Evolved gas analysis techniques are currently used because the possibility to on-line detect the nature of the released gases has become fundamental to proving a supposed reaction, either under isothermal or under heating conditions. Among the various technique, the Fourier Transformation-Infrared Spectroscopy (FT-IR) is a well-established method for gas analysis. In this project the FT-IR technique will be utilized for investigating the safety behavior of Li-ion batteries (LIB).
With continued advances in battery technologies, batteries have become one of the leading solutions for not only portable power application, but also automotive and energy storage applications. Because of the high energy density in advanced batteries, one key safety goal is preventing the unintended release of storage energy.
A catastrophic failure of a battery pack can occur if one or more cells in the battery pack undergo a thermal runaway event that results in a rapid release of flammable gases and heat, which can potentially result in fire and explosions. The design of effective thermal management systems or fire mitigation systems requires proper quantification of the thermal failure characteristics.
Single-cell abuse tests are a valuable tool for assessing the safety behavior of LIBs. Chemical analyses of emitted compounds are essential for a risk analysis. Due to the exposure pathway on human health, gaseous compounds are of particular importance. A quantitative analysis is especially necessary to relate the results of laboratory tests to exposure scenarios of LIB application.
This project wants detail the gas evolution reactions during abuse tests and present the thermal runaway mechanism. The flammability characteristics of the gases vented from battery failure will be also evaluated to propose a method to change its flammability characteristics. To this aim commercial LiBs with different chemistry and geometries will be investigated at different state of charges.
For many years, the main factor preventing Fourier Transform Infrared Spectroscopy analysis from becoming more commonplace was the long computation time required for the Fourier transformation, a mathematical tool that converts a time-domain signal to a frequency-domain signal. However, the invention of a fast Fourier transform algorithm and advances in digital signal processing have made it practical to build small, low-cost FT-IR spectrometers capable of rapidly measuring a complete mid-IR spectrum with moderate to high resolution and very good signal-to-noise ratio. Coupled with advanced algorithms for identification and quantification of the chemical species represented in the spectrum, modern gas and vapor FT-IR analyzers can identify multiple unknowns and can quantify components of complex gas-phase mixtures containing dozens of volatile organic compounds.
Nowadays infrared spectroscopy is a powerful technique widely used in many fields such as industry, environmental control, food, agriculture, geology, medical and pharmaceutical. Its ability to measure almost any gas, combined with the robustness and reliability of the technology, enable FT-IR to be employed in a wide variety of applications. It is an excellent tool for qualitative and quantitative analysis and due to its rapidity and environmentally friendly characteristics is the best method in the area of green analytical chemistry.
Infrared spectroscopy is based on the principle that molecular bond vibrations, excited by radiation of a proper frequency, can adsorb infrared radiation according to their characteristic functional group, in the range of electromagnetic radiation.
The spectrum obtained by infrared spectroscopy, represents the fingerprint of a sample. It consists of peaks corresponding to the frequencies of vibrations between the bonds of the atoms of the material. As the compounds are made of a unique combination of atoms, their infrared profiles make them unequable recognizable. This technique coupled to modern software algorithms is an excellent tool to characterize solids, liquids, or gaseous samples with the aid of different accessories depending on the physical state.
Nowadays, FT-IR makes use of low-cost FT-IR spectrometers capable of collecting a wide range of wavelength information, (from 700 to 400000 nm and wave numbers from 14000 to 25 cm-1), simultaneously, rapidly measuring a complete spectrum with moderate to high resolution and very good signal-to-noise ratio and continuously. The ultimate tools offer high sensitivity and improve spectral precision and reproducibility. Moreover, FT-IR is a non-destructive technique and provides the quantification of many compounds in a wide range of concentrations within a single measurement.
Modern gas and vapor FT-IR analyzers can be used for the identification and quantification of species in complex multi-component gas mixtures, and it is the best choice over the other gas analyzers and older IR technology because of the use of simple optical modulator, device that can monitor changes in sample concentrations to transient over time events by performing fast measures and many scans per second.
The FT-IR instrument is sensitive to changes in molecular structure and it is the best approach for on-line gas analysis. The possibility to carry out on-line measurements allows to overcome many difficulties. Traditionally, to collect data during a reaction, samples are taken for off-line analysis and this can cause the not representativity of the sample, damage for the operator if the compound is toxic or hazardous, the changing in the reaction and the loss of key information of the process.
The new generation FT-IR equipment collect data automatically, generating concentration information over time. In this way it is possible to carry out a few experiments and the research is accelerated. Moreover, the data are more accurate than those obtained by other offline technique because the preparative phase of the sample with its exposure to the environment is not required.
The presence of such versatile instrument would make the laboratory modern, fast and innovative and would allow synergy between research facilities in the department.
This type of instrumentation is ideal for analysis of the emitted gases coming from the abuse tests on lithium-ion cells.