Ing. Zbyněk Plachý

The rapid adoption of electric vehicles (EVs) has increased the demand for efficient methods to assess the state of health (SoH) of lithium-ion batteries (LIBs). Accurate and prompt evaluations are essential for safety, battery life extension, and performance optimization. While traditional techniques such as electrochemical impedance spectroscopy (EIS) are commonly used to monitor battery degradation, acoustic emission (AE) analysis is emerging as a promising complementary method. AE’s sensitivity to mechanical changes within the battery structure offers significant advantages, including speed and non-destructive assessment, enabling evaluations without disassembly. This capability is particularly beneficial for diagnosing second-life batteries and streamlining decision-making regarding the management of used batteries. Moreover, AE enhances diagnostics by facilitating early detection of potential issues, optimizing maintenance, and improving the reliability and longevity of battery systems. Importantly, AE is a non-destructive technique and belongs to the passive method category, as it does not introduce any external energy into the system but instead detects naturally occurring acoustic signals during the battery’s operation. Integrating AE with other analytical techniques can create a comprehensive tool for continuous battery condition monitoring and predictive maintenance, which is crucial in applications where battery reliability is vital, such as in EVs and energy storage systems. This review not only examines the potential of AE techniques in battery health monitoring but also underscores the need for further research and adoption of these techniques, encouraging the academic community and industry professionals to explore and implement these methods. © 2025 by the authors.

The importance of board-level underfill has increased significantly in modern electronics. One of the primary issues with underfill is the formation of voids, with moisture-related ones being one of the top three causes. This presents a significant challenge in surface mount technology production, significantly affecting the quality and reliability of the assembly. This work investigates the impact of several factors on void formation, including printed circuit board (PCB) exposure to moisture, drilled holes in the PCB, and using an underfilled syringe nearing the end of its floor life. The findings identify the most common diameter of moisture-related voids in board-level underfill and highlight the influence of individual parameters on their formation. Studies have revealed that the formation of voids is influenced not only by moisture exposure in materials but also by the design of the board and the drilled technological non-plated through hole (NPTH) vias within it. Similarly, using an underfill syringe at the third quarter of its guaranteed floor life leads to an increase in void formation. Using scanning acoustic microscopy (SAM) in this work, 38% more voids were detected than with cross-section optical evaluation.

The significant deployment of lithium-ion batteries (LIBs) within a wide application field covering small consumer electronics, light and heavy means of transport, such as e-bikes, e-scooters, and electric vehicles (EVs), or energy storage stationary systems will inevitably lead to generating notable amounts of spent batteries in the coming years. Considering the environmental perspective, material resource sustainability, and terms of the circular economy, recycling represents a highly prospective strategy for LIB end-of-life (EOL) management. In contrast with traditional, large-scale, implemented recycling methods, such as pyrometallurgy or hydrometallurgy, direct recycling technology constitutes a promising solution for LIB EOL treatment with outstanding environmental benefits, including reduction of energy consumption and emission footprint, and weighty economic viability. This work comprehensively assesses the limitations and challenges of state-of-the-art, implemented direct recycling methods for spent LIB cathode and anode material treatment. The introduced approaches include solid-state sintering, electrochemical relithiation in organic and aqueous electrolytes, and ionothermal, solution, and eutectic relithiation methods. Since most direct recycling techniques are still being developed and implemented primarily on a laboratory scale, this review identifies and discusses potential areas for optimization to facilitate forthcoming large-scale industrial implementation.

It is well known that the reflow temperature profile has an influence on the thickness of intermetallic layers. The higher the thermal treatment, especially above the melting temperature of solder alloy, the higher the thickness of intermetallic layers. The heating factor (time-temperature integral of temperature profile above the melting temperature) is commonly used for comparison of the heat treatment. This paper deals with a comparison of three different reflow temperature profiles (with three different heating factors: 242, 1061 and 1652 s.K), three surface finishes (Organic Solderability Preservative - OSP, Hot Air Solder Leveling - HASL and Electroless Nickel Immersion Gold - ENIG) of copper soldering pads and two solder pastes with the same composition of solder alloy (Sn96,5/Ag3,0/Cu0,5) but with different flux type (less aggressive - ROL0 and more aggressive - ROL1). The cross-sections of the samples were prepared after the reflow soldering process, followed by analysis by scanning electron microscope and measurement of intermetallic layers thicknesses. Results confirmed that the heating factor significantly influences the intermetallic layers. The highest thickness of intermetallic layers was achieved with the highest value of the heating factor. The surface finish HASL had the highest values of intermetallic layer thicknesses from all used surface finishes, whereas ENIG had the lowest. The higher values of intermetallic layer thickness were observed for the solder paste with a more aggressive flux, ROL1, than for ROL0.

Recycling lithium-ion batteries (LIBs) is crucial for environmental sustainability and resource conservation. However, current recycling procedures, particularly for smaller battery formats, pose several challenges. With the increasing demands of the circular economy for LIB waste treatment, it is essential to identify and address obstacles associated with concurrent processes. Thus, this study focuses on characterizing and examining the dilemmas of electrochemical discharging of cylindrical LIB cells. It primarily examines the quantity and composition of released battery mass from nickel-aluminium-cobalt (NCA) LIB cells using aqueous discharging via solutions of sodium chloride (NaCl), sodium hydroxide (NaOH), and sodium nitrate (NaNO3) within the 5-30 wt. % range. Additionally, the work monitored several procedure parameters, including the voltage profiles during discharging, the extent of battery contacts and casing damage after discharging, the character and material composition of the obtained battery mass, and the composition of the wastewater obtained after separating the solid product from waste solutions. Consequently, it was determined that the industrial implementation of these procedures, including material leakage and disposal, may incur economic losses of up to 1560 USD/tonne due to metal loss.

The present paper introduces a novel, sustainable approach to produce an eco-friendly Printed Circuit Board (PCB) substrate; a substitute for traditional substrates, to significantly reduce e-waste. We present the prepreg technology, the road to actual circuit assembly with application studies, life cycle analysis (LCA), and sustainability analysis. The flame-retarded prepregs and resulting PCB assemblies were based on polylactic acid (PLA), the structure is reinforced with flax textiles. After copper lamination, subtractive PCB production was performed, and thermal and mechanical reliability was investigated in the case of both laminated and bare substrates. Steps of surface roughness, peel and thermal analysis followed. After a new set of assemblies, the post-assembly analysis was extended with further shear strength analysis on the soldered components and mass analysis regarding thermal processes. The evaluation showed that PLA/Flax substrates provide reliable structural performance up to 200 ◦C in the reflow soldering process; this allows limited but stabilized application possibilities with specific eco-friendly lead-free solders. A basic blinker circuit and a field programmable gate array (FPGA)– based design was produced and tested; the latter has the general complexity of a commercial circuit. A vol% and wt% analysis extended our discussion with a reduction of harmful components in waste in the range of 90%, which is a disruptive and significant result. Life cycle analysis (LCA) quantified the ecological impact of the assembly, highlighting a significant ease on environmental load (~10%) for the total assembly. Finally, a qualitative degradation study was introduced to the prepared samples to investigate short-term stability with mechanical-, colour-, mass- and scanning electron microscopy (structure) analysis. Early results show that the boards can withstand the harsh environment of a composting bin for a few days, but in the time of a few weeks, degradation starts, pointing to eventual decomposition. The work directly connects with multiple sustainability development goals.

Battery recycling involves the recovery of materials from end-of-life (EOL) batteries, which are subsequently reused in the manufacturing of new products. Metals such as cobalt, lithium, nickel, manganese, aluminium, and copper are essential components of the electrodes of common lithium-ion batteries. In light of the growing demand for advancements in battery recycling, there is a critical need to start systematically documenting the chemistry of different types of batteries and to monitor the changes within their internal composition between the different states of charge, such as full charge, full discharge, deep discharge or shipping-state. In this work, a new methodology for a complex, quick, cheap, and effective material composition survey is presented. This methodology was applied to three types of cylindrical (18650) cells with two different cathode materials, specifically nickel cobalt aluminium (NCA) and nickel manganese cobalt (NMC), all with a capacity range from 3350 to 3500 mAh. This work offers a comprehensive, step-by-step description of the versatile battery research process, serving as the foundation for a streamlined and effective methodology for obtaining selected chemical and material parameters. The research endeavours to compare the material composition of lithium-ion cells at various states of charge to assess recycling potential and establish a database containing battery parameters. The results are essential for the automation and roboticization of the advanced recycling sector.

This work is devoted to investigating the effect of flux residues on the underfill. Prepared samples were made of copper sheets to eliminate the influence of multi-layered, inhomogeneous materials. Two sets of these samples were designed for this work; where one set was cleaned in an isopropyl alcohol bath in an ultrasonic cleaner, and the other was left uncleaned to highlight the presence of flux. Underfill was applied to both sets of samples, and the assemblies created in this way were subjected to several diagnostic methods. The work results showed that even when no-clean flux was used, its residues remained on the base substrates, contaminating the underfill or preventing it from completely filling the gap. The ultrasonic cleaner proved to be a suitable method for cleaning the samples, thus, eliminating the influence of flux residues or other impurities on the underfill. Furthermore, mechanical tests indicated that non-cleaned samples are characterized by a greater dispersion in mechanical properties than cleaned ones. Therefore, eliminating the influence of the flux will allow us to achieve more accurate results in the underfill's effect on the reliability of the assembly, which will allow a better potential comparison of different methods of underfill application and other materials.

Environmental concerns push for a reduction in greenhouse gas emissions and technologies with a low carbon footprint. In the transportation sector, this drives the transition toward electric vehicles (EVs), which are nowadays mainly based on lithium-ion batteries (LIBs). As the number of produced EVs is rapidly growing, a large amount of waste batteries is expected in the future. Recycling seems to be one of the most promising end-of-life (EOL) methods; it reduces raw material consumption in battery production and the environmental burden. Thus, this work introduces a comprehensive pre-recycling material characterization of waste nickel-manganese-cobalt (NMC) LIB cells from a fully electric battery electric vehicle (BEV), which represents a basis for cost-effective and environmentally friendly recycling focusing on the efficiency of the implemented technique. The composition of the NCM 622 battery cell was determined; it included a LiNi0.6Co0.2Mn0.2O2 spinel on a 15 μm Al-based current collector (cathode), a graphite layer on 60 μm copper foil (anode), 25 μm PE/PVDF polymer separator, and a LiPF6 salt electrolyte with a 1:3 ratio in primary solvents DMC and DEC. The performed research was based on a series of X-ray, infrared (IR) measurements, gas chromatography–mass spectrometry (GC-MS), and inductively coupled plasma–optical emission spectrometry (ICP-OES) characterization of an aqueous solution with dissolved electrolytes. These results will be used in subsequent works devoted to optimizing the most suitable recycling technique considering the environmental and economic perspectives.

The popularity of lithium-ion batteries (LIBs) as crucial power sources has increased in recent years. LIBs represent a perspective technology for recycling because they comprise a high portion of valuable metals, such as nickel, manganese, cobalt, or lithium, and other metals, including aluminium, copper, and iron. Battery discharging represents an essential step in end-of-life (EOL) pretreatment, as it reduces the risk of fire or explosion in further processing. As a simple, quick, and inexpensive technique, an electrochemical discharging process via salt-based solutions is preferred for cylindrical cells. Nevertheless, it is necessary to consider the composition of obtained waste products and the possible environmental risks leading to their safe and non-hazardous EOL processing. This work evaluated discharging efficiency and environmental perspective for cylindrical LIB cells, which were treated using NaCl solution. All battery cells were discharged to the safe voltage limit (0.75 V) within 24 hours. Major organic components, including volatile solvents with high toxic hazards, such as carbonic acid esters, methyl salicylate, and propanoic acid esters, were identified in the waste solutions using gas chromatography with mass spectrometry (GC-MS). Moreover, the metal proportion in the solution was determined using inductively coupled plasma - optical emission spectrometry (ICP-OES) analysis; it is recommended to recover metals from the wastewater before EOL or cleaning treatment.

The wetting balance method is used for the precise classification of solderability of chosen substrates by solder alloys. This work deals with a weakness of the wetting balance method during the wettability measurement of connectors with the wetting issue. The wetting issues at examined pins connector appeared during the serial manufacturing production, and therefore, the connector pins were analysed using the wetting balance method. The wetting balance method showed a good wetting of the connector pins. The wetted pins were examined by scanning electron microscopy (SEM) to find the reason for the wetting issue. This analysis showed a non-wetted area at pins edges. Following investigation of pins microsections using confocal/optical microscopy showed the reason for the wetting issue, when the surface finish was much thinner or was missing on the edges of the pin. This was the reason for the wetting issue of the connector pins in serial manufacturing, even though the wetting balance test showed good wettability results because most parts of the pin surface had good wetting.

Humidity is an essential and integral part of human life, of which electrical equipment and devices are already an integral part. The moisture problem is mainly associated with components in non-hermetic plastic packages. Understanding the behavior of these components is a basic prerequisite for proper handling during the manufacturing process. By proper handling of the components, various moisture-related defects can be avoided. For these reasons, moisture sensitive devices (MSD) are divided into different moisture sensitivity levels (MSL), which indicate their floor life. The main danger associated with moisture does not lie in its absorption itself, but in the mechanical stress caused by the rapid expansion of the evaporated water in a relatively short time during the reflow soldering process. Defects associated with delamination and cracks of the component packages are one of the most common defects in surface mounting technology. If the absorbed moisture does not cause mechanical defects during production within the Surface Mount Technology (SMT), it can further accelerate the degradation phenomena of the device. The results of this work clearly show that components exposed to environments with higher relative humidity (RH) absorb more moisture than the same components at lower RH. By reducing RH, the risk associated with defects caused by mishandling MSDs can also be reduced.