N -Heteroaromatic Hydrocarbon π-Conjugated Porous Polymers for High-Rate-Performance Sodium-Ion Batteries

As one type of promising material, porous organic polymers (POPs) have been widely used in sodium-ion battery (SIB) electrodes on account of their environmental friendliness and adjustable pore diameter. However, their capacity and rate performance require further improvement. Herein, a conjugated porous polymer (PQ–POP), containing an azaacene-deficient electron-deficient system, was synthesized by a simple condensation reaction. The conjugated and N-containing heteroaromatic structure improves the conductivity, charge-transfer efficiency, and physicochemical stability. Also, the porous polymeric framework shows a large specific surface area and high porosity, providing a large contact area with electrolytes and reducing the diffusion distance. Therefore, PQ–POP exhibits very good electrochemical properties. Besides its superior reversible specific capacity of 245 mAh g –1, PQ–POP also shows remarkable cycling stability, maintaining almost 100% after 1000 cycles at 4 A g –1 . At 10 A g –1, its capacity holds steady at 202 mAh g –1, outperforming many similar materials. The sodium ion storage mechanism of PQ–POP was confirmed by in situ FTIR and XPS experiments. In order to broaden the application of PQ–POP in SIBs, the electrochemical performance of PQ–POP as the negative electrode and Na 3 V 2 (PO 4 ) 3 as the positive electrode were employed to assemble a full cell, where, even at 3 A g –1, the full cell based on PQ–POP//Na 3 V 2 (PO 4 ) 3 maintained 101 mAh g –1 of the capacity with nearly 100% coulomb efficiency, highlighting its potential in energy storage applications and providing perspectives into designing advanced POP electrodes for SIBs.