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Lithium-ion batteries (LIBs) have emerged as important power sources in recent years, and their improved performance is accelerating the adoption of electric vehicles (EVs) as viable alternatives to internal combustion engines. A focal point for the international community of materials scientists, computational physicists, and chemists is the exploration of innovative materials for LIBs, with an overarching emphasis on addressing concerns related to safety, durability, energy density (ED), and affordability during the developmental stages. The electrolyte, serving as a solvent containing conducting salt and additional substances, plays a critical role, while the incorporation of additives is explored to enhance security, performance, and recyclability. To meet the multifaceted demands of automotive and grid applications, batteries necessitate advancements in power, durability, safety, environmental sustainability, and cost-effectiveness. Overcoming challenges associated with current LIBs, primarily those crafted from flammable and volatile organic solvents, becomes imperative. Addressing issues such as large electrochemical windows (Ews), a broad working temperature range, appropriate safety measures, and optimal surface reactions on electrodes for controlled passivation without compromising low impedance are formidable tasks. This review aims to comprehensively diverse LIB electrolyte types, facilitating the development of enhanced electrolytes for high-performance LIBs. Furthermore, it advocates for the design and implementation of safer electrolytes in future LIB iterations. The exploration of electrolyte additives is also a subject of investigation. The conclusion underscores the imperative to consider cell longevity when devising electrolytes for applications requiring rapid charging. [ABSTRACT FROM AUTHOR]

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In order to make electric transportation more accessible, the cost of lithium‐ion batteries must decrease. One way to achieve this is by increasing the production rates, especially in the time‐consuming steps of electrolyte filling and cell formation. Within this work, lithium‐ion pouch and hardcase cells are filled with electrolyte and the formation is started at varying wetting degrees. Data from the formation, stabilization, and life cycle testing are analyzed to determine the effect of an incomplete wetting degree on the cell quality. Additionally, postmortem analysis is performed to help understand the mechanisms induced when a cell with incomplete wetting is subjected to a current. The pouch cells demonstrate a linear capacity fade, regardless of the wetting degree, but feature strong lithium plating which becomes visible during postmortem analysis. In contrast, the hardcase cells display a clear correlation between the cell quality and the wetting degree in both the life cycle test and the postmortem analysis. It is shown that a wetting degree of 98% is required before starting the formation to avoid lithium plating in the cell. [ABSTRACT FROM AUTHOR]

Electrolyte filling and wetting is a quality-critical and cost-intensive process step of battery cell production. Due to the importance of this process, a steadily increasing number of publications is emerging for its different influences and factors. We conducted a systematic literature review to identify common parameters that influence wetting behavior in experimental settings, specifically focusing on material, processes, and experimental measurement methods but excluding simulation studies. We reduced the initially found 544 records systematically to 39 fully labeled articles. Our profound analysis guided by attributed labelings revealed current research gaps such as the lack of a holistic view on measurement methods for filling and wetting, underrepresented studies relevant to series production, as well as the negligence of research targeting the transferability of results from the material to the cell level, while also examining the measured variables' interactions. After comparatively illustrating and discussing implications of our findings, we also discussed limitations of our contribution and suggested ideas for potential further research topics. [ABSTRACT FROM AUTHOR]

Demand for lithium-ion battery cells (LIB) for electromobility has risen sharply in recent years. In order to continue to serve this growing market, large-scale production capacities require further expansion and the overall effectiveness of processes must be increased. Effectiveness can be significantly optimized through innovative manufacturing technology and by identifying scrap early in the production chain. To enable these two approaches, it is imperative to quantify safety- and function-critical product features in critical manufacturing steps through appropriate measurement techniques. The overview in this paper on quality control in LIB production illustrates the necessity for improved inspection techniques with X-rays to realize a fast, online measurement of inner features in large-scale cell assembly with short cycle times and to visualize inner product-process interactions for the optimization in electrolyte filling. Therefore, two new inspection techniques are presented that contribute to overcoming the aforementioned challenges through the targeted use of X-rays. First, based on the results of previous experiments in which the X-ray beam directions were deliberately varied, a online coordinate measurement of anode-cathode (AC) overhang was developed using a line detector. Second, a new concept and the results of a continuous 2D visualization of the electrolyte filling process are presented, which can be used in the future to optimize this time-critical process step. By using a X-ray-permeable and portable vacuum chamber it is possible to quantify the influence of process parameters on the distribution of the electrolyte in the LIB. [ABSTRACT FROM AUTHOR]

In order to meet consumer demands for electric transportation, the energy density of lithium-ion batteries (LIB) must be improved. Therefore, a trend to increase the overall size of the individual cell and to decrease the share of inactive materials is needed. The process of electrolyte filling involves the injection of electrolyte liquid into the cell, as well as the absorption of the electrolyte into the pores of the electrodes and the separator, which is known as wetting. The trend towards larger-format LIB challenges the electrolyte filling due to an increase in wetting distance for the electrolyte as well as a decrease in the void volume of the cell. The optimization of the process via numerical simulation promises to reduce costs and ensure quality during battery production. The two models developed in this study are based on a commercial computational fluid dynamics (CFD) program to study the effect of process parameters, such as pressure and temperature, on the filling process. The results were verified with neutron radiography images of the dosing process and a feasibility study for a wetting simulation is shown. For all simulations, specific recommendations are provided to set up the electrolyte filling process, based on which factors generate the greatest improvement. [ABSTRACT FROM AUTHOR]

Electrolyte filling and wetting is a quality-critical and cost-intensive process step of battery cell production. Due to the importance of this process, a steadily increasing number of publications is emerging for its different influences and factors. We conducted a systematic literature review to identify common parameters that influence wetting behavior in experimental settings, specifically focusing on material, processes, and experimental measurement methods but excluding simulation studies. We reduced the initially found 544 records systematically to 39 fully labeled articles. Our profound analysis guided by attributed labelings revealed current research gaps such as the lack of a holistic view on measurement methods for filling and wetting, underrepresented studies relevant to series production, as well as the negligence of research targeting the transferability of results from the material to the cell level, while also examining the measured variables’ interactions. After comparatively illustrating and discussing implications of our findings, we also discussed limitations of our contribution and suggested ideas for potential further research topics.

In order to meet consumer demands for electric transportation, the energy density of lithium-ion batteries (LIB) must be improved. Therefore, a trend to increase the overall size of the individual cell and to decrease the share of inactive materials is needed. The process of electrolyte filling involves the injection of electrolyte liquid into the cell, as well as the absorption of the electrolyte into the pores of the electrodes and the separator, which is known as wetting. The trend towards larger-format LIB challenges the electrolyte filling due to an increase in wetting distance for the electrolyte as well as a decrease in the void volume of the cell. The optimization of the process via numerical simulation promises to reduce costs and ensure quality during battery production. The two models developed in this study are based on a commercial computational fluid dynamics (CFD) program to study the effect of process parameters, such as pressure and temperature, on the filling process. The results were verified with neutron radiography images of the dosing process and a feasibility study for a wetting simulation is shown. For all simulations, specific recommendations are provided to set up the electrolyte filling process, based on which factors generate the greatest improvement.

The battery cell manufacturing is increasingly being digitalized to improve product quality and achieve a more transparent and efficient manufacturing process. In this paper, we apply the technology management method called "technology assessment" to the processes of electrical filling and formation of pouch cells to identify and evaluate possible digitalization measures. As a result, the digitalization measures in the process technology, logistics, quality control and energy system of the two processes are discussed and evaluated according to their potential and technology readiness level. The combination of digital twins of the battery cell with the digital factory operation is assessed as the most promising measure. [ABSTRACT FROM AUTHOR]

Lithium‐ion battery (LIB) cells of the 18650 format are built in‐house with different amounts of an electrolyte. After wetting and prior to subsequent formation, the cells are opened. The electrolyte is regained by centrifuging the entire jelly roll and quantified by a gas chromatography‐flame ionization detector (GC‐FID) and inductively coupled plasma‐optical emission spectroscopy (ICP‐OES). The influence of a filling protocol applying cycles with over‐ and reduced pressure is examined with a focus on the electrolyte composition. No significant difference is found in the ratio of linear (LC) to cyclic carbonates (CCs). Furthermore, extraction by centrifugation is investigated in different scenarios by simulating almost "dry" cells to minimize alterations during the sample preparation. The quantification of these electrolytes indicates a slightly reduced amount of LC in the sample. [ABSTRACT FROM AUTHOR]

The reduction of process time and costs of lithium‐ion‐battery (LIB) cells to make electromobility an ecological technology and economically accessible for everyone is a very crucial research topic. Within the production process of actual LIB cells, the electrolyte filling and wetting are very time‐consuming, and by association, cost‐intensive steps. Therefore, it is essential to investigate and understand the impact of several process parameters on the wetting time and product quality. This can be achieved by the visualization of the wetting progress and subsequent electrochemical characterization of the LIB cells. The monitoring is realized by wetting balance tests for electrodes and separators as well as a new and powerful thermographic method. In addition, different separators with different surface chemistries are tested to improve the production process, the actual cell design, and therefore the costs of the final battery cell. [ABSTRACT FROM AUTHOR]

In the manufacturing of Li-ion battery cells, filling with electrolyte liquid is a crucial step in terms of product quality and cost. To gain insight into the process phenomena, a non-destructive imaging method is presented. It is shown that the spreading of electrolyte liquid within the cell during filling and wetting can be visualized by neutron radiography. The experiment allows for the first time to visualize the soaking behaviour of electrolyte liquid in battery cells. The influence of the process parameters on the wetting behaviour is studied and flow paths of the liquid are identified. The electrolyte intake into the cell stack is discussed with two different analytical approaches. Based on the experimental data, the production process can be optimized, leading to stable cell performance and cost reduction due to faster processes and lower scrap rates. [ABSTRACT FROM AUTHOR]

Abstract: The effect of electrolyte filling method on the performance of the dye-sensitized solar cells is investigated with the segmented cell method, a recent technique which is very simple but effective as it can be used to examine all the photovoltaic characteristics. The electrolyte filling techniques compared were single injection, which is typically used in small laboratory cells, and pumping the electrolyte through the cell several times, which is often used for larger cells and modules. Significant photovoltage and photocurrent variations occur with the repeated pumping of the electrolyte in the cell preparation. Transient and charge extraction measurements confirmed that the differences in open circuit voltage were due to the shifts of the TiO2 conduction band and time correlated single photon counting confirmed that the reduction of short circuit current was largely due to reduced electron injection correlated with the increasing conduction band edge in the studied cases. This was interpreted as an effect of molecular filtering by the TiO2 causing an accumulation of electrolyte additives (4-tert-butylpyridine and benzimidazole) near the electrolyte filling hole, the concentration of which increased with repeated pumping of the electrolyte. Interestingly, spatial variations were seen not only in the relative TiO2 conduction band energy but also in the density of trap states. In this contribution it is demonstrated how the changes in the conduction band can be separated from the changes in the density of trap states which is an essential for the correct interpretation of the data. [Copyright &y& Elsevier]

Abstract: It is demonstrated that the molecular filtering effect of TiO2 has a significant influence on dye solar cell (DSC) performance. As electrolyte is injected to a DSC, some of the electrolyte components adsorb to the surface TiO2 (here 4-tert-butylpyridine and 1-methyl-benzimidazole) and accumulate near the electrolyte filling hole resulting in varying electrolyte composition and performance across the cell. The spatial performance distribution was investigated with a new method, the segment cell method. Not only is the segmented cell method simple and cheap when compared to the only other method for examining spatial variation (photocurrent mapping), it also has the major advantage of allowing the spatial variation in all other operating parameters to be assessed. Here the molecular filtering effect was to influence the cell performance in case of all the five studied electrolytes causing up to 35% losses in efficiency. Raman spectra indicated that the loss in photocurrent in the electrolyte filling was in correlation with the loss of thiocyanate ligands suggesting that dye regeneration may also be a significant factor in addition to electron injection in some of the cells. There were also shifts in the absorption spectra the photoelectrodes which further supported changes in the thiocyanate ligands. Besides absorption changes, there were additional shifts in the IPCE spectra which may relate to deprotonation of the dye. The efficiency losses were reduced to ∼10% with contemporary electrolyte compositions. [Copyright &y& Elsevier]

Abstract: The spatial performance variation of dye solar cell with standard liquid electrolyte was examined by dividing the cell into segments. Surprisingly large and permanent performance differences were found in different parts of the cell leading to significant losses in the overall cell efficiency. The decrease of open circuit voltage along the electrolyte filling direction suggests that 4-tert-butylpyridine is adsorbed non-uniformly as the electrolyte passes through the dyed TiO2 layer during the filling process. The result indicates that non-uniform electrolyte adsorption may limit the up-scaling of dye solar cells, which calls for the examination of electrolyte filling techniques and electrolyte compositions less prone to this effect. [Copyright &y& Elsevier]