Universal Li-Ion Cell Electro-Thermal Model

This paper describes and verifies a Li-ion cell electro-thermal model and the associated data analysis process. It is designed to be adaptable and give accurate results across all variations of operating conditions and cell design based only on time domain voltage, current and temperature measurements. The creation of this model required an analysis process ensuring consistency in expressing the underlying cell behavior. This informed a flexible modelling structure adaptable both to cell performance variations and the limitations of the available test data. The model has been created with a combined thermal and electrical approach enabling 1D nodal distribution adaptable to both cylindrical and prismatic cells. These features combine with an intelligent parameter identification process identifying model structure and parameterization across the usage range, adaptable to any Nickel-Manganese-Cobalt Li-Ion cell. It is designed to retain physical meaning and representation to each circuit element across the temperature operating range. The model is verified in several different operating conditions through representative automotive cycling on an 18650 cell and a BEV2 format prismatic cell, representing the extremes of automotive cell design. The consistency of the model parameters with real phenomena is also analyzed and validated against Electrochemical Impedance Spectroscopy data

Operando ultrasonic monitoring of the internal temperature of lithium-ion batteries for the detection and prevention of thermal runaway

Lithium-ion batteries (LIBs) play an integral role in powering various applications, from consumer electronics to stationary storage, and notably in the accelerating domain of electric vehicles (EVs). Despite their widespread adoption and numerous benefits, safety issues are of major concern, especially with the surge in their utilization and increasing proliferation of second-life cells, particularly in domestic energy storage applications. A critical concern revolves around susceptibility to thermal runaway, leading to highly hazardous and challenging-to-contain fires. Addressing these concerns necessitates effective methods to monitor internal temperature dynamics within lithium-ion cells swiftly and cost-effectively, alongside a need to develop prognostic techniques to pre-empt thermal runaway occurrences. This study presents an innovative approach that uses ultrasound analysis to track intricate internal temperature fluctuations and gradients within cells. Moreover, an efficient multi-stage warning system is proposed that is designed to proactively prevent thermal runaway events. The findings offer promising avenues for enhancing the safety and reliability of lithium-ion battery systems

Operando ultrasonic monitoring of lithium-ion battery temperature and behaviour at different cycling rates and under drive cycle conditions

Effective diagnostic techniques for Li-ion batteries are vital to ensure that they operate in the required voltage and temperature window to prevent premature degradation and failure. Ultrasonic analysis has been gaining significant attention as a low cost, fast, non-destructive, operando technique for assessing the state-of-charge and state-of-health of Li-ion batteries. Thus far, the majority of studies have focused on a single C-rate at relatively low charge and discharge currents, and as such the relationship between the changing acoustic signal and C-rate is not well understood. In this work, the effect of cell temperature on the acoustic signal is studied and shown to have a strong correlation with the signal's time-of-flight. This correlation allows for the cell temperature to be inferred using ultrasound and to compensate for these effects to accurately predict the state-of-charge regardless of the C-rate at which the cell is being cycled. Ultrasonic state-of-charge monitoring of a cell during a drive cycle illustrates the suitability of this technique to be applied in real-world situations, an important step in the implementation of this technique in battery management systems with the potential to improve pack safety, performance, and efficiency

Identifying Defects in Li-Ion Cells Using Ultrasound Acoustic Measurements

Identification of the state-of-health (SoH) of Li-ion cells is a vital tool to protect operating battery packs against accelerated degradation and failure. This is becoming increasingly important as the energy and power densities demanded by batteries and the economic costs of packs increase. Here, ultrasonic time-of-flight analysis is performed to demonstrate the technique as a tool for the identification of a range of defects and SoH in Li-ion cells. Analysis of large, purpose-built defects across multiple length scales is performed in pouch cells. The technique is then demonstrated to detect a microscale defect in a commercial cell, which is validated by examining the acoustic transmission signal through the cell. The location and scale of the defects are confirmed using X-ray computed tomography, which also provides information pertaining to the layered structure of the cells. The demonstration of this technique as a methodology for obtaining direct, non-destructive, depth-resolved measurements of the condition of electrode layers highlights the potential application of acoustic methods in real-time diagnostics for SoH monitoring and manufacturing processes

Advanced Virgo Plus: Future Perspectives

While completing the commissioning phase to prepare the Virgo interferometer for the next joint Observation Run (O4), the Virgo collaboration is also finalizing the design of the next upgrades to the detector to be employed in the following Observation Run (O5). The major upgrade will concern decreasing the thermal noise limit, which will imply using very large test masses and increased laser beam size. But this will not be the only upgrade to be implemented in the break between the O4 and O5 observation runs to increase the Virgo detector strain sensitivity. The paper will cover the challenges linked to this upgrade and implications on the detector's reach and observational potential, reflecting the talk given at 12th Cosmic Ray International Seminar - CRIS 2022 held in September 2022 in Napoli

The Advanced Virgo+ status

The gravitational wave detector Advanced Virgo+ is currently in the commissioning phase in view of the fourth Observing Run (O4). The major upgrades with respect to the Advanced Virgo configuration are the implementation of an additional recycling cavity, the Signal Recycling cavity (SRC), at the output of the interferometer to broaden the sensitivity band and the Frequency Dependent Squeezing (FDS) to reduce quantum noise at all frequencies. The main difference of the Advanced Virgo + detector with respect to the LIGO detectors is the presence of marginally stable recycling cavities, with respect to the stable recycling cavities present in the LIGO detectors, which increases the difficulties in controlling the interferometer in presence of defects (both thermal and cold defects). This work will focus on the interferometer commissioning, highlighting the control challenges to maintain the detector in the working point which maximizes the sensitivity and the duty cycle for scientific data taking

Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector

In this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285 m long, high-finesse, near-detuned optical resonator. With about 8.5 dB of generated squeezing, up to 5.6 dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2 dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6 Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5 dB and 2 dB, respectively

Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector

In this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285 m long, high-finesse, near-detuned optical resonator. With about 8.5 dB of generated squeezing, up to 5.6 dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2 dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6 Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5 dB and 2 dB, respectively

Open Data from the Third Observing Run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages

Search for Eccentric Black Hole Coalescences during the Third Observing Run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.Comment: 24 pages, 5 figure