highlights NMC vs. NCA chemistries and safety

September 22, 2015 // By Steve Taranovich, EDN
Bosch, one of the top automotive suppliers in the industry, on August 28, 2015 strategically acquired Seeo, a solid-state battery developer of next-generation energy storage. There was not much notice in the industry, but I believe this could be a significant boost to Seeo with the financial backing of Bosch.

This is the first instance of a major automotive player outright acquiring a next-generation battery developer, highlighting the strategic importance of advanced energy storage for the automotive value chain.

The potential is there for a significant increase in the range of electric vehicles (EV) as well as a safer technology in EVs and hybrid electric vehicles (HEVs). Lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminium oxide (NCA) are two standard Li-ion chemistries for the cathode makeup in those batteries.

Addressing the critical factor of safety, Reference 1 outlines electrical abuse tests such as short circuit, overcharge and over-discharge performed on these batteries with the two different cathode chemistries. The tests showed that Lithium Iron Phosphate technology (LiFePO4/C or LFP) cells have higher thermal stability and would be safer against thermal or electrical abuse where heat generation is the critical point. The problem is that [when or if] LFP calls are overcharged, the cathode does not have an overcharge reserve like that of NMC and NCA, such that the LFP will be irreversibly damaged earlier than NMC and NMA cells. In addition, LFP cells showed occasional electrical leakage when short circuited.

So there is certainly more research and development to be done regarding the NCA cathode chemistry, but it is beginning to look promising.

Reference 1 also discussed the Current Interrupt Device (CID) which protects a battery from over-charge. See Figure 1.

Figure 1: Typically, a CID is located at the top of a cylindrical battery. Here it is shown before and after opening (Image courtesy of Reference 1)

Before the acquisition Seeo had been trying to move from lower-energy LFP (lithium iron phosphate) cathodes towards higher-energy NCA (nickel cobalt aluminium) cathodes to keep ahead of the competition. It was also looking to set up joint ventures to help it scale up production of cells capable of 350 Wh/kg, a crucial step in proving its new technology.