A conventional binder for powdery composite electrodes, poly(vinylidene fluoride) (PVdF), is widely used in commercial lithium-ion electrodes because of its chemical and electrochemical stability and good affinity to the electrode and electrolyte materials. However, coverage of active material surface and adhesive strength of a composite layer onto a current collector are not enough to cope with severe conditions of electrode operation such as high potential or large volume change during a charge-discharge cycle. In addition, N-methyl-2-pyrrolidone (NMP) as solvent to dissolve PVdF binder to prepare electrode slurry is combustible and harmful. Since there has been intensive preference for alternative water-soluble polymer to PVdF binder, we study water-soluble polymers as new binders for lithium-ion cells, being convinced that binder is critical materials to maximize the intrinsic performance of active materials and to modify the negative electrode surface including SEI to suppress undesired side-reactions at graphite electrode [1]. Recently, we extend our work on binder towards cross-linked and natural polymers for negative and positive electrodes for Li, Na, and K batteries. We will present detailed results to realize high-energy electrode performance with new binders such as polyacrylates [2-4], covalently crosslinked polyacrylates [5], branched polysaccharides [6], polyglutamates [7,8], and SBR latex [9]. We will also discuss the mechanism of better performance compared to that for conventional PVdF with characterization data and surface analyses.

References:

[1] S. Komaba et al., ECS Trans, 11 (29) 63-70 (2008).

[2] S. Komaba et al., J. Power Sources, 189, 197 (2009).

[3] Z.-J. Han, S. Komaba, et al., Phys. Chem. Chem. Phys., 17, 3783 (2015)

[4] M. Fukuknishi, K. Kubota, T. Horiba, S. Komaba et al., Electrochem., 87, 70 (2019).

[5] S. Aoki, S. Komaba, et al., J. Electrohem. Soc., 162, A2245 (2015).

[6] M. Murase, S. Komaba, et al., ChemSusChem, 5, 2307 (2012).

[7] T. Mochizuki, T. Horiba, S. Komaba, et al., ACS Sustainable Chem. Eng., 5, 6343 (2017).

[8] Y. Yoda, K. Kubota, T. Horiba, S. Komaba, et al., ACS Appl. Mater. Interfaces, 10, 10986 (2018).

[9] N. Yabuuchi, S. Komaba et al., J. Electrochem. Soc., 162, A538 (2015).