Speaker
Description
Lithium-ion battery is considered as one of the most successful storage methods which enables the sustainability of the energy systems. However, its aging problems present considerable challenges in maintaining performance over its useful life. To study the degradation of lithium-ion batteries, numerous studies have been carried out that analyze the different phenomena that occur in internal components, in order to understand at a microstructural level, which processes are responsible for the loss of performance.
In this work, a Buck-type converter with enviromental temperaure control was build for charging and discharging lithium ion batteries, and later the effects of degradation on their internal components was studied.
The charging process was carried out in two stages: constant voltage and constant current. The discharge was carried out at constant current, subjecting a battery to 60 charge/discharge cycles at temperature of 25 ° C. Subsequently, its electrochemical behavior was compared at three different temperatures, 15, 25 and 35°C, using Electrochemical Impedance Spectroscopy. Batteries were later disassembled to analyze its components. Scanning Electron Microscopy, Energy Dispersion x-ray Spectroscopy and X-Ray Diffraction were used to analyze morphology and phase transformations on the components. The results showed that aging produces an increase in the internal impedance of the battery. Loss of active material was observed at the cathode. Despite the low number of cycles, the presence of cracks on the graphite anodic surface was observed as well as the formation and growing of a surface layer that accelerate the degradation. In addition, in the separators, the obstruction and deformation of pores product of the passage of lithium ions was observed. With the results it is possible to conclude that the operation of lithium-ion batteries is optimized at 25ºC, were impedance decrease as well as the degradation of the components.
| Speaker Country | Chile |
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