Improving Fundamental Understanding of Si-Based Anodes Using Carboxymethyl Cellulose (CMC) and Styrene-Butadiene Rubber (SBR) Binder for High Energy Lithium Ion Battery Applications

With increasing demand of high energy density lithium ion batteries, silicon (Si) based anodes are an obvious substitute of graphite based systems due to their high capacity. However, large volume changes of Si during lithiation and delithiation processes causes pulverization of silicon particles. The resulting reduction in electrical continuity and solid electrolyte interphase (SEI) growth within the anode leads to a fast depletion of lithium reservoirs and an accelerates battery failure. High energy lithium ion battery applications such as electrical vehicles and electronic devices require high capacity retention over extended cycling, so improving performance of Si-based anodes is a critical need for many applications. Commonly, a combination of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) is used as a binder for waterborne Si anode slurries. In these systems, carboxyl (-COOH) groups on CMC form chemical bonding with hydroxyl (-OH) groups on Si active material surface and SBR addition provides enhanced flexibility in the anode layer. Several reports on electrode integrity improvement through adhesion promoters, increased crosslinking, different binding groups, etc. are available in the literature. Delving deeper into the weak mechanical integrity of Si based anodes, and understanding the parameters influencing the fabrication process and subsequent properties, is important. This presentation will focus on several variations in Si based anode slurries and electrodes using CMC-SBR binders. Physical, mechanical, and electrochemical properties are extensively studied as a function of these parameters and will be discussed.