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Abstract Lithium‐sulfur batteries (LSBs) have garnered attention from both academia and industry because they can achieve high energy densities (>400 Wh kg–1), which are difficult to achieve in commercially available lithium‐ion batteries. As a preparation step for practically utilizing LSBs, there is a problem, wherein battery cycle life rapidly reduces as the loading level of the sulfur cathode increases and the electrode area expands. In this study, a separator coated with boehmite on both sides of polyethylene (hereinafter denoted as boehmite separator) is incorporated into a high‐loading Li‐S pouch battery to suppress sudden capacity drops and achieve a longer cycle life. We explore a phenomenon by which inequality is generated in regions where an electrochemical reaction occurs in the sulfur cathode during the discharging and charging of a high‐capacity Li‐S pouch battery. The boehmite separator inhibits the accumulation of sulfur‐related species on the surface of the sulfur cathode to induce an even reaction across the entire cathode and suppresses the degradation of the Li metal anode, allowing the pouch battery with an areal capacity of 8 mAh cm–2 to operate stably for 300 cycles. These results demonstrate the importance of customizing separators for the practical use of LSBs.

In this paper, the transient model of a high energy density Lithium-ion pouch battery cell is developed under dynamic conditions. The battery cell has a capacity of 73 Ah and volumetric energy density of 642 Wh L−1. This is one of the few studies included the electro-thermal behaviour of high energy density battery under transient conditions by using second ordered model. The transient model indicated that the state of charge (SOC) decreased by 7 % at the end of the WLTP driving cycle and this value is good agreement with the experimental data. Moreover, the developed model provides an accurate prediction of the terminal voltage with a R2 value of 0.99 and a maximum relative error of 2.0 %. Furthermore, the proposed model predicts the electro-thermal characteristics more precisely and the heat generation rate and the entropic term can also be determined without using measurement device. The calculated total heat emitted from battery is about 6W at 1 C-rate for constant current and the heat generation rate is a peak value of ±1.75 105 Wm−3 under dynamic conditions. By using the estimated heat generation rate, more effective cold plates will be designed for thermal management of high energy density battery cells.

The electrode tabs of pouch cells are rigidly joined to the bus bar in a battery module to achieve an electric connection. The effect of abusive mechanical loads arising from crash-related deformation or the possible movement of battery cells caused by operation-dependent thickness variations has so far never been investigated. Three quasi-static abuse tests for the anode and cathode electrode tabs were conducted with pouch cells at 100% SOC. Tensile tests on the anode, cathode and pouch foil were performed in order to explain differences between the anode and cathode in the abuse tests. The experiments revealed different failure mechanisms for the anode and cathode electrode tabs. The cathode failed at an average maximum load of 940.3 N through an external rupture of the electrode tab. The anode failed at an average maximum load of 868.9 N through a rupture of the single electrode sheets and the opening of the pouch foil. No thermal runaway occurred for either cathode or anode. The results of this study reveal a more critical failure behavior for the anode electrode tab, which can be addressed in the future by adding a predetermined breaking point and adapting the geometry of the anode electrode tab.

The scale-up of supercapacitors by electrophoretic deposition (EPD) from coin cell to pouch cell with commercially relevant mass loadings and thicknesses is reported. The use of EPD in electrode fabrication mainly reduces the interfacial resistance and increases the mechanical flexibility of the electrodes. The cycling performance or conversion efficiency can also be improved due to the highly porous EPD coatings. An exemplary investigation of activated carbon (AC) electrodes with an electrolyte comprising of tetraethylammonium tetrafluoroborate in acetonitrile is carried out. According to the general literature, EPD of AC on metal substrates has not performed well for supercapacitor electrodes unless they were thinner and with lower mass loadings than commercial requirements. As a consequence, and to redress this research gap, all the electrodes prepared in this work demonstrate high mass loadings (8 mg cm−2) and practical layer thicknesses (125 µm) and contain polyvinylidene fluoride binders with electrically conductive carbon black particles. Research investigations include: (a) impact of EPD of AC onto small (10 cm2) and large areas (50 cm2) of aluminum foil current collectors, (b) scaling-up of coin to pouch cells, and (c) the preparation of electrode coatings on both sides of the current collector for the first time using EPD for pouch cell investigations. Our research learning shows the evidence of practical cell performance, including current loading (40 A g−1), tens of thousands of successive charge and discharge operation (150,000 cycles), power (30 kW kg−1) and energy densities (10 W h kg−1), capacitance (154 F g−1), capacitance retention (80%) and coulombic efficiency (relatively close to 100%). Based upon the success of the pouch cells investigated in this work, further research studies on the use of EPD for preparing energy storage electrodes for commercial cylindrical types of supercapacitors is envisaged.

In large-format pouch cells for electric vehicles, the issues of elevated and non-uniform temperatures resulting from heat generation are intensified, necessitating the use of liquid cooling systems. The design factors of the liquid cooling system influence the maximum temperature and temperature differences in the module as well as the pumping power of the cooling system. Although it is known that these design factors interact, research on these interactions and their effects is currently lacking. In this study, the individual as well as interaction effects of design factors on the performance of the liquid cooling system for a large-format pouch cell module were investigated using design of experiment and analyzed through statistical methods. Electrochemical–thermal fluid coupled analysis was used to calculate the performance according to the design factors of the liquid cooling system. The wall and channel widths are factors that directly determine the coolant flow velocity and cooling plate heat capacity, and they exhibited major effects on all three responses. Moreover, the influence of each design factor tended to change in response to variations in the other design factors. Thus, the effects of each factor individually and of interactions between factors were quantitatively compared and evaluated for significance. The width of the walls was found to contribute the most to the maximum temperature (36.00%) and pumping power (57.56%), while the width of the channels contributed the most to the temperature difference (38.24%), indicating that they are the main influencing factors.

Battery cells experience volume changes due to intercalation and ageing processes, which may pose a challenge when integrating cells into a battery module. This study presents an innovative, numerical model, which spatially resolved predicts the time-dependent, overall mechanical behaviour of battery modules caused by volume changes in built-in cells. An already self-developed battery module model, which statically describes the three-dimensional (3D), mechanical behaviour in a 0D simulation environment, is extended by the time dimension for dynamic modelling. The existing model abilities and features are maintained, such as the inclusion of multiple size scales from the cell to module level as well as the automatized model building process for the investigation of different module designs in regard to the number and arrangement of foam pads and multiple other design parameters. The validation of the predication abilities against those of complex, commercial software solutions, which use Finite Element Analysis (FEA) in a 3D model environment, have shown good agreement regarding sensitivity, robustness and numerical stability, revealing the impact and interdependencies of model parameters as well as the numerical limits of the model. In this study, the potential of the novel model regarding computational time and resources is underlined, making it a useful and effective tool for fast optimization studies.

Metal selenides have been explored as promising sodium storage materials owing to their high theoretical capacity. However, sluggish Na+ diffusion and low electronic conductivity of selenides still hinder their practical applications. Herein, FeSe2-xSx microspheres have been prepared via a self-doping solvothermal method using NH4Fe(SO4)2 as both the Fe and S source, followed by gas phase selenization. The density functional theory calculation results reveal that S doping not only improves the Na adsorption, but also lower the diffusion energy barrier of Na atoms at the S doping sites, at the same time enhance the electronic conductivity of FeSe2-xSx. The carbon-free nature of the FeSe2-xSx microspheres results in a low specific surface area and a high tap density, leading to an initial columbic efficiency of 85.6%. Compared with pure FeSe2, such FeSe2-xSx delivers a high reversible capacity of 373.6 mAh·g−1 at a high current density of 5 ​A·g−1 after 2000 cycles and an enhanced rate performance of 305.8 mAh·g−1 at even 50 ​A·g−1. Finally, the FeSe2-xSx//NVP pouch cells have been assembled, achieving high energy and volumetric energy densities of 118 ​Wh·kg−1 and 272 ​mWh·cm−3, respectively, confirming the potential of applications for the FeSe2-xSx microspheres.

The growing demand for sodium-ion batteries (SIBs) in commercial applications has made it imperative to meet the commercial requirements. However, SIBs face significant challenges because of their poor cyclability and low reversible capacity compared with their rival lithium-ion batteries (LIBs). To address these challenges, various techniques, design strategies, surface engineering, and structural modifications have been developed to enhance the electrochemical performance of SIBs. This review focuses on recent developments in improving the electrochemical performance and cyclability of novel promising electrode materials for SIBs. We discuss several unique state-of-the-art research studies of the past five years that demonstrated excellent electrochemical performance through effective methodologies, surface modulations, and substitution of novel elements into the structure, and boosted the efficiency of the materials. Furthermore, we propose that it is important to adopt a nuanced approach when designing SIBs. Rather than copying the designs and methods used for LIBs, ideas should be absorbed from them and approaches should be tailored to meet the specific requirements of SIBs. This will enable the development of SIBs that are optimized for their intended applications and will avoid the challenges that have hindered the commercial success of earlier attempts at constructing SIBs. Thus, the key to creating high-performance SIBs is to draw inspiration from the best practices used in LIBs, while simultaneously innovating and developing new approaches tailored to the unique characteristics of SIBs.

When designing the battery of an electric vehicle, different parameters must be considered to obtain the safest arrangement of the battery/modules/cells from the mechanical and thermal points of view. In this study, the thermal runaway propagation mechanism of lithium-ion cells is analyzed as a function of their arrangement within a battery pack in case of a fire propagation of a battery pack in which a thermal runaway has occurred. The objective is to identify which cell/module arrangement is most critical within the battery pack, using microscopic analysis of the structure and chemical composition of the most damaged cells, both horizontally and vertically, of a battery belonging to a burnt vehicle. And their final condition was compared with the condition of new cells of the same type. In this way, the structure and chemical composition of the cathode, anode, and separator after thermal runaway were compared. This research was carried out to obtain information to understand the mechanical properties of lithium-ion cells and their behavior after thermal runaway heating leading to the propagation of a fire. Through the analysis carried out, it is concluded that cells placed in a vertical arrangement have worse behavior than cells in a horizontal arrangement. Regarding the safety of the battery, the results of this study will allow us to determine which arrangement and structure of the cells in the battery pack is safer against thermal runaway due to thermal failure.

Thermal monitoring of lithium-ion batteries ensures their safe and optimal operation. To collect the most accurate temperature data of LIBs, previous studies used thermocouples in the cell and proved them to be technically viable. However, the cost and scale-up limitations of this method restricted its use in many applications, hindering its mass adoption. This work developed a low-cost and scalable screen-printed carbon black thermocouple to study its applicability for the thermal monitoring of LIB. Given the appropriate manufacturing parameters, it was found that thermal sensors may be printed on the electrodes, installed on a pouch cell, and once calibrated, operate with excellent sensitivity. However, to reliably use a printed carbon black thermocouple in operando of a pouch cell, its chemical resistance against electrolytes was found to require further development.

Lithium-ion batteries have a wide range of usage areas, from transportation to the defense industry, from daily usage to space applications. The widespread use of consumer electronics day by day also increases the need for this critical strategic technology, which allows us to live at almost every point of our lives without binding factors such as cables. But this technology also has many limitations, which dominate our lives so much that it needs to be overcome. Low cycle life due to poor electrochemical efficiency of electrode materials is one of these limitations. At the same time, energy density constraints are also an obstacle to many technological developments. Therefore, finding new materials with higher capacity and higher cycle life has become inevitable to meet the demands. Moreover, developing novel production techniques suitable for the materials used in the battery is also critical. Cylindrical cells are mostly used commercially in the market due to their easy and fast production technics and relatively safe components. However, the energy density and capacity limit of this architecture pushes the market to use alternative cell designs. There are different cell structures in the lithium-ion battery industry apart from cylindrical cells, such as button type, pouch type, and prismatic type. Among them, pouch cells have rising star geometry due to their unique properties and flexible production style. But many parameters still need to be overcome in pouch cells. In this study, the NMC811 cathode has been selected to investigate some critical parameters in lithium-ion pouch cells. The effects of dynamic conditions such as electrode film thickness, variable temperatures, and current rates on electrochemical performance were analyzed. Finally, a cycle life test was performed on the cell with optimum parameters.

Pressure on electrodes in cells is crucial for improving their active material density and electronic conductivity. A single-layer pouch cell (60 mAh) was fabricated to study the electrochemical effects of external pressures ranging from 0 to 3 MPa. The high-pressure cell at 3 MPa presented poor capacity retention owing to Li plating and pore-clogging on the graphite electrode. However, the optimized pressed cell did not hinder Li-ion transport in the graphite anode and underwent 200 cycles with 82 % capacity retention. External pressure impacts the contact between the electrodes and electrolyte; however, excessive pressure makes it difficult to supplement Li ions from the electrolyte into the graphite anode, resulting in increased polarization, electrolyte side reactions, and Li-metal deposition.

Lithium-ion batteries are widely used in mobile applications because they offer a suitable package of characteristics in terms of specific energy, cost, and life span. Nevertheless, they have the potential to experience thermal runaway (TR), the prevention and containment of which require safety measures and intensive thermal management. This study introduces a novel combined thermal management and safety application designed for large aspect-ratio battery cells such as pouches and thin prismatics. It comprises polymer-based mini-channel cold plates that can indirectly thermally condition the batteries’ faces with liquid. They are lightweight and space-saving, making them suitable for mobile systems. Furthermore, this study experimentally clarifies to which extent the application of polymer mini-channel cold plates between battery cells is suitable to delay TR by heat dissipation and to prevent thermal runaway propagation (TRP) to adjacent cells by simultaneously acting as a thermal barrier. NMC pouch cells of 12.5 Ah capacity were overcharged at 1 C to induce TR. Without cold plates, TR and TRP occurred within one hour. Utilizing the polymer mini-channel cold plates for face cooling, the overcharge did not produce a condition leading to cell fire in the same time frame. When the fluid inlet temperature was varied between 5 and 40 °C, the overcharged cell’s surface temperature peaked between 50 and 60 °C. Indications were found that thermal conditioning with the polymer cold plates significantly slowed down parts of the process chain before cell firing. Their peak performance was measured to be just under 2.2 kW/m2. In addition, thermal management system malfunction was tested, and evidence was found that the polymer cold plates prevented TRP to adjacent cells. In conclusion, a combined thermal management and safety system made of polymer mini-channel cold plates provides necessary TR-related safety aspects in lithium battery systems and should be further investigated.

Abstract Columnar silicon (col‐Si) is a great candidate as anode material to achieve volumetric energy density, outperforming state‐of‐the‐art lithium‐ion batteries. The utilization of col‐Si in industrial scale is mainly restricted by poor cyclic life originating from immense volumetric expansion of Si, resulting in mechanical failure of the electrode. Understanding the mechanic and breathing behavior of col‐Si films coupled with copper current collectors (Cu‐CC) is therefore crucial to mitigate the above‐mentioned issues. In this study, structure‐mechanical changes of col‐Si anodes, which are induced by stress evolution upon (de‐)lithiation of Si, are investigated via operando electrochemical dilatometry and in situ thickness monitoring on material and stack level depending on Cu‐CC thickness (10 and 18 µm) and state‐of‐charge/balancing factor (SoC / N/P ratio). Employing moderately thick Cu‐CC (18 µm) prohibits electrode deformation significantly, achieving energy densities of 1101 and 873 Wh L−1 in multilayered‐pouch cells for N/P ratios of 1.1 and 2.0, respectively. The volume uptake that takes place after the first cycle can strongly be reduced from ∆Vcell stack: 55% to 25% by adapting N/P: 2.0 instead of 1.1. Even after volumetric growth (lithiated state), energy densities around 700 Wh L−1 are still achievable, confirming the feasibility of the col‐Si approach.

The dynamic response of lithium-ion cells under mechanical loading is known to feature significant strain-rate effects. Opposite trends in failure strength have been observed between elliptic cells (with hard shell casing) versus pouch cells, when cells were subjected to high-speed loads. This paper elucidates the reason for the observed effects by comparing dynamic data from tests on lithium-ion cells in different configurations. It reports on new dynamic tests on cells with different form factors, thicknesses, and casings. The two basic types of cells investigated were pouch cells and elliptical cells, with and without liquid electrolyte. Additionally, the elliptical cells were tested with a hard aluminum housing and with a soft pouch covering. All the cells have been loaded by a hemispherical punch with velocities between 0.01 mm/s and 5000 mm/s. Intrusion force, depth, and velocity, as well as cell voltage were measured with high time-resolution during the experiments. A comparison of the data from different configurations allows to discriminate the effects of electrolyte, thickness, and casing on the dynamic response of the cells. One main finding is that the presence of the electrolyte has the most significant effect on the overall relative strain-rate behavior. Thickness and casing do add simple scaling factors. These findings are of great importance for battery pack design in electric vehicles.

Mechanical simulation models have become crucial for understanding Li-ion battery failure and degradation mechanisms. However, existing safety assessment models lack the implementation of SOC-dependent thickness variations referred to as reversible swelling. Reversible swelling affects the applied preload force on a constrained pouch cell, potentially impacting its safety. To investigate this, a finite element RVE model was developed in LS-Dyna. Two swelling models, simplified homogenous expansion (HE) and locally resolved expansion (LE), were implemented along with a reference basis model (BM) without expansion. Six different stress- or strain-based short circuit criteria were calibrated with abuse test simulations at different SOCs and preload forces. Short circuit prognosis improved on average by 0.8% and 0.7% for the LE and HE model compared to the BM, with minimum principal stress being the most suitable criterion. The LE model exhibited a softer mechanical response than the HE model or BM, accounting for the pouch cell surface unevenness at small indentations. This study demonstrated the feasibility and usefulness of implementing an expansion model in a commercial FE solver for improved short circuit predictions. An expansion model is crucial for simulating aged battery cells with significant geometry changes strongly affecting the preload force of a constrained battery cell.

Abstract The interface structure of the electrode is closely related to the electrochemical performance of lithium‐metal batteries (LMBs). In particular, a high‐quality solid electrode interface (SEI) and uniform, dense lithium plating/stripping processes play a key role in achieving stable LMBs. Herein, a LiF‐rich SEI and a uniform and dense plating/stripping process of the electrolyte by reducing the electrolyte concentration without changing the solvation structure, thereby avoiding the high cost and poor wetting properties of high‐concentration electrolytes are achieved. The ultra‐low concentration electrolyte with an unchanged Li+ solvation structure can restrain the inhomogeneous diffusion flux of Li+, thereby achieving more uniform lithium deposition and stripping processes while maintaining a LiF‐rich SEI. The LiIICu battery with this electrolyte exhibits enhanced cycling stability for 1000 cycles with a coulombic efficiency of 99% at 1 mA cm–2 and 1 mAh cm–2. For the LiIILiFePO4 pouch cell, the capacity retention values at 0.5 and 1 C are 98.6% and 91.4%, respectively. This study offers a new perspective for the commercial application of low‐cost electrolytes with ultra‐low concentrations and high concentration effects.

Lithium-ion battery cells exhibit a complex and nonlinear coupling of thermal, electrochemical, and mechanical behavior. In order to increase insight into these processes, we report the development of a pseudo-three-dimensional (P3D) thermo-electro-mechanical model of a commercial lithium-ion pouch cell with graphite negative electrode and lithium nickel cobalt aluminum oxide/lithium cobalt oxide blend positive electrode. Nonlinear molar volumes of the active materials as function of lithium stoichiometry are taken from literature and implemented into the open-source software Cantera for convenient coupling to battery simulation codes. The model is parameterized and validated using electrical, thermal and thickness measurements over a wide range of C-rates from 0.05 C to 10 C. The combined experimental and simulated analyses show that thickness change during cycling is dominated by intercalation-induced swelling of graphite, while swelling of the two blend components partially cancel each other. At C-rates above 2 C, electrochemistry-induced temperature increase significantly contributes to cell swelling due to thermal expansion. The thickness changes are nonlinearly distributed over the thickness of the electrode pair due to gradients in the local lithiation, which may accelerate local degradation. Remaining discrepancies between simulation and experiment at high C-rates might be attributed to lithium plating, which is not considered in the model at present.

The technology of large surface thermal management of pouch cells was studied and discussed by means of simulation. With thermal management, two cells are managed by a single cold plate. First, the pressure drop of the cold plate was simulated and the velocity distribution of the flow field was observed. The cooling performance of the cold plate to the cell was then studied, and the low-temperature heating ability of the cold plate to the cell was analyzed. Through analysis, it can be concluded that large surface thermal management technology can effectively and quickly control the temperature rise of the cell when the cell is charging and discharging and the temperature difference is less than 5 °C. Finally, a control strategy for low-temperature heating of the cell by the cold plate was proposed.

Lithium-based batteries have the potential to undergo thermal runaway (TR), during which mixtures of gases are released. The purpose of this study was to assess the explosibility of the gaseous emission from LIBs of an NMC-based cathode during thermal runaway. In the current project, a series of pouch lithium-based battery cells was exposed to abuse conditions (thermal) to study the total amount of gases released and the composition of the gas mixture. First, the battery cells were placed in a closed vessel, and the pressure and temperature rise inside the vessel were measured. In a second step, the composition of gases was analysed using a Fourier transform Infrared (FTIR) spectrometer. We found that the amount of released gases was up to 102 ± 4 L, with a clear dependence on the battery capacity. This study showed that the concentration of gaseous emissions such as carbon monoxide (CO), methane (CH4), ethylene (C2H4), ethane (C2H6), and hydrogen cyanide (HCN) increased with higher cell capacity. Of the five studied flammable gases, the maximum concentrations of carbon monoxide (16.85 vol%), methane (7.6 vol%), and ethylene (7.86 vol%) were identified to be within their explosible range. Applying Le Chatelier’s law, a calculated lower explosion limit (LEL) of 7% in volume fraction was obtained for the gas mixture. The upper explosion limit (UEL) of the gas mixture was also found to be 31% in volume. A filter comprising pyrobubbles was used for the removal of the studied gas components released during the thermal abuse. The investigation revealed that the pyrobubbles filter was highly effect in the removal of HCN (up to 94% removal) and CO2 (up to 100% removal). Herein, we report the dependency of the method of thermal runaway trigger on the measured maximum temperature.

This paper presents an approach for the design and derivation for establishing a digital product twin for battery cells. A digital product twin is a virtual replica of a physical battery cell and can be used to predict and optimize quality properties and performance in real-time. The study focuses on pouch cell manufacturing and aims to map the large amount and variety of process information down to purchased parts and interim products. The approach for this study was to collect and analyze data from the physical production process and use this information to structure a digital battery product twin based on its product architecture. The main findings of this study indicate that a digital product twin can be effectively structured and implemented in a digital interface based on its product architecture in combination with data from the physical production process. The results of this study show the potential of digital product twins, in which statements about material, design, and behavior can be made using real information from production. Further research will focus on the practical application and implementation of digital product twins in a battery cell pilot production.

Lithium-sulfur batteries (LSBs) are among the most promising next generation battery technologies. First prototype cells show higher specific energies than conventional Li-ion batteries (LIBs) and the active material is cost-effective and ubiquitously abundant. However, Li-S batteries still suffer from several limitations, mainly the cycle life, inflation of cells, and also the lack of a component production value chain. As this battery system is based on a complex conversion mechanism, the electrolyte plays a key role, not only for specific energy, but also for rate capability, cycle stability and costs. Herein, we report on electrolytes based on glyoxylic-acetal based solvents, Tetraethoxyglyoxal (TEG) and Tetramethoxyglyoxal (TMG). These solvents have been examined before for supercapacitors and LIBs, but never for LSBs, although they exhibit some beneficial properties, and the production value chain has already been well established as they are precursors for several chemicals. A specially adapted electrolyte composition is established by adjusting solvent ratio and LiTFSI concentration in a TXG:DOL solvent blend. The obtained electrolytes show long cycle life as well as high coulombic efficiencies without the use of LiNO3, a component leading normally to cell inflation and safety issues. In addition, a successful evaluation in a multilayer Li-S-pouch cell was performed. The electrolytes were thoroughly characterized, and their sulfur conversion mechanism is discussed.

Lithium-ion capacitors (LICs) show promise to help lithium-ion batteries (LIBs) and electrical double layer capacitors (EDLCs) in giving response to those applications that require an energy storage solution. However, pre-lithiation is a major challenge that needs to be tackled in order to develop efficient and long-lasting LIBs and LICs. In this work, we report for the first time the scale-up and utilization of sacrificial salts (dilithium squarate, Li _2 C _4 O _4 ) as a pre-lithiation strategy in a LIC prototype fabricated in a pilot line. The synthesis of the sacrificial salt is scaled-up to produce 1 kg and is later incorporated in the positive electrode during the slurry formulation. After in-depth process optimization, 12 meter of a double side electrode are fabricated, achieving a high mass loading of 5.5 mg cm ^−2 for the HC negative electrode, and 14 mg cm ^−2 for the positive electrode accounting both the activated carbon and the dilithium squarate. On account of the satisfactory mechanical and electrochemical behaviour of the electrodes, multilayer pouch cell LIC prototypes are fabricated reaching 80 F each. Pre-lithiation is completed during the first ten cycles and after the required gas exhaustion, electrochemical performance of prototypes is also satisfactory. Moreover, fabricated pouch cells overcome a float test of 1600 h at 50 °C showing a capacitance retention of 84.3%. These results give clear evidence for the potential use of this strategy in real products and can foster research in the field to promote pre-lithiation by means of sacrificial salts as the final solution to the pre-lithiation step, both for LIBs and LICs.

In this study, 19 experiments were conducted with 25 pouch cells of NMC cathode to investigate thermal runaway and the release of gases from lithium-ion batteries (LIBs). Single cells, double cells, and a four-cell battery stack were forced to undergo thermal runaway inside an air-tight reactor vessel with a volume of 100 dm3. The study involved two series of tests with two types of ignition sources. In the Series 1 tests, a heating plug was used to initiate thermal runaway in LIBs in the ranges of 80–89% and 90–100% SOC. In the Series 2 tests, a heating plate was used to trigger thermal runaway in LIBs in the ranges of 30–50%, 80–89%, and 90–100% SOC. Thermal runaway started at an onset temperature of 344 ± 5 K and 345 K for the Series 1 tests and from 393 ± 36 K to 487 ± 10 K for the Series 2 tests. Peak reaction temperatures ranged between 642 K and 1184 K, while the maximum pressures observed were between 1.2 bar and 7.28 bar. Thermal runaway induced explosion of the cells and lead to a rate of temperature increase greater than 10 K/s. The amounts of gases released from the LIBs were calculated from pressures and temperatures measured in the reactor. Then, the gas composition was analyzed using a Fourier transform infrared (FTIR) spectrometer. The highest gaseous production was achieved at a range of 90–100% SOC and higher battery capacities 72 L, 1.8 L/Ah (Series 1, battery stack) and 103 L, 3.2 L/Ah (Series 2, 32 Ah cell)). Among the gases analyzed, the concentration of gaseous emissions such as C2H4, CH4, and C2H6 increased at a higher cell capacity in both series of tests. The study results revealed characteristic variations of thermal behavior with respect to the type of ignition source used.

To assist in light weighting of electric vehicles by improving the volumetric and gravimetric energy density and the structural performance of the battery pack, a modelling methodology based on a macro finite element model of a pouch cell has been developed. This model treats the core cell structure as a homogeneous orthotropic honeycomb block with the pouch material being defined as an orthotropic fabric with compressive stress elimination. The model considers five compression and bending load cases simultaneously and allows a level of element discretisation that is computationally efficient and appropriate for inclusion in full vehicle and sub-system simulations. The methodology is scalable in that it can be applied to a range of chemistries, external geometries and internal cell constructions. When considering stacks of cells, the model is predictive for both lateral compression and three-point bend, but further work is required to improve the confined compression response.

Strain rate sensitivity has been widely recognized as a significant feature of the dynamic mechanical properties of lithium-ion cells, which are important for their accurate representation in automotive crash simulations. This research sought to improve the precision with which dynamic mechanical properties can be determined from drop tower impact testing through the use of a diaphragm to minimize transient shock loads and to constrain off-axis motion of the indenter, specialized impact absorbers to reduce noise, and observation of displacement with a high speed camera. Inert pouch cells showed strain rate sensitivity in an increased stiffness during impact tests that was consistent with the poromechanical interaction of the porous structure of the jellyroll with the liquid electrolyte. The impact behaviour of the inert pouch cells was similar to that of an Expanded Polypropylene foam (EPP), with the exception that the inert pouch cells did not show hysteretic recovery under the weight of the indenter. This suggests that the dynamic mechanical behaviour of the inert pouch cells is analogous to a highly damped foam.

This study includes analysis of encapsulation materials from lithium-ion pouch cells and water vapour transmission rate (WVTR) measurements. WVTR measurements are performed on both fresh and environmentally stressed lithium-ion pouch cells. Capacity measurements are performed on both the fresh and the environmentally stressed battery cells to identify possible influences on electrochemical performance. Preparation of the battery cells prior to WVTR measurements includes opening of battery cells and extraction of electrode material, followed by resealing the encapsulations and adhesively mounting of gas couplings. A model describing the water diffusion through the thermal welds of the encapsulation are set up based on material analysis of the encapsulation material. Two WVTR equipments with different type of detectors are evaluated in this study. The results from the WVTR measurements show how important it is to perform this type of studies in dry environment and apply a rigorous precondition sequence before testing. Results from modelling confirm that the WVTR method has potential to be used for measurements of water diffusion into lithium-ion pouch cells. Consequently, WVTR measurements should be possible to use as a complement or alternative method to for example Karl Fisher titration.

Electrochemical performances of a high-capacity and long life β-α core-shell structured Ni0.84Co0.12Al0.04(OH)2 as the positive electrode active material were tested in a pouch design and compared to those of a standard β-Ni0.91Co0.045Zn0.045(OH)2. The core-shell materials were fabricated with a continuous co-precipitation process, which created an Al-poor core and an Al-rich shell during the nucleation and particle growth stages, respectively. The Al-rich shell became α-Ni(OH)2 after electrical activation and remained intact through the cycling. Pouch cells with the high-capacity β-α core-shell positive electrode material show higher charge acceptances and discharge capacities at 0.1C, 0.2C, 0.5C, and 1C, improved self-discharge performances, and reduced internal and surface charge-transfer resistances, at both room temperature and −10 °C when compared to those with the standard positive electrode material. While the high capacity of the core-shell material can be attributed to the α phase with a multi-electron transfer capability, the improvement in high-rate capability (lower resistance) is caused by the unique surface morphology and abundant interface sites at the β-α grain boundaries. Gravimetric energy densities of pouch cells made with the high-capacity and standard positive materials are 127 and 110 Wh·kg−1, respectively. A further improvement in capacity is expected via the continued optimization of pouch design and the use of high-capacity metal hydride alloy.