A flexible network polyimides binder for Si/graphite composite electrode inlithium‐ionbatteries

Although the high-capacity Si/graphite anode serves to advance the energy density of lithium-ion batteries, the volume change remains the main disfigurement of Si/graphite anode. Many studies show that crosslinked structure binders tend to play a good inhibitory effect on volume expansion. In this work, a three-dimensionally covalently cross-linked and flexible polyimides (C–PI–OH) is successfully synthesized and applied as silicon/graphite anode, which is composed through a tri-monomer co-polycondensation and crosslinking process. The as-formed free carboxylic acid groups and amide groups in C–PI–OH are efficient in structural stability, so the electrode bound by C–PI–OH exhibits the highest peeling strength than C–PI and polyvinylidene fluoride. The flexible network of the C–PI–OH binder is competent for accommodating the volume expansion and contraction of silicon particles during the deintercalation of lithium ion, which helps in the wholeness of solid electrolyte interface film and electrodes, and effectively boosting the cycle stability of the Si/graphite anode.