Dual-Crosslinked Polyacrylamide Binders with Various Polysaccharides and Their Application to High Capacity Anodes

Over the last 20 years, much attention has been devoted to developing new electrode materials with high energy and power densities for lithium ion batteries (LIBs). However, a binder material providing an integrity in a composite electrode seems to have an attention recently due to its great influence on the long-term cyclic stability, rate capability, and irreversible capacity loss of the electrodes. High capacity anodes experiencing large volume change such as silicon is strongly dependent on proper choice of polymeric binder. Polyvinyledene difluoride (PVdF) is the most common binder in commercial LIBs. However, the Si electrode fabricated with PVdF binder showed rapid capacity fades for the first tens of cycles caused by the poor adhesion strength of PVdF on current collector. Moreover, it dissolves only in toxic and expensive organic solvent, m-methyl-2-pyrrolidone, leading to environmental issues for the electrode manufacturing process. To replace the organic solvent, environmental-friendly water soluble polymers such as, polyacrylic acid (PAA), polyvinyl alcohol (PVA), carboxymethyl cellulose, and sodium-alginate (SA) began to be applied to high capacity Si-based anodes and showed excellent binder performance, when compared to conventional PVdF binder due to their robust adhesion to active material and current collector and low electrolyte swelling to maintain the mechanical properties of binder. In spite of these endeavors, further improvement in the binder materials is still required, especially for the use high capacity anodes to have sufficiently stable cyclic performance for commercial application. In this presentation, water-treated dual-crosslinked binder systems will be introduced for a high capacity silicon/graphite electrode. A polysaccharide is first grafted with polyacrylamide (PAAm), and ionic and chemical crosslinkings are subsequently performed to complete dual-crosslinking in the grafted polymer. Three types of polysaccharides, sodium-alginate, sodium-carboxymethyl cellulose, and pectin, will be employed and compared for their performance as a binder material for high-capacity anodes. A variety of characterization tools will used to examine the electrochemical performance of the electrodes containing the dual-crosslinking binder systems.