Thermal conductivity characterization considering dependencies on battery states with implication for thermal modeling and management
Extreme fast charging lithium-ion batteries require aggressive thermal management. High heat generation has to be compensated with active cooling to keep the cell temperature below hazardous thresholds. The importance of thermal management is further increased for many new cell designs. Improvements in energy density often bring along weaker thermal performance. For instance, reducing the volume […]
Diagnosis of Battery Condition Using Ultrasonic Measurements
In lithium-ion batteries (LIBs), mechanical alteration of the composites can cause a safety-critical state during battery operation. These alterations can be caused by deformation, inhomogeneous straining, or lithium plating just to name a few. Besides a safety risk, such alterations can lead to a massive loss of capacity, accelerate the aging processes and vastly limit […]
Data Driven Approach for Sensorless Temperature Estimation for Lithium-Ion Cells based on Pulse Resistance Measurements
Knowing the temperature distribution within a battery pack is crucial, because of the impact of temperature on capacity loss, power degradation and safety issues. Temperature measurements are usually realized with external temperature sensors attached to a few crucial cells throughout the battery pack, leaving the majority of cells in bigger battery packs unattended. Existing methods […]
Thermal runaway initialization temperature of fresh and aged large prismatic lithium-ion cells
Driven by the field of electric vehicles, the energy density of lithium-ion cells is rapidly increasing. Therefore, safety aspects in lithium-ion battery design become even more important. In case of a single cell failure, a thermal runaway (TR) might be triggered which results in an uncontrolled heat release within the battery system. Heat might be […]
Modeling the dimension changes under external pressure of unit cell with a system level approach
Dimensional changes in the electrodes can affect the electrochemical response of the battery and generates stresses which leads to its premature failure. Thus, understanding the volume expansion of Lithium-ion cell during cycling under external pressure is essential to improve cell design and predict aging phenomena. In this work, the volume change response of a unit […]
Challenges and solutions in battery system prototyping
Within the framework of the research project „Lebenszykluskostenreduktion im elektrischen Verteilerverkehr durch individuell adaptierbaren Antriebsstrang“ (LiVe), modular battery systems for commercial vehicles are being developed at the PEM of the RWTH Aachen University. Based on the proclaimed project objective of optimizing life cycle costs, different core requirements for battery system development were defined: • Modularity […]
Float Current Analysis for fast calendar aging detection investigating 18650 NCA/ Graphite varying temperature and voltage
Converting our electricity and transportation strategy into a sustainable system, we need high-quality battery electric storage. The most popular candidate up to now is the lithium-ion bat-tery family as it provides high energy density combined with long cycle life at low costs. The lifetime is targeted e.g. for e-mobility to 10-20 years. Due to the […]
Influence of compression on the accelerated aging of lithium ion battery cells
In this contribution, the influence of external compression on lithium-ion cells with respect to cyclic aging is demonstrated. Currently, cells for EV applications are manufactured in three different designs: pouch bag, cylindrical and prismatic housings. During charge and discharge especially the anode but as well the cathode expands and contracts. Thus, the entire jelly roll […]
A comparative study of impedance based modelling of lithium-ion batteries on half and full cell level
The dynamic performance of lithium-ion cells is strongly dependent of the underlying loss processes such as contact resistances, charge transfer and ion diffusion. Electrochemical impedance spectroscopy (EIS) is a well-known characterisation method for quantifying the complex impedance of electrochemical systems such as lithium-ion cells. In combination with an equivalent circuit model, the EIS offers the […]
Analysis of isotope labeled lithium-ion battery electrolytes – tracing solvent molecule decomposition during first cycles
The instability of state-of-the-art lithium-ion battery (LIB) electrolytes against applied electrode potentials results in redox reactions at the electrode/electrolyte interfaces. Especially during the first charge and discharge cycles, the solid electrolyte interphase (SEI) is formed on the negative electrode caused by solvent molecule and conducting salt decomposition. A sufficient interphase formation in LIBs limits ongoing […]