Enhancing cost efficiency in lithium-ion battery production via internal resistance measurement in the formation process

Abstract

Internal short circuits (ISCs) caused by metal impurities pose significant challenges in lithium-ion batteries manufacturing. This defect accounts for a large portion of the production time, specifically In this paper, we propose novel methods for detecting ISC abnormalities in lithium-ion batteries (LIBs) during discharge and voltage relaxation processes. Through comprehensive analysis of electrochemical behavior, it was demonstrated that ISC abnormal cells exhibit distinct characteristics compared to normal cells, particularly in term of equilibrium potential and internal resistance. Experimental results confirmed that ISC abnormal cells have higher equilibrium potential and lower internal resistance compared to normal cells. Two detection methods were proposed: the internal resistance slope method using in-situ electrochemical impedance spectroscopy (EIS) during discharge and the overtime internal resistance measurement method during voltage relaxation. These methods were validated using Samsung SDI 21700 cylindrical batteries and further verified for LIBs with LFP cathodes. The proposed methods not only significantly reduce ISC detection time in the manufacturing process, but also enhance reliability compared to traditional methods. When applied to actual Samsung SDI 21700 cylindrical batteries, the anticipated cost savings were achieved by shortening the ISC detection time from 7 days to 3 days, and the overall production time could be shortened from 10 days to 6 days, a 40% reduction. Implementation of these methods is expected to revolutionize battery manufacturing processes, ensuring higher technical capability and stability in LIBs production.