3D tomographic imagery reveals how lithium batteries age
Tomography of a lithium electrode in its initial condition.
Changes are visible after the first charging and discharging cycles.
After a longer period of operation, areas form that reduce performance and can cause short-circuits. © M. Osenberg / I. Manke / HZB
Lithium batteries lose amp-hour capacity over time. Microstructures can form on the electrodes with each new charge cycle, which further reduces battery capacity. Now an HZB team together with battery researchers from Forschungszentrum Jülich, the University of Munster, and partners in China have documented the degradation process of lithium electrodes in detail for the first time. They achieved this with the aid of a 3D tomography process using synchrotron radiation at BESSY II (HZB) as well at the Helmholtz-Zentrum Geesthacht (HZG). Their results have been published open access in the scientific journal "Materials Today".
Whether electric mobility, robotics, or IT - lithium batteries are simply used everywhere. Despite decades of improvements, it has not yet been possible to prevent such batteries from "ageing". Amp-hour capacity is lost with every charge cycle. The processes that lead to this are roughly understood. Now an international team headed by HZB researcher Dr. Ingo Manke has been able to observe with microscopic precision exactly what happens inside the battery at the interfaces between the electrodes during migration of the lithium ions.
3D insights into lithium cells
Manke is an expert in 3D synchrotron tomography, a method that utilises particularly intense X-rays. 3D images can be created of the interior of samples using this non-destructive imaging method with particularly high precision that is available on the BAM beamline at BESSY II. His team investigated a number of different lithium cells during charging and discharging under different cycle conditions. All cells studied had one side of the electrode made of pure lithium, while the other side was constructed of a selection of different electrode materials. Part of the investigation also took place at the Helmholtz-Zentrum Geesthacht.
Formation of microstructures
The tomographic imagery shows how a layer forms between the separator layer and the lithium electrode characterised by microscopic features after only a few charge/discharge cycles. The microscopic features of this layer consist of reaction compounds that form in the electrolyte and can take different forms – from a rather disordered slurry, to moss-like structures, to needle-shaped dendrites that can even cause dangerous short circuits in the battery.
“This gives us for the first time a complete picture of the degradation mechanism in lithium electrodes”, says Manke. It is not only of interest for fundamental understanding of the aging processes in batteries, but also provides valuable directions in the design of more durable batteries.
- Materials chemistry shapes the future of catalysisThe synthesis of materials can serve as a tool for developing smart, adaptive electrocatalysts. This rapidly evolving field of research involves in-situ analytics, data-driven discoveries and autonomous robotics. These new approaches could accelerate the discovery of long-lasting and efficient catalysts for future energy conversion and the decarbonisation of the chemical industry. A recent article by Dr Prashanth Menezes and his team in the renowned journal Angewandte Chemie provides an overview of this research.
- Imaging Ellipsometry for Process Control of Thin-Film DevicesA German–Israeli research team led by Dr. Andreas Furchner has demonstrated how imaging ellipsometry enables non-destructive characterisation and quality control of microstructured MXene thin films during device fabrication. The authors used two complementary ellipsometry approaches for precise, multi-scale access to key material properties. The work positions imaging ellipsometry as a powerful platform for monitoring thin-film uniformity, device integrity, and functionality throughout processing, including critical lithographic steps. The study was published in Applied Physics Letters and selected as an Editor’s Pick.
- BESSY II: How intrinsic oxygen shortens the lifespan of solid-state batteriesAlthough solid-state batteries (SSBs) demonstrate high performance and are intrinsically safe, their capacity currently declines rapidly. A team from the TU Wien, Humboldt-University Berlin and HZB has now analysed a TiS₂|Li₃YCl₆ solid-state half-cell in operando at BESSY II using a special sample environment that allows for non-destructive investigation under real operating conditions. Data obtained by combination of soft and hard X-ray photoelectron spectroscopy (XPS and HAXPES) revealed a new degradation mechanism that had not previously been identified in solid-state batteries. They have gained some surprising insights, particularly regarding the harmful role played by intrinsic oxygen. This study provides valuable information for improving design and handling of such batteries.