Evaluating single-crystal and polycrystalline NMC811 electrodes in lithium-ion cells via non-destructive EIS alone

Rechargeable batteries such as lithium-ion batteries (LIBs) are prevalent in everyday life and can be found in most electronic devices. Their usage is set to drastically increase in the coming years due to the demand for more environmentally friendly and sustainable power sources. Thus, an understanding of the behaviours of the electrode materials is essential. In this work, the effects of different cycling regimes on single-crystal and polycrystalline NMC811 pouch cells are studied via electrochemical impedance spectroscopy (EIS). By using the non-destructive methodology of EIS alone, it is shown that single-crystal NMC811 pouch cells have superior battery performance characteristics compared to polycrystalline NMC811 pouch cells. This is thought to be due to the polycrystalline NMC electrodes being placed under uneven mechanical strain during repeated cycling and developing weak points which become micro-fractures. Use of such non-destructive methods is economically favourable to the industrial battery manufacturing sector as it reduces scrap costs. Graphical abstract: [Figure not available: see fulltext.]