Lithium-ion batteries are a key element in our clean energy transition, but they tend to degrade after a certain number of charging cycles, leading researchers to look for answers.

To better understand what's happening inside these batteries, teams have begun using X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS), according to a report shared by TechXplore.

It explained that the quality of lithium-ion batteries has increased over the years, with the combination of layered nickel-manganese-cobalt (NMC) oxides and graphite electrodes becoming the standard design in button cells.

However, they tend to lose capacity as they age, and the researchers wanted to see the degradation process as it happens to find solutions for expanding their lifespan.

Researchers involved in a study on the process include teams from the SyncLab research group at HZB and the BLiX laboratory at the Technical University of Berlin.

"A lot happens at the interfaces between the anode, separator and cathode while a battery is charging or discharging," explained Ioanna Mantouvalou, a physicist at HZB and first author of the study.

Usually, the changes are only observed after a battery is disassembled, and only at a specific point in the process.

Through the use of XRF and XAS in a so-called confocal geometry, the report explained, researchers can look inside a battery while processes are taking place. This gives them detailed 3D scans with sample resolutions of down to 10 micrometers.

"The confocal setup allows us to distinguish the individual layers from the NMC cathode to the back contact and to study their elemental composition. This gives us spatially resolved insights into the operation without changing the layer stack; non-destructive, quantitative, under operating conditions, i.e., operando," says Mantouvalou.

Lithium-ion batteries support our transition away from planet-polluting dirty fuels toward renewable energy sources like solar and wind.

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Both electric vehicles and utility-scale energy storage use lithium-ion technology, as well as the consumer electronics industry.

Extending battery lifespans would reduce the need for raw material mining and improve functionality for consumers.

According to Battery University, manufacturers conservatively list lithium-ion battery lifespans from between 300 and 500 discharge/charge cycles. Data from 2020 indicated that smaller wearable batteries deliver around 300 cycles, while larger smartphone models have a life-cycle requirement of 800 or more.

Electric vehicles rely on lithium-ion batteries, and although they're predicted to last up to 15 years in normal climates, extreme weather conditions drop that down to as short as 8 years.

So far, the researchers have been able to observe 10,000 charge cycles over the course of several weeks by using a confocal micro X-ray fluorescence spectrometer at BLiX lab.

Results showed that during the first three weeks, manganese, in particular, began to dissolve in the NMC cathode and migrate to the carbon anode. This took just 200 cycles to appear, and it continued to dissolve further over time, which reduced the battery's efficiency.

"We urgently need such quantitative results to further improve batteries," said Mantouvalou, and their work could have a large impact on the future of the renewable energy economy.

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