In this study, a tailored hybrid sensing configuration integrating fiber Bragg grating and intrinsic Fabry-Perot interferometer is presented. It enables simultaneous discrimination and tracking of internal temperature and pressure changes within 18650 Li-ion batteries (LiBs). The battery undergoes rigorous cycling tests at different operating conditions and a comparison between them is presented. The optical fiber sensors instrumented into the LiB reveal, throughout overall cycling tests, a compelling correlation between internal and external temperature behavior. The application of systematic Incremental Capacity Analysis derivative curves during battery operation exposes crucial insights into the relationship between pressure and temperature physical parameters, and their electrochemical behavior. This optical sensing approach contributes in this way to a nuanced understanding of internal LiB dynamics, with implications for their optimizing performance and safety in diverse applications.
This work presents the development and application of high-birefringent optical fiber sensors for the internal monitoring of Li-ion pouch cells during their operation. The instrumented optical fiber sensing configuration simultaneously discriminates and tracks temperature and strain shifts at different and consecutive cycling operation conditions which includes a Worldwide Harmonised Light Vehicle Test Procedure. A correlation of the strain data sensed by the optical fiber sensors with the Differential Voltage Analysis of the cell is performed. This study is integrated into the INSTABAT EU-project, and it demonstrates the potential of this advanced technology based on optical fiber in the field of Li-ion cell monitoring, making a substantial contribution to the development of more sustainable energy solutions by improving their safety issues and evaluating their performance in real-time.
A Fabry Perot (FP) based fiber sensor for multiparameter measurement is proposed. The sensor is constituted by a short section of a hollow square core fiber (HSCF) spliced between a single mode fiber and a long section of a silica capillary tube. In a reflection scheme, several FP cavities are enhanced in different areas of the HSCF. In a single 439 μm long sensing head, three FP cavities are excited. Using the Fourier band-pass filter method, each cavity was individually monitored towards variations of pressure, temperature, and curvature. The maximum sensitivities of (3.23 ± 0.04) nm/MPa, (9.6 ± 0.3) pm/°C, and (-32 ± 1) pm/m-1 were obtained for pressure, temperature, and curvature, respectively within a measurement range of 0.4 MPa, 110°C, and 9 m-1. The distinct responses of the FP cavities to the measurands allow for a triple-hybrid application of the sensor towards simultaneous measurement of pressure, temperature, and curvature. The proposed sensor is robust with simple fabrication and small dimensions, revealing promising to be employed in a wide range of applications where the measurement of several physical parameters is required.
In this work, a comparison between the temperature and strain decoupling performed by a bare polarization-maintaining FBG (PM-FBG) sensor and by a hybrid sensing setup, involving the slow peak of the PM-FBG and the fringe shift of the fiber loop mirror (FLM) interferometer (FLM+FBGslow), was studied and discussed. To promote such comparison, the sensors were submitted to temperature and strain variations at the surface of a cylindrical Li-ion battery (LiB), cycling between 3.0 V and 4.2 V. The data spread of the FLM+FBGslow indicates a root mean square deviation of ± 0.1 °C and ± 7.8 με, against ± 0.5 °C and ± 9.7 με in PM-FBG, for temperature and strain, respectively. The matrixial method through the sensitivities values of each sensor was used for data processing. Although both sensing configurations showed similar trend behavior of strain and temperature variations during all the experiment, the FLM+FBGslow setup presented better accuracy when compared to the PM-FBGs, however, it could only perform measurements in all the LiB extension, while the PM-FBG could provide data regarding a specific spot of the LiB. The highest temperature and strain variations were achieved in the end of the discharge processes. Keywords: Fiber loop mirror, polarization-maintaining
In this work, an optical fiber sensing network has been developed to assess the impact of different environmental conditions on lithium batteries performance through the real time thermal monitoring. The battery is submitted to constant current charge and different discharge C-rates, under normal and abusive operating conditions. The results show that for the discharge C-rate of 5.77C, the LiB under cold and dry climates had 32.5% and 27.2% lower temperature variations, when compared with temperate climates, respectively. The higher temperature shift detected in the temperate climate was related to the battery better performance regarding discharge capacity and power capabilities.
Fiber Bragg grating sensors were attached to the surface of a rechargeable lithium battery in order to monitor its thermal and strain fluctuations through charge and different discharge C rates. During the discharge process above 1C, it were observed, a temperature and strain fluctuations of a 4.12 ± 0.67 °C and 24.64 ± 6.02 με, respectively. In the regular charge process, a temperature and strain variation of 1.03 ± 0.67 °C and 15.86 ± 6.02 με, were detected.
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