1,721,007 research outputs found
Simulation and experiments to understand the microstructure of and transport limitations in lithium-ion battery electrodes
No full textIt is well accepted that the electrode microstructure plays a pivotal role in
determining the cell performance (e.g., energy and power density), lifetime, and
final cost of lithium-ion batteries (LIBs). In a typical lithium-ion battery electrode,
particle-particle interactions inside the electrode solid matrix (active-material
(AM), carbon-AM, carbon-binder, and AM-binder) on one hand and the pore
structure on the other hand dictate the microstructure of the electrodes. Electrode
microstructure is a strong function of the manufacturing processes including
mixing, coating, drying, and calendaring steps. This work attempts to decipher
the interplay between the electrode manufacturing processes, electrode
microstructure, and battery rate-limiting factors for the LiNixMnyCo1-x-yO2 (NMC)-
based cathodes.
First, the existing literature on the role of electrode microstructure as a central
concept linking the electrode manufacturing processes and the battery
performance is reviewed. It is shown that there is always a trade-off between the
effective ionic and electronic transport properties of the battery electrodes. This
necessitates a comprehensive understanding of the interdependencies of the
electrode structure and the manufacturing processes to optimize the final battery
performance.
Next, we introduce an approach to assess the electrode inhomogeneity based on
different electrode formulations and thicknesses using a combination of
systematic experimentation and mathematical modeling. The electrochemical
behavior of lithium-ion batteries will be studied by analyzing the experimental
rate-capability data of the cells with the aid of a macro non-homogeneous physicsbased model which is a modified version of the so-called Newman’s model. This is
possible only when the electrode microstructure is fully characterized. For this
reason, the tortuosity of the electrodes was measured using a modelexperimentation approach. The rate limitations were identified based on the longrange and short-range limitations. It is shown that the spatial distribution of the
carbon-binder domain controls the relative contribution of the short- and longrange limitations. A similar model-experimentation platform was also developed to study the
performance limitations in situations where the electrode microstructure
properties cannot be precisely measured. This introduces an efficient approach to
scrutinize the battery behavior since a thorough characterization of the battery
electrodes is not always feasible and practical. In this regard, the overall
polarization of a battery undergoing constant-current charge and discharge cycles
was divided into the particle-level, short-range, and long-range polarization
categories. This classification is meaningful since each of these polarization groups
is influenced distinctly by the material modification (e.g., functionalization) and
components’ (e.g., electrode thickness) design strategies. In this regard, the
concept of polarographic map was introduced to correlate the share of different
polarization groups in the rate limitation of NMC porous electrodes.
Lastly, a general methodology to evaluate the advanced porous electrodes was
discussed. Here, surface-modified active material particles were used to prepare
a series of advanced porous electrodes with improved electronic and ionic
conductivities. The electrochemical performance of these electrodes was
evaluated using the insights gathered from the model-based studies of the earlier
chapters. It was shown that our model-based methodology can simplify the
screening and evaluation of the advanced novel porous electrodes without
sacrificing accuracy
Simulation and experiments to understand the microstructure of and transport limitations in lithium-ion battery electrodes
No full textIt is well accepted that the electrode microstructure plays a pivotal role in
determining the cell performance (e.g., energy and power density), lifetime, and
final cost of lithium-ion batteries (LIBs). In a typical lithium-ion battery electrode,
particle-particle interactions inside the electrode solid matrix (active-material
(AM), carbon-AM, carbon-binder, and AM-binder) on one hand and the pore
structure on the other hand dictate the microstructure of the electrodes. Electrode
microstructure is a strong function of the manufacturing processes including
mixing, coating, drying, and calendaring steps. This work attempts to decipher
the interplay between the electrode manufacturing processes, electrode
microstructure, and battery rate-limiting factors for the LiNixMnyCo1-x-yO2 (NMC)-
based cathodes.
First, the existing literature on the role of electrode microstructure as a central
concept linking the electrode manufacturing processes and the battery
performance is reviewed. It is shown that there is always a trade-off between the
effective ionic and electronic transport properties of the battery electrodes. This
necessitates a comprehensive understanding of the interdependencies of the
electrode structure and the manufacturing processes to optimize the final battery
performance.
Next, we introduce an approach to assess the electrode inhomogeneity based on
different electrode formulations and thicknesses using a combination of
systematic experimentation and mathematical modeling. The electrochemical
behavior of lithium-ion batteries will be studied by analyzing the experimental
rate-capability data of the cells with the aid of a macro non-homogeneous physicsbased model which is a modified version of the so-called Newman’s model. This is
possible only when the electrode microstructure is fully characterized. For this
reason, the tortuosity of the electrodes was measured using a modelexperimentation approach. The rate limitations were identified based on the longrange and short-range limitations. It is shown that the spatial distribution of the
carbon-binder domain controls the relative contribution of the short- and longrange limitations. A similar model-experimentation platform was also developed to study the
performance limitations in situations where the electrode microstructure
properties cannot be precisely measured. This introduces an efficient approach to
scrutinize the battery behavior since a thorough characterization of the battery
electrodes is not always feasible and practical. In this regard, the overall
polarization of a battery undergoing constant-current charge and discharge cycles
was divided into the particle-level, short-range, and long-range polarization
categories. This classification is meaningful since each of these polarization groups
is influenced distinctly by the material modification (e.g., functionalization) and
components’ (e.g., electrode thickness) design strategies. In this regard, the
concept of polarographic map was introduced to correlate the share of different
polarization groups in the rate limitation of NMC porous electrodes.
Lastly, a general methodology to evaluate the advanced porous electrodes was
discussed. Here, surface-modified active material particles were used to prepare
a series of advanced porous electrodes with improved electronic and ionic
conductivities. The electrochemical performance of these electrodes was
evaluated using the insights gathered from the model-based studies of the earlier
chapters. It was shown that our model-based methodology can simplify the
screening and evaluation of the advanced novel porous electrodes without
sacrificing accuracy
Sliding mode observer with adaptive switching gain for estimating state of charge and internal temperature of a commercial Li-ion pouch cell
No full textAccurate estimation of the state of charge (SOC) and internal temperature is the essence of the battery management systems for lithium-ion batteries (LIBs). In this research, an improved sliding mode observer (SMO) is presented and evaluated for the estimation of SOC and internal temperature of LIBs by adapting the switching gain. The observer is meticulously designed, parametrized, and validated by combining modeling and experimentation on a commercial 64 Ah LIB pouch cell. The battery behavior is emulated by a coupled equivalent circuit model (CECM) composed of a dual-polarization and a novel thermal model. The proposed observer is showcased to estimate the SOC with an average error of <2 % even in the presence of a significant model mismatch. The results provide deep insight into the development process of the efficient and robust SMO observers for estimating the internal states of LIBs.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Current Direct project under grant agreement No.963603
Morphological peculiarities of the lithium electrode from the perspective of the Marcus-Hush-Chidsey model
Full text linkThis work was supported by the European Union?s Horizon 2020 Research and Innovation Program for the Solidify Project (875557)
Experimental Investigation of a 64 Ah Lithium-Ion Pouch Cell
No full textThis study presents a meticulous investigation and characterization of a 64 Ah commercial lithium-ion pouch cell. Notably, an exhaustive analysis of the cell's open-circuit voltage and kinetics attributes is conducted, with particular emphasis on the temperature-dependent dynamics. Subsequently, a teardown experiment is performed, offering an incisive insight into the macro-geometrical properties underpinning the cell's architecture. Further details about the microstructural features and formulation inherent to the cathode and anode are revealed after image processing of the electrodes' cross sections. The details of cell balancing and cycling window of the electrodes in the pouch cell are determined and discussed based on the open-circuit-voltage measurements of the individual electrodes and a simple optimization algorithm. The methodologies presented in this work are insightful on the characterization and model parametrization of the high-capacity commercial lithium-ion cells.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Current Direct project under grant agreement No. 963603
Experimental Investigation of a 64 Ah Lithium-Ion Pouch Cell
No full textThis study presents a meticulous investigation and characterization of a 64 Ah commercial lithium-ion pouch cell. Notably, an exhaustive analysis of the cell's open-circuit voltage and kinetics attributes is conducted, with particular emphasis on the temperature-dependent dynamics. Subsequently, a teardown experiment is performed, offering an incisive insight into the macro-geometrical properties underpinning the cell's architecture. Further details about the microstructural features and formulation inherent to the cathode and anode are revealed after image processing of the electrodes' cross sections. The details of cell balancing and cycling window of the electrodes in the pouch cell are determined and discussed based on the open-circuit-voltage measurements of the individual electrodes and a simple optimization algorithm. The methodologies presented in this work are insightful on the characterization and model parametrization of the high-capacity commercial lithium-ion cells.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Current Direct project under grant agreement No. 963603
Screening of biomass residue streams for their applicability as feedstocks for activated carbon production and their compliance as electrode material
No full textCurrently, activated carbon production still relies heavily on unsustainable feedstocks, e.g., coal or fresh wood. To be able to phase out these practices, biomass residue streams offer a valid alternative, both from an economic and ecological perspective. Therefore, this research screens different promising biomass streams for their potential to be converted into top-tier activated carbon. These should preferably have a well-developed porosity and high nitrogen content to maximize their energy storage capacity and potential applicability as electrode material in supercapacitors.
Seven different types of biomass were selected in this study based on their physicochemical characteristics (e.g., lignocellulosic composition and nitrogen content): Common ivy trimmings (CI), brewer’s spent grain (BSG), Macadamia nut shells (MNS), chicken feathers (CF), coffee husks (CH) and the microalgae species Spirulina sp. (SP) and Chlorella vulgaris (CV). The biomass streams were transformed into biochars and activated carbons using a home-built stainless steel screw reactor [1,2]. Activated carbon was produced in a two step-process comprising a carbonization step at 700 °C in an inert atmosphere, followed by a physical activation step using CO2 at 800 °C. Biomass, biochars, and activated carbon were characterized for their ultimate and proximate analysis, biochemical composition, and elemental composition via inductively coupled plasma–atomic emission spectroscopy. Their surface functional groups were determined via FT-IR. Lastly, the porosity of the resulting activated carbons was measured via nitrogen physisorption experiments. The most promising activated carbons were incorporated in coin cell supercapacitors.
The results demonstrate the significant impact of the biomass’s mineral composition on creating highly porous activated carbon structures. Furthermore, the overall activated carbon yields decreased for the samples with large ash fractions due to a relative increase in carbon burn-off. In terms of creating nitrogen-rich activated carbons, CF proved best with a resulting nitrogen content of 8.2%, in contrast with MNS, which exhibited the lowest percentage (0.54 %). However, in terms of porosity, this sample (MNS) outperformed the other investigated biomass streams with a BET specific surface area of 693.7 m2/g. A correlation between the activated carbon’s porosity and their specific capacitance could be made when verifying the electrode material performance. Thus, the MNS-derived activated carbon performed best of the screened biomass streams with a specific capacitance of 53 F/g.
In conclusion, an investigation on the screening of different biomass residue streams was performed. It became clear that the low-ash content, lignocellulosic biomass MNS performed best compared to the other tested biomass streams. Future research should focus on combining different biomass streams to produce a highly porous nitrogen-rich biomass stream that would be perfectly suitable as electrode material
Interrelationships among Adjustable Design Parameters and Rate Performance of Porous Electrodes in Lithium‐Ion Batteries
No full textThe authors are grateful for the financial support to FWO-Vlaanderen (SBO XL-Lion, S005017N)
Bridging the microstructural evolutions from slurry to porous electrode of a lithium-ion battery
No full textIn lithium-ion batteries, the lithium-insertion particles that are responsible for the storage of charge are accommodated inside the porous electrodes. Although the architecture of a porous electrode is known to have a significant impact on the battery performance, there is still room to increase our knowledge about the quantitative links between electrode preparation steps and the resulting microstructural details. Here, a combination of the experimentation and physics-based modeling is employed to unravel the configurational translations of the particle aggregates from inside the slurry to the LiNi0.6Mn0.2Co0.2O2 porous electrodes. The solid-to-solvent ratio of the slurry is identified as a key parameter influencing the fractal dimension of the carbon-binder domain, drying-induced redistribution of the particles, and the compressibility behavior of the electrodes during the calendering step. The fundamental formalism introduced here paves the road for the development of optimal electrode architectures for lithium-ion cells by guiding the design of processing steps including slurry formulation and calendering. The porous electrodes are the crucial components of the modern electrochemical devices including lithium-ion batteries. The detailed configuration of the lithium-insertion, carbon black, and PVDF binder particles in a typical electrode of a lithium-ion cell has a significant impact on its energy and power density. A thinner electrode is desired to decrease the battery volume particularly for portable electronics and mobility applications. The thirst for longer discharge times, on the other hand, necessitates a higher loading of the Li-insertion particles inside the electrodes [1, 2]. A simultaneous fulfilling of these two wishes in a single design is a big challenge with a scope beyond the intrinsic charge-storage and transport properties of the individual components of the electrode. One needs to optimize the ionic and electronic connectivity of the Li-insertion particles in-and through-plane of the space confined between the current collector and separator [3-5]. A common practice is to decrease the thickness of the electrode under compression during the calendering step to optimize the effective electronic and ionic conductivity of the electrode. This is not a trivial task, however, considering the complexity and interplay among the processing steps involved in the preparation of a porous electrode, namely slurry formulation, mixing, coating, drying, and calendering (Fig. 1a-d). Our current quantitative and in-depth understanding of the interrelationships among these steps in determining the final microstructure of a porous electrode is ver
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