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Publications (44)
Lithium deposition on anode surfaces can lead to fast capacity degradation and decreased safety properties of Li-ion cells. To avoid the critical aging mechanism of lithium deposition, its detection is essential. We present workflows for the efficient detection of Li deposition on electrode and cell level. The workflows are based on a variety of co...
The cycle life of Li-ion batteries is limited by aging on the material and electrode level. Prolonging the battery life helps increasing sustainability, reducing the dependency from critical raw materials, and safes costs. The first step in extending battery life is to understand the underlying degradation mechanisms. Post-Mortem analysis of commer...
Bending of electrodes in certain cell designs (cylindrical cells or flat wound jellyrolls) leads to curved electrodes (curvature κ). For double side-coated electrodes, this curvature leads to convex and concave sides of the coating. In this work, we describe the effect of curved electrodes on the microstructure and aging. From a simple elastic mode...
We present an extensive analysis of Li-ion battery ageing via Arrhenius plots. The V-shaped Arrhenius plots show minima at an optimum temperature corresponding to the longest cycle-life. The V-shape of the Arrhenius plots signifies the crossover between the two dominating ageing mechanisms – solid electrolyte interphase (SEI) growth in the high tem...
The ageing rate and consequentially service life of mass-produced lithium-ion batteries depends on many external and internal factors. Some of the more important ones are the charge-discharge rate, ambient temperature, electrode thickness and state of health (SoH). This makes the estimation of the lifetime of battery cells very challenging and time...
In addition to the costs, high energy density, and fast-charging capability, safety of Li-ion batteries is most important-even after long-term usage or abusive conditions. A new combination of Accelerating Rate Calorimetry (ARC) coupled with a mass spectrometer (MS) [1] to study commercial 18650-type Li-ion cells will be shown. This novel ARC-MS se...
Aim Safety is one of the most important parameters that control the extent of use and spread of lithium-ion batteries (LIBs) worldwide. With the progressive development of LIBs in energy density, improving their safety is becoming necessary for EV applications. Developing an analytical tool for on-line gas detection during the thermal runaway of LI...
In addition to the costs, high energy density, and fast-charging capability, safety of Li-ion batteries is very important-even after long-term usage or abusive conditions. In this research, a new combination of Accelerating Rate Calorimetry (ARC) coupled with a mass spectrometer (MS) [1] to study commercial 18650-type Li-ion cells is developed. Thi...
The Cover Feature illustrates the operando analysis of gas evolving from an 18650‐type Li‐ion cell after provoked venting. This measurement became possible by coupling of accelerated rate calorimetry (ARC) to cause venting and thermal runaway of Li‐ion cells intentionally and gas analysis by mass spectrometry (MS). The molecules in the evolved gas...
Besides high energy density, fast‐charging capability, and costs, safety of Li‐ion batteries is fundamentally important – even after long‐term usage or abusive conditions. In this paper, a new combination of accelerating rate calorimetry (ARC) coupled with a mass spectrometer (MS), as well as cell resistance and audio recording was applied to study...
Cu dissolution in Li-ion cells during over-discharge to 0 V was investigated by Post-Mortem analysis. Commercial 18650 type cells with graphite anode and NMC/LMO cathodes as well as pilot-scale pouch full cells with graphite/NMC chemistry with reference electrode were investigated. The effects of discharge time at 0 V in the range of 100 h to 1000...
A method based on glow discharge optical emission spectroscopy (GD‐OES) depth profiling is developed to detect copper deposition on graphite electrodes for the first time. Commercial 18650 cells with graphite anodes were subject to Cu dissolution by over‐discharge to 0 V. On a first approach, the depth profiles for Cu show significant differences f...
Novel mobile and stationary applications require batteries with increasing energy density / specific energy, fast-charging capability, ¹ and long life-time – while maintaining a high safety level. However, there is a dearth of knowledge on the interactions between these parameters. Additionally, the data sheets of commercial cells contain usually o...
Si as active material has become a prominent candidate as anode material for high-energy Li-ion cells. Unfortunately, Si in Si/C anodes is hard to quantify by established methods, e.g. with ICP-OES no depth profile can be obtained and HF is needed for digestion.
Here, we present a semi-quantitative depth profiling method based on glow discharge opt...
Addition of a certain amount of Si to state of the art graphite anodes has become the most prominent option to increase the energy density of Li-ion cells. However, the distribution of Si in the depth of Si/C anodes is difficult to measure with established methods. In this paper, we present a semi-quantitative depth profiling method based on glow d...
Si/C composite anodes are of great interest for increasing the energy density of Li-ion cells. We report the applicability of the glow discharge optical emission spectroscopy (GD-OES) technique to detect and quantify the Si distribution in Si/C composite anodes. The calibration was developed in the range of 0–100 wt.-% Si by lab coated samples, whi...
This study analyzed a prototype of a pouch cell containing silicon alloy anodes with the potential to significantly increase the energy density, resulting in improved autonomy for electric vehicles. An electrical characterization campaign was performed, resulting in three main observations. Firstly, measurements showed a high energy density, althou...
The standard format for cylindrical Li-ion cells is about to change from 18650-type cells (18mm diameter, 65mm height) to 21700-type cells (21mm diameter, 70mm height). We investigated the properties of five 18650 cells, three of the first commercially available 21700, and three types of the similar 20700 cells in detail. In particular, the (i) spe...
Lithium deposition on graphite anodes is an unwanted side reaction in lithium ion batteries, which significantly contributes to accelerated ageing of the cells. Lithium deposition is connected not only to a drastic decrease of lifetime , but also limits fast-charging capability and can cause severe safety issues due to increased exothermic reaction...
Li-ion cells are used in a variety of mobile and stationary applications. Their use must be safe under all conditions, even for aged cells in second-life applications. In the present study, different aging mechanisms are taken into account for accelerating rate calorimetry (ARC) tests. 18650-type cells are cycled at 0◦C (Li plating expected) and at...
Application of Li-ion batteries for transportation not only requires long cycling life but also the preservation of the electrochemical performance during the resting period. For certain car usage this resting time could be predominant compared with the cycling activity and is referred to as calendar aging. To understand the aging mechanisms during...
Metallic lithium deposition is a typical aging mechanism observed in lithium-ion cells at low temperature and/or at high charge rate. Lithium dendrite growth not only leads to strong capacity fading, it also causes safety concerns such as short-circuits in the cell. In applications such as electric vehicles, the use of lithium-ion batteries combine...
Commercialization of many Li-ion cell chemistries is hindered by undesirable processes occurring during usage of Li-ion batteries, limiting their lifetime. One such process is the development of temperature gradients, especially in large-format cells, leading to uneven utilization of electrode material.1 Such inhomogeneity could locally accelerate...
Durability and performance of Li-ion cells are impaired by undesirable side reactions, observed as capacity decrease and resistance increase during their usage. This degradation is caused by aging mechanisms on the material level including surface film formation, especially in the case of graphite-based anodes. The present study evaluates the appli...
Commercialization of many Li-ion cell chemistries is hindered by undesirable processes occurring during usage of Li-ion batteries, limiting their lifetime. One such process is the development of temperature gradients, especially in large-format cells, leading to uneven utilization of electrode material. ¹ Such inhomogeneity could locally accelerate...
Improvement of life-time is an important issue in the development of Li-ion batteries. Aging mechanisms limiting the life-time can efficiently be characterized by physico-chemical analysis of aged cells with a variety of complementary methods. This study reviews the state-of-the-art literature on Post-Mortem analysis of Li-ion cells, including disa...
Due to the high chemical reactivity of metallic lithium, safety and life-time of Lithium-ion cells are closely related to the aging phenomenon of lithium plating [1–5]. Lithium plating on graphite anodes can occur during charging at low temperatures, high C-rates, and high states-of-charge [1,3,4]. However, lithium deposition depends also on the co...
Li-ion batteries are good candidates for electric vehicles and stationary applications due to their high power and energy densities. It is well known that the lifetime of lithium ion batteries is limited by undesirable side reactions. Moreover, these side reactions can affect different parts of the battery including the electrolyte, the active mate...
Due to the high chemical reactivity of metallic lithium, safety and life-time of Lithium-ion cells are closely related to the aging phenomenon of lithium plating [1–5]. Lithium plating on graphite anodes can occur during charging at low temperatures, high C-rates, and high states-of-charge [1,3,4]. However, lithium deposition depends also on the co...
Deposition of metallic Li on graphite anodes is a critical aging mechanism happening in Lithium-ion cells during charging at low temperatures, high C-rates and high states-of-charge [1,2]. Furthermore, Li deposition can also have negative effects on cell safety [3]. The cause for deposition of Li on anodes are negative anode potentials vs. (Li/Li+)...
Deposition of metallic Li is a severe aging mechanism in Lithium-ion cells. This study evaluates the influence of the main operating parameters leading to deposition of Li: temperature, charging C-rate, and end-of-charge voltage. Therefore both, graphite anodes and NMC cathodes from commercial 16Ah pouch cells are reconstructed into 3-electrode ful...
Deposition of metallic Li on graphite anodes is a critical aging mechanism happening in Lithium-ion cells during charging at low temperatures, high C-rates and high states-of-charge [1,2]. Furthermore, Li deposition can also have negative effects on cell safety [3]. The cause for deposition of Li on anodes are negative anode potentials vs. (Li/Li ⁺...
The study evaluates the capacity fade of commercial 3.25 Ah 18650-type cells with NCA cathodes and graphite anodes quantitatively for different temperatures and charging strategies. For standard constant current / constant voltage (CC-CV) charging, the aging rate for cells cycled at 0.5C is increased with decreasing temperature in the range of 25 °...
Glow discharge optical emission spectroscopy (GD-OES) is employed to detect and quantify Li deposition as a function of depth on graphite electrodes. Commercial cells with graphite anodes were subject to Li plating by being cycled at 5°C. A comparison is made with graphite electrodes with solid electrolyte interphase (SEI) after formation. Depth pr...
In typical applications of lithium-ion batteries, the cells are monitored in order to guarantee a safe and stable performance during operation. Therefore, methods to characterize aging processes in a non-destructive way are desired. In this work, internal resistance and power capability calculated from time domain measurements are investigated. Tes...
Material degradation is an issue limiting the life-time of Lithium-ion batteries. This study conducts quantitative observations of performance and material degradation in a commercial high-power Lithium-ion battery as a function of aging time and ambient temperature. Batteries are cycled until different states-of-health (SOHs) in the range of 100%...
The reactor is used for producing nano-particles of metal from volatile moieties in flow through mode. The reactor comprises at least a first feeder and a second feeder on one end of the vessel. The first feeder feeds the moiety in the form of an educt fluid into the reactor. This fluid is a mixture of metal moieties and a bearer fluid, entering th...
The study observes thermal behavior of six Lithium-ion batteries with different cell designs. In operando temperature measurements are conducted using a thermographic camera as well as internal and external temperature sensors. The investigated cell designs include pouch cells as well as two high-power and two high-energy 18650 battery types. It is...
The formation of metallic lithium on the negative graphite electrode in a lithium-ion (Li-ion) battery, also known as lithium plating, leads to severe performance degradation and may also affect the cell safety.
This study is focused on the nondestructive characterization of the aging behavior during long-term cycling at plating conditions, i.e. lo...
The effects of temperatures in the range of -20 °C to 70 °C on the ageing behaviour of cycled Lithium-ion batteries are investigated quantitatively by electrochemical methods and Post-Mortem analysis. Commercial 18650-type high-power cells with a LixNi1/3Mn1/3Co1/3O2/LiyMn2O4 blend cathode and graphite/carbon anode were used as test system. The cel...
A stochastic model is proposed for the efficient simulation of complex three-dimensional microstructures consisting of two different phases. The model is based on a hybrid approach, where in a first step a graph model is developed using ideas from stochastic geometry. Subsequently, the microstructure model is built by applying simulated annealing t...
In this work we evaluate the safety characteristics of an advanced Sn–C/EC:PC 1:1, LiPF6 PVdF gel electrolyte (GPE)/LiNi0.5Mn1.5O4 lithium ion polymer battery. The tests are performed by using a complex analysis that combines Differential Scanning Calorimetry (DSC) Thermal Gravimetric Analysis (TGA), and Mass Spectrometry (MS). This is a very conve...
Nickel hydroxide is widely used as an active material in Ni-Cd and Ni-MeH batteries. The electrochemical properties such as
charge acceptance, electronic conductivity etc. can be dramatically influenced by doping β-Ni(OH)2 with small amounts of Co, Cd or Zn. Stabilizing of α-Ni(OH)2 offers the possibility to obtain nickel electrodes with enhanced c...
