The rapid development of the new energy industry in recent years has emphasized the critical role of lithium batteries as reusable and rechargeable batteries in many industrial applications.
During the production of lithium batteries, an electrode slurry is created using NMP (n-methylpyrrolidone) as a dispersant. NMP is a solvent for PVDF in the slurry batching stage, helping a more uniform system to be produced by the slurry dispersion.
In the coating stage, NMP also serves as the main carrier of the slurry, and it provides an even coating on the substrate. During the coating and baking stages, NMP becomes volatile, producing pores in the coating. This gives rise to a uniformly distributed porous microelectrode structure.
The stability of battery electrode materials in NMP is critical because it directly impacts the electrode production quality. This article analyzes the zeta potential of various slurries dispersed in NMP.
Instrumentation
Bettersize Instruments’ BeNano 90 Zeta nanoparticle size and zeta potential analyzer were employed for this study. This instrument uses a laser with a wavelength of 671 nm and a power output of 50 mW as its light source.
An APD detector was placed at an angle of 12 degrees to collect the scattered light signal. The phase analysis light scattering (PALS) method was utilized to accurately detect the zeta potential information of samples with low electrophoretic mobility.
Experimental
A total of four battery electrode materials were dispersed in NMP solvent. The dip cell was utilized because of the low dielectric constant of the organic phase NMP. Each sample was measured six times to determine the mean and standard deviation.
Results
Figure 1. Phase plots of multiple measurements for sample #1. Image Credit: Bettersize Instruments Ltd
Figure 2. Zeta potential distributions of multiple measurements for sample #1. Image Credit: Bettersize Instruments Ltd
Figure 3. Phase plots of multiple measurements for sample #2. Image Credit: Bettersize Instruments Ltd
Figure 4. Zeta potential distributions of multiple measurements for sample #2. Image Credit: Bettersize Instruments Ltd
Figure 5. Phase plots of multiple measurements for sample #3. Image Credit: Bettersize Instruments Ltd
Figure 6. Zeta potential distributions of multiple measurements for sample #3. Image Credit: Bettersize Instruments Ltd
Figure 7. Phase plots of multiple measurements for sample #4. Image Credit: Bettersize Instruments Ltd
Figure 8. Zeta potential distributions of multiple measurements for sample #4. Image Credit: Bettersize Instruments Ltd
Table 1. Source: Bettersize Instruments Ltd
| Samples |
Zeta potential (mV) |
Standard deviation (mV) |
| 1# |
-53.43 |
3.48 |
| 2# |
-51.84 |
1.97 |
| 3# |
-50.32 |
2.46 |
| 4# |
-48.53 |
3.44 |
The phase plots and distribution curves of the samples displayed in Figures 1 – 8, along with the data presented in Table 1, show that the zeta potentials of all samples are negative. This is indicative of the electrode materials carrying negative charges in the NMP.
The zeta potential amplitudes of all four samples are approximately 50 mV, with the higher zeta potential representing the high stability of the samples. The standard deviations of several measurements were small, suggesting good reproducibility.
Conclusions
This study employed the BeNano 90 Zeta nanoparticle size and zeta potential analyzer to measure the zeta potentials of four different samples of battery electrode materials dispersed in NMP.
The results demonstrated that all samples had negative zeta potentials, indicating negative charges in the electrode materials. The zeta potential amplitudes were approximately 50 mV, which indicates high stability.
This experiment emphasizes the importance of understanding zeta potential to enable the optimization of battery electrode production as well as the reliability of the measurements.
Acknowledgments
Produced from materials originally authored by Zhibin Guo and Hui Ning from the Application Research Lab at Bettersize Instruments Ltd.
This information has been sourced, reviewed and adapted from materials provided by Bettersize Instruments Ltd.
For more information on this source, please visit Bettersize Instruments Ltd.