Electric vehicles, in the last decade, have become more affordable and reliable than ever before, but perhaps taking an even closer look can help researchers develop better solutions.
Of course, better solutions for electric vehicle batteries would need to fulfill a number of requirements. Increased energy density (Wh/kg) would increase the range of the vehicle, which is arguably the most important point. On the other hand, the battery can’t increase density at the expense of power delivery, battery production costs and environmental impact, and the number of charge / discharge cycles.
Clearly, this is a delicate balance that researchers and electric vehicle developers are working with, with some degree of success. Improving the performance of electric vehicle batteries, by trial and error, however, has been slow and painstaking. Understanding how rechargeable batteries work, on a microscopic level or even a molecular level might point researchers in the right direction regarding materials or processes.
For example, embedded sensors in individual cells might optimize charging and discharging while the battery is in use in an electric vehicle, but what about the manufacture of the battery itself? Getting a much closer look at rechargeable batteries is exactly the aim of researchers at Pacific Northwest National Laboratory (PNNL), who is working with the US Department of Energy’s Environmental Molecular Sciences Laboratory.
Working with a dime-sized wet-cell and a microscope, PNNL researchers can watch directly as the cell cycles. Being able to see what actually happens to the anode and cathode in the rechargeable cell has answered some questions, but has opened up new ones, as well. For now, researchers have come to understand the swelling that occurs in the electrodes as ions transfer. For future electric vehicle batteries, as well as for a host of other portable electronic devices, PNNL’s research seems to indicate that nanowires would be a better choice for lithium-ion batteries.
As for unanswered questions, PNNL researchers have discovered a “mystery layer,” a leading edge that forms inside the electrode as the lithium ions penetrate it. It could be a determining factor in the performance of electric vehicle batteries, but exactly how it forms and behaves has, so far, eluded study.
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