Team assesses environmental impact of vehicle batteries

In their first study, the researchers found that nickel metal hydride (NiMH) batteries, which are used in most hybrids, have a greater lifecycle impact than either iron phosphate lithium-ion (LFP) or nickel cobalt manganese (NCM) lithium-ion (Li-ion) batteries — both of which are now emerging on the market.

Thus a shift to the latter should be encouraged, according to the researchers, who nevertheless caution that their work uncovered a greater impact for all three types than had previously been reported.

‘There’s too little public research on this,’ study co-author Guillaume Majeau-Bettez of the Norwegian University of Science and Technology told The Engineer. ‘On the other hand, there seems to be a lot of private research. Internal LCAs [lifecycle assessments] have been done, but the results are not made public — so that’s one contribution of our research.

‘We’re trying to take a very broad perspective on this so that companies and governments know what the trade-offs are for different technologies.’

For all three batteries, the energy requirements for their manufacture were a major cause of greenhouse gas emissions.

One component of the analysis demonstrated the significance of using polytetrafluoroethylene as a dispersant/binder in the electrode paste. Its production was responsible for more than 97 per cent of the ozone depletion potential of all three batteries, along with 14–15 per cent of the greenhouse gas production from the two Li-ion batteries, mostly owing to the halogenated methane emissions.

While the production of NiMH causes the least greenhouse gas emissions impact per kilogramme, its lower energy density makes it score worst, relative to both its nominal energy capacity and to the researchers’ storage-based functional unit. Similarly, the greenhouse gas impacts of LFP and NCM production are roughly equal for a given mass or nominal energy capacity, but the greater life expectancy of LFP confers a net environmental advantage to this type of battery for a per-energy-delivered functional unit.

The researchers plan to do further tests as competing and alternative battery chemistries and technologies emerge.

‘There seems to be very definite advantages to shifting to partial electric drivetrains, depending on your electricity mix, and there has been quite a lot of research on that — the type of electricity you use,’ said Majeau-Bettez. ‘But the production of the vehicle itself has been poorly studied.’