Materials for Energy Storage

Prof Riedel's research team has been working on the latest battery systems, lithium-ion as well as beyond lithium-ion battery since 2003. Novel SiOC- and SiCN-based polymer-derived ceramics for the next-generation electrochemical energy storage have been developed and investigated.

The focus is on innovative storage materials that can be used as electrodes in lithium-ion, sodium-ion and lithium-sulphur batteries as well as in supercapacitors. The main goal is to identify novel storage materials with potentially higher energy densities that are safe and can be produced at lower costs. The rapid charging and discharging over many cycles is one of the main focuses of this research.

PDCs for Ion-Battery-Strategy

Within Re2LiB project new strategies for the sustainable processing of Li-ion batteries at the end of their service life in electric vehicles will be developed.

Project funding: HA Hessen Agentur GmbH, Innovationsförderung Hessen- Förderung der Elektromobilität (2020 – 2022)

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Project in a frame of Beethoven Classic 3, Polish-German Funding Initiative granted by the Polish National Science Centre (NCN) and Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), 2020-2023.

Partners:

Dr. Ing. Monika Wilamowska, Dr. Ing. Andrzej Nowak, Gdansk University of Technology (PL)

Dr. Grzegorz Trykowski, Nicolaus Copernicus University of Torun (PL)

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Sodium-Ion and sodium Metal BAtteries for efficient and sustainable next-generation energy storage – (SIMBA)

A consortium led by the TU is breaking new ground in sustainable energy storage. The “SIMBA” project aims to develop a safe, low-cost and environmentally friendly all-solid-state-sodium battery for stationary use, which could help solve a major problem of the energy revolution.

The EU is supporting SIMBA with eight million euros within the "Horizon 2020” program.

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M. Sc. Fangmu Qu

Supervisors: Ralf Riedel, Magdalena Graczyk-Zajac

Low electronic conductivity and shuttle effect of sulfur (S) hinders its application in Li-S battery [1]. Numerous carbon materials are used as host for solving above issues [2-3]. However, enough robustness for accommodating the volume expansion during cycles is not easy achieved by most of carbon materials. Porous carbon-rich SiCN/SiOC ceramic matrix is a great option for hosting S due to its robust structure stability and good electronic conductivity [4-6]. Now, we synthetized a carbon-rich SiCN ceramics with tailored morphology under different pyrolysis temperature and infiltrate sulfur into the porous ceramic matrices to form SiCN-S composites used for sulfur cathode. Then we investigated their morphology and performance. Under different pyrolysis temperature, SiCN shows different content and morphology, resulting in various electrochemical performance. SiCN ceramic pyrolyzed at 1000 ℃ exhibits best cycle stability compared with others due to it has more amorphous free carbon and nitrogen. Our work shows a new strategy for using ceramic as host material for S in Li-S battery. And in our subsequent works, we will further investigate other factors of the synthesis of SiCN-S composites on electrochemical performance as well as potential of SiOC ceramics served as sulfur host for cathode in Li-S battery.

References

[1] H.-J. Peng, J.-Q. Huang, X.-B. Cheng, Q. Zhang, Review on High-Loading and High-Energy Lithium-Sulfur Batteries, Advanced Energy Materials, 7 (2017).

[2] Y. Zhao, W. Wu, J. Li, Z. Xu, L. Guan, Encapsulating MWNTs into hollow porous carbon nanotubes: a tube-in-tube carbon nanostructure for high-performance lithium-sulfur batteries, Adv Mater, 26 (2014) 5113-5118.

[3] D. Gueon, J.T. Hwang, S.B. Yang, E. Cho, K. Sohn, D.K. Yang, J.H. Moon, Spherical Macroporous Carbon Nanotube Particles with Ultrahigh Sulfur Loading for Lithium-Sulfur Battery Cathodes, ACS Nano, 12 (2018) 226-233.

[4] J. Kaspar, M. Graczyk-Zajac, S. Choudhury, R. Riedel, Impact of the electrical conductivity on the lithium capacity of polymer-derived silicon oxycarbide (SiOC) ceramics, Electrochimica Acta, 216 (2016) 196-202.

[5] M. Graczyk-Zajac, D. Vrankovic, P. Waleska, C. Hess, P.V. Sasikumar, S. Lauterbach, H.-J. Kleebe, G.D. Sorarù, The Li-storage capacity of SiOC glasses with and without mixed silicon oxycarbide bonds, Journal of Materials Chemistry A, 6 (2018) 93-103.

[6] D. Vrankovic, M. Graczyk-Zajac, C. Kalcher, J. Rohrer, M. Becker, C. Stabler, G. Trykowski, K. Albe, R. Riedel, Highly Porous Silicon Embedded in a Ceramic Matrix: A Stable High-Capacity Electrode for Li-Ion Batteries, ACS Nano, 11 (2017) 11409-11416.

M. Sc. Mathias Storch

Supervisors: Ralf Riedel, Magdalena Graczyk-Zajac in cooperation with Mercedes-Benz AG, Kirchheim u.T.

The PhD study deals with the investigation of the degradation mechanism of lithium-ion cells aged under calendar and cycle operation. For both operation modes, a comprehensive aging test comprising 54 pouch-bag type lithium-ion cells with a capacity of 50.8 Ah (calendar) and 31 pouch-bag type lithium-ion cells with a capacity of 39 Ah (cycle) was performed for a period of ~2 years, each. Afterwards, an extensive post-mortem analysis was performed with those degraded cells. The cells were opened in argon atmosphere; the electrode materials were separated and prepared for further analysis using different material characterization methods. The methods of ICP-OES, SEM, Raman spectroscopy and XPS-depth profiling in combination with the data from electrochemical testing revealed a storage state of charge dependent growth of the solid electrolyte interphase. In the cycle aging test, the operation parameters temperature, cut-off voltage, depth of discharge, and discharge current were varied separately. In that case, the electrodes were analyzed using ICP-OES, (FIB-) SEM, XRD, STEM and XPS-depth profiling. The main degradation mechanism found are the growth of the solid electrolyte interphase, gas evolution, lithium plating, transition metal dissolution, and cathode particle cracking. In addition, inhomogeneous degradation, i.e. gas-assisted lithium plating and lithium plating resulting from thermal, current and Li- concentration gradients have been observed and formation mechanisms are proposed.

M. Sc. Nan Chai

Supervisors: Ralf Riedel, Zhaoju Yu, Magdalena Graczyk-Zajac

Polymer-derived ceramics (PDCs), including silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) ceramics, have attracted much attention due to their high theoretical capacity and stability with respect to a prolonged cycling [1-2]. During charge/discharge, the major Li-ion host sites are accordingly the interstitial spaces and edges of graphene, as well as the carbon layers within the free carbon phase. Meanwhile, Carbon nanotubes (CNTs) and graphene [3-4] have also attracted much interest for their potential applications as battery material due to their excellent electrical conductivity and outstanding storage properties. Therefore, introducing CNTs and graphene into PDCs represents a highly promising approach to enhance the electrochemical performance of these materials. A chemical approach, as the drawing below shows, to blend PDCs with CNTs and graphene has already been investigated in detail. The electrochemical (EC) test have revealed high capacities of more than 600 mAh/g in line with stability over 100 cycles.

References:

[1] W. Xing, A.M. Wilson, K. Eguchi, G. Zank, J.R. Dahn, Pyrolysed polysiloxanes for use as anode materials in lithium-ion batteries, J. Electrochem. Soc. 144 (1997) 2410–2416.

[2] Wilson A M, Zank G, Eguchi K, et al. Pyrolysed silicon-containing polymers as high capacity anodes for lithium-ion batteries. Journal of Power Sources, 1997, 68(2): 195-200.

[3] Yuan, Wenyu, et al. The applications of carbon nanotubes and graphene in advanced rechargeable lithium batteries, Journal of Materials Chemistry A, 4.23 (2016): 8932-8951.

[4] Wu, Heng, et al. Graphene based architectures for electrochemical capacitors, Energy Storage Materials, 5 (2016): 8-32.