Research

Wickelmaschne

The Cluster of Excellence POLiS investigates new battery materials and technology concepts for efficient and sustainable storage of electrical energy. The Cluster aims at developing electrode materials and electrolytes that allow for sustainable systems based on Na, Mg, Zn, Ca, Al, and Cl ions. Major obstacles for the development and use of post-lithium systems and thus the legitimation for our research are:

  • low ionic mobility in solids and liquids,
  • lack of well-designed materials interfaces with suitable charge transfer properties,
  • degradation of active materials and electrolyte, and
  • lack of reversibility of charge- and discharge processes.
Wickelmaschine ZSW/ Elvira Eberhardt
Collaboration

The members of the Cluster represent one of the strongest groups worldwide with a unique portfolio of competences, relevant and necessary for the research and development of post-Li batteries. Collaboration with national and international partners will be done both on a mutual level of direct contacts between researchers and via institutionalized cooperation. An important aspect is the active exchange of personnel to promote scientific excellence and joint projects.

If you are interested in cooperating with us, please contact our spokesperson Maximilian Fichtner (+49 (0)731 50 34201, m.fichtner@kit.edu) or directly one of our Principal Investigators, whose contact details can be found here.

 

Labor Daniel Messling
Forschung Labor Markus Breig

To tackle these issues, the work within the Cluster will be organized along four key topics (Research Units): Electrode Materials, Electrolytes, Interfaces, and Integration & Sustainable Cell Engineering, which reflect the different levels and aspects of electrochemical systems. POLiS will follow a multidisciplinary approach, including solution and materials chemistry, electro-chemistry, predictive atomistic and continuum modelling, as well as chemical and process engineering. Arising concepts for materials design will eventually be validated in full battery cells, examining performance, sustainability and safety issues. A rapidly increasing demand can be observed for future batteries that comprise the following and define our research:

  • Sustainable materials and fabrication processes
  • Increased volumetric/gravimetric energy density
  • Intrinsically safe design
  • Long operational and shelf life
  • Low price per kWh
Modellierung Elvira Eberhardt
Career promotion of early career researchers

The career prospects of young researchers in this Cluster are excellent due to the high scientific and industrial relevance of the research program, which is reflected in the high demand for well-trained specialists in the relevant industries, e.g. battery material suppliers, automotive and electronics industries.

The cluster offers a structured qualification program in cooperation with the Graduate School (GS-EES). You can find further information here. We are looking forward to receiving your unsolicited application, which you should send to the corresponding Principal Investigator who is working in the research area you are interested in.

 

 

Structure

 

Research Topics

Research Unit A (Electrode Materials)

Electrode materials define and limit the amount of energy that can be stored per weight and volume of a battery. Our goal is to identify, synthesize and test new high-capacity post-lithium storage materials and thereby gain an even deeper understanding of their functionality.

Work Package A.1 – Monovalent ions

This work package is essential for reaching the overall goal to deliver large-format SIBs with high performance and to provide suitable materials and electrodes for other work packages. The focus is on layered oxides for positive electrode materials and on carbon-based negative electrodes, investigated in a comprehensive interdisciplinary approach.

Work Package A.2 – Multivalent Ions

This WP focuses on the development of electrode materials for battery chemistries based on multivalent ions (Al, Ca, Mg). The main activities aim at designing and synthesizing new or improved electrode materials. Scope of this WP is to the shed light on transport and kinetics descriptors of multivalent ions into solids by combining experimental and theoretical approaches in order to rationalize the further improvement of the proposed materials.

Work Package A.3 – Anionic Systems

The work package ‘Anionic Systems’ aims to synthesize novel electrode materials and investigate them both experimentally and theoretically. Also it will provide an overview about the interphase formation mechanism in CIB’s. Overall, this work package bridges missing links between electrode, electrolyte in chloride ion batteries and could pave way for the acceleration of research efforts on anionic batteries across the research community.

 

Research Unit B (Electrolyte)

Electrolytes enable the transport of electrically charged particles (ions) between the two electrodes of a battery. The main objective is the identification, synthesis and testing of new, stable and highly efficient liquid or solid transfer systems for post-lithium-ions.

Work Package B.1 – Liquid Electrolytes

Any battery needs an appropriate electrolyte. Thus, the electrolyte is a key component as it connects both electrodes and allows an ionic and electronic communication between both. While at the electrodes ions are either intercalated in an existing structure or converted electrochemically by charge transfer processes, the development of suitable electrolytes faces various challenges, including stability, integrity, SEI formation processes, as well as charge and ion conductivity. This work package aims at the development of liquid electrolytes with high ionic conductivities and chemical and electrochemical stability. To tackle this challenge, different activities have been identified with the goal to synthesize and test new liquid electrolytes for mono- as well as multi-valent ions, to elucidate the mechanisms of ionic transport in these systems and to deduce strategies for better electrolytes.

Work Package B.2 – Solid Electrolytes

Solid-state batteries are considered as the ultimate solution of safety and stability issues, and their exploration and development will be a long-term enterprise. As necessary materials´ basis, solid electrolytes with a combination of various properties need to be developed, of which the high ionic conductivity (combined with low electronic conductivity), the (kinetic) stability in contact with electrode materials and their mechanical properties are important “key performance indicators”. This WP aims to be the cental WP of POLIS to explore, understand, characterize and test solid electrolytes for post-lithium systems.
 

Research Unit C (Interfaces)

We aim to understand the formation and nature of interfaces that form within a post-Li battery - e.g. at the contact between electrode and liquid or solid electrolyte. Their microstructure and chemical composition have a decisive influence on the interface processes within the battery and thus determine, among other things, its performance and longevity.

Work Package C.1 – Structure, Function and Morphology at Metal Electrodes

Metal deposition/dissolution and SEI formation at different metal electrodes will be investigated by various experimental methods in order to obtain detailed mechanistic understanding of the underlying processes, reaching from the charge transfer processes across the interphase to structure formation and morphological changes, SEI formation and side processes like electrolyte decomposition. The experimental studies will be conducted in strong collaboration with theoretical investigations spanning from atomistic investigations of elementary processes to MD simulations and modelling on different length scales. The work program will focus on exemplary studies on a limited number of systems, e.g., Na, Mg and Al deposition from prototypical electrolytes to ensure comparability of the results obtained from different methods.

Work Package C.2 – Structure, Function and Morphology at Carbon Electrodes

This work package aims to get a holistic knowledge about ongoing reactions and kinetics at carbon anodes. To get maximum knowledge gain, we focus in our work on commonly defined carbon systems. The whole available POLiS expertise will be used to clarify ongoing atomic processes within the electrode as well as on the electrode surface considering SEI formation due to electrolyte decomposition during cycling. Only through a complete description and holistic understanding of the electrode behavior, it is possible to improve the electrodes in terms of performance and long cycling stability. A targeted added value is also developed from the methodology of how the individual analysis techniques can be brought together synergistically in order to obtain new, deeper, comprehensive insights into SEI on electrode surfaces. The knowledge gained from the selected model system (SIB) can be transferred to other, new battery systems inside and outside the POLiS cluster and can make a targeted contribution to improving the interface kinetics of next-generation batteries.

Work Package C.3 – Positive Electrodes

For positive electrodes with both solid and liquid electrolytes, the transfer processes at interfaces are decisive for the overall performance of the battery. Interfacial reactions at equilibrium and at various operation states, ion migration kinetics, the role of grain and phase boundaries and dendrite formation are all important aspects that require more indepth investigations to develop a better description of these processes and an understanding of their role in battery performance. Furthermore, interfacial processes are key to understand CEI formation and material degradation. The aim is to use this knowledge in order to optimize kinetics and to suppress degradation processes.

Research Unit D (Integration and Sustainable Cell Engineering)

Up-scaling of materials synthesis and cell construction, studies on the production capability of new technical approaches, assessment of cell safety and life cycle analyses of new technologies will pave the way for technology transfer. Central research data management and the development of automated data analysis tools will flank all work in the Cluster, set standards for the handling of research data and enable integrative, cross-research field data analysis, which we hope will lead to new insights in battery research.

Work Package D.1 – Cell Design & Production

It intends to develop complete processing chains for post-Li systems including the scale-up of materials production, making electrode and cell manufacturing more sustainable and reliable, and the development of material-process-models to generate a deep understanding of the material behavior during processing. WP D1 is therefore, a very interdisciplinary research unit, where chemists, material scientists and process engineers tackle the complex tasks to enable the best performance from new materials in cells by developing the optimal conditions for the material, such as structure of the material, material integrity within the electrode, and overall electrode design, including its further processing up to optimal cell assembly. Another focus is on sustainable electrode and battery production through tailored manufacturing strategies depending on the material, components and composition. In the current phase, the results obtained in the material and process development activities to date are to be combined in order to lead to high-performance POLiS cells with high capacity.

Work Package D.2 – Demonstrator Cell

This WP addresses projects where the most promising post-lithium chemistries developed in POLiS (either material synthesis or its processing) are scaled up to the pouch cell level. On the one hand, a prototype lab-pouch cell serves as a proof of principle for poorly developed cell chemistries (e.g., Aluminum). On the other hand, full industrial-type pouch cells are used to demonstrate the performance of highly developed materials (e.g. Sodium). Na-, Mg- and Al-based chemistries will be studied in the full cell configuration to push each chemistry towards the next developmental step. The results from WP D2 have a great impact on POLiS as the POLiS demonstrator cell’s performance reflects the success of a complex and interdisciplinary research chain throughout all research units. The success of a cell chemistry as a demonstrator on pouch-cell level is the ultimate proof that all aspects of material, interphase, electrolyte material processing and engineering have successfully come together.

Work Package D.3 – Safety & Sustainability

Upscaling of both cathode materials as pouch cells are ongoing in cooperation with BaTec (IAM-ESS) and in similar manner, safety analysis on pouch cell level shall be performed and their heat generation during operation (under normal condition) shall be measured using Heat Flux sensors followed by thermal abuse tests using the Heat-Wait-Seek (HWS) method in the ARC. The sparation of reversible and irreversible heat as well as out gases anaylsis during cell-formation step and during thermal abuse will be also considered.
Also the sustainability of new materials and cell will be analysed in a prospective manner. The focus will be on Na- and Mg-Batteries and fluid and solid electrolyte and the prospective assessment of upscaled production process (including printing production process).The kind of analyses helps to improve the systems under development and prevent mismatch regrading the expectations of stakeholders and society regarding sustainability.

 

Research Unit X (Cross-sectional Topics)

In this research unit, innovative topics such as potassium batteries, organic redox systems, AI-supported virtual simulations or degradation are investigated. For this purpose, the competences from all other units are combined.

Work Package X.1 – High-Energy Potassium Batteries

The overarching goal of this work package is to build high-energy potassium-ion batteries by combining the competences of the clusters’ four original research units to one coherent topical work plan. In recent years, the field of potassium batteries greatly benefitted from the broad knowledge base available for the related monovalent battery systems, namely lithium- and sodium-ion batteries, and accelerated the developments in this field considerably. However, the high reactivity of potassium or potassium storing active materials favours different electrolyte degradation pathways, leading to significant changes of the SEI properties and hence cycle life. It is therefore necessary to detach from established concepts of previous technologies and provide new, system-specific strategies that enable mature potassium-ion systems. Providing a holistic approach, ranging from liquid to solid electrolytes over new electrode material developments to in-depth characterization on material and cell level is a globally unique measure of the work package.

Work Package X.2 Organic Redox Systems

The aim of the WP “Organic Redox Systems” is to purposefully design, synthesize and test new functional organic materials for Post-Li storage. For this purpose, the activities in the WP will focus on two subprojects.

Project I on porphyrin based electrodes and project II on organic electrodes based on quinones and other functional groups. Project I is a further development of the already established organic electrode material of [5,15-bis-(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP), which has a capacity comparable to an LFP cathode, while its rate capability is comparable to that of a supercapacitor (50C). To improve the performance and stability of the post-Li cells with metal porphyrins, we will investigate the influence of different metal centers as well as side groups and introducing of novel functionalities.

In the second project, novel high capacity and high voltage n- and p-type electrodes will be synthesized. Special attention will be paid on designing organic redox materials with limited solubility in the electrolytes. The developed material will be electrochemically analyzed. Upon optimizing the electrode and selecting appropriate electrolyte, it will be tested for post-Li storage (mainly Na-, Mg-, and Ca systems). We anticipate that the work will provide fundamental understanding of the storage mechanism in organic redox systems as well as the establishment of structure-property-performance relationship in the organic electrodes which could be used toward rational and target-oriented development of organic electrodes for post-Li storage.

Work Package X.3 Degradation

This work package is of an overarching nature in POLiS, as degradation processes can reduce the performance and lifetime of all components of post-Li batteries. The majority of projects in this WP follow a rational approach to prevent or suppress degradation processes. By a careful characterization of the degradation, identification of degradation products and a thorough analysis of the origins of these degradation processes, strategies to suppress degradation shall be developed. To achieve this goal, degradation shall be studied both experimentally and theoretically on several length and time scales.

In a second approach, pulsed charging protocols shall be developed from combining a series of experimental techniques with simulation tools that allow for ultra fast charging without shortening the lifetime of post-Li batteries. From an analysis of the optimized charging protocols, also an better understanding of degradation processes shall be developed. These two complimentary approaches will together identify how degradation processes in post-Li batteries can be avoided, so that the lifetime of the batteries will be extended.

Work Package X.4 AI Enhanced Virtual Simulation Chain

Adressing the challenges in developing efficient, sustainable and robust Post-Lithium batteries requires a strongly coupled simulation approach comprising all length and times scales and a systematic coupling to data based simulation techniques. Within the POLiS clusters all necessary simulation competences are available to address this key challenge for accelerating the development of Post-Lithium batteries.
Objectives of the work package are, first, to gain an understanding of the factors underlying these structure and processes in Post-Lithium batteries on all involved length and time scales. Second, by using a vertical multi scale approach with validated algorithms and description to compute parameters that are transferred from one level to the next, the reliability of the theoretical and numerical results shall be improved and coupling to data driven simulation techniques will be developed.

Work Package X.5 Advanced Integrated Data Analysis & Descriptors

The work package addresses the advanced data analysis techniques, high-throughput simulations and the concept of deriving structure-property relationships by descriptors for post-Li battery systems. While the analysis techniques will be used to bridge results from experiments, theoreticians and simulations by data exchange, high-throughput simulations will serve as concept for parameter studies on different scales to create digital twins. With descriptors, correlations between fundamental materials properties and desired or undesired functional properties of the materials are extracted. In order to improve the efficiency of post-Li battery research within the work package as well as within the whole Cluster Kadi4Mat is strongly promoted as the research data infrastructure. Consequently, Kadi4Mat is the base for creating reusable workflows for data analysis, simulations and descriptors.

 

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