Layer Stacked Polyimide with Great Built-in Electronic Field for Fast Lithium-ion storage based on Strong π-π Stacking Effect

Polyimide has been regarded as potential organic cathode for lithium-ion batteries (LIBs) due to its excellent solvent resistance, thermodynamic stability and flexibly programmable polymer structure. However, the poor conductivity, easy entanglement and agglomeration of PI chains lead to slow ion diffusion, poor electron transfer, and insufficient reaction, which make it difficult to effectively exert its theoretical capacity at high current density. Herein, a layer stacked polyimide cathode (NT-U) based on π-π stacking effect was successfully obtained. NT-U possesses a large molecular dipole moment that induced by the strong electronegative groups in PI and further enhanced by the π-π stacking structure, which contributes to the formation of a robust built-in electric field (BIEF). The strong BIEF in this highly crystalline PI plays a critical role in accelerating the charge transport dynamics and improving electrochemical performances of LIBs, as verified by in-situ XRD, ex-situ FTIR, ex-situ XPS, and ex-suit SEM, DFT calculations. These findings provide new insights into the construction of PIs cathode based on the mechanism of dipole and BIEF for fast and efficient energy storage.