Battery Research with an SEM: Inspecting One Layer at a Time

The electronics world was revolutionized by the creation of batteries. They have enabled us to carry an energy reserve around easily. Efficiency and Miniaturization are the two key words when discussing new advances in this field, impacting with the battery materials’ properties and pushing their limits. Researchers characterize materials and collect appropriate data about batteries by utilizing scanning electron microscopy (SEM).

The structure of a battery consists of three main parts:

  • Two electrodes made of different materials
  • An insulation membrane between the electrodes

Energy is discharged because the different chemical composition of the two electrodes means they are available for chemical interaction and during the reduction-oxidation processes that is what subsequently happens. The chemical energy stored in the electrodes is therefore transformed into electrical energy and can then be used to power up electronic devices.

Some enhancements were made to upgrade from the original battery concept (which was the size of a table-top) to the small and long-lasting smartwatch battery. These changes mostly affected the materials used for the production of the battery, rather than the working principle, which stayed the same in concept.

Engineering Batteries: What Matters?

When a new battery structure is designed, the specification of the object that it will be powering is key to acquire a strong match in terms of capacity and size. Some parameters that are commonly found in the battery research and development process are:

Energy Density

This determines the amount of energy per volume unit that can be amassed. This is increased by engineering the configuration of the electrodes and also the shape of them. This optimizes the use of space concerning the available reaction surface. Additionally, the size of the component has been massively decreased.

Self-Discharge Rate

Batteries cannot keep their charge forever and from time to time it’s lost completely. This is okay for some applications, but it can become annoying when it happens to a remote-control battery for example, which requires little quantities of energy with lengthy breaks in between. Usually temperature plays a big part role in this context which is why your phone battery dies faster in the cold!

Safety

Making components smaller raises a key safety issue: the correct insulation of the electrodes. It is no secret that batteries can explode (it has been in the news how some smartphone manufacturers have had problems with this). This can be because, when the insulating membranes that separate, the electrodes break due to a mechanical tension (the battery is bent too much).

Nominal Voltage

This is a guide of what voltage the battery can provide. For example, a watch and a car use different amounts of energy and these values are obtained using different sorts of electrodes.

Improving Battery Quality with SEM

All of these parameters, as discussed, rely heavily on the material composition and structure. These parameters can be monitored easily, but suitable analysis instrumentation is needed.

left and right: SEM images of raw powders used in the production of cathodes. SEMs are ideal tools for inspecting small particles in the range of micrometers or nanometers.

Figure 1. left and right: SEM images of raw powders used in the production of cathodes. SEMs are ideal tools for inspecting small particles in the range of micrometers or nanometers.

SEM gives you the chance to improve battery research by permitting you to magnify your sample hundreds of thousands of times. This means that features of a few nanometers are clearly visible. Using this it is viable to calculate the cross section of layers, and also the size of the small features on the electrode’s surface that upgrade the contact surface.

Additionally, it is possible to apply both mechanical and thermal stress to a membrane and observe its behavior to a microscopic degree, which enables battery researchers to understand the reason for an eventual rupture.

SEM is commonly combined with Energy-dispersive X-ray microanalysis to locally define the chemical composition of the sample accurately and with an outstanding, sub-micron, spatial resolution. The analysis only takes few seconds!

An example of how EDS can be used to trace how the sample composition changes along a line. Spot analysis, line scan or area map can be used to monitor the distribution of different phases in a specific region of the sample.

Figure 2. An example of how EDS can be used to trace how the sample composition changes along a line. Spot analysis, line scan or area map can be used to monitor the distribution of different phases in a specific region of the sample.

This information has been sourced, reviewed and adapted from materials provided by Phenom-World BV.

For more information on this source, please visit Phenom-World BV.

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