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Calendering is the common compaction process for lithium-ion battery electrodes and has a substantial impact on the pore structure and therefore the electrochemical performance of ...Lithium-ion battery cells. For a targeted determination of the performance-optimized pore structure, it is of decisive importance to be able to comprehensively control the compaction process. Thus, during continuous calendering of graphite anodes and lithium nickel cobalt manganese oxide (NCM) cathodes the applied line load is tracked and varied at different speeds to compact the electrode to several coating densities. The generated pore structures are measured via mercury intrusion, resulting in quite similar porosities, while the densities of graphite and NCM diverge greatly. The porosities, measured via mercury intrusion, are compared to geometrical determined data, identifying compaction resistant closed pores in the NCM. On the basis of the measured porosity reduction the compaction behavior of the line load was found to be describable by an exponential model equation. The model parameters quantify the different compaction resistances of the cathodes and anodes in converging to a maximal density, respectively minimal porosity. This substantial difference could be traced to the closer packing of the spherical and harder NCM particles. The calendering speed showed only an insignificant impact up to speeds of 5m/min.
Different discontinuously and continuously working dispersing devices were investigated to determine their influence on the structural and electrochemical properties of electrodes made from ...commercial LiNi
1/3
Co
1/3
Mn
1/3
O
2
(NCM) cathode active material. A laboratory-scale dispersing device was compared with a discontinuously working laboratory kneader and a continuously working extruder, both using 50% less solvent than the dissolver process. Rheological, mechanical, structural, conductive, imaging, and electrochemical analyses (C-rate test, long-term cycling) were carried out. The dispersing method and time were found to have a considerable impact on the structure and electrochemical performance. The continuous extrusion process resulted in good performance with more than 20% higher specific capacity at elevated C-rates compared with the discontinuous process. This can be attributed to better deagglomeration of the carbon black in the slurries, also resulting in 60% higher electrode conductivity. On top of these positive results, the changes in the drying step due to the reduced solvent use led to a 50% decrease in the time required for the constant-drying-rate period. The continuously working extrusion process was found to be most suitable for large-scale, cost-efficient, environmentally friendly production of slurries for lithium-ion battery electrodes.
Multiscale simulation approach for production systems Schönemann, Malte; Bockholt, Henrike; Thiede, Sebastian ...
International journal of advanced manufacturing technology,
06/2019, Letnik:
102, Številka:
5
Journal Article
Recenzirano
Planning support for industrial production systems aims at reducing production-related costs and environmental impacts while creating required products with a desired quality. However, the increasing ...complexity of modern products and production technology makes planning and the provision of appropriate methods and tools a challenging task. Isolated measures for improving quality, cost or eco-efficiency, often result in problem shifting causing negative effects regarding other goal criteria. For this reason, suitable methods and tools are required for the planning and evaluation of specific improvement measures and for obtaining an interdisciplinary system understanding. This paper presents an approach, which is capable of analyzing production systems considering multiple scales based on coupled simulation models. The approach enables the evaluation of interactions between product units, processes, machines, technical building services, and the building structure. The approach contains a generic framework for the simulation structure, detailed model concepts for relevant production system elements, and a definition of interfaces between models for co-simulation. A case study demonstrates an exemplary application of the simulation approach for the production of battery cells. The study shows how the simulation enables evaluating the influences of different process configurations on intermediate product characteristics as well as of different factory scenarios and seasonal effects on the energy demands. More specifically, on product and process scale, the study revealed how different process routes and process parameters in electrode production affect the characteristics of battery slurries and coated electrode foils along with production lead-times. On process chain and factory scale, the study illustrates how the energy demands of machines and building services are influenced by machine operation and outside weather conditions. Thus, the study provides insight into the capabilities of a multiscale simulation and how such simulation may be applied to evaluate different producton system configurations, operation strategies, or facility locations.
The conductive network within a lithium-ion battery electrode is mainly influenced by the process parameters chosen for the dry mixing and wet dispersing step during the production of a coatable ...electrode slurry, consisting of well-defined components. This conductive network, which results from the electrode's microstructure, plays a major role for the resulting battery cell performance, especially for high performance and power applications. Notable differences can be observed in the subsequently manufactured electrodes due to process-related modifications in the carbon black agglomerate size; mechanical, electrical, and, thus, electrochemical properties are significantly changing with the process parameters set. To allow for a direct correlation of these properties with the electrode structure, a characteristic parameter to describe the carbon black structure in electrode coatings is developed. Based on mercury intrusion measurements, the internal porosity of carbon black particles was determined as a characteristic parameter for the conductive microstructure. For a wide variety of lithium-ion battery cathode samples, the carbon black porosity can be well related to important electrode properties. This underscores the relevance of this carbon black-based microstructure parameter for a knowledge-based process and product optimization.
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•Carbon black porosity as a structural parameter for LIB is developed and proven.•Wet dispersion and dry mixing can be used to adjust the carbon black porosity.•Carbon black porosity determines C-rate performance in the form of an optimum curve.
Carbon black is an important component in lithium-ion battery electrodes since it significantly improves the electric conductivity in the coating. Dependent on the carbon black structure and the ...homogeneity of the carbon black distribution, electrical and electrochemical electrode properties vary. The presented work reveals that the carbon black structure in lithium-ion battery electrodes can precisely be governed by careful parameter variations in an upstream dry mixing process. Significant changes in important electrode properties like mechanical, structural and electrical characteristics are achieved and can be described as functions of the process parameters “mixing time” and “mixing intensity”. The integration of an intensive dry mixing process improves the coating homogeneity and creates short-range electrical contacts on the particle surfaces, leading to enhancements in cycling stability. Long-range electrical contacts can be re-established due to a subsequent calendering step, compensating rate capability losses, which can be identified for uncalendered electrodes.
Carbon black significantly improves the electric conductivity in lithium-ion battery electrodes. The presented work reveals that the carbon black structure in lithium-ion battery electrodes can precisely be governed by careful parameter variations in an upstream dry mixing process. As a result, important product properties are significantly changed. Display omitted
•Intensive dry mixing allows for solids content increase: economic benefit!•Dry dispersing of carbon black precisely governs electrode structure.•Electrode properties are presented as functions of the process parameters.•Creation of short-range electrical contacts brings advantages in cycling stability.•Subsequent calendering re-establishes long-range electrical contacts.
The individual steps in the electrode manufacturing process, e.g., conductive additives addition, mixing, and calendering, strongly affect the electrochemical and mechanical properties of the ...electrodes. LiNi1/3Co1/3Mn1/3O2 (NCM) cathode electrodes with conductive additive variations are fabricated using a reference and an intensive mixing process, and are subsequently calendered to different porosities. It is found that graphite reduces the pore size of NCM electrodes, in contrast to the carbon black that establishes additional nanoscale pores. Electrodes manufactured with reference mixing result in a porous carbon black network with good overall electric pathways, whereas those manufactured with intensive processing result in a dense carbon black network, leading to good short-range contacts, but a lack of long-range contacts. In this case, the addition of graphite as a conductive additive is identified to establish important additional long-range contacts. Due to the structural differences achieved by the compared processing routes, the calendering process can have a positive or negative impact on battery performance.
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•A concept is presented that explains the complexity of electrode manufacturing.•The concept derives how processing indirectly affects electrochemical performance.•Graphite addition enhances performance if long-range electric pathways are missing.•Calendering can disturb electric pathways, when CB network is mechanically weak.•Calendering improves performance only if electric pathways are not disturbed.
Multiscale simulation approach for production systems Schönemann, Malte; Bockholt, Henrike; Thiede, Sebastian ...
International journal of advanced manufacturing technology,
19/6, Letnik:
102, Številka:
5-8
Journal Article
Recenzirano
Planning support for industrial production systems aims at reducing production-related costs and environmental impacts while creating required products with a desired quality. However, the increasing ...complexity of modern products and production technology makes planning and the provision of appropriate methods and tools a challenging task. Isolated measures for improving quality, cost or eco-efficiency, often result in problem shifting causing negative effects regarding other goal criteria. For this reason, suitable methods and tools are required for the planning and evaluation of specific improvement measures and for obtaining an interdisciplinary system understanding. This paper presents an approach, which is capable of analyzing production systems considering multiple scales based on coupled simulation models. The approach enables the evaluation of interactions between product units, processes, machines, technical building services, and the building structure. The approach contains a generic framework for the simulation structure, detailed model concepts for relevant production system elements, and a definition of interfaces between models for co-simulation. A case study demonstrates an exemplary application of the simulation approach for the production of battery cells. The study shows how the simulation enables evaluating the influences of different process configurations on intermediate product characteristics as well as of different factory scenarios and seasonal effects on the energy demands. More specifically, on product and process scale, the study revealed how different process routes and process parameters in electrode production affect the characteristics of battery slurries and coated electrode foils along with production lead-times. On process chain and factory scale, the study illustrates how the energy demands of machines and building services are influenced by machine operation and outside weather conditions. Thus, the study provides insight into the capabilities of a multiscale simulation and how such simulation may be applied to evaluate different producton system configurations, operation strategies, or facility locations.
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