Rice researchers find the reason for degradation of lithium-ion batteries

Market Expertz   |     March 13, 2020

 

Rice University scientists have now brought to light the hazards of certain defects in lithium-ion cells. Materials scientist Ming Tang and Kaiqi Yang, a graduate student, introduced new stimulations to the cells, which resulted in putting too much strain in widely used lithium iron phosphate cathodes that open cracks and accelerates battery degradation. Their work has been published in the Journal of Materials Chemistry A and builds upon a recent Rice research that showed how putting defects in particles that are included in the cathode could help increase battery output by nearly two orders of magnitude by improving the efficiency of the movement of lithium.

In the subsequent study, the team observed that rapid charging and discharging, defected cathodes could develop cracks. Tang, Assistant Professor, Materials Science and Nanoengineering, Rice’s Brown School of Engineering, says that the conventional belief is that lithium moves uniformly into the cathode, with a region with an abundance of lithium that smoothly expands over the cathode’s center. However, the C-ray images taken in the lab showed a fingerlike boundary separating the lithium-rich and lithium-poor areas, similar to what is seen when water is injected into oil. Tang explains that the problem might be occurring due to the stress that destabilizes the flat boundary and leads it to become wavy. The change in the boundary share increases the stress further and triggers the formation of cracks. The research by Tang’s team shows that this instability increases due to a common defect in battery compounds known as ‘antisites,’ wherein iron atoms are present in the crystal that are meant to be for lithium. Tang adds that antisites can be a good thing, but they speed up the lithium intercalation kinetics, but they have observed a countereffect as excess antisites in the particles make the moving interface unstable and thus generate more stress.

Tang believes that there are a certain number of antisites in a cathode that will be ideal, i.e., enough to improve performance but not enough to make it unstable. The team will need some trial and error to get the right amount but their hypothesis might be beneficial for experimentalists. Recently, Rice researchers had also introduced a light-powered nanoparticle capable of shrinking the carbon emission of a sizable segment of the chemical industry.

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