Among others, the performance of lithium-ion batteries(LIBs) is determined by the structure and material distribution of the electrodes. These electrodes are known to develop an inhomogeneous inactive material distribution during the drying process of the wet slurry film.
Today, I'm going to review two relevant papers about the phenomenon called segregation, which occurs during the drying process, and their impacts on the microstructure of the electrode. There are various ways to characterize electrodes' properties, and the following works are utilizing the adhesion strength between the electrode and current collector, which is an indirect way to assess the distribution of inactive components throughout the electrode.
A common interest in the following two papers is finding out the impacts of the drying temperature and wet film properties on the macroscopic properties of the electrodes, e.g., adhesion strength.
Let's get it started!
Bastian G. Westphal et al., Journal of Energy Storage 18 (2018)
Summary
- The degree of segregation depends on both electrode mass loading and drying temperature.
- The higher the mass loading and the harsher the drying condition leads to the higher degree of segregation of the inactive materials.
- The auxiliary parameter, the amount of heat for warming, was used to determine a critical amount of heat for warming below which segregation can be avoided.
Useful backgrounds
- What does segregation mean?
- What does TTF stand for?
- Why did they introduce an auxiliary parameter: the amount of heat for warming?
Stefan Jaiser et al., DRYING TECHNOLOGY 35 (2017)
Summary
- In the preceding work[Jaiser et al., Journal of Power Sources 318 (2016)], the authors found characteristic solvent volume fraction to coincide with the end of film shrinkage.
- To verify the preceding hypothesis, they set six different experimental scenarios by varying the drying conditions and wet film properties.
- They found that the majority of the scenarios, the hypothesis proves true except for two scenarios.
- To determine the end of the film shrinkage indirectly, a characteristic saturation was defined relating the characteristic solvent volume fraction and the dry film porosity.
Useful backgrounds
- What is the characteristic solvent volume fraction?
- What does HDR stand for?
- Why is the thicker film harmful to adhesion strength?