Understanding Key NaCMC Properties to Optimize Electrodes and Battery Performance

Abstract

This study examines the effects of sodium carboxymethyl cellulose (NaCMC) on the performance of graphite anodes in lithium-ion batteries, focusing on variations in degrees of substitution (DS), molecular weights (MW), and gel particles. The results indicate that the best electrochemical performance is achieved by balancing the residual water content introduced by NaCMC while maintaining the anode's volume resistivity. A NaCMC with a low molecular weight and DS of 0.7 shows the best results for this particular formulation. An impurity (in batteries yet unreported)in NaCMC is also reported that significantly impacts electrochemical performance, called gel particles. By reducing the gel particles, cell performance is enhanced by 5%, without further optimization of the formulation. It is highlighted that both DS and MW influence electrode properties. A decrease in DS enhances adhesion but negatively affects volume resistivity. Increasing the MW improves adhesive strength and reduces interfacial resistivity due to greater chain entanglements. Higher gel particle levels negatively impact electrode properties, making low-gel NaCMC more effective for better adhesion and resistance. Water retention in electrodes again is influenced by both DS and MW. Higher DS leads to increased water retention due to greater hydrophilicity, while high MW contributes to this effect through enhanced entanglements.