Optimization of binary binder blends for aqueous-based slurries of SiOx/C for next-generation lithium-ion batteries

The growing demand for sustainable energy solutions has highlighted the crucial role of lithium-ion batteries (LIBs) in the global energy transition. However, the conventional use of polyvinylidene fluoride (PVDF) binders combined with toxic solvents like N-methyl-2-pyrrolidone (NMP), in the LIBs manufacturing process, poses environmental and cost concerns. In this study, three different water-soluble polysaccharides, sodium alginate, tragacanth gum, and carrageenan, are investigated as suitable binders for silicon/graphite composite anodes. The three single polysaccharide binders are initially screened through rheological and electrochemical analyses to ensure compatibility with slurry processing, electrode and cell manufacturing. From the pre-screening, sodium alginate emerges as the most promising candidate, demonstrating favourable rheological properties and electrochemical stability. To further improve electrode mechanical properties and long-term electrochemical performances, sodium alginate is mixed with lithiated polyacrylic acid in binary mixtures with a total binder content of 3 wt%. The optimal formulation, 2LiPAA:1ALG, exhibits enhanced cycling stability and higher specific capacity retention compared to single-binder systems. Statistical analysis confirms the significant influence of binder mixture composition, highlighting the complementary mechanical and electrochemical roles of ALG and LiPAA. In comparison with previously reported crosslinked or grafted binder systems that require chemical modification, this approach uses a simple physical mixing strategy, improving the electrochemical behaviour, preserving processability. Overall, the results demonstrate that rationally designed combinations of natural and synthetic water-soluble binders offer a viable strategy to balance mechanical integrity, sustainability, and electrochemical performance, providing valuable insights for the development of next-generation LIB anodes.