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Lithium-ion batteries are used in a wide range of applications ranging from mobile devices and computers to automotives. There is a constant demand for improved performance and safety of Li-ion batteries in order to make the technology more widely used.
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In order to improve the design and performance of the Li-ion batteries, it is important to understand the microstructure of the material. In this case particular to understand where the Li is located and how the structure might change during the lifetime of the battery.
Many of the materials used in the Li-ion batteries have successfully been analysed using EDS or EBSD and the presence of Li either shown by detecting Li K X-rays or by measuring the change the crystal structure indicating the presence of Li.
Li has been detected in the material used for graphite anodes and many new materials used as electrolytes. For the cathode materials, the ionic state of the Li ions means that so far no x-rays have been detected from Lithium.
Light element detection
Lithium x-rays have been detected using Extreme EDS from many of the compounds containing Li (1).
Examples covering a wide range of materials from LiH, LiF, Li3N, Li2S and LiCl.
The Ultim Extreme is an EDS detector optimized to deliver the ultimate performance in low energy EDS. Combined with a windowless design for maximum low energy sensitivity, this detector provides Extreme capabilities for light element detection.
Solid state electrolyte
Solid state electrolytes are being used to improve the safety and performance of the Li-ion batteries. These electrolytes typically contain several chemically different phases and being able to identify the phases is vital in order to improve the designs.
In this example, the chemical analysis of the phases in the garnet has been done using EDS to identify the phases.
LiNiO Cathode Material
You can’t detect Li with the Extreme due to the ionic state of the Li in this material. However, you do get a very good signal from the other light elements.
In this map, you are able to detect the Fluorine shell on the LiNiO grains. This is residual material from the processing of the cathode and understanding these layers gives you a valuable understanding of the battery performance.
References:
Lithium Ion batteries are found in most mobile electronic devices (e.g. laptop computers, phones etc). They are the dominant battery technology due to their superior energy to weight ratio and lack of memory effect. They are also the primary battery type used in the latest generation of electric and hybrid cars.
New and existing materials for lithium ion batteries are being studied extensively with the aim of increasing their storage capacity and lifetime. While the SEM is an important tool in the study of these materials, characterising the distribution of Li still remains one of the main challenges.
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