| 1. |
- Svens, Pontus, 1970-, et al.
(author)
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Evaluating Performance and Cycle Life Improvements in the Latest Generations of Prismatic Lithium-Ion Batteries
- 2022
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In: IEEE TRANSACTIONS ON TRANSPORTATION ELECTRIFICATION. - : Institute of Electrical and Electronics Engineers (IEEE). - 2332-7782. ; 8:3, s. 3696-3706
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Journal article (peer-reviewed)abstract
- During the last decade, the market interest for electrified vehicles has increased considerably alongside global climate initiatives. This has coincided with vast improvements in automotive-grade, lithium-ion battery performance. This has increased the range of battery electric vehicles and plug-in hybrids, but lifetime remains a challenge. Aging during fast charging is especially difficult to understand due to its nonlinear dependence on charge rate, state-of-charge, and temperature. We present results from fast charging of several energy-optimized, prismatic lithium-ion battery cell generations with a nickel manganese cobalt (NMC)/graphite chemistry through comparison of capacity retention, resistance, and dQ/dV analysis. Changes in cell design have increased energy density by almost 50% over six years of cell development and acceptable cycle life can be expected, even under fast charging, when restricting the usage of the available capacity. Even though this approach reduces the useable energy density of a battery system, this tradeoff could still be acceptable for vehicle applications where conventional overnight charging is not possible. The tested cell format has been used for a decade in electrified vehicles. The ongoing development and improvement of this cell format by several cell manufacturers suggests that it will continue to be a good choice for future vehicles.
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| 2. |
- Mikheenkova, Anastasiia, et al.
(author)
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Ageing of High Energy Density Automotive Li-Ion Batteries : The Effect of Temperature and State-of-Charge
- 2023
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
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Journal article (peer-reviewed)abstract
- Lithium ion batteries (LIB) have become a cornerstone of the shift to electric transportation. In an attempt to decrease the production load and prolong battery life, understanding different degradation mechanisms in state-of-the-art LIBs is essential. Here, we analyze how operational temperature and state-of-charge (SoC) range in cycling influence the ageing of automotive grade 21700 batteries, extracted from a Tesla 3 long Range 2018 battery pack with positive electrode containing LiNixCoyAlzO2 (NCA) and negative electrode containing SiOx-C. In the given study we use a combination of electrochemical and material analysis to understand degradation sources in the cell. Herein we show that loss of lithium inventory is the main degradation mode in the cells, with loss of material on the negative electrode as there is a significant contributor when cycled in the low SoC range. Degradation of NCA dominates at elevated temperatures with combination of cycling to high SoC (beyond 50%).
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| 3. |
- Shames, Iman, et al.
(author)
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Doppler Shift Target Localization
- 2013
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In: IEEE Transactions on Aerospace and Electronic Systems. - : IEEE Press. - 0018-9251 .- 1557-9603. ; 49:1, s. 266-276
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Journal article (peer-reviewed)abstract
- This paper outlines the problem of doppler-based target position and velocity estimation using a sensor network. The minimum number of doppler shift measurements at distinct generic sensor positions to have a finite number of solutions, and later, a unique solution for the unknown target position and velocity is stated analytically. Furthermore, we study the same problem where not only doppler shift measurements are collected, but also other types of measurements are available, e.g. bearing or distance to the target from each of the sensors. Later, we study the Cramer-Rao inequality associated with the doppler-shift measurements to a target in a sensor network, and use the Cramer-Rao bound to illustrate some results on optimal placements of the sensors when the goal is to estimate the velocity of the target. Some simulation results are presented in the end.
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| 4. |
- Smith, Alexander J., et al.
(author)
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Localized lithium plating under mild cycling conditions in high-energy lithium-ion batteries
- 2023
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In: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 573
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Journal article (peer-reviewed)abstract
- Conditions such as the temperature and pressure experienced by lithium-ion battery components are dependent on cell geometry and can vary widely within a large cell. The resulting uneven degradation is challenging to study at the full cell level but can be revealed upon disassembly and post mortem analysis. In this work, we report localized lithium plating in automotive-grade, prismatic lithium-ion cells, also under cycling conditions generally considered to be mild (e.g., 5–65 %SOC, 23 °C, 0.5C cycle rate). Dead lithium content is quantified using 7Li nuclear magnetic resonance spectroscopy in both electrode and separator samples, corresponding to substantial capacity fade (26–46%) of the full cells. Severe lithium plating is typically initiated in regions near the positive tab, in which both the separators and negative electrodes are ultimately deactivated. High pressure arises during cycling, and we propose a deactivation mechanism based on high local stress due to electrode expansion and external constraint. Further, we develop a model to demonstrate that component deactivation can result in lithium plating even under mild cycling conditions. Notably, components harvested from regions with no detected lithium plating maintained adequate electrochemical performance.
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| 5. |
- Biendicho, Jordi Jacas, et al.
(author)
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In situ investigation of commercial Ni(OH)(2) and LaNi5-based electrodes by neutron powder diffraction
- 2015
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In: Journal of Materials Research. - : Springer Science and Business Media LLC. - 0884-2914 .- 2044-5326. ; 30:3, s. 407-416
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Journal article (peer-reviewed)abstract
- Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available beta-Ni(OH)(2) and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the beta-Ni(OH)(2) electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to similar to 100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi(3.6)Al(0.4)Mn(0.3)Co(0.7), where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride gamma phase first and then to the beta phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.
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| 6. |
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| 7. |
- Blösch, Günter, et al.
(author)
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Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
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In: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
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Journal article (peer-reviewed)abstract
- This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
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| 8. |
- Churakova, Ekaterina, et al.
(author)
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Accurate analysis of residual lactose in low-lactose milk: Comparing a variety of analytical techniques
- 2019
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In: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 96, s. 126-131
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Journal article (peer-reviewed)abstract
- To receive the designation “lactose-free”, milk should contain <0.01% (w/w) lactose. As the analysis of such low levels of lactose is often hampered by other saccharides present or formed during milk processing, methods are required that are highly sensitive, accurate and precise. Currently, there is no international standard analysis method for the determination of lactose in low- or lactose-free milk, despite such a need from the dairy industry. We validated the analysis of residual lactose in lactase-treated UHT milk using HPAEC-PAD on a CarboPac PA100 column and compared it with a variety of commonly used analytical techniques for measuring lactose, including HPLC-RI, NMR, enzymatic kits, cryoscopy, and lactose biosensors. The results show that only one analytical technique, namely the Biomilk300, an amperometric biosensor, has performance comparable with analysis by HPAEC-PAD, which remains one of the most accurate, precise and sensitive methods to assess low levels of lactose in milk.
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| 9. |
- Lee-Smith, Matthew L., et al.
(author)
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Data as a material for design : alternative narratives, divergent pathways, and future directions
- 2023
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In: CHI EA '23. - : ACM Digital Library. - 9781450394222
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Conference paper (peer-reviewed)abstract
- This one-day workshop will bring together a diverse group of practitioners and researchers within the CHI community to discuss and explore data's increasing use as a material for design. This workshop encourages the submission of design exemplars, i.e., physical or digital works (in progress), design processes, or provocative or controversial pieces on the topic of data as a design material. If we are to continue to explore what data means as a design material and how we will continue to co-exist with them in our everyday lives through new and exciting ways and means, we must develop new strategies, tactics, tools, and outcomes. By bringing together products, processes, and provocations, this workshop will nurture and extend the continuation of research inquiring into data as a design material in its many forms. Our workshop will be conducted through physical and digital activities before, during, and after the onsite event at CHI 2023.
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| 10. |
- Matthaiou, Michail, 1981, et al.
(author)
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On the condition number distribution of complex Wishart matrices
- 2010
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In: IEEE Transactions on Communications. - 1558-0857. ; 58:6, s. 1705-1717
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Journal article (peer-reviewed)abstract
- This paper investigates the distribution of the condition number of complex Wishart matrices. Two closely related measures are considered: the standard condition number (SCN) and the Demmel condition number (DCN), both of which have important applications in the context of multiple-input multiple-output (MIMO) communication systems, as well as in various branches of mathematics. We first present a novel generic framework for the SCN distribution which accounts for both central and non-central Wishart matrices of arbitrary dimension. This result is a simple unified expression which involves only a single scalar integral, and therefore allows for fast and efficient computation. For the case of dual Wishart matrices, we derive new exact polynomial expressions for both the SCN and DCN distributions. We also formulate a new closed-form expression for the tail SCN distribution which applies for correlated central Wishart matrices of arbitrary dimension and demonstrates an interesting connection to the maximum eigenvalue moments of Wishart matrices of smaller dimension. Based on our analytical results, we gain valuable insights into the statistical behavior of the channel conditioning for various MIMO fading scenarios, such as uncorrelated/semi-correlated Rayleigh fading and Ricean fading.
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