ALBERT

Description: In this paper, advanced equivalent circuit models (ECMs) were developed to model large format and high energy nickel manganese cobalt (NMC) lithium-ion 20 Ah battery cells. Different temperatures conditions, cell characterization test (Normal and Advanced Tests), ECM topologies (1st and 2nd Order Thévenin model), state of charge (SoC) estimation techniques (Coulomb counting and extended Kalman filtering) and validation profiles (dynamic discharge pulse test (DDPT) and world harmonized light vehicle profiles) have been incorporated in the analysis. A concise state-of-the-art of different lithium-ion battery models existing in the academia and industry is presented providing information about model classification and information about electrical models. Moreover, an overview of the different steps and information needed to be able to create an ECM model is provided. A comparison between begin of life (BoL) and aged (95%, 90% state of health) ECM parameters (internal resistance (Ro), polarization resistance (Rp), activation resistance (Rp2) and time constants (τ) is presented. By comparing the BoL to the aged parameters an overview of the behavior of the parameters is introduced and provides the appropriate platform for future research in electrical modeling of battery cells covering the ageing aspect. Based on the BoL parameters 1st and 2nd order models were developed for a range of temperatures (15 °C, 25 °C, 35 °C, 45 °C). The highest impact to the accuracy of the model (validation results) is the temperature condition that the model was developed. The 1st and 2nd order Thévenin models and the change from normal to advanced characterization datasets, while they affect the accuracy of the model they mostly help in dealing with high and low SoC linearity problems. The 2nd order Thévenin model with advanced characterization parameters and extended Kalman filtering SoC estimation technique is the most efficient and dynamically correct ECM model developed.

Description: The increased activity in the field of Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) have led to an increase in standardization work, performed by both world-wide organizations like the IEC or the ISO, as by regional and national bodies such as CEN, CENELEC, SAE or JEVA. The issues of these standards cover several topics: safety, performance and operational/dimension issues. This paper reports a brief overview of current standardization activities of lithium batteries based on IEC 62660-1/2 and ISO 12405-1/2. Furthermore, in this paper, a series of innovative test procedures for lithium-ion batteries are presented. Thanks to these tests, the general characteristics of a battery such as charge and discharge capabilities, power performances and life cycle can be determined. Then, a new approach for extracting the life cycle of a battery in function of depth of discharge has been developed.

Description: Lithium-based batteries are considered as the most advanced batteries technology, which can be designed for high energy or high power storage systems. However, the battery cells are never fully identical due to the fabrication process, surrounding environment factors and differences between the cells tend to grow if no measures are taken. In order to have a high performance battery system, the battery cells should be continuously balanced for maintain the variation between the cells as small as possible. Without an appropriate balancing system, the individual cell voltages will differ over time and battery system capacity will decrease quickly. These issues will limit the electric range of the electric vehicle (EV) and some cells will undergo higher stress, whereby the cycle life of these cells will be shorter. Quite a lot of cell balancing/equalization topologies have been previously proposed. These balancing topologies can be categorized into passive and active balancing. Active topologies are categorized according to the active element used for storing the energy such as capacitor and/or inductive component as well as controlling switches or converters. This paper proposes an intelligent battery management system (BMS) including a battery pack charging and discharging control with a battery pack thermal management system. The BMS user input/output interfacing. The battery balancing system is based on battery pack modularization architecture. The proposed modularized balancing system has different equalization systems that operate inside and outside the modules. Innovative single switched capacitor (SSC) control strategy is proposed to balance between the battery cells in the module (inside module balancing, IMB). Novel utilization of isolated bidirectional DC/DC converter (IBC) is proposed to balance between the modules with the aid of the EV auxiliary battery (AB). Finally an experimental step-up has been implemented for the validation of the proposed balancing system.

Description: The increased activity in the field of Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) have led to an increase in standardization work, performed by both world-wide organizations like the IEC or the ISO, as by regional and national bodies such as CEN, CENELEC, SAE or JEVA. The issues of these standards cover several topics: safety, performance and operational/dimension issues. This paper reports a brief overview of current standardization activities of lithium batteries based on IEC 62660-1/2 and ISO 12405-1/2. Furthermore, in this paper, a series of innovative test procedures for lithium-ion batteries are presented. Thanks to these tests, the general characteristics of a battery such as charge and discharge capabilities, power performances and life cycle can be determined. Then, a new approach for extracting the life cycle of a battery in function of depth of discharge has been developed.

Description: Energies, Vol. 11, Pages 804: Combining an Electrothermal and Impedance Aging Model to Investigate Thermal Degradation Caused by Fast Charging Energies doi: 10.3390/en11040804 Authors: Joris de Hoog Joris Jaguemont Mohamed Abdel-Monem Peter Van Den Bossche Joeri Van Mierlo Noshin Omar Fast charging is an exciting topic in the field of electric and hybrid electric vehicles (EVs/HEVs). In order to achieve faster charging times, fast-charging applications involve high-current profiles which can lead to high cell temperature increase, and in some cases thermal runaways. There has been some research on the impact caused by fast-charging profiles. This research is mostly focused on the electrical, thermal and aging aspects of the cell individually, but these factors are never treated together. In this paper, the thermal progression of the lithium-ion battery under specific fast-charging profiles is investigated and modeled. The cell is a Lithium Nickel Manganese Cobalt Oxide/graphite-based cell (NMC) rated at 20 Ah, and thermal images during fast-charging have been taken at four degradation states: 100%, 90%, 85%, and 80% State-of-Health (SoH). A semi-empirical resistance aging model is developed using gathered data from extensive cycling and calendar aging tests, which is coupled to an electrothermal model. This novel combined model achieves good agreement with the measurements, with simulation results always within 2 °C of the measured values. This study presents a modeling methodology that is usable to predict the potential temperature distribution for lithium-ion batteries (LiBs) during fast-charging profiles at different aging states, which would be of benefit for Battery Management Systems (BMS) in future thermal strategies.

Description: Recently, second-life battery systems have received a growing interest as one of the most promising alternatives for decreasing the overall cost of the battery storage systems in stationary applications. The high-cost of batteries represents a prominent barrier for their use in traction and stationary applications. To make second-life batteries economically viable for stationary applications, an effective power-electronics converter should be selected as well. This converter should be supported by an energy management strategy (EMS), which is needed for controlling the power flow among the second-life battery modules based on their available capacity and performance. This article presents the design, analysis and implementation of a generic energy management strategy (GEMS). The proposed GEMS aims to control and distribute the load demand between battery storage systems under different load conditions and disturbances. This manuscript provides the experimental verification of the proposed management strategy. The results have demonstrated that the GEMS can robustly handle any level of performance inequality among the used-battery modules with the aim to integrate different levels (i.e., size, capacity, and chemistry type) of the second-life battery modules at the same time and in the same application.

Description: In this paper, the performances of various lithium-ion chemistries for use in plug-in hybrid electric vehicles have been investigated and compared to several other rechargeable energy storage systems technologies such as lead-acid, nickel-metal hydride and electrical-double layer capacitors. The analysis has shown the beneficial properties of lithium-ion in the terms of energy density, power density and rate capabilities. Particularly, the nickel manganese cobalt oxide cathode stands out with the high energy density up to 160 Wh/kg, compared to 70–110, 90 and 71 Wh/kg for lithium iron phosphate cathode, lithium nickel cobalt aluminum cathode and, lithium titanate oxide anode battery cells, respectively. These values are considerably higher than the lead-acid (23–28 Wh/kg) and nickel-metal hydride (44–53 Wh/kg) battery technologies. The dynamic discharge performance test shows that the energy efficiency of the lithium-ion batteries is significantly higher than the lead-acid and nickel-metal hydride technologies. The efficiency varies between 86% and 98%, with the best values obtained by pouch battery cells, ahead of cylindrical and prismatic battery design concepts. Also the power capacity of lithium-ion technology is superior compared to other technologies. The power density is in the range of 300–2400 W/kg against 200–400 and 90–120 W/kg for lead-acid and nickel-metal hydride, respectively. However, considering the influence of energy efficiency, the power density is in the range of 100–1150 W/kg. Lithium-ion batteries optimized for high energy are at the lower end of this range and are challenged to meet the United States Advanced Battery Consortium, SuperLIB and Massachusetts Institute of Technology goals. Their association with electric-double layer capacitors, which have low energy density (4–6 Wh/kg) but outstanding power capabilities, could be very interesting. The study of the rate capability of the lithium-ion batteries has allowed for a new state of charge estimation, encompassing all essential performance parameters. The rate capabilities tests are reflected by Peukert constants, which are significantly lower for lithium-ion batteries than for nickel-metal hydride and lead-acid. Furthermore, rate capabilities during charging have been investigated. Lithium-ion batteries are able to store about 80% of the capacity at current rate 2It, with high power cells accepting over 90%. At higher charging rates of 5It or more, the internal resistance impedes charge acceptance by high energy cells. The lithium titanate anode, due to its high surface area (100 m2/g compared to 3 m2/g for the graphite based anode) performs much better in this respect. The behavior of lithium-ion batteries has been investigated at different conditions. The analysis has leaded us to a new lithium ion battery model. This model will be compared to existing battery models in future research contributions.

Description: Battery management systems (BMS) are a key element in electric vehicle energy storage systems. The BMS performs several functions concerning to the battery system, its key task being balancing the battery cells. Battery cell unbalancing hampers electric vehicles’ performance, with differing individual cell voltages decreasing the battery pack capacity and cell lifetime, leading to the eventual failure of the total battery system. Quite a lot of cell balancing topologies have been proposed, such as shunt resistor, shuttling capacitor, inductor/transformer based and DC energy converters. The shuttling capacitor balancing systems in particular have not been subject to much research efforts however, due to their perceived low balancing speed and high cost. This paper tries to fill this gap by briefly discussing the shuttling capacitor cell balancing topologies, focusing on the single switched capacitor (SSC) cell balancing and proposing a novel procedure to improve the SSC balancing system performance. This leads to a new control strategy for the SSC system that can decrease the balancing system size, cost, balancing time and that can improve the SSC balancing system efficiency.

Description: Materials, Vol. 11, Pages 176: On the Ageing of High Energy Lithium-Ion Batteries—Comprehensive Electrochemical Diffusivity Studies of Harvested Nickel Manganese Cobalt Electrodes Materials doi: 10.3390/ma11020176 Authors: Odile Capron Rahul Gopalakrishnan Joris Jaguemont Peter Van Den Bossche Noshin Omar Joeri Van Mierlo This paper examines the impact of the characterisation technique considered for the determination of the L i + solid state diffusion coefficient in uncycled as in cycled Nickel Manganese Cobalt oxide (NMC) electrodes. As major characterisation techniques, Cyclic Voltammetry (CV), Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were systematically investigated. L i + diffusion coefficients during the lithiation process of the uncycled and cycled electrodes determined by CV at 3.71 V are shown to be equal to 3 . 48 × 10 - 10 cm 2 ·s - 1 and 1 . 56 × 10 - 10 cm 2 ·s - 1 , respectively. The dependency of the L i + diffusion with the lithium content in the electrodes is further studied in this paper with GITT and EIS. Diffusion coefficients calculated by GITT and EIS characterisations are shown to be in the range between 1 . 76 × 10 - 15 cm 2 ·s - 1 and 4 . 06 × 10 - 12 cm 2 ·s - 1 , while demonstrating the same decreasing trend with the lithiation process of the electrodes. For both electrode types, diffusion coefficients calculated by CV show greater values compared to those determined by GITT and EIS. With ageing, CV and EIS techniques lead to diffusion coefficients in the electrodes at 3.71 V that are decreasing, in contrast to GITT for which results indicate increasing diffusion coefficient. After long-term cycling, ratios of the diffusion coefficients determined by GITT compared to CV become more significant with an increase about 1 order of magnitude, while no significant variation is seen between the diffusion coefficients calculated from EIS in comparison to CV.