When we fabricate a variety of electrodes for lithium-ion batteries (LIBs), some electrode design parameters such as composition, loading level, density, etc. are generally predetermined depending on the targeted energy and power densities. Since they are complexly related to each other, repetitive experiments should be carried out to get reliable long-term cycle life as well as initial capacity. At this point, an optimum binder content or density always remains a difficult question, because there is no systematic research on adhesion properties for LIB electrodes. In addition, only the peel test with the 3M Scotch tape has widely used to compare electrode adhesion strength as a relatively comparing tool. Thus, our group has introduced a tool, the Surface and Interfacial Cutting and Analysis System (SAICAS), to measure shear stress as well as adhesion strength of the LIB electrodes [1-3]. Although our previous works provided battery scientists and engineers with worthwhile data, more systematic investigation to separate intrinsic adhesion property from loading is greatly required.

Herein, we applied the SAICAS tool to measure all the adhesion properties of LIB LiCoO₂ electrode having three different loading levels, 5, 10, and 15 mg cm^-2, and four different electrode densities, 2.0, 2.5, 3.0, and 3.5 g cm^-3. Not only the adhesion strength between current collector and electrode coating layer, but also the adhesion strength at the middle of the electrode coating layer are obtained and compared to divide each intrinsic adhesion strength independent of loading effect. From those data, we could propose an empirical equation to predict adhesion strength if density and loading level are provided. This equation is also confirmed in the LiCoO₂ electrode system by comparing the adhesion strength of arbitrary electrodes with different loading and density.

Acknowledgements

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).

References

[1] Son, B.; Ryou, M.-H.; Choi, J.; Lee, T.; Yu, H. K.; Kim, J. H.; Lee, Y. M., Measurement and Analysis of Adhesion Property of Lithium-Ion Battery Electrodes with SAICAS. ACS Appl. Mater. Interfaces 2013, 6, 526-531.

[2] Choi, J.; Ryou, M.-H.; Son, B.; Song, J.; Park, J.-K.; Cho, K. Y.; Lee, Y. M., Improved High Temperature Performance of Lithium-Ion Batteries through Use of a Thermally Stable Co-Polyimide-Based Cathode Binder. J. Power Soures 2014, 252, 138-143.

[3] Choi, J.; Kim, K.; Jeong, J; Cho, K. Y.; Ryou, M.-H.; Lee, Y. M., Highly Adhesive and Soluble Co-polyimide Binder: Improving the Long-Term Cycle Life of Silicon Anodes in Lithium-Ion Batteries, ACS Appl. Mater. Interfaces, 2015, 7, 14851-14858