Effect of binder properties on electrochemical performance for silicon-graphite anode: Method and application of binder screening

• Binder properties are systematically characterized to estimate their suitability.
• Interpretation of binder properties in connection with binding affinity, electrode properties, and degree of phase separation in slurry.
• According to the screening results, hybridization of poly(acrylic acid) and poly(amide imide) is recommended.
• The modified binder showed improved cycle performance based on enhanced binder properties.

With increasing demand for lithium-ion batteries (LIBs) with high energy density, silicon-based negative electrode material has attracted much interest because of its high specific capacity. Practical utilization of Si remains unattainable, however, owing to severe volume expansion in the electrode, resulting in a loss of the electrical Si network, which is directly connected to drastic capacity fading of the cell. Therefore, there have been systematic studies on the characterization of fundamental binder properties to estimate the suitability of various binder materials. The binder properties are subdivided into mechanical and adhesion characteristics, electrode properties (rigidity and recovery), and phase separation behavior of slurry to correlate with the electrochemical performance and practical acceptance of candidate materials. Systematic screening showed that hybridization of poly(acrylic acid) (PAA) and poly(amide imide) (PAI) could complement each other's properties and the hybridized PAA–PAI was synthesized by a one-step, acid-catalyzed reaction. The PAA–PAI hybrid showed enhancement in overall properties as a result of co-polymerization and exhibited remarkable cycling performance after 300 cycles. Based on these results, it can be concluded that an understanding of binder characteristics provides useful insight into the search for a more efficient binder material, and fine tuning of fundamental binder properties through screening will be advantageous to the construction of more efficient LIB systems