Silicon Anodes for Lithium‐Ion Batteries Based on a New Polyimide Binder

Silicon is a promising candidate for replacing graphite in anodes for advanced Li‐ion batteries due to its high theoretical gravimetric energy density. However, silicon as an active anode material suffers from significant volume changes upon lithiation/delithiation, causing fast capacity fading. The performance of silicon anodes depends on the polymeric binders used, which form well‐bound Si particles matrices that accommodate the strains developed during their repeated lithiation, thus maintaining their integrity. Herein, we investigated the effect of thermal treatment on the performance of polyimide P84 as a novel binder for composite Si anodes comprising metallurgical micron‐size silicon particles (80% silicon). The electrochemical behavior of metallurgical silicon‐based anodes heat‐treated to 120°C, 200°C, 300°C, and 400°C was examined in half (vs. Li electrodes) and full (vs. NCM622 cathodes) cells. An optimal performance was obtained after heat treatment at 400°C, related to the very good adhesion of the electrode’s active mass to the current collector, and the ability of the heat‐treated binder to enhance the active mass integrity upon cycling. A comparison between optimized anodes developed herein to other Si anodes containing frequently used binders like Sodium Alginate (SA) and Lithium Polyacrylate (LiPAA), demonstrated clear advantages of the heat‐treated Si anodes containing P84.