AG13 battery

Russian research and development visualizes battery electrode layers and provides new insights into AG13 battery structure

There are many processes at work during the charging and discharging of lithium batteries, and despite the growing popularity of this technology, some of these processes are still not fully understood.

Observing these events can lead to ways to improve performance, but this is not easy given the complex structure of lithium batteries and the limitations of microscopy techniques.

Scientists at the Skoltech Energy Science and Technology Center in Moscow have developed a method to take a closer look at such a process: the formation of a solid electrolyte interface (SEI), which the researchers describe as a thin layer of electrolyte reduction products that form on the surface of AG13 battery anodes during the first few cycles.

According to the Skoltech Group, the formation of this thin film is crucial to slowing down battery degradation. However, measuring SEI formation in situ has proven difficult, and replacing commercial battery materials with more uniform alternatives in the laboratory is the only way to achieve results.

Battery-grade materials are powders, and visualizing dynamic processes on their surface by AFM (atomic force microscopy), especially in liquid environments, is challenging, said Sergey Luchkin, a scientist at Skoltech. Standard battery electrodes are too rough for such measurements, and isolated particles tend to fall off the substrate during scanning. To address this problem, we embedded the particles in epoxy and made a cross-section so that the particles were firmly fixed to the substrate.

In addition to highly oriented pyrolytic graphite, one of the more uniform carbon materials previously used to study the SEI, the Skoltech group applied its cross-section process to electrodes of mesocarbon microbead graphite and non-graphitizable amorphous carbon, allowing the researchers to observe the thickness of the formed SEI layer and evaluate its electrical and mechanical properties.

Applying the cross-section method to a lithium-manganese-cobalt cathode revealed no signs of SEI layer formation. According to the scientists, this result suggests that future studies should acknowledge the fundamental differences in the stabilization mechanisms between anodes and cathodes in lithium batteries.

"The spatially resolved studies of battery interfaces and interphases, detailed in this work, provide important new insights into the structure and evolution of the anode SEI," said Skoltech Professor Keith Stevenson. "As a result, they provide solid guidelines for rational electrolyte design to improve the safety of high-performance batteries."

According to the team's investigation, the results published in Scientific Reports show that the conditions for SEI formation vary significantly depending on the electrode material. SEI adhesion was found to be related to the surface roughness of the electrode. The study found that rough surfaces can quickly reduce degradation because the SEI is able to penetrate more porous surfaces and achieve better adhesion.

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