• Semi-empirical model describing the rate capability of insertion electrodes. • Experimental ver... more • Semi-empirical model describing the rate capability of insertion electrodes. • Experimental verification using various active materials and design parameters. • Rate capability of all investigated electrodes follows a single master curve. • Rate capability is related to the time constant of the limiting transport process. • Model-based optimization of design parameters regarding gravimetric capacity.
The targeted optimization of Li-ion batteries (LIBs) requires a fundamental understanding of the ... more The targeted optimization of Li-ion batteries (LIBs) requires a fundamental understanding of the wide variety of interdependencies between electrode design and electrochemical performance. In the present study, the effects of thickness and porosity on the electrochemical performance and Li-ion insertion kinetics of LiNi 0.6 Co 0.2 Mn 0.2 O 2-based (NCM-622) cathodes are investigated. Cathodes of different thickness and porosity are prepared and analyzed regarding their rate capability. The polarization behavior is investigated using electrochemical impedance spectroscopy. A simple mathematical model is employed to estimate the impact of Li-ion diffusion limitations in the electrolyte. The results are considered at both, the materials and the full-cell level. The design parameters are found to have distinct impact on the electrolyte, contact and charge transfer resistance as well as the Li-ion diffusion limitations in the electrolyte, significantly influencing the rate capability. The results attest an inherent tradeoff between energy and power density. The insights of this study can be used straightforward for the optimization of gravimetric and volumetric energy density of LIBs depending on the desired application.
Abstract To enable solid-state batteries with Li metal anodes, different classes of electrolytes ... more Abstract To enable solid-state batteries with Li metal anodes, different classes of electrolytes are being investigated, mainly polymers, oxides, and sulfides. To overcome individual drawbacks of the material classes, so called bilayer hybrid cells combining layers of different electrolyte materials are considered highly promising. However, the introduction of an additional interface between the two solid electrolytes raises the question of the corresponding interfacial resistance. Herein, the properties of the interface between the two promising electrolytes Al-LLZO (Li6.16Al0.28La3Zr2O12) and LPS (Li7P3S11) are investigated by comprehensive impedance analyses. A series of systematic measurements allows to deconvolute the pressure dependence of the resistances related to the LPS material and the LPS/LLZO interface. This analysis reveals a significant pressure dependence of the LPS/LLZO interfacial resistance, mainly attributed to constriction resistance. Optimization of the LPS/LLZO interface is carried out by targeted surface treatment, resulting in a dramatic decrease of the interfacial resistance to virtually zero. These mechanistic studies and optimization approaches are complemented by practically relevant cycling tests using Li-metal electrodes. The cells show excellent cycling stability and negligible degradation. These findings contribute to the fundamental understanding of solid-solid interfaces in bilayer hybrid cells, indicating that solid-state batteries with hybrid LPS/LLZO electrolytes appear highly promising.
The development of rechargeable batteries with high‐energy density is critical for future decarbo... more The development of rechargeable batteries with high‐energy density is critical for future decarbonization of transportation. Anode‐free Li‐ion batteries, using a bare current collector at the anode side without any excess of Li, provide the highest volumetric energy density (>1500 Wh L−1) among all possible cell configurations. Furthermore, elimination of the anode material coating reduces material consumption and greatly simplifies cell production, which in turn lowers costs. Although significant progress has been made recently by the application of modified current collectors, optimized cycling parameters and improved liquid electrolytes, insufficient efficiencies, and dendritic growth during lithium plating lead to poor cycle life of typically less than 100 cycles as well as safety issues. Alternatively, very recent studies have demonstrated anode‐free solid‐state batteries that combine the benefits of high energy anode‐free cell configuration and solid‐state systems with high safety, exceeding 1000 cycles. This review provides an overview of recent developments toward anode‐free solid‐state batteries and highlights the current issues and challenges in this nascent field. It is concluded that, although major challenges remain at the present, the lessons learned in the fields of liquid electrolytes and solid‐state lithium metal batteries can accelerate the development of anode‐free solid‐state batteries of practical relevance.
Abstract In this work, an effective and facile extrusion-based mixing and coating process for the... more Abstract In this work, an effective and facile extrusion-based mixing and coating process for the manufacturing of electrodes for Li-ion batteries is proposed. Following the development of appropriate pastes and basic rheological investigations, promising formulations are dispersed continuously in a twin screw extruder and directly coated on a current collector foil using the example of LiNi0.6Mn0.2Co0.2O2 as cathode material. The impact of the rotational screw speed, residence time and shear stresses are examined by complimentary materials characterization. The electrochemical performance in battery cells, the homogeneity and microstructure of electrodes manufactured by the extrusion process are compared with electrodes fabricated by an established tape-casting process. The extrusion-based fabrication route shows excellent particle dispersion and high coating quality, resulting in excellent electrochemical performance while providing numerous advantages regarding design freedom, material and processing costs as well as facile upscaling and continuous operation potentials. The work shows that the extrusion-based coating process is a highly promising alternative for the efficient production of lithium-ion batteries.
Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability ... more Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability of 4.5 V vs. Li/Li+ are presented. Thus, imidazolium-containing poly(ionic liquid) (PIL) networks were prepared by crosslinking UV-photopolymerization in an in situ approach (i.e., to allow preparation directly on the electrodes used). The crosslinks in the network improve the mechanical stability of the samples, as indicated by the free-standing nature of the materials and temperature-dependent rheology measurements. The averaged mesh size calculated from rheologoical measurements varied between 1.66 nm with 10 mol% crosslinker and 4.35 nm without crosslinker. The chemical structure of the ionic liquid (IL) monomers in the network was varied to achieve the highest possible ionic conductivity. The systematic variation in three series with a number of new IL monomers offers a direct comparison of samples obtained under comparable conditions. The ionic conductivity of generation II and III...
Abstract To increase the user acceptance and to push electric mobility towards mass suitability, ... more Abstract To increase the user acceptance and to push electric mobility towards mass suitability, the energy and power density of Li-ion batteries for electric vehicles are among the most crucial features to be improved. The two major approaches to increase the energy density are the development of improved active materials and favorable cell designs. However, the identification of an optimal cell design is a sophisticated challenge due to the large number of interdependent factors influencing the different performance parameters. In the present study, a straightforward model based on the concept of diffusion-limited C-rate is proposed to optimize the energy density of Li-ion battery cells with specified rate performance. The model is introduced and the underlying assumptions are verified by comprehensive experimental investigations. The model is used to identify optimal design parameters of anode and cathode regarding maximum volumetric and gravimetric energy for specified rate performance. A sensitivity analysis is carried out to quantify optimization potentials of cell components and their properties. The results are discussed regarding promising improvement strategies and the practical limits of Li-ion batteries.
The publisher regrets that high-resolution vector graphics were not included in the final version... more The publisher regrets that high-resolution vector graphics were not included in the final version of this article and that line breaks were inserted within the chemical formula. The publisher would like to apologise for any inconvenience caused.
The presented model approach offers a computational efficient tool to analyze the influences of g... more The presented model approach offers a computational efficient tool to analyze the influences of geometrical design details, material selection and operational conditions on the electro-thermal behavior of a full Li ion battery cell geometry. It considers typical aspects as anisotropic winding structure, electro-thermal coupling and nonlinear electrical characteristics for moderate computational costs. That becomes possible by employing elaborate model reduction strategies, taking full advantage of the flexible features offered by the COMSOL Multiphysics® code: using an homogenized 3 DOF phase composite model for electric and thermal conduction in the cell laminate, a simple empirical, experimental based, submodel for the electro-chemical characteristics and a hybrid coupled 2D-3D approach for the electrical and thermal interactions in the winding body.
International Congress on Applications of Lasers & Electro-Optics
In order to introduce competitive mass market solutions for the production in electro mobility, c... more In order to introduce competitive mass market solutions for the production in electro mobility, costs for battery cell manufacturing have to be significantly reduced. The substitution of conventional furnace processes through innovative laser processes presents a significant energy saving potential as well as a considerable reduction of the installation space for the corresponding roll-to-roll system. A laser-based drying process of water-based battery electrode films (anodes as well as cathodes) is developed which needs to fulfill the requirement of not exceeding temperatures of 240°C in the temperature-sensitive, 50-100µm thick films. By laser-drying of battery electrodes, coin cell capacities of about 355 mAh/g (equal to those of conventionally produced cells) can be achieved. By implementing a technology demonstrator in the form of a laser drying module, the scalability of the process can be shown in an in-line coating demonstrator. Using 450 W of laser power, area rates of about 50 cm2/s can be achieved while reducing the energy consumption by about 50% in comparison to conventional oven processes. Among the application fields are laser-based drying of conventional battery electrodes in mobile devices as well as solid state electrodes in thin film batteries for small and mobile applications such as smart patches, lighted labelling etc.In order to introduce competitive mass market solutions for the production in electro mobility, costs for battery cell manufacturing have to be significantly reduced. The substitution of conventional furnace processes through innovative laser processes presents a significant energy saving potential as well as a considerable reduction of the installation space for the corresponding roll-to-roll system. A laser-based drying process of water-based battery electrode films (anodes as well as cathodes) is developed which needs to fulfill the requirement of not exceeding temperatures of 240°C in the temperature-sensitive, 50-100µm thick films. By laser-drying of battery electrodes, coin cell capacities of about 355 mAh/g (equal to those of conventionally produced cells) can be achieved. By implementing a technology demonstrator in the form of a laser drying module, the scalability of the process can be shown in an in-line coating demonstrator. Using 450 W of laser power, area rates of about 50 cm2/s can be achie...
Expanding life time as well as lowering production costs of a lithium-ion cell are two important ... more Expanding life time as well as lowering production costs of a lithium-ion cell are two important subjects, which are addressed in the current research of lithium-ion batteries. One approach to reach these aims is an optimization of the electrolyte filling and formation process of the lithium-ion cells. This process steps have a major contribution to the production costs, since it requires high investments to provide a sufficient amount of formation equipment. Furthermore, since this processes can take up to 3 weeks, quite a lot of stock capacity is necessary [1]. After filling the cell with electrolyte, the formation process starts with different aging and charging steps with different durations, charging conditions (e.g. c-rate, voltage cut-off) and atmosphere conditions (e.g. pressure and temperature profiles). The aging steps during the formation process are applied to ensure a proper saturation of all the pores of the electrodes with electrolyte. This is of particular importance...
We report a new process technique for electrode manufacturing for all solid-state batteries. Poro... more We report a new process technique for electrode manufacturing for all solid-state batteries. Porous electrodes are manufactured by a tape casting process and subsequently infiltrated by a plastic crystal polymer electrolyte (PCPE). With a following isostatic lamination process, the PCPE was further integrated deeply into the porous electrode layer, forming a composite electrode. The PCPE comprises the plastic crystal succinonitrile (SN), lithium conductive salt LiTFSI and polyacrylonitrile (PAN) and exhibits suitable thermal, rheological (ƞ = 0.6 Pa s @ 80 °C 1 s−1) and electrochemical properties (σ > 10−4 S/cm @ 45 °C). We detected a lowered porosity of infiltrated and laminated electrodes through Hg porosimetry, showing a reduction from 25.6% to 2.6% (NCM infiltrated to laminated) and 32.9% to 4.0% (LTO infiltrated to laminated). Infiltration of PCPE into the electrodes was further verified by FESEM images and EDS mapping of sulfur content of the conductive salt. Cycling tests ...
• Semi-empirical model describing the rate capability of insertion electrodes. • Experimental ver... more • Semi-empirical model describing the rate capability of insertion electrodes. • Experimental verification using various active materials and design parameters. • Rate capability of all investigated electrodes follows a single master curve. • Rate capability is related to the time constant of the limiting transport process. • Model-based optimization of design parameters regarding gravimetric capacity.
The targeted optimization of Li-ion batteries (LIBs) requires a fundamental understanding of the ... more The targeted optimization of Li-ion batteries (LIBs) requires a fundamental understanding of the wide variety of interdependencies between electrode design and electrochemical performance. In the present study, the effects of thickness and porosity on the electrochemical performance and Li-ion insertion kinetics of LiNi 0.6 Co 0.2 Mn 0.2 O 2-based (NCM-622) cathodes are investigated. Cathodes of different thickness and porosity are prepared and analyzed regarding their rate capability. The polarization behavior is investigated using electrochemical impedance spectroscopy. A simple mathematical model is employed to estimate the impact of Li-ion diffusion limitations in the electrolyte. The results are considered at both, the materials and the full-cell level. The design parameters are found to have distinct impact on the electrolyte, contact and charge transfer resistance as well as the Li-ion diffusion limitations in the electrolyte, significantly influencing the rate capability. The results attest an inherent tradeoff between energy and power density. The insights of this study can be used straightforward for the optimization of gravimetric and volumetric energy density of LIBs depending on the desired application.
Abstract To enable solid-state batteries with Li metal anodes, different classes of electrolytes ... more Abstract To enable solid-state batteries with Li metal anodes, different classes of electrolytes are being investigated, mainly polymers, oxides, and sulfides. To overcome individual drawbacks of the material classes, so called bilayer hybrid cells combining layers of different electrolyte materials are considered highly promising. However, the introduction of an additional interface between the two solid electrolytes raises the question of the corresponding interfacial resistance. Herein, the properties of the interface between the two promising electrolytes Al-LLZO (Li6.16Al0.28La3Zr2O12) and LPS (Li7P3S11) are investigated by comprehensive impedance analyses. A series of systematic measurements allows to deconvolute the pressure dependence of the resistances related to the LPS material and the LPS/LLZO interface. This analysis reveals a significant pressure dependence of the LPS/LLZO interfacial resistance, mainly attributed to constriction resistance. Optimization of the LPS/LLZO interface is carried out by targeted surface treatment, resulting in a dramatic decrease of the interfacial resistance to virtually zero. These mechanistic studies and optimization approaches are complemented by practically relevant cycling tests using Li-metal electrodes. The cells show excellent cycling stability and negligible degradation. These findings contribute to the fundamental understanding of solid-solid interfaces in bilayer hybrid cells, indicating that solid-state batteries with hybrid LPS/LLZO electrolytes appear highly promising.
The development of rechargeable batteries with high‐energy density is critical for future decarbo... more The development of rechargeable batteries with high‐energy density is critical for future decarbonization of transportation. Anode‐free Li‐ion batteries, using a bare current collector at the anode side without any excess of Li, provide the highest volumetric energy density (>1500 Wh L−1) among all possible cell configurations. Furthermore, elimination of the anode material coating reduces material consumption and greatly simplifies cell production, which in turn lowers costs. Although significant progress has been made recently by the application of modified current collectors, optimized cycling parameters and improved liquid electrolytes, insufficient efficiencies, and dendritic growth during lithium plating lead to poor cycle life of typically less than 100 cycles as well as safety issues. Alternatively, very recent studies have demonstrated anode‐free solid‐state batteries that combine the benefits of high energy anode‐free cell configuration and solid‐state systems with high safety, exceeding 1000 cycles. This review provides an overview of recent developments toward anode‐free solid‐state batteries and highlights the current issues and challenges in this nascent field. It is concluded that, although major challenges remain at the present, the lessons learned in the fields of liquid electrolytes and solid‐state lithium metal batteries can accelerate the development of anode‐free solid‐state batteries of practical relevance.
Abstract In this work, an effective and facile extrusion-based mixing and coating process for the... more Abstract In this work, an effective and facile extrusion-based mixing and coating process for the manufacturing of electrodes for Li-ion batteries is proposed. Following the development of appropriate pastes and basic rheological investigations, promising formulations are dispersed continuously in a twin screw extruder and directly coated on a current collector foil using the example of LiNi0.6Mn0.2Co0.2O2 as cathode material. The impact of the rotational screw speed, residence time and shear stresses are examined by complimentary materials characterization. The electrochemical performance in battery cells, the homogeneity and microstructure of electrodes manufactured by the extrusion process are compared with electrodes fabricated by an established tape-casting process. The extrusion-based fabrication route shows excellent particle dispersion and high coating quality, resulting in excellent electrochemical performance while providing numerous advantages regarding design freedom, material and processing costs as well as facile upscaling and continuous operation potentials. The work shows that the extrusion-based coating process is a highly promising alternative for the efficient production of lithium-ion batteries.
Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability ... more Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability of 4.5 V vs. Li/Li+ are presented. Thus, imidazolium-containing poly(ionic liquid) (PIL) networks were prepared by crosslinking UV-photopolymerization in an in situ approach (i.e., to allow preparation directly on the electrodes used). The crosslinks in the network improve the mechanical stability of the samples, as indicated by the free-standing nature of the materials and temperature-dependent rheology measurements. The averaged mesh size calculated from rheologoical measurements varied between 1.66 nm with 10 mol% crosslinker and 4.35 nm without crosslinker. The chemical structure of the ionic liquid (IL) monomers in the network was varied to achieve the highest possible ionic conductivity. The systematic variation in three series with a number of new IL monomers offers a direct comparison of samples obtained under comparable conditions. The ionic conductivity of generation II and III...
Abstract To increase the user acceptance and to push electric mobility towards mass suitability, ... more Abstract To increase the user acceptance and to push electric mobility towards mass suitability, the energy and power density of Li-ion batteries for electric vehicles are among the most crucial features to be improved. The two major approaches to increase the energy density are the development of improved active materials and favorable cell designs. However, the identification of an optimal cell design is a sophisticated challenge due to the large number of interdependent factors influencing the different performance parameters. In the present study, a straightforward model based on the concept of diffusion-limited C-rate is proposed to optimize the energy density of Li-ion battery cells with specified rate performance. The model is introduced and the underlying assumptions are verified by comprehensive experimental investigations. The model is used to identify optimal design parameters of anode and cathode regarding maximum volumetric and gravimetric energy for specified rate performance. A sensitivity analysis is carried out to quantify optimization potentials of cell components and their properties. The results are discussed regarding promising improvement strategies and the practical limits of Li-ion batteries.
The publisher regrets that high-resolution vector graphics were not included in the final version... more The publisher regrets that high-resolution vector graphics were not included in the final version of this article and that line breaks were inserted within the chemical formula. The publisher would like to apologise for any inconvenience caused.
The presented model approach offers a computational efficient tool to analyze the influences of g... more The presented model approach offers a computational efficient tool to analyze the influences of geometrical design details, material selection and operational conditions on the electro-thermal behavior of a full Li ion battery cell geometry. It considers typical aspects as anisotropic winding structure, electro-thermal coupling and nonlinear electrical characteristics for moderate computational costs. That becomes possible by employing elaborate model reduction strategies, taking full advantage of the flexible features offered by the COMSOL Multiphysics® code: using an homogenized 3 DOF phase composite model for electric and thermal conduction in the cell laminate, a simple empirical, experimental based, submodel for the electro-chemical characteristics and a hybrid coupled 2D-3D approach for the electrical and thermal interactions in the winding body.
International Congress on Applications of Lasers & Electro-Optics
In order to introduce competitive mass market solutions for the production in electro mobility, c... more In order to introduce competitive mass market solutions for the production in electro mobility, costs for battery cell manufacturing have to be significantly reduced. The substitution of conventional furnace processes through innovative laser processes presents a significant energy saving potential as well as a considerable reduction of the installation space for the corresponding roll-to-roll system. A laser-based drying process of water-based battery electrode films (anodes as well as cathodes) is developed which needs to fulfill the requirement of not exceeding temperatures of 240°C in the temperature-sensitive, 50-100µm thick films. By laser-drying of battery electrodes, coin cell capacities of about 355 mAh/g (equal to those of conventionally produced cells) can be achieved. By implementing a technology demonstrator in the form of a laser drying module, the scalability of the process can be shown in an in-line coating demonstrator. Using 450 W of laser power, area rates of about 50 cm2/s can be achieved while reducing the energy consumption by about 50% in comparison to conventional oven processes. Among the application fields are laser-based drying of conventional battery electrodes in mobile devices as well as solid state electrodes in thin film batteries for small and mobile applications such as smart patches, lighted labelling etc.In order to introduce competitive mass market solutions for the production in electro mobility, costs for battery cell manufacturing have to be significantly reduced. The substitution of conventional furnace processes through innovative laser processes presents a significant energy saving potential as well as a considerable reduction of the installation space for the corresponding roll-to-roll system. A laser-based drying process of water-based battery electrode films (anodes as well as cathodes) is developed which needs to fulfill the requirement of not exceeding temperatures of 240°C in the temperature-sensitive, 50-100µm thick films. By laser-drying of battery electrodes, coin cell capacities of about 355 mAh/g (equal to those of conventionally produced cells) can be achieved. By implementing a technology demonstrator in the form of a laser drying module, the scalability of the process can be shown in an in-line coating demonstrator. Using 450 W of laser power, area rates of about 50 cm2/s can be achie...
Expanding life time as well as lowering production costs of a lithium-ion cell are two important ... more Expanding life time as well as lowering production costs of a lithium-ion cell are two important subjects, which are addressed in the current research of lithium-ion batteries. One approach to reach these aims is an optimization of the electrolyte filling and formation process of the lithium-ion cells. This process steps have a major contribution to the production costs, since it requires high investments to provide a sufficient amount of formation equipment. Furthermore, since this processes can take up to 3 weeks, quite a lot of stock capacity is necessary [1]. After filling the cell with electrolyte, the formation process starts with different aging and charging steps with different durations, charging conditions (e.g. c-rate, voltage cut-off) and atmosphere conditions (e.g. pressure and temperature profiles). The aging steps during the formation process are applied to ensure a proper saturation of all the pores of the electrodes with electrolyte. This is of particular importance...
We report a new process technique for electrode manufacturing for all solid-state batteries. Poro... more We report a new process technique for electrode manufacturing for all solid-state batteries. Porous electrodes are manufactured by a tape casting process and subsequently infiltrated by a plastic crystal polymer electrolyte (PCPE). With a following isostatic lamination process, the PCPE was further integrated deeply into the porous electrode layer, forming a composite electrode. The PCPE comprises the plastic crystal succinonitrile (SN), lithium conductive salt LiTFSI and polyacrylonitrile (PAN) and exhibits suitable thermal, rheological (ƞ = 0.6 Pa s @ 80 °C 1 s−1) and electrochemical properties (σ > 10−4 S/cm @ 45 °C). We detected a lowered porosity of infiltrated and laminated electrodes through Hg porosimetry, showing a reduction from 25.6% to 2.6% (NCM infiltrated to laminated) and 32.9% to 4.0% (LTO infiltrated to laminated). Infiltration of PCPE into the electrodes was further verified by FESEM images and EDS mapping of sulfur content of the conductive salt. Cycling tests ...
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