Influence of Switching on the Aging of High Energy Lithium-Ion Cells

Abstract

An AC-battery or multilevel inverter used to increase safety and flexibility is realizable by switching the cells and modules on and off in a defined way and thus can replace the bidirectional converter. Assessing possible additional aging due to switching, the results of a previous study for a high-power optimized cell showed no influence on the current rates or the switching. In this paper, a highly energy-optimized LG 18650-cell is investigated to discuss the influence of switching during the charge and discharge process, respectively, as well as combining both processes together with clear performance differences when applying higher charge and discharge currents. Moreover, the influence of switching is discussed for the two frequencies (50 Hz and 10 kHz) and different duty cycles. The aging is analyzed by capacity loss and resistance increase, by dV/dQ analysis, and by electrochemical impedance spectroscopy. We found no clear negative influence of switching but a positive effect if the cells are switched during charge. The best performance is found for switching during charge as well as during discharge. The cell aging during switching is clearly determined by the average and not the maximum current applied. This work shows no negative effects of multilevel inverter applications on the tested cells.

Path‐Dependent Ageing of Lithium‐ion Batteries and Implications on the Ageing Assessment of Accelerated Ageing Tests

“…Furthermore, an in‐plane (that means along the surface of the electrode sheet) inhomogeneity has also been reported [43] . Such inhomogeneity might arise for different reasons, [32] such as an inhomogeneous current distribution, [43] temperature gradients [44] or pressure gradients [45] . In contrast to the cyclic ageing phases, the calendric ageing phases only slightly influence the height and prominence of features in the DVA.…”

Impact of Electrolyte Volume on the Cycling Performance and Impedance Growth of 18650 Li-ion Cells

“…Previously, studies have documented the influence of relaxation on the restoration of cell capacity. 19 EIS analysis and variation of the EIS parameters vs cycle number for the cells with different electrolyte volumes.-The extensive sets of EIS data collected at various SoC levels and under different cycling conditions were fitted and the equivalent circuit parameters were extracted for further analysis. To model the capacitive elements of the double layer(s), constant phase elements (referred to as Q) were used.…”

Balancing resistor-based online electrochemical impedance spectroscopy in battery systems: opportunities and limitations

“…The 18650-LG-Chem-MJ1 battery is sensitive to aging in the medium to lower frequency range 41 . As a compromise, the final frequencies used for excitation are f excited = 2, 5, 10, 20, 40, 80, 160, 320, 640 Hz.…”