Effect of electrode manufacturing defects on electrochemical performance of lithium-ion batteries: Cognizance of the battery failure sources

• Battery electrode manufacturing defects alter the electrochemical performance.
• Agglomeration, pinholes, non-uniform coatings, metal contamination were evaluated.
• Agglomerations, and non-uniform coating showed substandard performance.
• Microstructural analysis is correlated with poor performance in defective electrodes.

During LIB electrode manufacturing, it is difficult to avoid the certain defects that diminish LIB performance and shorten the life span of the batteries. This study provides a systematic investigation correlating the different plausible defects (agglomeration/blisters, pinholes/divots, metal particle contamination, and non-uniform coating) in a LiNi0.5Mn0.3Co0.2O2 positive electrode with its electrochemical performance. In addition, an infrared thermography technique was demonstrated as a nondestructive tool to detect these defects. The findings show that cathode agglomerates aggravated cycle efficiency, and resulted in faster capacity fading at high current density. Electrode pinholes showed substantially lower discharge capacities at higher current densities than baseline NMC 532electrodes. Metal particle contaminants have an extremely negative effect on performance, at higher C-rates. The electrodes with more coated and uncoated interfaces (non-uniform coatings) showed poor cycle life compared with electrodes with fewer coated and uncoated interfaces. Further, microstructural investigation provided evidence of presence of carbon-rich region in the agglomerated region and uneven electrode coating thickness in the coated and uncoated interfacial regions that may lead to the inferior electrochemical performance. This study provides the importance of monitoring and early detection of the electrode defects during LIB manufacturing processes to minimize the cell rejection rate after fabrication and testing.