The transition to electrification requires lithium-ion batteries with higher energy density, better cycle stability and a longer service life. This requires new electrode materials to drive the next generation of batteries. Due to its high theoretical specific storage capacity, silicon (Si) holds enormous potential for lithium-ion batteries (LIBs) and solid-state batteries (SSBs) and opens up new possibilities for the efficient storage of energy.
Despite progress in understanding the electrochemical properties of Si anodes, the effects of volume changes and mechanical stress on the crystalline structure of silicon are still poorly understood. The failure of batteries is mainly caused by the chemically induced formation of the so-called silicon electrolyte interface (SEI). This occurs on freshly exposed silicon surfaces and leads to the loss of lithium and electrolyte, which results in a reduction in capacity. In addition to these chemical processes, lithium intercalation in the silicon particle also leads to a transition from the crystalline to the amorphous phase.
Literature shows that similar phase transitions can occur under mechanical stress. Shear bands and crystallographic defects destabilize the crystal lattice.
Research using the latest equipment (4D-STEM, FESEM, synchrotron X-ray nanotomography and AI-assisted microstructure analysis) at MCL and research partners showed that shear bands can occur in Si-based anodes, triggered by stresses during cycling. These transitions promote non-uniform SEI growth and significantly change the voltage distribution in the anode. This results in phase-dependent lithiation of the active material. However, the formation of successive soft and hard phases in the silicon can also have a stabilizing effect by reducing cracking and particle destruction and delaying battery failure.
Impact and effects
The published study (image and information on the right) highlights the interplay of mechanical and chemical degradation processes and provides new insights into the action of silicon anodes as a result of lithiation. The control of interfacial kinetics and the development of optimized silicon architectures are crucial for the further development of improved energy storage.
In the ASSESS project, MCL and its partners (see below) are jointly creating a basis for future innovations in battery technology and thus for the sustainable storage of energy for electromobility and other applications.
Project coordination (Story)
Priv.-Doz. Dr. Roland Brunner
Group Leader Material and damage analytics
Materials Center Leoben Forschung GmbH
T +43 (0) 676 848883 620
roland.brunner(at)mcl.at
IC-MPPE / COMET-Zentrum
Materials Center Leoben Forschung GmbH
Vordernberger Straße 12
8700 Leoben
T +43 (0) 3842 45922-0
mclburo(at)mcl.at
www.mcl.at
Project partners
• Materials Center Leoben Forschung GmbH, Austria
• Montanuniversität Leoben, Chair of Materials Physics, Austria
• Montanuniversität Leoben, Chair of Functional Materials and Materials Systems, Austria
• Norwegian University of Science and Technology, Norway
• TU Graz - Institute of Electron Microscopy and Nanoanalysis, Austria