Battery system based on storage of electrolyte anions
Researchers at the MEET Battery Research Center of the University of Münster studied a new electrochemical energy storage system, on the so-called dual-ion battery technology. This system is primary supposed to store renewable energies intermediately in stationary systems and to stabilize the grid.
|Project status||Project completed|
|Cycle durability||> 2.000|
|Theo. Gravimetric energy density||ca. 120 Wh/kg|
|Pract. Gravimetric energy density||ca. 40-50 Wh/kg|
|Example application areas||Stationary storage|
|Project duration||Ocotber 2012 until December 2016|
A promising possibility for stationary energy storage are batteries. Regarding lithium-ion batteries, expensive and metal-containing active materials are used. The technically realizable gravimetric energy densities of 120 to 250 Wh/kg are that high, that these batteries will be mainly used in automotive applications. Unlike for the automotive usage, these high energy densities are not necessary for stationary applications, which means that the energy storage capacity is not limited like in the car by the size or the weight of the battery.
For the state-of-the-art lithium ion technology that has been commercially established for more than 25 years, expensive and metal-containing active materials (including cobalt, nickel, manganese) are required. The very high investment costs in the field of active materials for the production of lithium ion batteries (LIBs), therefore, make the use of this storage technology relatively unattractive for large-format stationary energy storage applications. This is due to the fact that in particular the cathode materials, typically lithium-nickel-cobalt-metal oxides, make up a very large proportion of costs (about 21%) of the lithium ion cell. In addition, the processing of the materials to electrodes, typically using organic and toxic solvents, is very cost-intensive, as the solvents must be collected and recycled due to their high toxicity. There are also safety concerns regarding the toxicity of the components cobalt and nickel as well as the use of fluorinated binders for the production of the electrodes. In addition, the issue of long-term availability, especially for the long-term needed large quantities, is being discussed critically for nickel and especially for cobalt.
Against this background, the development of new, cost-effective battery systems for stationary energy storage is an important part of the utilization of regenerative energy sources, which was the starting point of the research project INSIDER. Within the scope of the project, the basic idea of an energy storage system known as the "dual carbon battery", already known since the 1990s, was taken up, and a modified and significantly improved system design, based on an optimized electrolyte and further material variations, was developed.
Large scale energy storage
Within the framework of the research project INSIDER, an innovative concept of the "dual-ion technology" was successfully developed for the first time for the use as stationary energy storage and the cell chemistry was further developed successively as well as application-oriented. In contrast to the classical lithium ion technology, no transition metal oxides (cobalt, nickel, etc.) are used in this novel storage system. Both the anode and the cathode of this battery may consist of graphitic carbon, forming the so-called "dual-graphite cell". These carbons can in turn be produced from renewable raw materials, e.g. by thermal treatment of biological materials or carbonaceous waste. Furthermore, the electrode processing can dispense with the use of toxic organic solvents and fluorinated binders. Instead, water as processing solvent as well as biological, e.g. cellulose-based binders, which are used in yoghurt, can be applied. In combination with the ionic liquids used as electrolytes, it is also possible to ensure a high degree of safety and a long-term cycling stability or lifetime of this storage technology. This system can, thus, make an important contribution to the conservation of important resources, against the background of the use of renewable energies. The good electrochemical performance and high cycling stability of this system have already been published in two patent applications and numerous publications (see below).
A decisive further development of this "dual-ion battery technology" is the optimization of the electrolyte components, in particular of the electrolyte salt anion, which results in a significantly higher stability and safety and, thus, a strongly extended lifetime. For this reason, this technology is particularly attractive for large-scale stationary energy storage applications.
Status and achieved results of the project
The INSIDER project was successfully completed at the end of 2016. The "dual-ion energy storage system", with practically achievable specific energies of ≈40-50 Wh / kg and the use of cost-effective electrode materials, is particularly attractive for stationary energy storage applications, which are necessary for the effective storage of renewable energies. Our research work resulted in two innovative patents for the economical use of the dual-ion battery. [1,2] Due to the close relationship with the lithium ion technology, many production steps for the dual-ion battery can be adapted from the already market-oriented portfolio of lithium ion electrode and cell production. This process includes the processing of the electrodes, in particular the aqueous electrode preparation, as well as the processing of the electrodes to electrochemical cells. System-specific modification and functionalization processes for the production of tailor-made materials, e.g. for current collectors, electrolytes and active materials, were published freely accessible and subsequently evaluated integrally at the technical scale to achieve a rapid market availability of the dual-ion technology. In addition, the company "Power Japan Plus"  announced in 2014 the commercialization of a similar storage system, which is different from our system due to the use of another electrolyte, but which is clearly inferior to our system in terms of safety and long-term cycling stability. The significant improvements shown in the project compared the “Power Japan Plus technology” have already been presented in various publications (see below).
 M. Winter, S. Passerini, S. F. Lux, P. Bieker, T. Placke, H.-W. Meyer, DE-10-2011-054-119.5. https://www.google.ch/patents/DE102011054119A1
 M. Winter, S. Passerini, S. F. Lux, P. Bieker, T. Placke, H.-W. Meyer, DE-10-2011-054-122.5. https://www.google.ch/patents/DE102011054122A1
Research focus and optimisation
The focus of this joint project is the development of a "dual-ion battery system," in which, in contrast to the lithium-ion battery not only lithium ions are intercalated into the anode, but additionally anions are intercalated in the cathode. The project focusses on the following fundamental questions:
- Synthesis, modification and evaluation of suitable electrode materials for the cathode. Carbonaceous compounds are in the focus of research.
- Synthesis and characterization of suitable electrolytes and electrolyte mixtures for the "dual-ion system". The focus of the studies is on electrolytes and in particular anions with high oxidative stability.
- Study and development of a dual-graphite system: A special case of the "Dual-ion system" is the "dual-graphite system" in which both the anode and the cathode are made of graphite. The goal is to find a suitable electrolyte in connection with the electrode materials.
- Investigation of suitable current collectors or protective coatings for aluminum-based current collectors for the application of 5 V cathodes.
- Aqueous electrode manufacturing and their up-scaling, as well as large-area electrodes; Production of a demonstrator cell.
As part of the project, materials for current collectors, electrolytes, active materials and functional coatings are examined for their applicability for the dual-ion technology. Modification and functionalization procedures are developed and the entire process chain for electrode production is evaluated on a pilot scale to achieve a rapid market availability of dual-ion technology.
WG Winter, WWU Münster
The focus of this sub-project was the development of a fundamental understanding of the functions of anion intercalation into graphitic carbons, taking into account various electrochemical parameters. A further focus was the identification and optimization or modification of active materials which were suitable for the storage of anions and are characterized by good electrochemical properties (high capacity, high Coulombic efficiency, high energy efficiency, high capacity retention, high energy density and specific energy, etc.). In this respect, the identification and optimization of suitable electrolyte components which were suitable for application in the dual-ion battery (high-voltage or oxidative-stable electrolytes and anions, such as ionic liquids) was also of great importance. The overarching goal was the analysis and assessment of the influence of the active material and electrolyte properties on the electrochemical performance in order to establish material recommendations. Finally, an assessment of the dual-ion technology in terms of its competitiveness against other battery technologies should be carried out.
WG Wiemhöfer, WWU Münster
The project focused on the synthesis of high voltage stable electrolyte systems. The development of electrolyte materials was not limited to the synthesis of new liquid electrolytes with increased thermal stability, but also included the study on novel functional gel hybrid systems.
WG Guillon/Uhlenbruck, FZ Jülich
The main task was the development of solid, electron conductive and corrosion-resistant current collector protective layers. This work comprised three main steps: (i) the preparation of the material provided by the project partners (avoidance of agglomerates before coating), (ii) the actual coating, (iii) drying and heat treatment for the purpose to achieve the desired phase at the surface of the active material without damaging the material (or also the supporting structure) itself. For this, two methods were applied: The sol-gel method and the chemical vapor deposition (CVD) to achieve a surface coating.
WG Wirth, FAU Erlangen
The manufacture, modification and functionalization of carbon electrode materials for an optimum anion intercalation was the focus of this sub-project. These carbonaceous materials were optimized by functionalization of the surface with respect to their electrochemical properties, such as by removing amorphous carbon layers and/or surface functionalization. The latter was achieved by a dry coating of materials with nanoscale particles and by deposition of covalently bonded thin layers with an ALD process.
WG Kwade, TU Braunschweig
The aim was the particle and procedure development of various processes for the pre-treatment of active materials and for the manufacturing of high-performance electrode structures for the dual-ion technology. The key challenge in the development of this storage technology was to set the material and electrode structure (pore radius distribution) with respect to the efficiency of the anion intercalation. The AG Kwade aimed to point out structure-property relationships and process-structure-property relationships. Thus, a relation of cause and effect could be created in order to obtain a deeper understanding of the processes for further optimization of the dual-ion technology.
G. Schmuelling, T. Placke, R. Kloepsch, O. Fromm, H.-W. Meyer, S. Passerini, M. Winter, "X-ray diffraction studies of the electrochemical intercalation of bis(trifluoromethanesulfonyl)imide anions into graphite for dual-ion cells", Journal of Power Sources, 2013, 239, Pages 563-571; DOI: 10.1016/j.jpowsour.2013.03.064
T. Placke, O. Fromm, S. Rothermel, G. Schmuelling, P. Meister, H.-W. Meyer, S. Passerini, M. Winter, “Electrochemical Intercalation of Bis(trifluoromethanesulfonyl) imide Anion into Various Graphites for Dual-ion Cells”, ECS Trans., 2013, 50(24), Pages 59-68; DOI: 10.1149/05024.0059ecst
T. Placke, S. Rothermel, O. Fromm, P. Meister, S. F. Lux, J. Huesker, H.-W. Meyer, M. Winter, “Influence of Graphite Characteristics on the Electrochemical Intercalation of Bis(trifluoromethanesulfonyl) imide Anions into a Graphite-based Cathode”, J. Electrochem. Soc., 2013, 160(11), Pages A1979-A1991; DOI: 10.1149/2.027311jes
S. Rothermel, P. Meister, G. Schmuelling, O. Fromm, H.-W. Meyer, S. Nowak, M. Winter, T. Placke, “Dual-Graphite Cells based on the Reversible Intercalation of Bis(trifluoromethanesulfonyl) imide Anions from an Ionic Liquid Electrolyte“, Energy & Environmental Science, 2014, 7(10), Pages 3412-3423; DOI: 10.1039/C4EE01873G
P. Meister, V. Siozios, J. Reiter, S. Klamor, S. Rothermel, O. Fromm, H.-W. Meyer, M. Winter, T. Placke, “Dual-Ion Cells based on the Electrochemical Intercalation of Asymmetric Fluorosulfonyl-(trifluoromethanesulfonyl) imide Anions into Graphite”, Electrochim. Acta, 2014, 130, Pages 625-633; DOI: 10.1016/j.electacta.2014.03.070
T. Placke, G. Schmuelling, R. Kloepsch, P. Meister, O. Fromm, P. Hilbig, H.-W. Meyer, M. Winter, “In situ X-ray Diffraction Studies of Cation and Anion Intercalation into Graphitic Carbons for Electrochemical Energy Storage Applications”, Z. Anorg. Allg. Chem., 2014, 640(10), Pages 1996-2006; DOI: 10.1002/zaac.201400181
O. Fromm, P. Meister, X. Qi, S. Rothermel, J. Huesker, H.-W. Meyer, M. Winter, T. Placke, “Study of the Electrochemical Intercalation of Different Anions from non-aqueous Electrolytes into a Graphite-based Cathode”, ECS Trans., 2014, 58(14), Pages 55-65; DOI: 10.1149/05814.0055ecst
S. Rothermel, P. Meister, O. Fromm, J. Huesker, H.-W. Meyer, M. Winter, T. Placke, “Study of the Electrochemical Behavior of Dual-Graphite Cells using Ionic Liquid-based Electrolytes”, ECS Trans., 2014, 58(14), Pages 15-25; DOI: 10.1149/05814.0015ecst
T. Placke, V. Siozios, S. Rothermel, P. Meister, C. Colle, M. Winter, “Assessment of Surface Heterogeneity: A Route to Correlate and Quantify the 1st Cycle Irreversible Capacity Caused by SEI Formation to the Various Surfaces of Graphite Anodes for Lithium Ion Cells”, Zeitschrift für Physikalische Chemie, 2015, 229(9), Pages 1451-1469; DOI: 10.1515/zpch-2015-0584
A. Heckmann, P. Meister, H.-W. Meyer, A. Rohrbach, M. Winter, T. Placke, “Synthesis of Spherical Graphite Particles and Their Application as Cathode Material in Dual-Ion Cells”, ECS Transactions, 2015, 66(11), Pages 1-12; DOI: 10.1149/06611.0001ecst
J. Huesker, M. Winter, T. Placke, “Dilatometric Study of the Electrochemical Intercalation of Bis(trifluoromethanesulfonyl) imide and Hexafluorophosphate Anions into Carbon-Based Positive Electrodes”, ECS Transactions, 2015, 69, Pages 9-21; DOI: 10.1149/06922.0009ecst
K. Beltrop, P. Meister, S. Klein, A. Heckmann, M. Grünebaum, H.-D. Wiemhöfer, M. Winter, T. Placke, “Does Size really Matter? New Insights into the Intercalation Behavior of Anions into a Graphite-Based Positive Electrode for Dual-Ion Batteries”, Electrochimica Acta, 2016, 209, Pages 44-55; DOI: 10.1016/j.electacta.2016.05.012
P. Meister, G. Schmuelling, M. Winter, T. Placke, “New Insights into the Uptake/Release of FTFSI- Anions into Graphite by Means of in situ Powder X-Ray Diffraction”, Electrochemistry Communications, 2016, 71, Pages 52-55; DOI: 10.1016/j.elecom.2016.08.003
A. Heckmann, M. Krott, B. Streipert, S. Uhlenbruck, M. Winter, T. Placke, “Suppression of Aluminum Current Collector Dissolution by Protective Ceramic Coatings for Better High-Voltage Battery Performance”, ChemPhysChem, 2017, 18, Pages 156-163; DOI: 10.1002/cphc.201601095
P. Meister, X. Qi, R. Klöpsch, E. Krämer, B. Streipert, M. Winter, T. Placke, “Anodic Behavior of the Aluminum Current Collector in Imide Based Electrolytes - Influence of the Solvent, the Operating Temperature and the Native Oxide Layer Thickness”, ChemSusChem, 2017, 10(4), Pages 804-814; DOI: 10.1002/cssc.201601636
P. Meister, O. Fromm, S. Rothermel, J. Kasnatscheew, M. Winter, T. Placke, “Sodium-Based vs. Lithium-Based Dual-Ion Cells: Electrochemical Study of Anion Intercalation/De-Intercalation into/from Graphite and Metal Plating/Dissolution Behavior”, Electrochimica Acta, 2017, 228, Pages 18-27; DOI: 10.1016/j.electacta.2017.01.034