The Correlation between Carbon Additives and the Binder: The Case of Poly(methyl methacrylate)-Grafted Natural Rubber Binder

Abstract

This study examines the influence of carbon additives on the performance of rubber binder-based anodes in lithium-ion batteries, with a particular focus on a binder consisting of 49% poly(methyl methacrylate)-grafted natural rubber (MG49). This research is a continuation of previous efforts to better understand how different commercial carbon additives, varying in particle size and shape, affect binder cohesion and overall anode performance. A series of physicochemical and electrochemical techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), cyclic voltammetry (CV), and dynamic electrochemical impedance spectroscopy (DEIS), were employed to assess the effects of these additives on binder cohesion and overall anode performance. Electrodes incorporating Super P exhibited a high initial specific discharge capacity of 299.8 mAh/g (G6-15), with 98.6% initial Coulombic efficiency and 77.8% capacity retention after 50 cycles. C65-based electrodes demonstrated excellent performance, with a specific discharge capacity of 342.3 mAh/g (C6-15) and the highest capacity retention of 89.5%. In contrast, KS6L-based electrodes suffered from poor electrochemical performance, showing an initial capacity of only 1.237 mAh/g (K6-8), high charge transfer resistance (R_ct of 218.5 Ω), and a drastic loss in capacity over cycling. Lithium-ion diffusion coefficients revealed superior kinetics for Super P and C65, with values of 1.087 × 10^–8 cm²/s (G6-15) and 1.645 × 10^–8 cm²/s (C6-10) in the oxidation process, while KS6L exhibited limited ion mobility (2.316 × 10^–12 cm²/s for K6-10). These findings underscore the critical role of carbon additive selection in enhancing the energy density, stability, and lifespan of lithium-ion batteries. The study provides valuable insights into optimizing binder–additive interactions to improve electrode performance in next-generation energy storage applications.