In Situ Ultrasound Acoustic Measurement of the Lithium-Ion Battery Electrode Drying Process

Advances in acoustic techniques for evaluating defects and properties in lithium-ion batteries: A review

With the rapid demand for high-performance energy storage systems, lithium-ion batteries (LiBs) have emerged as the predominant technology in various applications. However, ensuring the safety and reliability of these batteries remains a critical challenge. Ultrasound-based detection, as a non-destructive and effective method for monitoring the internal state of LiBs, has gradually emerged as a valuable tool to enhance battery safety, reliability, and performance. This paper provides a review of recent advancements in the field of acoustic detection for LiBs, delving into the fundamental principles and mechanisms governing the propagation of acoustic signals within these batteries. This paper reviews the correlation between these acoustic signals and the operational status of the battery, as well as the association with internal side reactions during abnormal conditions. The strengths and limitations of current ultrasound-based detection methods are emphasized, offering insights to guide researchers, engineers, and industry professionals in advancing the field. The review aims to foster the development of robust ultrasound-based detection solutions for the next generation of energy storage systems.

Molecular Rotors for In Situ Viscosity Mapping during Evaporation of Confined Fluid Mixtures

Numerous formulation processes of materials involve a drying step, during which evaporation of a solvent from a multicomponent liquid mixture, often confined in a thin film or in a droplet, leads to concentration and assembly of nonvolatile compounds. While the basic phenomena ruling evaporation dynamics are known, precise modeling of practical situations is hindered by the lack of tools for local and time-resolved mapping of concentration fields in such confined systems. In this article, the use of fluorescence lifetime imaging microscopy and of fluorescent molecular rotors is introduced as a versatile, in situ, and quantitative method to map viscosity and concentration fields in confined, evaporating liquids. More precisely, the cases of drying of a suspended liquid film and of a sessile droplet of mixtures of fructose and water are investigated. Measured viscosity and concentration fields allow characterization of drying dynamics, in agreement with simple modeling of the evaporation process.

Excellent-Moisture-Resistance Fluorinated Polyimide Composite Film and Self-Powered Acoustic Sensing

As a clean, sustainable energy source, sound can carry a wealth of information and play a huge role in the Internet of Things era. In recent years, triboelectric acoustic sensors have received increasing attention due to the advantages of self-power supply and high sensitivity. However, the triboelectric charge is susceptible to ambient humidity, which reduces the reliability of the sensor and limits the application scenarios significantly. In this paper, a highly moisture-resistant fluorinated polyimide composited with an amorphous fluoropolymer film was prepared. The charge injection performance, triboelectric performance, and moisture resistance of the composite film were investigated. In addition, we developed a self-powered, highly sensitive, and moisture-resistant porous-structure acoustic sensor based on contact electrification. The detection characteristics of the acoustic sensor are also obtained.

Compressibility of Lithium Hexafluorophosphate Solutions in Two Carbonate Solvents

Speed-of-sound measurements are performed to establish how the isentropic bulk modulus K _s of the electrolyte system comprising lithium hexafluorophospate (LiPF₆) in blends of propylene carbonate (PC) and ethyl methyl carbonate (EMC) varies with salt molality m, mass fraction of PC in the PC:EMC cosolvent f, and temperature T. Bulk moduli are calculated by combining acoustic time-of-flight data between parallel walls of a liquid-filled cuvette with densitometric data for a sequence of binary and ternary salt solutions. Correlations are presented to yield K _s (m, f, T) accurately for nine compositions spanning the range m = 0-2 mol kg^-1 and f = 0-1, at temperatures T ranging from 283.15 to 313.15 K. Electrolyte compressibility varies most with solvent ratio, followed by salt content and temperature, with K _s ranging from 1 to 3 GPa. Composition-dependent acoustical properties elucidate the nature of speciation and solvation states in bulk electrolytes, and could be useful to identify the features of individual phases within solution-permeated porous electrodes.

Effective Ultrasound Acoustic Measurement to Monitor the Lithium-Ion Battery Electrode Drying Process with Various Coating Thicknesses

The electrode drying process (DP) is a crucial step in the lithium-ion battery manufacturing chain and plays a fundamental role in governing the performance of the cells. The DP is extremely complex, with the dynamics and their implication in the production of electrodes generally being poorly understood. To date, there is limited discussion of these processes in the literature due to the limitation of the existing in situ metrology. Here, ultrasound acoustic measurements are demonstrated as a promising tool to monitor the physical evolution of the electrode coating in situ. These observations are validated by gravimetric analysis to show the feasibility of the technique to monitor the DP and identify the three different drying stages. A possible application of this technique is to adjust the drying rates based upon the ultrasound readings at different drying stages and to speed up the drying time. These findings prove that this measurement can be used as a cost-effective and simple tool to provide characteristic diagnostics of the electrode, which can be applied in large-scale coating manufacturing.