Polyamic Acid Binder for Silicon Anode Battery Stability

The invention changes the chemical composition parameters of the binder by incorporating specific functional groups (carboxyl groups with 0.1-10 mmol/g and hydroxyl groups with 0.1-10 mmol/g) into the polyimide structure. This modification allows the binder to achieve both mechanical strength for cycle stability and improved ionic conductivity for charge-discharge efficiency through chemical interactions with lithium ions.

The invention creates a composite binder system by combining polyimide base resin with functional additives containing carboxyl and hydroxyl groups. This composite structure integrates the mechanical strength of polyimide with the electrochemical activity of the functional groups, enabling simultaneous improvement of cycle characteristics and charge-discharge efficiency.

The invention applies beforehand cushioning by incorporating functional groups (carboxyl and hydroxyl) into the binder structure that can chemically interact with silicon-based material before expansion occurs. These groups form protective complexes with silicon particles, cushioning the mechanical stress during expansion and contraction cycles and preventing active material layer damage.

The functional groups (carboxyl and hydroxyl) in the binder act as intermediaries between the silicon-based active material and the polyimide matrix. These intermediary groups facilitate stress distribution and maintain adhesion during volume changes, preventing direct mechanical damage to the active material layer while allowing high silicon content for energy density.