Lithium Plating on Graphite Negative Electrodes: Innovative Qualitative and Quantitative Investigation Methods

Abstract

The effect of metallic lithium depositing on the negative electrode surface of a carbon-based lithium-ion battery instead of intercalating into the graphitic layers, namely lithium plating, can be assigned to charging at low temperatures and/or high currents. Cell parameters, such as performance and safety, are negatively influenced by this phenomenon. Elemental lithium deposited on the negative electrode requires more space than the intercalated compound and therefore increases the cell volume. Thus, the thickness changes during cycling can be used as a qualitative indicator for lithium plating. In this context, two different non-destructive experimental setups detecting the thickness profiles in situ are presented. Moreover, a quantitative titration technique to determine the exact amount of lithium deposited is established.The utilization of lithium-ion batteries (LIBs) in automotive applications requires extended cycle life and prolonged calendar life. Therefore, the investigation of their capacity-fading mechanisms is of increasing interest. 1 Carbon-based materials, in particular graphites, are commonly used as negative electrodes in these energy storage systems. 2,3 Thus, most studies regarding negative electrode-aging mechanisms were conducted with graphite-based cells. 4 Mechanisms, such as cracking of particles due to volume changes, decomposition of the binder, growth of the solid electrolyte interface (SEI), and metallic lithium deposition are primarily influences on the aging process of an negative electrode. 5 The latter degradation process, also known as lithium plating, is usually formed as a consequence of charging at low temperatures, high state of charge (SOC) and high charge rates. 6 These conditions lead to a polarized negative electrode and poorer electrode kinetics. As soon as the potential of the negative electrode falls below 0 V measured versus the Li/Li + half cell, lithium plating is thermodynamically favored on the negative electrode surface. 6,7 The structure of deposited lithium depends on the current applied. 8 Orsini et al. have demonstrated that lithium deposition on metallic electrode surfaces generally has a mossy structure through low-current charging, whereas high-charge rates lead to dendrites. 8,9 Lithium dendrites, which occur on graphite as well, have a serious effect on the cell's safety and performance issues. The dendrites, which grow directly on the negative electrode, can cause short circuits, leading to serious fire hazards associated with the flammable organic electrolyte. 6,10,11

An Innovative Process for Ultra‐Thick Electrodes Elaboration: Toward Low‐Cost and High‐Energy Batteries

“…Indeed, Singh et al stated a drastic decrease in the capacity on cycling thick electrode cells; actually, all the cells ranging from 6 to 9 mAh cm −2 presented in their research lost at least 10% of initial capacity during the course of the first 20 cycles at C/10. The authors attributed this capacity fade to lithium plating during the charge that caused an increased resistance to lithium‐ion transport . The much better cycling behavior obtained for our cells suggests that no significant lithium plating takes place, which is likely the result of a good potential distribution in the different zones of our electrodes, highlighting again the beneficial effect of burrs on the electron collection (See Figure S4, Supporting Information).…”

“…The authors attributed this capacity fade to lithium plating during the charge that caused an increased resistance to lithium-ion transport. [30] The much better cycling behavior obtained for our cells suggests that no significant lithium plating takes place, which is likely the result of a good potential distribution in the different zones of our electrodes, highlighting again the beneficial effect of burrs on the electron collection (See Figure S4, Supporting Information).…”

Non-Destructive Detection of Local Aging in Lithium-Ion Pouch Cells by Multi-Directional Laser Scanning

“…However, the measurements only considered a single measurement point assuming a homogeneous distribution of the formed deposit layer. The work of Birkenmaier et al 28 dealt with the detection of the spatial distribution of lithium plating by point-laser sensor measurements. Measurements are gathered from one side of the cell requiring an initial data set in order to correct the recorded thicknesses at each point.…”

“…37,43 The irreversibly deposited lithium causes a permanent thickness change. 16,28 Experimental measurements in the work of Agubra et al 37 determined the irreversible thickness change per electrode layer to be between 21 μm and 53 μm depending on the local SOC and the affected area of the anode. These measurements were gained from an accelerated aging cycle (4 C) involving 600 cycles applied to a NMC/graphite pouch cell which was analyzed by means of a destructive post-mortem method.…”

Localized Swelling Inhomogeneity Detection in Lithium Ion Cells Using Multi-Dimensional Laser Scanning

“…Local resolution of cell dilation has been achieved by 3-D image correlation 25 and laser triangulation. [26][27][28] Other non-touching measurements include X-ray tomography 29 and neutron diffraction. 15 Dilation measurements have been used to detect lithium plating 22 and, by making use of local resolution across the cell surface, to investigate inhomogeneous aging.…”