A new concept to improve the lithium plating detection sensitivity in lithium-ion batteries

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.

The development of optimal charging strategies for lithium-ion batteries to prevent the onset of lithium plating at low ambient temperatures

“…The results show that reversible lithium plating was only found in the first two fast charge cycles. This reaffirms the findings from [30] and the literature contained within [3,22] that higher levels of plating lead to increased levels of capacity reduction and therefore must be avoided to prolong battery life.…”

“…To avoid lithium plating and to improve charge time, charge current in the third stage must be appropriately selected. From [30], for this cell, it was found that lithium plating was not detected with charge rates lower than 0.25C at ambient temperatures above 5 o C and reversible plating detection ability was maximum with a cut-off charge rate of 0.25C. As discussed in [30], lithium stripping begins in the…”

“…A full description of the VRP method; its derivation, application and underpinning theory is discussed in [26,30] and will therefore not be repeated here. For completeness, a brief introduction is provided.…”

“…The ΔSOHtarget can be defined based on this linear capacity fade rate. The ΔSOHtarget in this work is selected based on the author's previous low-temperature battery cycling results, reported within [30]. This research reported that the cells lost circa 10% capacity in ten cycles at 5 o C and 1C charge/discharge rate with the CC-CV charging protocol [30].…”

“…less than 0.1%) reduces the overall test period. From [30], it was found that the rate of capacity reduction was comparatively high during the early cycles and then slowed as the level of battery degradation increased. Hence, for the first 4 fast-charging cycles, the capacity test was performed after each fast charge cycle (N=1).…”