WMG, The University of Warwick, Coventry CV4 7AL, United Kingdom

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Abstract: Lithium plating significantly reduces the lifetime of lithium-ion batteries and may even pose a safety risk in the form of an internal short circuit, leading to catastrophic cell failure. Low temperatures, high charge currents and battery age are known to be contributing factors to increased lithium plating. To reduce or avoid battery ageing induced by lithium plating, a method for lithium plating detection is essential to help understand the favourable conditions under which battery charging is optimised. In this study, we present a concept to design an experiment-based approach to improve lithium plating detection sensitivity using the non-destructive voltage relaxation analysis method. Commercial NCA/graphite cells are employed for this study. Here, the reversible part of the plated lithium providing a unique cell voltage relaxation profile is used as a pseudo-measure to detect the onset of plating. This profile is observed while the cell is at rest as well as under a low C-rate discharge regime immediately after charging. It is found that the CV (Constant Voltage) phase cut-off current value significantly influences plating detection. To address this issue, a procedure to determine the optimal cut-off current in the CV phase of charging is introduced to improve the detection sensitivity. With the proposed method, plating detection chances are improved which will help in understanding the favourable conditions and developing plating control strategies. Furthermore, a correlation between lithium plating and Electrochemical Impedance Spectroscopy (EIS) measurements are utilized to demonstrate the influence of previous ageing conditions on lithium plating.

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