Structure Tailoring Enabled Self-Catalyzed Imidization for Engineering a Highly Adhesive and Ion-Conductive Polyimide...

Silicon (Si) is widely recognized as one of the most promising anode materials for next-generation lithium-ion batteries (LIBs). Nevertheless, its practical application is hindered by significant volume expansion and poor interfacial stability. Herein, a highly adhesive and ion-conductive polyimide binder, denoted as PIy, is synthesized via low-temperature self-catalyzed imidization through the copolymerization of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) with 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) as the tough monomer, 4,4'-diamino-2,2'-bipyridyl (DAPY) as a base-catalyzing component, and 2-(5-amino-2-methylanilino)-4-(3-pyridyl)pyrimidine (AMPY) as an end-capping agent. DAPY and AMPY effectively lower the activation energy of poly(amic acid) imidization which enables cyclization to proceed at low temperatures and the pyridine groups promote Li⁺ transport. BPDA and BAPP contain abundant aromatic rings that provide high toughness and impart a high modulus to suppress volume changes. Meanwhile, the flexible -O- segments enhance chain mobility adapting to expansion while maintaining structural integrity. The Si@PIy-185 °C electrode exhibits excellent long-term cycling stability, maintaining a high specific capacity of 1118.6 mAh g^{- 1} at 1 A g^{- 1} even after 1000 cycles.The full cell of the SiO_x@PIy-185 °C//NCM811 exhibits a remarkable capacity retention of 87.8% after 100 cycles, highlighting the potential of the low-temperature imidized PI binder for high-energy-density LIBs.